Agents of haemorrhagic fevers often change host

Some New World Arenaviruses are known to cause human disease, which up to one third of patients die. The disease is spread principally by inhalation of aerosolized droplets of saliva, respiratory secretions, urine, or blood from infected rodents. Results of a recent research by biologists and data analyst from Masaryk University, Czech Academy of Sciences, and University of York, however, conflict with an earlier hypothesis that the viruses co-evolved with their rodent hosts. One of the world's most infectious classes of disease can therefore spread much more easily than previously thought.

Křeček bavlníkový je hostitelem arenaviru Tamiami. Foto: Michael Drummond.

Michaela Bayerlová and Natália Martínková from the Masaryk University and Academy of Sciences of the Czech Republic, and Nancy Irwin and Oliver Missa from the University of York studied the evolutionary host associations of the Tacaribe virus complex – the New World Arenaviruses – responsible for South American haemorrhagic fevers. New World Arenaviruses consist of 23 viral species split into four groups and known to infect 32 mammal species, mainly rodents. Five of these viruses are known to cause human disease, which up to one third of patients die. There are no vaccines, or prophylactic treatment. It is therefore important to know which rodent species are capable of hosting and spreading the viruses. Natália Martínková said: “This project brought scientists together from different disciplines which enabled us to look at the virus-host relationship from a new perspective.”

The researchers demonstrated with co-phylogenetic analysis that with the exception of the viruses of North America there was no pattern of co-divergence. Using statistical techniques used more frequently in ecology, they found that the four groups of viruses were associated differently with their hosts, and that the pathogenic group of viruses were randomly distributed across the rodent hosts available to them. The researchers found that the occurrence of hosts in the same locality was a better predictor for the pathogenic viruses to jump to a different host than the need to find closely related hosts with similar characteristics and defensive capabilities. “No longer can it be thought that these viruses evolved with their hosts but are instead opportunistically host switching which has important bearings on understanding the potential for the pathogenic strains to affect many types of animal and to expand their range,” added Natália Martínková.

Results of the study have been published in Molecular Ecology journal in the article Complex patterns of host switching in New World arenaviruses. Initial fundamental information for following research arised from the BSc thesis of Michaela Bayerlová, a student of IBA MU’s study programme Computational Biology.

19.6.2012 Source: IBA MU, press release of the Academy of Sciences