Sheep Oestrosis (Oestrus Ovis, Diptera: Oestridae) in Damara Crossbred Sheep
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VOLUMEolume 2 NOo. 2 JULY 2011 • pages 41-49 MALAYSIAN JOURNAL OF VETERINARY RESEARCH SHEEP OESTROSIS (OESTRUS OVIS, DIPTERA: OESTRIDAE) IN DAMARA CROSSBRED SHEEP GUNALAN S.1, KAMALIAH G.1, WAN S.1, ROZITA A.R.1, RUGAYAH M.1, OSMAN M.A.1, NABIJAH D.2 and SHAH A.1 1 Regional Veterinary Diagnostic Laboratory Kuantan, Jalan Sri Kemunting 2, Kuantan, Pahang 2 KTS Jengka Pusat Perkhidmatan Veterinar Jengka Corresponding author: [email protected] ABSTRACT. Oestrosis is a worldwide the field and the larvae were discovered myiasis infection caused by the larvae of in the tracheal region. The larvae was the fly Oestrus ovis (Diptera, Oestridae), confirmed as Oestrus ovis using the that develops from the first to the third appropriate keys for identification by stage larvae. This is an obligate parasite Zumpt. The carcass showed pulmonary of the nasal and sinus cavities of sheep edema with severe congestion of the lungs and goats. The Oestrus ovis larvae elicit accompanied by frothy exudation in the clinical signs of cavitary myiasis seen as bronchus. There were also signs of serious a seromucous or purulent nasal discharge, atrophy (heart muscle) and mild enteritis frequent sneezing, incoordination and (intestine histopathological examination dyspnea. Myiasis in an incidental host showed, there was pulmonary congestion may have biological significance towards and edema, centrilobular hepatic necrosis, medical and public health importance if renal tubular necrosis and myocardial the incidental host is man. This infection sarcocystosis. The sheep also showed can result in signs of generalized disease, chronic helminthiasis and Staphylococcus causing serious economic losses in spp. was isolated from organ specimens. sheep and goat reared for meat and dairy Oestus ovis infection is rare in Malaysia, production. Due to the large numbers of as such this case posed as an unusual case small ruminants imported into Malaysia for investigation. from countries which are endemic with Keywords: Oestrus ovis, Damara oestrosis, precautionary measures should sheep, larvae, respiratory sign, myiasis be exercised to prevent this infection from establishing here. In 2009, there was a INTRODUCTION report of respiratory distress (pneumonic sign) accompanied by high mortality in Larvae of flies belonging to the Oestridae Damara sheep that was imported from Family and Oestrinae Subfamily include Australia. Investigations showed the several genera which cause obligatory presence of Oestrus ovis larvae in affected myiasis in Artiodactyla and Equidae, sheep. The post mortem was conducted in infesting the nasopharyngeal cavities and 41 MALAYSIAN JOURNAL OF VETERINARY RESEARCH VOLUME 2 NO. 2 JULY 2011 internal organs during their migration. southern Europe an unusually large number Oestrosis is a regional myiasis caused by of different spesies of bot fly suggests larvae of the fly Oestrus ovis (Diptera, a high degree of oestrid biodiversity. It Oestridae), that develop from the first to seems related to the movement of domestic the third stage larva which are obligate animals in association with migrating parasites of the nasal and sinus cavities of human populations in southern Europe sheep and goats. over thousands of years (Otranto et al., The larvae are obligatory parasites of 2006). Oestrus ovis can thrive in different nasal and sinus cavities of sheep and goats environments (Horak, 1977; Breev et (Zumpt, 1965). The female are larviparous, al., 1980; Pandey and Ouhelli, 1984) and depositing a number of first-instar larvae can overwinter in a diapauses state, as on the edge, or just inside the nostrils of larvae in the sinu-nasal passages of the sheep and goats. The peculiar feature of the host (Cobbett and Mitchell, 1941; Horak, O. ovis female is that it may larviposit while 1981). The ability to adapt in a different still in flight. In their normal development environment allows the natural persistence in sheep, the larvae migrate to the nasal of infestation and the difficulties for its mucosa and nasal and frontal sinuses control. Recent surveys have demonstrated where they undergo 2 moults. After 2 to 12 the high prevalence of caprine Oestrosis in months, the fully grown third instar larvae numerous areas all over the world, 48.3% are expelled and pupate on the ground. in India (Jagannath et al., 1989), 31.3% This parasite is found worldwide and in Mexico (Martinez et al., 1992), 4 % in it is especially widespread in Mediterranean Argentina (Trezeguet, 1996) and 53.8% countries of Europe and Africa (Pandey, in Nigeria (Biu and Nwosu, 1999). So far, 1989; Dorchies et al., 2000; Alcaide et al., there is no case report of Oestrus ovis in 2003; Papadopoulos et al., 2006). Despite sheep