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An epidemiological (cross-sectional) and therapeutic (randomized controlled field trial) study was conducted on sheep lice in Sayint district, South Wollo, Northeast Ethiopia. The aim of the study was to (i) quantify the magnitude of sheep lice burden and the prevailing lice species, (ii) identify and quantify risk factors affecting lice infestation in sheep, and (iii) evaluate the efficacy of commonly used acaricides (diazinon and ivermectin) against sheep lice infestation. A total of 232 randomly selected sheep, 15 naturally infested sheep, and 80 viable Bovicola ovis lice were used for epidemiological, in vivo, and in vitro based therapeutic studies, respectively. Three naturally infested treatment groups each with five sheep (Group I—treated with diazinon, Group II—treated with ivermectin, and Group III—untreated/control) were used for in vivo therapeutic study. Lice count for the corresponding treatment groups was conducted on weekly basis using clinical and parasitological examinations. We used logistic regression to quantify the association between different putative risk factors and lice infestation, and the independent t-test and one-way ANOVA to compare the within and between treatment group mean lice count variations. The overall prevalence of sheep lice in the study area was 48.3%, where Bovicola ovis (83%) was the dominant lice species. Hair length, body condition, agroecology, and season were significantly (P < 0.05) associated with sheep lice infestation. Analysis of variance revealed that mean lice count significantly (P < 0.05) varies between treatment groups. A significant (P < 0.05) low mean lice cunt was recorded in diazinon- and ivermectin-treated groups when compared to untreated group. The in vivo efficacy of ivermectin (81%) was lower than diazinon (99%) when compared to the efficacy standard limit (98–100%). However, no significant mean lice count variation was recorded between the two groups. In vivo (99%) and in vitro (95%) assay evidence revealed that diazinon was highly effective for the treatment of sheep lice. According to this study, it can be concluded that the magnitude of sheep lice burden in Sayint district was found to be high and this could have a potential negative impact on sheep productivity and health performances. Thus, applying an appropriate intervention measure including the right choice of effective acaricides could help to control sheep lice in the study area.

Context: The third Australian national survey on control practices for internal and external parasites of sheep, following similar surveys in 2003 and 2011. Aims: To document current parasite control practices and attitudes, measure change and to provide a benchmark against which to assess future practices and attitudes. Methods: An online survey emailed to 6460 sheep producers, with a paper version supplied on request. A follow up short survey was conducted to assess non-response bias. Analysis by region and key sheep enterprise. Key results: There were 354 and 250 useable responses to the main and short surveys respectively. Mean reported rainfall of 407 mm in 2018 was 27% lower than the average for respondents and >200 mm lower than mean reported rainfall in the previous surveys. The top three methods for worm control over the past 5 years were preventative treatments (74%), preparing clean pastures by spelling paddocks (62%) and treatment on the basis of faecal worm egg count (WEC, 54%). The proportion of respondents using WEC monitoring in 2018 was 40.4%, with a mean frequency of 3.1/year, and this was unaffected by sheep class. The frequency of anthelmintic treatment for ewes and lambs and weaners was 2.1/year. Of the respondents, 36.7% had performed an anthelmintic resistance test in the previous 5 years. The most popular flystrike control methods were timing of crutching (76.4%), preventative chemical treatment (75.9%), timing of shearing (63.1%), mulesing (46.8%) and genetic selection (46.4%). Pain relief was widely used for mulesing ewes (86.6%) and weathers (90.9%). Only 17.3% used Australian Sheep Breeding Values for traits in rams. Most respondents reported 'evidence of lice' in the past 5 years (55.8%) and had treated for lice off shears (50.1%), short wool (16.6%) or long wool (6.6%), with only 26.7% having not treated at all in the period. Web-based sources of information on parasite control have become increasingly important. Conclusions: Notable changes since the earlier surveys were high rates of pain relief when mulesing, an increase in the use of Australian Sheep Breeding Values for parasite-related traits, an increase in WEC monitoring since 2011 and an increased use of web-based resources. Implications: Parasite control remains important for sheep producers and continues to evolve with new drugs and approaches. The surveys highlight the effectiveness of extension networks and identify where more attention is required. An online national survey of Australian sheep producers was undertaken to benchmark Australian sheep parasite control practices in 2018. The aims of the survey were to document wool growers' current parasite control practices and attitudes, to measure the change in producer parasite control practices from those in the previous two surveys and to provide a benchmark against which to measure future parasite control practices and attitudes. [ABSTRACT FROM AUTHOR]

