DENGUE FEVER, YELLOW FEVER AND FLY AND MOSQUITO- BORNE DISEASES

AVOIDING INSECTS

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gambiae mosquito
For protection from insects use an insect repellant with at 30 percent DEET (some people recommend 95 to 100 percent), wear long pants and long sleeve shirts, treated with "Coulston's Duranon Tick, spray, and sleep under an insecticide-impregnated insect netting. Periodically check your body for ticks. If a tick penetrates your skin, remove the entire tick with tweezers or a tick removal kit by grasping the head and slowly backing it out.

Disease-carrying mosquitos, like most mosquitos, generally bite at night between dusk and dawn, and are particularly fierce around sunset. An exception to this rule are mosquito that carries dengue fever. They generally bite in the day. Mosquitos generally go for the lower extremities of the body. People with a high skin temperature and high moisture-transpiration rates sometimes attract more mosquitos.

The best way to avoid disease-carrying mosquitos and insects is avoid the places where the diseases are known to exist. The Center of Disease Control can provide information on countries and regions where diseases are found. Rural areas are generally more risky than urban areas. Local people can often provide information on specific risky places in their area.

The best way to avoid mosquitos is to: 1) stay inside when they are most active (in the late afternoon, early evening, and early morning); 2) sleep under a mosquito net (tucked under the mattress and treated with an insecticide); 3) cover as much of your body with clothing as possible, wearing long sleeve, light-colored, loose-fitting clothing; 4) use a repellant and your skin and a toxicant on your clothing; and 5) stay in hotels that are well-screened or air-conditioned, if screens are insufficient ask for mosquito netting. Fans and mosquito coils are also effective in keeping mosquitos away. Sandals should be avoid and pants should be tucked into socks in places with lots of ticks. White or light clothing makes ticks easier to spot.

Many Africans who live malaria-endemic areas use nets but still get the disease. Many people in hot countries don't like them because the keep out the breeze.

Websites and Resources on Health and Diseases: Centers for Disease Control and Prevention cdc.gov/DiseasesConditions ; Disease Pictures hardinmd.lib.uiowa.edu/pictures ; World Health Organization (WHO)statistics and data who.int/research ; World Health Organization (WHO) disease outbreak alert who.int/csr/disease ; Third World Traveler thirdworldtraveler.com/Disease/diseases ; Health Map healthmap.org ; Medline Plus medlineplus/healthtopics ; Merch Manuals (detailed info many diseases) merckmanuals.com/professional/index ; Health Images Directory healthline.com/directory/images

DEET and Permethrin

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Use a DEET insect repellents on your skin. DEET is a strong chemical that interferes with the tiny sensory hairs and pits in the antenna and body it uses to detect carbon dioxide.. DEET is toxic if ingested; stings eyes severely; and can blister the skin in high concentrations. Repellents with 30 to 35 percent DEET are good. They the usually only last for around five hours. Higher concentrations, such a 95 percent to 100 percent, don’t add any more protection but they last longer. Aerosol insecticides and mosquito coils help to clear rooms but they sometimes contain DDT. Non-DEET repellants generally work 1½ hours or less.

The Centers for Disease Control and Prevention recommend products containing DEET, picaridin, IR3535 and the oil of lemon eucalyptus. They say put some on you clothes for greater protection. If you wear sun screen, apply the insect repellant on top of it.

Use a spray or repellent with Permethrin or Permanone (such as Coulston's Duranon Tick Repellent) on your clothes, shoes, tents, camping gear and bed netting. Permethrin often maintains its potency through ten or more washing. It bonds tightly with cotton fabric and It is effective enough to knock out a mosquito by the time sticks its probe through the cloth and it aims it towards the victims skin.

Some people are turned off by the odor of DEET and the chemical os not suited for all ages. Alternatives include the chemical Picaridin and the plant-based oil of lemon eucalyptus.

See Malaria

Leishmaniasis

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Leishmaniasis bone marrow biopsy
Leishmaniasis is a parasitic disease found in tropical and subtropical areas of the world. Transmitted by the bite of some species of sand fly, it comes in cutaneous (skin) and visceral (internal organ) forms. Cutaneous leishmaniasis is characterized by open or closed skin sores. Visceral leishmaniasis typically develops over several months and is characterized by fever, enlargement of the liver and spleen and anemia.

Leishmaniasis affects about 15 million people a year, mostly in tropical areas. It begins with a bite that doesn't heal and a wound that gets bigger. Many victims have nasty looking lesions. If untreated the lesions can take months and even years to heal and leave behind nasty looking scars. Leishmaniasis can resembles leprosy in its external form. It slowly kills victim in visceral form by eating the internal organs.

