As if we didn’t have enough to concern us, we are facing the real possibility of an incursion by an unfriendly mosquito this spring and summer. Many of you have heard about the mosquito-borne Zika virus that has afflicted Brazilians, Mexicans, and Caribbean islanders, but primarily pregnant women, producing thousands of microcephalic infants: babies that will fare badly.
Tourist and business travelers, who have visited these areas and 23 other countries of the southern hemisphere with documented cases of Zika infection, as well as those who visited Asian countries where the first cases occurred, bring the virus home with them. Men may or may not show overt symptoms; one in five appear to have fever, rash, joint pain, and conjunctivitis — red eye — possibly muscle pain and headache.
Women, unless, they are pregnant, usually follow a similar course. If pregnant, especially during their first trimester, possibly the second, there is the real possibility of birth defects to their new-born infants — hearing and vision problems as well as microcephaly.
Microcephaly is a relatively rare condition in the US. Some 20,000 to 25,000 infants are born annually with this condition without mosquito intervention. These non-Zika related cases can occur as a consequence of Rubella, (German Measles), chickenpox, drug abuse, alcohol addiction, malnutrition, and exposure to noxious chemicals. Downs syndrome, (Trisomy) has also been implicated, as have other chromosomal disorders.
Fortunately, during the winter mosquitoes are not a concern, and those blood-borne viruses carried by infected individuals will be removed by their immune system in less than two weeks. Therefore, people returning home will not be a danger to their communities. Other than the one or two instances of women infected with the Zika virus via sexual intercourse, Zika transmission is strictly a mosquito borne problem. No mosquitoes, no infections.
Our concern must be directed to spring and summer, when warmer weather allows mosquitoes to breed. We can expect mosquitoes to increase their range and habitats, which also means that those buggers that have remained south of us will become more prevalent: mosquitoes carrying Zika, Dengue fever, Malaria, and yellow fever viruses, which we have not seen since the 1920s and 1930s.
There is, unfortunately, the possibility of a more dreadful scenario: our local home-grown mosquitoes evolving into aggressive Zika transmitters. That would be our worst nightmare.
With plenty of rainy days March, there are sure to be many standing pools of water in buckets, pails, tires, cans, bags, and wrappers, even bird baths; anything that can hold an ounce or more of water. These flying hypodermic syringes require no more than few drops of water in which to lay eggs that will develop into larvae, and shortly thereafter into adult menaces. We need to prevent as much of that as humanly possible, to avoid becoming a blood meal for the flying females. Indeed, it’s the females that want our blood; males don’t bite.
As the end of March and April come into view, we need to become eradicators of mosquito eggs and larvae. Allowing them to become adults simply puts us all at risk. Ergo, vigilance must be our watchword. See standing water, dump it!
As for ourselves, in addition to mosquito repellent, long sleeves are highly recommended. The Aedes aegypti mosquito, which currently exists in our southern states, but knows which way north is, bites during daylight hours. Its cousin, the Asian Tiger mosquito, Aedes albopictus, arrived here in the 1980s and has taken up residence along the eastern seaboard. If this normally aggressive mosquito evolves into an efficient transmitter of the Zika virus, the eastern states could be swamped with Zika infections and its complications, such as Guillain-Barre syndrome which can induce paralysis. She too prefers human blood and bites during the day.
So cover up. No need to provide them the luxury of our skin. To beat these pests, we need effective mosquito control. For us, it’s a two-pronged approach: no standing water, and mosquito repellent and proper clothing.
Zika belongs to the Flavivirus family that includes yellow fever, Dengue Fever, Chikungunya, West Nile, and several other nasties. Birds of a feather, so to speak, which means there is no blood test specifically for the Zika virus. Zika’s presence in a blood sample is presumed when there is a positive IgM (immunoglobulin) antibody result, as these family members all yield substantial serological cross-reactivity. Is there any wonder uncertainty prevails?
Currently there appears to be less than 10 percent of women in Brazil with a microcephalic infant with a positive blood test. Of course this low number could be due to lack of widespread testing, or we could be seeing virus and non-virus causes of microcephaly at work here. Given the highly restrictive abortion regulations in Latin American countries, many women may be trying to obtain abortions during this chaotic period.
To the question, what about protective vaccines, all that can be said at this time is that there aren’t any for Zika, Dengue, or Malaria. Yellow Fever, yes, but until we see the first cases, that need not be on our agendas.
A number of pharmaceutical companies and university research labs are racing to develop a preventive Zika vaccine, but no one expects any to be available for at least 18 to 24 months, if then.
As for bringing back DDT, an effective mosquitocide, that’s problematic, as the public remains in thrall of Rachel Carson’s “Silent Spring.” However, if local mosquitoes become aggressive carriers of the Zika virus, DDT could well be reconsidered.
Interestingly enough, a dark-horse may be in the wings. Oxitech, originally a British company, now owned by Intrexon, an American biotech firm, has been developing a genetically modified Aedes mosquito. These critters contain a lethal gene that is passed from adult to their eggs and larvae that simply kills them. Which means no females flying about, seeking to sink their fangs into our skins. In tests in Brazil with this lethal gene, mosquito populations have been reduced by 80 percent. A lovely, and encouraging number. Unfortunately, that too, is at best, a year away.
With these malevolent mosquitoes and their equally pernicious passengers, the viruses, we do not have the luxury of doing nothing until a vaccine or other preventive comes on line. We need to protect ourselves, and that means nearby communities must join in this effort as these winged creatures know no boundaries. Mosquito eradication remains our optimum protection. It’s up to all of us to protect one another. But mosquitoes must go!
Melvin Bernarde Ph.D, a Princeton-based author and retired microbiologist/epidemiologist, taught a course in public health at Rutgers and is the author of “Our Precarious Habitat: It’s in Your Hands,” among other books.