Diseases

Mosquito Diseases

Mosquito diseases are an important factor in the need to be proactive about getting rid of mosquitoes.

Aside from the irritation and inconvenience of having mosquito bites, there are far more serious reasons for being aggressive about mosquito kill. They are carriers, or vectors, for a number of serious, and sometimes fatal, diseases.

Before modern transportation turned our planet into a global village, many of these diseases were restricted to specific geographic areas. Now, a Western traveler to Laos, for example, can be bitten and infected with Dengue fever, return home with active symptoms and be bitten by a mosquito that can transmit the disease to someone else.

In fact, West Nile virus came to North America from South East Asia because a shipment of used tires arrived in Houston, Texas harboring infected Asian Tiger, aedes egypti, mosquitoes.

From the original Asian Tigers that arrived in the Southern United States, their range has spread and now covers most of the United States. They have also spread to most of the United States from the original Texas stowaways.

To look at the mosquito diseases that are endemic only to one part of the globe is very sort sighted. It fails to take into account that disease risks occurring half way around the globe are risks everywhere because we have become so mobile.

The most important, and prevalent, mosquito borne diseases are these:

ENCEPHALITIS

There are several strains of encephalitis, most classified according to region and mosquito vector. It is not only a risk
to humans, but also to livestock. Equine encephalitis is a major concern for horse
breeders and owners. Learn more about Encephalitis below.
WEST NILE VIRUS

West Nile virus has been around since 1937, when it was first discovered in Africa. With the arrival of the Asian Tiger Mosquito in the United States, it has become a health problem in the Americas as well. While not as deadly as malaria, it is still a very serious mosquito disease. Learn more about West Nile Virus below.

MALARIA

Not a newcomer in the human plague arena, malaria is a serious, and sometimes epidemic disease, especially in tropical countries. It’s wide reaching destructiveness keeps it on the radar screen of the World Health Organization as a significant global concern. Learn more about malaria below.

DENGUE FEVER

Originally restricted to South East Asia, dengue fever is rapidly spreading around the world. It is now becoming a serious health risk in areas where it previously was extremely rare. Learn more about Dengue Fever below.

In terms number of deaths caused by wildlife, world wide, mosquitoes lead the pack. It is no longer an option to ignore ways to reduce their populations. It is a health imperative, especially since many of these mosquito diseases appear to be spreading to areas where they were once rare.

In 2016 Zika is the new “star disease” from mosquito’s, so lets start there…

About Zika Virus and Mosquito’s

In the last several weeks every time the news comes on Zika virus is in the headlines. According to health officials, Zika virus has made it to the United States from several foreign countries and the concern about unborn children and their mothers contracting the disease is on the rise.

Per Health officials, symptoms of the virus include a fever, rash, red eyes, joint pain and may last up to a week. In fact, many people aren’t even aware that they’ve contracted the disease. Typically, one out of five persons who contract the disease via a mosquito bite will become ill. Symptoms will appear within a few days of infection.

However, there are many potential complications of the disease. Zika can cause severe brain damage in unborn children and infants who are affected. This damage includes babies being born with very small heads. Due to this concern, American officials have cautioned pregnant women to avoid travel to approximately 30 countries and their territories to help reduce this risk of contracting the Zika virus.

This travel also includes Puerto Rico where the virus is rampant thanks to mosquito’s. Per the federal Centers for Disease Control and Prevention, avoiding these areas could help to reduce the spread of Zika. According to one study, doctors have also connected the disease to another rare syndrome, Guillain-Barre wherein patients may be paralyzed for several weeks. Further study shows that the condition is typically contracted while abroad, however, there have been incidences of people making it back to the states and suddenly coming down with the virus.

With no medication or vaccine to prevent the virus, travelers are urged to consider their state of health prior to traveling in foreign countries, especially of those travelers are pregnant. The concentration at the moment is more on prevention than on the condition itself while this is a huge concern, the other huge concern is keeping it from happening in our own country. Since the condition is so mild most people aren’t aware that they’ve even come down with it. Its typical duration is no longer than the average cold and it displays symptoms days to weeks after the person has contracted the condition. Since most people aren’t sick enough to even consider going to the doctor, many cases may go un-diagnosed and thus, people aren’t even aware that they are ill.

