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Rhipicephalus (Boophilus) microplus is globally one of the most economically important ectoparasites of cattle costing the agriculture industry billions of dollars annually. Resistance to chemical control measures has prompted the development of novel methods of control. Recent advancements in genetic control measures for human and other animal vectors have utilized sex determination research to manipulate sex ratios, which have shown promising results in mosquitoes namely Aedes aegypti and Anopheles stephensi. Here, we use R. (B.) microplus as a model to provide foundational research to allow similar avenues of investigation in ticks using R. (B.) microplus as a model. Karyotypes for R. (B.) microplus show an XX:XO sex determining system with the largest chromosome being the sex chromosome. Using flow cytometric methods, the size of the sex chromosome was estimated at 526.91 Mb. All measures to identify the sex chromosome within the cattle tick genome assembly associated sex chromosomal characteristics to two chromosomes. This discrepancy between the assembly and karyotypes of the tick led to generating a new genome assembly with a single adult male specimen. The two chromosomes in question aligned with a single scaffold within the new genome that had a length of 513.29 Mb and was the first time the sex chromosome was identified in an Ixodid genome assembly., (Published by Oxford University Press on behalf of The Genetics Society of America 2024.)

Background: Bovine babesiosis is caused by infection with the protozoal parasite Babesia bovis, which is transmitted by Rhipicephalus (Boophilus) spp. It can cause mortality rates up to 90% in immunologically naive Bos taurus cattle. In south Texas, R. (B.) microplus is known to infest nilgai antelope (Boselaphus tragocamelus); however, their susceptibility to infection with B. bovis and their role in the transmission of the parasite remain unknown. In this study, we challenged nilgai antelope with B. bovis and evaluated their susceptibility to infection., Methods: Nilgai were needle inoculated with ≈10 8 B. bovis-parasitized erythrocytes (merozoites) or a homogenate of B. bovis-infected larval ticks (sporozoite) delivered intravenously. Bos taurus beef calves were inoculated in parallel, as this strain of B. bovis is lethal to cattle. Temperature and hematocrit were monitored daily over the course of each study, and whole blood was collected for molecular [polymerase chain reaction (PCR)] and serological [indirect enzyme-linked immunosorbent assay (ELISA)] diagnostic evaluation. Histological sections of nilgai cerebral tissue were examined for evidence of infection. Recipient bovine calves were sub-inoculated with blood from nilgai challenged with either stage of the parasite, and they were monitored for clinical signs of infection and evaluated by a PCR diagnostic assay. Red blood cells (RBCs) from prechallenged nilgai and B. taurus beef cattle were cultured with an in vitro B. bovis merozoite culture to examine colonization of the RBCs by the parasite., Results: Nilgai did not display clinical signs of infection upon inoculation with either the merozoite or sporozoite stage of B. bovis. All nilgai were PCR-negative for the parasite, and they did not develop antibodies to B. bovis. No evidence of infection was detected in histological sections of nilgai tissues, and in vitro culture analysis indicated that the nilgai RBCs were not colonized by B. bovis merozoites. Cattle subinoculated with blood from challenged nilgai did not display clinical signs of infection, and they were PCR-negative up to 45 days after transfer., Conclusions: Nilgai do not appear to be susceptible to infection with a strain of B. bovis that is lethal to cattle. Tick control on these alternative hosts remains a critical priority, especially given their potential to disseminate ticks over long distances., (© 2024. The Author(s).)

The sand fly, Phlebotomus papatasi (Scopoli, 1786), is a major vector for Leishmania major in the Middle East, which has impacted human health and US military operations in the area, demonstrating the need to develop effective sand fly control and repellent options. Here, we report the results of spatial repellency and avoidance experiments in a static air olfactometer using the female P. papatasi testing essential oils of Lippia graveolens (Mexican oregano), Pimenta dioica (allspice), Amyris balsamifera (amyris), Nepeta cataria (catnip), Mentha piperita (peppermint), and Melaleuca alternifolia (tea tree); the 9-12 carbon saturated fatty acids (nonanoic acid, decanoic acid, undecanoic acid, and dodecanoic acid); and the synthetic repellents DEET and IR3535. The materials applied at 1% exhibited varying activity levels but were not significantly different in mean repellency and avoidance from DEET and IR3535, except in regards to nonanoic acid. Some materials, particularly nonanoic and undecanoic acids, produced sand fly mortality. The observed trends in mean repellency over exposure time included the following: (1) P. dioica oil, M. alternifolia oil, decanoic acid, undecanoic acid, DEET, and IR3535 exhibited increasing mean repellency over time; (2) oils of N. cataria , A. balsamifera , M. piperita , and dodecanoic acid exhibited relatively constant mean repellency over time; and (3) L. graveolens oil and nonanoic acid exhibited a general decrease in mean repellent activity over time. These studies identified the essential oils of N. cataria and A. balsamifera as effective spatial repellents at reduced concentrations compared to those of DEET. Additional research is required to elucidate the modes of action and potential synergism of repellents and essential oil components for enhanced repellency activity.

Screwworm flies are mass-reared and released along the Panama-Colombia border to prevent reinfestation of Central and North America. The cost of the production facility, labor, and diet materials makes mass-rearing the most expensive component of the program. The mass-rearing diet has a large impact on the quality and quantity of insects produced, both of which are necessary for the successful implementation of the sterile insect technique. The diet currently used to rear screwworm flies in Panama contains dried bovine red blood cells, dried bovine plasma, egg powder, milk replacement powder, cellulose (thickening agent), formaldehyde (antimicrobial), and water. Here, we tested an alternative diet containing 2 chicken by-products, which cost less and are locally available, to replace the egg powder and milk replacement powder currently used in the diet. We used 2 screwworm colony strains in our test, the current production strain (Jamaica) and an early female-lethal strain. The chicken diet performed similarly to the production diet with the Jamaica strain, while further optimization will likely be needed for transgenic strain. Finally, nutritional analysis conducted on 7 diet ingredients will assist with diet optimization and the identification of alternative diet ingredients., (Published by Oxford University Press on behalf of Entomological Society of America 2023.)

