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Abstract & Introduction

Background

Materials & Methods

Results & Discussion

References

Appendices

MATERIALS

The CDC Miniature Light Traps used in this study are portable sampling devices for the collection of mosquitoes and sand flies. Some traps came equipped with photocells and operated only after sundown; others operated continuously and had to be manually turned on and off. Both styles required the use of dry ice for producing a CO₂ mosquito attractant. The dry ice was made at IUS or purchased locally and placed in perforated Styrofoam containers or in perforated plastic thermos jugs.

The CDC Gravid Trap was specifically designed for the selective capture of gravid Culex mosquitoes. An oviposition attractant was prepared using 1 oz. of dried brewer’s yeast and lactalbumin powder, 1 lb. of hay and 30 gallons of tap water. The solution was placed into a fifty-gallon closed container and allowed to infuse and incubate for five days. A one-half gallon portion of oviposition media was poured into the pan placed below the trap. Females were attracted to the media’s odor, landed on it, and were then swept upward into the net (22).

Floyd, Clark and Harrison County Health Departments provided CDC Miniature Light Traps and CDC Gravid Traps, manufactured by the John W. Hock Company. Figures 11 and 12 are photographs of these traps.

Indiana University SE supplied laboratory space, dry ice, microscopes, supplies and keys for identification of the mosquitoes. IUS biologists also worked to organize a much needed color reference key to the species. This time-consuming task greatly increased our accuracy and ability in identifying each specimen. Finally, Ms. August Nelson received mosquito identification training at a state meeting.

The CDC Miniature Light Traps and Gravid traps were used in Clark, Floyd and Harrison Counties. Protocols for proper use and assembly of these traps were provided with the traps. Briefly, the CDC Miniature Light Trap was assembled according to procedure and then was suspended from a tree limb or other stationary object. The CDC Gravid Trap was placed on the ground near vegetation or standing water in accordance with the manufacturer’s recommendations.

Traps were dispersed at southern Indiana locations chosen by the Floyd, Clark and Harrison County Health Departments and/or Ms. August Nelson. At an unsecured location in Clark County, a location chosen by the staff of the Clark County Health Department, three CDC light traps and 2 Gravid Traps were lost to theft. In some cases, Dr. Baker and students surveyed the area selecting locations for the traps and obtaining the property owner’s permission to place a trap at that location. Other IUS professors, staff employees and students provided locations for mosquito trapping.

Traps were assembled near a suitable collecting site at dusk and allowed to operate continuously. The traps remained in place for a total of four trap nights. The following morning nets were first tied off and then removed from trap assembly. The samples were then transported to Indiana University Southeast where they were placed in the freezer in Life Sciences Building Room #170. The frozen samples were removed from the net and placed in plastic bags or vials for identification.

The frozen mosquito samples were identified to species level using dissecting microscopes, available keys and equipment (23). Ms. August Nelson performed this identification. The identified frozen mosquitoes were placed in labeled bags and were shipped frozen to Indianapolis where the Indiana State Department of Health used PCR Amplification to determine presence of West Nile Virus. Dr. Michael Sinsko, Head Entomologist for the ISDH, reported back only positive WNV results. A large number of the collected mosquitoes were reserved at the IUS campus where Ms. August Nelson performed the VecTest to detect the presence of West Nile Virus.