Correlates of resistance to gastrointestinal nematode infection in Nigerian West African dwarf sheep

摘要

ABSTRACT Objective:To investigate correlates of resistance toGI nematode infection inNigerianWest African dwarf(WAD) sheep.Methods:Thirty three sheep were randomly assigned to two groups, A(n=27) which were used for experimental infections, andB(n=6) which served as uninfected control.Each infected animal received weekly escalating infections with infective larvae(60%Haemonchus contortus (H. contortus) and40%Trichostrongylus colubriformis (T. colubriformis) for4 weeks.The responses of all the infected and control sheep were assessed by faecal egg count(FEC), worm burden(Wb), packed cell volume(PCV), body weight(Bwt), and body condition score(BCS).On the basis of their individual faecal egg output,Lambs in groupA with epg≤1 000 on any sampling day were classified as low faecal egg count(LFEC) phenotype(n =16), those with epg between1000 and10000 as intermediate(n=5) and lambs with epg >10000 as high feacal egg count(HFEC) phenotype(n=6).Results:The difference between theFEC classes was highly significant(P=0.001).TheBCS and weight gained at the end of the experiment by the control andLFEC sheep was significantly higher(P≤0.05) than those of the intermediate and HFEC phenotypes.There was a significant and negative correlation between the parasitological measures and the trio ofBCS,PCV andBwt of sheep.Conclusions:The result of the study indicated that theFEC, weight gain,PCV, andBCS are correlates and potential selection criteria ofGI nematode resistantWAD sheep.