New insights into the use of a mite count reduction test for the detection of therapeutic acaricide efficacy in Psoroptes ovis in cattle

When used for the evaluation of drug efficacy against Psoroptes ovis, the diagnostic performance of different sampling strategies for a mite count reduction test (MCRT) remains unclear. In the present study, a novel simulation framework was constructed that accounted for relevant biological features of P. ovis infestations in cattle and that was parameterized with field data from 16 farms (154 animals). Second, this framework was applied to explore the impact of study specific factors (number of animals, number of sampled lesions, and number of scrapings per lesion) and biological factors (mite infestation intensity and size of lesions) on the diagnostic performance of MCRT. Its outcome provided a basis to determine the diagnostic performance of MCRT when it was applied according to the World Association for the Advancement in Veterinary Parasitology (WAAVP) and the European Medicine Agency (EMA) guidelines, and to formulate recommendations to ensure a good diagnostic performance of the MCRT. For both guidelines, the MCRT allowed to correctly detect (power 80%) reduced and normal efficacy when the therapeutic efficacy was 95%, respectively. The results highlighted a reliable diagnostic performance of the MCRT when performed as recommended by WAAVP and EMA for the detection of normal drug efficacy. When used for the detection of reduced efficacy, therapeutic efficacies between 70% and 90% could not be detected with sufficient reliability. The diagnostic performance can be improved by increasing the total number of skin scrapings (increasing the number of animals, number of sampled lesions and/or number of samples per lesion). In order to help researchers and veterinarians to optimize the design of the MCRT to their field settings, the findings were translated into a simple tool

Comparative analysis of the immune responses induced by native versus recombinant versions of the ASP-based vaccine against the bovine intestinal parasite Cooperia oncophora

The protective capacities of a native double-domain activation-associated secreted protein (ndd-ASP)-based vaccine against the cattle intestinal nematode Cooperia oncophora has previously been demonstrated. However, protection analysis upon vaccination with a recombinantly produced antigen has never been performed. Therefore, the aim of the current study was to test the protective potential of a Pichia-produced double-domain ASP (pdd-ASP)-based vaccine against C. oncophora. Additionally, we aimed to compare the cellular and humoral mechanisms underlying the vaccine-induced responses by the native (ndd-ASP) and recombinant vaccines. Immunisation of cattle with the native C. oncophora vaccine conferred significant levels of protection after an experimental challenge infection, whereas the recombinant vaccine did not. Moreover, vaccination with ndd-ASP resulted in a higher proliferation of CD4-T cells both systemically and in the small intestinal mucosa when compared with animals vaccinated with the recombinant antigen. In terms of humoral response, although both native and recombinant vaccines induced similar levels of antibodies, animals vaccinated with the native vaccine were able to raise antibodies with greater specificity towards ndd-ASP in comparison with antibodies raised by vaccination with the recombinant vaccine, suggesting a differential immune recognition towards the ndd-ASP and pdd-ASP. Finally, the observation that animals displaying antibodies with higher percentages of recognition towards ndd-ASP also exhibited the lowest egg counts suggests a potential relationship between antibody specificity and protection

Multiplexed-tandem PCR for the specific diagnosis of gastrointestinal nematode infections in sheep : an European validation study

Background: Traditional methods of detecting and identifying gastrointestinal nematode infections in small ruminants, including sheep and goats, are time-consuming and lack in sensitivity and specificity. Recently, we developed an automated multiplexed-tandem (MT)-PCR platform for the diagnosis and identification patent infections with key genera/species of gastrointestinal nematodes of sheep and validated this approach in detailed experiments carried out in Australia. In the present study, we deployed this diagnostic platform in Scotland and Belgium to test samples from naturally infected sheep in these environments and to validate the MT-PCR platform relative to traditional diagnostic methods routinely used by local laboratories. Results: MT-PCR detected all microscopy positive samples and there was a significant agreement between the results of the different test methods in terms of the species detected and their relative proportion in a test sample, however, for some samples, there were discrepancies between the results of the different test methods. Selective sequencing of purified MT-PCR products demonstrated the results to be 100% specific. Conclusions: The MT-PCR platform is an advanced method for the species/genus-specific diagnosis of gastrointestinal nematode infections in small ruminants and has demonstrated utility when deployed in different countries and climatic zones. The platform is user-friendly due to the largely automated procedure and has high versatility in that it can achieve a specific diagnosis from different types of sample templates, including larval culture and faecal samples. With appropriate modifications of the primers used, the MT-PCR platform also provides potential for the diagnosis of a variety of other pathogens of veterinary or medical importance