The sheep body louse, Bovicola ovis (B. ovis), is one of the most significant ectoparasites affecting Australia's sheep flocks. Despite this, detection methods for B. ovis infestation are limited to visual inspection and ELISA. A colourimetric loop-mediated isothermal amplification (LAMP) method was developed and evaluated for the detection of B. ovis DNA. Diagnostic sensitivity and specificity of LAMP were compared with those of visual inspection and PCR and validated using field samples collected from 22 farms. Two different DNA extraction methods using a commercial kit and a boiling method were also compared. The highest sensitivity and specificity were observed when PCR was used and DNA was extracted using a commercial kit. Compared with PCR, the LAMP assay demonstrated a sensitivity and specificity of 90% and 92% when DNA was extracted by a commercial kit and 100% and 75% when DNA was extracted by the boiling method, respectively. The LAMP test developed in this study could potentially serve as a point-of-care diagnostic tool for monitoring of sheep flocks as well as surveillance of B. ovis populations. [ABSTRACT FROM AUTHOR]

Using a previously developed predictive model, three different management practices were examined in combination with post-shearing chemical treatments for lice, to determine which combinations could provide cost-effective reductions in lice prevalence over a 20-year period. The model included nine sheep production regions across Australia, all of which have different regional flock prevalence of lice and mean numbers of sheep/property. The lice prevalence model simulated the effects of four management options on Australian lice prevalence and on financial return (expressed as net present value) over a 20-year period. Management options modelled in this study were: treatment for eradication, inspection for lice detection, intervention level, and biosecurity of purchased sheep. The costs and benefits of these management options were calculated on the basis of published data or standard industry costs. Combinations of eradication achieved through treatment and biosecurity of purchased sheep provided the greatest modelled reductions in Australian flock lice prevalence at the lowest cost. With current management practices, lice prevalence was estimated as 16.3% of Australian properties infested and lice costs were estimated at 902 cents per sheep over 20 years. The model estimated that with appropriate management, lice prevalence could be reduced to less than 1.5% of properties infested and costs could be halved to 435 cents per sheep over 20 years. With further development, the modelling described herein offers potential guidance for Australian sheep producers in selecting the most effective and cost-efficient combination of management strategies to reduce lice infestation. [ABSTRACT FROM AUTHOR]

A model of lice management systems was used to investigate the potential benefits of improved fencing against straying sheep, used in conjunction with other management options for lice control. The impact of combined strategies was simulated over a 20-year period. Management options included in the model were: lice eradication rate, lice detection, intervention level, improved fencing to reduce straying sheep, and biosecurity of purchased sheep. The modelling found it was cost-effective to improve fences for an initial average cost of $20 000/property if the number of properties from which strays could enter was reduced by⩾40%, but for average Australian properties this represents less than 20% of the boundary replaced. In order for fencing to be a cost-effective part of lice management, the fencing must target sections of boundary fence that will provide the greatest protection from contact with neighbouring flocks. The model showed that improved biosecurity against straying sheep combined well with improved eradication rates. However, biosecurity for purchased sheep may be the most cost-effective option. [ABSTRACT FROM AUTHOR]

A model of sheep lice management incorporating different assumed levels of lice prevalence in different regions of Australia was used to determine the conditions under which it would be cost-effective to treat sheep for lice at shearing when no lice had been detected. The probability that a flock might be infested was calculated from the probability that the previous treatment had failed to eradicate lice, purchased sheepmayhave introduced lice, or lice may have entered on straying sheep. The model showed that a flock should be treated if the probability of infestation is greater than 10%. It was projected that acceptance of a risk level greater than 10% would reduce treatment of flocks where no lice were present, thus reducing treatment costs. This higher risk level, however, would increase the proportion of louse-infested flocks that remained untreated, resulting in increased direct lice costs and an increase in the regional prevalence of lice, but little overall change in costs to the sheep industry. The model indicated that treatment of sheep at lower levels of risk (less than 10%) would incur unnecessary costs due to treatment of flocks where no lice were present and would not reduce the regional prevalence of lice more effectively than a 10% intervention level. The model suggested that more accurate methods of detecting lice at shearing would allow higher levels of risk, reduce the use of treatment and hence reduce overall costs associated with managing lice, without increasing the prevalence of lice. [ABSTRACT FROM AUTHOR]

