Repeatability of faecal egg-count and haematological values in sheep experimentally infected with Haemonchus contortus

Avivastra lambs (12) were experimentally infected twice with 10 000 infecti ve larvae of Haemonchus contortus at 7-week interval. Another 6 lambs of sa me breed served as infectivity control and 4 lambs were healthy contra is. The mean faecal egg count peaked 6-7 weeks after both the infections. The m ean packed-cell volume decreased significantly from week 3 while, mean haem oglobin and total erythrocyte count dropped from week 5 onward. The repeata bility of mean faecal egg count, haemoglobin, packed-cell volume, mean corp uscular haemoglobin concentration and body weight for each animal between 2 infections were 0.4958, 0.4899, 0.5509, 0.6098 and 0.9410 respectively. Wo rn; burden and faecal egg count were negatively correlated with haemoglobin , packed-cell volume, total erythrocyte count and body weight. Multiple reg ression analysis revealed that 5 variables - faecal egg count, haemoglobin, packed-cell volume, total erythrocyte count and body weight together accou nted for 86% of the observed variation in worm burden among lambs. fl was c oncluded that under these controlled conditions these markers are reasonabl y appropriate for detecting the resistance status of sheep against H. conto rtus.