Public health importance: Mosquitoes are flying insects of the insect order Diptera and family Culicidae. Their public health importance arises from the habit of female mosquitoes sucking human blood to collect iron and proteins before egg-laying. While feeding on people for blood, female mosquitoes spread diseases such as dengue, filariasis, malaria, yellow fever, and Zika fever.
Feeding and disease transmission: While male mosquitoes feed exclusively on plants, female mosquitoes suck plant juices and nectar and depend on the human blood they need before laying their eggs. Malarial transmission happens by the movement of the causal parasite from the gut of a female Anopheles mosquito when she is feeding on a human host. Likewise, dengue and yellow fever viruses enter a female Aedes mosquito when it feeds on a person with either of those infections. The infectious viruses move into another host through mosquito saliva when the carrier feeds on a healthy individual.
Mosquito life cycle: After female mosquitoes lay their eggs in water, their larvae emerge from the eggs. As mosquito larvae move in jerky movements that resemble wriggling, they go by the name ‘wrigglers.’ Wrigglers feed on organic matter in water, including aquatic plants, and sometimes cannibalistically consume other mosquito larvae. The third stage of mosquitoes is the pupae or tumblers, which are not stationary and swim in the water. Mosquito larvae and pupae respire by coming to the water surface to breathe oxygen in the air. The male and female adult mosquitoes emerge from pupae and mate soon after to continue the insect’s reproductive life cycle.
Why do people attract mosquitoes: People attract mosquitoes through sweat odors, respiring carbon dioxide out, octenol, lactic acid, body heat, and by moving around.
Mosquito genera: The three mosquito genera: Aedes, Anopheles, and Culex, are most important ones which impact human health.
Anopheles mosquitoes have spots on their wings and prefer water having aquatic plants to lay their eggs. They rest at an angle to the water surface with their body parts in a straight line. Anopheles mosquitoes spread encephalitis, filariasis, and malaria.
Aedes mosquitoes have white markings on their black thorax and hold their bodies parallel to the surface when resting. Though Aedes mosquitoes lay eggs in rainwater or marshland, they also prefer domestic environments such as empty vessels and containers, flower vases, drain trays below potted plants, water coolers, and tires to lay their eggs. Aedes mosquitoes spread dengue, encephalitis, yellow fever, and Zika fever.
A Culex mosquito rests on a surface by keeping its body parallel to the surface. Female Culex mosquitoes prefer fresh or impure water to lay their eggs and spread encephalitis and filariasis.
Integrated mosquito management: The key strategy in mosquito management is reducing their reproduction by denying them water for laying eggs. Larviciding is applying pesticides in water having mosquito larvae to kill them. Larvirores such as fishes are a popular choice to feed on mosquito larvae. Though natural predators such as birds, bats, dragonflies, and frogs eat mosquito larvae, such predation is not enough to control mosquito populations.
While pest management professionals (PMPs) use larvicidal pesticides to control mosquito larvae, forming oil films on water surfaces prevents breathing by mosquito larvae and kills them. Indoor and outdoor fogging, either cold or thermal fogging with synthetic pyrethroid pesticides, controls adult mosquitoes. PMPs apply synthetic pyrethroids on walls and other indoor surfaces as an indoor residual spray (IRS) for long-lasting protection against mosquitoes resting on such treated surfaces.
All mosquito management strategies rely on surveillance to know the larval and adult types and populations.
Steps people can take for personal protection from mosquitoes:
Use of long-sleeved clothing, covering ankles with footwear,
using mosquito repellents in the air or on exposed body parts,
screening windows and doors,
limiting movement during dusk and dawn for minimizing attraction to mosquitoes, and
use of mosquito treated bed nets are common.
Mosquito traps: These monitoring tools help in attracting adults and rely on light and odor. While the New Jersey Light trap attracts multiple mosquito species through light, the CDC light traps use light and carbon dioxide to attract and trap mosquitoes.
Gravitraps: Since the past three decades, traps that attract, kill, or limit mosquitoes have emerged as an effective Integrated Mosquito Management tool. Early gravitraps in the United States used stagnant water in organic matter like grass or hay to mimic stagnant natural water to attract mosquitoes. In addition, the early gravitraps used battery-run fans to push mosquitoes into a collection chamber.
Though gravitraps do not control mosquitoes, they effectively minimize pesticide use to curb mosquito populations.
Some gravitraps depend on pesticides to kill mosquitoes, whereas others like the AedesX Smart Gravitrap only kill the larvae and prevent an increase in the mosquito population. We at GPA are confident that gravitraps will increasingly become an important component of Integrated Mosquito Management.
Gravitraps are no longer just surveillance tools to monitor mosquito presence and population, but like in the AedesX Smart Gravitraps, an important smart technology tool for control of Aedes mosquitoes.
What are gravitraps?
These are traps whose design attracts and traps female mosquitoes to lay their eggs. The prefix ‘gravi’ in gravitrap stands for gravid or egg carrying or pregnant female mosquito.
What is an ovitrap?
Ovitraps, similar to gravitraps, have a design that encourages female mosquitoes to oviposition or lay eggs in such traps.
What are lethal ovitraps?
Lethal ovitraps attract, trap, and kill female adult mosquitoes using pesticides and prevent reproduction as they stop egg-laying by a female mosquito. The two types of lethal ovitraps include larvidical or those that kill only larvae and adulticidal or those that kill both adults and larvae that emerge from eggs that the female adults laid in the trap.
Which mosquito species do ovitraps attract?
While the gravitraps from the United States attracted Culex tarsalis or Culex pipiens, Ovitraps like AedesX are now available. They are suitable for container breeding mosquitoes like Aedes aegypti or Aedes albopictus. The BG-Sentinel trap from the United States attracts Aedes aegypti or Aedes albopictus by using human scent, octenol, or carbon dioxide and collects them live by a fan.
Which countries use gravitraps in mosquito management?
Starting with the United States, where the country’s military developed and deployed a gravitrap, many countries have successfully adapted gravitraps. While Singapore’s National Environmental Agency (NEA) uses them effectively, others such as Australia, the Philippines, Brazil, and Thailand have also benefitted from gravitrap use. Peru and Bangladesh have also studied gravitrap technology to overcome mosquitoes.