Bats are one of the zoological groups attracting most interest around the world in terms of studying the epidemiology of rabies.

However, the dynamics of the viral infection in these organisms remains poorly understood. A team from the UB and the Institut Pasteur in Paris has just reported the first epidemiological, ecological and virological study with previously unpublished data on the transmission and development of rabies in these mammals.

The study is the result of twelve years of monitoring the dynamics of rabies virus infection (European bat lyssavirus subtype 1 - EBL1) in two wild bat (Myotis myotis) colonies in Spain. In total, the scientific data refer to the monitoring of over 1000 individuals from two colonies situated 35 km from one another.

The authors of the article are the researchers Blanca Amengual, Marc López-Roig and Jordi Serra-Cobo, from the Department of Animal Biology at the UB and the Barcelona Science Park, and Hervé Bourhy, from the Institut Pasteur in Paris.

“Bats can end up eliminating the rabies virus. Unlike what occurs in terrestrial mammals the viral infection does not significantly increase mortality in the bat colony”, says Serra-Cobo, director of the research and member of the vertebrate biology group coordinated by Professor Jacint Nadal of the Faculty of Biology.

He also points out that “when the rabies virus infects a bat colony, this does not significantly affect survival. This is the first publication of a mathematical model that analyzes survival rates among bats in a natural colony affected by this infection”.

The immunological response of these mammals to the infection has raised new hopes in the search for new health strategies against this fatal viral disease, which is considered to be an emerging zoonosis that is spread widely across the world. In the article the authors describe the initial findings from the mathematical model, which they have been able to compare with the results observed in the colonies during the study period.

According to the study the entry of the virus into the colony triggers a powerful immune response. Serological analyses and blood cell fractions were used to determine different parameters of the immune response of bats to the rabies virus. The results suggest that in response to infection, bats are able to produce antibodies that can last for up to twelve months. Other novel findings of the study include an estimate of the basic rate of viral reproduction and the period during which a bat is able to infect other individuals, this being five days. These infectious periods, which are cyclical in nature, occur in intervals of 2.5 to 5 years. The results obtained are of enormous importance for public health as they show that the risk of transmission is very low in this species.

In 2002 the same scientific team reported another set of original findings in the field of virology: they were the first to detect the rabies virus in the blood of bats using molecular genetic techniques (nested RT-PCR), and this research was published in the journal Emerging Infectious Diseases of the Centres for Disease Control (CDC). This discovery received a highly favourable appraisal from the editors of Rabies Bulletin Europe, published by the World Health Organization (WHO).

The study was promoted and funded by the Department of Health and Consumer Affairs of the Government of the Balearic Islands, and received the backing of Spain’s Ministry of Health and Consumer Affairs.

Source: University of Barcelona