Arthropod vectors Tsetse flies

Tsetse fliesAuthor: Dr Reginald De DekenLicensed under a Creative Commons Attribution license.

IMPORTANCETsetse flies represent a key constraint for food security in the 37 sub-Saharan African countries where tsetse flies are present. Tsetse flies are the biological vectors of several trypanosomes affecting livestock and of two trypanosome species, Trypanosoma brucei gambiense and T.b.rhodesiense, causing respectively in eastern and southern Africa a chronic form and in Western and Central Africa an acute form of human sleeping sickness. The distribution of sleeping sickness areas has a focal nature and the localisation of the actual areas fluctuates over the course of time. Important vectors for human African trypanosomosis are: all subspecies of Glossina fuscipes and of G.palpalis, G.pallicera pallicera, G.swynnertoni, G. morsitans centralis, G. morsitans morsitans and G.pallidipes.

Contrary to human African trypanosomosis, almost all tsetse flies can transmit the trypanosomes responsible for animal trypanosomosis and the disease has a wide geographic distribution.

Distribution of tsetse and cattle

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Arthropod vectors Tsetse flies

Through the disease they transmit, these trypanosomes hamper livestock keeping or genetic improvement of indigenous breeds and an efficient use of animal traction. The economic cost of trypanosomosis will largely depend on the livestock production system (the type of animal bred; trypanotolerant or susceptible – draught, dairy or beef animals) and is inversely related to the endemicity of the disease (epidemics occurring essentially when livestock is encroaching on undeveloped areas). According to Kristjanson P.M. (1999) the disease costed African livestock producers and consumers at that time an estimated $1340 million annually, without including indirect livestock benefits such as manure and traction. The most striking direct effects of the disease are observed in the field of milk production, calving rate and mortality among calves and draught animals. Apart from these direct economic effects of the disease, there are also considerable indirect losses due to unbalanced land use and settlement patterns, difficulties to integrate livestock breeding and agriculture, reduced use of draught power and massive expenditures on trypanocidal drugs in tsetse infested areas. On top of this, resistance to trypanocidal drugs is spreading. The highest losses from animal trypanosomosis currently occur in areas with high cattle population densities on the margins of the tsetse distribution and where animal traction is an important component of farming systems (Shaw, 2009).

Available multimedia

Videos: A 45 min lasting video “Survival – Deadliest disease” produced by rockhopper TV for BBC can be visualised or downloaded at

http://www.rockhopper.tv/films/detail/survival-the-deadliest-disease

Some videos on the zoonotic form of the disease caused by T.brucei rhodesiense may be consulted on the ICONZ website:

http://www.iconzafrica.org/videos/sleeping_sickness_march_2010.mov or http://www.iconzafrica.org/videos/sleeping_sickness_long.mov

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