Tsetse Flies carried by Railway Trains in Kenya Colony

Abstract

Railway trains running through tsetse-infested country between Mombasa and Nairobi in Kenya Colony carry G. longipennis, G. pcdlidipes and G. brevipalpis on to stock-farming areas beyond the natural limit of the fly belt, thus being largely responsible for outbreaks of animal trypanosomiasis and a reluctance on the part of European, Asian and African settlers to develop the land, affected by this form of fly dispersal, to its full capacity.The country through which the trains travel is described together with an account of a survey of the fly distribution.Tabulated figures are given of the monthly totals of tsetses collected from passenger and goods trains by teams of fly boys posted at Emali and Sultan Hamud railway stations about 17 and 25 miles respectively outside the fly belt towards Nairobi More than 24,000 flies were collected over a period of one year and many, not collected by the de-flying teams, were carried up-country even as far as Nairobi, 101 miles from the fly belt.Tsetses were collected from inside passenger trains, but very much larger numberswere taken from the outer surfaces and undercarriages of goods trucks.Reference is also made to the rôle of motor traffic, especially when in convoy in the dispersal of tsetses.The incidence of animal trypanosomiasis along the line of the railway is dealt with and the association of the disease with tsetses carried by trains is supported by results of laboratory experiments on the transmissibility of Trypanosoma congolense, T. vivax and T. brucei by the three species of flies concerned.Bush-clearing on stock farms outside the fly belt will not protect the cattle from infection carried by flies brought by trains but bush-clearing in specified localities of fly concentration in the infested country is recommended as a measure to reduce the numbers now attracted to trains. It is considered that the spraying of trains will bring considerable relief to farmers ; but, so far, no suitable spraying apparatus has been devised nor has a reasonably cheap insecticide been found for this purpose.