Abstract
While Texel lambs have increased resistance to infection with the gastrointestinal nematode Teladorsagia circumcincta compared to Suffolk lambs, the underlying resistance mechanisms are still unknown. The aim of this study was to compare parasitological, humoral and cellular responses of Texel and Suffolk lambs over time following a single experimental infection with T. circumcincta. Gastrointestinal nematode free (but not naïve) lambs received a single oral dose of 3 × 104 infective T. circumcincta larvae. The variables examined included worm burden, mucosal and serum IgA, abomasal mast cells and eosinophils, haematological parameters and plasma pepsinogen. Texel lambs had significantly lower worm burden on day 14 and lower plasma pepsinogen concentration from day 14 onwards than Suffolks and their response in mucosal IgA to infection occurred earlier. The results from the study suggest that an earlier local IgA response in the Texel contributes to the resistant characteristics of the breed, while the increased level of plasma pepsinogen in the Suffolk lambs implies greater abomasal tissue damage arising from the nematode infection.
Highlights
Teladorsagia circumcincta is among the most important gastrointestinal nematode (GIN) species affecting sheep production in temperate regions [1,2]
The breed effect was significant for platelets (Texel > Suffolk; P < 0.001), mean corpuscular volume (MCV) (Texel > Suffolk; P < 0.001) and red blood cells (RBC) (Suffolk > Texel; P < 0.001). To our knowledge this is the first comparison of the response of Suffolk and Texel lambs to an experimental challenge with T. circumcincta
The significant breed difference in worm burden 14 days after artificial infection is consistent with previous observations in this flock on lambs exposed to a natural challenge [6,24]
Summary
Teladorsagia circumcincta is among the most important gastrointestinal nematode (GIN) species affecting sheep production in temperate regions [1,2]. Extensive use of anthelmintics as a control strategy has resulted in the evolution of anthelmintic resistance in various nematode species [5]. This together with consumer concern over drug residues in animal products has promoted interest in the development of alternative methods of GIN control, such as genetic selection for increased host resistance to GIN. A number of studies have already identified established breeds that are relatively resistant to various GIN species [6,7,8,9]. In Ireland, Ahmed et al Veterinary Research (2015) 46:8 parasite specific factors (variability in species composition, fecundity, developmental stage), environmental factors (nutrition, climate), sampling accuracy and precision [16,17,18,19,20,21]
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