The objective of this study was to evaluate the therapeutic efficacy of
paromomycin against
cryptosporidiosis in naturally infected lambs under field conditions. The 36 cross-bred neonatal lambs, 3-10 days old, were used. On the first day that lambs showed
diarrhea (Day 1) they were randomly divided into three groups. The infected control group (14 lambs) remained unmedicated whereas the two other groups were orally medicated with
paromomycin solution (
Humatin((R)), Parke Davis, France): 12 lambs (Group A) at 100mg/kg per day for three consecutive days (Days 1-3) and 10 lambs (Group B) at 200mg/kg per day for two days (Days 1 and 2).
Drug efficacy was assessed by evaluating the presence of
diarrhea, oocyst shedding and
weight gains from Days 1 to 23. The results show the efficacy of
paromomycin in reducing both cryptosporidial oocyst output and severity of clinical signs. On Day 4, all unmedicated lambs remained infected and excreted large numbers of cryptosporidial oocysts (mean score: 2.5) whereas oocyst output had stopped in most medicated lambs (>60%) and low numbers of oocysts were excreted in the remaining lambs (mean score: 0.45 in Group A and 1 in Group B). Mean oocyst excretion was significantly reduced in medicated lambs from Days 2 to 5 (P<0.05). Treatment also reduced, but not completely prevented, clinical symptoms although
diarrhea stopped in most medicated lambs just after
drug withdrawal. The mean
weight gains of Group A lambs were higher than that of unmedicated lambs throughout the study and statistically significant differences were found from Days 1 to 11 (1.99+/-0.81 versus 1.47+/-0.53) (P<0.05). By contrast, the growth rate of Group B lambs from Days 11 to 23 was impaired when compared with the two other groups (P<0.05) although no significant differences were found at the end of the study (Days 1-23).