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Definition
- Trypanosomosis is a group of diseases affecting mammals, domesticated and wild animals, as well as man and birds caused by various species of Trypanosoma
Aetiology
- Trypanosoma evansi – Surra
- T. equiperdum – Dourine
- T. equinum – Mal de caderas
- T. congolense and T.vivax - Wasting disease in cattle
- T.cruzi - Chaga's disease or American trypanosomosis
- T.gambiense - Sleeping sickness in man
- T.brucei - Nagana or tsetse fly disease or african trypanosomosis
Life cycle
- Common vectors are blood sucking flies of the group Tabanus, Stomaxys, tsetse, glossina etc.
- Non pathogenic Trypanosomes are also present. Defiinite cyclic development occurs in the body of true invertebrate hosts.
- In these hosts, Trypanosomes multiply in various forms in the digestive tract, finally migrate as infective forms to the salivary glands and are injected into the mammalian host with the vector's saliva at the time of the bite.
- In T.cruzi, the infective stage is located in the hind gut and is excreted in the faeces of the arthropod (Triatoma sp.) when the arthropod defecates at the time of its bite.
- When transmitted through vector saliva Trypanosomes are referred to as salivarian and when through arthropod faeces as stercorarian
Pathogenesis
- The Trypanosomes of american trypanosomiasis invade cells whereas african trypanosomiasis do not.
- Following entry into the mammalian host, african trypanosomiasis rapidly multiply by binary fission within the blood stream leading to parasitaemia.
- The parasite's unique ability to undergo almost endless antigenic variations through changes in surface glycoproteins. Because of their variability, these surface antigens are called variable surface glycoproteins(VSGs).
- Trypanosomes may also enter the interstitial space and multiplication occurs. Glomerulonephrits and vasculitis which may occur in chronic trypanosmiasis can result from the continuous immune response and the formation of antigen and antibody complexes.
Evasion of the immune response by Trypanosomes
- Trypanosomes may promote the development of suppressive regulatory cells, or stimulate the B cell system exhaustion.
- Immunosuppression induced by trypanosomes can lead to the death of host as a result of secondary infection either by bacterial pneumonia or sepsis.
- In addition to immunosuppression, trypanosomes have evolved two other effective evasive techniques as 1. Becoming non-antigenic 2. Ability to alter surface antigens rapidly and repeatedly ( i.e. antigenic variation)
Surra
- Definition
- Surra is an acute or chronic disease of all domestic animals chiefly of equines caused by T.evansi. Camel also affected. Surra is always fatal in camels and horses.
- Clinical signs
- In horses : Intermittent fever, serous nasal discharge, petechiae and ecchymoses of visible mucosae, oedema of dependant parts, incoordiantion, icterus and anaemia.
- In cattle and buffaloes , the condition is milder. Temperature, aimless walking in circles, salivation, grinding of teeth, coma. Surra may affect the quality of semen in bulls, and cause irregular oestrus, abortion and stillbirths in cows.
- Blood picture
- Progressive anaemia with reduction of erythrocyte and haemoglobin content
- Hypoglycaemia develops as the parasite consume large amount of glucose
- Gross lesions
- Spleen and lymph nodes are enlarged and show hyperplasia of follicles.
- Petechiae and ecchymoses of mucosa and serosa are also observed
- Microscopic lesions
- Microscopic lesions characterized by lymphoplasmacytic infiltrate of various organs including the brain and spinal cord. Trypanosomes can be detected in body fluids
- Diagnosis
- Examination of blood smear in acute phase of infection
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Peripherla blood smear-Trypanosoma evansi
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Mal de carderas
Chaga's disease
Dourine
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It is a disease of equines transmitted by coitus characterized by oedematous lesions in the genital tract. The lesions are those of mononuclear or granulomatous inflammation
Nagana
Nagana is african trypanosomiasis causing gradual wasting in domestic animals. Metacyclic trypanosomes are injected into the host by the fly during feeding. They multiply at the subcutaneous site, provoking a local skin reaction called a chancre. Within the chancre, m etacyclic trypanosomes change to trypomastigote form and enter the blood stream directly or through lymphatics.
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Diagnosis
- Demonstration of T.cruzi in blood or tissues of infected animals
- Examination of wet film and stained blood smear for Trypanosomes.
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Participants