Nearly everyone has experienced a mosquito bite, the raised bump, the unbearable itching. The story of mosquitoes and man is a complex tale of adaptation, co-existence and far too often, a deadly illness.
The United States, and upstate New York, are very familiar with both mosquitoes and the illnesses they may carry. The ease with which the world interconnects at this time is bringing some strangers to America, new breeds of mosquito and new illnesses.
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Not all mosquitoes bite humans. Some bite both animals and humans. Some only bite humans. All biting mosquitoes have one thing in common, they’re female. The blood they draw when they bite allows them to reproduce. The illnesses, viral, bacterial and parasitic, that they ingest from sick people and carry to other people, are just incidentals to their main purpose. They want to make babies and they need our blood to do it.
WEST NILE VIRUS
Rochester and Upstate New York residents are familiar with the West Nile virus. It arrived in the United States about 1999, and was first discovered in New York City. While most people infected with the virus show no symptoms, those with symptoms suffer a flu-like illness for days or weeks. In less than one percent of those infected, life threatening forms of West Nile called West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis can develop.
West Nile is spread by various members of the Culex family of mosquitoes with C. pipiens being the primary carrier in New York. It is also called the Northern House Mosquito.
C. pipiens loves the filthy water around people. It breeds in storm drains and sewers, even raw sewage and at sewage treatment plants. It feeds on birds, some mammals and on humans.
YELLOW FEVER
New York has not seen a local outbreak of yellow fever since about 1870. Before then, the illness was a regular visitor to New York City, Albany and other parts of the state.
Aedes aegypti is the usual mosquito carrier of this illness. Currently it is found much farther south than New York, though its range varies with the weather.
A. aegypti is very adapted to living around humans. It has regulated its wing speed to reduce the buzz or hum that humans identify with mosquitoes. It is a day feeder, choosing the early morning or late evening to feed. During the heat of the day these mosquitoes seek out dark hiding places where there is little air circulation, like closets or under tables. Most bites from A. aegypti are to the lower leg.
A. aegypti is the opposite of the Culex mosquitoes when it comes to breeding sites. It seeks clean water, rain gutters, clear pools and containers that have collected rain.
MALARIA
Malaria may be one of the earliest illnesses to be described. It is a deadly illness, killing about a million people worldwide every year. It was considered eliminated in the United States by 1951.
In New York, the malarial risk was along the waterways, New York City, up the Hudson River to Albany, along the Mohawk River west, the Lake Ontario and Lake Erie shorelines.
Malaria is a parasite carried and transmitted to humans by mosquitoes in the genus Anopheles. A.quadrimaculatus is the variety common to the New York area.
Despite the eradication of malaria in the United States, cases are discovered every year. Most are acquired by travelers in regions of the world where malaria is prevalent. There are occasional outbreaks, such as this one in New Jersey in 1991, that appear to be native. It is almost certain, however, that the initial host was a traveler who did not know they were sick and was bitten by mosquitoes. This is a common source of outbreaks of mosquito borne illnesses not native to the United States.
A. quadrimaculatus inhabits the eastern United States, east of the Mississippi. They prefer freshwater pods, steams and lakes with vegetation. The mosquito prefers to take blood from animals. They are night feeders.
DENGUE FEVER
Key West, Florida. The last outbreak of this illness native to the United States was in 1945, so its reemergence in 2009 was startling.
There have been dengue fever cases and outbreaks traced to travelers, including cases in Florida at this time. One traces to Puerto Rico, another to Haiti, both areas where dengue is endemic.
Dengue is carries by A. aegypti. This should mean that the outbreak can only move as far north as this mosquito can survive, perhaps into the Carolinas. However, a recent illegal immigrant to the United States may change that assumption.
A. albopictus, the Asian Tiger mosquito, was accidentally brought in to the United States in the 1980’s. It is known to spread dengue fever as well as eastern equine encephalomyelitis and the Cache Valley virus. It is also reported to be able to carry West Nile.
The Aedes genera of mosquitoes are highly adapted to living near humans. they have also demonstrated a high degree of adaptation to changing habitat. Their eggs may survive for several months in a dried out area and revive when water returns to the area.
In an e-mail to me, Dr. Laura Harrington, Associate Professor, Department of Entomology at Cornell University, talked about the Asian Tiger mosquito, A. albopictus. She has found these mosquitoes in New York and New York City but they are not yet able to survive year round. This mosquito has the potential to be a vector for both existing disease and newly imported illnesses such as dengue fever.