Fever is the first clinical sign one to three weeks after an infective tick bite. Following the bite, the parasites invade red blood cell where they multiply and invade more red blood cells. The destruction of increasing number of red blood cells causes the affected animals become anaemic, shocked and also release large quantities of red blood cell pigment (haemoglobin) into the circulation. The sick animals are usually depressed, lose appetite, and their eyes and gums are pale from anaemia and yellow (jaundiced) due to bile pigments in their circulation. Red coloured urine can usually be observed in these animals. Pregnant animals often abort. In severe B. bovis infection cases, signs like nervous signs, incoordination, paralysis and coma are presented which often lead to death.
Babesia infections can range from inapparent to acute severe diseases. In severe cases, animals often die within one or two days of the appearance of clinical signs. However, in less severe cases, animals can have a fever for about a week and sick for about three weeks. After that, they can have slow recovery, but will remain infected carriers for the rest of their lives.
Babesiosis can be treated with various drugs. However, treatment should be administered as early as possible to make it effective. Among the currently available drugs, imidocarb and diminazene aceturate are the most widely used for treating babesiosis. It should be noted that some of the drugs are potentially toxic and manufacturers' recommendations must be carefully followed.
In endemic areas, many indigenous cattle are naturally infected with babesiosis in calfhood, and are immuned as a result. This situation is called #fblue endemic stability#d. Generally, no control measures are required in these areas. Occasionally, immuned animals may develop clinical babesiosis under stress, malnutrition, other diseases or overwork, and these should be treated as they arise.
However, in some endemic areas, indigenous cattle may not have been naturally infected and immuned early in life due to the inactivity of the Boophilus vectors, e.g. prolonged dry seasons, droughts, etc. Outbreaks of babesiosis can sometimes happen to indigenous cattle. 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 babesiosis. If they are introduced into endemic areas, they must be vaccinated on arrival to avoid heavy losses. Strict tick control programme aimed at the one-host Boophilus ticks is another option. However, because the difficulties in practice to ensure that the protected cattle are not exposed to infected ticks, the disease control is often more efficient to combine tick control with vaccination.
WWW Sites of Relevance
Department of Health - Hawaii
World Organisation for Animal Health