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Established populations of Aedes aegypti, a mosquito vector of multiple major arthropod-borne viruses, were first found in three California (CA) cities in 2013. From 2013 to April 2021, Ae. aegypti thwarted almost all control efforts to stop its spread and expanded its range to 308 cities, including Exeter, in 22 counties in CA. Population genomic analyses have suggested that multiple genetically distinct Ae. aegypti populations were introduced into CA. However Ae. aegypti collected for the first time in 2014 in Exeter, appeared to be different from three major genetic clusters found elsewhere in CA. Due to intense control efforts by the Delta Vector Control District (DVCD), Ae. aegypti was thought to have been eliminated from Exeter in 2015. Unfortunately, it was recollected in 2018. It was not clear if the reemergence of Ae. aegypti in Exeter was derived from the bottlenecked remnants of the original 2014 Exeter population or from an independent invasion from a different population derived from surrounding areas. The goal of this work was to determine which of these scenarios occurred (recovery after bottleneck or reintroduction after elimination) and if elimination and reintroduction occurred to identify the origin of the invading population using a population genomic approach. Our results support the reintroduction after elimination hypothesis. The source of reintroduction, however, was unexpectedly from the southern CA cluster rather than from other two geographically closer central CA genetic clusters. We also conducted a knockdown resistance mutation profile, which showed Exeter 2014 had the lowest level of resistant alleles compared to the other populations, could have contributed towards DVCD’s ability to locally eliminate Ae. aegypti in 2014.

Las pérdidas económicas causadas por parásitos del bovino en México se calcularon anualmente. Los principales factores considerados para esta evaluación incluyeron el número total de animales a riesgo, los posibles efectos dañinos del parasitismo sobre la producción de leche o ganancia de peso, y los decomisos de subproductos pecuarios. Las pérdidas económicas fueron estimadas en dólares americanos (US$) y se basaron en las pérdidas del rendimiento productivo de animales no tratados. Estas estimaciones reflejan los principales efectos de seis parásitos o grupos de parásitos sobre la producción bovina. El impacto económico potencial (millones de dólares) fue: nematodos gastrointestinales US$ 445.10; coccidias (Eimeria spp.) US$ 23.78; duelas del hígado (Fasciola hepatica) US$ 130.91; garrapatas (Rhipicephalus microplus) US$ 573.61; mosca de los cuernos (Haematobia irritans) US$ 231.67; y mosca de los establos (Stomoxys calcitrans) US$ 6.79. En general, las pérdidas anuales causadas por los seis principales parásitos del bovino en México se estimaron en US$ 1.41 mil millones. Considerando que la población bovina nacional en 2013 fue de 32.40 millones de bovinos, la pérdida anual estimada fue de US$ 43.57 por animal. Se hace mención de las limitaciones que tienen el uso de algunas referencias para las estimaciones, particularmente cuando se extrapolan situaciones locales a una escala nacional. Sin embargo, el resultado general obtenido en este estudio demuestra la magnitud e importancia del parasitismo en el ganado de México y los desafíos para maximizar la rentabilidad de la industria ganadera sin recurrir al uso de estrategias de control integrado sustentable de parásitos. ABSTRACT Here, economic losses caused by cattle parasites in Mexico were estimated on an annual basis. The main factors taken into consideration for this assessment included the total number of animals at risk, potential detrimental effects of parasitism on milk production or weight gain, and recor

Se evaluó un programa de control integral en 15 ranchos con el fin de cuantificar los costos de producción asociados con el control químico de garrapatas. Bajo un programa combinado de control químico e inmunológico se inmunizaron 587 animales de 15 ranchos,El costo del control químico de las garrapatas en la región fue de $408.3 pesos por animal, mientras que el programa combinado fue de $128 pesos por animal, lo que significó una reducción de 68.63 % por concepto de la compra de ixodicidas. La extrapolación de estos datos a la ganadería nacional con un hato estimado en 30 millones de cabezas de ganado bovino, puede significar una pérdida que equivale a 12 248 994 889 millones de pesos mexicanos. El uso de un programa combinado de control disminuiría estas pérdidas hasta 3843 015 332, es decir, 68.63 % de las pérdidas en la ganadería nacional.

