Abstract
Trypanosoma brucei gambiense, transmitted by the tsetse fly, is the main causative agent of Human African trypanosomosis in West Africa and poses a significant health risk to 70 million people. Disease progression varies depending on host immunity, but usually begins with a haemo-lymphatic phase, followed by parasite invasion of the central nervous system.In the current study, the tropism of T. b. gambiense 1135, causing a low level chronic ‘silent’ infection, was monitored in a murine model using bioluminescence imaging and PCR. A tropism to the reproductive organs, in addition to the central nervous system, after 12–18 months of infection was observed. Bioluminescent analysis of healthy females crossed with infected males showed that 50%, 62.5% and 37.5% of the female mice were subsequently positive for parasites in their ovaries, uteri and brain respectively. Although PCR confirmed the presence of parasites in the uterus of one of these mice, the blood of all mice was negative by PCR and LAMP. Subsequently, bioluminescent imaging of the offspring of infected female mice crossed with healthy males indicated parasites were present in the reproductive organs of both male (80%) and female (60%) offspring.These findings imply that transmission of T. b. gambiense 1135 occurs horizontally, most probably via sexual contact, and vertically in a murine model, which raises the possibility of a similar transmission in humans. This has wide reaching implications. Firstly, the observations made in this study are likely to be valid for wild animals acting as a reservoir for T. b. gambiense. Also, the reproductive organs may act as a refuge for parasites during drug treatment in a similar manner to the central nervous system. This could leave patients at risk of a relapse, ultimately allowing them to act as a reservoir for subsequent transmission by tsetse and possibly, horizontally and vertically.
Highlights
Human African trypanosomosis (HAT) is caused by the protozoan parasite Trypanosoma brucei gambiense in West and Central Africa and T. b. rhodesiense in East Africa
Using a strain of T. b. gambiense transfected with a gene for luminescent detection that causes a chronic infection with very low parasitaemia, we found that the parasite is capable of entering the reproductive organs of both male and female mice
These experiments demonstrated that T. b. gambiense 1135 is transmitted both horizontally, most probably by sexual contact, and vertically in mice
Summary
Human African trypanosomosis (HAT) is caused by the protozoan parasite Trypanosoma brucei gambiense in West and Central Africa and T. b. rhodesiense in East Africa. It has recently been established that HAT may lead to various disease states, including a latent state characterised by a chronic, asymptomatic stage 1 and no progression to stage 2, or asymptomatic stage 2 [10,11]. Such variation in disease progression is likely to be affected by host genetics [10,12,13]
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