Mosquitoes are major contributors of several diseases throughout the world. Mosquitoes can pass along these diseases to humans by biting them. Only female mosquitoes bite to nourish their eggs and only certain species of mosquitoes carry diseases. The best defense is to become educated about these diseases and find ways to control the mosquito population.
Zika Virus (ZIKV)
In 2016, Zika virus began commanding worldwide attention because of an alarming connection between the virus and microcephaly - a birth defect that results in babies being born with abnormally small heads. The World Health Organization declared a global public health emergency on February 1, and on April 13 the Centers for Disease Control and Prevention confirmed that the evidence was conclusive - the Zika virus causes a rare birth defect and other severe fetal abnormalities.
Transmitted by the aggressive daytime biting Aedes aegypti mosquito, Zika has now spread to 40 countries. There have also been several reported cases of transmission of the virus through sexual intercourse. World Health Organization Director-General Dr. Margaret Chan issued a statement to the effect: "reports and investigations in several countries strongly suggest that sexual transmission of the virus is more common than previously assumed."
Symptoms of the virus include a slight fever, rash, conjunctivitis, headaches, joint and muscle pain. Symptoms begin to show between 3 and 12 days however, the majority of those infected (80%) show no symptoms and don't even know they have the virus.
There is no vaccine or cure for the Zika virus, and the treatment plan for those infected is to get plenty of rest, drink fluids to stave off dehydration, and take pain and fever medications.
Dengue fever is found mostly in Asia, Africa and the Caribbean. However, it has made its way into the United States. In the summer of 2001 four people on the island of Maui in Hawaii contracted the disease. From 1977 to 1994, there have been 2,248 suspected cases of imported dengue fever reported in the United States.
The Aedes aegypti mosquito, which primarily feeds during the day, is a carrier of the Dengue fever virus. Symptoms of the disease begin four to seven days after being bit and include fever, painful headaches, eye, joint and muscle pain and a rash on the arms or legs. The disease is rarely fatal but occasionally progresses to dengue hemorrhagic fever a more serious illness with abnormal bleeding and very low blood pressure.
Chikungunya Fever (CHIKV)
Chikungunya is a viral illness spread human-to-human through the bite of a mosquito. The primary vector for chikungunya is the Aedes aegypti or yellow fever mosquito, although the Asian tiger mosquito is also a competent vector for the spread of Chikungunya.
Chikungunya was first discovered in Tanzania in 1952, but has since spread beyond Africa to nearly 40 countries in Asia, Africa, Europe and also in the Americas. The name ‘chikungunya’ derives from a word in the Kimakonde language, meaning "to become contorted" and describes the stooped appearance of sufferers with joint pain.
The incubation period is usually 3-7 days and symptoms can include sudden fever, joint pain with or without swelling, chills, headache, nausea, vomiting, lower back pain, and a rash. The symptoms are similar to those of Dengue fever, but unlike some types of Dengue, people who have Chikungunya do not experience hemorrhage (bleeding) or go into shock. There is no vaccine for chikungunya and no cure. Management of the disease includes rest, fluids and medications to relieve the symptoms of fever and pain.
Probably one of the most widespread diseases that mosquitoes can carry is Malaria. According to the World Health Organization, malaria infects 300 to 500 million people every year in Africa, India, Southeast Asia, the Middle East, Oceania, and Central and South America. Malaria has been around for thousands of years. The symptoms of malaria were described in ancient Chinese medical writings in 2700 BC. Malaria is etched in history as the construction of the Panama Canal was nearly halted because of it. In 1906, there were more than 26,000 employees working on the canal of these, more than 21,000 were hospitalized for malaria at some time.
Malaria is transmitted by the Anopheles mosquito. These mosquitoes primarily bite during the nighttime hours. Once infected, the symptoms include anemia, fever, chills, nausea, and flu-like illness and in severe cases coma and death.
Malaria kills between one and three million people worldwide each year. Since there is no vaccination for the disease and the Plasmodium parasite that causes malaria has become increasingly drug resistant scientists are beginning to look at a new way to combat the disease. Researchers are currently looking for a way to create a genetically altered Anopheles mosquito that would be resistant to the Plasmodium parasite.
West Nile Virus (WNV)
Probably one of the diseases that is of most concern for those living in the United States is the West Nile virus. The West Nile virus has actually been around for decades. The disease was first recognized in a woman in the West Nile District of Uganda in 1937, thus the origin of its name. There have been millions of cases of the disease reported from the Western Mediterranean and Africa through the Middle East. In 1996 the West Nile virus spread to Europe and in 1999 was found in New York City. Out of 62 confirmed cases in New York, seven deaths were reported. So far, West Nile virus has spread to 41 states and Washington D.C. One of the most common mosquitoes, the Culex species, is known to carry the West Nile virus. A person bitten by an infected Culex mosquito can contract the West Nile virus. The virus itself causes severe human meningitis or encephalitis, which is inflammation of the spinal cord and brain.
Eastern Equine Encephalitis (EEEV)
Eastern equine encephalitis is as its name implies, primarily caused by a virus that infects horses. This mosquito-borne viral disease also infects humans and some species of birds. The virus received its name after a major outbreak occurred in horses in the coastal areas of Delaware, Maryland, New Jersey, and Virginia in 1933. Additional outbreaks occurred in Virginia and North Carolina in 1934 and 1935. There have been approximately 220 confirmed human cases of Eastern equine encephalitis (EEEV) in the United States between 1964 and 2004. States with the largest number of cases are Florida, Georgia, Massachusetts and New Jersey.