Haematobia irritans irritans (Linnaeus, 1758: Diptera: Muscidae), the horn fly, is an external parasite of penned and pastured livestock that causes a major economic impact on cattle production worldwide. Pesticides such as synthetic pyrethroids and organophosphates are routinely used to control horn flies; however, resistance to these chemicals has become a concern in several countries. To further elucidate the molecular mechanisms of resistance in horn fly populations, we sequenced the transcriptomes of ten populations of horn flies from the southern US possessing varying degrees of pesticide resistance levels to pyrethroids, organophosphates, and endosulfans. We employed an Illumina paired end HiSeq approach, followed by de novo assembly of the transcriptomes using CLC Genomics Workbench 8.0.1 De Novo Assembler using multiple kmers, and annotation using Blast2GO PRO version 5.2.5. The Gene Ontology biological process term Response to Insecticide was found in all the populations, but at an increased frequency in the populations with higher levels of insecticide resistance. The raw sequence reads are archived in the Sequence Read Archive (SRA) and assembled population transcriptomes in the Transcriptome Shotgun Assembly (TSA) at the National Center for Biotechnology Information (NCBI)., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

A cDNA encoding a novel cholinesterase (ChE, EC 3.1.1.8) from the larvae of Amblyomma americanum (Linnaeus) was identified, sequenced, and expressed in Sf21 insect cell culture using the baculoviral expression vector pBlueBac4.5/V5-His. The open reading frame (1746 nucleotides) of the cDNA encoded 581 amino acids beginning with the initiation codon. Identical cDNA sequences were amplified from the total RNA of adult tick synganglion and salivary gland, strongly suggesting expression in both tick synganglion and saliva. The recombinant enzyme (rAaChE1) was highly sensitive to eserine and BW284c51, relatively insensitive to tetraisopropyl pyrophosphoramide (iso-OMPA) and ethopropazine, and hydrolyzed butyrylthiocholine (BuTCh) 5.7 times as fast as acetylthiocholine (ATCh) at 120 µM, with calculated K M values for acetylthiocholine (ATCh) and butyrylthiocholine of 6.39 µM and 14.18 µM, respectively. The recombinant enzyme was highly sensitive to inhibition by malaoxon, paraoxon, and coroxon in either substrate. Western blots using polyclonal rabbit antibody produced by immunization with a peptide specific for rAaChE1 exhibited reactivity in salivary and synganglial extract blots, indicating the presence of AaChE1 antigenic protein. Total cholinesterase activities of synganglial or salivary gland extracts from adult ticks exhibited biochemical properties very different from the expressed rAaACh1 enzyme, evidencing the substantial presence of additional cholinesterase activities in tick synganglion and saliva. The biological function of AaChE1 remains to be elucidated, but its presence in tick saliva is suggestive of functions in hydrolysis of cholinergic substrates present in the large blood mean and potential involvement in the modulation of host immune responses to tick feeding and introduced pathogens.

The New World screwworm, Cochliomyia hominivorax, causes myiasis in livestock, humans, and other warm-blooded animals in much of South America and the Caribbean. It has been eradicated from North and Central America using the sterile insect technique and a biological barrier is currently maintained at the Panama - Colombian border. However, C. hominivorax is still a threat to eradicated areas as outbreaks can and do occur. In order to identify the origin of a fly involved in an outbreak scenario, diagnostic tools would be beneficial. Recently, the geographic population structure of this species was identified using single nucleotide polymorphisms (SNPs). Here we characterize the three major regional clusters: South America, the Inner Caribbean, and the Outer Caribbean. The objective of this study was to develop a SNP (single nucleotide polymorphism) panel to distinguish between these three clusters. A panel was developed using two unique SNPs per region for a total of six SNPs. This diagnostic SNP assay will allow for rapid source determination of flies from future incursions in order to intercept introductory pathways and aid in the control of New World screwworm., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier B.V.)

The mitochondrial genome (mitogenome) has proven to be important for the taxonomy, systematics, and population genetics of ticks. However, current methods to generate mitogenomes can be cost-prohibitive at scale. To address this issue, we developed a cost-effective approach to amplify and sequence the whole mitogenome of individual tick specimens. Using two different primer sites, this approach generated two full-length mitogenome amplicons that were sequenced using the Oxford Nanopore Technologies' Mk1B sequencer. We used this approach to generate 85 individual tick mitogenomes from samples comprised of the three tick families, 11 genera, and 57 species. Twenty-six of these species did not have a complete mitogenome available on GenBank prior to this work. We benchmarked the accuracy of this approach using a subset of samples that had been previously sequenced by low-coverage Illumina genome skimming. We found our assemblies were comparable or exceeded the Illumina method, achieving a median sequence concordance of 99.98%. We further analyzed our mitogenome dataset in a mitophylogenomic analysis in the context of all three tick families. We were able to sequence 72 samples in one run and achieved a cost/sample of ~ $10 USD. This cost-effective strategy is applicable for sample identification, taxonomy, systematics, and population genetics for not only ticks but likely other metazoans; thus, making mitogenome sequencing equitable for the wider scientific community., (© 2022. The Author(s).)

Background: The cattle fever tick, Rhipicephalus (Boophilus) microplus, is a vector of pathogens causative of babesiosis and anaplasmosis, both highly lethal bovine diseases that affect cattle worldwide. In Ecdysozoa, neuropeptides and their G-protein-coupled receptors play a critical integrative role in the regulation of all physiological processes. However, the physiological activity of many neuropeptides is still unknown in ticks. Periviscerokinins (CAP 2b /PVKs) are neuropeptides associated with myotropic and diuretic activities in insects. These peptides have been identified only in a few tick species, such as Ixodes ricinus, Ixodes scapularis and R. microplus, and their cognate receptor only characterized for the last two., Methods: Expression of the periviscerokinin receptor (Rhimi-CAP 2b R) was investigated throughout the developmental stages of R. microplus and silenced by RNA interference (RNAi) in the females. In a first experiment, three double-stranded (ds) RNAs, named ds680-805, ds956-1109 and ds1102-1200, respectively, were tested in vivo. All three caused phenotypic effects, but only the last one was chosen for subsequent experiments. Resulting RNAi phenotypic variables were compared to those of negative controls, both non-injected and dsRNA beta-lactamase-injected ticks, and to positive controls injected with beta-actin dsRNA. Rhimi-CAP 2b R silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues., Results: Rhimi-CAP 2b R transcript expression was detected throughout all developmental stages. Rhimi-CAP 2b R silencing was associated with increased female mortality, decreased weight of surviving females and of egg masses, a delayed egg incubation period and decreased egg hatching (P < 0.05)., Conclusions: CAP 2b /PVKs appear to be associated with the regulation of female feeding, reproduction and survival. Since the Rhimi-CAP 2b R loss of function was detrimental to females, the discovery of antagonistic molecules of the CAP 2b /PVK signaling system should cause similar effects. Our results point to this signaling system as a promising target for tick control., (© 2022. The Author(s).)

Background: Rhipicephalus microplus is the vector of deadly cattle pathogens, especially Babesia spp., for which a recombinant vaccine is not available. Therefore, disease control depends on tick vector control. However, R. microplus populations worldwide have developed resistance to available acaricides, prompting the search for novel acaricide targets. G protein-coupled receptors (GPCRs) are involved in the regulation of many physiological processes and have been suggested as druggable targets for the control of arthropod vectors. Arthropod-specific signaling systems of small neuropeptides are being investigated for this purpose. The pyrokinin receptor (PKR) is a GPCR previously characterized in ticks. Myotropic activity of pyrokinins in feeding-related tissues of Rhipicephalus sanguineus and Ixodes scapularis was recently reported., Methods: The R. microplus pyrokinin receptor (Rhimi-PKR) was silenced through RNA interference (RNAi) in female ticks. To optimize RNAi, a dual-luciferase assay was applied to determine the silencing efficiency of two Rhimi-PKR double-stranded RNAs (dsRNA) prior to injecting dsRNA in ticks to be placed on cattle. Phenotypic variables of female ticks obtained at the endpoint of the RNAi experiment were compared to those of control female ticks (non-injected and beta-lactamase dsRNA-injected). Rhimi-PKR silencing was verified by quantitative reverse-transcriptase PCR in whole females and dissected tissues., Results: The Rhimi-PKR transcript was expressed in all developmental stages. Rhimi-PKR silencing was confirmed in whole ticks 4 days after injection, and in the tick carcass, ovary and synganglion 6 days after injection. Rhimi-PKR silencing was associated with an increased mortality and decreased weight of both surviving females and egg masses (P < 0.05). Delays in repletion, pre-oviposition and incubation periods were observed (P < 0.05)., Conclusions: Rhimi-PKR silencing negatively affected female reproductive fitness. The PKR appears to be directly or indirectly associated with the regulation of female feeding and/or reproductive output in R. microplus. Antagonists of the pyrokinin signaling system could be explored for tick control., (© 2022. The Author(s).)

