helminth parasites and Oestrus ovis in Karakul sheep, seasonal incidence determined by slaughter of successive groups of tracer lambs each exposed on pasture for 33 days, recommended deworming programme, importance of moving sheep to new pastures immediately after deworming

Oestrosis is a worldwide myiasis infection caused by the larvae of
the fly Oestrus ovis (Diptera, Oestridae), that develops from the first to the third stage larvae. This is an obligate parasite of the nasal and sinus cavities of sheep and goats. The Oestrus ovis larvae elicit clinical signs of cavitary myiasis seen as a seromucous or purulent nasal discharge, frequent sneezing, incoordination and
dyspnea. Myiasis in an incidental host may have biological significance towards medical and public health importance if
the incidental host is man. This infection can result in signs of generalized disease, causing serious economic losses in sheep and goat reared for meat and dairy production. Due to the large numbers of small ruminants imported into Malaysia from countries which are endemic with oestrosis, precautionary measures should be exercised to prevent this infection from establishing here. In 2009, there was a report of respiratory distress (pneumonic sign) accompanied by high mortality in Damara sheep that was imported from Australia. Investigations showed the presence of Oestrus ovis larvae in affected
sheep. The post mortem was conducted in the field and the larvae were discovered in the tracheal region. The larvae was confirmed as Oestrus ovis using the appropriate keys for identification by Zumpt. The carcass showed pulmonary edema with severe congestion of the lungs accompanied by frothy exudation in the bronchus. There were also signs of serious atrophy (heart muscle) and mild enteritis
(intestine histopathological examination showed, there was pulmonary congestion and edema, centrilobular hepatic necrosis, renal tubular necrosis and myocardial sarcocystosis. The sheep also showed chronic helminthiasis and Staphylococcus spp. was isolated from organ specimens.Oestus ovis infection is rare in Malaysia, as such this case posed as an unusual case for investigation.