Standing Water Logan Hawkes
Standing water following torrential rains and flooding from Hurricane Harvey poses a health risk--mosquitoes.

Hurricanes and floods not the only thing hampering recovery in Texas

Not the least of worries, and a concern that is growing as each day passes, is the rapid population explosion of mosquitoes and the diseases they may be carrying.

Nearly two weeks after Hurricane Harvey ravaged the Texas coast, flood waters are still receding in hard hit areas across the mid and upper coast of Texas and in parts of Louisiana. More than 25,000 residents remain in shelters, hotel and motel rooms or at the homes of relatives or friends.

In cities, communities and across large parts of rural areas, families are still digging out, shoring up and trying to put their homes and often their lives back together. For most it has been a struggle. Federal, state and local officials have been joined with a mounting number of volunteers to help in the cleanup. Rummaging through damaged or destroyed homes for personal property is an ongoing project for many, and debris removal continues.

There is plenty of work yet to do. Roads, bridges and dams need repaired, utility crews are still attempting to restore power to many customers, especially in rural areas. Farmers and ranchers are still assessing damage to crops, equipment and structures, while many continue to search for lost cattle or other livestock.

Diligent work continues, but under less than ideal conditions. Many storm-ravaged areas are troubled by heat and unbearable humidity, workers often wishing or searching for an air conditioned cafe or coffee shop in areas that still have electricity for respite from the heat of the late summer sun.

Officials in Houston and Baytown and as far south down the coast as the Port of Corpus Christi are warning of the dangers from standing water and polluted tributaries near the coast. Environmental officials warn of the possibility that bays and channels are contaminated from sunken vessels or barges— fuel and the petrochemicals they carry leaching into the waterways. Some have no fresh running water for drinking or bathing.

MOSQUITO INVASION

Not the least of worries, and a concern that is growing as each day passes, is the rapid population explosion of mosquitoes and the diseases they may be carrying. Jason Ott, Nueces County agricultural agent in Corpus Christi, says mosquitoes go from egg to adult in 4 to 14 days, depending on conditions. The process of development from egg to adult takes less time when the weather is hot.

"Mosquitoes are aquatic in all but the biting adult stage. Eggs, larvae and pupae must have water to mature into blood-feeding adults," he said. "Adult mosquitoes emerge from the aquatic pupal stage and begin to feed. Males feed on nectar [while] females feed on nectar initially, but then they must feed on blood to produce eggs."

According to the Environmental Protection Agency (EPA), all mosquito species go through four distinct stages during their life cycle, from egg hatch as larvae, mosquitoes progress to pupae and then adult stage. The first three stages occur in water, but the adult is an active flying insect. But only the female mosquito bites and feeds on the blood of humans or other animals. After she obtains a blood meal, the female mosquito lays her eggs directly on or near water, soil and at the base of some plants in places that may fill with water. The eggs can even survive dry conditions for several months.

MOST DANGEROUS CREATURE

According to the Center for Disease Control in Atlanta, mosquitos may well be the most dangerous creatures on earth. The Illinois Department of Public Health claims the diseases mosquitoes spread have been responsible for killing more people than all the wars in history. Even in modern times, mosquitoes transmitting malaria kill 2 to 3 million people and infect another 200 million or more globally every year. Tens of millions more are killed and debilitated by a host of other mosquito-borne diseases, including filariasis, yellow fever, dengue, and encephalitis.

 In the United States, encephalitis, meningitis and other diseases can develop from the bites of mosquitoes infected with certain viruses. These include the viruses of West Nile, St. Louis encephalitis, LaCrosse (California) encephalitis, and Eastern equine and Western equine encephalitis. In more recent years however, a new threat has emerged—Zika virus.

Zika is transmitted to humans primarily (but not limited) to two specific mosquito species. These are the same type of mosquitoes that spread dengue and chikungunya viruses. Zika virus in humans is usually mild with symptoms lasting up to a week, and many people do not have symptoms at all, or will experience only mild discomfort. However, a Zika virus infection during pregnancy can cause a serious birth defect called microcephaly along with other severe brain defects.

Most mosquito species bite actively at dusk and dawn, however, the two mosquito species that transmit the Zika virus and many other diseases – Aedes aegypti and Aedes albopictus - bite during daytime, and at dusk and dawn.

Over all, mosquitoes can be described in two groups, depending on where the eggs are laid. One type is floodwater mosquitoes. They lay their eggs on moist soil in areas prone to flood. The eggs lay dormant on the soil surface until the site floods again, at which point the eggs will hatch. Some eggs are weather resistant and can withstand desiccation for up to two years. Summer flooding often results in large populations of these biting floodwater mosquitoes. Floodwater mosquitoes are typically aggressive and deliver a painful bite. But floodwater mosquitoes are not considered primary in human disease transmission.  

The second group of mosquitoes lay eggs in standing water. Some prefer to lay eggs in water-filled tree holes, while others prefer artificial containers. Some of these mosquitoes are major players in the transmission of human disease,

PREVENTION IS CRUCIAL

"Prevention of mosquito bites and disease outbreaks will require taking steps to disrupt the mosquito life cycle.  Mosquitoes must have food, shelter, and water to live. Remove any one of these – especially standing water – and they cannot survive.  Without water, there are no larvae," Ott explained. 

"The most effective thing people can do to reduce mosquito populations is to eliminate standing water.   Gutters, boat tarps, under-treated swimming pools, tires, toys, buckets, bird baths, water features, catch dishes under potted plants, cans, bottles, and other containers are all locations that can hold enough water for mosquitoes to breed. When dealing with mosquitoes and mosquito-borne disease, anything that will hold water is a problem, so eliminating these types of items around the house or on the farm will reduce mosquito populations."

As far as the best way to avoid mosquito bites, experts say simply avoid them. And the best way to that is a generous application of a mosquito repellent containing Deet. A remarkably effective alternative is a commercial lemon eucalyptus repellent.

In a 2015 study, Deep Woods repellent containing Deet provided a 94 percent reduction in mosquito attraction upon application, and four hours later it was still providing protection equal to 71 percent reduction in attraction. By comparison, Cutter's lemon eucalyptus repellent provided 91 percent reduced attraction at application and 82 percent reduced attraction four hours later.

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