Antibodies against Lagos Bat Virus in Megachiroptera from West Africa

Abstract

To investigate the presence of Lagos bat virus (LBV)-specifi c antibodies in megachiroptera from West Africa, we conducted fl uorescent antibody virus neutralization tests. Neutralizing antibodies were detected in Eidolon helvum (37%), Epomophorus gambianus (3%), and Epomops buettikoferi (33%, 2/6) from Ghana. These fi ndings confi rm the presence of LBV in West Africa. Bats host a range of lyssaviruses, depending on their species and locality. The genus Lyssavirus is differentiated into 7 genetically divergent genotypes: classical rabies virus (genotype 1), Lagos bat virus (LBV; genotype 2), Mokola virus (MOKV; genotype 3), Duvenhage virus (genotype 4), European bat lyssavirus (genotypes 5 and 6), and Australian bat lyssavirus (genotype 7) (1). All but MOKV have been isolated from bats.LBV and MOKV are each distributed in Africa and are members of phylogroup 2 within the genus Lyssavirus (1). Because LBV isolates (2) from African bats are increasing, our goal was to determine the prevalence of virus neutralizing antibodies against LBV in bat populations in West Africa. The StudyBats were sampled in January and May 2007 at 6 sites in Ghana: the center of Accra (urban habitat); the wooded outskirts of Accra (savannah habitat); and forested habitats at Pra, Kibi, Adoagyiri, and Oyibi (a plantation with woodland/forest border). Bats were captured by using 6-18-m mist nets; roosting Eidolon helvum were captured by using nets on poles. A sample size of 59 would provide 95% confi dence of fi nding at least 1 LBV-seropositive bat in a large population (>5,000), given a seroprevalence of 5% and assuming random sampling (3). Species were identifi ed by using a dichotomous key (4). Captured bats were manually restrained and anesthetized by intravenous injection; ≈0.2-1.0 mL of blood was collected from the propatagial vein before the bat was released. Blood was centrifuged in the fi eld at ambient temperature at 3,000 rpm for 15 min. Serum was heat treated at 56°C for 30 min and frozen at -70°C.Two species, Epomophorus gambianus and E. helvum, were caught in suffi cient numbers (117 and 66, respectively) for reasonable inferences to be made about LBV seroprevalence rates (Table). A standard approach was used to calculate 95% confi dence intervals (CIs) for seroprevalence (3). Because of the relatively short distances between study sites and the likelihood of bats mixing between these sites, bats of each species were considered to belong to single populations. All but 3 E. helvum were derived from a colony in Accra, whereas E. gambianus were derived from all habitat types.Bat serum samples were tested for virus neutralizing antibody against classical rabies virus (challenge virus standard) by using a standard fl uorescent antibody virus neutralization (FAVN) test (5). Antibodies to LBV were measured by using a modifi ed FAVN test (6). Because positive bat antiserum from naturally infected bats was not available, for positive controls we used human rabies immunoglobulin, LBV-positive rabbit serum, and serum from mice vaccina...

Lagos bat virus transmission in an Eidolon helvum bat colony, Ghana

“…Hence, if this particular isolate, which had been used in most other serosurveys, were initially used as test virus for screening the Kumasi colony, presence of neutralizing antibodies would have been missed. Against the background of reported LBVNIG1956-based seroprevalences in E. helvum colonies from Kumasi, Accra, and Tanoboase in Ghana (Hayman et al, 2008(Hayman et al, , 2012, this is difficult to explain. Repeated testing of our serum samples, however, yielded the same results (data not shown).…”

“…On the other hand, this discrepancy could also be due to different cut-offs for seropositivity. While Hayman et al (2008Hayman et al ( , 2012 considered a reciprocal titre of >9 as seropositive, in our assay 1:10 is the starting dilution. Hence, low level VNAs would be missed.…”

Quantifying Antigenic Relationships among the Lyssaviruses

“…Such conservation in the phenotype of the key antigenic determinant of lyssaviruses is consistent with a low immune selective pressure upon lyssaviruses (9,14,24) in comparison with pathogens such as influenza virus that are under large selection pressure (42,52). Although low immune selective pressure could be expected from the natural history of RABV in terrestrial animals, where infection classically leads to death, the dynamics of RABV in terrestrial animals may not be applicable to bats, particularly in light of evidence of high seroprevalence against RABV and other lyssaviruses in apparently healthy conspecifics (23,30,54).…”

Evidence of Lagos Bat Virus Circulation among Nigerian Fruit Bats

“…Both samples that demonstrated neutralizing activity against MOKV came from E. helvum in Karfi. Other studies in Africa record about 38% virus neutralizing activity to LBV among fruit bats in Ghana and Kenya (Hayman et al, 2008: Kuzmin et al, 2008.…”