Mosquito study underway in B.C.’s Sea-to-Sky region after scattering of severe illness

A small number of virus cases in B.C. last year has triggered a study in the Sea-to-Sky region of mosquito populations and the diseases they may carry.

A small-scale mosquito surveillance project is being launched in B.C.’s Sea-to-Sky region to better understand the mosquitos in the area and what diseases they may be carrying.

The project, launched by Vancouver Coastal Health in collaboration with the B.C. Centre for Disease Control, Líl̓wat Nation, Squamish Nation and the University of B.C., was prompted after a spate of mosquito-borne illness was reported in the region late last year.

“Late last year in the fall, we were notified of a small cluster of individuals who were diagnosed with an illness known as California Serogroup, and they had all presented with severe neurological symptoms of encephalitis,” said Dr. Moliehi Khaketla, medical health officer for Vancouver Coastal Health. Encephalitis is an autoimmune response that leads to a swelling of the brain.

According to Khaketla, the majority of people who contact the virus show “mild to no symptoms” and it is only “a very small proportion” of individuals that have these severe neurological presentations.

While the specific infection was not new to the province, it was notable that four cases occurred over the course of one summer and that the severity of those cases meant the infected required hospitalization, said Khaketla. Prior to these four cases, there had been only three cases of California Serogroup reported since 2009.

“We decided to investigate to better understand if these individuals had acquired this illness while traveling to another area, or if they had stayed locally in B.C., and we determined that they had all likely acquired this new emerging pathogen locally in the Sea-to-Sky region, which was new,” said Khaketla.

The project, due to last three months, may be extended to allow surveys of other regions in B.C. if new cases arise.

“Because this is an emerging pathogen, this is our first step to being able to better understand this problem,” Khaketla said. “Depending on how these results go, and if we see new additional cases this summer of this illness, it may prompt other regions across B.C. to conduct something similar.”

As the study gets underway, VCH is highlighting the importance of preventing mosquito bites and the various ways that they can be protected against. Khaketla recommends wearing mosquito repellents, wearing clothing that covers more skin – like full-length pants or long-sleeved shirts – installing screens on windows and avoiding being outdoors during times when mosquitoes are more active, typically around dusk and dawn.

Removing sources of stagnant water, where mosquitos can breed, may also remove the risk, he said.

“That could be simple things like removing the water under saucers or flowerpots, or changing bird baths, or unblocking your rain gutters, things like that,” he said.