PARASITES

        A parasite is an organism that lives on or in humans or animals. Infection is the process whereby a parasite establishes itself and starts to grow. Parasites which inflict damage on humans and animals are known as pathogens. Pathogenic organisms that can be transmitted by water include certain protozoa, bacteria and viruses. In general, harmful organisms transmitted by water grow in the intestinal tract and exit the body through the feces. Fecal contamination of water and / or food supplies can lead to widespread infection, hence proper treatment of water is a very important public health measure.

        The following section provides information about several diseases caused by protozoa. Protozoa are unicellular microorganisms, generally slightly larger than bacteria (i.e. 4 to 25 µm) with a more complex cell structure. They are usually transmitted in the cyst form - a dormant, protected state -- which can be resistant to disinfection. Disinfection alone, therefore, may be inadequate for removing all of the cysts present in water supplies. The protozoans addressed in this section include:

- Cryptosporidium
- Giardia
- Microsporidium
- Toxoplasma
- Cyclospora
- Others

        Cryptosporidium. What is Cryptosporidium? Diarrhea, stomach cramps, vomiting, upset stomach, and a slight fever are all symptoms of cryptosporidiosis, as well as other intestinal diseases.
        Cryptosporidium (krip­toe­spo­rid­I­um, called crypto for short) is a one­celled organism that can cause a diarrheal disease known as cryptosporidiosis. Crypto can live in the intestines of humans, farm animals, wild animals and household pets. Crypto is too small to be seen by the naked eye. It can live outside the body for a long time in water and on surfaces, but cannot multiply unless it is in the intestines. If a person or animal swallows crypto, they can get sick and have watery diarrhea, stomach cramps, an upset stomach or a slight fever.

        Where is Crypto Found? Both human and animal feces (that is, bowel movements) can contain crypto. Crypto has found its way into most lakes, rivers and streams (surface waters) in all parts of the United States. It may also sometimes be found in wells or springs. San Francisco's pristine water sources have very little crypto.

        How Can Crypto Affect My Health? If you have severe diarrhea for more than 4 days, you should contact your doctor. Two to ten days after you swallow crypto, you may get diarrhea which might be watery, and you may also get stomach cramps, vomiting, upset stomach or a slight fever. If you are healthy with a normal immune system, your symptoms normally will last for 2 weeks or less, although you may feel better and then worse. Some people with cryptosporidiosis may not get sick, but they can still pass the disease to others. After you are infected you can pass crypto in your feces for up to 2 months, and maybe give the disease to other people. If you have a severely weakened immune system you may have cryptosporidiosis for a longer time. You should talk with your health care provider to learn how to avoid cryptosporidiosis. Examples of people with weakened immune systems include HIV/AIDS patients and cancer and transplant patients.

        How Would I Know If I Have Cryptosporidiosis? If you have severe diarrhea for more than 4 days, you should ask your doctor to have your feces tested for crypto. If you have a very young child with severe diarrhea, you should go even sooner. Only a test of your feces can show whether or not you have cryptosporidiosis. Most people will recover on their own.

        What Is the Treatment for Cryptosporidiosis? There is no drug yet that can cure cryptosporidiosis. Most people will recover on their own. You should drink plenty of fluids if you have diarrhea. However, if you have a weakened immune system, you should seek medical advice.
        How Is Cryptosporidiosis Spread? Even a tiny amount of feces can cause disease. You can become infected only by swallowing crypto. Even a small amount may cause disease. Some sources of disease are:

- Drinking water with crypto in it.
- Contact with the feces of infected persons (e.g., changing diapers, sexual practices).
- Contact with the feces of infected animals (e.g., pets and farm animals).
- Hand­to­mouth transfer of crypto from surfaces or objects that may have gotten infected feces on them (e.g., diaper changing tables, garden soil, bathrooms).
- Swallowing water with crypto in it while swimming.
- Eating raw or undercooked food that has crypto in it.

        How Can I Protect Myself? Washing your hands is important for protecting against cryptosporidiosis.

