Does tick-borne relapsing fever have an animal reservoir in East Africa?

Tick-borne relapsing fevers (TBRF) are caused by infection with Borrelia spirochetes and transmitted to humans by ticks. All except East African TBRF, caused by Borrelia duttonii, are known zoonoses. This widespread, endemic and pathogenic infection has only been found in humans and the Ornithodoros sp. soft tick vectors. We investigated the role of domestic animals as possible reservoirs of infection in a TBRF endemic region. Tick infestations in households and pigpens were investigated in the villages near Mvumi hospital in central Tanzania. Blood from chickens and pigs was examined by PCR and flagellin gene sequencing was performed on any Borrelia sp. infections detected. A mark-recapture experiment investigated tick movement between pigpens and houses. The acceptability of chickens as tick hosts was also investigated. Tick infestation of the 122 houses investigated was high (47%). Pigpens also were tick infested (16%) and were more likely to be so if they were located close to tick infested households (p < 0.001). PCR screening of peripheral blood found Borrelia infections in both chickens and pigs (11% and 8.9% respectively). Sequencing of a subset of positive samples revealed that the amplified Borrelia sp. flagellin gene fragments shared greatest homology with B. duttonii. In a mark-recapture experiment, ticks released in pigpens were recaptured inside human bedrooms. When offered chickens as hosts, over 20% of ticks fed. For the first time in East Africa, we record natural infections of Borrelia in domestic animals and show that tick populations may act as bridging vectors between animals and humans. These results, from villages where B. duttonii is already known to be prevalent and a major cause of illness in humans, and where it has been found at high levels in ticks, strongly support the case that it is a zoonosis. This increases understanding of the epidemiology and control of this important but neglected human disease

Immunogenic salivary proteins of Triatoma infestans\textit {Triatoma infestans}

$\textit {Background:}$ Triatomines are vectors of $\textit {Trypanosoma cruzi}$, the etiological agent of Chagas disease in Latin America. The most effective vector, $\textit {Triatoma infestans}$, has been controlled successfully in much of Latin America using insecticide spraying. Though rarely undertaken, surveillance programs are necessary in order to identify new infestations and estimate the intensity of triatomine bug infestations in domestic and peridomestic habitats. Since hosts exposed to triatomines develop immune responses to salivary antigens, these responses can be evaluated for their usefulness as epidemiological markers to detect infestations of $\textit {T. infestans}$. $\textit {Methodology/Principal Findings:}$ $\textit {T. infestans}$ salivary proteins were separated by 2D-gel electrophoresis and tested for their immunogenicity by Western blotting using sera from chickens and guinea pigs experimentally exposed to $\textit {T. infestans}$. From five highly immunogenic protein spots, eight salivary proteins were identified by nano liquid chromatography-electrospray ionization-tandem mass spectrometry (nanoLC-ESI-MS/MS) and comparison to the protein sequences of the National Center for Biotechnology Information (NCBI) database and expressed sequence tags of a unidirectionally cloned salivary gland cDNA library from $\textit {T. infestans}$ combined with the NCBI yeast protein sub-database. The 14.6 kDa salivary protein [gi|149689094] was produced as recombinant protein (r$\it Ti$SP14.6) in a mammalian cell expression system and recognized by all animal sera. The specificity of rTiSP14.6 was confirmed by the lack of reactivity to anti-mosquito and anti-sand fly saliva antibodies. However, r$\it Ti$SP14.6 was recognized by sera from chickens exposed to four other triatomine species, $\textit {Triatoma brasiliensis, T. sordida, Rhodnius prolixus}$, and $\textit {Panstrongylus megistus}$ and by sera of chickens from an endemic area of $\textit {T. infestans}$ and Chagas disease in Bolivia. $\textit {Conclusions/Significance:}$ The recombinant r$\it Ti$SP14.6 is a suitable and promising epidemiological marker for detecting the presence of small numbers of different species of triatomines and could be developed for use as a new tool in surveillance programs, especially to corroborate vector elimination in Chagas disease vector control campaigns