When Neutral Bugs Turn Nasty: Venezuelan equine encephalitis virus
The Venezuelan equine encephalitis virus (VEEV) is responsible for a zoonic disease transmitted by mosquitoes that can cause death in humans and equines (such as horses, donkeys and asses). This disease emerges periodically throughout central and southern America and occasionally even in the USA. In humans it causes flu-like symptoms including severe headaches which usually subside after a few days. Death usually only occurs in immunocompromised people such as the very old or young. In equines the effects are more severe and neurological disorders are often observed. The death rate in equines has been estimated as high as 83% for some strains. In these animals death usually occurs within a week of infection.
It has been hypothesised that VEE epidemics are caused by alterations to the genome of a relatively harmless strain of the virus. This less virulent strain of the virus is carried asymptomatically by many small, forest dwelling mammals throughout the Americas and is only capable of infecting humans who are continuously in close proximity with infected populations. This strain is very rarely passed to equines. It was shown in a recent study that a single mutation of the genome causing an amino acid substitution in the less virulent strain is all that is needed to turn it into an epidemic strain. Because of this, it is believed that these outbreaks of highly virulent VEEV will continue to occur unless mosquito populations are better controlled and more equines are vaccinated.
It has been hypothesised that VEE epidemics are caused by alterations to the genome of a relatively harmless strain of the virus. This less virulent strain of the virus is carried asymptomatically by many small, forest dwelling mammals throughout the Americas and is only capable of infecting humans who are continuously in close proximity with infected populations. This strain is very rarely passed to equines. It was shown in a recent study that a single mutation of the genome causing an amino acid substitution in the less virulent strain is all that is needed to turn it into an epidemic strain. Because of this, it is believed that these outbreaks of highly virulent VEEV will continue to occur unless mosquito populations are better controlled and more equines are vaccinated.
Written by: Sarah Batt
Student number: 41386015
Primary references:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16549790 Venezuelan encephalitis emergence meditated by a phylogenetically predicted viral mutation
http://en.wikipedia.org/wiki/Venezuelan_equine_encephalitis_virus -general info from wikipedia
Secondary references:
http://arjournals.annualreviews.org/doi/pdf/10.1146/annurev.ento.49.061802.123422 - more in depth info on outbreaks
http://www.cdc.gov/ncidod/EID/vol11no05/04-1251.htm -about reservoirs (forest mammals)
http://www.sciencedaily.com/releases/2006/09/060915203515.htm -bioterrorism threat
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=16549790 Venezuelan encephalitis emergence meditated by a phylogenetically predicted viral mutation
http://en.wikipedia.org/wiki/Venezuelan_equine_encephalitis_virus -general info from wikipedia
Secondary references:
http://arjournals.annualreviews.org/doi/pdf/10.1146/annurev.ento.49.061802.123422 - more in depth info on outbreaks
http://www.cdc.gov/ncidod/EID/vol11no05/04-1251.htm -about reservoirs (forest mammals)
http://www.sciencedaily.com/releases/2006/09/060915203515.htm -bioterrorism threat