Evaluatie van twee intensieve behandelingsschema's tegen Psoroptes ovis-schurft bij Belgisch witblauwe runderen op negen Vlaamse rundveebedrijven

Psoroptic mange, caused by Psoroptes ovis, is a problem on many Flemish farms where Belgian blue beef cattle are bred. Two intensive treatment schedules were evaluated on nine Belgian blue fauns with a-persistent mange problem. On farms 1 to 7, all animals were treated twice (with a seven-to-ten-days interval) with an injectable macrocyclic lactone (ML), while on the two remaining fauns, the initial treatment consisted of one injection with the long acting (LA) formulation of moxidectin (10%). Skin scrapings were taken after treatment, and when living mites were found on at least one animal, all animals (farms 1 to 7) or only positive animals (farms 8 and 9) were treated consecutively with an injectable ML. On all farms, the treated animals were clinically healthy and P ovis free at the end of winter, after two to nine treatment rounds (two injections with a seven to ten-days interval or one LA injection). Although mange reappeared on the first seven farms after the subsequent grazing season, the disease was less severe and easier to control

Abundance, zoonotic potential and risk factors of intestinal parasitism amongst dog and cat populations: The scenario of Crete, Greece

Background: The objectives of this study were to evaluate the prevalence and infection intensity of intestinal parasites in different dog and cat populations in Crete, Greece, estimate the zoonotic risk and identify risk factors. Methods: Faecal samples from shelter, household and shepherd dogs and shelter and household cats were analyzed using sedimentation/flotation techniques. Giardia and Cryptosporidium were detected by a quantitative direct immunofluorescence assay (IFA). PCR and sequencing was performed to evaluate the zoonotic potential of Giardia and Cryptosporidium positive samples. Results: Totals of 879 dog and 264 cat faecal samples were examined. In dogs, the overall prevalence was 25.2% (CI: 22.4-28.1) for Giardia spp.; 9.2% (CI: 7.3-11.1) for Ancylostoma/Uncinaria spp.; 7.6% (CI: 5.9-9.4) for Toxocara spp.; 5.9% (CI: 4.4-7.5) for Cryptosporidium spp.; 4.6% (CI: 3.2-5.9) for Cystoisospora spp.; 2.7% (CI: 1.7-3.8) for Toxascaris leonina; 1.7% (CI: 0.9-2.6) for Capillaria spp.; 0.8% (CI: 0.2-1.4) for taeniid eggs; 0.2% (CI: 0-0.5) for Dipylidium caninum; and 0.1% (CI: 0-0.3) for Strongyloides stercoralis. In cats, the prevalence was 20.5% (CI: 15.6-25.3) for Giardia spp.; 9.5% (CI: 5.9-13.0) for Cystoisospora spp.; 8.3% (CI: 5.0-11.7) for Toxocara spp.; 7.6% (CI: 4.4-10.8) for Ancylostoma/Uncinaria spp.; 6.8% (CI: 3.8-9.9) for Cryptosporidium spp.; 4.2% (CI: 1.8-6.6) for Capillaria spp.; 0.8% (CI: 0-1.8) for taeniid eggs; and 0.4% (CI: 0-1.1) for Hammondia/Toxoplasma. Concerning the risk factors evaluated, there was a negative association between age and Giardia infection and between age and T. leonina infection intensity for dogs. Sequencing results revealed the presence of mainly animal-specific G. duodenalis assemblages C and D in dogs and assemblages F, C and BIV-like in cats, with only a limited number of (co-) infections with assemblage A. As for Cryptosporidium, the dog-specific C. canis and the pig-specific C. scrofarum were detected in dogs and the cat-specific C. felis was detected in cats. Conclusions: High levels of parasitism in both dogs and cats were recorded. Giardia was the most prevalent parasite in all dog and cat populations except for shepherd dogs. Genotyping results suggest a limited zoonotic risk of Giardia and Cryptosporidium infections from dogs and cats in Crete. Taeniid eggs were more prevalent in shepherd dogs suggesting access to carcasses and posing a threat for cystic echinococcosis transmission. Infection rates of Toxocara spp. in both dogs and cats show that companion animals could be a significant source of infection to humans

