Leishmaniasis refers to several different illnesses caused by infection with an organism called a protozoan.
Protozoa are considered to be the most simple organisms in the animal kingdom. They are all single-celled. The types of protozoa that cause leishmaniasis are carried by the blood-sucking sandfly. The sandfly is referred to as the disease vector, simply meaning that the infectious agent (the protozoan) is carried by the sandfly and passed on to other animals or humans in whom the protozoan will set up residence and cause disease. The animal or human in which the protozoan then resides is referred to as the host.
Once the protozoan is within the human host, the human's immune system is activated to try to combat the invader. Specialized immune cells called macrophages work to swallow up the protozoa. Usually, this technique kills a foreign invader, but these protozoa can survive and flourish within macrophages. The protozoa multiply within the macrophages, ultimately causing the macrophage to burst open. The protozoa are released, and take up residence within other neighboring cells.
At this point, the course of the disease caused by the protozoa is dependent on the specific type of protozoa, and on the type of reaction the protozoa elicits from the immune system. There are several types of protozoa that cause leishmaniasis, and they cause different patterns of disease progression.
At any one time, about 20 million people throughout the world are infected with leishmaniasis. Between one million and one and one-half million cases of cutaenous leishmaniasis are reported yearly worldwide. While leishmaniasis exists as a disease in 88 countries on five continents, some countries are hit harder than others. These include Bangladesh, India, Nepal, Sudan, Afghanistan, Brazil, Iran, Peru, Saudi Arabia, and Syria. Other areas that harbor the causative protozoa include China, many countries throughout Africa, Mexico, Central and South America, Turkey, and Greece. Although less frequent, cases have occurred in the United States, in Texas.
As Americans travel to these countries, they will come in contact the protozoa that cause forms of leishmaniasis. Also, physicians were advised in 2004 to suspect cutaneous leishmaniasis in military personnel who were deployed to areas where the infection is present. From August 2002 to February 2004, staff from the U.S. Department of Defense identified 522 confirmed cases of the disease in American military personnel.
In some areas of southern Europe, leishmaniasis is becoming an important disease that infects people with weakened immune systems. In particular, individuals with acquired immunodeficiency syndrome (AIDS ) are at great risk of this infection.
Causes and symptoms
There are a number of types of protozoa that can cause leishmaniasis. Each type exists in specific locations, and there are different patterns to the kind of disease each causes. The overall species name is Leishmania (commonly abbreviated L.). The specific types include: L. Donovani, L. Infantum, L. Chagasi, L. Mexicana, L. Amazonensis, L. Tropica, L. Major, L. Aethiopica, L. Brasiliensis, L. Guyaensis, L. Panamensis, L. Peruviana. Some of the names are reflective of the locale in which the specific protozoa is most commonly found, or in which it was first discovered.
Localized cutaneous leishmaniasis
This type of disease occurs most commonly in China, India, Asia Minor, Africa, the Mediterranean Basin, and Central America. It has occurred in an area ranging from northern Argentina all the way up to southern Texas. It is called different names in different locations, including chiclero ulcer, bush yaws, uta, oriental sore, Aleppo boil, and Baghdad sore.
This is perhaps the least drastic type of disease caused by any of the Leishmania. Several weeks or months after being bitten by an infected sandfly, the host may notice an itchy bump (lesion) on an arm, leg, or face. Lymph nodes in the area of this bump may be swollen. Within several months, the bump develops a crater (ulceration) in the center, with a raised, reddened ridge around it. There may be several of these lesions near each other, and they may spread into each other to form one large lesion. Although localized cutaneous leishmaniasis usually heals on its own, it may take as long as one year. A depressed, light-colored scar usually remains behind. Some lesions never heal, and may invade and destroy the tissue below. For example, lesions on the ears may slowly, but surely, invade and destroy the cartilage that supports the outer ear.
Diffuse cutaneous leishmaniasis
The lesions of diffuse cutaneous leishmaniasis are very similar to those of localized cutaneous leishmaniasis, except they are spread all over the body. The body's immune system apparently fails to battle the protozoa, which are free to spread throughout. The characteristic lesions resemble those of the dread biblical disease, leprosy.
