West Nile Virus, the mosquito-born illness that has killed 67 people this year and infected more than 1,500 in the U.S., is a concern for Southeastern North Carolina, said UNC Pembroke entomologist and mosquito researcher Dr. W. Bruce Ezell.
The region’s moist and relatively cool weather recently is the perfect environment for breeding mosquitoes. The Center for Disease Control said 2012 has been a bad year for the West Nile Virus. Almost half the cases reported have been in Texas, compared with two deaths in North Carolina.
“There is cause for concern,” Dr. Ezell said, “and it is worthwhile for us to take some precautions.”
The UNCP scientist gave this advice for avoiding contact with mosquitoes:
- Plan activities when mosquitoes are less active. They thrive on the cooler temperatures at dawn and dusk.
- Wear protective clothing and light colored clothing. Mosquitoes favor dark colors.
- Eliminate standing water. Eliminate water standing in tires, ditches, gutters, tree holes, unused swimming pools and any container that collects rainwater.
- Use insect repellant with DEET
“Our best course now is to inform the public about these precautions,” Dr. Ezell said. “Source reduction is important.”
Mosquitoes, which are beneficial sources of food for some species of birds and fish, have a long and unhealthy relationship with humans. The number one killer on the planet is mosquito-born malaria, Dr. Ezell said.
As many as four mosquito species have been linked to West Nile Virus, although there may be more, according to Dr. Ezell. It is one of many viruses, which are increasing in number because we live in a more connected world.
The West Nile Virus is an “arbovirus” or arthro/pod/borne/virus and, in this case, mosquito-borne. Birds, which carry the virus, are called “viremic” carriers that are not affected by the disease.
Dr. Ezell said more research is needed, but for the virus to be transmitted to humans, the mosquito must have first taken blood from a bird.
“Humans are the second blood meal in this case,” he said. “This may be a limiting factor in the spread of the disease because one blood meal is usually sufficient.”
Dr. Ezell conducted research on mosquitoes at Clemson University and other schools and later for the Army Corps of Engineers on coastal mosquito issues. He is particularly knowledgeable of the mosquito life cycle, which takes 18 – 22 days from egg to adult.
“Mosquitos larvae require stagnant and absolutely still water to survive,” he said. “Mosquitoes can lay eggs on moist earth or even dry earth that has a history of collecting water. The eggs survive until water returns.”
When the adult mosquito emerges and mates, the trouble begins for humans.
“After mating, they are desperate for a protein source, and vertebrate blood is the best source,” Dr. Ezell concluded.
About a fifth of those infected with West Nile Virus will develop a fever, headaches, tiredness, body aches, swollen lymph glands and possibly a skin rash that may last only a few days or a few weeks. Most people infected by the virus will have no symptoms.
However, severe or neuro-invasive cases may develop West Nile encephalitis or meningitis or poliomyelitis. This results in headaches, neck stiffness, disorientation, tremors, convulsions, weakness, paralysis and coma. An estimated one in 150 persons infected with West Nile Virus develop severe symptoms, which may result in death or lasting neurological damage.
Although there is no treatment for the infection itself, the person with severe disease often needs to be hospitalized. Care may involve nursing, IV fluids, respiratory support and prevention of secondary infections.