The facts on mosquito-borne diseases

By Bill Smith

Bill Smith Contributing columnist

I know I have written several articles about mosquitoes and the Zika virus, but questions persist. This has been emphasized recently with the news that five people stationed at Ft. Bragg have been infected. As they were travel-related — that is it was acquired elsewhere and brought back to N.C. — the risk is lessened.

Generally there are three species of mosquitoes that have prominent roles in transmitting the viruses. First, the culex pipiens, oftentimes called the house mosquito, is the most widely spread mosquito in the world. In our part of the world it is responsible for the spread of eastern equine encephalitis, West Nile virus and other similar diseases. It typically enters houses through gaps in the windows and such. It is not out during the day normally. Its range from the breeding ground is about a mile. It does not play any part in the spread of the Zika virus.

A newer visitor to our community is the aedes albopictus. This is referred to as the Asia Tiger mosquito because of the stripes on the body and appendages. It came to America from China, probably within tires that arrived in Houston, Texas; so much for our friendly trade agreement. It now ranges as far north as New York and is prominent here.

It is the main carrier for the Chikungunya virus, which we worried about at one time until Ebola and Zika appeared. It is a day feeder and is the home-body of the group, probably traveling no more than 300 feet from where it was bred. It will lay eggs in an ounce of water so things like gutters can harbor them. Night spraying will not reduce this population and aerial spraying has a very limited effect as they will be near the ground or under leaves. In fact, aerial spraying kills a lot of other insects, notably bees that are out in the daytime, so it has major drawbacks. To date, this mosquito has not transmitted Zika.

The aedes aegypti is the mosquito of choice for the Zika virus. It came from Africa, possibly riding over with one of the storms that start from there. One of our recent concerns was that the hurricane that came through Florida up to here might carry their mosquitos to us. Fortunately, the winds were not high and it does not appear to have occurred. This mosquito looks somewhat like the Asia Tiger mosquito with stripes, but they are not all over the insect. This breed has been limited to Florida and the gulf coast states. In N.C., 17 areas were surveyed by three universities — metropolitan sites and places with a robust vector control program — and they have not found this breed to be present. Everyone with Zika in N.C. acquired it elsewhere and brought it back. The concern is if the disease can be spread eventually by albopictus because it is so similar to aegypti.

I saw an interesting article about purple martins. Their effect on the mosquito population is tiny as they fly much too high to capture mosquitoes. But what the birds do get a lot of are dragon flies, which is a good predator of mosquitoes. So having purple martins may be counter-productive to keeping the mosquito population down — but if you own them just to watch them fly, enjoy.

Bill Smith Contributing columnist Smith Contributing columnist

By Bill Smith

Bill Smith is the director of the Robeson County Health Department.

Bill Smith is the director of the Robeson County Health Department.

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