This form of leishmaniasis occurs primarily in the tropics of South America. The disease begins with the same sores noted in localized cutaneous leishmaniasis. Sometimes these primary lesions heal, other times they spread and become larger. Some years after the first lesion is noted (and sometimes several years after that lesion has totally healed), new lesions appear in the mouth and nose, and occasionally in the area between the genitalia and the anus (the perineum). These new lesions are particularly destructive and painful. They erode underlying tissue and cartilage, frequently eating through the septum (the cartilage that separates the two nostrils). If the lesions spread to the roof of the mouth and the larynx (the part of the wind pipe which contains the vocal cords), they may prevent speech. Other symptoms include fever, weight loss, and anemia (low red blood cell count). There is always a large danger of bacteria infecting the already open sores.
This type of leishmaniasis occurs in India, China, the southern region of Russia, and throughout Africa, the Mediterranean, and South and Central America. It/is frequently called Kala-Azar or Dumdum fever.
In this disease, the protozoa use the bloodstream to travel to the liver, spleen, lymph nodes, and bone marrow. Fever may last for as long as eight weeks, disappear, and then reappear again. The lymph nodes, spleen, and liver are often quite enlarged. Weakness, fatigue, loss of appetite, diarrhea, and weight loss are common. Kala-azar translates to mean "black fever." The name kala-azar comes from a characteristic of this form of leishmaniasis. Individuals with light-colored skin take on a darker, grayish skin tone, particularly of their face and hands. A variety of lesions appear on the skin.
Diagnosis for each of these types of leishmaniasis involves taking a scraping from a lesion, preparing it in a laboratory, and examining it under a microscope to demonstrate the causative protozoan. Other methods that have been used include culturing a sample piece of tissue in a laboratory to allow the protozoa to multiply for easier microscopic identification; injecting a mouse or hamster with a solution made of scrapings from a patient's lesion to see if the animal develops a leishmaniasis-like disease; and demonstrating the presence in macrophages of the characteristic-appearing protozoan, called Leishman-Donovan bodies.
In some forms of leishmaniasis, a skin test (similar to that given for TB) may be used. In this test, a solution containing a small bit of the protozoan antigen (cell marker that causes the human immune system to react) is injected or scratched into a patient's skin. In a positive reaction, cells from the immune system will race to this spot, causing a characteristic skin lesion. Not all forms of leishmaniasis cause a positive skin test, however.
The treatment of choice for all forms of leishmaniasis is a type of drug containing the element antimony. These include sodium sitogluconate, and meglumin antimonate. When these types of drugs do not work, other medications with anti-protozoal activity are utilized, including amphotericin B, pentamidine, flagyl, and allopurinol. In 2004, it was reported that the world's first non-profit drug company was seeking approval in India for a drug to cure visceral leishmaniasis. An estimated 200,000 people die annually from the disease in that country. The company, called OneWorld Health, hoped to offer the drug called paromomycin for a day for a three-week treatment course.
The prognosis for leishmaniasis is quite variable, and depends on the specific strain of infecting protozoan, as well as the individual patient's immune system response to infection. Localized cutaneous leishmaniasis may require no treatment. Although it may take many months, these lesions usually heal themselves completely. Only rarely do these lesions fail to heal and become more destructive.
Disseminated cutaneous leishmaniasis may smolder on for years without treatment, ultimately causing death when the large, open lesions become infected with bacteria.
Mucocutaneous leishmaniasis is often relatively resistant to treatment. Untreated visceral leishmaniasis has a 90% death rate, but only a 10% death rate with treatment.
Prevention involves protecting against sandfly bites. Insect repellents used around homes, on clothing, on skin, and on bednets (to protect people while sleeping) are effective measures.
Reducing the population of sandflies is also an important preventive measure. In areas where leishmaniasis is very common, recommendations include clearing the land of trees and brush for at least 984 ft (300 m) around all villages, and regularly spraying the area with insecticides. Because rodents often carry the protozoan that causes leishmaniasis, careful rodent control should be practiced. Dogs, which also carry the protozoan, can be given a simple blood test.
MacReady, Norma. "Leishmaniasis Hits Military Hot Spots." Internal Medicine News June 15, 2004: 58.
