Investigations on the transmissibility of Trypanosoma congolense by the tsetse fly Glossina morsitans morsitans during its development in a mammalian host

Abstract

Experiments were conducted to investigate the effect of the developmental stage of a monomorphic T. congolense IL1180 strain, in a vertebrate host, on its transmissibility by the tsetse fly Glossina morsitans morsitans Westwood (Diptera: Glossinidae). Batches of 160 male teneral tsetse flies were given a single bloodmeal on mice infected with this T. congolense strain 4, 5, 6, 7 or 10 days post-infection. The proportion of infected flies in each of those batches showed that the stage of development of the trypanosome does affect the proportion of flies that develop a mature or immature infection with immature and mature infection rates of flies infected on days 5 or 10 significantly higher. The proportion of infected flies was not affected by the parasitaemia at the moment of infection. Results show that tsetse flies can become infected at any phase of the development of the T. congolense IL 1180 strain but the ease with which trypanosomes develop in the fly depends on the phase in the parasite's development in the host. Those observations suggest that in analogy with the pleomorphic T. brucei s.l. adaptation of the monomorphic T. congolense to development in the fly may also determine the parasite's transmissibility. Moreover, the findings stress the importance of standardising experiments in which the vectorial capacity of tsetse flies is determined and compared.

A gene expression comparison of Trypanosoma brucei and Trypanosoma congolense in the bloodstream of the mammalian host reveals species-specific adaptations to density-dependent development

“…Finally, T . congolense isolated at peak parasitaemia may be more able to infect tsetse flies than those during the ascending phase [ 49 ] though this has not been the observation in all studies[ 50 ]. All of these observations argue for a specific adaptation for transmission in T .…”

A Leap Into the Unknown – Early Events in African Trypanosome Transmission

“…Reports of morphological heterogeneity during infections exist [74,75] but T. congolense lacks a morphologically stumpy form, and there is conflicting evidence whether tsetse infectivity correlates with infection stage [75]. Nonetheless, mitochondrial activity is greater in T. congolense and T. vivax bloodstream forms than in T. brucei slender forms [76], and evidence suggests that T. congolense has a different strategy to T. brucei to prepare for transmission.…”

A Novel qPCR Assay for the Detection of African Animal Trypanosomosis in Trypanotolerant and Trypanosusceptible Cattle Breeds

“…It is known that different Glossinidae have diverse vector competences for different trypanosome species [35], [36]. G. morsitans submorsitans is regarded as a good vector for T. congolense Savannah [37], [38]. An in-depth vector and host surveillance program in this area would be helpful to shed more light on tsetse type abundance and T. congolense Savannah infections.…”