High frequency of benzimidazole resistance alleles in trichostrongyloids from Austrian sheep flocks in an alpine transhumance management system.

BACKGROUND: Infections of small ruminants with trichostrongyloid nematodes often result in reduced productivity and may be detrimental to the host. Anthelmintic resistance (AR) against most anthelmintic drug classes is now widespread amongst the trichostrongyloids. Baseline establishment, followed by regular monitoring of the level of AR, is necessary for farmers and veterinarians to make informed decisions about parasite management. The detection of single nucleotide polymorphisms (SNPs) is a sensitive method to detect AR against benzimidazoles (BZs), one of the most widely used anthelmintic classes. Alpine transhumance constitutes a special type of pasturing of sheep from many different farms, the aim of this study was to investigate the prevalence of benzimidazole resistance alleles in this particular management system. RESULTS: Sixteen sheep flocks in Styria and Salzburg in Austria were examined by pyrosequencing for SNPs at codons 167, 198 and 200 of the isotype-1 ß-tubulin gene. The frequency of the resistance-associated exchange F200Y was 87-100% for H. contortus, 77-100% for T. colubriformis and <  5-66% for T. circumcincta. Additionally, the F167Y polymorphism was detected in T. colubriformis from two farms at a frequency of 19 and 23% respectively. CONCLUSIONS: The high resistance allele frequency in H. contortus and T. colubriformis in the examined sheep population urgently calls for the development of new treatment strategies to sustainably control trichostrongyloid infections for this kind of pasturing, since the frequent mixing of flocks during the alpine summer grazing must be considered an important risk factor for the spread of resistant nematodes to a large number of farms.

Sequence polymorphisms in a Theileria annulata surface protein (TaSP) known to augment the immunity induced by live attenuated cell line vaccine.

Theileria annulata is a tick-borne protozoan causing tropical theileriosis in cattle. The use of attenuated cell line vaccines in combination with subunit vaccines has been relatively successful as a control method, as exemplified by a recent study in which immunization with a local cell line followed by booster vaccinations with recombinant T. annulata surface protein (TaSP) resulted in 100% protection upon field challenge in Sudan. However, these findings cannot be directly extrapolated to other countries as culture-attenuated live vaccines are generated using local strains and no systematic evaluation of genotype differences between countries has been undertaken. In this study, we sequenced the TaSP gene from T. annulata cell lines and field isolates from Tunisia (n = 28) and compared them to genotypes from Sudan (n = 25) and Morocco (n = 1; AJ316259.1). Our analyses revealed 20 unique TaSP genotypes in the Tunisian samples, which were all novel but similar to genotypes found in Asia. The impact of these polymorphisms on the ability of the TaSP antigen to boost the immunity engendered by live cell line vaccines, especially in Tunisia where studies with TaSP have not been conducted, remains to be examined. Interestingly, phylogenetic analyses of publicly available TaSP sequences resolved the sequences into two clusters with no correlation to the geographical origin of the isolates. The availability of candidate vaccines that were recently attenuated using local strains from Sudan, Tunisia, Egypt and Morocco should be exploited to generate a comprehensive catalogue of genetic variation across this regional collection of attenuated live vaccines.