Merino sheep infested with lice (Bovicola ovis) and with 8 months' wool were hand jetted with a commercial spinosad formulation or treated with an α-cypermethrin backline product to examine the effect of long wool treatment on lice numbers and wool damage, relative to untreated controls. Mean lice numbers were reduced significantly (P < 0.05) by treatment and then remained relatively constant until shearing 20 weeks later. Treatment with either product resulted in significant improvements in mean clean and greasy wool cut, yield, staple length, both visually assessed and measured colour, and the proportion of fleeces classed into the main fleece line. There was no significant difference between the two treatments in either efficacy in reducing louse numbers or on production characters. Wool rub score and cotting assessed on the sheep increased slightly after treatment and then did not change until shearing whereas both scores increased significantly in the untreated group. There was a strong relationship between the visual rub score and the loss of wool at shearing, indicating that rub score can be a good predictor of lice-induced reduction in fleece weights. [ABSTRACT FROM AUTHOR]

A deterministic model for predicting the prevalence of lice in sheep flocks was compared with a stochastic model. The stochastic model was based on data from 100 000 simulated farms and encompassed: a range of lice detection levels at shearing, whether or not treatment was applied where no lice were detected, the efficacy of treatments used, and the adequacy of quarantine measures against entering sheep. The deterministic model generated more extreme estimates of the effects of lice management changes, and was judged unsatisfactory for long-term decision making. Predictions based on the stochastic model were consistent with reported survey values, suggesting the stochastic model could be used to predict benefits and costs associated with changes in louse-control methods. According to the stochastic model, the two factors that could provide the greatest reduction in dollar costs were improvement of quarantine by limiting the incidence of lice entering the flock, and improvement of eradication methods. The deterministic model suggested that there would be large benefits from improvement in detection, but the stochastic model only found small dollar benefits with improved detection in the absence of changes such as more effective treatments. Changing the proportion of flocks that were treated when no lice were detected had little effect on the predicted incidence of lousy flocks. [ABSTRACT FROM AUTHOR]

The heterodimeric ligand-binding region of the Bovicola ovis ecdysone receptor has been crystallized either in the presence of an ecdysteroid or a synthetic methylene lactam insecticide. Two X-ray crystallographic structures, determined at 2.7 Å resolution, show that the ligand-binding domains of both subunits of this receptor, like those of other nuclear receptors, can display significant conformational flexibility. Thermal melt experiments show that while ponasterone A stabilizes the higher order structure of the heterodimer in solution, the methylene lactam destabilizes it. The conformations of the EcR and USP subunits observed in the structure crystallized in the presence of the methylene lactam have not been seen previously in any ecdysone receptor structure and represent a new level of conformational flexibility for these important receptors. Interestingly, the new USP conformation presents an open, unoccupied ligand-binding pocket. [ABSTRACT FROM AUTHOR]

The purpose of the present study was based on assessments of the antiparasitic activities of synthesized titanium dioxide nanoparticles (TiO NPs) utilizing leaf aqueous extract of Catharanthus roseus against the adults of hematophagous fly, Hippobosca maculata Leach (Diptera: Hippoboscidae), and sheep-biting louse, Bovicola ovis Schrank (Phthiraptera: Trichodectidae). The synthesized TiO NPs were analyzed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The formation of the TiO NPs synthesized from the XRD spectrum compared with the standard confirmed spectrum of titanium particles formed in the present experiments were in the form of nanocrystals, as evidenced by the peaks at 2 θ values of 27.43°, 36.03°, and 54.32°. The FTIR spectra of TiO NPs exhibited prominent peaks at 714 (Ti-O-O bond), 1,076 (C-N stretch aliphatic amines), 1,172 (C-O stretching vibrations in alcoholic groups), 1,642 (N-H bend bond), and 3,426 (O-H stretching due to alcoholic group). SEM analysis of the synthesized TiO NPs clearly showed the clustered and irregular shapes, mostly aggregated and having the size of 25-110 nm. By Bragg's law and Scherrer's constant, it is proved that the mean size of synthesized TiO NPs was 65 nm. The AFM obviously depicts the formation of the rutile and anatase forms in the TiO NPs and also, the surface morphology of the particles is uneven due to the presence of some of the aggregates and individual particles. Adulticidal parasitic activity was observed in varying concentrations of aqueous leaf extract of C. roseus, TiO solution, and synthesized TiO NPs for 24 h. The maximum parasitic activity was observed in aqueous crude leaf extracts of C. roseus against the adults of H. maculata and B. ovis with LD values of 36.17 and 30.35 mg/L, and r values of 0.948 and 0.908, respectively. The highest efficacy was reported in 5 mM TiO solution against H. maculata and B. ovis (LD = 33.40 and 34.74 mg/L; r = 0.786 and 0.873), respectively, and the maximum activity was observed in the synthesized TiO NPs against H. maculata and B. ovis with LD values of LD = 7.09 and 6.56 mg/L, and r values of 0.880 and 0.913, respectively. This method is considered as an innovative alternative approach to control the hematophagous fly and sheep-biting louse. [ABSTRACT FROM AUTHOR]

