• Two forms of mosquito transmitted encephalitis may occur in Utah: western equine encephalitis (WEE) and St. Louis encephalitis (SLE).  WEE effects both humans and horses; SLE effects only humans and some birds (emus).
  
• The last outbreak of WEE in humans in Utah was in 1958.  There has never been a human outbreak of SLE in Utah.
  
  
• WEE and SLE are characterized in their most severe form by signs and symptoms of long-term residual neurological damage, which may include paralysis, memory loss, deterioration of fine motor skills, or death.
  
  
• The Utah Mosquito Abatement Association (UMMA), Utah State Health Department (USHD) and the Utah State Agricultural Department (USAD) has had a cooperative encephalitis surveillance program since 1983.
  
  
• The virus that causes WEE or SLE is naturally found in wild bird populations. If a Culex tarsalis female mosquito (only female mosquitoes bite) takes a blood-meal from an infected bird and later takes a blood-meal from a human or horse then those animals may become infected.
  
  
• The mosquito that transmits WEE or SLE in Utah is called Culex tarsalis. This mosquito primarily feeds on birds, and will readily bite man.  The Culex tarsalis bite only at dusk and dawn.  If you are outside at that time precautions can be taken to minimize risk.
  
  
• A total of 20 flocks of 20 chickens each are place in mosquito abatement districts in the northern 2/3 of the state, as well as, in the Moab area.
  
  
• Blood samples are taken from the chicken flocks, and tested for the presence of antibodies to WEE and SLE viruses.
  
  
• The purpose of the sentinel chicken flocks is to allow early detection of viral activity in the chickens before man or horses are affected.
  
  
• Early detection of encephalitis viral activity will hopefully give the mosquito abatement districts a chance to concentrate their efforts in reducing the populations of the mosquito species Culex tarsalis, which transmits the virus.

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Canine heartworm disease (CHD), commonly called dog heartworm, is caused by filarial worm, Dirofilaria immitis being transmitted to dogs while being bitten by a mosquito.  In Davis County, the western tree hole mosquito (Aedes sierrensis) is the most efficient carrier of CHD.

The first locally acquired case of CHD, in Utah, was diagnosed from Davis County in 1987.  Several dozen CHD cases have now been reported from Weber, Davis and Salt Lake Counties.  It is believed that once established in an area, CHD cannot be eliminated.

Severe heartworm infections can cause damage to the dog's heart and other organs before visible signs or symptoms appear.  The disease is usually in its advanced stages by the time typical symptoms - coughing, labored breathing, uncommon weakness and tiring are seen.  A severe infection often leads to heart failure or related complications, and death.

Your veterinarian can diagnose the presence of adult heartworms.  In many cases he can prevent the further development of heartworm disease.

Heartworms have a life cycle unlike that of any other worms in dogs.  They can be transmitted from dog to dog only through the bite of a mosquito.

There are four basic stages in the life cycle of the heartworm. 

1.     When the mosquito bites a dog it passes infective larvae into the dog's skin. Each larva burrows into tissue under the skin where it lives for the next 90 to 100 days and develops about 3 inches in length.  It then penetrates the blood vessels and moves to the dog's heart, where it settles in the right side of the heart or in adjoining blood vessels.  It remains there to complete its growth within five months.  When fully grown, the female beings producing microfilariae and the cycle repeats once again.

2.     The adult female worm-- at least 6 month old and living in the dog's heart-- produces small, immature worms called microfilariae.  The microfilariae are released into the dog's blood stream.

3.     Microfilariae do not grow, but continue to live and circulate in the blood stream for as long as three years, even if the adult worms die.  They must develop further in the body of a mosquito to becomes infective for a dog.

4.     When a mosquito draws blood from a heartworm infected dog, it takes in a number of microfilariae with the blood.  Within the mosquito, the microfilariae undergo a transformation to infective larvae, in about 14 to 21 days.  These infective larvae are really miniature adults, small enough to live in the mosquito's body.

