Comparative immunoprophylactic efficacy of Haemonchus contortus recombinant enolase (rHcENO) and Con A purified native glycoproteins in sheep.

Haemonchus contortus is the most economically important blood feeding nematode parasite of sheep and goats all over the world. Enolase in helminth parasites is a multi-functional enzyme which involves in glycolysis and host tissue invasion. In this study, the recombinant H. contortus enolase (rHcENO) was evaluated for its immunoprophylactic efficacy in sheep along with Con A purified native glycoproteins in a vaccine challenge trial. Group I and Group II experimental sheep were immunized thrice with rHcENO and Con A purified native glycoproteins along with Montanide ISA 61 VG adjuvant. The animals were challenged with 5000 L3 stage active H. contortus larvae after 21 days of third immunization. A significant increase in the IgG titre was observed in rHcENO and Con A purified native glycoproteins immunized animals as compared to the control animals. Immunoprotective efficacy of Con A purified native glycoproteins was comparatively higher than rHcENO antigen.

Genotyping of benzimidazole resistant and susceptible isolates of Haemonchus contortus from sheep by allele specific PCR.

Extensive and indiscriminate use of the benzimidazole class of drugs has led to the onset of anthelmintic resistance. In tropical countries like India, Haemonchus contortus is the most pathogenic parasite infecting sheep and goats. The widespread presence of resistant helminths (especially H. contortus) threatens the livestock farming. The use of various drugs has led to single nucleotide polymorphism that causes specific amino acid substitutions in ß-tubulin protein of H. contortus to confer resistance. This emphasizes the need for a survey on the present status of resistance in India. In this study, allele specific PCR was employed to screen the presence of a SNP, a thymine-to-adenine transversion which leads to substitution of amino acid in codon 200 of ß-tubulin gene that is correlated specifically with BZ resistance. Third stage larvae (L3) from pooled faecal cultures of four organized sheep farms served as a source of genomic DNA for identification of H. contortus and further genotype analysis. A total of 1000 larvae was screened, out of which 673 larvae were identified as H. contortus. Among 673 H. contortus larvae, 539 larvae (80 %) were genotyped as homozygous resistant (rr) and remaining 134 (20 %) were heterozygous susceptible (Sr) by allele specific PCR. The concluded resistance status reasons out the failure of anthelmintic drug in treating ruminants. Immediate steps are needed to avoid further aggravation of the problem. Target selective treatment by reviewing the resistance status of individual drugs, appropriate use of anthelmintic drugs and other control strategies will provide a pragmatic option for delaying the further spread of anthelmintic resistance.