The horn fly, Haematobia irritans, is a blood-feeding parasitic fly with a global distribution that includes Europe, Africa, Asia, and the Americas. The fly has a major detrimental economic impact upon cattle production, with losses estimated at over $800 million annually in the United States and $2.5 billion in Brazil alone. Insecticide resistance in specific horn fly populations has been a problem for many years and there are several mechanisms whereby resistance develops. Little is known about the complement of metabolic enzymes encoded by the horn fly's genome that might provide the fly with detoxification or sequestration pathways to survive insecticide treatments. The cytochrome P450, glutathione S-transferase, and esterase enzyme families contain members that are capable of sequestering and/or detoxifying xenobiotic molecules such as insecticides. We sought to develop a comprehensive dataset of metabolic enzyme-encoding transcript sequences from the adult horn fly, as this is the life stage whose actions directly impose the economic costs to cattle producers. We used an Illumina paired-end read RNA-Seq approach to determine the adult horn fly transcriptomes from laboratory and field populations of horn flies with varying levels of pesticide resistance, including untreated and pyrethroid-treated newly eclosed adult flies. We followed with bioinformatic analyses to discern sequences putatively encoding cytochrome P450, esterase, and GST enzymes. We utilized read-mapping of RNA-Seq data and quantitative real-time polymerase chain reaction (qRT-PCR) to examine gene expression levels of specific P450 transcripts in several fly populations with varying degrees of pesticide resistance., (Published by Elsevier B.V.)

The field of veterinary entomology is primarily associated with the study of arthropods that impact the health of animals. Papers featured in the compilation of highlighted research from 2020 focused on studies conducted by scientists from the federal government that sought to understand and manage arthropods associated with wild and domesticated animals. The topics of these articles included research from the basic tenets of veterinary entomology: 1) biology and ecology of economically important pests, 2) novel control tactics and resistance management, 3) genomics, and 4) pathogen transmission. Key findings of the highlighted papers are presented and discussed to serve as a presentation record., (Published by Oxford University Press on behalf of Entomological Society of America 2021.)

Cattle fever ticks, Rhipicephalus microplus and R. annulatus have been eradicated from the United States and inspectors from the U.S. Department of Agriculture (USDA), Animal Plant Health Inspection Service (APHIS), Cattle Fever Tick Eradication Program (CFTEP) monitor the quarantine zone along the Texas border to prevent the introduction of livestock carrying cattle fever ticks from Mexico. Stray livestock apprehended by CFTEP in the zone are checked for ticks and tested for infectious disease-causing pathogens but are not evaluated for evidence of infection with tick-borne pathogens. We tested blood samples collected from stray cattle by CFTEP inspectors for evidence of infection with tick-borne pathogens. As a comparison group representing U.S. resident cattle, we tested blood samples that had been sent to the Texas A&M Veterinary Medical Diagnostic Laboratory (TVMDL) for unrelated testing. Both sets of blood samples were evaluated using the same specific and broad-spectrum PCR assays. For the border cattle the overall prevalence of infection with one or more tick-borne pathogen was 58.5 % (79/135) with many co-infections, including 30 cattle positive for Babesia bovis and/or Babesia bigemina (22.2 %) and 77 cattle positive for Anaplasma marginale (57 %), three of these animals were also positive for Borrelia theileri. No resident cattle represented by the TVMDL samples were infected with either of the Babesia spp., or with Borrelia theileri, but three were positive for Theileria orientalis and 7.3 % (7/96) were positive for A. marginale. These data show that cattle originating in Mexico have a higher prevalence of infection with tick-borne pathogens relative to resident U.S. cattle and specifically, a proportion are infected with bovine Babesia, which is absent from U.S. cattle populations. Consequently, these stray cattle may be a reservoir of tick-borne pathogens and if populations of Boophilus ticks become reestablished in areas where they had previously been eradicated, could pose a significant risk to the U.S. Cattle industry., (Copyright © 2021. Published by Elsevier GmbH.)

Background: Cattle fever ticks (CFT), Rhipicephalus (Boophilus) annulatus and R. (B.) microplus, are vectors of microbes causing bovine babesiosis and pose a threat to the economic viability of the US livestock industry. Efforts by the Cattle Fever Tick Eradication Program (CFTEP) along the US-Mexico border in south Texas are complicated by the involvement of alternate hosts, including white-tailed deer (Odocoileus virginianus) and nilgai (Boselaphus tragocamelus)., Methods: In the present study, we use a spatially explicit, individual-based model to explore the potential effects of host species composition and host habitat use patterns on southern cattle fever ticks (SCFT, R. (B.) microplus) infestation dynamics and efficacy of eradication schemes., Results: In simulations without eradication efforts, mean off-host larval densities were much higher when cattle were present than when only white-tailed deer and nilgai were present. Densities in mesquite and meadows were slightly higher, and densities in mixed brush were much lower, than landscape-level densities in each of these scenarios. In eradication simulations, reductions in mean off-host larval densities at the landscape level were much smaller when acaricide was applied to cattle only, or to cattle and white-tailed deer, than when applied to cattle and nilgai. Relative density reductions in mesquite, mixed brush, and meadows depended on host habitat use preferences. Shifting nilgai habitat use preferences increasingly toward mixed brush and away from mesquite did not change mean off-host larval tick densities noticeably at the landscape level. However, mean densities were increased markedly in mesquite and decreased markedly in mixed brush, while no noticeable change in density was observed in meadows., Conclusions: Our results suggest that continued integration of field data into spatially explicit, individual-based models will facilitate the development of novel eradication strategies and will allow near-real-time infestation forecasts as an aid in anticipating and preventing wildlife-mediated impacts on SCFT eradication efforts.

Ticks are pests and vectors of diseases that are of public health and veterinary importance. The cattle tick, Rhipicephalus microplus (Canestrini, 1888), is one of the most studied tick species because of its impact on livestock health and production in the tropical and subtropical parts of the world, costing the cattle industry billions annually. Control methods have evolved throughout the years but so has R. microplus. Reliance upon chemical control has created a consistent need to develop new technologies to overcome the pesticide resistance that occurs as the ticks adapt. In order to utilize the more advanced tools such as RNAi or Crispr/Cas9 systems, tick tissues need to be isolated and manipulated. Unfortunately, there are a limited number of dissection guides available providing a detailed view of tick internal anatomy. This manual includes photomicrographs to guide the dissection of R. microplus adults, male and female. Topography and anatomical differences between the internal organs of unfed and gravid adult females are described. We were able to locate the crucial tissues for cattle tick physiology and lay out spatial and temporal guidelines for their identification and dissection. Examples of how this information can be used at the nexus between organismal and molecular research to innovate tick control technologies is discussed., (Copyright © 2021. Published by Elsevier GmbH.)

