The doctors at Mountain Animal Hospital recently attended a lecture on Ticks and Tick-borne diseases in Ontario given by Professor Andrew S. Peregrine, parasitologist at Ontario Veterinary College. Dr. Peregrine discussed the increasing threat of tick borne diseases in Ontario, routine screening, as well as management strategies for dogs that have tested positive.
The two ticks we are most likely to see in Ontario are the American Dog Tick (Dermatocentor variabilis, Figure 1) and the Deer Tick (Ixodes scapularis, Figure 2). While American Dog Ticks have the potential to transmit both bacterial and rickettsial diseases, there is no current evidence of ticks harboring these diseases in Ontario. Deer ticks on the other hand may potentially transmit two bacterial diseases in Ontario – Borrelia burgdorferi, more commonly know as “Lyme Disease” and Anaplasma phagocytophilum or “Granulocytic Anaplasmosis” (much less prevalent). Both of these diseases are also transmissible to humans by the bite of an infected tick. Clinical signs in dogs include fever, anorexia, enlarged lymph nodes and polyarthritis causing recurrent lameness. The incubation period in infected dogs is between 2 to 5 months.
 Figure 1. American Dog Tick, note the multi-coloured scutum |
 Figure 2. Deer Tick, note the dark brown scutum |
Data published by the Public Health Agency of Canada shows that the risk of transmission of B. burgdorferi to dogs in Ontario is increasing. Between 2008 and 2012 the potential of exposure to B. burgdorferi following a tick encounter increased from 4% to 8%. While the overall risk remains low in most of the province, the risk of exposure is much higher in tick-endemic areas such as Lake Erie, Prince Edward County and parts of the 1000 Islands. In Long Point, Lake Erie in particular, the proportion of deer ticks infected with B. burgdorferi was ~ 60% in a study published from 2009 (R. Lindsay, Public Health Agency of Canada).
Despite the current low prevalence of deer ticks in the Hamilton area, there is an increasing need for awareness of ticks and tick-borne diseases. We cannot currently predict the pattern or speed of tick migration in Ontario, however we can be certain that tick numbers will continue to increase. After going for a walk in the woods or tall grass, owners should be checking themselves and their pets for ticks. If a tick is found, owners should promptly remove the tick themselves or take their pet to a veterinarian where the tick can be removed and identified. For tips on tick removal, visit the Centers for Disease Control and Prevention (CDC) website. Avoid compressing the tick’s abdomen during removal – this can result in reflux of infective organisms into the host. Also remember that ticks need to be attached for a minimum of 24 hours before transmission of B. burgdorferi occurs – therefore, the earlier we spot and remove ticks, the less likely both dogs and humans are to contract disease.
For more information on Lyme Disease in humans please visit the following link: http://www.health.gov.on.ca/en/public/publications/disease/lyme.aspx
References:
Peregrine, Andrew. “Current hot topics in clinical parasitology”. Powerpoint Slides. Ontario Veterinary College. October 21, 2014.
Fig. 1. “Dermacentor variabilis (Say) (female)”. USA, New Jersey, Morris Country, Gilete, April 3, 1953. Image credit: W. Lam, E.H. Strickland Entomological Museum, University of Alberta. <http://entomology.museums.ualberta.ca/browse_results .php?b=ticks&r=14&ref=s&o=1&c=6#>
Fig. 2. “Ixodes scapularis Say (female)”. Canada, Ontario, October 4, 2004. Image credit: W. Lam, E.H. Strickland Entomological Museum, University of Alberta. <http://entomology.museums.ualberta.ca/browse_results.php?b=ticks&r= 14&ref=s&o=2&c=6>