The good news is that once a person has contracted Zika, they are very unlikely to contract the disease again. First discovered in 1947, the virus is named after the forest in Uganda where it was found. It wasn’t until 1952 that humans first contracted the condition. Since that time, there have been outbreaks reported in tropical areas such as Africa, Southeast Asia as well as the Pacific Islands. While they did occur prior to 2007, most cases weren’t reported at that time. Due to the fact that there are many conditions that mimic the condition, it is likely that the condition was largely misdiagnosed or under diagnosed prior to that time. It wasn’t until May of 2015 that PAHO or the Pan American Health Organization became concerned and issued alerts regarding the virus and unborn children. Since that time more care has been taken to ensure the safety of pregnant women and the virus. It is wise to check with the center for disease control prior to travel if planning a trip in any of those regions, especially if there is a pregnancy involved.

According to the electron micrograph, Zika virus particles are a mere 40nm in diameter and have an outer envelope as well as a dense inner core. The virus is related to such conditions as dengue fever, yellow fever, and Japanese encephalitis as well as that of West Nile virus. These are all considered flaviviruses. Zika is an enveloped icosahedral and also a nonsegmented and a single-stranded positive-sense RNA genome. One of the two Spondweni viruses and only transmitted via mosquito’s as far as scientists have determined at this time.

However, there is a huge concern as there are two lineages of the Zika virus. That of the African lineage and that of the Asian lineage. Studies are underway to check for variants of the condition that may or may not make it treatable. According to earlier studies, the vertebrate hosts of the virus were monkeys in the so-called enzootic mosquito-monkey-mosquito which became a cycle. Prior to the outbreaks of 2007, it is believed that it was extremely rare for humans to contract the disease although there are other conditions that closely mimic that of Zika.

Sadly, the true extent of the virus is largely unknown and medical scientists are still trying to determine whether or not there is a reason for huge concern, especially where anencephaly (babies with undersized heads) are concerned. The main treatment for the condition is rest and more rest. If there are other symptoms such as fever or conjunctivitis typical treatments will include treating the fever accordingly and treating conjunctivitis accordingly.

At present, there is a huge concern for autochthonous infections in more urban areas of the European countries. This is due to the first few cases of lab confirmed Zika outbreaks that were in Italy. However, since these persons had been traveling, it is likely that they contracted the condition while on their travels, and not in Italy. Further studies are underway and will continue until the Center for Disease Control has answers. Until such time the public is advised to be aware of Zika and the damage that it can do if contracted and appropriate measures should be taken to avoid contracting the condition whenever possible.

Since 2015 the Zika virus has been in the news and will continue to be so until such information has come to light. With more awareness there is hope that the virus will slow the spread and that newborn babies everywhere will be able to avoid being contaminated with the virus which can cause serious damage.

West Nile Virus

West Nile virus is a potentially serious disease. It has become a seasonal epidemic in the United States, it’s occurrence peaks in August and September. The best way to protect yourself is to keep from being bitten.

Most commonly, it is transmitted by the Culex species mosquitoes, but the Aedes and Anopheles species transmit it as well.Most often, the mosquito bites an infected bird, and then transmits the West Nile virus to a human through it’s saliva. In very rare cases, it has been transmitted through blood transfusions, breast feeding and during pregnancy, from mother to child. Most often a mosquito bite is the cause of its spread. If you see a dead
bird, DO NOT touch it. West Nile virus affects the central nervous system, but the severity of it’s symptoms
varies widely.Luckily, in about 80% of those infected, no symptoms appear, and they do not become
ill.Other people who have contracted West Nile virus experience mild symptoms, which are very similar to many flu symptoms.
These people can experience nausea, body aches, chills, headaches, fever, swollen glands, and sometimes rashes.These symptoms are reported in about 20% of the cases. The aftermath of the infection can last a few days to a few weeks.Significant symptoms from infection with the virus are not that common, but are quite serious. Only about 150 people infected with the virus each year have these serious symptoms. They include: high fever, muscle weakness, tremors, stupor, convulsions, vision loss, severe headaches, neck stiffness, coma, disorientation, numbness and paralysis. These symptoms can lead to neurological damage, and on very rare occasions, fatal encephalitis, or swelling of the brain. The symptoms, if they occur, will manifest about three to four days after the bite. In milder cases, rest and riding out the symptoms is usually enough. More severe cases need medical attention, including hospitalization.

