Is trypanocidal drug resistance a threat for livestock health and production in endemic areas? Food for thoughts from Sahelian goats infected by Trypanosoma vivax in Bobo Dioulasso (Burkina Faso)

Abstract

Trypanocidal drug resistance is unanimously recognized as a threat for livestock production in regions where the prevalence of trypanosomosis is high. To assess the impact of the disease and the effect of drug resistance on the health of small ruminants, twelve Trypanosoma vivax isolates collected in 6 villages in the vicinity of Bobo Dioulasso (Burkina Faso) were injected into 12 groups of 5 Sahelian goats, two being treated with 3.5mg/kg body weight diminazene aceturate (DA), two with 0.5mg/kg body weight isometamidium chloride (ISM) and one left untreated as control. A monitoring was performed every 5days for 100days to evaluate the parasitaemia by buffy coat examination, the hematocrit and the body weight. Among the 12 groups, 6 were additionally monitored using a trypanosome specific 18S-PCR–RFLP every 5days from day 30 to day 100 to verify the complete clearance of the parasites from the blood of the hosts. In six groups of goats, trypanosomes disappeared completely after treatment, five groups showed relapses in at least one goat treated with ISM and one group showed relapses in one goat treated with DA and one with ISM. For the 6 groups that were screened both using microscopic examination and trypanosome specific 18S-PCR–RFLP, the following results were observed: for the groups treated with DA, no relapses by microscopic examination and 83.3% (10/12) using the 18S-PCR–RFLP. For the groups treated with ISM, 25% (3/12) relapses by microscopic examination and 83.3% with the 18S-PCR–RFLP (10/12). The evolution of the PCV and the weight during the observation period from relapsing (either by microscopical examination or by 18S-PCR–RFLP diagnosis) and non relapsing animals were compared. The relative average PCV in goats that relapsed microscopically, decreased significantly more than in non-relapsing goats. This difference was not significant when relapses were detected using the trypanosome specific 18S-PCR–RFLP. This indicates that only the animals with the highest parasitaemia suffered from the infection. Relapses after treatment where the host controls the parasitaemia to a level below the sensitivity of the microscopical examination do not affect body weight nor PCV.