Adult heartworms live for approximately five years.  The microfilariae they produce will live in the blood stream for at least three years.  A single infected dog can be a constant source of infection to all dogs in the community -- when mosquitoes are present.

The microfilariae life cycle cannot be completed without the mosquito.  There is a direct relationship between the number of dogs with heartworms and the number of mosquitoes.  The length of the mosquito season is also a factor.  A longer season means a longer period each year during which dogs are exposed.  Even in short mosquito season areas each infected dog is a source of new infections as soon as the mosquitoes return.

An infected dog is not only a source of infections for heartworm-free dogs; infected dogs can also be constantly reinfected-Theoretically, by the same mosquito.

Dogs of all breeds are susceptible.  Mosquitoes will generally feed in the abdominal region, where even long-haired dogs have little hair cover.

Your veterinarian can normally detect adult heartworms through a blood test.  He looks for the presence of microfilariae in the blood. If the test is positive, he may begin a program to remove the adult heartworms, or in effect, convert the dog to a negative state.

Most dogs can be treated successfully if the disease is not in its advanced stages. Drugs are administered that cause adult heartworms to die.  Dead worms decompose and are absorbed by the body over a period of time. The treatment period is critical.  Your veterinarian will keep close watch until all danger of post-treatment reactions have passed.

Present treatments will remove adult heartworms, but will not affect the microfilariae circulating in the blood stream or immature infective larvae which may also be present.  This requires a separate treatment.

The most effective and practical means of controlling heartworms today is to prevent them from ever reaching the adult stage.

A new drug, administered daily during the mosquito season, prevents the maturing of infective larvae into adult heartworms.  This drug offers the additional benefit of preventing and controlling roundworms and hookworms.

Several precautions are necessary.  The drug must not be administered to dogs with established heartworm infections until they have been converted to a negative state.  It must be administered from the beginning of the mosquito season until two months after the season ends.  Where mosquitoes are present year-round, it must be administered year-around.

The drug is available only from your veterinarian, and it must be administered only under his directions. 

The incidence of heartworm disease is spreading rapidly.  Don't wait until you suspect a problem.  Have your dog checked twice yearly and depend on your veterinarian to advise you as to the steps you should take to keep your dog free of this serious disease.

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Rabies is an infectious viral disease that affects the nervous system of humans and other mammals.  People get rabies from the bite of an animal with rabies (a rabid animal). Any wild mammal, like a raccoon, skunk, fox, coyote, or bat, can have rabies and transmit it to people.  It is also possible, but quite rare, that people may get rabies if infectious material from a rabid animal, such as saliva, gets directly into their eyes, nose, mouth or wound.

Because rabies is a fatal disease, the goal of public health, is first, to prevent human exposure to rabies by education and, second, to prevent the disease by anti-rabies treatment if exposure occurs. Tens of thousands of people are successfully treated each year after being bitten by an animal that may have rabies.  A few people die of rabies each year in the United States, usually because they do not recognize the risk or rabies from the bite of a wild animals and do not seek medical advice.

Most of the recent human rabies cases have been caused by rabies virus from bats.  Awareness of the facts about bats and rabies can help people protect themselves, their families, and their pets.  This information may also help clear up misunderstandings about bats.

When people think about bats, they often imagine things that are not true.  Bats are not blind.  They are neither rodents nor birds.  They will not suck your blood - and most do not have rabies.  Bats play key roles in ecosystems around the globe, from rain forests to deserts, especially by eating insects, including agricultural pests.  The best protection we can offer these unique mammals is to learn more about their habits and recognize the value of living safely with them.

Rabies can be confirmed only a laboratory.  However, any bat that is active by day, is found in a place where bats are not usually seen (for example, in a room in your home, or on the lawn), or is unable to fly is far more likely than others to be rabid.  Such bats are often the most easily approached.  Therefore, it is best never to handle any bat.

