Swampy areas, creeks, dams, undrained pot plants,
blocked gutters, disused bottles, and old tyres are places where mosquitos love to breed.
Although mosquitos are most abundant through January to March, and Australia’s peak
incidence of mosquito transmitted diseases is through the summer and autumn months, you
may be a victim any time throughout the year.
At home, work, on holidays, walking, fishing or doing any outdoors
activity, protect yourself against the skeeters, you won’t want to be hit by
‘Ross’ or beaten by the ‘Barmah’.
ROSS RIVER FEVER & BARMAH FOREST DISEASE
Both Ross River (RR) and Barmah Forest (BF) disease are caused by
viruses which are transmitted from human to human through the bite of mosquitoes. A wide
variety of symptoms may occur from rashes with fevers, to arthritis that can last from
months to years with RR virus infection. There are no specific treatments for these
debilitating diseases. Your best action is to prevent a mosquito from biting you.
Natural History
RR disease is the most commonly transmitted mosquito-borne viral
disease to humans in Australia. The number of cases has averaged more than 5,000 per annum
during 1991-1997. The virus appears to be endemic in most rural areas, and there has been
an increasing incidence near major cities. BF disease is less common, but the number of
cases appears to be increasing annually, with several outbreaks occurring during the
1990's.
Areas under intensive irrigation and localities close to saltmarshes,
are most productive for mosquito populations and hence tend to result in the highest
number of human cases of disease. Outbreaks occur when local conditions of rainfall, tides
and temperature promote vector abundance. Studies have indicated that native mammals, most
likely kangaroos and wallabies, are natural hosts for RR virus but little is known about
the hosts of Barmah Forest virus.
Symptoms
Human infection with RR virus or BF virus, may result in the clinical
condition known as polyarthritis. The effects range from a symptomless condition, through
a transient rash and mild illness with fever, to polyarthritis affecting chiefly the
ankles, fingers, knees, and wrists, but other joints may be affected. The disease is not
fatal. For RR virus, symptoms become evident from 3-21 days (average 9 days) after
infection, and mild cases may recover in less than one month but many persist for months
to years. Recent studies have indicated that the rash may be more florid with BF virus
infections but the arthritic symptoms are greater with RR virus infection. People of
working age are most likely to be afflicted with the diseases, whilst symptoms are rare in
children.
Prevention is your only cure
Specific therapies do not exist to treat the disease, rather it is the
symptoms that are alleviated. This includes various analgesics to reduce the pain and
fevers, and anti-inflammatory agents for the arthritic symptoms.
Prevention of mosquito borne viral diseases is mainly accomplished through
reducing the threat of bites from mosquitoes. This can be achieved either through
undertaking active mosquito control or by the use of personal protective measures.
Householders can ensure that their own backyard does not contain water
holding containers which can provide suitable mosquito larval habitats (e.g. undrained pot
plants, blocked gutters, disused bottles, old tyres, etc). Personal protective measures
include: avoiding known mosquito infested areas, especially at dawn and dusk when
mosquitoes are most active; ensuring that houses are adequately screened; using insect
repellents that contain the chemical DEET, and reapplying it regularly; and wearing long
sleeved shirts and pants.