Laboratory bioassays were used to measure the susceptibility of sheep lice [Bovicola ovis (Schrank)] strains that were resistant to pyrethroid or benzoylphenyl urea insect growth regulator insecticides to the organophosphate temephos, the most commonly used wet dipping insecticide. Compared with the reference susceptible strain, only the pyrethroid-resistant 'Rowena' strain displayed low level (2.2x) tolerance of temephos. Lice exposed to the minimum lethal concentration of temephos began to be affected within 6-7 h and all had responded to the insecticide within 24 h. In a dipping trial with sheep, the working concentration of temephos in a 5000-L plunge dip operating according to constant replenishment principles remained close to the nominal application rate of 350 mg/L. The ease with which temephos dip concentration was maintained simplified the dipping process. If typical of similar field populations, the absence, or low level of cross-resistance to temephos reported here for insect growth regulator-resistant and pyrethroid-resistant lice, respectively, should make wool producers confident that thorough dipping with temephos according to product label directions should be effective in controlling lice on their sheep. Temephos is the most commonly applied wet dipping product used on sheep in Australia, yet there is little information about it. Here, laboratory assays that measured the susceptibilities of louse populations to temephos are described and temephos concentration in a commercial dip is monitored during on-farm dipping. With no significant cross-resistance, wool producers should feel confident that use of temephos according to label directions should be effective. [ABSTRACT FROM AUTHOR]

In the present work, we describe inexpensive, nontoxic, unreported and simple procedure for synthesis of silver nanoparticles (Ag NPs) using leaf aqueous extract of Lawsonia inermis as eco-friendly reducing and capping agent. The aim of the present study was to assess the lousicidal activity of synthesized Ag NPs against human head louse, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), and sheep body louse, Bovicola ovis Schrank (Phthiraptera: Trichodectidae). Direct contact method was conducted to determine the potential of pediculocidal activity and impregnated method was used with slight modifications to improve practicality and efficiency of tested materials of synthesized Ag NPs against B. ovis. The synthesized Ag NPs characterized with the UV showing peak at 426 nm. X-ray diffraction (XRD) spectra clearly shows that the diffraction peaks in the pattern indexed as the silver with lattice constants. XRD analysis showed intense peaks at 2 θ values of 38.34°, 44.59°, 65.04°, and 77.77° corresponding to (111), (200), (220), and (311) Bragg's reflection based on the fcc structure of Ag NPs. Fourier transform infrared spectroscopy (FTIR) spectra of Ag NPs exhibited prominent peaks at 3,422.13, 2,924.12, 2,851.76, 1,631.41, 1,381.60, 1,087.11, and 789.55 cm. Scanning electron microscopy (SEM) micrograph showed mean size of 59.52 nm and aggregates of spherical shape Ag NPs. Energy dispersive X-ray spectroscopy (EDX) showed the complete chemical composition of the synthesized Ag NPs. In pediculocidal activity, the results showed that the optimal times for measuring percent mortality effects of synthesized Ag NPs were 26, 61, 84, and 100 at 5, 10, 15, and 20 min, respectively. The average percent mortality for synthesized Ag NPs was 33, 84, 91, and 100 at 10, 15, 20, and 35 min, respectively against B. ovis. The maximum activity was observed in the aqueous leaf extract of L. inermis, 1 mM AgNO solution, and synthesized Ag NPs against P. humanus capitis with LC values of 18.26, 7.77, and 1.33 mg l and r values of 0.863, 0.900, and 0.803 and against B. ovis showed with LC values of 21.19, 8.49, and 1.41 mg l and r values of 0.920, 0.938 and 0.870, respectively. The findings revealed that synthesized Ag NPs possess excellent anti-lousicidal activity. [ABSTRACT FROM AUTHOR]

