Evaluation of in vitro and in vivo Effectiveness of Diazinon Against Damalina ovis

An experimental randomized controlled trial were used to assess in vitro and in vivo acaricidal effect of Diazinon against sheep lice Damalinia ovis on sheep kept under semi-intensive production system, in sheep farm of Adama University School of Agriculture, Asella campus, from November, 2011 to January, 2012. Thirty naturally infested sheep with D. ovis were purposely selected for the in-vivo test according to the inclusion criteria for the study and were randomly allocated in to treatment and control group. Each selected animal were visually examined for lice infestation and lice from individual animal were counted in 24 hrs before Diazinon was applied. One hundred twenty live and motile D. ovis were manually collected for the in vitro test from the sheep that had been selected for the in vivo test and were immediately taken to the laboratory. The lice were then allocated to treatment and control group (60 lice for each group). The result of the present study showed that the in vitro and in vivo efficacy of diazinon to be 100%. There was a significant variation in percentage mortality of lice between diazinon treated and untreated group throughout the study period (P< 0.001). Sex and body condition of animals do not have significant effect (P>0.05) on the effectiveness of the tested acaricide. However, there was statistically significant variation in mean lice burden between animals with short and animals with long wool (P<0.05) post exposure up to the second round insecticide spray on day 14. Finally, Diazinon was demonstrated to be highly effective against sheep lice D.ovis. Thus, sheep producers could use it at recommended dose to treat their sheep infested with this parasite.