Background: Some tick species are invasive and of high consequence to public and veterinary health. Socioeconomic development of rural parts of the USA was enabled partly through the eradication by 1943 of cattle fever ticks (CFT, Rhipicephalus (Boophilus) annulatus and R. (B.) microplus). The southern cattle fever ticks (SCFT, R. (B.) microplus) remain a real and present threat to the USA animal agriculture because they are established in Mexico. Livestock-wildlife interactions in the Permanent Quarantine Zone (PQZ) established by the century-old Cattle Fever Tick Eradication Programme (CFTEP) in south Texas endanger its operations., Methods: We describe a spatially-explicit, individual-based model that simulates interactions between cattle, white-tailed deer (WTD, Odocoileus virginianus), and nilgai (Boselaphus tragocamelus) to assess the risk for SCFT infestations across the pathogenic landscape in the PQZ and beyond. We also investigate the potential role of nilgai in sustaining SCFT populations by simulating various hypothetical infestation and eradication scenarios., Results: All infestation scenarios resulted in a phase transition from a relatively small proportion of the ranch infested to almost the entire ranch infested coinciding with the typical period of autumn increases in off-host tick larvae. Results of eradication scenarios suggest that elimination of all on-host ticks on cattle, WTD, or nilgai would have virtually no effect on the proportion of the ranch infested or on the proportions of different tick habitat types infested; the entire ranch would remain infested. If all on-host ticks were eliminated on cattle and WTD, WTD and nilgai, or cattle and nilgai, the proportions of the ranch infested occasionally would drop to 0.6, 0.6 and 0.2, respectively. Differences in proportions of the ranch infested from year to year were due to primarily to differences in winter weather conditions, whereas infestation differences among tick habitat types were due primarily to habitat use preferences of hosts., Conclusions: Infestations in nilgai augment SCFT refugia enabled by WTD and promote pest persistence across the landscape and cattle parasitism. Our study documented the utility of enhanced biosurveillance using simulation tools to mitigate risk and enhance operations of area-wide tick management programmes like the CFTEP through integrated tactics for SCFT suppression.

Filth flies cause billions of dollars of losses annually to the animal production industry. Fluralaner is a relatively new pesticide currently sold for control of fleas, ticks, and mites on companion animals and poultry. We examined the efficacy of fluralaner against three species of filth flies. Insecticide-susceptible horn flies and stable flies were tested topically. Fluralaner outperformed permethrin by > 2-fold for the horn flies but underperformed permethrin by > 45-fold for stable flies at 24 h. House flies were tested topically with fluralaner in comparison to permethrin at 48 h and orally with fluralaner in comparison to imidacloprid at 24 h. Topical fluralaner was 6- to 28-fold as toxic as permethrin in four pyrethroid-resistant strains and not significantly less toxic than permethrin in a susceptible strain and a mildly pyrethroid-resistant strain. There was slight cross-resistance between topically applied fluralaner and permethrin in all five insecticide-resistant strains tested. Oral fluralaner was more toxic than imidacloprid in all four house fly strains tested, 9- to 118-fold as toxic. Oral cross-resistance between imidacloprid and fluralaner was not detected, but imidacloprid resistance was not high in any of the tested strains. Fluralaner shows promise for control of horn flies and house flies.

White-tailed deer ( Odocoileus virginianus ) serve as a host for cattle fever ticks ( Rhipicephalus [ Boophilus ] microplus and Rhipicephalus [ Boophilus ] annulatus ; CFTs); therefore, deer are a concern for CFT control programs in southern Texas, US. Systemic (oral delivery of ivermectin) and topical (permethrin on pelage) treatment devices have been developed for white-tailed deer; however, the efficacy of these treatment options has not been determined for CFTs in southern Texas. Our objectives were to evaluate the effectiveness of CFT treatment strategies by 1) measuring exposure rates of deer to the acaricides permethrin and ivermectin, 2) determining the relationship between CFTs on deer and exposure to the acaricides, and 3) determining if photos from remote cameras at medicated bait sites can be used as a measure of acaricide treatment. We captured 327 deer at four sites in southern Texas. Deer visitation to medicated bait sites was monitored using remote cameras from March 2010 to February 2012. There was no relationship between the presence of permethrin and the probability of being infested with CFTs ( P ≥0.336). The probability of infestation with CFTs decreased as serum ivermectin levels increased for male ( n =18, P =0.098) and female ( n =33, P <0.001) deer. Our results indicate ivermectin may be more effective in treating CFTs than permethrin; thus it would be worthwhile to develop topical acaricides other than permethrin for treating white-tailed deer in southern Texas.

The water buffalo ( Bubalus bubalis ) is an Asian species of bovine that was introduced in Mexico in 1992 as an alternative for milk and meat production. To date, no surveys have been conducted to identify ticks acquired by water buffaloes since their arrival in the country. Here we report, for the first time, the presence of Amblyomma mixtum , a neotropical tick in the Amblyomma cajennense complex, found on water buffaloes from Mexico and discuss its possible implications in veterinary public health for the region.

Water buffaloes (Bubalus bubalis) were introduced to Mexico at the end of the last century. In Mexico, buffaloes are commonly pastured together with cattle; however few studies have been done on buffalo herd health in Mexico. We hypothesized that a better knowledge of the epidemiology of infections shared between cattle and buffaloes may improve herd profitability and promote buffalo production in areas unsuitable to cattle farming. This study aimed to determine the prevalence of antibodies against bovine herpes virus - 1 (BoHV1) in water buffaloes raised on six farms from the state of Veracruz, Mexico. Of 368 buffaloes sampled, 217 (59%) were seropositive for BoHV-1. Age was identified as a risk factor for BoHV-1 infection with buffaloes older than 5 years being the most likely to be infected. Animals more than 7 years old had the highest prevalence (86.0%). Females and males had similar seroprevalence rates. Females with history of abortion had higher prevalence of antiBoHV-1 antibodies than those with no record of abortion. Buffaloes and cattle were raised together in only one of the six farms under study. Interaction with cattle was not a risk factor for BoHV-1 seropositivity. This study showed that BoHV-1 is prevalent among buffalo herds in the state of Veracruz, Mexico. Buffaloes appear to play an important role in the epidemiology of BoHV-1 infection in parts of Mexico when there is no apparent risk of interaction with cattle. Animal health programs established to mitigate the burden caused by BoHV-1 must take into consideration buffaloes when this bovid species is part of the agroecosystem shared with cattle.