For the most part, those at risk of the more severe symptoms are individuals over the age of 50. And, anyone who is outside often runs the risk of being bitten and contracting the virus.In 2004, there have been a total of 1191 reported cases in the United States, and 30 fatalities. Since 1999, the Center for Disease Control has had cases from all states in the US except for Alaska, Hawaii, and Oregon. The disease is being reported in Europe, both West and Central Asia, Africa and North America.

View a map of West Nile cases in the United States.

west-nile-virus-states-2015

The disease was first reported in 1937 in the West Nile portion of Uganda. From there, it was found in Egypt in the 1950’s and recognized as a serious cause of fatal encephalitis from an outbreak in Israel in the late 1950’s. It did not appear in the United States until 1999, and then in both humans and horses. It has been found in other animals, such as dogs and cats, but they do not appear to become sick from the virus.

Keep in mind that it can be transmitted through other biting insects, such as ticks and no-see-ums.The best way to avoid being stricken with the virus is to avoid being bitten by mosquitoes, especially in late summer and early fall. Avoid being outside around dusk and dawn, wear protective clothing and a good mosquito repellant, and keep your yard and home as free of breeding grounds as possible.

Encephalitis

While the West Nile virus can result in cases of encephalitis, it is not the only mosquito borne type of encephalic disease; there are several others, some of which are actually more severe. The more common ones are:

EASTERN EQUINE ENCEPHALITIS

As its name implies, this viral infection is found primarily in the Eastern United States. It is a disease that affects both horses and humans. It is transmitted through the bite of a mosquito that has fed on an infected bird. The most frequent species that transmits the disease is the Culiseta melanura.

Far more than West Nile virus, it is one of the more serious of the mosquito borne encephalitic diseases. The symptoms, in their mild form, are like a mild case of the flu. At the other end of the spectrum, it produces encephalitis, or inflammation of the brain, coma and death. It has an alarmingly high mortality rate: 35% of those who contract it die. Of those who survive an infection, about 35% have some residual neurological
damage, ranging from mild to severe.

These precautions are not to be taken lightly, even though the disease is not common, it is
one of the most serious of mosquito borne diseases. Luckily, it is quite rare. From 1964 to the present, only 200 cases have been confirmed in the United States. The states with the highest rates of cases are on the Eastern seaboard,
ranging from Florida to Massachusetts. Part of the reason for its rare occurrence is that carrier mosquitoes that inhabit swamps, which humans do not frequent often.

The greatest risk of danger is among those over 50 and less than 15 years of age who visit, live or work in areas where the mosquitoes are prevalent. The best way to avoid infection is to avoid being bitten. So, stay away from swampy, marshy areas, if you live on or visit the East coast. And, follow the usual precautions about wearing protective clothing, staying inside during feeding times, and always wear a good repellent. Unfortunately, there is no vaccine for humans, although there is one available for horses.

JAPANESE ENCEPHALITIS

This viral infection is transmitted by mosquitoes breeding in rice paddies in Asia, mostly from one of the Culex species. It is closely related to the virus that causes St. Louis encephalitis. In this case, the mosquitoes feed on
infected domestic pigs and birds, which then feed on human hosts. Like the West Nile virus, many people have no symptoms. The milder forms of infection can produce some fever and headaches. The more severe symptoms include high fever, headache, disorientation, coma, neck stiffness, convulsions, stupor, and paralysis.The symptoms usually manifest in one to two weeks after the bite. Its reported mortality rate is very broad, somewhere between .3% to 60%.

This is the leading cause of viral based encephalitis in Asia, but rarely occurs outside of
that area.  Like the other forms of mosquito borne viral encephalitis, there is no treatment, except to
alleviate the symptoms. It is much more common in rural areas of Asia, and is rarely
found in urban areas. Again, the best precaution is to avoid being bitten, and to take action to avoid areas of
exposure.

