Scrub typhus

Scrub typhus is a disease caused by bacteria called Orientia tsutsugamushi, which is in the rickettsia family.

How it is spread

The germ infects people when they are bitten (usually painlessly) by an infected larval mite called Leptotrombidium deliense. The mite is very small (0.2 to 0.4mm) and can only be seen through a microscope or magnifying glass.

The mites live in grassland areas at the edge of dense monsoon forests or forested creeks. Mites usually feed on marsupials and other native animals such as rats but they can attach to passing humans and bite for a blood meal.

Scrub typhus cannot spread from one person to another.

Where is the disease found

Scrub typhus is found in Asia and the Pacific region including northern Australia. The endemic area extends from south-eastern Siberia and northern Japan, through eastern and south-east Asia, to Vanuatu in the east and Pakistan in the west. Other countries may have small foci. Thailand has the highest prevalence of disease.

There have been numerous reported cases of infection in the Top End of the Northern Territory since 1990 with at least one fatality.

More than half of the reported cases were infected in Litchfield National Park. Other areas associated with infection include all of the following:

• Batchelor area
• Melville Island
• Groote Eylandt
• Emu Point near Peppimenarti in the Daly River area.

Risk areas in the Top End are described as locations near well-watered escarpment slopes that have associated creeks and seepage areas with monsoon forest and grasslands in close proximity.

Symptoms

The symptoms usually occur within 1 to 2 weeks of being bitten. They may include fever, chills, sweating, headache, cough, swollen glands and sometimes a dull red skin rash. The bite site often ulcerates and becomes red with a central black scab, called an “eschar”.

Any person with these symptoms who has recently visited a risk area, in particular Litchfield Park, should mention the possibility of scrub typhus to their doctor. The diagnosis is made by a blood test.

Who is at risk

Anyone visiting areas near well watered escarpment slopes of the Top End that have associated creeks and seepage areas with monsoon forest and grasslands in close proximity are at risk.

The warning particularly applies for:

• bushwalkers
• off road tourists
• Aboriginal people pursuing traditional lifestyles
• military personnel on bush exercises
• park rangers
• people clearing virgin land in high risk areas.

Treatment

Treatment with antibiotics is necessary and very effective. Doxycycline is the drug of choice. Often people require treatment in hospital.

Prevention

You should take precautions to avoid being bitten by mites when visiting 'at risk' areas. These include:

• wear footwear such as runners or boots with socks rather than walking barefoot or wearing sandals. Long trousers are preferable when bushwalking
• apply insect repellent that contains DEET or picaridin to all exposed skin areas on the legs, onto socks and the bottom half of trousers (this is the same repellent you use to prevent mosquito bites)
• do not sit or lie on bare ground or grass, use a suitable ground sheet or other ground cover
• camp in cleared areas away from dense forests. Use tents with attached floors. People who are working in infested areas should consider wearing permethrin impregnated clothing.

Information for health professionals

To find out more go to the NT Health website.

Contact

For more information contact the Centre for Disease Control.