The NWT government has issued an internal advisory warning healthcare professionals to be on the lookout for more mosquito-borne diseases as the territory’s climate changes.
In late June, Dr Kami Kandola – the territory’s chief public health officer – circulated a notice that stated: “With climate change and resulting changes to animal reservoirs, the physical environment, and mosquito vectors, California serogroup virus infection incidence could increase in NWT.”
California serogroup viruses are a class of 18 related viruses carried by mosquitoes, at least seven of which have been shown to cause neurological disease in humans.
The three best-known such viruses in North America are Jamestown Canyon virus, snowshoe hare virus, and La Crosse virus. La Crosse virus has so far not been detected in Canada.
Though Dr Kandola’s advisory did not state the NWT had experienced any increase in California serogroup cases among humans, there has been at least one recent confirmed diagnosis in the territory of meningoencephalitis – a severe neurological condition – linked to snowshoe hare virus.
Kandola said California serogroup infections were “infrequently diagnosed but … have occurred in all provinces and territories.”
The warning comes as summers in the NWT get hotter and last longer, making it easier for mosquito-borne viruses to thrive.
A spokesperson for the territory’s Department of Health and Social Services said Kandola had sent the notice after “mosquito surveillance conducted by the Department of Environment and Natural Resources determined some mosquitoes in the NWT had the California serogroup viruses.”
Taz Stuart, an entomologist and mosquito specialist who has worked in the territory, said diseases carried by mosquitoes are only now becoming a problem in the NWT.
“Three years ago, summer was two months if you were lucky,” Stuart told Cabin Radio. “That’s not enough time for most mosquitoes to be infective and transmit viruses to other animals or humans.”
The journey from viral host to human is not a straightforward process, Stuart said. California serogroup viruses originate in animals like deer, squirrels, and hares. A mosquito will become infected after feeding on these animals. Extended seasons give mosquitoes longer breeding periods, increasing the likelihood of transmission to humans.
“With longer seasons now hotter, conditions are more conducive in the Northwest Territories for the potential for California serogroup viruses to spread, and that does also include the potential for West Nile,” Stuart said. While most people suffer few or no symptoms, West Nile virus – which is not part of the California serogroup – can cause encephalitis or meningitis and, in a small number of cases, proves fatal.
The NWT government’s notice to healthcare providers asks them to “be vigilant for California serogroup virus,” consider that possibility when diagnosing patients, and report any confirmed or suspected mosquito-borne infections to Kandola’s office.
As any resident knows, the NWT is full of mosquitoes during the summer. They are all but impossible to completely avoid.
“You always want to use personal protection measures: wearing appropriate DEET repellent, or a keratin repellent.” Stuart said.
If you have standing water in your back yard, Stuart recommends treating it to avoid it becoming a mosquito breeding ground.
The warning about California serogroup viruses means “you should be a little more aware of personal protection measures to keep yourself from not getting bitten,” he concluded.
“The risk of getting the virus is low,” said the spokesperson for the Department of Health and Social Services. “Those who do get it usually do not develop symptoms. However, severe illness – though rare – can occur.
“The Office of the Chief Public Health Officer recommends healthcare providers to have awareness during mosquito season if individuals present with signs of severe illness, and consider differential diagnosis.”