Trypanosoma spp are a tsetse fly-transmitted blood parasite which causes disease in cattle in Africa and Central and South America. Trypanosomiasis causes serious economic losses in cattle from anemia, loss of condition and emaciation. Many untreated cases are fatal.
Transmission of Trypanosoma spp is by biting flies (Tsetse - Glossina spp and Tabanus spp). A number of trypanosome species have been identified which infect cattle:
- T. congolense
- T. vivax
- T. brucei brucei
- Trypanosoma theileri - nonpathogenic
Most tsetse transmission is cyclic and begins when blood from a trypanosome-infected animal is ingested by the fly. The trypanosome loses its surface coat, multiplies in the fly, then reacquires a surface coat and becomes infective. T brucei spp migrate from the gut to the proventriculus to the pharynx and eventually to the salivary glands; the cycle for T congolense stops at the hypopharynx, and the salivary glands are not invaded; the entire cycle for T vivax occurs in the proboscis. The animal-infective form in the tsetse salivary gland is referred to as the metacyclic form. The life cycle in the tsetse may be as short as 1 wk with T vivax or extend to a few weeks for T brucei spp.
Primary clinical signs include fever, jaundice, decreased milk production, weight loss, profuse diarrhea, abortion, anemia, leukocytosis and hyperfibrinogenemia. Animals lose condition and become progressively emaciated. Milk yield may be decreased in dairy animals. Neurological signs like dysmetria, ataxia, muscle weakness, ptyalism, lymph node enlargement and submandibular edema are less common. Cardiac lesions, diarrhea, keratitis, lacrimation, appetite loss and other clinical signs have also been reported.
Diagnosis is based on presenting clinical signs, predisposition to cattle in the area as well as supportive diagnostic testing. Confirmation depends on demonstrating trypanosomes in stained blood smears or wet mounts. The most sensitive rapid method is to examine a wet mount of the buffy coat area of a PCV tube after centrifugation. Differential diagnoses include Babesiosis, Anaplasmosis, and Haemonchus spp infection.
Various drugs have been used to treat bovine trypanosomiasis, including Diminazene aceturate, Isometamidium chloride and Homidium bromide.
Eradication of herds infected with trypanosomiasis involves eradication of tsetse flies and use of prophylactic drugs. In West Africa, several breeds of cattle have been identified that show innate resistance to trypanosomiasis and play a valuable role in reducing the impact of the disease in this area. However, resistance may be lost due to poor nutrition or heavy tsetse challenge.
- Cadioli FA et al (2012) First report of Trypanosoma vivax outbreak in dairy cattle in São Paulo state, Brazil. Rev Bras Parasitol Vet 21(2):118-124