        1. Know the source of your water: (a) do not drink or swallow water directly from rivers, lakes, streams, pools or spas, (b) if you travel outside the United States you may want to avoid drinking water that has not been boiled or filtered for crypto. If you are immunocompromised you should consider additional protective steps.
        2. Always wash your hands with soap and water any time you might have touched human or animal feces, changed diapers, cleaned up feces, or gardened. Always wash your hands before eating.
        3. Avoid sex that may involve contact with feces.
        4. If you are immunocompromised you should consider additional protective steps such as boiling your drinking water for one minute, which will kill any crypto in it. You could also use a water filter certified by NSF International to remove cysts or drink only bottled water certified by NSF or drink only canned and bottled bubbly drinks.

        Giardia. Diarrhea, stomach cramps, and vomiting are all symptoms of giardiasis and other intestinal diseases.

        What is Giardia? Giardia is a microscopic one­celled organism that can cause a diarrheal disease known as giardiasis. Giardia can live in the intestines of humans, farm animals, wild animals and household pets. It can live outside the body for a long time in water and on surfaces, but cannot multiply unless it is in the intestines. If a person or animal swallows Giardia, they can get sick and have a smelly diarrhea, stomach cramps, an upset stomach or nausea.

        Where is Giardia Found? If you have severe diarrhea for more than 4 days, you should contact your doctor. Both human and animal feces (that is, bowel movements) can contain Giardia. Giardia has found its way into most lakes, rivers and streams (surface waters) in all parts of the United States. It may also sometimes be found in wells or springs. San Francisco's pristine water sources have very little Giardia.

        How Would I Know If I Have Giardiasis? Seven to twenty-one days after you swallow Giardia symptoms appear. If you have severe diarrhea for more than 4 days, you should ask your doctor to have your feces tested for Giardia. If you have a very young child with severe diarrhea, you should go even sooner. Only a test of your feces can show whether or not you have Giardiasis.
        What Is the Treatment for Giardiasis? Many people will recover on their own. Many people will recover on their own. You should drink plenty of fluids if you have diarrhea. A doctor may prescribe anti-parasitic drugs.

        How Is Giardiasis Spread? You can become infected only by swallowing Giardia. Even a small amount may cause disease. Some sources of disease are:

- Drinking water with Giardia in it.
- Contact with the feces of infected persons (e.g., changing diapers, sexual practices). Even a tiny amount of feces can cause disease.
- Contact with the feces of infected animals (e.g., pets and farm animals).
- Hand­to­mouth transfer of Giardia from surfaces or objects that may have gotten infected feces on them (e.g., diaper changing tables, garden soil, bathrooms).
- Swallowing water with Giardia in it while swimming.
- Eating raw or undercooked food that has Giardia in it.

        How Can I Protect Myself? Washing your hands is important for protecting against Giardiasis.

1. Know the source of your water: (a) do not drink or swallow water directly from rivers, lakes, streams, pools or spas, (b) if you travel outside the United States you may want to avoid drinking water that has not been boiled or filtered for crypto. If you are immunocompromised you should consider additional protective steps.
2. Always wash your hands with soap and water any time you might have touched human or animal feces, changed diapers, cleaned up feces, or gardened. Always wash your hands before eating.
3. Avoid sex that may involve contact with feces.
4. If you are immunocompromised you should consider additional protective steps such as boiling your drinking water for one minute, which will kill any Giardia in it. You could also use a water filter certified by NSF International to remove cysts or drink only bottled water certified by NSF or drink only canned and bottled bubbly drinks.

        Microsporidia. What is Microsporidia? Microsporidia, similar to Cryptosporidium and Giardia, are protozoans. Fecal spores are generally 1 to 3 microns in diameter. It is known to infect fish, birds, and some mammals. Only recently has Microsporidia been recognized to cause disease in humans and has increased in its public health significance. While microsporidiosis is more common in people with weakened immune systems (i.e., immunocompromised), cases do occur among those with normal immune systems. Some Microsporidia have the potential to be waterborne because they are released in feces and urine. The most frequent cause of human infection is Enterocytozoan bieneusi. Others include Encephalitozoon hellem, Encephalitozoon cuniculi, Encephalitozoon intestinalis, and Nosema corneum.

