BY CHRIS ROBINSON
There are no deer on P.E.I. Local public health officials have therefore mistakenly concluded that Lyme and other tick borne diseases are not a serious threat here; because these diseases are transmitted by the bite of the so-called deer tick. Last June, P.E.I.'s chief public health officer declared that there have only ever been five confirmed Lyme disease cases on P.E.I., and that four of these were "come from away" cases from tick bites elsewhere on the mainland. Unfortunately, this reassurance is misleading.
First, there are definitely plenty of deer ticks on the Island, and they are increasing, thanks to climate change. Warmer winters mean that ticks are now able to over winter and reproduce. More new tick immigrants arrive from the U.S. each spring as passengers on migrating waterfowl and other birds. Once these ticks arrive, they find lots of field mice (also people and their pets) as hosts for their blood meals, so no deer are needed for ticks to survive and reproduce. Over that past several years, the Atlantic Vet College has tested 80-100 ticks annually from across P.E.I.: approximately 1 in 4 ticks carried Lyme.
Secondly, the current clinical blood tests being used to diagnose Lyme and other tick borne diseases are woefully unreliable, so the true disease burden is vastly under-diagnosed. (More accurate PCR blood tests are available but they are not routinely ordered). For Lyme, physicians often will only order blood tests if a "bull’s-eye rash" develops around the bite, yet in many cases no rash was ever observed, and the tick escaped undetected. Moreover, other serious tick borne diseases like Babesia Microti are never present with a bull’s-eye rash, so none of these cases are being sent for testing. Both Lyme and Babesia present with similar flu-like symptoms, which last for months or years if left untreated. These diseases are not only disabling, but they can also prove fatal for certain high-risk groups.
My own personal experience prompted me to write about this issue. Last May I was bitten by a deer tick in Cavendish while gardening in my backyard. I never saw the tick, only a small bloody crater in my thigh about the width of a match head. This is not unusual, since many ticks go undetected, and over half of all tick bites occur from small immature nymphs, which are no larger than a freckle. As a health scientist, I suspected it was a tick bite and looked for signs of a bull’s-eye rash, but was relieved when none appeared.
A week later I developed flu-like symptoms, which dragged on for months. In September, I saw my family physician, who ordered the routine "ELISA" blood test for Lyme. This antibody-based test is known to miss a large percentage of true Lyme cases, which is why the CDC recently increased their national U.S. estimates of Lyme incidence from 30,000 to over 350,000 new cases annually. When my ELISA came back negative, I decided to pay $1,500 for more accurate PCR blood tests at a private U.S. lab to see if my blood contained DNA from Lyme or other tick borne diseases. The results were negative for Lyme, but positive for Babesia microti. Babesia is a protozoan which enters via tick bite and then attacks red blood cells, hiding inside them so that the immune system cannot find and eliminate them. It is very similar to malaria. I have begun treatment with clindamycin (antibiotic) and quinine (anti-malarial).
Tick borne diseases on P.E.I. are a major public health threat, so Health P.E.I. and physicians should re-evaluate existing inadequate efforts at prevention and diagnosis. The unreliable ELISA Lyme test should be abandoned in favour of more timely and accurate PCR blood tests. The "bull’s-eye rash" should also be dropped as a prerequisite for blood testing. Since tick borne diseases such as Babesia microti can be readily transmitted by blood transfusion, it is also imperative that those responsible for blood safety act immediately to introduce new blood screening measures in order to address the significant undiagnosed burden of tick borne disease in Canada. The CDC in the U.S. found over 160 cases of Babesia microti, which were transmitted by blood transfusion. The tainted blood scandal involving HIV, and subsequent Krever Royal Commission, should serve as a recent cautionary tale.
- Chris Robinson is a health economist / epidemiologist, and former head of Evidence and Risk Assessment Division, Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada. He is now retired and living in Cavendish