Mosquitoes are out

People encouraged to protect themselves

Mosquito season is in full swing and the insects aren’t just nuisances, they can be dangerous.

There’s a whole list of diseases they carry depending on the insect — Zika, West Nile, Malaria and others. Of course it can depend on what part of the United States or which foreign country someone visits for some, but other disease opportunities are right here in Plumas County and the state.

Mosquitoes

It seems there is a scientific reason why mosquitoes like some people and almost never bite others — it’s all in the blood. Or rather close to it.

Actually there are two main reasons why mosquitoes are attracted to some people and not others.

Sight and smell seem to have a lot to do with why a mosquito is attracted to particular humans.

Mosquitoes use their eyes to find a target, according to Jonathan Day, a professor of medical entomology at the University of Florida in Vero Beach. Especially in the late afternoon, mosquitoes are more apt to be out scouting for food.

Mosquitoes, it turns out, have highly developed vision. And people who are wearing dark clothing, especially navy and black and sometime red are easy for them to spot, Jay said.

In other words, tend to wear light-colored clothing to avoid detection by mosquitoes that are out for blood.

The tiny, buzzing insects also have a keen sense of smell. Adult mosquitoes are out for nectar, but female mosquitoes rely on the protein they find in blood for egg production.

People with Type O blood are highly favored for mosquitoes to zero in on. They really don’t care for Type A blood. Type B people seem to be in the middle. They won’t attract as many mosquitoes as those with Type O blood, but they’re not as fortunate as those with Type A blood, according to scientific studies.

When out for blood, mosquitoes smell for people who produce a secretion that signals to them just what blood type they are. According to research, 85 percent of the population produces the secretion that signals blood type. It’s the non-secretors who are the most fortunate.

Carbon dioxide also plays a big part in a mosquito’s well-being. They can sense it up to 160 feet away. So as people breathe out carbon dioxide mosquitoes know about it. That’s also why the insects seem to like our faces and heads.

Mosquitoes also detect lactic acid, uric acid, ammonia and sweat. A hot, sweaty person makes a good lunch for mosquitoes.

Exercise, whether it’s mowing the lawn or running, builds up lactic acid in the body, according to Smithsonian Magazine. Mosquitoes, of course, are attracted to the smell.

Genetic factors can also mean more lactic acid and heat within the body.

Our skin also has an impact on weather a mosquito will bite.

Skin bacteria, it seems, makes a difference. Microscopic life lives in abundance on the human skin and it doesn’t matter how clean we believe we are. It produces a distinct fragrance that mosquitoes sense. Of particular interest are the ankles and feet of individuals who happen to have bacteria types that mosquitoes want.

Mosquitoes are also attracted more to some women who are pregnant, according to research. In one study in Africa, pregnant women were twice as likely to attract malaria-carrying mosquitoes as non-pregnant women. Part of this also might be explained by the fact that larger people tend to breathe more frequently; therefore, more carbon dioxide is present to attract insects.

Those who drink beer are also more likely to attract mosquitoes, according to yet another study. It’s the increase in ethanol content in sweat and skin temperature combinations that attract mosquitoes.

Mosquito-borne diseases

Mosquitoes feed by sticking that long, needle-like mouthpiece into the skin of a human or animal. Female mosquitoes must have blood in order to lay eggs, which they deposit in standing water.

Mosquitoes can carry a number of diseases or viruses that they can transmit when they are feeding. These diseases include Aedes aegypti and Aedes albopictus, chikungunya, dengue, malaria, St. Louis encephalitis, West Nile virus and Zika.

Although no West Nile virus cases have been reported in California yet this year, that doesn’t mean it’s over, according to University of California, Davis Arbovirus Research and Training, and the Mosquito and Vector Control Association of California.

WNV was first detected in California in 2003 and is now well established throughout the state. There have been 6,582 human cases and 292 deaths in the state since WNV was first reported.  Nearly 22,000 dead birds with the virus have been collected and nearly 30,000 mosquito samplings have been conducted.

The state also looks at horses; “sentinel” chickens and squirrels are also monitored.

Transmission is by infected mosquitoes to humans and animals that are hosts. Summer and early fall when the temperatures are warm are when mosquitoes are most active and when humans are more likely to contract the disease.

So far this year, four dead birds and one mosquito sampling have been found carrying WNV, according to public health.

The mosquito sampling was conducted in San Bernardino County.

West Nile virus originated in Africa, according to the California Department of Public Health. It is mosquito-borne and was first identified in the U.S. in 1999 in the eastern states.

When Culex mosquitoes feed on an infected bird they spread the disease to humans and animals. The Culex mosquito is found throughout the state. They tend to feed in the morning and evening. The good news is that the Culex mosquito doesn’t carry Zika, dengue or chikungunya viruses in California.

Less than 1 percent of the population or one in 150 infected with WNV will develop severe neurological illnesses such as encephalitis or meningitis — inflammation of the brain or surrounding tissue.