The Cattle Fever Tick Eradication Program was the first parasite eradication program of veterinary importance in the United States and is considered to be one of the greatest disease eradication programs of all time. The program's utilization of pasture vacation and dipping of cattle in acaricide has been extremely successful for controlling Rhipicephalus (Boophilus) microplus (Canestrini) and R. (B.) annulatus (Say), collectively known as cattle fever ticks, on cattle along the Texas border with Mexico for decades. However, the increase of white-tailed deer, Odocoileus virginianus (Zimmermann), populations in South Texas over the last 50 yr has compromised the success of the program. R. (B.) microplus and R. (B.) annulatus infestation data have confirmed that O. virginianus can support the maintenance and movement of both species of cattle fever tick within the permanent quarantine or buffer zone in South Texas along the Rio Grande, and also in the cattle fever tick-free area north and east of the buffer zone. Over the last two decades, increasing populations of exotic nilgai antelope, Boselaphus tragocamelus (Pallas), in South Texas have further complicated cattle fever tick eradication efforts. Historical cattle fever tick infestation data, host source data, and geographical data support the continued role of O. virginianus in maintaining reinfestations of R. (B.) microplus and R. (B.) annulatus in South Texas as well as the increasing role of nilgai antelope in cattle fever tick maintenance and dispersal.

Biting arthropods are implicated in the transdermal transmission of Salmonella to bovine peripheral lymph nodes, and such contamination can contribute to increased Salmonella prevalence in processed beef. Since horn flies can acquire Salmonella and then excrete the bacteria in their feces, on-animal fly infestations were conducted in this study to assess whether horn flies have a role in this bacterial transmission. Three Salmonella serotypes were used to assess fly acquisition from and excretion onto cattle. The results indicated that flies can acquire Salmonella from the hide, as assessed by recovery from homogenates of surfacesterilized flies, and that Salmonella persists for at least 5 days in the fly. Fly fecal excreta serves as a bacterial contaminant on the hide, and the overall mean probable estimate of the quantity shed was ≈10(5) most probable number per fly cage area. In 5 days, no transmission of the bacteria to bovine peripheral lymph nodes was evident, prompting an assessment of the effects of prolonged horn fly feeding on transmission. Three groups of animals were infested with flies that had consumed a blood meal containing Salmonella Senftenberg. After 5 days, the study was either terminated or the flies were removed and the cages replenished with unfed flies either once or twice over the course of an 11- or 19-day fly exposure period, respectively. A microlancet-inoculated positive-control animal was included in each group for comparison. The impact of prolonged horn fly feeding was evident, as 8% of lymph nodes cultured were positive from the 5-day exposure, whereas 50 and 42% were positive from 11- and 19-day exposures, respectively. Higher concentrations of Salmonella were recovered from fly-infested animals than from the microlancet-inoculated control, likely a result of repeated inoculations over time by flies versus a single introduction. The data described provide new insights into the transmission dynamics of Salmonella in cattle populations, highlighting a role for biting flies as an important reservoir.

The present study was conducted to elucidate the neuronal pathways between peripheral olfactory and taste sensilla and the synganglion in an Ixodidae tick species. The tarsus of the front legs (olfactory nerves) and the fourth palpal segment (gustatory nerves) of unfed Amblyomma americanum males and females were excised. A neuronal tracer, dextran tetramethylrhodamine, was used for filling of the sensory neurons. The synganglion preparations were examined using a confocal microscope. Neuronal arborizations from the Haller's organ were confined to the olfactory lobes and the first pedal ganglion. The estimated number of olfactory glomeruli ranged from 16 to 22 per olfactory lobe in the females. The number of glomeruli was not counted in males because they were densely packed. Sensory neurons associated with sensilla at the distal end of the palpal organ projected into the palpal ganglion in the synganglion through the palpal nerve. Gustatory sensory neurons associated with palpal sensilla projected into a commissure with several bulges, which are confined in the palpal ganglion. The findings of distinct projection patterns of sensory neurons associated with the Haller's organ and palpal organ in the lone star tick from this study advanced our knowledge on mechanisms of sensory information processing in ticks.

Contamination of cattle peripheral lymph nodes with Salmonella enterica is proposed to occur via a transdermal route of entry. If so, bacteria may be introduced to cattle by biting arthropods. Biting flies, such as horn flies (Haematobia irritans irritans (L.)) (Diptera: Muscidae), are intriguing candidates for transmitting Salmonella to cattle because they provide a route of entry when they breach the skin barrier during blood feeding. Using a green fluorescent protein-expressing strain of Salmonella Montevideo (S. Montevideo-GFP), the current study demonstrated that horn fly grooming subsequent to tactile exposure to the bacteria resulted in acquisition of the bacteria on mouthparts as well as microbial ingestion. Consumption of a bloodmeal containing approximately 10(2), approximately 10(4), or 10(6) S. Montevideo-GFP resulted in horn fly colonization for up to 72 h postingestion (PI). Epifluorescent microscopy indicated that the bacteria were not localized to the crop but were observed within the endoperitrophic space, suggesting that regurgitation is not a primary route of transmission. S. Montevideo-GFP were cultured from excreta of 100% of flies beginning 6-7 h PI of a medium or high dose meal and > 12 h PI in excreta from 60% of flies fed the low-dose meal. Animal hides and manure pats are sources for horn flies to acquire the Salmonella and mechanically transmit them to an animal while feeding. Mean quantities of 5.65-67.5 x 10(2) CFU per fly were cultured from fly excreta passed within 1 d after feeding, suggesting the excreta can provide an additional microbial source on the animal's hide.

Two rates (0.4 mg/kg body weight/d and 0.6 mg/kg body weight/d) of a daily feed-through formulation of novaluron (Novaluron 0.67% active ingredient Cattle Mix), a newer benzoylphenyl urea insecticide, were evaluated for efficacy in controlling the larval stage of horn flies, Haematobia irritans (L.), house flies, Musca domestica L., and stable flies, Stomoxys calcitrans (L.), developing in cow manure. Both rates of feed-through novaluron, delivered consecutively for 10 d, reduced adult emergence of all three species when compared with the untreated control. The presence of deformed puparia indicated that novaluron had an insect growth regulator effect on the developing fly larvae. Both of the feed-through rates evaluated resulted in 100% reduction of adult stable fly emergence after the second day of feed-through treatment. The level of control efficacy observed against these three fly species make this feed-through formulation a candidate for use in an integrated livestock pest management program, particularly in confined cattle production situations where a feed-through product could be easily administered.

The horn fly, Haematobia irritans irritans (L.), is an ectoparasitic blood feeder mainly on cattle. Its cosmopolitan distribution extends from boreal and grassland regions in northern and southern latitudes to the tropics. Stress and blood loss from horn flies can reduce cattle weight gain and milk production. Horn flies show substantial plasticity in their response to winter. Populations in warmer, lower latitudes have been reported to overwinter in a state of dormancy, but most overwinter as active adults in normal or reduced numbers. As latitudes increase, winters are generally colder, and correspondingly, larger percentages of horn fly populations become dormant as pharate adults (a post-pupal, pre-emergent stage) or die. Reports on the effect of elevation on horn fly dormancy at high elevations were contradictory. When it occurs, dormancy takes place beneath cattle dung pats and in the underlying soil. The horn fly's mode of dormancy is commonly called diapause, but the collective research on horn fly diapause (behavioral and biochemical) is not conclusive. Understanding the horn fly's overwintering behaviors can lead to development of pre-dormancy insecticide spray strategies in colder latitudes while other strategies must be determined for warmer regions., (© 2014 SAGE Publications.)