Leishmaniasis is transmitted to humans by sand flies that thrive in animal dung used for cooking and thatched used for making roofs in poor villages. The flies that transmit the disease are smaller than mosquitos and easily pass through mosquito netting. They congregate in large number in banana groves and bamboo stands often found near poor villages.

Visceral Leishmaniasis (Black Fever Kala-Azar)

Visceral leishmaniasis, also known as black fever and kala-azar, is the world’s second deadliest parasitic killer after malaria. Spread by sand flies, it causes itchy skin lesions, fever, swelling of the spleen and liver and serious weight loss. A serious form eats away at a victim’s skin and mucosa tissues and can cause death.

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leishmaniasis parasites and fly

Black fever kills about a half million people worldwide annually, nearly all of them poor. In its developed form the disease causes the liver and spleen to expand so much they to bulge from victims rib cage. Describing a 15-year-old boy in Bihar state in India with black fever, Stephanie Strom wrote in the New York Times, “Dilip Manjhi...lay listless on a string bed....Dilip’s spleen extended eight centimeters below his rib cage and was rock hard. His liver protruded three centimeters below his ribs.” About 90 percent of the cases are in Bihar, Bangladesh, Nepal, Sudan and northeastern Brazil. In India the disease is known as kala azar.

Preventing and Treating Visceral Leishmaniasis

Leishmaniasis is cured by grueling course of intravenous medication. The most widely prescribed medicine was discovered more than a century ago and has severe side effects. No vaccines or preventative drugs are available for the disease. Like tsetse flies, the sand flies occupy certain regions, often in the rain forest. Forced by poverty and desperation, more and more people are moving to these areas. The current treatment can be toxic and costs $500 in India.

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leishmaniasis life cycle

Leishmaniasis can be cured and prevented with a series of cheap injections from a drug called paromomycin ---an inexpensive antibiotic used in some places to treat diarrhea that was found promising in the 1960s but never made it to the market place because it was determined that there was not enough profit in it to justify carrying out expensive trials.

The Gates Foundation has donated $30 million to combat leishmaniasis. The Institute of One-World Health, a small San-Francisco-based charity supported with a $47.2 million grant from the Gates foundation, is currently trying to get paromomycin to the desperately poor who need by conducting trials to prove the drug is safe and effective. If the drug is approved a course of treatment that cost less than $10 per person could virtually eliminate the disease. In India, One-World is working the Indian drug company Gland Pharma to produce and sell the drug at cost. A big hurdle that still has to be overcome is getting the drug to remote villages where it is needed most.

Preventative measures focus on reducing man-fly contact. The flies are most active at dawn and dusk and bite mostly at night (or during the day when disturbed). They are about a third smaller than mosquitos so netting should be a fine mesh variety with at least 18 holes to the linear inch. This netting is sometimes intolerably hot in tropical areas. Regular mosquito netting sprayed with an insecticide is relatively effective.

Lymphatic Filariasis

Lymphatic filariasis is a disease that infects 120 million people, of which 43 million are sick. Caused by parasitic filarial worms ( wuchereria bancrofti ) and transmitted by mosquitoes, it can cause fevers and asthma-like breathing difficulties. The worms reside in the lymph nodes and muscle tissues. In its most extreme form (elephantiasis, often misspelled and mispronounced as “elephantitis”), the legs, arms and male genitals swell to a huge size as a result of the accumulation of lymphatic fluid. Dog heartworm is also caused by filarial worms.

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Lymphatic filariasis life cycle

Lymphatic filariasis can be treated with a drug called diethylcarbamazine (DEC). DEC, used in conjunction with invermectin, a powerful drug donated by the drug giant Merck, reduces 99 percent of the filariasis parasite concentrations in the victim's blood. The disease can be prevented by taking the drug Albendazole

In Sweden, an increase in number of cases of tick-borne encephalitis has been blamed on global warming.

Japanese Encephalitis

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Culex vishui mosquito
Japanese encephalitis is a mosquito-born viral disease that usually infects people in rural areas in the summer and autumn in temperate regions and northern tropical zones of Bangladesh, China, India, Cambodia, Korea, Laos, Myanmar, Nepal, Thailand, Vietnam and eastern Russia. It is sometimes present in the wet season in the tropical zones of south India, Indonesia, Malaysia, the Philippines, Singapore, Sri Lanka. Taiwan and south Thailand.

