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What is Cryptosporidium?
What are the symptoms of cryptosporidiosis?
Source - Cryptosporidium is a protozoan parasite which exists as a round oocyst about 4 to 6 microns in diameter. Oocysts pass through the stomach into the small intestine where it's sporozoites invade the cell lining of the gastrointestinal tract. Symptoms of infection include diarrhea, cramps, nausea, and low grade fever. Treatment - Filtration is the most effective treatment for protozoan cysts. Cartridge POU filters rated at 0.5 micron are designed for this purpose.
What is Cryptosporidium?
Cryptosporidium (crip-toe-spor-ID-ee-um) is a protozoan, a single-celled parasite, that lives in the intestines of animals and people. This microscopic pathogen causes a disease called cryptosporidiosis (crip-toe-spor-id-ee-O-sis).
The dormant (inactive) form of Cryptosporidium, called an oocyst (O-o-sist), is excreted in the feces (stool) of infected humans and animals. The tough-walled oocysts survive under a wide range of environmental conditions.
What are the symptoms of cryptosporidiosis?
The most common symptom of cryptosporidiosis is watery diarrhea. There may also be abdominal cramps, nausea, low-grade fever, dehydration, and weight loss. Symptoms usually develop 4 to 6 days after infection but may appear anytime from 2 to 10 days after infection.
People with healthy immune systems are usually ill with cryptosporidiosis for several days but rarely more than two weeks. Some infected individuals may not even get sick. Some people with cryptosporidiosis seem to recover, then get worse again. Those who are infected may shed oocysts in their stool for months, even after they no longer appear to be ill.
Cryptosporidiosis may cause complications for those with illnesses or conditions such as diabetes, alcoholism, or pregnancy. The effects of prolonged diarrhea and dehydration can be dangerous, especially for the very young, the elderly, and the frail.
Cryptosporidiosis is most severe and long-lasting in immunocompromised individuals (whose immune systems are weak). This disease can be life-threatening for the immunocompromised.
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How is this disease diagnosed and treated?
Cryptosporidiosis cannot be diagnosed by symptoms alone. Watery diarrhea is a symptom of many intestinal diseases caused by bacteria, viruses, or parasites. If Cryptosporidium is the suspected cause of an intestinal illness, the doctor should request a specific diagnostic test.
There is currently no drug that can cure cryptosporidiosis. People with competent immune systems will recover on their own and appear to develop some immunity to subsequent infections. Anti-diarrheal medicines may ease some of the symptoms. Anyone with diarrhea should drink plenty of fluids to prevent dehydration.
How is the pathogen spread?
You can get infected with Cryptosporidium when you put anything in your mouth that has been in contact with feces from an infected animal or person. When large numbers of people get cryptosporidiosis, the source of infection can sometimes be tracked down, but it is impossible to determine the origin of many individual cases of this disease.
Your hands may be contaminated with Cryptosporidium through person-to-person contact, perhaps while changing a child's diaper, caring for someone with diarrhea or engaging in any activity that involves touching areas of the body contaminated with feces. Cryptosporidiosis can be easily spread among people in close social groups such as families, day care centers, and nursing homes. People who work with animals, especially young animals or animals with diarrhea, have greater chance of exposure to the parasite. You may pick up oocysts while handling soil, or any object contaminated with even a small amount of feces.
You can also get cryptosporidiosis by drinking water or eating food that has been contaminated with oocysts. Drinking untreated surface water (such as streams, rivers, and lakes) or swallowing a small amount of water when swimming, even in a chlorinated pool, can cause cryptosporidiosis. The parasite may also be spread in uncooked foods, beverages, or ice prepared with contaminated water. Unwashed fresh fruits or vegetables may carry oocysts if manure was used or animals grazed where the crop was grown.
People who are infected (or whose hands become contaminated) with Cryptosporidium can spread the disease to other people or pets if they are not careful about their hygiene. Frequent handwashing is the single most important thing people can do to avoid spreading cryptosporidiosis and other illnesses. It is especially important to wash thoroughly before preparing food, as well as after using the toilet.
Oocysts are not killed by typical household disinfectants, including bleach, but are killed at temperatures over 160 F (hotter than most domestic hot tap water). Thorough drying in a clothes dryer will kill oocysts by desicating them.
Is cryptosporidiosis a new disease?
Cryptosporidiosis has long been a veterinary problem, predominantly in young farm animals, such as calves. Cryptosporidium was first recognized as a cause of human disease in 1976 but was rarely reported in humans until 1982. The number of detected cases began to rise rapidly along with the AIDS epidemic and the development of methods to identify the parasite in stool samples. The earliest cases of human cryptosporidiosis were diagnosed in animal handlers. An outbreak at a day care center was first documented in 1983.
In 1987, 13,000 people in Carrollton, Georgia became ill with cryptosporidiosis. This was the first report of its spread through a municipal water system that met all state and federal drinking water standards. In the spring of 1993 in Milwaukee, Wisconsin, municipal drinking water, again within standards, was contaminated with Cryptosporidium. An estimated 400,000 people became ill and the disease contributed to the deaths of some AIDS patients. These outbreaks focused attention on the risk of waterborne cryptosporidiosis and the possible need for stricter drinking water standards.
