Field trial on the therapeutic efficacy of paromomycin on natural Cryptosporidium parvum infections in lambs

The objective of this study was to evaluate the therapeutic efficacy of par omomycin 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 unmedica ted whereas the two other groups were orally medicated with paromomycin sol ution (Humatin(R), Parke Davis, France): 12 lambs (Group A) at 100 mg/kg pe r day for three consecutive days (Days 1-3) and 10 lambs (Group B) at 200 m g/kg per day for two days (Days 1 and 2). Drug efficacy was assessed by eva luating the presence of diarrhea, oocyst shedding and weight gains from Day s 1 to 23. The results show the efficacy of paromomycin in reducing both cr yptosporidial oocyst output and severity of clinical signs. On Day 4, all u nmedicated lambs remained infected and excreted large numbers of cryptospor idial oocysts (mean score: 2.5) whereas oocyst output had stopped in most m edicated lambs (>60%) and low numbers of oocysts were excreted in the remai ning lambs (mean score: 0.45 in Group A and 1 in Group B). Mean oocyst excr etion 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 withdrawa l. The mean weight gains of Group A lambs were higher than that of unmedica ted lambs throughout the study and statistically significant differences we re found from Days 1 to 11 (1.99+/-0.81 versus 1.47+/-0.53) (P<0.05). By co ntrast, the growth rate of Group B lambs from Days 11 to 23 was impaired wh en compared with the two other groups (P<0.05) although no significant diff erences were found at the end of the study (Days 1-23). (C) 2000 Elsevier S cience B.V. All rights reserved.