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Comparison of the transmissibility of Trypanosoma congolense strains, isolated in a trypanosomiasis endemic area of eastern Zambia, by Glossina morsitans morsitans

Published online by Cambridge University Press:  24 May 2006

J. MASUMU ,
T. MARCOTTY ,
N. NDELEDJE ,
C. KUBI ,
S. GEERTS ,
J. VERCRUYSSE ,
P. DORNY  and
P. VAN DEN BOSSCHE
J. MASUMU
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium
T. MARCOTTY
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium
N. NDELEDJE
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium
C. KUBI
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium
S. GEERTS
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium
J. VERCRUYSSE
Affiliation:
Ghent University, Vakgroep Virologie, Parasitologie en Immunologie, Salisburylaan 133, B-9820 Merelbeke, Belgium
P. DORNY
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium Ghent University, Vakgroep Virologie, Parasitologie en Immunologie, Salisburylaan 133, B-9820 Merelbeke, Belgium
P. VAN DEN BOSSCHE
Affiliation:
Institute of Tropical Medicine, Animal Health Department, Nationalestraat 155, B-2000 Antwerp, Belgium University of Pretoria, Department of Veterinary Tropical Diseases, Onderstepoort, South Africa
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Abstract

Transmission experiments were conducted to compare the transmissibility of genetically different Trypanosoma congolense (Savannah subgroup) strains isolated from cattle in a trypanosomiasis endemic area of eastern Zambia. A total of 17 strains were compared. Three strains were extremely virulent with a short pre-patent period, high parasitaemia and a short median survival time (between 5 and 9 days) in mice. The remainder of the strains belonged to the moderate (6 strains) or low (8 strains) virulence categories with median survival times between 10 and 30 days and >30 days, respectively. Batches of 40 teneral Glossina morsitans morsitans (Diptera: Glossinidae) were offered a single bloodmeal on mice infected with one of those strains. Flies were dissected to determine their infection status 21 days later. The proportion of flies with procyclic and metacyclic infections differed significantly between trypanosome strains and were significantly higher in flies infected with extremely virulent strains (P=0·033 and P=0·016 for the differences in the procyclic infection rate of strains with moderate and low virulence, respectively and P=0·005 and P=0·019 for the differences in the metacyclic infection rate of strains with moderate and low virulence, respectively). On the other hand, moderately virulent strains had, in general, higher procyclic and metacyclic infection rates compared to low virulent strains. But the differences were not significant (P>0·05). The outcome of those experiments shows clear differences in transmissibility of trypanosome strains associated with their virulence. This observation confirms the theory for the evolution and maintenance of virulence in a parasite population and may explain the persistence of virulent trypanosome strains in a susceptible host population.

Keywords

Trypanosoma congolenseGlossina morsitans morsitanstransmissionvirulenceZambia
Type
Research Article
Information
Parasitology , Volume 133 , Issue 3 , September 2006 , pp. 331 - 334
Copyright
2006 Cambridge University Press

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