"Seeking First-time Approval." Chemist & Druggist May 8, 2004: 12.
"Treatment of Cutaneous Leishmaniasis Among Travelers Reviewed." Vaccine Weekly April 28, 2004: 58.
Host— The organism (such as a monkey or human) in which another organism (such as a virus or bacteria) is living.
Larynx— The part of the airway lying between the pharynx and the trachea.
Leishman-Donovan body— A body of a (trypanosomatid) protozoa at a particular and characteristic stage in its life cycle; the infectious (trypanosomatid) protozoa can cause leishmaniasis, and is relatively easy to identify at that stage.
Lesion— A disruption of the normal structure and function of a tissue by some disease process.
Macrophage— A cell of the immune system that engulfs and digests foreign invaders such as bacteria and viruses in an attempt to stop them from causing disease within the body.
Protozoa— A group of organisms which are the smallest members of the animal kingdom, consisting of a single cell.
Ulceration— An area of pitting and irritation.
Vector— A carrier organism (such as a fly or mosquito) that to delivers a virus (or other agent of infection) to a host.
Leishmaniasis (LEASH-ma-NIGH-a-sis) is a parasitic disease caused by a protozoan of the genus Leishmania and spread by the bite of a sand fly. The disease is endemic in 88 countries worldwide and about 2 million cases occur each year.
Leishmaniasis usually affects people living in tropical and subtropical regions frequently exposed to the sand fly. Signs and symptoms vary depending on the form of infection, but mild cases present with skin sores on the face, arms, and legs that eventually heal with treatment. The more severe cases of visceral leishmaniasis affect organs such as the spleen and liver and may be fatal if untreated.
Treatment with drugs is usually quite effective if administered prior to significant immune damage, but, in the majority of cases, severe scarring is often unavoidable. There is no vaccine or drug available for the prevention of leishmaniasis, however, minimizing contact with the sand fly vector significantly reduces the risk of infection.
One of the first clinical descriptions of leishmaniasis appeared in 1756, although the disease has been referenced as far back as the first century AD. The name leishmaniasis was given to the disease in 1901 when a Scottish doctor identified the causative organism as being the protozoa Leishmania.
Leishmaniasis has several forms, each with varying symptomatic presentation and clinical severity. Cutaneous leishmaniasis is the most common form. It is characterized by skin sores over the face, arms, and body, which may be painful or painless. Glands near the sores may be swollen. The sores usually develop within a few weeks of infection, and may leave severe scarring.
Visceral leishmaniasis is the most serious form of the disease. It affects organs, such as the liver and spleen, and presents symptoms such as persistent chronic fever, fatigue, scaly/gray skin, weight loss, anemia, and enlarged spleen or liver. In developing countries, this form of leishmaniasis may have a 100% fatality rate within two years if untreated.
Mucocutaneous leishmaniasis often occurs if the cutaneous (skin) form is untreated. In this form of the disease, the skin sores spread and may cause partial or total destruction of mucous membranes found in the nose, mouth, and throat. These mucosal sores often leave patients with severe facial deformities.
Leishmaniasis is transmitted by the bite of about 30 species of the phlebotomine sand fly, which are most active between dusk and dawn. Only female sand flies are capable of spreading the disease after infecting themselves by ingesting host blood containing the protozoa. Hosts of the parasite include dogs, foxes, jackals, and rodents. After 4 to 25 days within the sand fly, the protozoon transforms and completes its lifecycle upon being re-injected into a new host. Transmission is possible between humans through blood transfusions or the use of contaminated needles.
There are an estimated twelve million cases of leishmaniasis globally. It is found in 88 countries around the world and is most common in tropical and subtropical regions of Africa, South America, and Asia. Within these regions, over 350 million people are at risk of contracting the disease. Each year there are over 1.5 million new cases of cutaneous leishmaniasis and more than 500,000 cases of visceral leishmaniasis.
The geographic distribution of the disease is limited by the suitability of habitat for the sand fly, their ability to remove blood from the host and transfer it to another, and the role the flies play in completing the life cycle of the infecting protozoa. Over 90% of global cases of visceral leishmaniasis are found in India, Bangladesh, Nepal, Sudan, and Brazil. These regions offer tropical and subtropical climates and provide the perfect conditions for phlebotomine sand flies to live, breed, and successfully transmit the disease.
