While Lyme disease rarely occurs in Australia and cannot be locally acquired, it is still important to be aware of this potentially serious infection.
Lyme disease (also known as Lyme borreliosis) is a bacterial infection transmitted through tick bites (Ngan & Vanousova 2015).
It is a potentially multi-systemic condition that may lead to serious symptoms if left untreated (Lyme Disease Association of Australia 2018).
The illness is predominantly caused by four types of bacteria in the Borrelia burgdorferi sensu lato group:
(NSW Health 2017; CDC 2019)
Lyme disease is spread through ticks that become infected with Borrelia by feeding on the blood of certain wild mammals that naturally carry the bacteria, particularly white-footed mice (Dehhaghi et al. 2019; Bush 2020).
Borrelia survives in the tick’s midgut and can infect humans and other animals through bites. Generally, the tick must be attached to a host’s skin for 36 to 48 hours in order for Borrelia to be transmitted. Ticks are often encountered in high grass, brush, woodlands and forests (Ngan & Vanousova 2015).
Most cases of Lyme disease are caused by nymphs - immature (young) ticks - as they are under 2 mm in size and are therefore less likely to be discovered and removed before the Borrelia can be transmitted to the host (CDC 2020a).
The main vectors (carriers) of Borrelia are certain species of ticks from the Ixodidae family (hard-bodied ticks). These species include:
(Ngan & Vanousova 2015; LymeDisease.org 2021)
None of the above tick species nor the Lyme disease-causing Borrelia are found in Australia (Healthdirect 2019; APH 2016). While other Ixodidae family ticks live in Australia, none of them have been found to be carriers of Borrelia bacteria. Furthermore, there is no evidence of locally-acquired Lyme disease (NSW Health 2017; Dehhaghi et al. 2019).
Despite this, returning overseas travellers may be at risk of Lyme disease (SA Health 2020).
It is not possible for Lyme disease to spread between people (NSW Health 2017).
The most typical symptom of Lyme disease is erythema migrans, a red expanding rash that often resembles a bullseye. Erythema migrans occurs in about 70 to 80% of Lyme disease presentations and usually appears at the site of the tick bite after 7 to 14 days. In most cases, the rash is not painful or itchy but may feel warm to the touch. It may expand to 50 cm in diameter before spontaneously disappearing after three to four weeks (Ngan & Vanousova 2015; Bush 2020).
Lyme disease can be categorised into two stages. If left untreated, it will progress:
| Stage | When Does it Occur? | Symptoms |
|---|---|---|
| Early Lyme disease | 3 to 30 days after the tick bite |
|
| Late Lyme disease | Days to weeks after the tick bite. It may progress over months to years. |
|
(CDC 2021; Ngan & Vanousova 2015; Bush 2020; NSW Health 2017)
Most of the cases identified in Australia have already progressed to the late stage due to a lack of early intervention strategies (Lyme Disease Association of Australia 2018).
In earlier stages, Lyme disease may be diagnosed using physical symptoms (e.g. the presence of erythema migrans) and the possibility of exposure to infected ticks (NSW Health 2017).
Diagnosing late-stage Lyme disease requires complex laboratory testing and specialist expertise. Tests must only be performed by institutions that are accredited with the National Association of Testing Authorities (NATA) (NSW Health 2017).
Laboratory tests generally involve screening for relevant antibodies using the enzyme-linked immunosorbent assay (ELISA) test. These results are then confirmed using a western blot test (NSW Health 2017).
Lyme disease is treated using antibiotics. If recognised and addressed early, the infection generally responds well to treatment and the patient is able to make a full recovery (Ngan & Vanousova 2015).
However, if treatment is delayed, the patient is less likely to recover completely. In some cases, they may experience long-term symptoms such as arthritis, fatigue, headaches and neurological issues even after successful treatment (Ngan & Vanousova 2015; Bush 2020).
Lyme disease can be prevented by avoiding tick bites. If spending time in areas where Lyme disease-carrying tick species live, consider the following strategies:
(NSW Health 2017; CDC 2019b)
The tick should be killed before being removed to prevent more saliva from being injected into the wound.
(Healthdirect 2019; SA Health 2020)
Question 1 of 3
How long must a tick stay attached for in order to infect the host with Borrelia bacteria?
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