Abstract: The in vivo pediculicidal effectiveness of 1% and 2% formulations of tea tree (Melaleuca alternifolia) oil (TTO) against sheep chewing lice (Bovicola ovis) was tested in two pen studies. Immersion dipping of sheep shorn two weeks before treatment in both 1% and 2% formulations reduced lice to non detectable levels. No lice were found on any of the treated sheep despite careful inspection of at least 40 fleece partings per animal at 2, 6, 12 and 20 weeks after treatment. In the untreated sheep louse numbers increased from a mean (±SE) of 2.4 (±0.7) per 10cm fleece part at 2 weeks to 12.3 (±4.2) per part at 20 weeks. Treatment of sheep with 6 months wool by jetting (high pressure spraying into the fleece) reduced louse numbers by 94% in comparison to controls at two weeks after treatment with both 1% and 2% TTO formulations. At 6 and 12 weeks after treatment reductions were 94% and 91% respectively with the 1% formulation and 78% and 84% respectively with the 2% formulation. TTO treatment also appeared to reduce wool damage in infested sheep. Laboratory studies indicated that tea tree oil ‘stripped’ from solution with a progressive reduction in concentration as well as volume as more wool was dipped, indicating that reinforcement of active ingredient would be required to maintain effectiveness when large numbers of sheep are treated. The results of these studies suggest significant potential for the development of ovine lousicides incorporating TTO. [Copyright &y& Elsevier]

Abstract: Tea tree oil (TTO) from the Australian native plant Melaleuca alternifolia has wide ranging bio-active properties, including insecticidal and repellent activity against arthropods. Furthermore, composition of commercially available Australian TTO is specified under an International Organization for Standardization standard (ISO 4730), reducing the potential for variable effects often noted with botanical pesticides. The effect of TTO, meeting the ISO standard for terpinen-4-ol chemotype, was tested against sheep lice (Bovicola ovis Schrank) in a series of laboratory studies. Immersion of wool for 60s in formulations containing concentrations of 1% TTO and above caused 100% mortality of adult lice and eggs. Exposure to vapours from TTO, delivered as droplets in fumigation chambers and when applied to wool also caused high mortality in both lice and eggs. The main active component of TTO in the fumigant tests was terpinen-4-ol. Treated surface assays and tests with wool where the formulation was allowed to dry before exposure of lice indicated low persistence. These studies demonstrate that TTO is highly toxic to sheep lice and active at concentrations that suggest potential for the development of TTO-based ovine lousicides. [Copyright &y& Elsevier]

October 20118February2012accepted 8 February 2012 CSIRO 2012 In response to suggestions that the incidence of louse infestations in New South Wales has increased markedly, a survey of 173 producers was conducted in the Tablelands Livestock Health and Pest Authority region using visual detection and a questionnaire to document retrospective lice history. An estimated apparent prevalence of 16.5% is a moderate increase from the 10% reported in 2004. On a subset of the surveyed sheep flocks sheep, lice-specific immunoassay conducted by the New South Wales Department of Primary Industries were used to detect low levels of infestation that were not identified by visual detection. This provided a true prevalence estimate of 30%. These results will be used to promote improved control and preventative strategies. Lice are an economically important parasite of sheep yet there is widespread speculation regarding the incidence of lice in central and southern New South Wales flocks. A survey that included visual and diagnostic inspection of sheep suggests lice infestations may have increased moderately since 2004. Producer education about the extent of the problem will facilitate improved regional control and preventative strategies. [ABSTRACT FROM AUTHOR]

