Temporal Dynamics of European Bat Lyssavirus Type 1 and Survival of Myotis myotis Bats in Natural Colonies

Abstract

Many emerging RNA viruses of public health concern have recently been detected in bats. However, the dynamics of these viruses in natural bat colonies is presently unknown. Consequently, prediction of the spread of these viruses and the establishment of appropriate control measures are hindered by a lack of information. To this aim, we collected epidemiological, virological and ecological data during a twelve-year longitudinal study in two colonies of insectivorous bats (Myotis myotis) located in Spain and infected by the most common bat lyssavirus found in Europe, the European bat lyssavirus subtype 1 (EBLV-1). This active survey demonstrates that cyclic lyssavirus infections occurred with periodic oscillations in the number of susceptible, immune and infected bats. Persistence of immunity for more than one year was detected in some individuals. These data were further used to feed models to analyze the temporal dynamics of EBLV-1 and the survival rate of bats. According to these models, the infection is characterized by a predicted low basic reproductive rate (R 0 = 1.706) and a short infectious period (D = 5.1 days). In contrast to observations in most non-flying animals infected with rabies, the survival model shows no variation in mortality after EBLV-1 infection of M. myotis. These findings have considerable public health implications in terms of management of colonies where lyssavirus-positive bats have been recorded and confirm the potential risk of rabies transmission to humans. A greater understanding of the dynamics of lyssavirus in bat colonies also provides a model to study how bats contribute to the maintenance and transmission of other viruses of public health concern.

Experimental infection of serotine bats (Eptesicus serotinus) with European bat lyssavirus type 1a

“…Neither virus nor viral RNA was detected in the brain, salivary gland, other organs or oral swabs of bats that survived the experiments, contradicting any suggested carrier state in bats. In addition, the presence of viral RNA in blood clots as described elsewhere (Serra-Cobo et al, 2002;Amengual et al, 2007) seems to have been refuted by our results.…”

“…Müller, unpublished data). Extremely high virus-neutralizing activity has been found in various other bat species in bat colonies in Spain (Serra-Cobo et al, 2002;Amengual et al, 2007). However, there is no validated standard EBLV-1a in bats serological method available for the measurement of VNAs in bats.…”

Twenty years of active bat rabies surveillance in Germany: a detailed analysis and future perspectives

“…Although in general high VNA titres tend to be specific more often, low titres rather tend to be unspecific by resembling non-humoral neutralization or virucidal effects. Even if high VNA titres were specific, the extraordinary high seroprevalences found in Spanish M. myotis colonies [21,23], compared to ours, raise further questions. This could be a true representation of regional differences in virus circulation and dynamics; however, an influence of the various neutralization test methods applied cannot be excluded.…”

“…While studies in the UK and Spain had mainly focused on reservoir species, i.e. Daubenton's bat (M. daubentonii), and Eptesicus bat species [17,20], others screened the greater mouse-eared bat (M. myotis) [23], while only in France, Slovenia and in one study from Spain was a similarly high number of different bat species sampled [19,21,27]. With more than 4000 oropharyngeal swabs and 1200 blood samples tested by RT-PCR and RFFIT, respectively, this is one of the most extensive active bat rabies surveillance studies ever conducted in Europe.…”

“…Passive surveillance as the method of choice focuses on investigations of bats which were found with suspicious clinical symptoms or dead, whereas active surveillance for bat lyssavirus infections consisting of collecting and investigating micro-samples of blood and saliva from free-living indigenous bat populations as pioneered in North America [14][15][16] is considered valuable for obtaining additional information. As a consequence, active bat rabies surveillance in free-ranging bat populations was implemented in the UK [17,18], France [19], Spain [20][21][22][23][24], Switzerland [25], Sweden [26], Slovenia [27,28], Serbia [29] and Belgium [30]. While in some countries results from passive surveillance were confirmed by active surveillance, the detection of virus neutralizing antibodies (VNA) in sera of insectivorous bats indicated the presence of lyssaviruses in countries where bat rabies cases had not yet been reported [6] resulting in speculation as to whether bat lyssavirus infections are in fact more frequent and more widely distributed than assumed from passive surveillance data.…”