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Infectivity and virulence of Trypanosoma brucei metacyclics from Glossina morsitans morsitans salivary glands infected with tsetse DNA virus

Published online by Cambridge University Press:  19 September 2011

Walter G. Z. O. Jura  and
Leonard H. Otieno
Walter G. Z. O. Jura*
Affiliation:
International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
Leonard H. Otieno
Affiliation:
International Centre of Insect Physiology and Ecology (ICIPE), P.O. Box 30772, Nairobi, Kenya
*
* Author to whom correspondence should be addressed.
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Abstract

The pathogenicity of cyclically transmitted C16 clone 1 of Trypanosoma brucei metacyclics which developed within normal and hypertrophied DNA virus-infected salivary glands of Glossina morsitans morsitans was studied in the inbred, BALB/c mice. Microscopic examination of salivary glands obtained from G. m. morsitans with combined virus and T. brucei infections (i.e. the flies which transmitted the trypanosome infection to the test group of mice, group A) revealed that the glands comprised hyperplastic epithelial cells, some of which were fragmented, and numerous metacyclic trypanosomes. All the mice which contracted trypanosomiasis from G. m. morsitans with only T. brucei, i. e., the control mice (Group B; n=4) and the mice in the test group (n = 3) developed high parasitaemia and died. Repeated-measures analysis of variance using adjusted mean rate revealed that the mean prepatent periods and the mean times to death in both the control and the test groups of the BALB/c mice were not significantly different (P > 0.05). Analysis of log-transformed data fitted to a logistic growth model revealed that the rate of multiplication of T. brucei parasites in the blood of the test group BALB/c mice (r=2.373) was greater than in the control mice (r=0.808) and that the maximum carrying capacity was also attained earlier in the former group. These observations imply that the development of T. brucei metacyclics within hypertrophied salivary glands and their co-existence with the DNA virus particles might have enhanced their infectivity and virulence in the mice.

Résumé

La pathogénicité du clone 1 C16 (à transmission cyclique) des stades métacycliques de Trypanosoma brucei qui se sont developpés à l'intérieur des glandes salivaires normales et hypertrophiées infectées d'ADN viral de Glossina morsitans morsitans a été étudiée sur une lignée de souris, le BALB/c. L'examin microscopique des glandes salivaires obtenues sur G. m. morsitans porteuses d'infections mixtes virus et infections à T. brucei (cad les mouches ayant transmis l'infection à Trypanosoma au groupe test de souris, soit le group A) a révelé que les glandes abritaient des cellules épithéliales hyperplasiques dont certaines se présentaient en fragments et de nombreaux trypanosomes métacycliques. Toutes les souris ayant contracté la trypanosomiase à partir de G. m. morsitans avec les seuls T. brucei, cad les souris témoins (group B; n=4) et celles du groupe test (n=3) ont developpé une forte parasitémie et en sont mortes. L'analyse des mesures répétées de variance avec ajustement de moyennes a révelé que la période moyenne précédant la manifestation de la maladie et la période moyenne jusqu'au décès à la fois chez la groupe test et chez les témoins n'étaient pas significativement différentes (P > 0.05). L'analyse des données obtenues par transformation logarithmique et a justées à la courbe de croissance logistique a révelé que le taux de multiplication des parasites T. brucei dans le sang du groupe test BALB/c (r=2.373) était plus élevé que chez les souris témoins (r=0.808) et que la capacité maximum de charge était aussi atteinte plus tôt dans le premier groupe. Ces observations impliquent que le développement des T. brucei métacycliques à l'intérieur des glandes salivaires hypertrophiées et leur co-existence avec des particules virales d'ADN peuvent avoir modifié leur infectivité et leur virulence chez les souris.

Keywords

Trypanosoma bruceiGlossina morsitans morsitansDNA virusinfectivityvirulencepathogenicitymetacyclicsBALB/c micecyclical transmissionTrypanosoma bruceiGlossina morsitans morsitansADN viralinfectivitévirulencepathogenicitéstades métacycliquessouris BALB/ctransmission cyclique
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 15 , Issue 4-5 , October 1994 , pp. 551 - 556
Copyright
Copyright © ICIPE 1994

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