Mosquito Hunting in Liberty County, TX
LIBERTY, September 30, 2016 – By Bryce Langskov (American Conservation Experience, Intern) and Laurie Lomas Gonzales (Trinity River National Wildlife Refuge, Wildlife Biologist)
Mosquitoes are a pesky bunch. Most would not think of them as a beneficial creature, but like all other life forms, they have their place in the complex food web.
We think of mosquitoes as blood-sucking drones, flying around searching out a target with precision. If there are enough of them, they can even run us out of an area. Underwater, many fish, insect larvae, and tadpoles, feed on mosquito larvae. As one female mosquito can produce 100 eggs at a time, and those eggs hatch within 24-48 hours, one can see how mosquitoes are, in fact, important to an underwater ecosystem. On land and air, many animal species, such as birds, bats, spiders, dragonflies, fish, and frogs, think of adult mosquitoes as a meal on the go. In fact, if mosquitoes were completely removed from the arctic tundra, 50% of the migratory birds which nest in the north would die of starvation, including most species of ducks.
In the lower 48 states, however, mosquitoes can be hazardous to human and animal health. They are known as vectors for disease. In east Texas, several types of encephalitis cause concern in Texas: eastern equine encephalitis (EEE), western equine encephalitis (WEE), and St. Louis encephalitis (SLE). The viruses are normally transmitted among birds, mosquitoes, humans and horses. When the incidence of any encephalitis virus increases in bird populations, it becomes more likely that humans and equines can become involved. Mosquitoes are also responsible for the transmission of Dengue fever, malaria, yellow fever, Zika virus, West Nile virus, and Chikungunya virus to humans and heart-worms to dogs.
Due to the threat of these vector-borne diseases, infections transmitted by the bite of infected mosquitoes, US Fish and Wildlife Service (USFWS) has partnered with Texas Department of State Health Services (TDSHS) to assist in Mosquito-borne Disease Surveillance Program in east Texas. This program is designed to detect equine encephalitis virus, West Nile virus, and Chikungunya virus in mosquito populations.
At Trinity River National Wildlife Refuge (USFWS; Liberty, TX), Bryce Langskov, biotechnician, is assisting TDSHS in collecting live mosquito samples. One would think it would be simple to catch thousands of mosquitoes. Just walk outside. But, mosquitoes can be finicky, as Bryce has pointed out, “it was an arduous process but an interesting project for my internship.” Bryce was in charge of the project. His first step was to find attractants used to bait mosquitoes.
Mosquitoes are attracted to smelly stagnant water for laying eggs. Bryce created bait by using stagnant water steeped with leaves and cow feces, brewed by the sun for days. Surprisingly, that bait proved to be unsuccessful in drawing the mosquitoes to traps. He realized that an alternative method needed to be attempted.
It seems like mosquitoes somehow know when we enter an area or walk outside. It is as is they hear us breathing. Actually, they smell us breathing. They detect carbon dioxide in our breath. The next question, how to supply carbon dioxide to traps overnight? Use dry ice, which is carbon dioxide in a solid form.
“By rigging up some jugs to hold the dry ice, we attracted mosquitoes to the trap. Then when they got close enough to the light, the fans inhaled the small flying varmints into the sack made of fine netting,” explained Bryce, who let out a laugh, “however, little did we know that the amount of mosquitoes being trapped would far exceed our expectations.”
Bryce continued, “After our triumph in gathering the insects in to our traps, we began the extraction process. This process included getting up close and personal, you have to wear leather gloves, as the mosquitoes will attack you through the net. Using a retrieval gun to suck up the mosquitoes and transfer them into containers for transport was difficult. They become very unwilling to cooperate when this process was attempted. After this step, we then packed and shipped the fragile blood-sucking ‘carbon dioxide detectors’ within an insulated box filled with ice packs. This was to insure that they arrived intact to their destination at TDSHS. One question is why we aren’t monitoring for Zika virus. The answer is science is simply not there yet. Tests for detecting Zika virus in mosquitoes don’t exist yet. Zika virus is detected in the human populations. If there is a single or a few cases of non-travel related Zika virus infection, you know the mosquito population may be infected. However, the number of mosquitoes carrying Zika virus may be so low that may still not be detectable even if the tests were available.
Bryce is waiting with baited breath, “we are still awaiting disease results for our mid-September submission from Trinity River National Wildlife Refuge. However, the types of mosquitoes caught numbered at 11 different species!” Most people don’t think about these small insects having so many different classifications, but they truly are remarkable in their variety.
This Mosquito-borne Disease Surveillance Program is conducted in Liberty County, TX, in partnership with Texas Department of State Health Services Region 6/5 south. TDSHS is seeking more sites for mosquito-surveillance in east Texas. If you would like to participate in mosquito surveillance, please contact Bob Garrison at (713) 767-3302. If you have any questions regarding Trinity River National Wildlife Refuge, please call the Refuge Office at (936) 336-9786 or drop by the office at 601 FM 1011, Liberty, TX 77575.