Lyme disease is caused by the bacterium Borrelia burgdorferi.
Typical symptoms include fever, headache, fatigue, sore muscles and joints, and a characteristic skin rash called erythema migrans.
Although locally-acquired Lyme borreliosis cannot be ruled out, there is little evidence that it occurs in Australia. There is a continuing risk of overseas-acquired Lyme disease being imported into NSW.
What is the disease?
- Lyme disease is caused by the bacterium called Borrelia.
- The first symptom is usually a characteristic pink or red rash that starts as a small red spot that gradually spreads in a much larger circle with a characteristic bulls-eye appearance. This normally happens between 3 and 32 days after being bitten by an infected tick. Not everyone with Lyme disease gets the rash.
- There may also be fever, headaches, tiredness and joint pains.
- In later stages of Lyme disease the infection spreads through the bloodstream and can cause infection in the brain and membranes surrounding the brain (meningoencephalitis) and infection in or around the heart (endocarditis, myocarditis or pericarditis). The disease can also cause inflammation of joints and cause joint pain and long-term neurological involvement.
How is Lyme disease spread?
- Lyme disease is transmitted following the bite of a tick that is infected with the Borrelia bacterium.
- Only some species of ticks are capable of being infected by the Borrelia bacteria and only these infected ticks can pass the infection on to humans. This group of ticks is found in Asia, Europe and North America, but not in Australia.
- Ticks with Borrelia infection live in temperate forested areas of northern Asia and Europe (especially central and eastern Europe) and the United States (especially north-eastern, north central and Pacific coastal USA).
- In the 1990s, 12,000 ticks were collected from different parts of NSW and were tested for Borrelia bacteria. No evidence of Borrelia infection could be found in any of the ticks collected.
- In April 2011, NSW Health convened an expert panel with expertise in public health, epidemiology, infectious diseases, rickettsial diseases and entomology to provide advice on the current risk of Lyme disease in NSW. The panel concluded that although locally-acquired Lyme disease cannot be ruled out, there is little evidence that it occurs in Australia. The panel also noted that there was a continuing risk of overseas-acquired Lyme disease being imported into NSW.
- Lyme disease is not spread from person to person.
How is Lyme disease diagnosed?
- Lyme disease is diagnosed based on symptoms, physical findings (e.g., a characteristic rash), and the possibility of exposure to infected ticks. Laboratory testing is helpful in the later stages of disease.
- Diagnosis of any infectious disease requires a combination of clinical experience and assessment by the doctor and understanding of the lab tests and their limitations. Laboratory tests are rarely definitive and all tests have a proportion of results which are false positive (test indicates disease in someone without the disease) and false negative (test indicates that there is no disease in someone with the disease). When tests are done in places where a disease is rare or absent (for example, Lyme disease in Australia), many positive tests will be falsely positive.
- The tests to diagnose Lyme disease are technically complex and require specialist expertise. It is important for people who want to be tested to make sure the laboratory that performs the test has accreditation with the National Association of Testing Authorities (NATA).
- Lyme disease is most commonly diagnosed by a screening test called ELISA and this is then confirmed using a western blot test. Both of these tests detect antibodies that are produced by the immune system of someone with Lyme disease.
- Lyme disease can also be diagnosed by testing a sample of the skin lesion by nucleic acid testing (eg PCR) or culture. (See testing advise for clinicians for more information).
- Occasionally, tests performed in Australia for Lyme disease show evidence of an infection. When these cases have been followed up in the past, the cases have been found to have acquired the infection while overseas.
- Tests for Lyme disease should only be done by laboratories that have current accreditation with National Association of Testing Authorities (NATA).
How is Lyme disease treated?
- Most cases of Lyme disease can be treated successfully with a few weeks of antibiotics
Can ticks in NSW transmit infections?
- A species of paralysis tick called Ixodes holocyclus can be found along Australia's east coast and can cause tick paralysis, tick typhus and allergic reactions.
- While there is little evidence that Lyme disease is caused by Australian ticks, there may be other infections carried by Australian ticks which may cause an infection which is similar to Lyme disease. These infections remain poorly characterised.
How to prevent tick bites
- Ticks tend to live in coastal areas in NSW.
- Wear appropriate clothing when outdoors in tick areas including long sleeved shirts, long pants tucked into socks and a wide brimmed hat. Ticks are more easily detected on light coloured clothing.
- Spray clothes and hats with an insect repellent and wear a repellent that contains DEET or Picaridin.
- When returning from an area known to have ticks, remove clothing and search for ticks, especially behind the ears, on the back of the head, groin, armpits and back of knees. Be careful where clothes are placed as they may introduce ticks to inside the house. Don't forget to check children and pets.
- Ticks in the nymph stage are tiny (eg. as big as a poppy seed) but can still transmit infections so it's important to have a very close look at your skin in good light to see any small ticks that may be feeding. People are sometimes not aware that they have been bitten by a tick.
- In tick-infected areas, mow grass in the backyard and keep mulch and leaf litter away from the main entrance to the house. Trim shrubs overhanging paths and play areas.
- When walking in tick-infested areas try to keep to the centre of cleared paths as much as possible and try to avoid brushing up against plants and grasses as you walk.
- In the Northern Hemisphere the risks of tick bites and Lyme disease is greatest in late spring, summer and early autumn when the nymph ticks are more abundant and when people visit habitats where ticks live such as forests and other densely vegetated areas, especially areas with high grass and lots of leaf litter. Lyme disease is more likely to affect people participating in outdoor activities such as hiking or mountain biking in tick-infested areas.
What to do if bitten by a tick
- Remove a tick as soon as possible after locating it.
- Use fine pointed tweezers and grasp the tick as close to the skin as possible. Gently pull the tick straight out with steady pressure. If you have difficulty, seek medical attention.
- Do not try to kill the tick with methylated spirits or any other chemicals as this will cause the tick to inject more toxins. If you have a severe infestation by larval stage ticks (often referred to as grass ticks) take a bath for 30 minutes with 1 cup of bicarbonate of soda.
What is the public health response?
Lyme disease is not notifiable in NSW.
For further information please call your local Public Health Unit on 1300 066 055