Trypanosoma spp

From Cow
Tsetse flies (Glossina spp), the principal transmitting arthropod of Trypanosomiasis
Trypanosoma spp parasite in infected blood
Weight loss and anorexia in a cow infected by Trypanosoma spp protozoa

Trypanosoma spp are a tsetse fly-transmitted flagellated protozoan 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[1]. Many untreated cases are fatal.

Cause

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. evansi
  • 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.

Clinical signs

Primary clinical signs include fever, jaundice, decreased milk production, weight loss, profuse diarrhea, abortion, anemia, leukocytosis and hyperfibrinogenemia[2]. 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

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 as well as diagnostic assays such as ELISA[3] and PCR testing[4].

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.

Treatment

Various drugs have been used to treat bovine trypanosomiasis, including diminazene aceturate, isometamidium chloride, homidium bromide[5] and melarsomine hydrochloride[6].

Eradication of herds infected with trypanosomiasis involves eradication of tsetse flies[7] 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.

References

  1. Tesfaye D et al (2012) Economic burden of bovine trypanosomosis in three villages of Metekel zone, northwest Ethiopia. Trop Anim Health Prod 44(4):873-879
  2. 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
  3. Rahman WA et al (2012) Comparative seroprevalences of bovine trypanosomiasis and anaplasmosis in five states of Malaysia. Trop Biomed 29(1):65-70
  4. Laohasinnarong D et al (2011) Prevalence of Trypanosoma sp. in cattle from Tanzania estimated by conventional PCR and loop-mediated isothermal amplification (LAMP). Parasitol Res 109(6):1735-1739
  5. Sow A et al (2012) Field detection of resistance to isometamidium chloride and diminazene aceturate in Trypanosoma vivax from the region of the Boucle du Mouhoun in Burkina Faso. Vet Parasitol 187(1-2):105-111
  6. Desquesnes M et al (2011) An evaluation of melarsomine hydrochloride efficacy for parasitological cure in experimental infection of dairy cattle with Trypanosoma evansi in Thailand. Parasitology 138(9):1134-1142
  7. Magona JW & Walubengo J (2011) Mass-treatment and insecticide-spraying of animal reservoirs for emergency control of Rhodesiense sleeping sickness in Uganda. J Vector Borne Dis 48(2):105-108