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The cyclical transmission of strains of Trypanosoma congolense and T. vivax resistant to normal therapeutic doses of trypanocidal drugs

Published online by Cambridge University Press:  06 April 2009

A. R. Gray
Affiliation:
The Nigerian Institute for Trypanosomiasis Research, Vom, Benue-Plateau State, Nigeria
C. J. Roberts
Affiliation:
The Nigerian Institute for Trypanosomiasis Research, Vom, Benue-Plateau State, Nigeria

Extract

Two strains of T. congolense and two strains of T. vivax, resistant to normal therapeutic doses of trypanocidal drugs, were transmitted by G. morsitans and G. tachinoides through series of cattle in the absence of drugs to assess the transmissibility of the trypanosomes by tsetse flies and the stability of drug resistance in the organisms during cyclical development.

The characteristics of both strains of T. vivax and one strain of T. congolense were typical of the species, but the infectivity of the second strain of T. congolense for laboratory animals was abnormally low.

The transmissibility of the trypanosomes was assessed on the bases of the infection rates in tsetse flies used to transmit the strains and the periods required for the development of the trypanosomes in the flies and bovine hosts. The transmissibilities of both strains of T. vivax and the first strain of T. congolense were normal by comparison with data obtained by cyclically transmitting non-resistant trypanosomes of the same species, but the period required for the development of the second strain of T. congolense in tsetse flies was abnormally long.

There was no loss of drug resistance in any of the strains examined in the experiments. A strain of T. congolense retained resistance to diminazene aceturate at a dose rate of 7-0 mg/kg, homidium chloride at 2-0 mg/kg, quinapyramine sulphate at 4-4 mg/kg and isometamidium chloride at 0-5 mg/kg during a series of eight transmissions by tsetse flies in a period of 376 days.

Type
Research Article
Copyright
Copyright © Cambridge University Press 1971

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