Mosquitoes were first determined to be potential carriers of EEEV in 1934. Various mosquito species of Aedes andCulex can transmit the virus to humans. EEEV transmission is most common in and around freshwater swamps in the Atlantic and Gulf Coast states and the Great Lakes region. Cases of human infection are less likely because the primary transmission occurs in swampy areas where the mosquitoes live, but most humans don’t. Once infected with the virus, many humans have no apparent symptoms. However, some develop symptoms ranging from mild flu-like to inflammation of the brain, coma and death.
Japanese Encephalitis Virus (JEV)
The Japanese encephalitis virus is a mosquito-borne virus, which can be potentially fatal to humans. The virus has spread throughout eastern Asia, including India, Japan, China and Southeast Asia. The virus has also cropped up in Australia in 1995.
The virus is transmitted through the Culex species of mosquito. Culex mosquitoes become infected by feeding on domestic pigs and wild birds infected with the Japanese encephalitis virus. Infected mosquitoes then transmit the Japanese encephalitis virus to humans and animals during the feeding process. Once infected a person might experience a mild infection with a fever with headache. More severe infection is marked by quick onset, headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, occasional convulsions and spastic paralysis.
La Crosse Encephalitis (LACV)
La Crosse encephalitis virus is transmitted by the Aedes species of mosquito. It occurs in the Appalachian and Midwestern regions of the United States. The virus was first discovered in La Crosse, Wisconsin in 1963. Since then the virus has been detected in several Midwestern and Mid-Atlantic states. There are usually 75 cases of La Crosse encephalitis reported to the Centers for Disease Control every year. Most cases occur in Minnesota, Wisconsin, Iowa, Illinois, Indiana and Ohio. Recently more cases have been reported in West Virginia, Virginia, North Carolina, Alabama and Mississippi.
Symptoms of the disease include nausea, headache, and vomiting. In more serious cases the symptoms can be seizures, coma, paralysis and permanent brain damage.
St. Louis Encephalitis (SLEV)
The St. Louis encephalitis virus is related to the Japanese encephalitis virus. This virus mostly affects the United States and occasional cases in Canada and Mexico. The origin of the virus began in 1933 when an encephalitis epidemic broke out in vicinity of St. Louis, Missouri. More than 1,000 cases were reported.
The virus is transmitted via the Culex mosquitoes that become infected by feeding on birds infected with the virus. Infected mosquitoes then transmit the virus to humans.
Symptoms of the virus include fever and headache and in more severe cases can cause headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions and spastic paralysis.
Western Equine Encephalitis (WEEV)
Western Equine Encephalitis is relatively uncommon. There have been less than 700 confirmed cases of the virus in the United States since 1964. The virus is seen primarily in states west of the Mississippi River and in some countries in South America.
The Culex mosquito transmits the virus. Once infected symptoms range from mild flu-like illness to encephalitis, coma and death.
Rift Valley Fever (RVFD)
Though primarily a virus that affects livestock, humans do contract Rift Valley Fever as well. The disease is usually found in Africa and the Middle East. There have been severe outbreaks of the disease. In Africa between 1977and 1978 several million people were infected and thousands died.
Humans can become infected from the bite of an infected Aedes mosquito. Symptoms are usually mild and include fever, weakness, back pain, dizziness and weight loss. In rare cases it can lead to hemorrhagic fever syndrome or meningoencephalitis (inflammation of the brain).
Yellow fever is primarily found in African and South American countries. The yellow refers to the jaundice symptoms that affect some patients. Humans contract the disease from infected Aedes simpsaloi, Aedes africanus, and Aedes aegypti mosquitoes.
Although it’s not usually found in the United States, yellow fever has made its way here. A ship carrying people infected with the virus arrived in Norfolk, Virginia in 1855. The disease spread quickly eventually killing more than 3,000 people.
There is a vaccination available for yellow fever but as of 2001, the World Health Organization estimates that yellow fever causes 200,000 illnesses and 30,000 deaths in unvaccinated countries.
Another type of mosquito-borne disease that affects our furry, four-legged friends is heartworm disease. Dog heartworm disease can be a life-threatening disease for canines. Dogs and sometimes other animals such as cats, foxes and raccoons are infected with a type of roundworm through the bite of a mosquito carrying the larvae of the worm. Many common types of mosquitoes can carry the heartworm disease and the disease is found throughout the United States.
Once a dog is infected with the roundworm through a mosquito bite, the worms burrow into the skin and eventually end up in the canine’s heart. The cure for heartworm can be risky and expensive. However, it is preventable and there are several medications on the market for dogs.
Preventing Mosquito-Borne Diseases
Of all of the mosquito-borne diseases, the ones that occur within the borders of the United States are West Nile virus, eastern equine encephalitis, La Crosse encephalitis, St. Louis encephalitis and western equine encephalitis. There are no vaccines for these diseases. Most of the other viruses that may have once appeared here are no longer around due to effective vaccinations.
One way to prevent the spread of these diseases is to get rid of the mosquito population. While eradicating all the mosquitoes in the world sounds like a good idea, it will never realistically happen. Therefore, taking protective measures against mosquitoes is the next best solution.