Anaplasmosis, also called Gall sickness, is a tick-borne disease. It
is one of the major threats to cattle industries in Africa. In many tropical
and sub-tropical areas, virtually all indigenous cattle are infected but
immuned and suffer no ill effects. However, when exotic cattle are introduced,
heavy losses can occur unless precautions are taken. If anaplasmosis is
suspected, a blood smear should be taken from the tip of either the ear
or the tail of the sick animals and sent to the laboratory. Controlling
the disease is rather complicated which involves a combination of treatment,
vaccination and tick control.
Clinical signs:
Cattle from endemic areas are commonly infected with anaplasmosis
when they were calves. These animals are infected with the disease
throughout life. They are usually healthy, although the infections
may flare up under stress and cause a mild form of the disease. In non-endemic
areas, however, cattle are more susceptible. The incubation
period of the disease ranges from two to, rarely, twelve
weeks. The typical clinical signs of
the diseased animals include: anaemia; visible
mucous membranes, e.g. gums and eyes,
become pale and later yellowish in colour
(jaundice); depression; loss of appetite; incoordination
and laboured breathing; females abort and suffer a drop in
milk yield.
Post-mortem signs:
The typical post-mortem signs of anaplasmosis
include: organs and tissues become yellowish discoloured; spleen
enlarged and the gall bladder is distended with thick brownish-green
bile. However, these signs can
also occur in other diseases, such as babesiosis
and heartwater.
Treatment:
Most of the sick animals die within a few days of the fever starting, if they are not treated. The use of tetracyclines or imidocarb diproprionate is effective, however, the drug mush be administered early in the disease.
Control measures:
In many tropical and sub-tropical areas, virtually all indigenous cattle are infected but immuned. This situation is called #fblue endemic stability#d and generally no control measures are required in these areas. Occasionally, immuned animals may develop clinical anaplasmosis under stress and these should be treated as they arise.
In endemic areas, ticks and biting flies are only active in certain
seasons. Outbreaks of anaplasmosis can sometimes happen to indigenous cattle
which have not been infected with the disease in calfhood. This situation
is called #mendemic instability#m. In these areas, young cattle should
be vaccinated to protect them until they are naturally immuned.
Exotic cattle are very susceptible to anaplasmosis. If they are introduced
into endemic areas, they must be vaccinated on arrival to avoid heavy losses.
WWW Sites of Relevance