West Nile Virus and Lyme Disease in Ottawa

From Ottawa Public Health

West Nile Virus and Lyme Disease in Ottawa

Ticks and mosquitoes have the potential to spread infections to residents of Ottawa. Lyme Disease and West Nile Virus (WNV) are two of the most prevalent diseases.

What is Lyme disease?

Lyme disease is an infection caused by Borrelia burgdorferi, a bacteria transmitted through the bite of an infected blacklegged tick (Ixodes scapularis), most commonly during the spring, summer and fall months. If a person finds a tick on their body, they should remove it as soon as possible. The risk of Lyme disease increases the longer the tick is attached.  Blacklegged ticks in Ottawa are known to carry this bacterium. Ottawa Public Health (OPH) recommends that, if a person finds a tick on their body that may have been attached for more than 24 hours, they should speak to a healthcare provider or pharmacist. The healthcare provider or pharmacist will provide recommendations on what to do. Next steps may include monitoring for symptoms for the next 32 days and, if appropriate, taking post-exposure prophylaxis (antibiotics). Early signs of Lyme disease occur three to 32 days following a tick bite. This may include an expanding, circular rash, which may look like a “bull’s eye,” but is not present in all cases. Other symptoms can include fatigue (tiredness), fever, headache, swollen lymph nodes, and muscle and joint pain. If untreated, the infection may cause additional rashes on other areas of the body, fatigue, weakness, and may harm the heart, liver, nerves and joints.

What is West Nile virus?

West Nile virus (WNV) is a disease primarily spread to humans by infected mosquitoes. Mosquitos, especially the Culex type, become infected with WNV when they feed on infected birds. They can then spread the virus to humans and other animals by bites. It can take between three and 14 days before symptoms occur after being bitten by an infected mosquito. Most people infected with WNV will remain asymptomatic, but approximately 20% will develop symptoms of usually mild (through to sometimes debilitating) febrile illness, which may include headache, fatigue, body aches, rash, nausea, and vomiting. Less than 1% of those infected may develop severe neurological illness. In Ontario, locally acquired WNV occurs in the summer months, with the majority of cases occurring in August and September.

What is OPH’s Role?

OPH works to prevent Lyme disease and West Nile virus through a variety of measures, including:

• OPH investigates every report of a person being infected with WNV to identify the likely source of infection and, where appropriate, takes action to minimize further risk to the population.

• OPH conducts epidemiological surveillance of reported infections of Lyme disease and WNV to identify trends and populations at risk.

• OPH, in partnership with University of Ottawa researchers, conduct tick surveillance to assess their spread and the presence of pathogens like Lyme disease. OPH conducts surveillance and management of mosquito populations through its West Nile Virus Prevention Program.

  • Mosquito traps are placed around the city to determine species and densities of mosquitoes, with tests for WNV carried out weekly.

  • OPH contracts services to apply Ministry of the Environment, Conservation and Parks approved products. A biological larvicide (Bacillus thuringiensis subspecies israelensis – Bti) is used on surface waters such as ditches and storm water management ponds as needed throughout the season. A chemical larvicide (methoprene) is used to treat non-surface waters, such as roadside catch basins.

  • If homeowners have a backyard catch basin they would like to have treated, they can contact OPH at healthsante@ottawa.ca.

• OPH provides information to healthcare providers to aid in clinical diagnosis.

• OPH also conducts public education on tick and mosquito bite prevention.

• If necessary, conduct mosquito control using adulticide (malathion), based on assessment of increased transmission and risk. No adulticide treatment has been used to date in the history of OPH’s West Nile Virus Prevention Program.

How can individuals protect themselves from these infections?

• Apply a Health Canada approved insect repellent containing DEET or icaridin to exposed skin and clothing

• Wear long pants, a long-sleeved shirt, shoes, and socks to cover exposed skin

• Tuck your pants into your socks

• Wear light-coloured clothing to spot ticks more easily; this is also appropriate for mosquitoes as they are attracted to darker colours

• Stay on the trails when hiking in the woods and other natural areas. Enjoy the mowed/maintained areas in parks and playing fields, while being mindful of tick habitat, such as tall grass and leaf litter.

• For ticks, do a "full body" check on yourself, your children, and pets. Pay careful attention around your toes, back of the knees, groin, armpits and scalp

• For mosquitoes, avoid being outside during dusk and dawn - periods when they are most active – and at any time in shady, wooded areas. Remember to use repellent and protective clothing if you must be out during these periods

• Make sure all windows and doors in your home have well-fitting screens that are in good condition to prevent mosquitoes from entering

• Mosquitoes need water to breed.  Decrease mosquito numbers around personal property by reducing or eliminating areas or objects that can accumulate or retain water (e.g., old tires, garbage or recycle containers, flowerpots, toys, bird feeders, ornamental ponds, pool covers, etc.). Empty and refill them regularly, turn them over when appropriate, or dispose of them accordingly.

For more information about West Nile virus and Lyme disease, visit the OPH website at Insects, Animals and Bites - Ottawa Public Health