Mosquito feeding on blood from an ʻApapane
Mosquitoes are a group of small fly-like insects that have a slender segmented body, a pair of wings, three pairs of long hair-like legs, feathery antennae, and elongated mouthparts.
Typically, both male and female mosquitoes feed on nectar and plant juices. In many species however, the female needs to obtain nutrients from a blood meal before it can produce eggs. As a result, the mouthparts of these females are adapted for piercing the skin of animal hosts and sucking their blood. During this process, mosquitoes can inject and/or ingest disease-causing organisms with their bite and are thus a vector for the transmission of diseases such as malaria, yellow fever, Chikungunya, West Nile virus, dengue fever, Zika virus and others.
The above mentioned diseases are transmitted between humans, but mosquitoes are also responsible for transmitting pathogens that can infect birds. Diseases like avian malaria and avian poxvirus can cause deformities and death in birds that have not developed any defense against them.
Culex Quinquefasciatus
Culex Quinquefasciatus–
Southern House Mosquito
Introduced 1826
Culex Quinquefasciatus can carry pathogens like West Nile Virus that can infect HUMANS. This species is also known to carry a blood-borne parasite called Plasmodium relictum. This pathogen is particularly dangerous for Kauaʻi’s forest birds because it causes avian malaria. It is transmitted from infected birds to healthy birds by Culex Quinquefasciatus mosquitoes under suitably (warm) temperatures. Kauaʻi’s forest birds are particularly susceptible to this disease because they evolved in the absence of the pathogen and have developed little or no resistance. In fact, just one bite from an infected mosquito can kill an ʻIʻiwi. Since the introduction of mosquitos to Hawaiʻi, there has been an extreme decline in forest bird populations.
Aedes aegypti
Aedes aegypti
Yellow Fever Mosquito
Introduced 1892
Aedes aegypti is an important vector for many disease causing viruses including the Dengue Fever virus, Chikungunya, Zika virus, and Yellow Fever viruses. The mosquito can be recognized by the white markings on its legs and thorax. This mosquito originated in Africa but is now found in many tropical, subtropical, and temperate regions throughout the world.
Aedes aegypti mosquitoes most commonly feed at dusk and dawn and in shady areas, but they can bite and spread infection all year long at any time of day. Only the female bites for blood, which is needs to mature her eggs. To find a host, these mosquitoes rely on chemical compounds emitted by mammals such as ammonia and carbon dioxide.
Aedes albopictus
Aedes albopictus
Asian Tiger Mosquito
Introduced 1900
Aedes albopictus is native to the tropical and subtropical regions of Southeast Asia, but has found its way to many countries via the transportation of goods and international travel. This mosquito is characterized by the white stripes on its abdomen that give it the appearance of a tiger, thus the common name, “Asian Tiger Mosquito”. Aedes albopictus has become a pest because it flies and bites not only at dusk and dawn, but also in the daytime and it is known to associate with humans. It is of particular concern because it is an important vector for many viral pathogens, including the yellow fever virus, dengue fever, and Chikungunya fever and is also capable of hosting the Zika Virus.
Aedes japonicus
Aedes japonicus
Aedes japonicus is originally from Japan but is now found in China, South Korea, Russia Taiwan, France, Spain, Belgium and the contiguous lower 48 United States. This mosquito is spreading and has recently found its way to Hawaiʻi. Adult mosquitoes live in forested areas and are day biters, but are apparently reluctant to bite humans. In the laboratory, they feed on chicks and mice but not on reptiles or amphibians. Larvae occur in a wide variety of natural and artificial water retainers especially those found in shaded places with water that is rich in organic matter.
“Without question, the one factor that prevented widespread and rapid extinction of virtually all of Hawaii’s native honeycreepers after the introduction of avian malaria was the presence of high-altitude disease refuges on Kauai, Maui and Hawaii,”
Dr. Carter Atkinson, a U.S. Geological Survey (USGS) microbiologist based at the USGS Pacific Islands Ecosystems Research Center in Hawaii.
Before the introduction of the mosquito, Kauaʻi’s forest birds could be found from the mountains to the sea.
Currently, many forest birds are dying from mosquito born illness. Diversity is declining, and the birds are forced to retreat to the remote regions of the Alaka’i.
As warmer temperatures move into the upper elevations, the mosquitos move into the forested regions now occupied by the birds. The birds most susceptible to mosquito born diseases disappear, and only the most resistant will survive.
Mosquito Abatement
Current mosquito control methods are inadequate for the control of invasive mosquitoes and the diseases they carry. Current methods are not efficient or effective at larger scales, nor are they cost effective, or practical and they present many ecological and public health challenges. A range of control techniques are currently being evaluated in order to find a way to protect native Hawaiian birds and ecosystems. This requires the cooperation of many different partners and agencies. It also requires a better understanding of the population dynamics of mosquitos in remote forested regions. KFBRP must conduct frequent and rigorous stream surveys in order to better understand where and mosquitos are found and what species they are. To learn more about how these stream surveys work, please refer to this video on our Youtube Channel.
With climate change predictions, there is an urgency now to work with partners to find solutions that work for people, native forest birds, and Hawaii’s native ecosystems as a whole. Technologies have only recently been developed where control could be addressed at larger scales. These technologies include the use of Wolbachia, a naturally occurring bacteria that could be used as mosquito birth control. Wolbachia have been used successfully in other parts of the world as illustrated by this video. Please refer to the video below to see how Wolbachia may work to control mosquitos in Hawaiʻi.