in Malaysia, a tropical rainforest the high prevalence in these countries country where large imports of sheep and and severity of infection, many breeders goats for breeding and sheep production is and veterinary practitioners still remain carried out regularly. unaware of the importance of these parasitic The O. ovis larvae elicit clinical agents. The subfamily Oestrinae mutation signs of cavitary myiasis as a seromucous is still unknown. During the last decade, or purulent nasal discharge, frequent some work on genetics, pathophysiology sneezing, incoordination and dyspnea. This and immunology was done in France, infection can result in signs of generalized Italy, Mexico and Spain and a review was disease, causing serious economic losses published by Hall and Wall (1995). in sheep and goat herds reared for meat and Extensive use of macrocyclic lactones dairy produce. The development of larvae is modifying parasitic diversity (Otranto in the nasal-sinus cavities can cause severe and Colwell, 2008), whereas in some areas of clinical signs such as breathing difficulties, 42 VOLUME 2 NO. 2 JULY 2011 MALAYSIAN JOURNAL OF VETERINARY RESEARCH nasal discharge and emaciation, together higher in sheep than in goats after either with the annoyance caused by the adult natural or artificial infestation (Duranton flies. This may lead to production and et al., 1996). Little is known about the economic losses (Dorchies et al., 1998, development of immunity but it is possible 2003). Oestrus ovis can severely impair that some animals are immunodeficient. breathing because it induces tenacious Respiratory disease are common in sheep nasal discharge to which grass, straw and and goats and O. ovis has been suggested dust adhere, clogging the air passages. to have an immunosuppressive effect (with Moreover, the infection may be complicated consequent association with respiratory by sinusal tumour and lung abscesses pathogens) (Dorchies et al., 1993). (Dorchies et al., 1993). Despite the fact that both animal Furthermore, several cases of species can be hosts of this parasite, ophthalmic and naso-pharnygeal myiasis infection prevalence and larval burdens have been reported in humans, indicating are generally higher in sheep than in goats a public health issue in certain areas (Dar after either natural or artificial infestation et al., 1980; Masoodi and Hosseini, 2003). (Duranton et al., 1996, Papadopoulos et al., The opthalmomyiasis produced in man by 2006), and this is taken to indicate higher O. ovis larvae is restricted to conjunctivae, susceptibility in sheep. sclera, eyelids, and lachrymal duct (external opthalmomyiasis) or the eye ball History of Case Report (internal opthalmomyiasis) (Hadani et al. and Dar et al., 1980; Stulting and Meyer, In 2009, a case of respiratory distress 1981; Omar et al., 1988; Amir et al., 1993). accompanied by severe mortality was Myiasis in an incidental host which may reported in Damara sheep that was have biological significance and can also recently imported into Malaysia from a be of medical and public health importance neighbouring country. The report involved if the incidental host is a man. Myiasis 25 heads of 7-month-old, female Damara caused by O. ovis may be considered as crossbred sheep imported in stages over a an occupational disease of shepherds or period of 4-5. They were sent for breeding farmers who usually keep their sheep and purposes to a commercial sheep farm. goats in close proximity to their dwellings The sheep were reared using an intensive (Amir et al., 1993). system where animals were fed grass and This infection can result in generalized pellets. Initially, a few animals exhibited disease, causing serious economic losses severe respiratory signs indicative of in sheep and goat reared for meat and dairy suspected pneumonia. Soon after, the produce. Despite the fact that both animal sheep showed signs of respiratory distress species can be host of this parasite, infection such as loud, noisy breathing, poor body prevalence and larval burdens are generally scores (severe emaciation), ill thrift and 43 MALAYSIAN JOURNAL OF VETERINARY RESEARCH VOLUME 2 NO. 2 JULY 2011 were unproductive with poor kidding foul smell. There was also serous atrophy rates. About 10% mortality was reported of the heart coronary fat and generalized initially. The flock of sheep were treated moderate congestion in all vital organs. with antibiotics by veterinary personnel, Based on the post mortem and clinical and subsequently one of the treated sheep signs exhibited by this flock of sheep, the died 4 days after treatment prompting a differential diagnosis made were bacterial postmortem. The post mortem exhibited pneumonia, viral pneumonia, verminous findings of frothy discharge with foamy pneumonia, chronic helminthiasis and exudation (especially in the bronchus)