If you are bitten by a bat - or if infectious material (such as saliva) from a bat gets into your eyes, nose, mouth, or a wound - wash the affected area thoroughly with soap and water and get medical advice immediately.  Whenever possible, the bat should be captured and sent to a laboratory for rabies testing.

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Rocky mountain spotted fever (RMSF) is a tick-borne, rickettsial infection with the majority of the cases reported in the Eastern half of the United States.

The major symptoms are as follows: fever, occurring usually about 3 to 10m days after exposure often including sever headache, general discomfort and other flu-like symptoms; edema is also common at this point.  Usually about 1-5 days after the fever begins a rash develops, first appearing on the extremities, including the palms and soles of the feet, and moving inward as time progresses.  The rah in initially macular but soon becomes petichial.  Because of the irregularity of occurrence of symptoms, RMSF has proved a difficult disease to diagnose.

If infection goes untreated the organisms invade endothelial cells and vascular smooth muscle cells of the kidneys, heart, brain, and subcutaneous tissues (which accounts for the petechial rash in later stages).  Death usually is caused by toxemia, shock, vasomotor weakness, renal failure, cardiac, or respiratory failure.

Another problem in the diagnosis of RSMF is the fact that the symptoms mimic those of other diseases like meningocccemia, atypical measles, rubella, scarlet fever, toxic shock syndrome, typhoid, secondary syphilis and many others.

The disease is usually passed to man by the bite of an infected tick.  Attachment must be for at least two hours in order to pas the pathogen.  Transmission can also occur by handling a crushed tick or by contact with tick excretions.

In the Eastern U.S. the primary vector is the dog tick (Dermacentor variablis). This tick can be found all over the United States except the Rockies.  The vector in the West is the Rocky Mountain wood tick (Dermacentor andersoni).  The Dermacentor genus can usually be distinguished by the reddish brown color and particularly the complex white ornations on the tick's scutum.  THe Lone Star tick (Amblyomma americanum) is a vector of the Southeastern states and as far north as Delaware.  It is characterized by an obvious "star" at the base of the scutum.  The HLP tick has also been shown to possess the Ricketsia but this tick-rabbit interaction serves to maintain the microbe in nature.  The Latin American vector is Amblyomms cajennense.

The most effective form of control of RMSF is an educated public.  Spraying tactics or preventive drug therapy will only select for resistant strains and create more problems. People living in endemic areas must be aware of the disease and exercise some preventive measures.  These include avoiding wooded areas; wearing light clothing, tucked in at the cuffs; performing body searches, including pets, after visits to tick areas; promptly removing any ticks with a pair of tweezers, applying constant traction as close to the tick-skin border, and avoiding direct contact with the removed tick.  If RMSF is diagnosed in the early stages it can be stopped by antibiotics.  Tetracycline is used except in pregnant women and children under 8 years old.  (Chloramphenicol is substituted).  Other antibiotics are ineffective and sulfonamides actually worsen the disease.  There is not vaccine in current use today, but recent work in the cloning of rickettsia antigen genes for use as a vaccine has been successful in mice.

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Lyme disease is an infection caused by a bacteria balled Borrelia burgdorfero.  On the west coast of the United States it is carried by the Western Black legged tick and can be transmitted through its bite.  The disease is name dafter the town of Old Lyme, Connecticut, where some of the first cases were discovered. Lyme disease is the most common tick-borne disease in the United States.  The disease has been reported in humans, dogs, horses, cattle, and in other wild animals but rarely in cats.

If you are bitten by a tick, of think you have been, it is important to watch for early symptoms of Lyme disease.  One of the first symptoms is a rash that slowly enlarges, usually at the site of the bite and from about the size of a half dollar or larger to a large circular rash with a clear area in the center. The rash may have a bull’s –eye appearance.  It should appear in about seven to ten days and sometimes up to 30 days after the tick bites.  Keep in mind that the rash will only appear in about 60% of cases.  In addition to the rash, flu-like symptoms such as fever, body aches, vomiting, and fatigue may be experiences.  If you have been to an area where ticks occur, found a tick attached to your skin, or believe you have been bitten by a tick and have any of the disease symptoms, you should see your doctor immediately.  When possible, recover and save the tick.

