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Anaplasmosis: Tick-borne disease of ruminants
2008-02-19 10:07:05
By Luumba Rashid
Dear reader our to days theme is another blood parasite which cause disease to our animals. This disease known as ANAPLASMOSIS which formally known as gall sickness.
The disease is mainly of ruminant and caused by obligate intraerythrocytic parasite of the family Anaplasmataceae, genus Anaplasma.
This disease may infect all ruminant animals including cattle, sheep, goat, deer, antelope, giraffe and buffalo, but bovine anaplasmosis is of the most economic significance, following the nature of the animals per se, as we know these kinds of animals are mainly of production purposes.
The occurrence of the disease is world wide and can be caused by Anaplasma marginale, and another species of importance are Anaplasma caudatum, which may cause severe disease and Anaplasma centrale which generally result in mild disease while Anaplasma ovis may cause mild to severe disease in sheep, deer and goat.
The disease is not contagious, most transmission occurs via numerous species of tick vectors. There is more than 16 species of ticks of which seven genera (Boophilus, Dermacentor, Rhipicephalus, Ixodes, Hyaloma, Argas and Ormithodoros) have been shown experimentally to transmit Anaplasmamarginale.
Even though not all of these are likely to be significant vector in the field but Boophilus species ( it is the biggest tick, blackish gray when full of blood.) are major vector in Africa.
After vector tick feeding on an infected animals intrastadial or trans- stadial transmission may occur; Trans-ovarial transmission may also occur though it is very rare.
A replicate cycle occurs in the infected ticks, but mechanical transmission via biting dipterans occurs in some region while transplacental transmission has been associated with acute infection of the cow in the second or third trimester of gestation. Anaplasmosis can also be transmitted or rather be spread through the use of contaminated needle or dehorning instrument and surgical equipment or during surgery procedures.
Calve are said to be much more resistance to disease (although not infection) than order cattle. This resistance is not due to colostral antibody from immune.
In endemic areas where calves first become infected with Anaplasma marginale early in life losing them due to anaplasmosis are minimal. After recovery from the acute phase of infection, cattle remain chronically infected carriers of the parasite and immune to further clinical disease, However these chronically infected cattle may relapse to anaplasmosis when immunosuppressed ; when infected with other parasite.
Carriers serve as a reservoir for further transmission. Serious loses due to anaplasmosis occur when mature cattle with no previous exposure are moved into endemic areas or under endemically unstable situation when transmission rate are insufficient to ensure all cattle are infected before reaching the more susceptible adult age.
Clinical findings.
Anaplasmisis is characterized by progressive anemia due to extavascular destruction of infected and uninfected erythrocytes. These parasites are destructive of red blood cell that\'s why there is anemic condition. The prepatent period of Anaplasma marginale is directly related to the infective dose and typically range from 2-8wks.
This parasite approximately doubles every 24hrs during the exponential growth phase.
Generally 10-30%of red blood cell are infected at peak parasitemia, although reterature this figure may be as high as 65%of red blood cell count and hemoglobin\'s values are all severely reduced.
Macrocytic anemia with circulating reticulocytes may be present late in the disease. Acutely infected animals lost condition rapidly, drop of milk production and in appearence, also there is loss of coordination, and always breathlessness when excited and a rapid bounding pulse are usually evident in the late stages. There is change of urine colour to brownish due to excessive death of red blood cell.
Also there is a transient febrile response with the temperature rarely exceeding 41 deg centigrade this always occurs at about the time of peak parasitemia. The mucous membrane appear pale and then yellow.
This is all membrane of eye, vulva, under the tongue, and prepuce for the bull (male cow). Pregnant cow may abort due to high fever. Sometime animal may defecate the mucous feces and constipations follows, and then dryness of the muzzle.
Surviving cattle convalesce over several weeks during which hematologic parameters gradually return to normal.
porstmortem to the carcass of cattle that die from anaplasmosis are generally marked anemic and jaundiced, blood is thin and watery also the spleen characteristically enlarged and soft, with prominent follicles, liver may be mottled and yellow-orange while gall bladder (bile bladder) is often extended and contains thick brown bile.
Diagnosis of Anaplasma marginale can be done under microscopical examination of giemsa-stained, thick and thin blood film which is collected by experienced veterinarian and being examined with a qualified laboratory personnel.
Another area one can be able to derive diagnosis is through clinical findings though the disease is most likely resemble with other disease like Babesiosis, leptospilosis, and theileriosis. therefore it is important to call competent and experienced veterinary to attend the case.
The chronically infected carriers may be identified with a fair degree of accuracy by serologic test using either complement fixation or card agglutination test.
Treatment with any strong antibiotics such as oxytetracycline, tetracycline together with Imidocarb are currently used for treatment of the said disease.
Through properly recommended dose may sterilize cattle and remain immune to severe anaplasmosis subsequently for at least 8month and imidocarb is also highly efficacious against the disease as a single injection.
Because the disease causing anemia hence the use of iron dextrose injection is preferable and multivitamins or B complex should be used as supportive treatment in order to restore deficiencies.
To control the disease is by observing tick control parameters by frequent dipping and spraying animals with strong accariside (insectcides), cleanness of the premises, control grazing.
And make sure you check blood parasite test of your animals every three month to avoid resistance of the said parasite.
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