Abstract

Rabies virus (RABV) is enzootic throughout Africa, with the domestic dog (Canis familiaris) being the principal vector. Dog rabies is estimated to cause 24,000 human deaths per year in Africa, however, this estimate is still considered to be conservative. Two sub-Saharan African RABV lineages have been detected in West Africa. Lineage 2 is present throughout West Africa, whereas Africa 1a dominates in northern and eastern Africa, but has been detected in Nigeria and Gabon, and Africa 1b was previously absent from West Africa. We confirmed the presence of RABV in a cohort of 76 brain samples obtained from rabid animals in Ghana collected over an eighteen-month period (2007–2009). Phylogenetic analysis of the sequences obtained confirmed all viruses to be RABV, belonging to lineages previously detected in sub-Saharan Africa. However, unlike earlier reported studies that suggested a single lineage (Africa 2) circulates in West Africa, we identified viruses belonging to the Africa 2 lineage and both Africa 1 (a and b) sub-lineages. Phylogeographic Bayesian Markov chain Monte Carlo analysis of a 405 bp fragment of the RABV nucleoprotein gene from the 76 new sequences derived from Ghanaian animals suggest that within the Africa 2 lineage three clades co-circulate with their origins in other West African countries. Africa 1a is probably a western extension of a clade circulating in central Africa and the Africa 1b virus a probable recent introduction from eastern Africa. We also developed and tested a novel reverse-transcription loop-mediated isothermal amplification (RT-LAMP) assay for the detection of RABV in African laboratories. This RT-LAMP was shown to detect both Africa 1 and 2 viruses, including its adaptation to a lateral flow device format for product visualization. These data suggest that RABV epidemiology is more complex than previously thought in West Africa and that there have been repeated introductions of RABV into Ghana. This analysis highlights the potential problems of individual developing nations implementing rabies control programmes in the absence of a regional programme.

Highlights

  • Viruses belonging to the genus Lyssavirus, family Rhabdoviridae, cause the disease rabies

  • We confirmed the presence of Rabies virus (RABV) in a cohort of 76 brain samples obtained from rabid animals in Ghana collected from 2007 to 2009

  • Our analysis of the genetic sequences obtained confirmed all viruses to be RABV, unlike previous studies we detected two sub-Saharan African RABV viruses (Africa 1 and 2) in this cohort, which included a single virus previously undetected in West Africa

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Summary

Introduction

Viruses belonging to the genus Lyssavirus, family Rhabdoviridae, cause the disease rabies. Sylvatic rabies is reported in a number of wildlife hosts, in southern Africa [2,3,4,5]. Between 1970 and 1974, an average of 72 cases of canine rabies were reported annually throughout the country [10]. Since 1981 there have been no further published reports of rabies in Ghana, and rabies viruses from the country have not been included in phylogenetic analyses of rabies in Africa [13,14]. ‘suspect’ human rabies cases are rarely confirmed using a laboratory-based diagnosis, relying solely on a clinical diagnosis [9]

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