Authors : A.V. Rodriguez, V. Goldberg, G. Ciappesoni and P.A. Cabrera
Abstract: Haemonchus contortus is a blood-sucking parasite causing the presence of Faecal Occult Blood (FOB). The objective was to study three different FOB tests in order to have a new indicator of H. contortus infection in sheep that could be included in the genetic evaluation system as an alternative selection criterion to Faecal worm Egg Count (FEC). A total of 29 Corriedale lambs were artificially infected with 10 larvae of H. contortus. Stool samples were recorded for FEC and FOB tests (Hexagon, Hematest® and Multistix®), blood for Packed Cell Volume (PCV), haemoglobin, white and Red Blood Cell count (RBC) and FAMACHA© for scoring anaemia. At the end of the experiment lambs were slaughtered to worm burden count. Field validation was achieved in 309 Merino lambs under natural parasite challenge. FEC data was normalized through logarithmic transformation (lnFEC). Pearson correlation was estimated to examine the relationship between all traits. The three tests were able to detect the presence of FOB at day +11. FEC, PCV and RBC decreased to sub-normal values since day +18. FAMACHA© score 3 was considered to be indicative of anaemia. All correlations were significantly different from zero (p<0.001). The correlations between haematological parameters with lnFEC and FAMACHA© were high as well as between lnFEC with FAMACHA© and worm burden. Multistix® test was moderately correlated with lnFEC, haematological parameters and FAMACHA©. In field validation, most samples were negative to FOB tests and the correlations were lower than those calculated under artificial infection. In conclusion, FOB tests were able to detect haemonchosis earlier than FEC under high artificial parasite challenge. However, they were not able to detect FOB under natural mixed parasite challenge. FAMACHA© and PCV demonstrated to be good indicators of Haemonchosis having moderate to high correlations with FEC.
A.V. Rodriguez, V. Goldberg, G. Ciappesoni and P.A. Cabrera, 2014. Early Detection of Haemonchus contortus Infection in Sheep Using Three Different Faecal Occult Blood Tests. Journal of Animal and Veterinary Advances, 13: 395-400.