Abstract' Background: For >100 years cattle production in the southern United States has been threatened by cattle fever. It is caused by an invasive parasite-vector complex that includes the protozoan hemoparasites Babesia bovis and B. bigemina, which are transmitted among domestic cattle via Rhipicephalus tick vectors of the subgenus Boophilus. In 1906 an eradication effort was started and by 1943 Boophilus ticks had been confined to a narrow tick eradication quarantine area (TEQA) along the Texas-Mexico border. However, a dramatic increase in tick infestations in areas outside the TEQA over the last decade suggests these tick vectors may be poised to re-invade the southern United States. We investigated historical and potential future distributions of climatic habitats of cattle fever ticks to assess the potential for a range expansion., Methods: We built robust spatial predictions of habitat suitability for the vector species Rhipicephalus (Boophilus) microplus and R. (B.) annulatus across the southern United States for three time periods: 1906, present day (2012), and 2050. We used analysis of molecular variance (AMOVA) to identify persistent tick occurrences and analysis of bias in the climate proximate to these occurrences to identify key environmental parameters associated with the ecology of both species. We then used ecological niche modeling algorithms GARP and Maxent to construct models that related known occurrences of ticks in the TEQA during 2001-2011 with geospatial data layers that summarized important climate parameters at all three time periods., Results: We identified persistent tick infestations and specific climate parameters that appear to be drivers of ecological niches of the two tick species. Spatial models projected onto climate data representative of climate in 1906 reproduced historical pre-eradication tick distributions. Present-day predictions, although constrained to areas near the TEQA, extrapolated well onto climate projections for 2050., Conclusions: Our models indicate the potential for range expansion of climate suitable for survival of R. microplus and R. annulatus in the southern United States by mid-century, which increases the risk of reintroduction of these ticks and cattle tick fever into major cattle producing areas.

The stable fly, Stomoxys calcitrans (L.) (Diptera: Muscidae), is one of the most significant biting flies that affect cattle. The use of traditional insecticides for stable fly control has only a limited success owing to the insect's unique feeding behaviours and immature development sites. A laboratory study was conducted to evaluate the effects of two insect growth regulator (IGR) products, pyriproxyfen and buprofezin, on the development of the immature stages of the stable fly and the effects of pyriproxyfen on oviposition and egg hatch. Both pyriproxyfen and buprofezin had significant inhibitory effects on immature development. The LC(50) s of pyriproxyfen and buprofezin were 0.002 and 18.92 p.p.m., respectively. Topical treatment of adult females with different doses of pyriproxyfen had significant negative effects on both female oviposition and egg hatching when 1- and 3-day-old females were treated, and the effects were dose dependent. A significant reduction in the mean number of eggs laid was observed only at the highest pyriproxyfen dose (8 µg/fly) and egg hatch was unaffected by pyriproxyfen treatment when 5-day-old females were treated. Results from the present study indicate that pyriproxyfen has the potential to be used as part of an integrated stable fly management programme., (Published 2012. This article is a U.S. Government work and is in the public domain in the USA.)

Over a 7 yr period, we monitored the effect of a commercially available, amitraz impregnated anti-tick collar in controlling free-living populations of lone star ticks, Amblyomma americanum (L.) when manually fitted around necks of white-tailed deer, Odocoileus virginianus (Zimmermann). Study animals in treatment and control groups were confined in 38.8 ha game-fenced and densely vegetated treatment plots in South Texas. Tick densities during years 1 and 7 served as untreated pre- and posttreatment comparisons and treatments occurred during years 2 through 5. Reductions in tick densities in the treatment plot were compared against tick densities in a control plot having similar vegetation and numbers of untreated deer. During years of treatment, indices of control pressure ranged from 18.2 to 82.6 for nymphs and 16.9-78.7 for adults, and efficacy, expressed as percentage control during the final year of treatment, was 77.2 and 85.0%, respectively, for nymphal and adult ticks. These data show that acaricidal collar treatments provide efficacies very similar to those achieved with the existing ivermectin-medicated bait and '4-Poster' topical treatment technologies to control ticks feeding on wild white-tailed deer.

A granular formulation of novaluron (Novaluron 0.2G, 0.2% [AI]), a newer benzoylphenyl urea insecticide, was evaluated for its efficacy in controlling the larval stage of horn flies, Haematobia irritans (L.); house flies, Musca domestica L.; and stable flies, Stomoxys calcitrans (L.), in cow manure. Various rates and insecticide placement locations (top, middle, and bottom of manure) were evaluated in this study and all combinations of these variables reduced adult emergence of all three species when compared with the untreated controls. The presence of deformed pupae indicated that novaluron had an insect growth regulator effect on the developing fly larvae. Top, middle, or bottom application rates of 0.125, 0.195, 0.25, and 0.375 g novaluron onto manure samples, reduced adult horn fly emergence by > 90%. Middle and bottom application rates of 0.195, 0.25, and 0.375 g novaluron reduced adult house fly emergence >93%. All rates and placement combinations resulted in >98% reduction of adult stable fly emergence. The level of control efficacy observed against these three fly species along with the ease of use of a granular formulation, make this product an ideal candidate for use in an integrated livestock pest management program.

Analysis of doramectin concentration in blood serum of pastured cattle injected repeatedly (12 treatments) at two different dosage rates and 28-day intervals throughout the year was used to predict the probability that cattle fever ticks could successfully feed to repletion during the interval between any two consecutive treatments. Treatment at ~270 μg/kg indicated that serum doramectin concentration dropped below the baseline concentration estimated for tick survival (8 ppb) in 7 of the 12 treatments. However, the longest period between any two treatments during which the doramectin concentration remained below the 8 ppb baseline level for successful tick feeding was 15 days, making it virtually impossible for any ticks to reach ovipositional status prior to a subsequent treatment. At a dosage rate of ~540 μg/kg, the concentration dropped below the baseline tick survival level (8 ppb) only once, following the initial treatment, and the duration during which the concentration remained below the baseline level prior to the subsequent treatment was only 6 days. Thus, at the high dosage rate results indicated, with absolute certainty, that no ticks could successfully feed to repletion between any two consecutive treatments. Based on the data obtained in the study it was concluded that analysis of doramectin concentration in serum of treated animals would be a reliable predictor for assessing the probability that ticks could successfully develop to repletion. More importantly, results demonstrated that the trial policy, instituted by the Cattle Fever Tick Eradication Program, of repeatedly treating cattle with doramectin injections at 25-28 day intervals for eliminating cattle fever ticks would produce little or no risk of any viable ticks developing to repletion and re-infesting the field between treatment applications.

