Mosquitoes kill more than one million people each year with the deadly diseases they transmit. These diseases include malaria, filariasis, dengue fever, yellow fever and viruses that can cause encephalitis, or swelling of the brain, such as Eastern Equine Encephalitis virus (EEE) and West Nile virus (WNV). Mosquitoes can also vector (transmit) dog heartworm. It is important to note that not all mosquitoes carry diseases. Each of the diseases is mainly transmitted by only a few species of mosquito. Malaria is a single-celled parasite (Plasmodium spp.) that is transmitted by the bite of an infected Anopheles mosquito. An infected person feels tired, has muscle pain, headaches and loss of appetite, much like the onset of flu symptoms. This is followed by chills and high fever which usually reoccur every few days. Lab tests are required to confirm malaria infection. Yellow fever, (so named because the infected person turns yellow from jaundice) is caused by a virus that is carried by an infected mosquito. Encephalitis is difficult to determine because laboratory confirmation is required, a costly and time-consuming procedure. Mosquito control surveillance programs gather data from wild birds and sentinel chicken flocks to determine the presence of encephalitis antibodies. Prevention and control of encephalitis has historically been addressed by local mosquito control programs.
Dog heartworm is caused by juvenile worms (called microfilariae) leaving the mosquito's proboscis and being deposited on the skin of a dog while the mosquito is taking a blood meal. These microfilariae find the puncture wound made by the mosquito and crawl into the dog's bloodstream. Heartworm is a serious problem which can lead to death for dogs. However, veterinarians can prescribe medication to prevent heartworm.