Relationship between parameters used to estimate the burden of gastrointestinal nematode infections in sheep

MALKINSKA, MARTA; FERNÁNDEZ, ALICIA SILVINA; MENZIES, PAULA; PEREGRINE, ANDREW

Jornada; Summer Leadership and Research Program; 2007

Gastrointestinal nematodes are a significant problem in sheep farming and one species in particular, Haemonchus contortus, is capable of producing anemia. An on-farm parasite control system - FAMACHA' - has been developed to aid small ruminant farmers in identifying individual animals requiring treatment. This system has been used extensively in the southern USA and South Africa; however its use under Canadian conditions needs evaluation. The objective of this study was to determine the relationship between FAMACHA scores, fecal egg counts (FEC) and packed red cell volume (PCV) in sheep farms. In April/May 2007, 23 farms in Ontario and 11 in Quebec were visited; 10 ewes and 10 lambs were sampled on every farm for blood and feces, as well as body condition and FAMACHA scores. Blood and fecal samples were used to determine PCV and FEC, respectively. Significant Spearman rank correlations were found between PCV and FAMACHA in both ewes (0.2809) and lambs (-0.4552). When agreement was measured between FAMACHA scores of 4 and 5 and a PCV threshold of less than 19%, both considered as anemic conditions, kappa was 0.386 (ewes) and -0.016 (lambs), with a sensitivity of 63.6% and 0%, and specificity of 95.3% and 99%, respectively. Based on these data the utility of FAMACHA' scoring can be questioned. However, further research in late-summer months is required to reach a concluding verdict about the method’s utility.