Abstract: A retrospective study in which the 18years treatment history of a mob of sheep hosting a pyrethroid resistant strain of sheep body lice was compared with the coincidental changes in that strain''s response to cypermethrin, provided a unique opportunity to investigate the stability of pyrethroid resistance in this species. Resistance levels remained very high (resistance factors (RF)=75–145) for at least five years following the cessation of pyrethroid treatments but within ten years had dropped to only 5, a level similar to many normal field strains and certainly not indicative of high-level resistance. Resumption of pyrethroid treatment of sheep infested with these lice caused a coincidental increase in resistance to an extreme level (RF=321) within two years. Wool producers considering a return to pyrethroid use to control louse infestations should be aware that such a strategy may not be sustainable in the long term and that in Australia effective registered alternative treatments are available. [Copyright &y& Elsevier]

Abstract: Control of sheep lice with conventional pesticides can be compromised by difficulty in contacting lice in the dense water repellent fleeces of sheep, particularly when sheep have not been recently shorn. Entomopathogenic nematodes (ENs) are motile and are able to actively seek out insect hosts. They have particular advantages for the control of pests in cryptic habitats, such as the fleeces of sheep and avoid many of the problems frequently associated with chemical controls. This study investigated whether ENs were able infect and kill Bovicola ovis and compared the effectiveness of different species at different temperatures and when applied to wool. Four species of nematodes, Steinernema carpocapsae, Steinernema riobrave, Steinernema feltiae and Heterorhabditis bacteriophora were tested. All were shown to infect and kill lice in Petri dish assays at 30°C. At 35°C, the percent infection for S. carpocapsae and S. riobrave was significantly higher than for the other two species and percent infection by S. feltiae was significantly greater than for H. bacteriophora (P <0.05). At 37°C the percent mortality induced by S. riobrave was significantly greater than for S. carpocapsae (P <0.05). All species were able to locate and infect lice in wool when formulated in water with 8% Tween 80. In wool assays the percent lice infected with nematodes was significantly greater for S. riobrave than H. bacteriophora at 25°C, but there were no other differences between species (P =0.05). S. carpocapsae, S. riobrave and S. feltiae caused significantly higher lice mortality than H. bacteriophora at both 25 and 35°C in wool assays, but mortality induced by the three steinernematid species did not differ significantly (P >0.05). It is concluded that of the ENs studied S. riobrave is likely to be most effective against B. ovis when applied to live sheep because of its greater tolerance to high temperatures and ‘cruiser’ foraging strategy. [Copyright &y& Elsevier]

Abstract: Infestation of sheep with the louse Bovicola ovis is common worldwide and leads to an allergic dermatitis referred to as ‘scatter cockle’. IgE from an infested lamb was used in immunoaffinity chromatography to purify allergens from crude preparations of whole B. ovis and its faeces. SDS–PAGE of the affinity-purified eluates from both preparations showed a dominant band with Mr of 28.5kDa. Spleen cells from a mouse immunised with B. ovis faecal antigens were used to produce hybridomas which were screened by ELISA to identify those producing monoclonal antibodies (mAb) to the allergens purified by IgE immunoaffinity chromatography. Western blotting demonstrated that all of the mAbs examined recognised the 28.5kDa allergen. The allergen, purified using immunoaffinity columns constructed with one of the specific mAbs, was shown to cause immediate and late-phase responses on intradermal skin testing in B. ovis-infested but not in naïve lambs. Levels of serum IgE specific for the purified allergen were significantly higher in infested than in naïve lambs (P ⩽0.0025). N-terminal and internal amino acid (aa) sequences obtained from the purified 28.5kDa allergen were used to design primers to amplify a partial cDNA probe from B. ovis cDNA by PCR. The amplified probe was radiolabeled and used to screen a B. ovis cDNA library. The complete nucleotide sequence of the allergen was determined from the sequences of the positive clones from the library. The full-length cDNA encodes a 255aa protein including a secretory leader sequence of 26aas and a mature protein of 229aas. The encoded protein showed strong homology to several hypothetical proteins of unknown function from diverse species and weak homology with lipid-binding proteins of Xenopus tropicalis and Galleria mellonella. This is the first allergen to be identified from a louse and it has been designated Bov o 1 in accordance with the criteria of the World Health Organization/International Union of Immunological Societies Allergen Nomenclature Subcommittee. [Copyright &y& Elsevier]