LACROSSE ENCEPHALITIS

This is one of the more rare forms of mosquito viral encephalitis diseases. And, fatalities are very rare. More often, mild symptoms are the norm. There are only about 70 cases reported each year, and less than 1% of those
result in fatality.It is transmitted mostly by one of the Aedes triseriatus , the treehole mosquito, that is found primarily in wooded habitats. The animal hosts for Lacrosse encephalitis are mostly chipmunks and squirrels. Treehole mosquitoes breed in small collections of water, like crevices in trees, discarded cans and low-lying puddles.

As with all other types of encephalitis diseases, prevention is the best cure. Avoid going into the mosquito’s natural habitat, wear protective clothing, and use a good repellent.

ST. LOUIS ENCEPHALITIS

This virus is very closely related to Japanese encephalitis, but far less prevalent. Mostly, its victims have only a mild illness, although it can produce the more severe symptoms. It occurs with varying frequency, often rarely, but sometimes up to 3000 cases per year. It is spread by various members of the Culex species.

WESTERN EQUINE ENCEPHALITIS

This version of mosquito borne virus is really not at all common. There have been only about 600 reported cases since 1964, and its symptoms are like most encephalitic disorders, mild flu like symptoms to a few, rare deaths. It can be epidemic, but its occurrence is hard to predict. While related to the Eastern equine encephalitis virus, it is simply not as prevalent. There is no known treatment, except addressing symptoms, and the best precaution is avoidance.

As you can see, mosquito borne encephalitic diseases encompass far more than just West Nile virus. And, the best means of combating them is to avoid the bites. The best way to avoid these types of illnesses comes from a double approach. Learn all you can about them, and then be smart about staying out of harm’s way. It is important to take a
balanced view, too. Sure, these are serious diseases, and not to be ignored, but at the same time, recognize
that they are not really than common in urban dwelling environments.

Dengue Fever

Dengue fever (DF) and its more serious counterpart, Dengue hemorrhagic fever (DHF), are quickly becoming a problem in more than the tropic regions where it has been most common.

A virus causes DF, and there are four main strains. Having been infected by one does not prevent contracting the others.So, having endured a bout with one strain does not provide immunity against another illness from one of the other strains.

DF and DHF are spread primarily by the Aedes aegypti, or Asian Tiger, mosquito. Asian Tigers are aggressive day feeders that prefer humans as their main host. View a map of the Asian tiger mosquito’s habitat range.

asian-mosquito-range

Although dengue fever is mostly found in the tropics, it is beginning to be known as a significant disease in otherareas. Dengue fever is not a newcomer to our planet. In Asia, Africa and North America, the first reported epidemics of DF were in 1779-1780. Often there were long periods of time, several decades, between outbreaks, because mosquitoes
could only be carried on slow sailing ships.

Around 1950, a global pandemic occurred, beginning in Southeast Asia and by 1975, DHF had become the leading cause of death in children in the region. Spread of the disease has expanded rapidly in the last 15 years, including increasing reports of cases in the Americas. In fact, the CDC calls the emergence of DF and DHF in the Americas a “major public health problem.” Spraying efforts by public health organizations in the 1950’s and 1960’s significantly reduced Aedes egypti populations, and the spread of this disease, but were abandoned in the United States in the 1970’s. Now the populations of this mosquito are higher than before spraying was conducted.

By 1997, DF/DHF were considered to pose the greatest threat of mosquito borne diseases, rivaling malaria, worldwide. Serious mosquito eradication efforts are imperative, on both a global and community level.
Even the “milder” form of dengue fever is anything but mild. The symptoms are muscular and joint pain, high fever, severe headaches and backaches, vomiting, nausea and eye pain. DHF involves a high fever of extended duration, about 2-7 days. The initial symptoms are like those of many types of flu: headache, nausea, vomiting and abdominal pain. Then small capillaries begin to leak and hemorrhaging can occur through the skin, nose, gums and even internally. Without proper medical management, the hemorrhagic phase may lead to shock, failure of the circulatory system and possibly death.

There is no specific treatment for this fever, other than pain relievers, but aspirin should be avoided because it impairs blood clotting. In DHF, hospitalization is often required to insure proper fluid replacement.

Although dengue fever occurs mostly in tropical area infested with the Aedes aegypti or Aedes albopictus mosquitoes, it may be spread to other areas by travelers carrying the infection. In fact, one strain was found in Central America in 1994 and has spread into several countries in that region. Unfortunately, because the strain had not been present in the area for two decades, immunity in the area is low, and the disease is expected to spread quickly. All of the strains are found the Americas at this time.

