East Wetlands sees increase of West Nile-positive mosquitoes
Pest control agencies from Yuma County and the Cocopah and Quechan tribes have been treating the East Wetlands area of Yuma with insecticide after recent samples have shown a dramatic increase in the number of mosquitoes infected by West Nile Virus.
Elene Stefanakos, manager of the Yuma County Pest Abatement District, said the infection rate has been relatively low over the last two years, but this summer they have skyrocketed in the East Wetlands and some South County areas.
Authorities have begun using planes to deliver chemicals targeting mosquito larvae about once a week, she said.
“Every other night, either us or the city with the Quechan are out there fogging, trying to kill all the adult population, but we’re still seeing a huge number of West Nile-positive pools,” she said.
Last week, she said nearly half of the samples collected by her agency tested positive for the virus, 34 out of 75. “That’s not normal,” she said, adding that levels have been high statewide this year.
No human West Nile Virus cases have been reported from Yuma County as of Friday, according to the Arizona Department for Health Services, with most confirmed cases coming from Maricopa County.
The same report said a total of 70 mosquito samples have tested positive for West Nile Virus in the county this year, behind only Maricopa’s 170. Pinal is the only other that’s reported any, with five positive samples.
Stefanokos said most of the infected pools have been found in the East Wetlands, but have been found as far northeast as the confluence of the Colorado and Gila Rivers and as far south as the Cocopah water tower, on the tribe’s west reservation outside of Somerton.
She said the likely reason more mosquitoes are infected here this year is because more of the bird population in the area did not have immunity to it.
“If you don’t see it for a couple of years, it’s like the flu. If we have the flu, and then a new strain comes in, nobody has immunity and everybody’s going to get sick,” she said.
After a mosquito bites an infected bird, it can then spread West Nile by biting humans, horses or other animals.
About 70 percent to 80 percent of people who are infected will experience no symptoms, according to the Centers for Disease Control. Another 20 percent experience fever and other flu-like symptoms.
Less than 1 percent may develop encephalitis, meningitis or another severe neurological condition, which can be fatal. Symptoms can include headache, high fever, stiff neck, disorientation, and coma.
Diana Gomez, director of the Yuma County Public Health Services District, said a locally acquired case of West Nile has never been reported for the county.
“This is largely due to proactive efforts to identify, test, treat and eliminate potential mosquito breeding sites,” she said.
But the most important preventive measures are taken by residents who wear protective clothing or use insecticide when in mosquito-prone areas, eliminate standing water or other potential breeding sites at home, and report green pools and other hazards.
Stefanokos said residents should be aware of their surroundings at night, when the culex tarsalis mosquitoes which are most prevalent in the area are buzzing.
“It comes out when the sun sets and stays active during the nighttime period, and becomes dormant at sunrise.
“So we wanted to let people know that it’s a really good idea to wear clothing that covers their arms and legs if they’re out fishing or sports, or anything near any water areas or Yuma East Wetlands area. And if not then definitely wear an EPA-approved insect repellent, because this particular species hates the insect repellent, and it’ll stay away from you.”
She said the county Pest Abatement District, which covers mostly unincorporated areas around the city of Yuma, has been working closely with the Yuma County Vector Control District, which covers most of the city of Yuma, and tribal authorities to control the spread of West Nile virus.