Why You Should Worry About Mosquitos

Aedes egypti day biting mosquito

By Lizzie Bennett

In her recent article, Widespread Drug-Resistant Malaria Cases Now Threatening India, Tess discussed increasing resistance to malarial drugs half a world away, and how that can, and very likely will, eventually affect those of us living in the West.

Malaria is just one of a wide variety of diseases that mosquitos can spread and although many of the species concerned are found in the tropics mosquitos can and do hitch rides with travelers returning from these areas. To discuss each disease in detail is beyond the scope of this article, please click on the relevant links to find out more about a particular disease.

West Nile Virus was first reported in the United States in October 1999. You can read about that outbreak here.

Most cases of WNV are not serious and many people have no symptoms or only mild flu-like symptoms, such as headaches, muscle aches and a high temperature (fever).

Serious problems occur in fewer than 1 in 100 people infected with the virus but can include infection of the brain (encephalitis), spinal cord, and tissues surrounding the brain and spinal cord (meningitis), which can be fatal.

Signs of a severe infection can include muscle weakness, disorientation, seizures (fits) and loss of consciousness.

Rift Valley Fever originates, as you may expect, in the Rift Valley region that runs down East Africa from Kenya to South Africa. Primarily it affects cattle and livestock but is zoonotic which means it can and does infect humans as well as animals.

There is concern that RVF could spread to Europe and the United States as since 2000 cases have occurred outside of the African continent. Most human cases have mild symptoms very similar to those of West Nile Virus, but a small number of people will develop lesions in their eyes, meningitis or even hemorrhagic fever where spontaneous bleeding occurs from orifices as per Ebola. The death rate for these patients is 50% on average.

Dengue Fever is a leading cause of illness and death in tropical and sub-tropical regions. Symptoms include:

a high temperature (fever) that can reach as high as 41C (105.8F)
a headache
pain behind the eyes
bone, muscle and joint pain

As many of these diseases, the treatment is prophylactic to relieve the symptoms caused by the virus but treatment will have no effect on the virus itself. In 2013, there was an outbreak of Dengue in the UK with 541 cases reported. The same year saw over 2000 cases in Europe and major outbreaks with case numbers in the thousands in several Central American countries.

Complications that can lead to death include:

Yellow Fever is a nasty disease that causes jaundice, a yellowing of the skin, hence the name. There is a vaccine available for yellow fever, it’s a live vaccine and it takes ten days to work. Some countries will not allow visitors in if they cannot produce a vaccination card.

Six travelers from Europe and North America have died from yellow fever since 1996. None of them were vaccinated.

The symptoms of yellow fever occur in two stages. The initial symptoms develop three to six days after infection and can include:

a high temperature (fever)
a headache
nausea or vomiting
muscle pain, including a backache
loss of appetite

This stage will usually pass after three to four days and most people will make a full recovery.

However, around 15% of people go on to develop more serious problems, including jaundice (yellowing of the skin and whites of the eyes), kidney failure and bleeding from the mouth, nose, eyes or stomach (causing blood in your vomit and stools).

Up to half of those who experience these symptoms will die. (source)

Chikungunya is spreading fast. In the last few hours news articles have started to pop up concerning a major outbreak in Colombia, and meetings are taking place to strengthen the US response to the threat along the US-Mexican border. This outbreak started in the Carribean late last year and has rapidly spread through South America and is marching north at a fast pace.

Infection with chikungunya virus is rarely fatal, but the joint pain seen with chikungunya can often be severe and debilitating. The virus is not spread between people. There is no vaccine and no specific treatment for the infection. Patients recover in about a week, although some people have long-term joint pain. Infection is thought to provide lifelong immunity. (source)

Eastern Equine Encephalitis (EEE) is spread to horses and humans by infected mosquitoes. It is among the most serious of a group of mosquito-borne arboviruses that can affect the central nervous system and cause severe complications and even death. EEE is found in freshwater hardwood swampland in the Atlantic and Gulf Coast states in the eastern part of North America, Central, and South America, and the Caribbean. It has a complex life cycle involving birds and a specific type of mosquitoes including several Culex species and Culiseta melanura.

