To understand how mosquitoes carry and transmit disease, it’s necessary to understand how mosquitoes reproduce. When a female mosquito is ready to produce eggs, she must drink a small bit of blood to help her eggs develop. To get that blood, she’ll bite a mammal, bird, reptile, or amphibian. Some mosquitoes only bite from a single source, such as birds, while others will bite from more than one, such as the mosquito that transmits yellow fever, which bites both humans and monkeys.
When the female mosquito bites, she inserts her proboscis – or feeding tube – into the skin in search of blood. The feeding tube that she uses to drink the blood is very small, so to make it easier for the proboscis to penetrate the skin and to prevent the blood from clotting and blocking the tube, she releases a small amount of anticoagulant enzyme-laced saliva.
The blood that the female mosquito takes into her body may be laden with parasites, viruses or other disease-causing organisms. While in the mosquito, these parasites or viruses will continue to develop and reproduce, and when the mosquito bites her next “victim,” those disease-causing organisms can be transferred along with her saliva.
There are a number of diseases that can be transmitted by the mosquito:
West Nile Virus (also known as West Nile Fever or West Nile Encephalitis) can affect people, horses and birds.
Malaria is transmitted from human to human by the Anopheles mosquito. Malaria is caused by a protozoa that uses the mosquito as a host.
Yellow fever is a virus transmitted from monkey to human or from human to human by mosquitoes.
There are a variety of forms of encephalitis that are transmitted by mosquito, including LaCrosse encephalitis (affects humans), Western Equine Encephalitis (affects humans and horses), Eastern Equine Encephalitis (rare though very serious in humans, severe and usually fatal in horses), Venezuelan Equine Encephalitis, California Encephalitis, Japanese Encephalitis, Australian Encephalitis, and St. Louis Encephalitis (affects humans).
Rift Valley Fever and Dengue Fever can also be transmitted by mosquitoes.
The virus that causes meningitis can be transmitted by mosquito.
Dog heart worms are worms that undergo a stage of development in the blood of dogs. While dog heart worms cannot be transmitted to humans, a similar related parasite that causes human elephantiasis can be transmitted to humans by mosquito.
The best way to protect yourself from getting a mosquito-borne disease is, of course, to avoid being bitten by a mosquito. The following are some ways to avoid mosquito bites:
Use a mosquito repellent. DEET remains the most effective repellent, although newer products containing picaridin are showing success. Look for a product that contains up to 30% DEET for adults; products for children should contain 10% DEET or less, and products containing DEET should not be used on children under 2 months old. Always follow the directions printed on any repellent product you choose.
Limit your exposed skin by wearing pants and long-sleeved shirts when possible.
Avoid being outside during dawn and dusk, when mosquitoes are most active.
Eliminate standing water and other potential havens and breeding locations for mosquitoes, and stay away from them if you can’t eliminate them yourself.