Trypanosome

(Trypanosoma spp.)

Trypanosoma spp. are vector-borne parasites that infect a wide range of wild and domestic mammal species, including cats. Trypanosoma cruzi is zoonotic.

Parasite species: Trypanosoma brucei, T. evansi, T. congolense, T. cruzi, T. rangeli
Common name: Trypanosomes
Hosts: Several wild and domestic mammal species, including cats
Pre-patent period: 5 days for T. brucei (25-44 days when cats were fed with infected goat meat, mouse or guinea pig), 11-25 days for T. congolense, 14-15 days for T. evansi
Location in the host: Blood and eventually tissue fluids
Distribution: Worldwide
Transmission route: By tsetse flies (T. brucei, T. congolense), triatomine bugs (T. cruzi, T. rangeli), biting flies (T. evansi), and possibly predation of infected rodents (T. cruzi, T. evansi)
Zoonotic: Yes (T. cruzi)

Distribution

Trypanosoma brucei is found in western Africa and T. congolense is found in tropical Africa south of the Sahara. Trypanosoma evansi is found in Africa north of the Sahara, Asia, and Central and South America. Trypanosoma cruzi is found in the southern United States, and throughout Mexico, Central America, and South America down into Argentina. Trypanosoma rangeli is found in Central America and South America down into Chile.

Clinical signs

Trypanosoma brucei can cause severe disease in cats. Clinical signs may include fever, pale mucous membranes, ocular disorders (even blindness) and weakness. In experimental infections, post-mortem examination revealed pronounced wasting with generalized lymphadenomegaly, splenomegaly, hepatomegaly and pleural and pericardial haemorrhages. Experimental infection by T. congolense produced a fatal outcome in six cats, all of which presented hepatomegaly upon post-mortem examination. Trypanosoma evansi can cause lethargy and inappetence, sunken eyes, and incoordination in cats. Trypanosoma cruzi infections in cats are usually subclinical; a cat from Montevideo, Uruguay, showed convulsions and transient posterior paralysis.

Figure 1. Trypanosoma congolense from a blood smear of a dog (Image credit: Dr. G. Baneth)

Diagnosis

Trypanosoma infections can be confirmed by cytological examination of Giemsa stained blood smears (Fig. 1). The trypomastigote stages are 20 μm long in T. cruzi (1-2 undulations of the undulating membrane), 26-34 μm long in T. rangeli (with 4-5 undulations of the undulating membrane), 9-18 μm in long in T. congolense (with 3-4 undulations of the undulating membrane). Trypanosoma brucei has a short and stumpy form (12-26 μm long) with no free flagellum and a long and slender form (23-42 μm long) with a free flagellum. Trypanosoma evansi is morphologically indistinguishable from T. brucei [1].

Treatment

No effective treatment has been described in cats.

Prevention and Control

No effective treatment has been described in cats.

Public health considerations

Trypanosoma cruzi is the causative agent of Chagas disease (American trypanosomiasis), a major neglected tropical disease. Cats are considered reservoirs of this parasite, potentially an amplifying host, but the actual role of cats in the maintenance of the zoonotic cycle of this parasite is probably minor.

References

[1] Bowman DD, Hendrix CM, Lindsay DS, Barr SC. Feline Clinical Parasitology. Iowa State University Press, Ames, USA. 2002.

[2] Gürtler RE, Cardinal MV. Reservoir host competence and the role of domestic and commensal hosts in the transmission of Trypanosoma cruzi. Acta Tropica. 2015;151:32-50.