No vaccines exist for any of the strains, and prevention is the best cure. Keep standing water clean, or eliminate it. And, avoid being bitten. Be sure all portals in buildings, such as houses, and offices are screened.

Community and governmental efforts to prevent mosquito breeding is essential, through use of natural predators like Btiand copepods.In terms of frequency of reported cases, the Center for Disease Control(CDC) reports there are approximately 50 to 100 million cases per year of DF. DHF infects approximately several hundred thousand people each year. The average rate of fatality for dengue hemorrhagic fever is about 5%. In the Americas in the late 1990’s there were approximately 250,000 cases of dengue fever, and about 7,000 reported cases of dengue hemorrhagic fever. By CDC estimates, between 100-200 cases of this virus are introduced into the United States each year by travelers.
Unfortunately, epidemics of the disease are occurring with increasing frequency and are more widespread than in the past. The CDC draws a parallel in dengue fever’s evolution in the Americas, calling it similar to the pattern of its spread to what occurred in South East Asia in the 1950’s and 1960’s

As our global community becomes more urban, and we continue to become more mobile, the disease is expected to spread rapidly. And, education of medical personnel in the Americas is critical. At the present time the hemorrhagic disease is often poorly understood because it has not been a common ailment.

Malaria

Malaria is not a newcomer on the disease forefront. It was reported as far back as 4000 BC. In the 1700’s, Spanish missionaries in South America learned of a treatment for the disease they called Peruvian bark. The tree that produced this bark was named after the Peruvian countess, Cinchona, and is now known as quinine. Even today, quinine, along with artemisinin, it is one of the most effective drugs available. Artemisinin comes from the sweet wormwood plant, found to be effective for treatment of this disease by Chinese herbalists as early as 340 BC.

Still, even today, public health experts consider it to be one of the most serious and severe mosquito borne diseases.
About 700,000 to 2,700,000 people die each year from it. While most of the fatalities are in Africa, the disease is a world wide problem. Most cases involve bites from one of the Anophelese species. To date, malaria is the leading cause of death and disease, world wide.In the United States, where it is considered to have been eradicated, more than 1300 cases were reported in 2002, of which 8 resulted in fatalities. Most of the cases came from bites acquired in other countries, but since 1957, after eradication was considered complete, there have been 63 outbreaks of malaria from domestic transmission.

Consider this, about 41% of the world’s population lives in areas where itis actively transmitted. And, consider that geographic isolation is no longer feasible, and you get an idea of the danger malaria presents to the human community, planet wide. And, more frightening, these numbers are probably lower than the reality of the situation. Most deaths from malaria occur in Africa, where patients have no access to adequate medical care and die at home. In this instance, under reporting is a real issue. One reason that malaria has been mostly eliminated in the United States and Europe is simply a matter of climate. In areas where freezes occur, the mosquitoes die out. Most of the areas of significant malaria outbreaks are in tropical climates.

The cycle of transmission follow a set pattern. A mosquito bites an infected host and ingests malaria parasites. While the mosquito is unharmed by the parasites, they thrive in the body of the mosquito, and then migrate back to the mosquito’s salivary glands. Once the mosquito bites again, the parasites are injected into the victim. First, the parasites migrate to the host’s liver, where they incubate for about 7-30 days. This is the incubation period and the victim has no symptoms. Then, the parasites enter the bloodstream and infect the red blood cells, causing them to burst. This causes the classic symptoms of malaria.

First, the victim feels cold and often shivers. This is followed by fever, headaches, and vomiting. In young children, seizures can also occur. Last, the victim begins sweating, and normal temperatures resume. Depending on which parasite is involved, the victim will experience these attacks every second day or in three day intervals.

The red blood rupture is what ultimately causes fatality. Particularly in children, insurmountable anemia results.

And, of course, if the victim is bitten by another mosquito, the parasite goes on to find a new host, which spreads the disease.The World Health Organization has attempted to launch efforts to eradicate the disease, but lack of funding and manpower has forced it to focus on control. For now, the best course would appear to be what is true for all mosquito borne diseases: get rid of the vector. Mosquito eradication and avoiding bites is far better than trying to combat the diseases they cause.

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