Tick-borne pathogens cause diseases that greatly impact animal health and production worldwide. The ultimate goal of tick vaccines is to protect against tick-borne diseases through the control of vector infestations and reducing pathogen infection and transmission. Tick genetic traits are involved in vector-pathogen interactions and some of these molecules such as Subolesin (SUB) have been shown to protect against vector infestations and pathogen infection. Based on these premises, herein we characterized the efficacy of cattle vaccination with tick proteins involved in vector-pathogen interactions, TROSPA, SILK, and Q38 for the control of cattle tick, Rhipicephalus (Boophilus) microplus infestations and infection with Anaplasma marginale and Babesia bigemina. SUB and adjuvant/saline placebo were used as positive and negative controls, respectively. The results showed that vaccination with Q38, SILK and SUB reduced tick infestations and oviposition with vaccine efficacies of 75% (Q38), 62% (SILK) and 60% (SUB) with respect to ticks fed on placebo control cattle. Vaccination with TROSPA did not have a significant effect on any of the tick parameters analyzed. The results also showed that vaccination with Q38, TROSPA and SUB reduced B. bigemina DNA levels in ticks while vaccination with SILK and SUB resulted in lower A. marginale DNA levels when compared to ticks fed on placebo control cattle. The positive correlation between antigen-specific antibody titers and reduction of tick infestations and pathogen infection strongly suggested that the effect of the vaccine was the result of the antibody response in vaccinated cattle. Vaccination and co-infection with A. marginale and B. bigemina also affected the expression of genes encoding for vaccine antigens in ticks fed on cattle. These results showed that vaccines using tick proteins involved in vector-pathogen interactions could be used for the dual control of tick infestations and pathogen infection.

The horn fly Haematobia irritans (Linnaeus, 1758) (Diptera: Muscidae) is one of the most important ectoparasites of cattle. The parasitism of horn flies interferes with cattle feeding, thus reducing weight gain and milk production. Additionally, horn flies are mechanical vectors of pathogens that cause disease in cattle. The aims of this study were to identify microorganisms in partially fed female horn flies through mining of expressed sequence tags (ESTs) and to characterize microorganism prevalence using real-time RT-PCR. Seven unigenes containing 24 ESTs were homologous to infectious agents. Microorganisms identified in partially fed female horn flies ESTs included Nora virus (3 unigenes; 8 ESTs), Wolbachia endosymbionts (3 unigenes; 3 ESTs), and Mycobacterium bovis (1 unigene; 13 ESTs). These results expanded the repertoire of microorganisms that could cause persistent infections or be mechanically transmitted by horn flies and support further studies on the role of horn flies in the epidemiology of these pathogens in Mexico.

[Background]: The horn fly, Haematobiaaa irritans (Linnaeus, 1758) (Diptera: Muscidae) is one of the most important ectoparasites of pastured cattle. Horn flies infestations reduce cattle weight gain and milk production. Additionally, horn flies are mechanical vectors of different pathogens that cause disease in cattle. The aim of this study was to conduct a functional genomics study in female horn flies using Expressed Sequence Tags (EST) analysis and RNA interference (RNAi). [Results]: A cDNA library was made from whole abdominal tissues collected from partially fed adult female horn flies. High quality horn fly ESTs (2,160) were sequenced and assembled into 992 unigenes (178 contigs and 814 singlets) representing molecular functions such as serine proteases, cell metabolism, mitochondrial function, transcription and translation, transport, chromatin structure, vitellogenesis, cytoskeleton, DNA replication, cell response to stress and infection, cell proliferation and cell-cell interactions, intracellular trafficking and secretion, and development. Functional analyses were conducted using RNAi for the first time in horn flies. Gene knockdown by RNAi resulted in higher horn fly mortality (protease inhibitor functional group), reduced oviposition (vitellogenin, ferritin and vATPase groups) or both (immune response and 5’-NUC groups) when compared to controls. Silencing of ubiquitination ESTs did not affect horn fly mortality and ovisposition while gene knockdown in the ferritin and vATPse functional groups reduced mortality when compared to controls. [Conclusions]: These results advanced the molecular characterization of this important ectoparasite and suggested candidate protective antigens for the development of vaccines for the control of horn fly infestations.

The cattle ticks, Rhipicephalus (Boophilus) spp., affect cattle production in tropical and subtropical regions of the world. Tick vaccines constitute a cost-effective and environmentally friendly alternative to tick control. The recombinant Rhipicephalus microplus Bm86 antigen has been shown to protect cattle against tick infestations. However, variable efficacy of Bm86-based vaccines against geographic tick strains has encouraged the research for additional tick-protective antigens. Herein, we describe the analysis of R. microplus glutathione-S transferase, ubiquitin (UBQ), selenoprotein W, elongation factor-1 alpha, and subolesin (SUB) complementary DNAs (cDNAs) by RNA interference (RNAi) in R. microplus and Rhipicephalus annulatus. Candidate protective antigens were selected for vaccination experiments based on the effect of gene knockdown on tick mortality, feeding, and fertility. Two cDNA clones encoding for UBQ and SUB were used for cattle vaccination and infestation with R. microplus and R. annulatus. Control groups were immunized with recombinant Bm86 or adjuvant/saline. The highest vaccine efficacy for the control of tick infestations was obtained for Bm86. Although with low immunogenic response, the results with the SUB vaccine encourage further investigations on the use of recombinant subolesin alone or in combination with other antigens for the control of cattle tick infestations. The UBQ peptide showed low immunogenicity, and the results of the vaccination trial were inconclusive to assess the protective efficacy of this antigen. These experiments showed that RNAi could be used for the selection of candidate tick-protective antigens. However, vaccination trials are necessary to evaluate the effect of recombinant antigens in the control of tick infestations, a process that requires efficient recombinant protein production and formulation systems.

