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

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 (R0 = 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

Presence of European bat lyssavirus RNas in apparently healthy Rousettus aegyptiacus bats

Apparently healthy Rousettus aegyptiacus bats were randomly chosen from a Dutch colony naturally infected with European bat lyssavirus subgenotype 1a (EBL1a). These bats were euthanised three months after the first evidence of an EBL1a infection in the colony. EBL1a genomic and antigenomic RNAs of the nucleoprotein gene were detected by nested reverse transcriptase PCR in 75% of the examined Rousettus aegyptiacus bats. The EBL1a RNAs of the nucleoprotein gene were detected mainly in brain tissues, but also in other organs. EBL1a messenger RNAs of the nucleoprotein gene and the glycoprotein gene were detected in brain tissues. The standard fluorescent antibody test revealed the presence of lyssavirus antigens in brain tissues from 7 (17.5%) Rousettus aegyptiacus bats. Furthermore, EBL1a could not be detected by virus isolation on murine neuroblastoma cells or by intracerebral inoculation of suckling mice. Neutralising antibodies directed against EBL1 were detected in 11% of the examined bats. This study shows that at least 85% of the apparently healthy Rousettus aegyptiacus bats must have been infected with EBL1a, and that these bats may survive from an EBL1a infection. Furthermore, the study supports the possibility of a long-term maintenance of EBL1a genome in Rousettus aegyptiacus bats

A simple, rapid and reliable enzyme-linked immunosorbent assay for the detection of bovine virus diarrhoea virus (BVDV) specific antibodies in cattle serum, plasma and bulk milk

To detect Bovine Virus Diarrhoea Virus (BVDV)-specific antibodies in cattle serum, plasma and bulk milk, a simple, reliable and rapid blocking ELISA ("Ceditest") has been developed using two monoclonal antibodies ("WB112" and "WB103") directed to different highly conserved epitopes on the non-structural peptide NS3 of pestiviruses. The test can be performed at high reproducibility using undiluted samples. In testing 1000 field serum samples, the ELISA showed a specificity and a sensitivity relative to the virus neutralization test of 99% and 98%, respectively. The blocking ELISA is able to detect specific antibodies in serum obtained 12 days after an acute infection and in serum of vaccinated and challenged animals. A frequency distribution diagram, obtained by testing almost 1800 random Dutch field serum samples, showed a clear separation between a negative population (maximum frequency of the % inhibition at −5%) and a positive population (maximum frequency of the % inhibition at 95%). Based on these data, the prevalence of seropositive animals was 65% (95% confidence interval: 63%–67%). By exchanging plasma- and bulk milk samples between two laboratories (The Netherlands and Denmark), a good overall agreement was found between results obtained with the Ceditest and those obtained with the Danish blocking ELISA as used in the Danish BVDV eradication programme. The results indicate that BVDV infections can reliably be diagnosed by the Ceditest ELISA and that the test is suitable for use in large scale screening and eradication programmes