Abstract: The present study was undertaken to investigate further the immunological responses in the skin of lambs to natural louse infestation and following intradermal allergen challenge. Bovicola ovis-infested (n =7) and naïve (n =7) Romney lambs received four intradermal injections each of crude louse Ag and diluent control solutions on the dorso-lateral chest. From each lamb, skin samples were obtained from untreated skin and, at 4, 24, 48 and 72h following injection, from one each of the Ag- and diluent-injected skin sites. Levels of acetylcholinesterase-positive Langerhans and MHC II+ cells in the epidermis as well as MHC II+, CD1b+, T19+ and IgE+ cells, eosinophils, and diffuse IgE staining in the dermis were significantly elevated in infested compared to naïve lambs (all p ≤0.01). Additionally, gene expression of interleukin-4 (IL-4), IL-5, IL-13 (all p ≤0.001) and IL-10 (p ≤0.05) was significantly higher in the skin of infested compared to naïve lambs while TNF-α and IFN-γ gene expression were not significantly different between the two groups. Intradermal injection of louse Ag led to immediate and late phase responses in the infested lambs while the naïve lambs showed only minimal responses. Levels of dermal MHC II+, CD1b+, T19+and IgE+ cells, eosinophils and diffuse IgE staining in infested lambs following injection of louse Ag were similar to or exceeded those in untreated skin and, with few exceptions, were higher than in naïve lambs. Additionally, cytokine gene expression of IL-4, IL-5, IL-13 and IL-10 increased to peak levels 4h following Ag injection in the infested lambs (p ≤0.001,≤0.05,≤0.05 and≤0.001 respectively compared to untreated controls) and remained significantly elevated compared to that observed in the naïve controls for the duration of the experiment. Significant elevations of MHC II+ cells and IL-4, IL-5, IL-13 and IL-10 gene expression were observed in the louse-naïve lambs following injection of louse Ag but were much less pronounced than in the infested lambs. These results indicated that louse infestation in lambs elicited a highly skewed Th2 immuno-inflammatory response with many characteristics similar to those seen with other parasitic infections and also in atopic dermatitis. [Copyright &y& Elsevier]

This paper describes the development of a model, based on Bayesian networks, to estimate the likelihood that sheep flocks are infested with lice at shearing and to assist farm managers or advisers to assess whether or not to apply a lousicide treatment. The risk of lice comes from three main sources: (i) lice may have been present at the previous shearing and not eradicated; (ii) lice may have been introduced with purchased sheep; and (iii) lice may have entered with strays. A Bayesian network is used to assess the probability of each of these events independently and combine them for an overall assessment. Rubbing is a common indicator of lice but there are other causes too. If rubbing has been observed, an additional Bayesian network is used to assess the probability that lice are the cause. The presence or absence of rubbing and its possible cause are combined with these networks to improve the overall risk assessment. [ABSTRACT FROM AUTHOR]

A laboratory bioassay based on the failure of eggs laid by diflubenzuron-treated sheep body lice Bovicola ovis (Schrank) (Phthiraptera; Trichodectidae) to produce nymphs is described. The test is capable of detecting benzoylphenyl urea-resistant populations. A susceptible discriminating dose (topical treatment of female lice with 0.10 μg diflubenzuron) suitable for screening suspect resistant populations is suggested but testing of further populations that are naïve to these insect growth regulator insecticides is warranted. [ABSTRACT FROM AUTHOR]

Low-volume, backline applications with the benzoylphenyl urea insecticides triflumuron and diflubenzuron represent in excess of 70% of treatments for the control of sheep lice, Bovicola ovis (Schrank) (Phthiraptera: Trichodectidae), in Australia. Reports of reduced effectiveness from 2003 and subsequent controlled treatment trials suggested the emergence of resistance to these compounds in B. ovis populations. A laboratory assay based on the measurement of moulting success in nymphs was developed and used to assess susceptibility to diflubenzuron and triflumuron in louse populations collected from sheep where a control failure had occurred. These tests confirmed the development of resistance to triflumuron and diflubenzuron in at least two instances, with estimated resistance ratios of 67–94X at LC50. [ABSTRACT FROM AUTHOR]

Results of laboratory bioassays indicated that spinosad was equally effective against sheep lice populations that were susceptible to insecticides or resistant to pyrethroid, organophosphorus or insect growth regulator (IGR) insecticides. Spinosad had similar toxicity against susceptible strains of lice to that previously reported for diazinon, but lower toxicity than cypermethrin. Lethal concentrations of spinosad and diazinon caused knock down of lice within 6 h of exposure and death within 24 h. Prior to the current phasing out of diazinon as a sheep dip, most wool producers, needing to control pyrethroid- or IGR-resistant lice infestations in short-wool, would have chosen to use diazinon. Our results suggest that spinosad is an effective alternative for treatment of lice resistant to other chemical groups. [ABSTRACT FROM AUTHOR]

