Evolutionary History and Phylogeography of Rabies Viruses Associated with Outbreaks in Trinidad

Abstract

Bat rabies is an emerging disease of public health significance in the Americas. The Caribbean island of Trinidad experiences periodic outbreaks within the livestock population. We performed molecular characterisation of Trinidad rabies virus (RABV) and used a Bayesian phylogeographic approach to investigate the extent to which outbreaks are a result of in situ evolution versus importation of virus from the nearby South American mainland. Trinidadian RABV sequences were confirmed as bat variant and clustered with Desmodus rotundus (vampire bat) related sequences. They fell into two largely temporally defined lineages designated Trinidad I and II. The Trinidad I lineage which included sequences from 1997–2000 (all but two of which were from the northeast of the island) was most closely related to RABV from Ecuador (2005, 2007), French Guiana (1990) and Venezuela (1993, 1994). Trinidad II comprised sequences from the southwest of the island, which clustered into two groups: Trinidad IIa, which included one sequence each from 2000 and 2007, and Trinidad IIb including all 2010 sequences. The Trinidad II sequences were most closely related to sequences from Brazil (1999, 2004) and Uruguay (2007, 2008). Phylogeographic analyses support three separate RABV introductions from the mainland from which each of the three Trinidadian lineages arose. The estimated dates for the introductions and subsequent lineage expansions suggest periods of in situ evolution within Trinidad following each introduction. These data also indicate co-circulation of Trinidad lineage I and IIa during 2000. In light of these findings and the likely vampire bat origin of Trinidadian RABV, further studies should be conducted to investigate the relationship between RABV spatiotemporal dynamics and vampire bat population ecology, in particular any movement between the mainland and Trinidad.

The Phylogeography of Rabies in Grenada, West Indies, and Implications for Control

“…The vampire bat ( Desmodus rotundus ), which is the main rabies reservoir on the neighboring island of Trinidad and several Latin American countries does not occur on Grenada [18] , [36] . Other bat species are lyssavirus reservoirs worldwide [37] and 13 species of insectivorous and fructivorous bats have been recorded in Grenada [38] .…”

“…These Caribbean variants are quite different from those circulating in mongooses in Asia [13] . In contrast, on the south Caribbean island of Trinidad, rabies circulates in vampire and other bat species, but rabies has not been reported in the Trinidadian mongoose population [18] .…”

The Serological Prevalence of Rabies Virus-Neutralizing Antibodies in the Bat Population on the Caribbean Island of Trinidad

“…In Trinidad, bat surveillance has traditionally targeted hematophagous bats with Desmodus species comprising the vast majority of tested bats [22,27]. However, the prevalence of RVNA in non-hematophagous bats found in this study suggests an expansion of rabies diagnostic testing to non-hematophagous species may be warranted to obtain a comprehensive picture of rabies host diversity and viral dynamics and ultimately determine the risk of transmission [31].…”

“…The island is enzootic for bat RABV which has been so far isolated from nine bat species [19,20]. Of these, the hematophagous Desmodus rotundus species is considered the most effective vector on account of its feeding practices [21] and to date, is the only bat directly implicated in transmission of the virus on the island [22]. Some earlier unconfirmed studies have suggested that apparently healthy bats could harbour and transmit RABV for extended periods [23][24][25][26], however to date this has not been conclusively proven by modern diagnostic methods.…”

“…In Trinidad viral isolation from bats has been rare with a rabies positivity proportion of 0.05% (two positive of 4399 tested between 1971 and 2015) obtained from samples acquired mainly through active surveillance in the bat population [27]. Despite the bias towards healthy bats inherent to this type of sampling, it has been suggested that this low proportion is a consequence of virus only being periodically imported from the South American mainland (as bats fly from mainland to island) causing vampire bat epizootics with occasional viral spill-over to the livestock population [22]. Nonetheless, over the last 50 years, despite the apparent low levels of RABV circulation in the bat population, five significant epizootic events have occurred on the island [28].…”