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Tentang ilmu biology dan patalogi dan kontrol
Typology: Lecture notes
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Pathology: the house fly, M. domestica, is closely associated with humans, livestock, their buildings and organic wastes. Although it may be of only minor direct annoyance to animals, its potential for transmission of viral and bacterial diseases and protozoan and metazoan parasites is of sig- nificance. However, its pathological importance varies considerably, depending on the precise circumstances in which it occurs. The free avail- ability of livestock or human excrement and low levels of hygiene provide sites in which flies can breed and allow flies to act as vectors as they move from site to site. Pathogens may be carried either on the hairs of the feet and body or regurgitated in the saliva during feeding. More than 100 pathogens associated with the house fly may cause disease in humans and animals, including typhoid, cholera, tuberculosis, anthrax, and conjunctivitis. Musca domestica are also thought to be capable of harbouring and trans- mitting Corynebacterium pseudotubercolosis, the bacterium responsible for mastitis in dairy herds, after feeding on lesions or contaminated milk. When fed on contaminated milk, house flies harboured the bacterium on their body surface for the following 5 minutes, in their saliva for up to 3 hours and in their faeces for between 1 and 4 hours after feeding. In humans, the house fly is important in the spread of Shigella and other enteric bacteria. House flies are suspected to be mechanical vectors of the Escherichia coli patho- gens, harbouring the bacteria in their intestine and excreting it for at least 3 days after feeding. Eggs and larvae of various nematodes which affect horses, such as Habronema spp., may also be carried. The latter, when deposited in wounds, may give rise to skin lesions of habronemiasis, commonly called `summer sores' in horses. Granulomatous nodules, which contain the nematode larvae, appear on the skin, especially around the eye, ventral abdomen, prepuce and lower limbs. In northern Europe, the face fly, M. autumna- lis, may often be the most numerous fly worrying cattle in pasture. In Britain this species tends to be found in more southerly areas and, in general, is not found north of Yorkshire. Musca autumnalis is also one of the most important livestock pests to invade the United States in recent years. Its introduction into North America from Europe was first detected in 1951 in Nova Scotia. From there it spread southward and, by 1959, many cases were being reported on cattle. It now occurs practically throughout the USA. Face flies are generally found around the eyes and nose of livestock or on wounds where the females feed. The annoyance caused by the flies results in cattle aggregating and bunching in the shade to escape and contributes to reduced production rates. In the USA, M. autumnalis is an important vector of bovine keratoconjunctivitis caused by Moraxella bovis. Face flies are also intermediate hosts of Parafilaria bovicola, the causative agent of par- afilariosis of cattle in northern Europe and else- where, and the irritation of the eye arising from their feeding can exacerbate the transmission of pinkeye and other conditions such as eyeworm. Adults are developmental hosts for Thelazia (Spirurata: Thelaziidae) nematodes which live in the conjunctival sac of cattle and horses, causing conjunctivitis, keratitis, photophobia and epi- phora. This disease is an increasing problem in the USA. Musca sorbens is thought to be the principal insect vector of Chlamydia trachomatis, the cau- sative agent of trachoma in parts of Africa. In addition to dung feeding, adults of the bush fly M. vetustissima will persistently attempt to feed at the mouth, eyes and nose. As a result, they are of considerable significance as a nuisance pest in Australia for both livestock and humans. In the absence of native Australian dung beetles capable of disposing of the dung of introduced cattle, the dung of these herbivores is slow to decompose, allowing M. vetustissima ample opportunity to breed and reach large and problematic popula- tion densities.
Species of the genus Hydrotaea closely resemble species of Musca and are known as the sweat flies and head flies. They feed on exudates of the eyes, nose and mouth. They do not bite. The genus contains one particularly important species, 94 Veterinary Ectoparasites: Biology, Pathology and Control VetBooks.ir