        How can Microsporidiosis Affect My Health? In some cases, the person infected with Microsporidia will not demonstrate symptoms. In other cases, infections can result in intestinal symptoms (e.g. diarrhea) and respiratory symptoms (e.g. bronchitis, pneumonia, and sinusitis). Microsporidia may also be a frequent cause of otherwise unexplained cholangitis in HIV-infected patients. Microsporidiosis can be diagnosed through examination of stool, urine, or nasal washings.
        What is the Treatment for Microsporidiosis? Currently, there is no standard treatment for microsporidiosis. Albendazole, metronidazole, and thalidomide have all been used to treat microsporidiosis with limited success.

        How is Microsporidiosis Spread? Microsporidia enter individuals via ingestion or inhalation. Resistant spores are formed within the host and are secreted from the body in feces and urine, and possibly through mucous secretion although this has not been documented. Therefore, microsporidiosis is predisposed to spread via fecal-oral, urine-oral, and waterborne transmission. Microsporidia spores have been shown to survive prolonged periods of time in water (up to 4 months) and have been detected in surface water. The levels of Microsporidia spores found in raw sewage are comparable to that of Cryptosporidium and Giardia.

        How Can I Protect Myself?
1. Know the source of your water: (a) do not drink or swallow water directly from rivers, lakes, streams, pools, or spas, (b) if you travel outside the United States you may want to avoid drinking water that has not been boiled or filtered for Microsporidia.
2. Always wash your hands with soap and water any time you might have touched human or animal feces, changed diapers, cleaned up feces, or gardened. Always wash your hands before eating.
3. Avoid sex that may involve contact with feces.
4. If you are immunocompromised you should consider additional protective steps such as boiling your drinking water for one minute, which will kill any Microsporidia in it. You could also use a water filter certified by NSF International to remove cysts or drink only bottled water certified by NSF or drink only canned and bottled bubbly drinks.

        Toxoplasma. What is Toxoplasma? Toxoplasma gondii is a protozoan, 10 to 12 microns in diameter, that causes latent infection (termed Toxoplasmosis) of the central nervous system. It is also the most common opportunistic pathogen of the brain in AIDS patients. Toxoplasma infection primarily occurs due to the ingestion of raw or undercooked meat or contact with cat excrement. However, there have been two reported cases of Toxoplasma being transmitted by contaminated water.

        How can Toxoplasmosis Affect My Health? The most common symptoms of toxoplasmosis are headaches, confusion, fever, and inflammation of the brain. These symptoms appear 5 to 23 days after exposure. Toxoplasmosis may also involve the heart, lung, pancreas, and testis. People infected with the acute form of the disease may experience symptoms similar to mononucleosis. Infection during primary stages of pregnancy may lead to brain damage or even death of the fetus. If the infection occurs in the later stages of pregnancy, it may result in mild or subclinical fetal disease with delayed manifestations. Toxoplasmosis is a common infection which does not produce symptoms in most cases. However, individuals who are HIV-infected have a much greater risk of developing cerebral toxoplasmosis.

        What is the Treatment for Toxoplasmosis? Diagnosis of toxoplasmosis is determined by reviewing a CAT (Computerized Axial Tomography) scan, MRI (Magnetic Resonance Imaging), and blood work. The standard treatment method for people with toxoplasmic encephalitis is a combination of pyrimethamine and sulfadiazine. Other methods of treatment are currently being considered due to the adverse reactions that occur with this regimen.

        How is Toxoplasmosis Spread? Cats and other felines acquire the infection from consuming infected mammals or birds. The parasite then reproduces in the intestinal tract and is excreted from their system via feces. The infective parasite is capable of remaining in water or moist soil for prolonged periods of time. Humans ingest the parasite and it develops into tissue cysts. Intermediate hosts that may carry the infective tissue cysts in their muscle or brain include: sheep, cattle, goats, rodents, swine, and chickens.