People at greatest risk of contracting leishmaniasis are those living, working, or visiting those areas where sand flies are found, and there is a notably higher incidence of infection in rural areas than in urban areas. There is no indication of transmission between pregnant women and unborn children, although contaminated blood or needles can spread of disease.
Leishmaniasis is rarely occurs in the United States, but some cases of skin sores arising from cutaneous leishmaniasis have been reported in rural areas of southern Texas. As of 2007, no cases of visceral leishmaniasis have been reported in the United States.
Leishmaniasis is caused by parasitic infection and treatment with drugs is usually effective if applied prior to immune system damage. In some parts of the world, the parasite has become resistant to traditional drug treatments and, as a result, new drugs must be constantly developed to maintain effectiveness. In some cases of drug resistant visceral leishmaniasis, it may be necessary to remove the patient's spleen.
The sores caused by cutaneous leishmaniasis may lead to unsightly scarring if not treated, and severe cases of mucocutaneous leishmaniasis may require reconstructive surgery to repair damage to facial tissues. Because the disease is parasitic, there may be reactivation of infection after the initial signs and symptoms disappear. Previous infection does not provide any form of immunity against future infection.
There is no vaccine or drug available to prevent leishmaniasis, but transmission may be avoided by limiting exposure to the sand fly vector that carries the disease. Sand flies are most active from dusk to dawn, and it is best to limit outdoor activities during these times in areas where the disease occurs. Protective clothing, such as long-sleeved shirts and long pants, can reduce the amount of exposed skin and prevent fly bites. If the sleeping area is not well screened or air-conditioned, a bed net that has been soaked in or sprayed with insecticide should be used. Dogs and rodents should be kept away from sleeping areas. When exposure to sand flies is unavoidable, it is beneficial to use a strong insect repellent and spray sleeping areas with insecticides, if possible.
In addition to undertaking individual prevention, governments may implement public health measures. While avoidance of the vector is helpful in preventing individual cases, a reduction in animals harboring infection will have a greater impact on preventing the spread of disease. Public awareness is important to ensure that communities are working towards the same goal and following similar guidelines to reduce sand fly populations and animal reservoirs.
WORDS TO KNOW
CUTANEOUS: Pertaining to the skin.
PROTOZOA: Single-celled animal-like microscopic organisms that live by taking in food rather than making it by photosynthesis and must live in the presence of water. (Singular: protozoan.) Protozoa are a diverse group of singlecelled organisms, with more than 50,000 different types represented. The vast majority are microscopic, many measuring less than measuring less than 5 one thousandth of an inch(0.005 millimeters), but some, such as the freshwater Spirostomun, may reach 0.17 inches (3 millimeters) in length, large enough to enable it to be seen with the naked eye.
VECTOR: Any agent, living or otherwise, that carries and transmits parasites and diseases. Also, an organism or chemical used to transport a gene into a new host cell.
VISCERAL: Visceral means pertaining to the viscera. The viscera are the large organs contained in the main cavities of the body, especially the thorax and abdomen; for example, the lungs, stomach, intestines, kidneys, or liver.
The impacts of a widespread condition such as leishmaniasis are evident at the community level and also across countries and continents. One of the significant physical effects of leishmaniasis infection is the severe scarring caused by the sores that develop on the face, legs, and arms. In some communities affected by the disease, social prejudices exist towards people with these unattractive scars and in some situations people with disabling disfigurations become social outcasts. This may cause division within communities and may eventually lead to social breakdown.
On a larger scale, human-caused environmental changes are having an impact on natural habitats and as a result are increasing the risk of human exposure to the sand fly vector. Activities, such as dam building, mining, deforestation, irrigation, and conversion of land to cultivation, permanently alter the conditions under which the vectors exist naturally and create new opportunities for vector contact. Although it was previously a disease associated with poverty stricken, rural areas, leishmaniasis has successfully adapted to the urban environment. The movement of large groups from rural to urban areas, in addition to the worldwide urbanization, is also adding to this effect.
