Sub genus : Trypanozoon

Trypanosoma bruce

Location and host

• These parasites are found in blood of cattle, sheep, goat, horse, donkey, camel, pig, dog and cat.
• Vector of this parasite : Tabanus , Stomoxys.

Morphology

• Pleomorphic in form and ranges from long and selender upto 42 µm to short and stumpy; 12-26 µm.
• Undulating membrane is conspicuous
• Kinetoplast is small and sub terminal
• Posterior end is pointed
• In slender form, kinetoplast is upto 4 µm from posterior end, usually drawn out, tapering to points and had well developed free flagellum.
• In stumpy form, flagellum is either short or absent. Posterior end is broad and rounded with kinetoplast almost terminal.
• Intermediate form has blunt posterior end and moderately long flagellum.
• In fresh unmixed blood films, organism move rapidly within small areas of microscopic field.

Life cycle

• Tse-tse flies ingest trypanosomes in blood or lymph while feeding on an infected host.
• Trypanosomes lose their glycoprotein surface coat, becomes elongated and multiply in mid gut before migrating to salivary glands.
• There, they undergo transformation, loosing trypanomastigote form and acquire epimastigote form
• After further multiplication of epimastigote, they transform again into small typically trypomastigote form with glycoprotein surface coat. These are called metacyclic trypanosomes and are infective for next host.
• Metacyclic trypanosomes are inoculated into skin when vector feeds on host.
• At site of inoculation, metacyclic forms multiply locally as typical blood forms, producing a raised cutaneous inflammatory swelling called ‘chancre’.
• They enter blood stream and multiply resulting in parasitemia. These are detachable in peripheral blood.

Transmission

• Transmission is mainly through bite of vector flies
• Some flies may be transmitted through contact

Pathogenesis/ Clinical signs

• Disease is usually more chronic in cattle. Animal survive for several months and may recover.
• In cattle, major clinical signs are anemia, generalized enlargement of superficial lymph nodes, lethargy and progressive loss of body condition
• Intermittent fever and loss of appetite
• Pregnant animals may abort or give birth to weak offsprings
• In terminal stage, animals become extremely weak, lymph nodes reduced in size and there is often a jugular pulse.

Diagnosis

• Clinical signs, though indicative but not pathognomonic.
• Confirmatory diagnosis is through demonstration of trypanosomes in blood
• Serological test such as indirect fluorescent Ab test and ELISA.

Treatment and control

• Isometamidium @ 0.25-1 mg /kg intramuscular and diminazene aceturate @ 3-10 mg/kg intramuscular are drug of choice. Quinapyramine sulphate @ 3-5 mg/kg intramuscular only in horse
• Use of fly repellant and insecticide Suramin @ 7-10 mg/kg I/M or I/V in horse and camel
• Control of breeding of insect vectors