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10 THE RURAL VOICE
DIAGNOSTICS
LYME DISEASE
by DR. G. K. A. JOSEPHSON
VETERINARY LABORATORY SERVICES
Lyme disease was discussed previ-
ously (June issue), but the information
presented at that time dealt primarily
with the actual disease, its historical
features, its symptoms and diagnosis.
In this issue, some of the practical as-
pects of the disease will be presented,
particularly as it relates to humans.
First of all, the human disease is
not as prevalent in Ontario as we
might be led to believe. The disease is
difficult to diagnose, as both false neg-
ative and false positive blood antibody
levels have been reported.
From 1984 to 1989, only 76 cases
were reported, with 44 having no his-
tory of traveling to an area outside of
Ontario where Lyme disease is com-
mon. Since the disease is reportable
in Ontario, we must assume that most,
if not all, of the diagnosed cases are
included in these figures. In all of
these cases, there was an increase in
the antibody level in the blood, and in
36 of the 44, the classical skin lesion
that appears as an expanding red area
with a central clear area, was evident
and was at least five cm (two inches)
in diameter.
Eight of these cases were identified
in persons either working or holiday-
ing in the Long Point area. Both the
tick (Ixodes dammini) that carries the
causative organism and the organism
itself, Borrelia burgdorferi, have been
recovered from animals in the Nation-
al Wildlife Area and Provincial Park
at Long Point, but not elsewhere in the
province. The highest incidence of
human disease is in northwestern On-
tario. Although the tick has not been
identified in that area, the disease is
quite widespread in Minnesota and
Wisconsin. The other reported cases
are difficult to explain in terms of the
mouse -tick -deer (or human) cycle.
The activities mentioned by those
diagnosed with the disease involved
the outdoors and included camping,
hiking in wooded areas, cutting grass
and either work eg. cutting brush, or
recreation eg. hunting or bird watch-
ing. Less than half could recall a pre-
vious insect or tick bite, and in none of
the cases was the insect identified.
Figures show a marked annual in-
crease, particularly from 1988 to 1989.
This increase may reflect an actual in-
crease in the disease, but may also be
partially due to increased public and
medical awareness. However, it is
probable and quite likely that the num-
ber of cases reported annually will
continue to increase.
Lyme disease appears to have a
seasonal distribution, with most cases
diagnosed in June to August. This of
course coincides with the time of year
when the nymph form of the tick is
feeding on animals, including humans.
In spite of its low incidence, sever-
al preventive measures can and should
be used to help avoid tick bites in a-
reas where the disease is common or
where ticks are known to exist. These
include: • avoid walking barelegged in
tall grass or woods • wear long -sleeve
shirts and pants, tucking the cuffs into
socks. Light coloured clothes make it
easier to find the ticks, which vary
from pinhead (when empty) to raisin
(when engorged with blood) in size
• check daily to see if there are ticks
on the skin • remove ticks with twee-
zers by applying gentle firm pressure
and pulling the tick straight out • use
insect repellent on exposed skin
Tick removal from pets should be
similar to the method mentioned a-
bove. It is also important to record the
date and place that the tick was picked
up and also the location of any bite.
Most important however, is to con-
sult your doctor if you exhibit any of
the symptoms of the disease. Cats re-
portedly are less likely to exhibit signs
of the infection that dogs.0
We welcome any suggestions from readers
for future topics. We also invite interested
persons to take a tour of the facilities at
the Diagnostic Laboratory at Huron Park.
We would ask that you make prior arran-
gements by phoning 228-6691, Ext. 276.