When war breaks out in areas where leishmaniasis is endemic, the disease can have an international impact. The deployment of foreign troops to these regions places those soldiers at increased risk of contracting the disease, despite extensive measures taken to prevent sand fly contact. The deployment of United States troops to Iraq in 2003 and 2004 resulted in 237 cases of leishmaniasis out of a force of about 200,000 soldiers. Soldiers fighting in Iraq have dubbed the disease “Baghdad Boil.” When these foreign soldiers return to their home countries, they potentially create a portal of entry for the parasite to move into previously unaffected zones, thus aiding the worldwide spread of leishmaniasis. While these countries generally are able to implement stringent preventative measures among their troops to protect them from infection, there remains a potential risk of spreading the disease to new areas.
Co-infection of HIV and leishmaniasis also is common. HIV infection increases the risk of leishmaniasis infection, while leishmaniasis causes an increase in the progression of HIV to AIDS. In Europe, the primary way in which leishmaniasis is transmitted is through sharing of intravenous needles. The World Health Organization considers co-infection of HIV and leishmaniasis to be a significant concern, since it could lead to spread of the disease into previously non-endemic areas. In 1998, the World Health Organization and UNAID implemented the Programme for the Surveillance and Control of Leishmaniasis to monitor leishmaniasis/HIV co-infection, improve response capability, and ensure that epidemics are detected and contained.
IN CONTEXT: PERSONAL RESPONSIBILITY AND PROTECTION
The Centers for Disease Control and Prevention (CDC), Division of Parasitic Diseases recommends that the “best way for travelers to prevent leishmaniasis is by protecting themselves from sand fly bites.” and that to decrease their risk of being bitten, travelers should:
- Stay in well-screened or air-conditioned areas as much as possible. Avoid outdoor activities, especially from dusk to dawn, when sand flies are the most active.
- When outside, wear long-sleeved shirts, long pants, and socks. Tuck your shirt into your pants.
- Apply insect repellent on uncovered skin and under the ends of sleeves and pant legs. Follow the instructions on the label of the repellent. The most effective repellents are those that contain the chemical DEET (N,N-diethylmetatoluamide). The concentration of DEET varies among repellents. Repellents with DEET concentrations of 30-35% are quite effective, and the effect should last about 4 hours. Lower concentrations should be used for children (no more than 10% DEET). Repellents with DEET should be used sparingly on children from 2 to 6 years old and not at all on children less than 2 years old.
- Spray clothing with permethrin-containing insecticides. The insecticide should be reapplied after every five washings.
- Spray living and sleeping areas with an insecticide to kill insects.
- If you are not sleeping in an area that is well screened or air-conditioned, use a bed net and tuck it under your mattress. If possible, use a bed net that has been soaked in or sprayed with permethrin. The permethrin will be effective for several months if the bed net is not washed. Keep in mind that sand flies are much smaller than mosquitoes and therefore can get through smaller holes. Fine-mesh netting (at least 18 holes to the inch; some sources say even finer) is needed for an effective barrier against sand flies. This is particularly important if the bed net has not been treated with permethrin. However, it may be uncomfortable to sleep under such a closely woven bed net when it is hot.
- NOTE: Bed nets, repellents containing DEET, and permethrin should be purchased before traveling and can be found in hardware, camping, and military surplus stores.
SOURCE: Centers for Disease Control and Prevention (CDC)
See AlsoAIDS (Acquired Immunodeficiency Syndrome); Blood Supply and Infectious Disease; Emerging Infectious Diseases; HIV; Host and Vector; Parasitic Diseases; War and Infectious Disease; World Health Organization (WHO).
Mandell, G.L., J.E. Bennett, and R. Dolin. Principles and Practice of Infectious Diseases. Vol. 2. Philadelphia: Elsevier, 2005.
American Academy of Dermatology. “Researchers Urge Soldiers and Civilians Returning from Iraq to Be Aware of ‘Baghdad Boil.”’ June 30, 2005. <http://www.aad.org/aad/Newsroom/Researchers+Urge+Soldiers+and+civilians+returning.htm> (accessed February 26, 2007).
Centers for Disease Control. “Leishmania Infection.” April 1, 2004. <http://www.cdc.gov/ncidod/dpd/parasites/leishmania/default.htm> (accessed February 26, 2007).