Resistance against macrocyclic lactones in Psoroptes ovis in cattle

Background Psoroptic mange is an important disease in Belgian Blue cattle. Treatment failure of macrocyclic lactones against Psoroptes ovis has been reported, but clear evidence of in vivo resistance is lacking. This study assessed the efficacy of macrocyclic lactone products on 16 beef farms in Belgium and the Netherlands in vivo and in vitro. Methods On each farm a group of animals (n = 7-14) with psoroptic mange was treated with two subcutaneous injections of a macrocyclic lactone product with 7-10 days interval (15 farms) or a single injection with a long-acting macrocyclic lactone (1 farm). In vivo efficacy was assessed by the reduction in mite counts, clinical index (proportion of the body surface affected by lesions), the proportion of the animals with negative mite counts after the first treatment round and the number of treatment rounds needed to obtain zero mites counts in all animals. A mite population was categorized as sensitive when the mite count reduction after the first treatment round > 95% and the lower limit of the uncertainty interval > 90%. Resistance was detected when both parameters were below their threshold and suspected when one parameter was too low. In vitro knockdown and mortality were evaluated in a contact test. Results The proportion of the animals with negative mite counts after the first treatment round varied from 0 to 80%. All farms needed two or more treatments rounds to obtain zero mite counts on all animals. Clinical index only started to reduce after the second treatment round. Mite populations from three farms were categorized as sensitive, one as suspected resistant and 12 as resistant. No correlation was found between in vitro lethal dose 50 and knockdown dose 50 values and in vivo efficacy parameters. Conclusions Unambiguous treatment failure was detected on 12 out of 16 farms, confirming the presence of macrocyclic lactone resistance on Belgian Blue beef farms. In vitro parameters could not discriminate the farms based on their in vivo sensitivity. The mean reduction in mite counts and the lower limit of the confidence interval are proposed as parameters to identify acaricide resistance

Dermal immune responses against Psoroptes ovis in two cattle breeds and effects of anti-inflammatory dexamethasone treatment on the development of psoroptic mange

Psoroptic mange is a common disease of livestock, caused by Psoroptes ovis. Compared to Holstein-Friesian (HF) cattle, the Belgian Blue (BB) cattle breed is highly susceptible to the infestation. However, the mechanism for this difference is still unclear. To determine the factors responsible for this breed susceptibility, the immune response to P. ovis was studied in experimentally infested BB and HF cattle, using clinical signs, histology, immunohistochemical profiling and gene expression analysis of skin biopsies. The mite numbers and lesion area of BB cattle were greater than in HF during the whole study period. Significant influxes of eosinophils in the epidermis and dermis were detected in comparison with the pre-infestation samples in both breeds, with significantly higher eosinophils in BB at 6 weeks post infestation (wpi). Mast cell numbers were unaffected at all stages of infestation in HF, but were significantly elevated relative to pre-infestation in BB cattle at 2 and 6 wpi. The more pronounced cutaneous eosinophilia and higher IL-4 levels at 6 wpi in BB cattle suggest that a Th2-type immune response is underlying the higher susceptibility of the BB breed. In naturally infested BB cattle, development of the psoroptic mange lesions and eosinophils and CD3+ T cell areas were severely depressed after anti-inflammatory treatment with dexamethasone. Together, these results suggest that a stronger Th2-type immune response to P. ovis causes the skin lesions in psoroptic mange in BB cattle and that local anti-inflammatory treatment could potentially be an alternative to control the pathology caused by this parasite