Japanese encephalitis is transmitted chiefly by the Culex vishui and Culex tritaeniorhyncus mosquitos, which bite mainly in the afternoon and evening and develop from larvae found mainly in cultivated rice fields and marshes. People traveling in rural areas have a stronger likelihood of contacting the disease than those who stay in urban areas.

Most people who are infected display no symptoms, but the fatality rate is as high as 30 percent among victims who are hospitalized. Severe swelling in the head and central nervous system are manifestations of severe cases of the disease.

There is a vaccine that is given in a series of two or three injections one or two weeks apart. There is no medical cure but most victims recover on their own with rest and hospital care.

Encephalitis is a tick-bourne disease that often produces fatal swelling of the brain. Symptoms include fever, headache vomiting, neck stiffness, pain in the eyes when looking at light, alterations in consciousness, seizures, paralysis or muscle weakness. Correct diagnosis requires hospitalization. There are vaccines for encephalitis and specific tick-borne encephalitis immune globulin. Encephalitis prevention includes avoiding places with ticks such as high grass, edges of forests, clearings.

Dengue Fever

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aegypti mosquito
Dengue fever is a nasty, viral disease transmitted by the Aedes mosquito, usually the Aedes aegypti , the same mosquito that often carries yellow fever. Sometimes called "breakbone fever" or "break-heart" because of the intense pain it can produce, the disease is characterized by sudden onset of fever; intense pounding, frontal headaches; aching bones and joints; nausea and vomiting; and a feeling of being too sick to eat anything. Other symptoms include severe sweats, symptoms: eye pain, rash, chills, and excruciating chest pains. Tests foe dengue rely on the presence of antibodies, which can take up to a week to develop.

Dengue fever is found in 100 countries and kills about 20,000 people annually. Nine out of 10 people who get dengue fever don’t even feel it or get a mild case in which they feel something akin to a slight flu. People who get full-blown dengue fever are sick for a week or more. Many patients have a rash, which appears 3 to 5 days after the onset of the disease, and experience severe emotional and mental depression during the recovery period. Most cases of the disease are benign and self-limiting although convalescence may take a long time.

A few people with dengue fever suffer gastrointestinal bleeding. Fewer still suffer brain hemorrhages. In about 1 percent of cases dengue fever can cause a severe and often fatal hemorrhagic disease called dengue hemorrhagic fever (DHF) that occurs when capillaries leak and the circulatory system collapses.. Those that die of dengue fever often get DHF hemorrhaging in the final stage of the sickness. Failing to realize they are infected, they go don’t get treatment soon enough and lose blood plasma and go into shock after the initial fever passes. Some victims die within 10 hours of developing serious symptoms if they don’t get appropriate treatment.

There are several strains of dengue fever (the four main one are immunologically related). Those who get the disease develop an immunity to the strain they were infected by but are more likely to get DHF and get seriously sick if they get infected with a second, different strain. Scientists are not sure why this happens but think it may be because the immune system reacts the second time as if the invader were the first strain, wasting precious energy and leaving the body vulnerable to an attack by the second strain. Many doctors believe that since so few people show symptoms the when get dengue those that do display symptoms probably have gotten the disease a second time from a second strain. Getting the disease twice for two different strains seems to provide immunity for life from all strains of dengue fever.

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mosquito stages of development

History of Dengue Fever

Dengue fever and yellow fever are so closely related they are regarded as sister diseases. Dengue was first identified about 300 years ago but remained an isolated problems until it was spread around Asia and Pacific by troops during World War II. Both dengue and yellow fever were thought to have been close to eradication in the 1940s but have since made comebacks. The disease took off in crowded conditions in Asia. By 1975 it was a leading cause of hospitalization and death among children in the region.

From Southeast Asia dengue fever made its way to India, Africa, the eastern Mediterranean and finally to the Americas where it emerged as a threat in the 1970s just as campaigns to stamp out yellow fever in Latin America were declared a success.

Several new strains of the dengue virus have emerged in Asia and Latin America since the mid-1970s. The disease was a problem in Latin America and the Caribbean in the 1980s and 90s. It first took hold in Central and South America and progressed into Caribbean and the southern United States. There were 116,000 infections in Latin America alone in 1990. Cases have been reported in Florida and Hawaii.

In recent years there have been severe outbreaks of nasty forms of dengue fever and of DHF in Southeast Asia. See Thailand, Indonesia and Southeast Asia.