Deployment Health Clinical Center. “Leishmaniasis.” June 21, 2004. <http://www.pdhealth.mil/leish.asp> (accessed February 26, 2007).
World Health Organization. “Leishmaniasis: Background Information.” 2007. <http://www.who.int/leishmaniasis/en/> (accessed February 26, 2007).
World Health Organization. “Surveillance and Control of Leishmaniasis.” 2007. <http://www.who.int/leishmaniasis/surveillance/en/> (accessed February 26, 2007).
Leishmaniasis (leesh-muh-NYE-uh-sis) is a parasitic infection spread by sand flies. It causes symptoms ranging from sores on the skin to damage to internal organs.
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The disease occurs when a person becomes infected with any of several types of Leishmania parasites*. They spread to people through the bite of female sand flies and can cause different forms of illness, all of which are called leishmaniasis. Cutaneous (kyoo-TAY-nee-us) leishmaniasis affects the skin; mucocutaneous (myoo-ko-kyoo-TAY-nee-us) leishmaniasis attacks the mucous membranes* in the mouth, nose, and throat; and visceral (VIH-suh-rul) leishmaniasis (also known as systemic leishmaniasis or kala azar) damages internal organs, such as the liver* and spleen*.
- (PAIR-uh-sites) are organisms such as protozoa (one-celled animals), worms, or insects that must live on or inside a human or other organism to survive. An animal or plant harboring a parasite is called its host. Parasites live at the expense of the host and may cause illness.
- *mucous membranes
- are the moist linings of the mouth, nose, eyes, and throat.
- is a large organ located beneath the ribs on the right side of the body. The liver performs numerous digestive and chemical functions essential for health.
- is an organ in the upper left part of the abdomen that stores and filters blood. As part of the immune system, the spleen also plays a role in fighting infection.
Cutaneous and mucocutaneous infections can lead to severe scarring and permanent disfigurement. In patients with a mucocutaneous infection, the disease can destroy soft tissue in the mouth and nose, drastically deforming the face. The visceral form of the disease is considered the most dangerous. It can grow worse over time and is usually fatal if not treated. Leishmaniasis damages the immune system so that it cannot fight off infections; these infections are generally the cause of death, not leishmaniasis itself. In some countries, visceral disease has been found with increasing frequency in people who also have human immunodeficiency virus* infection.
- *human immunodeficiency
- (HYOO-mun ih-myoo-no-dih-FIHshen-see) virus , or HIV, is the virus that causes AIDS (acquired immunodeficiency syndrome).
The infection is most common in tropical and subtropical regions, such as countries in South America, Africa, and Asia, and the number of areas where it occurs continues to grow. The U.S. Centers for Disease Control and Prevention (CDC) estimates that one and a half million people around the world contract cutaneous leishmaniasis each year and half a million people experience the more serious visceral form of the disease. Ninety percent of the visceral cases are found in just five countries: India, Nepal, Bangladesh, Sudan, and Brazil. Leishmaniasis is exceptionally rare in the United States, although a few cutaneous cases have been diagnosed in rural southern Texas.
People cannot get leishmaniasis directly from other people. Instead, the disease spreads through the bite of blood-sucking sand flies. A fly bites an infected animal or person and takes in the parasite with its meal of blood. The Leishmania parasites reproduce in the fly, which can spread them when it bites another person. Sand flies are quite small—about a third of the size of a mosquito—and fly silently, so people often do not even know the flies are nearby. Less often, the disease can be transmitted through contaminated blood in a transfusion*, by sharing or reusing needles for injecting drugs, or from a mother to her baby during pregnancy or birth.
- (trans-FYOO-zhun) is a procedure in which blood or certain parts of blood, such as specific cells, are given to a person who needs them because of illness or blood loss.
Cutaneous leishmaniasis is marked by sores that often look like volcanoes: they have a central pit and a raised rim. They can be painful or painless and may be covered by scabs. The sores tend to appear on the face, arms, and legs, and some people have as many as 200 of them. Patients with cutaneous leishmaniasis also may have swollen lymph nodes* near the sores. In mucocutaneous cases, the lesions appear in the mouth, nose, and throat and gradually destroy the soft tissues in those areas.
