Introduction: Babesiosis (Texas fever, tick fever, redwater) is caused by tick-borne protozoa of the genus Babesia. There are over 70 species, but Babesia bovis and B. bigemina are the most common ones to cause problems. Both can be transmitted by ticks and are often transmitted along with Anaplasma marginale (see page F27). The combination then produces tick fever, a fatal syndrome. It is found throughout the United States and is especially a problem in tropical areas of the world.
Clinical Signs: Affected cattle may suffer from acute (sudden), chronic (long term) or inapparent symptoms. In acute cases, the first sign is a high fever (107 degrees F) followed by a lack of appetite and red urine (sometimes called redwater). More advanced signs include incoordination, grinding of the teeth, mania, coma or death. Jaundice (yellowing of the gums and white of the eye) and anemia may appear as well. A necropsy on an animal that has died from B. bigemina will often reveal edema (fluid swelling), jaundice, yellow and gelatinous fat, and thin and watery blood. The spleen is often enlarged, dark, soft and pulpy. The liver can be enlarged, pale and yellowish. The gallbladder is distended with thick, dark bile.
Disease Transmission: Ticks of the Boophilus spp., as well as some biting flies, bite an infected animal and transfer the protozoa to another animal with subsequent bites. Babesiosis can be spread by the nymph and adult stages of the tick.
Diagnosis: Giemsa-stained, thin and thick blood smears are the most effective way to diagnose babesiosis. The protozoal organism is observed in these blood smears. Serological tests are also used for a specific diagnosis of the disease. Of these tests, the indirect FA test is the most accurate.
Treatment: If treated early, acute babesiosis responds well to the following compounds: diminazene diaceturate (3-5 mg/kg), phenamidine (8-13 mg/kg), amicarbalide (5-10 mg/kg), and imidocarb (1-3 mg/kg). Some of these compounds are not available in the United States. All should be used under the direction of a local veterinarian. Imidocarb dipropionate can also be given as a prophylactic (preventative) that will provide several weeks protection to susceptible animals.
Prevention: In the United States, the best preventions include eradication of the tick vectors, followed by repeated treatments using acaricides to destroy ticks on the animal or in the environment. In some areas where infections are very common, different forms of vaccination are available and sometimes used.
In the United States, babesiosis is a reportable disease, and any suspected case should be reported to local authorities.