How many people get cryptosporidiosis?
We do not know exactly how many cases of cryptosporidiosis actually occur. Many people do not seek medical attention or are not tested for this parasite and so, Cryptosporidium often goes undetected as the cause of an intestinal illness.
Health professionals in some states are on the lookout for cases of cryptosporidiosis through surveillance programs at hospitals, clinics and labs. The Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia keep track of many disease-causing organisms and send out warnings and advice on controlling outbreaks to every health department in the United States.
How prevalent is Cryptosporidium in surface water?
Oocysts are present in most surface bodies of water (e.g. lakes and rivers) across the United States, many of which supply public drinking water. Oocysts are more prevalent in surface waters when heavy rains increase runoff of wild and domestic animal wastes from the land or when sewage treatment plants are overloaded or break down.
Only laboratories with specialized capabilities can detect the presence of Cryptosporidium oocysts in water. Unfortunately, current sampling and detection methods are unreliable. It is difficult to recover oocysts trapped on the material used to filter water samples. Looking at a sample under a microscope, it is not easy to determine whether an oocyst is alive, or whether it is the species Cryptosporidium parvum that can infect humans.
The number of oocysts detected in raw (untreated) water varies with location, sampling time and laboratory methods. Water treatment plants remove most, but not always all oocysts from municipal drinking water. It is not known exactly how many oocysts are sufficient to cause cryptosporidiosis, but the low numbers of oocysts sometimes present in drinking water are not considered cause for alarm in the general public.
How can we protect our water supplies from Cryptosporidium?
Multiple barriers are needed to protect our water supplies from Cryptosporidium. Water treatment methods alone cannot solve the problem; watershed protection and monitoring of water quality are critical.
Cryptosporidium oocysts have tough walls that can withstand many environmental stresses and are resistant to the chemical disinfectants such as chlorine that are traditionally used in municipal drinking water systems and swimming pools.
Physical removal of particles, including oocysts, from water by filtration is an important step in the municipal water treatment process. Typically, water pumped from rivers or lakes into a treatment plant is mixed with coagulants which help settle out particles suspended in the water. If sand filtration is used, even more particles are removed. Finally, the clarified water is disinfected and piped to customers. Filtration is the only conventional method now in use in the United States for controlling Cryptosporidium.
Ozone is a strong disinfectant that kills protozoa if sufficient doses and contact times are used, but ozone leaves no residual for killing microorganisms in the distribution system as does chlorine. The high costs of new filtration or ozone treatment plants have to be weighed against the benefits of additional treatment. Even well-operated water treatment plants cannot ensure that drinking water will be completely free of Cryptosporidium oocysts.
Watershed protection is another barrier to Cryptosporidium in drinking water. Land use controls such as septic system regulations and best management practices to control runoff can help keep human and animal wastes out of the water.
Water treatment and monitoring regulations
Under the Surface Water Treatment Rule of 1989, public water systems are required to filter surface water sources unless water quality and disinfection requirements are met and a watershed control program is maintained. This rule, however, did not address Cryptosporidium. The U.S. Environmental Protection Agency (USEPA) has set standards for turbidity (cloudiness) and coliform bacteria (which indicate that pathogens are probably present) in drinking water. Frequent monitoring is required so officials will have an early warning of potential problems and can take steps to protect public health. Unfortunately, there are no water quality indicators that can reliably predict the occurrence of cryptosporidiosis. More accurate and rapid assays for oocysts will make it possible to notify residents promptly if their water supply is contaminated with Cryptosporidium and thus, avert outbreaks.
Efforts are underway to answer questions about the occurrence, detection, and treatment of Cryptosporidium in water so that the EPA and states can set specific standards for this parasite in the future. The collaborative efforts of water utilities, government agencies, health care providers, and individuals are needed to prevent outbreaks of cryptosporidiosis.
How can you tell if the tap water is safe?
Properly drilled and maintained wells that tap into groundwater are unlikely to contain pathogens because of the natural filtration that takes place as water percolates down through the soil. However, contaminants may flow into groundwater aquifers which lie beneath coarse soils or fractured bedrock. Very shallow or poorly constructed wells and springs can be contaminated with surface water runoff that carries disease-causing microbes. It is important that the well be protected from surface contamination by an intact well casing, proper seals, and a cap above ground.
The risk of waterborne cryptosporidiosis from public drinking water varies depending on the quality of the source water and type of water treatment. HIV-infected persons should follow the guidelines issued by the CDC and talk with their health care providers about safe drinking water. When routine testing of public drinking water indicates potential danger, the health department and/or water utility will issue a "boil water" notice.
How can you make sure your own drinking water is safe?
There are three measures you may wish to take to ensure that your drinking water is safe: boil your water to kill the pathogen, remove oocysts from your water with certain types of filters, or drink certain types of bottled water.