        Toxoplasmosis may therefore be spread from raw or undercooked meat, raw milk, or water/food contaminated with feline feces. Ingestion of Toxoplasma from hands contaminated with feline feces is another route of infection. Toxoplasmosis is not transmitted from person-to-person except in utero (mother-fetus).

        How Can I Protect Myself?

        Avoid eating raw or undercooked meat, or drinking raw milk. Cook meat thoroughly (until color changes). Freezing meat reduces infectivity but does not eliminate it. You should not drink or swallow water directly from rivers, lakes, or streams.

        Always wash your hands with soap and water any time you might have touched feline feces, gardened, touched soil that may have been contaminated by cat feces, and after handling raw meat. Always wash your hands before eating.

        Cat feces and litter should be disposed of daily. Feces should be flushed down the toilet, burned, or deeply buried. Litter pans should be disinfected daily by scalding and dry litter should be disposed of without shaking. Also, wear gloves when handling potentially infective material.

        Guidelines have been published by the United States Public Health Service and Infectious Disease Society of America for the prevention of toxoplasmosis. Toxo seropositive HIV patients with a CD4+ count less 100 cells/mm3 should receive prophylactic treatment. The standard protocol involves Trimethoprim/sulfamethoxazole (TMP/SMX ) although alternatives are available.

        Cyclospora. What is Cyclospora? Cyclospora is a protozoan parasite that was originally thought to be large Cryptosporidium or blue green algae. Infections caused by Cyclospora have been found in both immunodeficient and immunocompetent persons. Before 1996, only three outbreaks of cyclosporiasis infection had been reported in the United States. However, between May 1 and mid-July 1996 almost 1,000 laboratory-confirmed cases were reported to the Centers for Disease Control and Prevention (CDC).

        How can Cyclosporiasis Affect My Health? Common symptoms of cyclosporiasis infections are watery diarrhea, nausea, loss of appetite, abdominal cramping, fatigue, vomiting, and weight loss. Infected persons can also suffer from low-grade fever, but this is less common. The incubation period between infection and the onset of symptoms is approximately one week. Those who are infected may display symptoms for several weeks. Others may experience symptoms that tend to cease and then relapse over a span of months. Cyclosporiasis can be diagnosed through examination of stool samples. However, identification of Cyclospora requires special laboratory tests. Therefore, your physician should specifically request testing for Cyclospora.

        What is the Method of Treatment for Cyclosporiasis? The standard treatment method for cyclosporiasis includes the antibiotics trimethoprim and sulfamethoxazole. Treatment for those individuals who are sulfa-intolerant has not been identified. People infected with Cyclospora should drink plenty of fluids and rest.

        How is Cyclosporiasis Spread? Cyclospora is found in the feces of infected individuals and is transmitted by contaminated water and food. Cyclospora requires days or weeks after being excreted in feces to develop into its infective state. Hence, person-to-person transmission is unlikely. It is unknown whether animals can be infected with Cyclospora. However, raspberries imported from Guatemala have been associated with the outbreak of cyclosporiasis that occurred in 1996. Similarly, strawberries from Mexico caused an outbreak in 1997. Cases have been linked to contaminated water -- both drinking and swimming.

        How Can I Protect Myself?
1. Know the source of your water: (a) do not drink or swallow water directly from rivers, lakes, streams, pools, or spas, (b) if you travel outside the United States you may want to avoid drinking water that has not been boiled or filtered for Cyclospora.
2. Always wash your hands with soap and water any time you might have touched human feces, or changed diapers. Always wash your hands before eating.
3. If you are immunocompromised you should consider additional protective steps such as boiling your drinking water for one minute, which will kill any Cyclospora in it. You could also use a water filter certified by NSF International to remove cysts or drink only bottled water certified by NSF or drink only canned and bottled bubbly drinks.





Source: http://www.ci.sf.ca.us/puc/wqfs/outbreak.htm