TABLE OF CONTENTS
Trypanosoma brucei (African Trypanosome): Morphology, Transmission, Pathogenesis, and Treatment
Trypanosoma brucei is a hemoflagellate protozoan parasite of major veterinary importance and one of the causative agents of African animal trypanosomiasis (Nagana). It infects a wide range of domestic and wild animals and is transmitted biologically by tsetse flies (Glossina spp.). The parasite primarily inhabits the bloodstream but may also invade extravascular tissues, contributing to chronic disease and significant economic losses in endemic regions of Africa.
This article provides a concise veterinary overview of Trypanosoma brucei, including its taxonomy, morphology, transmission, development in the vector, pathogenesis, clinical signs, and treatment.
Parasite Overview
- Hosts: Cattle, horses, donkeys, sheep, goats, camels, dogs, pigs, cats, and wild game animals such as antelopes (reservoir hosts)
- Predilection site: Blood; it is also found extravascularly in the myocardium, CNS, and reproductive tract.
- Vector: Glossina spp. (tsetse fly)
- Disease Caused: African animal trypanosomiasis (Nagana)
- Infective stage: Metacyclic trypomastigote
Taxonomical Classification
- Kingdom: Protista
- Phylum: Euglenozoa
- Class: Kinetoplastea
- Order: Trypanosomatida
- Family: Trypanosomatidae
- Genus: Trypanosoma
- Subgenus: Trypanozoon
- Species: Trypanosoma brucei
- Common Name: African trypanosome
Morphology
T. brucei is pleomorphic; it may be long and slender or short and stumpy. Sometimes, intermediate forms may occur. The undulating membrane is prominent, and the kinetoplast is small and subterminal.
In the slender form, the posterior end is pointed and has a well-developed free flagellum, whereas in the stumpy and intermediate forms, the posterior end is broad and rounded, and the free flagellum is either short or moderately long.
Transmission and Development
Tsetse flies ingest trypanosomes in the blood or lymph while feeding on an infected animal. The ingested trypanosomes first lose their surface coat, become elongated, and multiply in the midgut of the fly.
Thereafter, they migrate to the salivary glands, where they transform into the epimastigote form and undergo further multiplication. After multiplication, the epimastigotes transform again into the trypomastigote form with a surface coat. These are the infective forms, called metacyclic trypanosomes, which are inoculated into a new host when the tsetse fly feeds.
Pathogenesis and Clinical Signs
At the site of inoculation, the metacyclic forms multiply locally and produce a raised cutaneous inflammatory swelling called a chancre.
The disease is usually more chronic in cattle, and affected animals may survive for several months and recover.
Affected animals commonly exhibit intermittent fever, progressive anemia, enlarged superficial lymph nodes, lethargy, weight loss, reduced appetite, weakness, decreased milk production or work performance, and ventral edema.
Treatment
- Isometamidium: 0.25–1 mg/kg IM
- Diminazene aceturate: 3–10 mg/kg IM
Treatment should be selected based on the animal species, disease stage, and local drug resistance patterns. Supportive therapy may also be required in severely affected animals.
