Nasal myiasis due to Oestrus ovis infestation in a dog

Abstract

NASAL myiasis caused by the sheep bot fly, Oestrus ovis, is a common cause of disease in sheep in warm climates. In the Mediterranean, the disease occurs mainly in the spring and summer months when adult flies emerge, mate, and females deposit the first instar larvae on the nostrils of sheep. In the nasal cavity, larvae develop into the third instar which are recognised by the presence of two characteristic black oral hooks, two black posterior spiracles and dorsal transverse bands of pigment, measuring about 30 x 8 mm. After two to 10 months, mature larvae are sneezed into the external environment, where they complete the life cycle (Kimberling 1988). The present communication reports the diagnosis of an unusual infestation by 0 ovis in a dog.In May 1996, an eight-year-old intact male German shorthair pointer was presented at a private practice with frequent sneezing, moderate pyrexia (39.3'C) and slight weakness. No nasal discharge had been noted and, at general examination, the clinician only noted a rhinitic condition. The animal was correctly vaccinated against canine distemper, canine parvovirus, canine adenovirus hepatitis and leptospirosis. It was currently being treated with 6 pg/kg ivermectin orally (Cardotek, MSD AgVet) each month as a preventive measure against canine filariosis. The owner had kept the dog in a flat and it was rarely taken outside. Rhinitis was diagnosed and the animal was treated with a broad spectrum antibiotic (amoxycillin, 30 mg/kg per day for seven days) and anti-inflammatory therapy (a single dose of methylprednisolone, 10 mg/kg intramuscularly).After a week, the dog did not show any evidence of improvement, with frequent sneezing and slight pyrexia; it did, however, show apparently normal activity and a normal demeanour. The treatment was changed to an antihistamine (dexchlorpheniramine, 5 mg/kg twice a day) and broad spectrum antibiotic (doxycycline, 10 mg/kg per day for a week).Two weeks after the first visit to the clinician, the animal had not improved. Moreover, it started to show a serous unilateral (left) nasal discharge. Rhinoscopy was undertaken but no foreign bodies or masses were observed. Marked congestion and inflammation of the nasal mucosa was observed; the mucosa was prone to bleeding on contact with the rhinoscope making exploration difficult. Dorsal and lateral radiographs showed no abnormality.Over the following days the serous nasal discharge changed to a mucous discharge with frequent left unilateral epistaxis. An ELISA test to detect antibodies against Leishmania species was negative. Confirmation of this result was obtained a week later with a sec-FIG 1: Remnants of a third instar Oestrus ovis larvae located in the nasal cavity of a male German shorthair pointer. A hook is observed (arrow head) near a disrupted layer of chitin (arrows). The structure is surrounded by fungi. Periodic acid-Schiff, bar = 10 pm ond test against Leishmania species. Surgical exploration using a rhinotomy was declined by the owner, who requested that the dog be euthanased.At nec...

Nasal myiasis in a cat caused by larvae of the nasal bot fly,Oestrus ovis

“…In affected individuals, there is an acute onset of discomfort and a ‘foreign body’ sensation, with extreme irritation of the throat, itching and coughing, as well as nasal, aural and ocular symptoms. Similar findings have been reported sporadically in the dog, with sneezing as the most prominent clinical sign 6–8 …”

Oestrus ovisL. (Diptera: Oestridae) Induced Nasal Myiasis in a Dog from Northern Italy

“…As to dogs, it should be noted that in domestic carnivores (dogs and cats) O. ovis infestions are less common than in humans, having been sporadically described in dogs from India [ 11 ], Spain [ 12 , 13 ], New Zealand [ 14 ], and UK [ 16 ] and in a cat from Australia [ 15 ]. Low occurrence of O. ovis infestions in domestic carnivores might be due to peculiar sheep bot fly preferences and, in general, due to the strong relationship between oestrids and herbivores.…”

Oestrus ovis infestation of a dog in the UK

“…The dog had suffered violent sneezing episodes but only a mild rhinitis, probably as a result of prolonged immunotherapy, but more severe consequences have been recorded in other cases. The report of Lujan and others (1998) of a dog in Spain describes serous discharge and inflammation of the nasal mucosa progressing to mucous discharge and frequent unilateral epitaxis; necropsy revealed three retained third‐stage O. ovis , which had resulted in a diffuse haemorrhagic rhinitis.…”

“…There are reports that O. ovis is attracted to domestic animals other than sheep and goats. Webb and Grillo (2010) described a case in which numerous first‐stage larvae were flushed from the nasal passages of a cat in New South Wales, Australia, and several incidents have now been reported in dogs (Lucientes and others 1997, Lujan and others 1998, Heath and Johnson 2001). In dogs, development to the mature third larval instar can occur, which contradicts the long‐held belief that such aberrant fly behaviour will fail to result in progressive larval moults and growth in these unusual hosts (Zumpt 1965).…”