L.M. Otero / AP
In this Aug. 16, 2012, file photo, mosquitoes are sorted at the Dallas County mosquito lab in Dallas. Infectious diseases that used to be unknown in Nevada could become a greater threat here as mosquitoes associated with maladies such as the chikungunya virus spread around the globe.
Sunday, Aug. 28, 2016 | 2 a.m.
Did you know?
Nurseries, junk yards, cemeteries and flood washes can be ripe for mosquito breeding because of the likelihood of stagnant water and debris.
Talk of the mosquito-borne Zika virus has dominated the news lately, due to the recent Olympic Games in Brazil and the diagnosis of more than a dozen people in Florida infected by local mosquitoes. Zika so far isn’t a direct threat to Southern Nevada, as the main mosquito species that carries the disease hasn’t been found in our region. However, mosquitoes carrying other diseases have made their way to the valley. Some found in July tested positive for West Nile virus, and a sharp increase in mosquitoes carrying St. Louis encephalitis triggered the Southern Nevada Health District to issue a warning in June.
Found in Southern Nevada:
Culex
• Prime biting time: Evening to morning
Viruses spread:
• West Nile virus: Mosquitoes become infected with West Nile virus when they feed on infected birds; humans and other animals become infected when they’re bitten by an infected mosquito. No medication exists to treat or prevent West Nile virus. The Southern Nevada Health District on Aug. 23 reported its first human case of West Nile virus in 2016. A woman over the age of 50 was hospitalized with a more serious neuroinvasive form of the illness but has since been released.
Most people, about 80 percent, infected with West Nile virus show no symptoms. In the other 20 percent, symptoms usually are mild and flu-like — fever, headache, body ache, nausea and skin rash — although some, particularly the elderly and immunocompromised, can suffer vision loss, numbness, paralysis or death.
West Nile has been detected in all lower 48 states, and outbreaks of the disease have occurred in the United States every summer since 1999. The first human cases of West Nile in Clark County were reported in 2004. Every year since then, except 2010, the virus has been found in both humans and mosquitoes. Southern Nevada health officials say West Nile virus is endemic in Clark County.
• St. Louis encephalitis: St. Louis encephalitis is transmitted to mosquitoes from birds. Flu-like — most cases are mild and characterized either by no symptoms or by fever and headache. Severe cases can cause confusion, coma and seizures. Risk for severe symptoms increases with age.
Last week, health officials confirmed reports of the first human case of St. Louis encephalitis in Clark County since 2007. A man over the age of 50 was hospitalized but has since been treated and released.
Not found in Southern Nevada:
Aedes aegypti, aedes albopictus
• Prime biting time: Daytime, although they also can bite at night
Viruses spread:
• Dengue: Dengue can be caused by four types of viruses, all of which are transmitted through a mosquito bite. There is no treatment for dengue, although most people recover in about two weeks. Classic dengue typically causes headache, high fever and muscle pain. The more severe dengue hemorrhagic fever can cause bleeding, bruising and blood vessel damage, while the most severe dengue shock syndrome can cause massive bleeding and death, particularly in children and young adults.
About 400 million people worldwide are infected with dengue yearly. However, the disease rarely occurs in the continental United States.
• Zika: The Southern Nevada Health District, as of July, had tested 65 people for the Zika virus. Seven tested positive; all were travel-associated infections.
Health officials say it’s only a matter of time until the types of mosquitoes that transmit the Zika virus are found in Southern Nevada, as those species already have been identified in California and Arizona. A study indicated that Culex mosquitoes could carry Zika, as well, but thus far it’s unclear whether they have spread the disease.
• Chikungunya: Chikungunya is spread when a mosquito feeds on an infected person, then passes the virus to other people through bites. No vaccine or treatment for the disease exists. The most common symptoms include fever and severe joint pain in the hands and feet.
There have been only a few documented cases of Chikungunya in the United States, and those residents acquired the illness while traveling.
Mosquito-proof yourself
Life cycle of a mosquito
1. Female mosquitoes lay eggs in collections of stagnant water. The eggs, when submerged, hatch in a few days. However, they remain viable even when dry and can hatch months later when resubmerged in water.
2. Mosquito larvae live in water and develop into pupae in about five days.
3. Pupae develop into flying mosquitoes in two to three days. Mosquitoes have a lifespan of about three weeks.
Mosquitofish
Large numbers of small, silver fish have helped control mosquitoes in Southern Nevada and elsewhere. The Gambusia affinis, also known as the mosquitofish, eats mosquito larvae almost as fast as the larvae hatch, with each fish eating up to 100 per day. The fish have been among the most effective nonchemical methods of pest control. The Southern Nevada Health District maintains an 800-gallon tank in which it breeds mosquitofish to stock in local bodies of water, distribute to municipalities and hand out to the public.
• Cover up: Wear long-sleeved shirts and long pants when outdoors.
• Use insect repellent:
• Use a U.S. Environmental Protection Agency-registered repellent with one of the following active ingredients: DEET, Picaridin (also known as KBR 3023, Bayrepel and icaridin), oil of lemon eucalyptus, para-menthane-diol or IR3535.
• Reapply every few hours.
• Do not spray under clothing.
• If you also want protection from the sun, apply sunscreen first, then repellent.
• To apply to a child’s face, spray the repellent on your hands, then rub on the child’s face. Do not apply repellent to his or her eyes, mouth or hands.
Important: Do not use repellent on infants younger than 2 months, and do not use products containing oil of lemon eucalyptus or para-menthane-diol on children under 3.
• Wear treated clothing and gear. Boots, pants, shirts, socks and tents can be treated or bought pretreated with permethrin, an insecticide. Do not use it directly on skin.
Mosquito-proof your home
• Use screens on windows and doors; repair holes in screens.
• Use air conditioning to cool rather than open windows.
• Once a week, empty and scrub, turn over, cover or throw out items that hold water, such as tires, buckets, planters, toys, flowerpots, birdbaths, trash cans and the like.
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