No human cases of West Nile reported yet
The mosquito-borne West Nile virus has yet to infect any Albertans this season, according to Alberta Health.
In fact, no human cases have been reported to the Public Health Agency of Canada from across the nation as of July 19.
In 2013, Alberta saw 21 West Nile cases with one fatality. Three cases were in Central Alberta.
There were 115 clinical cases across Canada in 2013 and five people died.
Humans infected with West Nile virus can develop either West Nile non-neurological syndrome or West Nile neurological syndrome.
Symptoms of the non-neurological version include fever, chills, nausea, vomiting, fatigue, skin rash, swollen glands and headaches.
The neurological version can be more severe, with tremours, drowsiness, confusion, swallowing problems, high fever, unconsciousness, paralysis and even death.
Last year, the first few Alberta cases occurred in mid-August, including the first case in Central Alberta.
Dr. Martin Lavoie, the province’s deputy chief medical officer, said West Nile-infected mosquitoes are probably around right now and have bit people, but it takes about a week for someone to become infected and more time for them to seek medical assistance.
And 80 per cent of people don’t have symptoms, he said.
“Most people don’t have any symptoms at all. A small proportion will have some symptoms, about 20 per cent, and rarely will it be severe, less than one per cent,” Lavoie said.
He said there is no antiviral medication for West Nile and complications are more likely in the elderly.
The risk of infection is higher in Southern Alberta because of higher temperatures that spur on the mosquito population, he said.
“There is always a risk of West Nile. It will vary from year to year. We know it’s here, we just need to make sure we protect ourselves.”
Precautions include wearing a long-sleeved, light-coloured shirt, pants and a hat; using insect repellent with DEET, and staying indoors at dawn and dusk when mosquitoes are most active.
Alberta Environment and Sustainable Resource does not monitor Alberta’s mosquito population, but the province did in the past.
AESR spokesperson Carrie Sancartier said from the perspective of climate change, it’s hard to predict the impact on mosquitoes.
“On one hand, warmer weather can speed up the development of larvae of mosquitoes that carry the disease. But on the other hand, it can also dry up the pools where mosquitoes breed. So there’s no definitive answer at this point on what the impact would be,” Sancartier said.
Trevor Poth, Red Deer Parks Department superintendent, said long periods of dry weather this summer did trim the local mosquito population.
City staff have treated pockets of standing water four times this season, including a treatment that will be underway this week due to recent rain.
“We’re really anticipating a very standard treatment. We’re not expecting it to be booming population at all,” Poth said.
By this time last year, five treatments had been done, with a total of seven for the season.
“Generally, this has been a very typical year for mosquitoes.”
The city uses a microbial pesticide called bacillus thuringiensis israelensis (Bti) on ponds where mosquito larvae will hatch. It is used to treat the aquatic larval stage of the mosquito life cycle before it emerges as an adult.
Bti is non-chemical product that only kills mosquitoes. It does not affect fishing waters, other aquatic organisms or birds.
Dragonflies are also taking a bite out of local mosquitoes.
“We should see dragonfly populations right through until September. Their populations are doing amazing,” Poth said about the mosquito-eating insects that have benefitted from the hot weather.
He said residents can encourage dragonflies to visit their yards by having pollinator gardens with flowers and shade and a small water source where dragonflies will check for mosquitoes.
“The best thing to do is use a small bird bath with a few stones in it so that there’s landing platforms in the water itself.”
Just make sure to dump the water every couple of days and refill it so mosquito larvae can’t hatch, he said.
To learn more about West Nile and risk-reducing precautions, visit www.fightthebite.info or call Health Link Alberta at 1-866-408-5465.