Species identification and global positioning system coordinates of infestations of cattle fever ticks, Rhipicephalus (Boophilus) annulatus (Say) and Rhipicephalus (Boophilus) microplus (Canestrini), were determined for 790 specimens submitted to the National Veterinary Services Laboratory between 1 October 1999 and 30 September 2010. Cattle fever tick specimens obtained by personnel of the United States Department of Agriculture-Animal and Plant Health Inspection Service-Cattle Fever Tick Eradication Program from infested cattle and wildlife along the Texas/ Mexico border were submitted for identification, as required by the program. A geographic information system database was developed that incorporates location, collection, and infestation records. Submitted ticks came from 11 Texas counties and were comprised of 19.5% R. (B.) annulatus and 80.5% R. (B.) microplus. Maps produced from this study locate and define the parapatric boundary between R. (B.) annulatus and R. (B.) microplus.

The therapeutic and persistent efficacy of a single subcutaneous injection of a long-acting formulation of moxidectin at a concentration of 1 mg/kg body weight was determined against Rhipicephalus (Boophilus) microplus (Canestrini), along with the concentration-time blood sera profile in treated cattle. The therapeutic efficacy against ticks of all parasitic stages on cattle at the time of treatment was >99.9%, and the mean tick number, index of fecundity, engorgement weight, and egg mass weight of ticks recovered from treated animals were all significantly lower than ticks from untreated animals. The index of fecundity, engorgement weight of females, and egg mass weight of ticks recovered from treated animals infested at weekly (7-d) intervals between 14 and 63 d posttreatment were significantly lower than for ticks on untreated animals, whereas the number of ticks per animal recovered from treated cattle remained lower than that of untreated cattle for up to 49 d posttreatment. The percentage control remained >99% at weekly intervals between 14 and 49 d posttreatment, which is the minimum level of efficacy considered acceptable for use in the United States Cattle Fever Tick Eradication Program. The serum concentration of moxidectin in treated cattle increased to 25.6 ppb (parts per billion) within 1 d after treatment, and peaked at 47.3 ppb at 8 d posttreatment. Moxidectin sera levels remained above the estimated 100% threshold level for elimination of feeding ticks (5-8 ppb) for 44-53 d after treatment. The label claim of 50 d of prevention against reinfestation for the long-acting moxidectin formulation used in the study was supported by the efficacy and sera concentration data obtained. Based on these results, cattle could be treated at 63-d intervals with minimal risk of viable ticks detaching from treated animals. This treatment interval would be 4.5-fold longer than the presently required treatment interval of 14 d, thus leading to approximately 75% reduction in gathering and handling costs of cattle incurred by producers.

The efficacies of a 20% 1-methyl-propyl-2- (hydroxyethyl)-1-piperidinecarboxylate (picaridin) spray, 20% 3-(N-acetyl-N-butyl)aminopropionic acid ethyl ester (IR3535) spray, 20% picaridin lotion, 10% IR3535 lotion, and 33% N,N-diethyl-3-methylbenzamide (deet) cream in repelling nymphal lone star ticks, Amblyomma americanum (L.), were determined at 2-h intervals over 12 h using human subjects. A repellent formulation was applied in a 5-cm-wide band encircling a volunteer's lower leg. For each challenge, 70 host-seeking nymphs were released on each volunteer's ankle, and tick locations were recorded 10 min after the ticks were released. Ticks that crawled entirely across the repellent band were considered not repelled. For all formulations and time points, significantly fewer (all P < 0.0001) A. americanum nymphs crossed the treatment bands on the volunteers' ankles than crossed the corresponding area on the untreated control legs. Formulations containing > or = 20% active ingredient were highly effective, with <10% of the ticks crossing through the treatment bands for any challenge during the 12 h. At least 40% of ticks exposed to any formulation for any challenge fell or crawled off the volunteers. There was no difference in effectiveness between the 20% spray and 20% lotion formulations of picaridin. The 10% IR3535 lotion was significantly less effective than the formulations with higher concentrations of repellent. In the formulations tested, deet, picaridin, and IR3535 provided lasting protection against A. americanum.

The stable fly, Stomoxys calcitrans L. (Diptera: Muscidae), is one of the most significant pests of livestock in the United States. The identification of targets for the development of novel control for this pest species, focusing on those molecules that play a role in successful feeding and reproduction, is critical to mitigating its impact on confined and rangeland livestock. A database was developed representing genes expressed at the immature and adult life stages of the stable fly, comprising data obtained from pyrosequencing both immature and adult stages and from small-scale sequencing of an antennal/maxillary palp-expressed sequence tag library. The full-length sequence and expression of 21 transcripts that may have a role in chemosensation is presented, including 13 odorant-binding proteins, 6 chemosensory proteins, and 2 odorant receptors. Transcripts with potential roles in sex determination and reproductive behaviors are identified, including evidence for the sex-specific expression of stable fly doublesex- and transformer-like transcripts. The current database will be a valuable tool for target identification and for comparative studies with other Diptera.

From 1907 when the fever tick eradication campaign began until 1933, the tick eradication methods of dipping cattle in an acaricide or "pasture vacation" were enormously successful in eradicating southern cattle ticks [Rhipicephalus (Boophilus) microplus (Canestrini)], until failures began to occur in some areas of Florida. Regarding the failures in Florida, the consensus was that populations of white-tailed deer [Odocoileus virginianus (Zimmermann)] infested with southern cattle ticks were responsible. After numerous deer in several counties were killed, eradication was achieved in Florida. As in Florida, in Texas increasing numbers of failures of the pasture vacation approach to tick eradication from the 1970s to the present are known to be related to the abundance of white-tailed deer and perhaps other wild ungulate species. A sizable body of evidence confirms the hypothesis that white-tailed deer support the dispersal and maintenance of both cattle ticks [Rhipicephalus (Boophilus) annulatus (Say)] and southern cattle ticks (cattle fever ticks) within the permanent quarantine or buffer zone in South Texas along the Rio Grande, as well as in the so-called free ("cattle fever tick-free") area north and east of the buffer zone and extending to the east coast of the United States. As of August 2009, in addition to the permanent quarantine zone of approximately 2233 km2, three temporary preventative or blanket quarantines were established. Currently, only two methodologies exist to control ticks feeding on white-tailed deer: (1) a systemic treatment method involving dispersal of ivermectin-medicated corn, Zea mays L.; and (2) two topical treatment methods, '4-poster' deer treatment bait stations and '2-poster' deer treatment feeder adapters, both of which passively apply topically active acaricide to deer for the eradication of populations of cattle fever tick associated with white-tailed deer. This study presents and summarizes confirmational support for the role of white-tailed deer derived from historical accounts, circumstantial evidence from review of recent infestations, and cattle fever tick infestations on white-tailed deer that were live-captured and examined specifically for cattle fever ticks.

