The world is certainly getting "smaller," especially in terms of infectious diseases.  One example is the renewed controversy this month over the existence of Lyme disease in Australia.  A Sydney man was recently diagnosed with the disease following his death, and now a doctor from Laurieton claims to have "absolute proof" of at least two other Australians with the infection.

Lyme disease is caused by infection with one of three species of Borrelia, previously all known as Borrelia burgdorferi.  The disease is transmitted by a few specific species of ticks belonging to the genus Ixodes.  It is relatively common in areas of North America (including some parts of Canada) and Europe where these tick species are also found.  Ticks become infected by feeding on reservoir hosts, which are typically small mammals.  Early signs and symptoms in people following a bite from an infected tick can include a rash, fever, headaches, tiredness and joint pain.  The disease can be very difficult to diagnose because the initial signs are quite non-specific, particularly if the person does not report being bitten by a tick.

None of the tick species known to transmit Lyme disease are found in Australia, although there is one species of Ixodes tick there which some believe is a potential candidate for a vector.  However, after testing some 12 000 of these ticks, evidence of Borrelia infection has still not been found.  Also, none of the known reservoir hosts of Borrelia are said to live in Australia, and no other hosts have been identified.

The Laurieton physician, Dr, Mayne, claims he has "absolute proof" of Lyme disease in at least two of his patients, and says he has about 30 more patients with the disease as well.  "Proof" is a very strong word.  Not only is the disease hard to diagnose clinically, but there is also no perfect test that can detect infection for certain.  Even the DNA test on which Dr. Mayne is hanging his hat can be prone to false-negative and false-positive results.  The article also does not state whether or not the infected patients traveled outside the country and could have potentially picked up the disease in a Lyme-endemic area.  Further investigation is needed before anyone can claim to have "proof."

So why am I writing about this situation on a zoonotic disease blog, when there hasn’t even been any mention of pets, and the disease can’t be directly transmitted between people and animals anyway?  Because this is a perfect example of a situation in which physicians and veterinarians could potentially work together for the greater good, under the "one health, one medicine" banner.  Dogs in particular can also be affected by Lyme disease.  If the Australians really want to know if Lyme disease has made it to their shores – or perhaps some other tick-borne disease that mimics Lyme – then they shouldn’t just be looking in people.  By alerting veterinarians that Lyme disease or a similar condition is cropping up in humans, they can start to look for it in the animal population as well.  If they’re left unaware, Australian veterinarians may not consider Borrelia as a potential cause of illness in their patients and therefore not test for it.  If pets also start testing positive for Lyme disease, then hopefully that would be communicated back to the human medical community to increase testing of suspect cases there as well.  If more cases are identified, either human or animal, then further efforts could be taken to identify the tick source and reservoir hosts in Australia.

More information about Lyme disease and ticks in dogs is available in the Worms & Germs archives.

Image: The "classic" bulls-eye rash associated with a tick bite transmitting Lyme disease (source: CDC Public Health Image Library #9874)