Severe symptoms can include a high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, impaired vision, numbness and paralysis.

The symptoms might last a few weeks, but the neurological effect could be permanent and even fatal.

Up to 20 percent of those who contract WNV will display symptoms that include fever, headache, body aches, nausea, vomiting and sometimes swollen lymph glands or a skin rash on the chest, stomach and back. Acute symptoms can last for a few days although fatigue and weakness can last for weeks or even months.

About 80 percent of the population or four out of every five people who contract WNV show no symptoms.

People who are 60 and older show a greater chance of getting WNV.

There are no vaccines available for West Nile virus. Over-the-counter pain medications can be used to treat milder cases. Severe cases are hospitalized for more intensive care.

Here are a few things that people can do to help protect themselves and others against the disease. The state’s public health program recommends that individuals prevent exposure to mosquito bites and West Nile virus by practicing the three “Ds”: DEET. Apply insect repellent containing DEET, picaradin, oil of lemon eucalyptus or IR3535, according to label instructions. Repellents keep the mosquitoes from biting. DEET can be used safely on infants and children 2 months of age and older.

Dawn and Dusk are when Culex mosquitoes like to feed. People should wear proper clothing — light colors, long sleeves and pants — use a repellent and make sure that doors and windows have tight screens to help keep mosquitoes out of homes. Rain gutters, birdbaths and pet bowls are also to be properly maintained as well as swimming pools or ponds.

Drains are the third thing to consider. Mosquitoes lay their eggs in standing water. By eliminating standing water or maintaining these sources people cut down on places where mosquitoes will breed.

Animals, including pets, are susceptible to WNV, but they are very resistant to it and rarely become sick, according to public health sources.

If someone finds a dead bird, particularly crows, jays, magpies, ravens, sparrows, finches or raptors, they are encouraged to report it at westnile.ca.gov or call toll-free 877-968-2473.

Dead bird reports are often the first indication that the virus is active in a particular area.

It’s all about the mosquito species

While Culex mosquitoes are credited with West Nile virus, non-native species of Aedes Aegypti and Aedes alboprictus are responsible for spreading other diseases in California.

The Aedes aegypti is also known as the yellow fever mosquito. The Aedes albopictus is also known as the Asian tiger mosquito. Both of the species are small and black with white stripes on their backs and legs. They also bite during the day.

Both kinds have the potential to transmit dengue, chikungunya, Zika and yellow fever. None of these are in California at this time, but people can be infected when they travel to other parts of the world, including Mexico, Central and South America, the Caribbean and Asia.

“The presence of Aedes aegypti and Aedes albopictus mosquitoes in California poses a threat that Zika, dengue, and chikungunya viruses can be transmitted in infested areas from returned infected travelers,” according to the California Department of Public Health.

When traveling to the above-mentioned areas people can help protect themselves from potential infection by wearing long sleeves and pants, using an insect repellent, and staying in air-conditioned places or places with window and door screens.

Although these mosquitoes aren’t native to California they have been detected here. To date there has been no detection of Zika virus in California.

Zika has been documented only in people who were infected while traveling to areas with ongoing Zika transmission, through sexual contact with an infected traveler or through maternal-fetal transmission during pregnancy. 

Zika virus during pregnancy can cause microcephaly and other severe brain defects in infants. Additionally, there is an association between Zika and Guillain-Barré Syndrome, a disease affecting the nervous system,” according to public health sources.

Chikungunya is an infectious disease with symptoms that include fever and severe joint pain. These people are not contagious.

Dengue and dengue hemorrhagic fever infestations have been detected in many California counties last year, according to public health.

Dengue is the leading cause of illness and death in the tropics and subtropics, according to the Centers for Disease Control and Prevention. “As many as 400 million people are infected yearly.”​

Early symptoms include high fever, severe headaches, severe pain behind the eyes, joint pain and muscle and bone pain, and mild bleeding from the nose or gums and bruising.

Malaria is probably the most recognizable among the mosquito borne diseases. It is transmitted to humans by the Anopheles mosquito.

“Once an infected mosquito bites a human, the parasites multiply in the host’s liver before infecting and destroying red blood cells,” according to Peter Lam for Medical News Today.

There is no vaccine that is licensed outside of European countries against the disease, but it can be treated and controlled through early detection.

Malaria was eliminated in the U.S. in the 1950s but people who travel can contract it.

Symptoms resemble the flu. Through treatment it can be managed, but it is often long-term and sometimes fatal.

Again, individuals who are planning to travel this summer to areas typically infected are encouraged to follow the recommended process for avoiding mosquito bites.

2 thoughts on “Mosquitoes are out

  • May 21, 2018 at 10:57 am
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    Great article . So informative. Thank you

  • May 21, 2018 at 5:59 pm
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    Mosquitos aren’t the only thing that is out… Ask the plumas county sheriff’s department about their catch and release policy for heroin dealers.

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