Trypanosoma congolense Broden, 1904

(Figure 1-32)

ETYMOLOGY: This parasite is named after the Congo location in which it was first observed.

SYNONYMS:Trypanosoma dimorphon Laveran & Mesnil, 1904; Trypanosoma nanum Laveran, 1905; Trypanosom confusum Montgomery & Kinghorn, 1909; Trypanosoma montgomeryi Laveran, 1909; Trypanosoma pecorum Bruce et al., 1910; Trypanosoma frobeniusi Weissenborn, 1911; Trypanosoma Somaliense Maroglio, 1911; Trypanosoma cellii Martogio, 1911; Trypaonsoms multiforme Kinghorne et al., 1913; Trypaonson randae van Saceghem, 1921; Trypanosoma urundiense chardome & Peel, 1967; Trypanosoma berghei Chardome & Peel, 1967; Trypanosoma mossosense Chardom & Peel, 1967.

HISTORY: This parasite was first observed in the blood of sheep and a donkey in Leopoldville (Kinshasa) of The Congo, and Broden noted that it was small and did not have a free flagellum. This is the major trypanosome of African animals, and the most important animal trypanosome in East Africa.

GEOGRAPHIC DISTRIBUTION: Tropical Africa south of the Sahara, within the range of the Tsetse fly.

LOCATION IN THE HOST:Trypanosoma congolense is a parasite of mainly of the blood, although it may be found at times in tissue fluids.

IDENTIFICATION OF THE PARASITE:Trypanosoma congolense is a small trypanosome measuring 9 to 18 m in length (Fig. 1-18). There is typically no free flagellum observed in Giemsa-stained organisms and the undulating membrane typically has no more than 3 to 4 undulations throughout the length of the cell body. The kinetoplast is relatively small, tends to be marginal, and is just subterminal to the posterior end of the body. In fresh blood, the trypanosome is active but shows no progressive motion through red blood cells rarely leaving the field of view in the microscope.

LIFE CYCLE: This parasite is transmitted between hosts by the bite of the Tsetse fly which serves as a required biological vector of this para site.

CLINICAL PRESENTATION AND PATHOGENESIS: This parasite is capable of causing disease in most domestic animals. The disease is typically one of anemia that is considered to be related to an inhibition of hematopoiesis. There have been few reports in cats.

In six cats experimentally infected with Trypanosoma congolense, organisms appeared in the blood within 11 to 25 days after infection but were difficult to find throughout the course of the infection (Laveran, 1909). All six cats died within 68 to 85 days after infection. At necropsy, two of the cats were noted to have splenomegally.

TREATMENT: Treatment has not been tried in cats.

EPIZOOTIOLOGY:Trypanosoma congolense is considered to use domestic cattle and wild game as reservoir hosts. It is unclear how often cats may be infected.


HAZARDS TO HUMANS:Trypanosoma congolense is not considered to be a human pathogen. However, precautions should be taken to reduce potential hazards to humans in the veterinary clinic where an accident with a contaminated needle could serve to introduce the parasite into someone supplying veterinary care.

CONTROL/PREVENTION: There is currently very little known about the prevalence, control, or prevention of the disease in cats. The biology of the parasite would suggest that cats should be protected from fly bites.


Laveran A. Au sujet de Trypanosomacongolense Broden. Bull Soc Pathol Exot 2:526-528.

FIGURE 1-32. Trypanosoma congolense in the blood of a mouse. In this preparation, the flagellum is clearly evident as it undulates along the body of this parasite.