West Nile virus positive horse reported in Greater Sudbury

Public Health Sudbury & Districts has received confirmation that a horse in the Greater Sudbury area has tested positive for West Nile virus. The last infected horse reported was in 2024. This is the third animal that has tested positive this year, with two crows testing positive in the summer. The most recent report of a person testing positive was in 2023.

“Although the overall risk of a person becoming infected remains low, late summer and early fall are typically the time of greatest risk for contracting West Nile virus as mosquitoes can carry higher levels of the virus at this time of year,” said Jonathan Groulx, a manager in Public Health Sudbury & District’s Health Protection division. “Therefore, continuing to take precautions even late in the season is important to avoid becoming infected.”

The One Health approach in Ontario emphasizes that human, animal, and environmental health are interconnected. By monitoring cases in humans, along with animal health and mosquito populations, public health authorities, health care providers, veterinarians, and environmental experts can better predict, prevent, and control the spread of West Nile virus.

West Nile virus is spread through the bite of an infected mosquito. It cannot be passed directly from horses to humans or other animals. Most people infected with the virus have no symptoms, but some people may experience mild symptoms including fever, headache, body aches, mild rash, and swollen lymph glands. In very rare cases, infection can affect the brain and cause severe illness.

Early symptoms in horses include fever, muscle twitching, hypersensitivity to touch or sound, and difficulty standing. Keeping horses up to date on vaccines and boosters is the most effective way to protect them against West Nile virus.

Simple measures can reduce the risk of West Nile virus.

Reduce the risk around the home

• Install or repair screens. Some mosquitoes like to come indoors. Keep them outside by having well-fitting screens on all your windows and doors.
• Remove standing water from around your home where mosquitoes can breed.

Personal precautions

• Avoid going outside at dusk and dawn, as these are peak times for mosquito activity.
• Wear light-colored, long-sleeved shirts, long pants, shoes, and socks when outside.
• Use an approved insect repellent and be sure to follow the manufacturer’s recommendations.

Precautions for horse owners

• Stabling horses at dawn and dusk, when mosquitoes are most active.
• Using fans in barns to deter mosquitoes.
• Applying veterinarian-approved insect repellents.

For more information about West Nile virus, please contact Public Health Sudbury & Districts at 705.522.9200 ( toll-free at 1.866.522.9200) or visit phsd.ca.

For further information about West Nile virus and horses, contact:

• Ontario Ministry of Agriculture, Food and Rural Affairs
  Agricultural Information Contact Centre: 1-877-424-1300 or info@omafra.gov.on.ca
• Ministry of Health INFOline
  1-877-234-4343 (Toll-free in Ontario only)
  TTY 1-800-387-5559