To remove a tick, grasp it with a tissue or preferable with a pair of tweezers.  Never handle a tick with your bare hands.  Pull the tick slowly but firmly straight out from the skin.  Soon the tick should come loose.  Do not twist the tick or use a burning cigarette or match, Vaseline, nail polish, or kerosene in an attempt to remove it.  After removal, wash the area with warm soapy water.  Also, if you have a rash, take pictures of it.  Early recognition of Lyme disease is important.

Sources: http://www.sutter-yubamvcd.org/Lyme%20Disease.htm

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Yellow fever is a serious viral infection, transmitted by mosquitoes in tropical regions.  It has both an urban cycle and a jungles cycle the relies on monkeys as carriers. (‘Sylvatic cycle’).  In mild cases the symptoms are similar to influenza, but serious cases develop a high temperature and may have a series of after effects, such as internal bleeding, kidney failure, and meningitis.  A classic feature of yellow fever is hepatitis, which is the reason for the yellow coloring of the skin (jaundice) and the name of the disease.

The virus is transmitted among humans by a couple of species of mosquito, including Aedes egyptii, which can also transmit dengue fever.  In its original jungle cycle, the mosquito sucks the blood of an infected monkey.  The mosquito develops a permanent infection, in which the virus accumulates in its salivary glands.  Then the mosquito bites another monkey, which then also becomes infected with the virus.  A person traveling through the jungle may also become infected by an infected mosquito.  When this person returns to the urban areas, a new cycle begins.

Urban cycles start when an infected traveler returns from the jungles.  A mosquito bites the traveler, who then becomes infected and passes the virus on to other people, and either an epidemic breaks out, or an endemic situation is perpetuated.

The virus is constantly present with low levels of infection. (i.e. endemic) in some tropical areas of Africa and the Americas.  This viral presence can amplify into regular epidemics.  Until the start of this century, yellow fever outbreaks also occurred in Europe, the Caribbean islands and Central and North America.  Even though the virus is not felt to be present in these areas now, they must still be considered at risk for yellow fever epidemics.

Thirty three countries, with a combined population of 508 million are at risk in Africa.  These lie within a band from 15 degrees North to 10 degrees South of the equator. In the Americas, yellow fever is endemic in nine South American countries and in several Caribbean islands.  Bolivia, Brazil, Colombia, Ecuador and Peru are considered at greater risk.

Souces: www.netdoctor.co.uk/travel/diseases/yelllowfever.htm
http://www.who.int/inf-fs/en/fact100.html

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Malaria is a life-threatening parasitic disease transmitted by mosquitoes.  It was once thought that the disease came from fetid marshes, hence the name mal aria (bad air).  IN 1880, scientists discovered the real cause of malaria a one cell parasite called plasmodium.  Later they discovered that the parasite is transmitted from person to person through the bite of a female Anopheles mosquito, which requires blood to nurture her eggs.

Today approximately 40% of the world’s population mostly those living the worlds poorest countries is at risk of malaria.  The disease was once more widespread but it was successful eliminated from many countries with temperate climates during the mid 20^th century.  Today malaria is found throughout the tropical and sub-tropical regions of the world and causes more than 300 million acute illnesses and at least one million deaths annually.

Symptoms of malaria include fever and flu-like illness, including shaking chills, headache, muscle aches, and tiredness. Nausea, vomiting and diarrhea may also occur. Malaria may cause anemia and jaundice (yellow coloring of the skin and eyes) because of the loss of red blood cells.  Infection with one type of malaria, Plasmodium falciparum, if not promptly treated, may cause kidney failure, seizures, mental confusion, coma and death.

Soucres: www.rbm.who.int/cmc_upload/0/000/015/372/RBMInfosheet_1.htm
www.cdc.gov/travel/malinfo.htm

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