Ticks and Tick-Borne Diseases: A Renaissance in Research presented by TiARA Committee Member Stephen Doggett
Ticks and Tick-Borne Diseases: A Renaissance in Research
Stephen L. Doggett
Department of Medical Entomology, CIDMLS, Pathology West - ICPMR,
Westmead Hospital, Westmead, NSW.
The Australian Paralysis Tick, Ixodes holocyclus, is the most important tick species in Australia due to its harmful effects on both humans and companion animals. Ixodes holocyclus occurs along the eastern sea-bird of Australia and is prevalent in moist coastal forests with an abundance of native animals that serves as its hosts, and it is in this environment where humans come in contact with the tick. As the common name indicates, I. holocyclus can cause paralysis and past human deaths occurred before the development of an anti-venene. The bite from the tick can induce allergies, which can range in severity from mild to even anaphylaxis, with occasional deaths being recorded. More recently a syndrome known as ‘mammalian meat allergy’ has been reported whereby people who are bitten by the tick can develop an allergy, and even anaphylaxis, following the consumption of mammalian meats and meat by-products. In the last ten years, great controversy has surrounded this tick species, in particular, whether Lyme disease exists in this country. Lyme disease is caused by the spirochaete bacteria, Borrelia burgdoreri s.l. and is transmitted by ticks in the northern hemisphere, although the main vectors do not occur in Australia. A small group of very vocal patient advocates supported by public media figures, have pushed governments for the disease to be recognized in this country. Much of this drive has been supported by questionable medical and diagnostic backing. In spite of there being not one credible piece of evidence for the existence of Lyme disease in Australia, the federal government has provided research funding to investigate potential pathogens in Australian ticks. No evidence has been found for B. burgdorferi in Australian ticks, although a range of microbes have been detected via modern molecular techniques. One rickettsia found is closely aligned with a species that occurs in the US, which is known to cause human disease, however to date, none of the microbes detected have been associated with local human disease. Unfortunately research on the prevention of tick bite has been neglected, yet arguably, this is the most important area of scientific endeavour, as stopping tick bite will negate any ill affects. My laboratory has now undertaken preliminary work on tick repellents and the results will be presented along with an overview of the recent investigations on tick pathogens.