Mosquito season ugly, and far from over

While this mosquito season has been particularly bad, so far she has been kind to us — knock on wood — with regard to mosquito-borne diseases.

By this time last year there were four cases of Eastern Equine Encephalitis in horses, all of which died; three pools of mosquitoes that had tested positive for the West Nile virus; and reported human infections of West Nile virus, one case proving fatal. This year there have been no reported cases of locally transmitted mosquito-borne illness in Collier County.

While we may have dodged the hurricane and mosquito-borne disease bullets so far, residents of Naples still have to take precautions to protect themselves for another two or three months. Historically, the next couple of months are the prime months for the transmission of West Nile virus (WNv) in the Naples area. Because the Collier Mosquito Control District (CMCD) can’t bring mosquito levels to zero, residents need to take precautions to protect themselves from mosquitoes.

Anyone needing to go outdoors should avoid the dusk and dawn hours, if possible, as this is when mosquitoes are most active. When outdoors wear long sleeve shirts, long pants, shoes and socks, all in light colors. And don’t forget the repellent.

The Centers for Disease Control (CDC) still recommends products with DEET or Picaridin as the active ingredient, with DEET getting the nod for being longer lasting than Picaridin. Remember to thoroughly read and understand the label of the repellent you choose before applying it.

Oh yeah, remember to look around your property and empty anything that holds water to prevent home-grown mosquitoes.

While protecting human health is paramount, protecting domestic animals is also important. Horses should be vaccinated against Eastern equine encephalitis and West Nile virus, while dogs should be placed on medicine to prevent dog heartworm, a disease transmitted by several species of local mosquitoes.

A note of caution, however: Before putting a dog on a heartworm prophylactic regimen, have the dog tested for heartworm by a veterinarian. Starting a dog already infected with heartworm on such a regimen can result in the death of the dog.

As for the mosquitoes that normally invade the Naples area in the summer; it has been a normal mosquito season: totally unpredictable. Has this been an exceptionally bad mosquito season? Yes, especially in comparison to the last several years, causing people to think it is the worst season ever in Naples.

So what is making this such a strange year? If you can figure that out, you need to stop by CMCD and let us know.

The “normal” progression of mosquitoes in Naples is for the black salt marsh mosquito to invade first. This mosquito comes to us by way of the mangrove marshes that practically surround Naples. The production of this mosquito is caused by the high tides and/or coastal rains early in the summer. Its population tapers off as larval habitats receive heavier rains that serve to flush out the habitat and mosquito-eating fish become established.

Then, as the rainy season sets in, fresh-water Psorophora mosquitoes take their place. Of the fresh-water mosquitoes, a couple of species of Psorophora, vicious biters all, begin appearing around the district. These mosquitoes are produced when swales, ditches and retention ponds start holding water.

Continuing the progression, Culex mosquitoes appear next, being produced in the same locations as Psorophora when the water becomes filled with rotting organic matter. It is these Culex mosquitoes that are the vector for Saint Louis Encephalitis (SLE) and WNv.

This year the salt marsh mosquitoes appeared pretty much on schedule, were bad for several weeks and then, unexpectedly, they seemed to disappear quite a bit earlier than normal. Then they came back with a vengeance, which was also unexpected. There were salt marsh mosquitoes as far inland as the eastern Estates and Ave Maria, not a normal occurrence.

When the summer rains began to fall more inland, fresh-water mosquitoes began appearing all over the district. However, it wasn’t the normal progression, as Culex mosquitoes also arrived with the rain, not the normal Psorophora.

And they just kept arriving and arriving, to the point that the district had all of its fixed wing aircraft flying simultaneously on three different nights. Then the pilots would have to climb into a helicopter to treat more areas of the district. Only now are there high numbers of Psorophora fresh-water mosquitoes being collected around the district.

With the near continuous production of Culex and Psorophora mosquitoes, and strange weather patterns this year, the CMCD has been very active in the effort to control mosquitoes to prevent the spread of mosquito-borne diseases.

The results so far this year demonstrate the district’s commitment to protecting residents and domestic animals. And that commitment will continue into the foreseeable future, no matter how sneaky our mosquitoes try to be.

Jeff Stivers is director of research for the Collier Mosquito Control District, an agency charged with suppressing mosquito populations in most of Collier county. Phone 436-1000 or visit its Web site: www.cmcd.org.

© 2011 marconews.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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