- (LIMF) nodes are small, bean-shaped masses of tissue that contain immune system cells that fight harmful microorganisms. Lymph nodes may swell during infections.
The visceral form of the disease can cause lack of appetite, serious weight loss, fever (which can last from 2 weeks to 2 months), and increasing weakness. It also can lead to an enlarged spleen and liver and sometimes swollen lymph nodes. Blood tests may show that the patient has low levels of white blood cells, red blood cells, or platelets*. As the disease progresses, the skin can become dark and dry—a symptom that gave the disease the name kala azar (meaning “black fever”). In children, visceral leishmaniasis often begins suddenly, with fever, diarrhea, and cough.
- (PLATE-lets) are tiny, disk-shaped particles within the blood that play an important role in clotting.
Cutaneous leishmaniasis affects the skin, causing sores that may look like volcanoes: they have a central pit and a raised rim. The disease can destroy tissue and lead to permanent scarring. AP/Wide World Photos
A key to making the diagnosis is learning whether the patient has traveled to a country where leishmaniasis occurs. During the physical examination, the doctor also checks the patient’s body for the types of sores seen with the infection. The doctor may take blood samples and tissue samples from any sores that are found. These samples will be cultured*, examined for signs of the parasite, or tested for antibodies* to the parasite. For suspected cases of visceral infection, biopsies* of the abnormal tissue may be done.
- (KUL-churd) means subjected to a test in which a sample of fluid or tissue from the body is placed in a dish containing material that supports the growth of certain organisms. Over time, ranging from hours to weeks, the organisms will grow and can be identified.
- (AN-tih-bah-deez) are protein molecules produced by the body’s immune system to help fight specific infections caused by microorganisms, such as bacteria and viruses.
- (BI-op-seez) are tests in which a small sample of skin or other body tissue is removed and examined for signs of disease.
Doctors treat the infection with prescription medications; many of these medicines contain antimony*. Cutaneous cases usually can be treated at home, but visceral disease may require hospitalization and supportive care, such as intravenous* fluids. Patients who have severe disfigurement from cutaneous, and especially mucocutaneous, leishmaniasis often need reconstructive surgery to regain a normal appearance. However, such extensive (and expensive) treatment is not available to vast numbers of people in developing countries who contract this disease.
- (AN-tih-mo-nee) is an element that has properties of both metals and nonmetals and can kill or inhibit the growth of certain bacteria.
- (in-tra-VEE-nus) means within or through a vein. For example, medications, fluid, or other substances can be given through a needle or soft tube inserted through the skin’s surface directly into a vein.
Although some cases of cutaneous leishmaniasis clear up on their own, most cases of mucocutaneous and visceral infection will not get better without treatment. Left untreated, visceral disease typically leads to death within 2 years. Cutaneous cases may take several months to heal, even with treatment, and may return after the treatment has been completed.
The cutaneous and mucocutaneous forms of leishmaniasis often cause widespread scarring. In mucocutaneous cases, destruction of tissue in the mouth and nose can lead to facial deformity. Visceral disease can damage the immune system to the point that it is unable to fight off other infections. Some patients may need to have the spleen removed if it is trapping and destroying too many of the person’s blood cells, and advanced cases of disease often result in death.
Avoiding sand fly bites is the best way to limit the spread of leishmaniasis. In areas where the flies live, people are advised to stay inside from dusk until dawn, when the insects are most active. Wearing long-sleeved shirts, long pants, and socks and tucking pants into socks can reduce the amount of bare skin that is vulnerable to fly bites. Using insect repellent, staying in screened-in or air-conditioned areas, sleeping under mosquito netting, and spraying living areas with an insecticide to kill flies also can help lessen the risk of being bitten.
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Leishmaniasis is caused by protozoan parasites of the genus Leishmania that are spread by the bite of female phlebotomine sand flies of the genus Phlebotomus in the Old World and Lutzomyia in the New World.
Approximately 350 million people in eighty-eight countries are thought to be at risk for leishmania infection. The true number of infected individuals is unknown, as it is not considered a reportable disease in many of the affected countries. The World Health Organization (WHO) estimates that twelve million people are infected and that there are between 1.5 and 2 million new cases each year.
