Assessment of acquired resistance in previously infected lambs with gastrointestinal nematodes in a tropical climate

The aim of this study was to determine the parasitological traits and productive response in Pelibuey lambs re-infected with gastrointestinal nematodes (GIN) previously infected with different doses of infective larvae (L3). One infection with 60% Haemonchus contortus and 40% Cooperia curticei larvae was induced in three groups of six lambs using oral doses of 100, 200 and 300 L3 per kg of body weight (BW), respectively. Nine weeks post-infection all lambs were treated with albendazole (ABZ). A second parasitic infection was induced using 300 L3 per BW followed for six weeks of parasitological sampled and four lambs of each treatment were slaughtered after this period to count adult nematodes. Results showed reduction of eggs per gram of faeces (EPG) between first (2463±4400 EPG) to second infection (327±66 EPG) for pre-infected lambs with 300 L3. Through first infection, the packed cell volume (PCV) decreased until 35 days post-infection (32.0% to 26.0%) for all groups. In conclusion Pelibuey lambs infected with 300 L3 showed low re-infection to contribute in the reduction of parasitic traits under tropical climate.