Female engorgement weight, oviposition, and molting times of larvae and nymphs of Amblyomma maculatum Koch (Acari: Ixodidae) were studied at various photoperiods under constant humidity and temperature in the laboratory. Ticks were held at photoperiods of 0:24, 10:14, 12:12, or 14:10 (L:D) h from egg through unfed nymphal stage and then at either the same or a different regime from fed nymphs to adults. No significant effects were observed on oviposition, female engorgement weights, survival, or molting time to unfed nymphs. Nymphal molting times were significantly shorter at the short-day regime (10:14) during the larval stage and 12:12 during the nymphal stage compared with those held at either 14:10 during both life periods or at 0:24 during both life periods. Longer molting times also were observed in ticks held at 12:12 during the larval phase and either 10:14, 12:12, or 0:24 during the nymphal phase compared with 14:10 during both life periods or 0:24 during both life periods. Ticks held at 10:14 during the larval phase and at 0:24 or 10:14 had longer molting times compared with those at 14:10 or 0:24 during both life periods. No differences in survival to either nymphal or adult stages were observed at any regime, and at day 25 no individuals were observed to be in developmental diapause. This study demonstrates that developmental diapause does not seem to be photoperiodically induced in fed nymphal A. maculatum in the laboratory.

A gel formulation formed by incorporating technical doramectin into a 10% hydroxypropyl methylcellulose aqueous solution was used to subcutaneously inject steers at varying dosages. Doramectin serum concentration of steers receiving 600 microg (AI)/kg body weight declined from 21.9 ppb at 0.5 wk to below detectable at 8 wk postinjection. The 1,200 microg (AI)/kg injection resulted in serum concentrations of 29.1 ppb at 0.5 wk and declined to 0.5 ppb at 8 wk postinjection. Both the 600 and 1,200 microg (AI)/kg injections provided 100% inhibition of index of fecundity (IF) in adult lone star ticks, Amblyomma americanum L. (Acari: Ixodidae) through week 8, after which inhibition declined to 79.4 and 45.3%, respectively, during the 12th week posttreatment. For steers treated at 600 microg (AI)/kg, mortality of adult horn flies, Hematobia irritans L. (Diptera: Muscidae), declined from 16.9% during week 2 to 3.1% during week 7 postinjection. The blood from steers treated at 1,200 microg (AI)/kg resulted in a similar decline in mortality of blood fed adult horn flies from 29.4% during week 1 to 4.0% during week 7. The 600 microg (AI)/kg treatment provided complete control of larval horn flies in the manure for 9 wk, whereas the 1,200 microg (AI)/kg injection gave complete control for 14 wk posttreatment. The doramectin gel formulation provided long-lasting delivery of doramectin to cattle and extended control of lone star ticks and larval horn flies. Such a simple and inexpensive formulation could be useful in tick eradication programs by reducing the frequency of gathering cattle.

Steers were treated with doramectin or eprinomectin by daily oral capsule for 28 consecutive days. The level of doramectin in the serum of steers treated at 200 microg/kg/d reached a maximum of 104.0 +/- 22.1 ppb at day 21 and declined from 93.3 +/- 20.5 ppb on the final day of treatment to below detectable by day 56. Steers treated at 50 microg/kg/d reached a maximum level of doramectin in the serum of 24.7 +/- 1.2 ppb on day 21 and declined from 24.7 +/- 0.6 ppb on the final day of treatment to less than detectable on day 42. Both doramectin dosages provided 100% control of estimated larvae (EL) of Amblyomma americanum (L.) (Acari: Ixodidae) throughout the 28-d treatment period. Daily oral treatment with eprinomectin at a dosage of 200 microg/kg for 28 consecutive days produced a maximum concentration in the serum of 41.6 +/- 11.0 ppb at day 14. On the final day of eprinomectin treatment, the serum concentration was 38.3 +/- 5.9 ppb. Seven days later at day 35, eprinomectin was not detectable in the serum. For steers treated at 50 microg/kg/d for 28 consecutive days, the serum level of eprinomectin reached a maximum of 10.0 +/- 3.0 ppb on day 28 and was undetectable on day 35. Both eprinomectin dosages provided complete control of EL of A. americanum during the 28-d treatment period. Because eprinomectin is efficacious against A. americanum at lower serum levels in cattle and is eliminated from the serum at a more rapid rate than either doramectin or ivermectin, it provides advantages for use in applications such as the medicated bait for control of ticks on white-tailed deer and could have potential for use in the Cattle Fever Tick Eradication Program.

Acetylcholinesterase (AChE) cDNA from individual field-collected diazinon-resistant horn flies was amplified by RT-PCR. Sequencing of the amplification products revealed that 8/12 of the diazinon-resistant horn flies contained a point mutation previously associated with resistance to organophosphates in house flies and Drosophila, strongly suggesting that this cDNA encodes the AChE that is the target site for organophosphate (OP) pesticide. The point mutation (G262A) resulted in a shift from glycine to alanine in the mature HiAChE amino acid sequence at position 262. Allele-specific PCR and RLFP assays were developed to diagnose the presence or absence of the G262A mutation in individual flies. Use of the allele-specific assays each demonstrated the presence of the G262A mutation in 10 of 12 individual field-collected flies, demonstrating higher sensitivity than direct sequencing of RT-PCR amplification products. The G262A mutation was found in additional fly populations previously characterized as OP-resistant, further supporting that this AChE is the target site for OP pesticide. The allele-specific assay is a useful tool for quantitative assay of the resistance allele in horn fly populations.

Powder formulations of three species of entomopathogenic fungi were evaluated for their pathogenic effect upon adult horn flies, Hematobia irritans (L.) (Diptera: Muscidae). Flies were treated with conidia and blastospores of the entomopathogenic fungi Beauveria bassiana (Bals.) Vuill. (strain GHA), Metarhizium anisopliae (Metschnikoff) Sorokin (strain ESCI), and Paecilomyces fimosoroseus (Wize) Brown & Smith (strain ARSEF 3581) in the laboratory. At 4 d postexposure, flies treated with B. bassiana had an average of 98.4% mortality versus 43.5% from treatment with M. anisopliae and 13.0% from treatment with P. fiimosoroseus. At 7 d postexposure, flies treated with B. bassiana had an average of 100.0% mortality compared with 73.0% from treatment with M. anisopliae and 33.3% from treatment with P.fumosoroseus. Mean lethal time (LT50) was 2.70, 4.98, and 7.97 d for B. bassiana, M. anisopliae, and P. fiumosoroseus, respectively. Entomopathogenic fungi such as B. bassiana and M. anisopliae may have the potential for controlling populations of horn flies. These studies indicate that B. bassiana and M. anisopliae were not only pathogenic to adult horn flies, but they caused mortality in a short time.

Field studies were conducted during 1999-2001 in two climatic/edaphic areas of Georgia (Southern Piedmont and East Gulf Coastal Plain) to test the hypothesis that precision placement of aldicarb with cotton seed in hill planting at spatially specific intervals could decrease insecticide use for management of tobacco thrips, Frankliniella fusca (Hinds). Precision-placed aldicarb controlled thrips during cotton seedling stages using per ha amounts of one-half or less than standard in-furrow application rates with no significant differences in yield. Residual analysis of cotton plants showed that plants in precision placement plots had as much or more aldicarb and aldicarb metabolites present as compared with cotton treated with conventional in-furrow treatments. Higher rates of precision-placed aldicarb did cause phytotoxic burning early in the growing season, but no significant impact on yield was observed.