NSW and Victorian health departments have issued alerts after a number of pigs in piggeries located in southern NSW and near Echuca, just over the border into Victoria, were found to be infected with the Japanese encephalitis virus (JEV). As the virus is transmitted by mosquitoes that have fed on a JEV- infected host (generally wading birds and pigs), this indicates that the virus is circulating in local mosquito populations and adds the potential for JEV transmission to humans (via the bites of one of these virus-carrying mosquitoes). Humans are usually considered dead-end virus hosts as mosquitoes are unlikely to become infected through feeding on the low levels of virus circulating during an infection (unlike pigs which are known as virus amplifiers).
The Victorian department’s health advisory notes that ‘No cases of JEV have been detected in humans, however several cases of encephalitis with no identified cause have been detected in NSW and SA in the past month’. The patients all reported recent mosquito bites and ‘their presentation is suggestive of a mosquito-borne viral infection’.
As recommended by both health departments, the best method of prevention is to use personal protection measures to avoid mosquito bites at all times:
- Be aware of peak mosquito exposure places and times (usually around dawn and dusk)
- Use effective insect repellents & contact insecticides
- Wear appropriate clothing
- Avoid scents & perfumes
- Mosquito nets, insect coils and sprays
In related news, South Australian health authorities are also warning of the increased risk of mosquito-borne viruses: Be Alert for Flaviviruses