Leishmania infection occurs in a variety of mammalian hosts, including the domestic dog, rodents, and sloths. When a sand fly, a night-biting insect, takes a blood meal from an infected mammal, it will ingest leishmania parasites, called amastigotes, along with the blood. Over seven days leishmania multiply in the flight muscles and develop into infective, flagellated promastigote forms. When the sand fly next takes a blood meal, these promastigotes are injected into a new mammalian host, where they transform back into the amastigote form and begin to divide. Leishmania species are obligate intracellular parasites that infect and replicate in mononuclear phagocytic cells such as macrophages. Infection can also occur via blood transfusion, shared intravenous needles, or, rarely, direct contact with skin lesions. The incubation period in humans is usually from three to eight months, but can be as short as two weeks or as long as several decades.
The spectrum of clinical manifestations caused by leishmania is divided into three broad categories: cutaneous, mucocutaneous, and visceral leishmaniasis. Cutaneous leishmaniasis is found worldwide and results in skin lesions ranging from a single, discrete, self-healing ulcer to diffuse progressive induration. The spectrum of disease is determined by the species of the parasite and the ability of the host to mount a cell-mediated response. A hyper-immune response causes destructive changes such as those seen in mucocutaneous disease, and a hypo-immune response results in visceral and diffuse cutaneous leishmaniasis. In Old World cutaneous leishmaniasis, the usual causative species are L. major, L. tropica, or L. aethiopica. In the Americas, cutaneous lesions are usually the result of infection with L. braziliensis, L. mexicana, L. amazonensis, or L. panamensis.
In mucocutaneous leishmaniasis (also called espundia), the infection causes destruction of mucous membranes of the nose, mouth, and throat. This form of leishmania is found almost exclusively in the Americas and is seen predominantly in a subset of patients infected with L. braziliensis. Diffuse cutaneous leishmaniasisis, caused by L. aethiopica, is characterized by induration of skin without ulceration.
Visceral leishmaniasis, or kala-azar, is the most severe form of infection with parasites disseminated throughout the reticuloendothelial system. Patients experience fevers, night sweats, and weight loss. The spleen and liver become enlarged, sometimes massively. Blood work reveals anemia, leucopenia, thrombocytopenia, and a marked increase in gamma-globulin levels. If untreated, visceral leishmaniasis is virtually always fatal.
It used to be thought that each species of leishmania resulted in a particular clinical syndrome. However, it is now being recognized that there is considerable overlap in the clinical presentation of each species. Most people bitten by leishmania -infected sand flies will never manifest any evidence of the infection. After recovery from leishmaniasis, a person is immune for life from reinfection by that strain.
Conditions that impair cell-mediated immunity can result in more severe, disseminated leishmanial infections. This has been seen in organ transplant recipients and, most importantly, in persons infected with HIV (human immunodeficiency virus), in whom visceral leishmaniasis has become a frequent opportunistic infection in endemic regions.
Diagnosis is made by microscopic identification of the parasite in tissue samples, by growing the organisms in culture, or by polymerase chain reaction (PCR) of tissue. PCR is a test that will identify even trace amounts of leishmanial DNA in tissue. Samples are taken from the edge or base of a skin ulcer in cutaneous disease. Bone marrow or splenic aspirates are the best tissue samples in cases of visceral disease. Testing for serum antibodies against leishmania parasites may be helpful.
Cutaneous lesions often heal spontaneously. Treatment is undertaken when the lesions are in cosmetically disfiguring areas, when the infection is widespread, and for certain leishmania spp. that are less likely to heal (e.g., L. brasiliensis ). Pentavalent antimony (sodium stibogluconate, Pentostam), given either systemically or intralesionally, is the drug of choice for cutaneous lesions. Mucocutaneous and visceral leishmaniasis always require intravenous treatment with a pentavalent antimonial. Other effective medications for some species include amphotericin B (HIV-infected individuals) and pentamidine (for L. panamensis ).
As there are many animal reservoirs of infection, and as elimination of sand flies is unlikely, control of leishmaniasis depends on avoiding exposure to sand flies. This involves a combination of insect repellent, fine-meshed bed nets, and protective clothing, and avoiding areas known to harbor sand flies.
(see also: Communicable Disease Control; Tropical Infectious Diseases )
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