Défense de thèse de doctorat en médecine vétérinaire "gastrointestinal parasite infections"

Epidemiology and control of gastrointestinal parasite infections in wool sheep adapted to tropical Andes high altitude conditions

Jury

Pierre DORNY (Inst. médecine tropicale, Anvers), Martin GANTER (TIHO, Hannover), Bernard LOSSON (ULg), Jean-François BECKERS (ULg), Claude SAEGERMAN (ULg), Benoît MUYLKENS, président (UNamur), Tanguy MARCOTTY (UNamur), Marianne RAES (UNamur), Nathalie KIRSCHVINK, promoteur (UNamur)

Résumé

High susceptibility of sheep to gastrointestinal parasites has been described as a constraint that contributes to reduce sustainability of commercial farms worldwide. The increasing problems with internal parasites at Andean sheep flocks are based largely on anecdotal evidence, such as farmers’ impressions and from particular reports of clinical outbreaks. The objective of this study was to describe the dynamic of sheep gastrointestinal parasites and the interaction with their hosts within specific conditions of tropical Andes high altitude conditions, in order to recommend rational and sustainable practices of control.  Fecal samples collected in adult sheep demonstrated that fluctuation in nematode eggs elimination was related to adult ewes` physiological status. Pregnant and lactating ewes were highly susceptible to strongylids nematodes. In lambs, it was demonstrated the high susceptibility to Eimeria and Strongyloides papillosus infections early after lambing and the subsequently gradual increase in strongylids eggs near to weaning. Thus, strategic treatment at these points during sheep productive life could be beneficial. Creole breed showed the lowest fecal egg counts in all animal categories; however, significant differences between breeds were only detected in adult sheep.  Fecal egg count reduction tests (FECRT) were performed in lambs and lactating ewes with the most employed anthelmintic molecules in Colombia. Fecal egg count reduction tests demonstrated that levamisol and moxidectin were effective against gastrointestinal nematodes in contrast to fenbendazole and ivermectin which had moderate and insufficient activities respectively. As periparturient ewes were the most susceptible adult category to gastrointestinal nematodes and the main source of nematode eggs for pasture contamination, it was demonstrated that strategic periparturient anthelmintic treatment prevents peaks in nematode eggs excretion during lactation. In conclusion, the present study described a pattern of gastrointestinal nematode infection that could be employed for the development of rational advices which can be used by farmers to manage in a better way the nematode parasite infections at Andean sheep flocks in Colombia.

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