Role of Tsetse Fly in Transmission of Trypanosomiasis

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In Pakistan round about 60 to 70% people directly or indirectly are involved with livestock industry for their livelihood. Livestock population is providing basic necessities for people related to dairy industry. Livestock industry is the backbone of rural population because small dairy holders totally depend upon the animals. They earn their livelihood by selling animals, their products and byproducts. Hence we can say that livestock plays central role in social economy of Pakistan. Now a days various infectious diseases like bacterial, viral and parasitic are the major threat to livestock industry. Among these protozoan diseases like thelieriasis, babesiosis, leshmaniasis, trypanosomiasis, are of economic importance. Trypanosomiasis is transmitted by the bite of tsetse fly which causes heavy economic losses in animals including debilitating condition, anemia, rise in body temperature, cutaneous eruptions, neurological conditions and death.

Clinical signs

Trypanosomiasis disease caused by protozoan parasitic species Trypanosoma evansi, Trypanosoma cruzi (chages disease), Trypanosoma brucie (sleeping sickness). This disease has acute, sub-acute and chronic forms. Trypanosoma parasite causes disease in almost all livestock species like cattle and buffalo, horse, camel and dogs. Trypanosomosis is transmitted by the bite of infected tsetse fly. Clinical signs includes arise in temperature up to 105 to 106oF, anorexia, anemia, weakness, enlargement of superficial lymph nodes, lacrimation, progressive weight loss, abortion, delayed estrus, still birth.  Oedema of different body parts due to increase in vascular permeability is the major indication of this disease. In chronic cases animals will show keratitis, swelling of tongue, nervous signs (convulsions, ataxia, and blindness) and ultimately death. Animals show petechial haemorraghes on conjunctiva and decrease in circulatory volume of blood. In camel disease pattern is intermittent fever with anemia, emaciation and edema of different body parts. In dogs trypanosomiasis periodic fever including decrease in appetite, edema and corneal opacity.

Life cycle

Life cycle of Trypanosomiasis consists of different stages in vector (tsetse fly) and host (animals plus human being). When infected tsetse fly bite to the host it transfers trypomastigotes stage in it. Trypomastigotes further carried to body fluids of host where it multiplies  via binary fission in blood, lymph and spinal fluids. During infected blood meal from host trypomastigote stage is sucked by tsetse fly where it changes to procyclic trypomastigote stage. After multiplication in fly midgut, Procyclic trypomastigote transform into epimastigote stage. In salivary gland of fly epimastigote stage multiply and changes to metacyclic trypomastigotes that  transfer to host during blood feeding. In this way life cycle of trypanosomiasis continues onward.


The trypanosoma that is extracellular parasite can be identified easily through blood smear easily. The treatment protocol followed to control this disease is the use of Quinapyramine sulphate @ 4mg/kg body weight. Tribexin® is used in cattle as well horses for treatment and prophylactic purposes @ 3.5 to 4 mg/kg of body weight. Use of pain killer like Loxin® helps in reduction of fever. If condition is more chronic then use of intravenous hematinic solutions in order to achieve desired hemoglobin level in blood. Multivitamins powder like Vito Mineral T® at @ of 100gm/day/animal helps to recover the animals from infection.

Prophylactic Measures

The main strategy to control trypanosomiasis is to destroy the reservoirs of infection in order to minimize the tsetse fly population.

Keep the environment neat and clean to avoid propagation of fly’s population.

Regular screening of people at risk helps in identification of patients at early stage.

Use of Quinapyramine sulphate at regular intervals can minimize the chance of trpanosomiasis.

Hence it is concluded that trypanosomiasis is the major threat in almost all species of livestock population in summer season due to hot and humid conditions. So we can minimize the risk of trypanosomiasis disease in terms of health, wealth and reproductive losses by keeping in mind the above mentioned control strategies .

This article is collectively authored by Dr. Muhammad Rashid Fayyaz1, Dr. Asghar Abbas2, Dr. Rao Zahid Abbas3, Dr. Imran Ali1, Dr. Muhammad Mohsin1. 1. M. Phil Scholar in Department of Parasitology, University of Agriculture Faisalabad. 2. Ph. D Scholar in Department of Parasitology, University of Agriculture Faisalabad. 3. Associate Professor in Department of Parasitology, University of Agriculture Faisalabad.


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