Summary: Groups of louse-infested and louse-naïve lambs (n=6 or 7) were used in two experiments to determine the sequential tissue response (macroscopical, microscopical and key cytokine mRNA) to intradermal injection of crude louse (Bovicola ovis) antigen over a period of 72 or 96h. Histamine diphosphate and phosphate-buffered saline/glycerol (antigen vehicle control) solutions were also injected intradermally in each lamb for comparison. In both experiments, louse-infested lambs showed immediate and late-phase responses (LPRs) to louse antigen that differed significantly from the responses in the louse-naïve lambs. In experiment 1, biopsy samples taken at 7, 24, 48 and 96h after injections showed more extensive dermal inflammation and leucocyte infiltration in response to louse antigen in louse-infested than in louse-naïve lambs. Eosinophils were significantly more numerous in the dermis of louse-infested lambs after all treatments and increased substantially in these lambs after antigen injection. Additionally, the louse-infested lambs differed from the naïve lambs in showing significantly higher mononuclear leucocyte and basophil infiltration and significantly lower neutrophil infiltration after antigen injection. In experiment 2, biopsy samples taken 4, 24, 48 and 72h after injections showed trends in eosinophil infiltration of the dermis similar to those observed in experiment 1. Peak IL-4 mRNA expression was detected 4h after antigen injection in the louse-infested lambs and remained significantly elevated at 24h as compared with the results in the louse-naïve lambs. No significant difference in IFN-γ mRNA expression between the louse-infested and the louse-naïve lambs was observed. These results indicated that louse-infested lambs show a cutaneous LPR analogous to that observed in atopic human beings and dogs. However, some differences were observed, including the longer duration of the LPR, the profuse eosinophil infiltration, and an absence of increased IFN-γ mRNA expression. [Copyright &y& Elsevier]

Strains of sheep louse Bovicola ovis (Schrank) with various levels of resistance to pyrethroid and one strain with high degree of resistance to organophosphate (OP) insecticides were used to investigate the biochemical mechanisms of insecticide resistance, i.e., enhanced levels of general esterases, specific acetylcholinesterases (AChE), glutathione S-transferase (GST), and mixed function oxidases. Native gel electrophoresis combined with quantitative enzyme assays showed analogous expression profiles of several esterase isozymes in all the strains tested. The determination of the sensitivity of each esterase isozyme to five inhibitors (acetylthiocholine iodide, butyrylthiocholine iodide, paraoxon eserine sulfate, and pCMB) led to the identification of nine esterases in the B. ovis strain. Gel electrophoresis results are supported by enzyme assay studies where, except for the OP resistant strain, no differences in esterase activities were detected in all the pyrethroid resistant and susceptible strains assayed. Statistical analyses demonstrated that some strains have elevated GST activities compared to the susceptible reference strain. [Copyright &y& Elsevier]

The sheep biting louse (Bovicola ovis) feeds superficially on the skin of sheep but appears to stimulate an immune response. In this study we examined the association between louse infestation and serum and skin surface antibodies. Louse numbers were monitored on experimentally infested Polypay and Columbia ewes for two years and on their lambs in the second year. Serum and skin wash samples were tested for antibodies to soluble extracts of B. ovis, Stomoxys calcitrans and Musca autumnalis by enzyme linked immunosorbent assay (ELISA). In addition, the effects of skin wash extracts on B. ovis were examined in vitro. The titre of anti-B. ovis antibodies in the serum did not differ significantly between infested and naive ewes. However, there was an increase in serum antibody titre which coincided with periods of high louse density in ewes with high louse counts. Infested lambs had higher serum antibody levels than naive lambs. Substantial cross reactivity was evident among extracts of the different insects. Densities of lice on the ewes during population decline were negatively related to the titre of skin surface antibodies. Skin washings collected from sheep during B. ovis population decline reduced the number of louse progeny when incorporated into louse diet. These results indicate that B. ovis stimulates an immune response in sheep and suggest that compounds on the skin surface may play a role in the regulation of louse populations. [ABSTRACT FROM AUTHOR]