Sleeping sickness: a tale of two diseases.
ABSTRACT Sleeping sickness presents clinically as two distinct diseases, reflecting the fact that two very different trypanosomes are responsible. The African Rift separating East and West Africa defines the distribution of the two diseases. In this review, Susan Welburn, Eric Fèvre, Paul Coleman, Martin Odiit and Ian Maudlin discuss the biology and distribution of these two diseases in relation to the evolution of hominids in Africa.
Article: Detection and characterization of Wolbachia infections in laboratory and natural populations of different species of tsetse flies (genus Glossina).[show abstract] [hide abstract]
ABSTRACT: BACKGROUND: Wolbachia is a genus of endosymbiotic α-Proteobacteria infecting a wide range of arthropods and filarial nematodes. Wolbachia is able to induce reproductive abnormalities such as cytoplasmic incompatibility (CI), thelytokous parthenogenesis, feminization and male killing, thus affecting biology, ecology and evolution of its hosts. The bacterial group has prompted research regarding its potential for the control of agricultural and medical disease vectors, including Glossina spp., which transmits African trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. RESULTS: In the present study, we employed a Wolbachia specific 16S rRNA PCR assay to investigate the presence of Wolbachia in six different laboratory stocks as well as in natural populations of nine different Glossina species originating from 10 African countries. Wolbachia was prevalent in Glossina morsitans morsitans, G. morsitans centralis and G. austeni populations. It was also detected in G. brevipalpis, and, for the first time, in G. pallidipes and G. palpalis gambiensis. On the other hand, Wolbachia was not found in G. p. palpalis, G. fuscipes fuscipes and G. tachinoides. Wolbachia infections of different laboratory and natural populations of Glossina species were characterized using 16S rRNA, the wsp (Wolbachia Surface Protein) gene and MLST (Multi Locus Sequence Typing) gene markers. This analysis led to the detection of horizontal gene transfer events, in which Wobachia genes were inserted into the tsetse flies fly nuclear genome. CONCLUSIONS: Wolbachia infections were detected in both laboratory and natural populations of several different Glossina species. The characterization of these Wolbachia strains promises to lead to a deeper insight in tsetse flies-Wolbachia interactions, which is essential for the development and use of Wolbachia-based biological control methods.BMC Microbiology 01/2012; 12 Suppl 1:S3. · 3.04 Impact Factor
Article: Scrutinizing the mechanisms underlying the induction of anemia of inflammation through GPI-mediated modulation of macrophage activation in a model of African trypanosomiasis.[show abstract] [hide abstract]
ABSTRACT: In animal trypanosomiasis the severity of infection is reflected by the degree of anemia which resembles anemia of inflammation, involving a skewed iron homeostasis leading to iron accumulation within the reticuloendothelial system. Myeloid cells (M cells) have been implicated in the induction and maintenance of this type of anemia and modulation of M cells through the main trypanosome-derived glycosylphosphatidylinositol (GPI)-anchor could attenuate both anemia and trypano-susceptibility in Trypanosoma brucei-infected mice. Herein the GPI-based treatment, allowing a straightforward comparison between trypanotolerance and susceptibility in T. brucei-infected C57Bl/6 mice, was further adopted to scrutinize mechanisms/pathways underlying trypanosome-elicited anemia. Hereby, the following interlinkable observations were made in GPI-based treated (GBT) T. brucei-infected mice: (i) a reduced inflammatory cytokine production and increased IL-10 production associated with alleviation of anemia and restoration of serum iron levels, (ii) a shift in increased liver expression of iron storage towards iron export genes, (iii) increased erythropoiesis in the bone marrow and extramedullar sites (spleen) probably reflecting a normalized iron homeostasis and availability. Collectively, our results demonstrate that reprogramming macrophages towards an anti-inflammatory state alleviates anemia of inflammation by normalizing iron homeostasis and restoring erythropoiesis.Microbes and Infection 02/2010; 12(5):389-99. · 3.10 Impact Factor
Article: Constraints to estimating the prevalence of trypanosome infections in East African zebu cattle.[show abstract] [hide abstract]
ABSTRACT: In East Africa, animal trypanosomiasis is caused by many tsetse transmitted protozoan parasites including Trypanosoma vivax, T. congolense and subspecies of T. brucei s.l. (T. b. brucei and zoonotic human infective T. b. rhodesiense) that may co-circulate in domestic and wild animals. Accurate species-specific prevalence measurements of these parasites in animal populations are complicated by mixed infections of trypanosomes within individual hosts, low parasite densities and difficulties in conducting field studies. Many Polymerase Chain Reaction (PCR) based diagnostic tools are available to characterise and quantify infection in animals. These are important for assessing the contribution of infections in animal reservoirs and the risk posed to humans from zoonotic trypanosome species. New matrices for DNA capture have simplified large scale field PCR analyses but few studies have examined the impact of these techniques on prevalence estimations. The Whatman FTA matrix has been evaluated using a random sample of 35 village zebu cattle from a population naturally exposed to trypanosome infection. Using a generic trypanosome-specific PCR, prevalence was systematically evaluated. Multiple PCR samples taken from single FTA cards demonstrated that a single punch from an FTA card is not sufficient to confirm the infectivity status of an individual animal as parasite DNA is unevenly distributed across the card. At low parasite densities in the host, this stochastic sampling effect results in underestimation of prevalence based on single punch PCR testing. Repeated testing increased the estimated prevalence of all Trypanosoma spp. from 9.7% to 86%. Using repeat testing, a very high prevalence of pathogenic trypanosomes was detected in these local village cattle: T. brucei (34.3%), T. congolense (42.9%) and T. vivax (22.9%). These results show that, despite the convenience of Whatman FTA cards and specific PCR based detection tools, the chronically low parasitaemias in indigenous African zebu cattle make it difficult to establish true prevalence. Although this study specifically applies to FTA cards, a similar effect would be experienced with other approaches using blood samples containing low parasite densities. For example, using blood film microscopy or PCR detection from liquid samples where the probability of detecting a parasite or DNA molecule, in the required number of fields of view or PCR reaction, is less than one.Parasites & Vectors 01/2010; 3:82. · 2.94 Impact Factor