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One Person’s Experience with Dengue Fever

Dengue fever often begins with a headache and an achy feeling. The headaches seems to migrate towards the eyes behind the sockets as fever takes hold rises. If full-blown symptoms take hold the pain spreads throughout the entire body.

One suffer who was struck by dengue fever in Singapore wrote in the New York Times, “Not for nothing is dengue also known as breakbone fever...I, for one, felt as though someone had tied a Brink’s truck to my lower back. My skin was flushed, I could not eat, and I slept 12 to 14 hours at stretch. When I went to my doctor two days later, I could hardly open my blood-stained eyes...The doctor had little choice but to send me home with the painkiller Panadal and some muscle relaxants.”

“A week after my first feverish night, a doctor looked at the tiny pinpricks of blood under the skin on my shoulders, and sent me for a blood test, which confirmed that I had dengue...My first blood tests also revealed that my platelets---the cells that allow blood to clot and prevent hemorrhaging---had dropped to almost half of what doctors consider normal. They weren’t low enough for me to be hospitalized for transfusions, fortunately, but they were low enough to earn me daily blood tests to make sure.”

“The virus had inflamed my liver, as well, sending liver enzymes into my bloodstream, another mysterious symptom. For weeks after my fever subsided and my platelets returned to normal, I was still laid out, lethargic and giddy. My appetite returned slightly, but food and even water tasted strangely unpleasant...A month of afternoon naps later I was completely recovered.”

Dengue Fever Mosquitos

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Where dengue fever is found in Africa, Asia and Oceania
Aedes aegypti is a small, dark mosquito with white markings and banded legs. It originated in Africa and made its way around the globe centuries ago when it hitchhiked on transoceanic voyages.

Aedes aegypti mosquitos prefer to feed on humans during the daytime and are most frequently found in or near human habitations. They are most likely to bite during a period of several hours in the late afternoon before dark and for several hours after day break.

In 2007, scientists published the genome---a map of all the DNA---of the Aedes aegypti, the mosquito that carries yellow fever and dengue fever. It turns out the genetic make up of this mosquito is more complex than the one that carries malaria. Both Aedes aegypti and the mosquito that carries malaria have about 16,000 genes but the genome for Aedes aegypti is about five times larger.

Dengue Fever Treatment and Prevention

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spread in Western Hemisphere
Dengue fever has no vaccine and no cure. Most victims that show symptoms recover on their own with rest and hospital care. Dengue fever can be avoided by staying out of endemic areas (the Center of Disease Control can tell you where they are) and protecting oneself against mosquitos.

Dengue outbreaks often have followed unusually hot, rainy and humid conditions. The danger of dengue fever rises when there is a lot of stagnant water for mosquitos to breed in. In some places where it rains a lot people get infected every two or three years as their immunity from the previous illness lasts only a year and they get infected again..

Developing a vaccine against dengue fever is difficult because one a vaccine has to be developed that can work on all the strains.. Scientists are tinkering with the genetic material of 17D to come with a vaccination for dengue fever. See Yellow Fever.

Scientist were able to wipe out mosquitos that carry Dengue fever in a village in northern Vietnam by using a one-eyed crustaceans that lives in ponds where mosquitos breed and has a large appetite for the larvae mosquitos that carry Dengue fever.

There are concerns dengue fever could spread northwards, even becoming common place in the United States, as result of global warming. Already species capable of carrying the disease have been found in 28 states in the U.S. and as far north as the Netherlands in Europe. Cases of dengue fever have been reported in all 50 U.S. states but people who had it contacted the disease abroad and brought it home.

Yellow Fever

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aedes
Yellow fever is the second most dangerous mosquito-borne disease after malaria. It is a viral infection transmitted by Aedes aegypti mosquitos and is endemic to zones in tropical Africa and South America. Urban yellow fever is carried the Aedes aegypti mosquito. Jungle yellow fever is an enzootic disease transmitted among nonhuman primate hosts by a variety of species of mosquitos.

Yellow fever victims often suffer from jaundice (a liver disease that yellows the skin), hence the name yellow fever. Other symptoms include headache, chills, nausea, and vomiting. Severe cases can infect the blood, liver and kidneys.

Dengue fever and yellow fever are so closely related they are regarded as sister diseases. Yellow Fever sometimes picked by mosquitos from monkeys that carry the disease with no ill effects. Tissue and blood samples are taken from hunted monkeys to find source of disease and define infected area.

