Taking the Bite Out of Mosquitoes


C. Dayton Steelman and Dennis L. Wallette Jr.

Mosquitoes have been cussed, discussed and described in written detail since the first explorers traveled through the area now known as Louisiana. Because of their need for blood from human or animal hosts, mosquitoes have historically caused misery and suffering to Louisiana citizens and visitors alike.

Throughout Louisiana’s history, massive numbers of mosquitoes have thrived along the Gulf Coast from Plaquemines west through Cameron Parish. These parishes include rice production, swamps and bayou areas. Massive outbreaks occurring on seven- to 10-year cycles, and especially after hurricanes, often have resulted in cattle and other domestic animal deaths because of blood loss and suffocation caused by blockage of air passages. The impact of mosquitoes on tourism and their potential as carriers of organisms that cause disease resulted in the establishment of mosquito abatement districts in Jefferson, Orleans, St. Bernard and St. Tammany parishes in the early 1960s.

Because of public concern over the continued impact of mosquitoes on humans, domestic and wild animals, the Louisiana Agricultural Experiment Station created a position for a scientist to do research on mosquito population management in 1965. Research was conducted in cooperation with the Louisiana Mosquito Control Association, which had researchers at New Orleans, Lafayette and Lake Charles, the existing mosquito abatement districts and the U.S. Department of Agriculture (USDA) Mosquito Research Laboratory at Lake Charles.

A significant effort was immediately initiated wherein the mosquito abatement districts provided funding for a laboratory technician at LSU to determine the susceptibility of mosquitoes to the insecticides in use in mosquito control programs. Abatement district personnel collected mosquitoes from their respective parishes and delivered them to LSU where the tests were conducted. The baseline data established in these tests later identified the development of insecticide resistance in mosquitoes to several insecticides that had been in constant use in the various parish programs. This information provided advance warning that resulted in preventing resistance development in the districts by their changing to alternative insecticides.

In 1971, mosquitoes carrying Venezuelan encephalitis crossed the border between Mexico and Texas, killing horses and dogs and threatening the human population. Massive numbers of mosquitoes were in coastal Texas and Louisiana at this time, and this stimulated the U.S. Department of Agriculture to conduct an emergency adult mosquito control program in Texas that included Cameron and Calcasieu parishes in Louisiana. The emergency program involved the aerial application of ultra-low-volume insecticide and effectively controlled adult mosquitoes and protected the horse population for a three-week period until a horse vaccine could be administered. LSU AgCenter scientists worked with USDA’s Animal and Plant Health Inspection Service (APHIS) personnel during this program. No horse or human cases of Venezuelan encephalitis occurred in Louisiana. This mosquito control program provided a large-scale demonstration that proved to the citizens of the coastal parishes that mosquitoes could be controlled effectively.

LSU AgCenter scientists went on to help form mosquito control programs in Cameron, Calcasieu, Jefferson Davis and Vermilion parishes. Later, the LSU AgCenter led the way to initiating mosquito control programs in East Baton Rouge and Ouachita parishes. Since the mid-1970s, many other mosquito control programs have been initiated in other parishes.

Research on mosquitoes at LSU has included the identification of the mosquitoes responsible for transmitting dog heartworm, anaplasmosis and equine infectious anemia (swamp fever), identification of host animals that provide most of the mosquito blood meals and the impact of wildlife habitat management on mosquito production. The mosquito research program at LSU received national and international recognition for its leadership in a consortium of scientists from rice production states that conducted research from 1979 to 1993 on the biology and control of mosquitoes produced in rice fields.

In addition, landmark research that determined the effect of mosquito attacks on cattle production, identifying Brahman-breed resistance to mosquitoes, was conducted at the Rice Research Station in Crowley. The mosquito abatement districts have received helpful information on the integrated management of mosquitoes in many aquatic habitats, impact of insecticides applied for mosquito control on non-target aquatic organisms and mark-release-recapture studies that determined mosquito dispersal. Countless experiments have been conducted to determine the efficacy of many different insecticides, biological agents and habitat manipulation for managing mosquito populations.

(This article appeared in the spring 2001 issue of Louisiana Agriculture.)

6/2/2005 2:16:43 AM
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