These mosquitoes feed on infected birds and become carriers of the disease and then feed on humans, horses, and other mammals. EEE cannot be transmitted from humans or other mammals because the viremia presented in the disease is not sufficient to further transmission. Thus, humans and other animals are known as “dead-end hosts.” Symptoms may range from none at all to a mild flu-like illness with fever, headache, and sore throat. More serious infections of the central nervous system lead to a sudden fever and severe headache followed quickly by seizures and coma. About half of these patients die from the disease. Of those who survive, many suffer permanent brain damage and require lifetime institutional care. There is no specific treatment. A vaccine is available for horses, but not humans.

St. Louis Encephalitis (SLE) is transmitted from birds to man and other mammals by infected mosquitoes (mainly some Culex species). SLE is found throughout the United States, but most often along the Gulf of Mexico, especially Florida. Major SLE epidemics occurred in Florida in 1959, 1961, 1962, 1977, and 1990. The elderly and very young are more susceptible than those between 20 and 50.

During the period 1964-1998 [35 years] a total of 4478 confirmed cases of SLE were recorded in the United States Symptoms are similar to those seen in EEE and like EEE, there is no vaccine. Mississippi’s first case of St. Louis Encephalitis since 1994 was confirmed in June 2003. Previously the last outbreak of SLE in Mississippi was in 1975 with over 300 reported cases. It was the first confirmed mosquito-borne virus in the United States in 2003. It turned up in October 2003 in California Riverside County in sentinel chickens. The last [SLE] human case in California occurred in 1997. In Louisiana, in 2003 there was a fatal St Louis Encephalitis case previously listed as a West Nile caused death.

LaCrosse encephalitis (LAC) is much less widespread than EEE or SLE, but approximately 90 cases occur per year occurs in all 13 states east of the Mississippi, particularly in the Appalachian region. It was reported first in 1963 in LaCrosse, Wisconsin and the vector is thought to be a specific type of woodland mosquito (Aedes triseriatus) called the tree-hole mosquito, with small mammals the usual warm-blooded host. Infrequent fatalities occur in children younger than 16. It is not transmissible from human to human. There is no vaccine for LaCrosse encephalitis.

Western Equine Encephalitis (WEE) was first recognized in 1930 in a horse in California. It is found west of the Mississippi including parts of Canada and Mexico. The primary vector is Culex tarsalis and birds are the most important vertebrate hosts with small mammals playing a minor role. Unlike LAC it is nonspecific in humans and since 1964 fewer than 1000 cases have been reported As with EEE a vaccine is available for horses against WEE but not for humans. In Arizona 3 counties have been found with sentinel chicken flocks seroconverting to WEE.(source)

As more and more people travel the chances of these diseases making it to our shores increases. It should be remembered that many species of mosquito, such as those whose name is prefixed by Aedes actually bite during the daytime, not at dawn and dusk as most advice on avoiding bites states. If you are in an area where mosquitos are common the only way to be sure you won’t contract any of these diseases is to avoid getting bitten in the first place. Remember:

Mosquitos are more attracted to dark-colored clothing as heat is retained and they home in on that heat.
Avoid areas where there is stagnant water, and therefore, most likely to be mosquitos as they lay their eggs in water.
Keep your gardens and yards clear of standing water, however, small the volume.
Mosquitos often stay within a few hundred feet of where they hatch. Preventing egg laying near your property reduces numbers drastically.
Find a repellent, natural or chemical based that suits you and the area you are in and apply when you are likely to come into contact with mosquitoes.
Mosquitos fly at under 25ft and are attracted to the carbon dioxide that we breathe out, based on that, see the video below. Cheap, easy and it works.

Personally, having done this I added more sugar and more yeast as my climate is colder and I wanted to be sure I got a good reaction going. I fixed mine at a head height near to where we were sitting. It worked like a charm. If you are indoors, place it near an open window so the smell attracts them as they fly into the house.