Description, Causes and Risk Factors:
Parafilaria multipapillosa is a parasitic nematode of the genus Parafilaria, which affects horses causing hemorrhagic subcutaneous nodules in the head and upper forelimbs, in North Africa, Southern and Eastern Europe, Asia and South America, leading to bleeding from the skin. It is very rarely effect human beings.
P. multipapillosa is found in the subcutaneous tissues of horses in various parts of the world; it is especially common in the Russian steppes and eastern Europe. It is similar in size, appearance, life cycle, and development to P. bovicola. Blood-sucking Haematobia spp are thought to be the invertebrate hosts.
In spring and summer, the parasite causes skin nodules, particularly on the head and upper forequarters. These bleed transiently but often profusely ("summer bleeding") and then resolve; other hemorrhaging nodules develop as the parasite moves to a different site. Occasionally, the nodules suppurate. The nodules and bleeding are unsightly and interfere with harnesses of working horses but generally are of little consequence. The clinical signs are pathognomonic.
The invertebrate hosts are face flies of the genus Musca (subgenus Eumusca), which ingest the eggs when feeding at the bleeding spots. M. autumnalis has been identified as a host in Sweden, M. lusoria and M. xanthomelas in South Africa, and M. vitripennis in Asia. Development to infective third-stage larvae in the fly takes 10-12 days. Transmission to cattle probably occurs when the flies feed on wounds, Parafilaria bleeding spots, or ocular secretions.
No satisfactory treatment has been reported, but fly control may reduce the incidence.
The only external signs of infection in cattle are focal cutaneous hemorrhages ("bleeding spots") that may ooze for some hours before clotting and drying in the matted hair of the coat. Bleeding spots are induced by the female worm, which causes the formation of a small nodule, perforates the skin, and oviposits in the blood dripping from the central wound. The tiny eggs contain the first larval stage (microfilariae) of the parasite. In both the Northern and Southern hemispheres, bleeding spots are markedly seasonal, being most common in spring and early summer. Most bleeding spots occur along the dorsum of the animal, particularly in the forequarters.
The seasonal bleeding spots are sometimes confused with those caused by thorns, wire, ticks, or biting insects. For differentiation, either fresh or dried blood should be mixed with water in a test tube and centrifuged. The characteristic eggs are found on microscopic examination of the sediment.
Carcass lesions can be differentiated from bruising by the presence of numerous eosinophils in Giemsa-stained impression smears made from the lesions. In addition, affected tissue has a characteristic, disagreeable, metallic smell.
Usually, only small numbers of worms are present in affected carcasses and are often difficult to find because of their color and the accompanying inflammatory reaction. Affected tissues can be incubated in warm saline to facilitate the recovery of parasites. An ELISA for the detection of antibodies against P. bovicola has been developed.
Ivermectin or nitroxynil (20 mg/kg) given by SC injection reduces the number and surface area of Parafilaria lesions. Animals should be treated at least 70-90 days provide sufficient time for lesions to resolve.
In trials in Finland, use of pyrethroid-impregnated ear tags gave good control of flies and reduced Parafilaria. Ear tagging all cattle in an area resulted in total control of the parasite. The use of residually active, synthetic pyrethroid dips has also been effective in reducing transmission.
It may be possible to screen imported animals with the ELISA to prevent spread of the disease to unaffected countries or, in conjunction with residual insecticides and effective anthelmintics, to eradicate new foci of infection.
NOTE: The above information is for processing purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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