[ES]: La aplicación de ixodicidas durante mucho tiempo ha sido la alternativa de elección para el control de la garrapata Boophilus microplus, sin embargo, actualmente el uso de los ixodicidas tiene una eficacia limitada en la reducción de las infestaciones debido al desarrollo de poblaciones de garrapatas resistes. La resistencia a ixodicidas es un problema creciente que necesita ser atendido, por que en este momento está afectando la competitividad de la ganadería y la economía de miles de productores en México. La solución de este problema requiere de la implementación de programas de investigación que coadyuven a dilucidar los mecanismos moleculares de la resistencia con el fin de encontrar nuevos blancos moleculares para el diagnóstico y para el desarrollo de vacunas recombinantes. El uso reciente de nuevas herramientas genómicas y los enfoques de genética reversa, son una extraordinaria herramienta que podría ayudar en el descubrimiento de nuevos genes de interés diagnóstico ó imunoprofiláctico, contribuyendo así al mejoramiento de las estrategias de control de garrapatas y los programas de mitigación de la resistencia a ixodicidas. El propósito de esta revisión es compilar diferentes tópicos actuales relacionados con la biología de las garrapatas, resistencia a los ixodicidas, y las perspectivas de la investigación genómica en la garrapata Boophilus microplus, iniciando con algunas consideraciones biológicas y moleculares acerca de la nueva clasificación de este ectoparásito, hasta el análisis de la resistencia a los ixodicidas, su impacto en la industria ganadera en México y la aplicación de la genómica en la solución de problemas asociados con el control de las garrapatas mediante el diseño de nuevos métodos diagnósticos así como el desarrollo de vacunas contra garrapatas., [EN]: The application of Ixodicides has been considered for a long time the alternative for control of the cattle tick Boophilus microplus, however, its use is currently limited in reducing tick infestations, due to the appearance of resistant field tick populations. Ixodicide resistance is a growing problem that needs to be attended, because, it is currently affecting the competitiveness of the Mexican cattle industry in general and in particular the income of cattle producers. The solution to this problem needs to increase the budget dedicated to basic research in order to elucidate the molecular mechanisms of ixodicide resistance leading to the discovery of new molecular targets for ixodicide resistance detection and recombinant vaccine development. The recent use of new genomic tools, as well as reverse genetics approaches, will provide an extraordinary contribution to the improvement of tick control strategies and ixodicide resistance mitigation programs. The aim of the present review is to make a compilation of different topics related with acaricide resistance in the cattle tick Boophilus microplus, starting with some biological and molecular considerations on its new classification, to the analysis of ixodicide resistance, its impact on the Mexican cattle industry and the perspective of the genomic research in order to solve the problems associated to tick control, new diagnostic tools and development of tick vaccines.

Acaricide resistance in Boophilus microplus has been studied for the last 20 years from the toxicology, metabolic and genomic points of view, however, only few methods for molecular detection of resistance have been developed. Despite the relatively poor sensitivity for resistance detection, bioassays remain the method of choice for susceptibility evaluation of tick populations, based on their toxicological response after exposure to acaricides. Metabolic detoxification of acaricides is known to be mediated by multigene- families of enzymes such as GST, Esterases and Mixed Function Oxidases (cytochrome P450). In addition, target site insensitivity has been studied on the sodium channel and acetylcholinesterase genes. The use of genomics to understand acaricide resistance in B. microplus will play a major role in unraveling the molecular mechanisms of resistance. Advances in genomics, will accelerate the development of new diagnostic and immunoprophylactic tools based on new vaccine candidates, and new molecular targets for acaricide resistance detection and improvement of strategies for the control of ticks and tick-borne diseases in tropical and subtropical areas of Mexico.

Anaplasma marginale is a tick-borne pathogen of cattle that causes the disease bovine anaplasmosis worldwide. Major surface proteins (MSPs) are involved in host–pathogen and tick–pathogen interactions and have been used as markers for the genetic characterization of A. marginale strains and phylogenetic studies. MSP1a is involved in the adhesion and transmission of A. marginale by ticks and varies among geographic strains in the number and sequence of amino-terminal tandem repeats. The aim of this study was to characterize the genetic diversity of A. marginale strains collected from countries in North and South America, Europe, Asia, Africa and Australia, inclusive of all continents. In this study, we characterized 131 strains of A. marginale using 79 MSP1a repeat sequences. These results corroborated the genetic heterogeneity of A. marginale strains in endemic regions worldwide. The phylogenetic analyses of MSP1a repeat sequences did not result in clusters according to the geographic origin of A. marginale strains but provided phylogeographic information. Seventy-eight percent of the MSP1a repeat sequences were present in strains from a single geographic region. Strong (≥80%) support was found for clusters containing sequences from Italian, Spanish, Chinese, Argentinean and South American strains. The phylogenetic analyses of MSP1a repeat sequences suggested tick–pathogen co-evolution and provided evidence of multiple introductions of A. marginale strains from various geographic locations worldwide. These results contribute to the understanding of the genetic diversity and evolution of A. marginale and tick–pathogen interactions.