Yellow fever is found primarily in the 34 countries that make up Africa's "yellow fever belt." Each year there are around 200,000 news cases of yellow fever and 20,000 to 30,000 deaths attributed to the disease. Although a vaccine has been around for decades the number of people have become infected with the disease has risen in the past 20 years according to the World Health Organization (WHO).

Yellow Fever Mosquito

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yellow fever parasite
Aedes aegypti is a small, dark mosquito with white markings and banded legs. It originated in Africa and made its way around the globe centuries ago when it hitchhiked on transoceanic voyages.

Aedes aegypti prefers to feed on humans during the daytime and is most frequently found in or near human habitations. They most commonly bite for several hours after day break and for several hours in the late afternoon before dark.

In 2007, scientists published the genome---a map of all the DNA---of the Aedes aegypti, the mosquito that carries yellow fever and dengue fever. It turns the genetic make up of this mosquito is more complex than the one that carries malaria. Both Aedes aegypti and the mosquito that carries malaria have 16,000 genes but the genome for Aedes aegypti is about five times larger.

History of Yellow Fever

Yellow fever originated in Africa. In the 16th or 17th century, the larvae of its carrier, the Aedes aeyoti mosquito was likely transported from West Africa to the New World in water casks carried aboard slave ships and found an ecological niche in its new home.

The United States suffered greatly from the disease. Philadelphia lost ten percent of its population in one outbreak in 1793, and the urban mortality rates from yellow fever reached 50 percent in some cities in the 19th century. People thought the disease was spread by the vomit or clothes of sick people. The French also suffered. In 1802, Napoleon sent 33,000 men to Haiti and the Mississippi Valley. 29,000 of them succumbed to yellow fever. He became fed with the New World. And this is one of the reasons he made the Louisiana purchase deal with the United States for such a small amount of money.

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Renowned U.S. Army pathologist Walter Reed discovered the cause of yellow fever during an outbreak of the disease during the Spanish American war in Cuba. Using volunteers as guinea pigs, Reed determined that yellow fever was transmitted by the Aedes aegypti . Reed's work inspired a huge campaign to get rid of the disease-carrying mosquitos by killing them with fumigators and by getting rid of supplies of standing water. The number of cases of yellow fever dropped from 1,400 cases in 1900 to 37 in 1901.

The disease was controlled in Cuba and later in Panama, where the Panama canal was being built, eliminating mosquito breeding habitats (namely still water) and installing screens. After World War II, DDT was used to get rid of mosquitos around the world and yellow fever as well as malaria, dengue and other diseases were declared "under control."

In the early 1900s, John D. Rockefeller, one of the richest men in the world at that time, tried to eradicate yellow fever. He was successful wiping out in the United States but not globally.

In the 1930s, soon after the vaccine was developed, yellow fever began to disappear in Africa due to an aggressive immunization campaign. By the late 1950s it was very rare. In the 1960, the vaccinations campaign came to a halt in many African countries. By the 1980s, yellow fever was staging a comeback.

Berries from a common weed found in India shows promising fighting mosquitos that spread dengue fever and yellow fever. In the online open-access journal BMC Complementary and Alternative Medicine, scientists in India described how the juice and extracts from the Solanum villosum weed was particularly effective in eliminating Stegomyia aegypti larvae.

Yellow Fever Vaccination

In 1927, a Ghanian man named Asibi came down with yellow fever. Scientists isolated some yellow fever from his blood and over the years cultivated it in laboratories and fed it to mouse embryo cells and later chicken embryo cells. The virus survived this regimen but became too weak to cause the disease. A vaccine made from it, called 17D, has been given to 300 million people. Scientists are tinkering with the genetic material of 17D to come with a vaccination for dengue fever.

There is a widely available yellow fever vaccination that is given in a single dose that lasts for ten years. Many countries require travelers visiting their country to have it (some of them require evidence of the vaccination from all entering travelers, others require it from travelers coming from a country where yellow fever is found). People receiving a vaccination receive an International Certificate of vaccination completed, signed and validated with the stamp of the Yellow Fever Vaccination Center.

There is also no medical cure for yellow fever. Most victims recover on their own with rest and hospital care.

Image Source: Centers for Disease Control and Prevention cdc.gov/DiseasesConditions

Text Sources: CDC Health Information for International Travel, U.S. Department of Health and Human Services; National Geographic, New York Times, Washington Post, Los Angeles Times, Times of London, The New Yorker, Time, Newsweek, Reuters, AP, Lonely Planet Guides, Compton’s Encyclopedia and various books and other publications.

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© 2009 Jeffrey Hays

Last updated March 2011

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