B113 - TRYPANOSOMIS

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B113 - TRYPANOSOMIS

Nature of the disease
Trypanosomis tsetse transmitted covers infections by a large number of protozoa of the genus Trypanosoma and transmitted by tsetse flies, Glossina spp. Despite the diversity of parasites, the clinical signs are relatively similar and the disease causes major economic losses. T brucei gambiense and T. brucei rhodesiense are transmissible to human and cause the sleeping sickness but they do not cause symptoms in animals.
Classification
OIE, List B disease (Bovine only).
Susceptible species and Distribution

Trypanosoma spp.

Vectors

Affected animals

Geographic distribution

T. brucei brucei Glossina palpadis,
Glossina tachinoides,
Glossina morsitans
Acute in: Horses, camels, dogs, monkeys
Mild in: Cattle, wild ruminants
Inter-tropical zone of Africa
T. congolense Glossina spp. Cattle, sheep, goats, dogs, camels, horses, wild animals, pigs (rarely) Inter-tropical zone of Africa
T. simiae Glossina spp. Domestic and wild pigs, camels Inter-tropical zone of Africa
T. vivax Glossina spp.
Tabanidae and other biting flies.
Acute in: Cattle, sheep, goats
Mild in: Horses, wild animals
Sub-Saharan Africa, 
South and Central America, 
West Indies
Clinical signs 
The severity of the disease depends on the host and the Trypanosoma involved, clinical signs in cattle include after an incubation period of 1 to 3 weeks:
  • Fever,
  • Weight loss,
  • Anaemia,
  • Adenopathy,
  • Sometimes  petechia on mucosa,

Evolution to chronic disease and high mortality rate. Sometimes acute form with diarrhoea followed by death within a week.

Post-mortem findings 
There is no specific findings, lesions include swollen lymph nodes and anaemia.
Differential diagnosis 
  • Babesiosis
  • Theileriosis
  • Wasting disease
Specimens required for diagnosis 
Microscopic observation of the parasite can be attempted from stained blood smears, it is possible to concentrate the parasite. PCR technique is has been developed. 

Serums can be submitted for serological tests including ELISA and indirect fluorescent antibody test.

Transmission   
Transmission is usually made by the bite of the insect vector whose specificity is variable. T. vivax as be transmitted by a wide range of biting insects (that have regular blood meal). 

Transplacental transmission has been described. Direct transmission through infected blood is possible but rare.

Risk of introduction   
Trypanosomosis could be introduced by importation of infected animals or vectors. However the establishment of the disease will depend on the presence of competent vector. T. vivax has therefore the highest risk to establish.
Control / vaccines  
In the absence of vaccine the control of the disease is essentially made by the control of the vector. Abundant researches on the subject have been carried in Africa. Medical prophylaxy is available but there are resistance problems and drugs are expensive. 

Treatments are also available but considering the risk of drug resistance apparition and the zoonotic character of some trypanosomosis, treatment is not advisable. 

References
  • BUSSIERAS J, CHERMETTE R, Protozoologie In Parasitologie Vétérinaire, Ecole Nationale Vétérinaire D'Alfort, 1992, p 98-104; 119-122.
  • Office International des Epizooties, 2002
  • Trypanosomis, In Merck Veterinary Manual, National Publishing Inc. Eight ed, 1998, Philadelphia, p 33-35
  • Trypanosomis, In Veterinary Medicine, Saunders, Eight ed, 1997, London p. 1212-1218