Boiling water is the best method of killing Cryptosporidium and other waterborne pathogens; water should be brought to a rolling boil for at least one minute. It should be stored in the refrigerator in a clean bottle or pitcher with a lid. To prevent recontamination, be careful not to touch the inside of the water bottle or lid.
Water can be filtered to remove Cryptosporidium oocysts and the cysts of another protozoan parasite, Giardia lamblia. Point-of-use filters may be used to treat the water to be used for drinking or preparing foods. They may be either attached to a faucet or have a pour-through design. Only filters with an "absolute" (not "nominal") pore size of one micron or smaller will remove all the oocysts (viruses, however, can pass through a one-micron filter). The pore size of reverse osmosis (RO) membranes are too small for oocysts to pass through. NSF International, an independent non-profit testing agency, publishes lists of filters and RO units certified for "cyst reduction". Follow the manufacturer's instructions that are supplied with water treatment equipment to prevent clogging and ensure proper filtration. The filter cartridge(s) and/or membrane will periodically need to be replaced. Improper maintenance can actually increase health risks.
Isn't all bottled water safe to drink?
Under current standards, bottled water is not necessarily any safer than tap water. Bottled water from deep wells (ground water sources) has a very low likelihood of containing oocysts, but bottled water from a surface water source has the same risk of containing oocysts as tap water from that source unless it is treated before bottling.
Read the label on bottled water for information about the water source and treatment. Water can be distilled or pasteurized to kill all pathogens before bottling. Procedures for using ozone to inactivate oocysts in bottled water have not yet been established. Oocysts can be removed by reverse osmosis or a filter with an absolute one micron rating. Other microfiltration or ion-exchange methods or treatment with chlorine, carbon dioxide, or ultraviolet light cannot promise crypto-free water.
The heat of pasteurization will kill all pathogens in dairy products. Bottled and canned bubbly drinks, such as sodas and beer, are usually heated and/or filtered enough to kill or remove Cryptosporidium.
How can you avoid getting cryptosporidiosis?
You can minimize the chances of getting infected with Cryptosporidium (and numerous other pathogens) by always practicing good hygiene, especially after possible exposure to sources of infection. People with compromised immune systems must consistently take precautions to avoid exposure to Cryptosporidium.
Wash your hands thoroughly with soap and water (and supervise children's hand washing) after using the toilet or changing diapers, after handling animals or cleaning up feces, after working in dirt or touching any objects, such as shoes, that may have been contaminated with fecal matter, before eating, preparing or serving food. Avoid drinking untreated water from lakes, streams, and other surface water bodies. Because of possible contamination with manure, peel or rinse fruits or vegetables to be eaten raw. Take extra care in selecting food and drink when traveling to places with poor sanitation. Follow any water advisory issued by local health departments, state authorities, or the national Centers for Disease Control and Prevention. To treat contaminated water before drinking it, bring it to a rolling boil for at least one minute to kill oocysts or remove them with a filter with an absolute pore size of one micron or smaller.
This organic sporozoan, first described in 1907, wasn't recognized as a cause of human illness until 1976. It is a protozoan parasite that can infect a variety of animals. In the environment, Cryptosporidium exists as a resilient, infectious, round oocyst about four to six microns in diameter. The cyst is a "suitcase" for the infectious material inside.
Cryptosporidium is widespread in the environment. Oocysts (cysts) have been found in rivers, streams, lakes, reservoirs, sewage, and treated surface water. Once introduced to water, the oocyst can survive for weeks, even at low temperatures. The organism has been found in humans, cattle, sheep, swine, goats, cats, and dogs as well as deer, raccoons, foxes, coyotes, beavers, muskrats, rabbits and squirrels. Oocysts infecting certain species can infect another (referred to as cross-transmission). For example, organisms from domestic animals (cattle, dogs, eats, etc.) are able to infect humans, Conversely, organisms from humans can infect animals. Consequently, animals which typically reside in or around watersheds may serve as hosts to the cysts and continuous sources of infection. This is where the nick name "Beaver Fever" was born. Beavers carry the organisms and through their feces spread it throughout surface water supplies without becoming ill themselves. Moreover, infection can occur not only from drinking contaminated water but also from eating contaminated food and from exposure to fecally contaminated environmental surfaces.
When ingested, the Oocysts pass through the stomach into the small intestine. There the Oocysts split open, releasing sporozoites which invade the cells lining the gastrointestinal tract. Infected cells lining the intestine appear normal, but their ability to absorb water and nutrients is severely impaired. The water and food ingested simply passes through the digestive system. Additional Oocysts are formed in the intestine and either split open to release additional sporozoites to continue the infection or are excreted in the feces.
The Cryptosporidium infection causes an illness called cryptosporidiosis. After the Oocysts are ingested, the incubation period typically varies from two to 12 days with an average of seven days. Disease symptoms include diarrhea, abdominal cramps, nausea, occasional vomiting and low grade fever.
The number of Oocysts that must be ingested to cause infection in humans is not conclusively known. Studies indicate that as few as ten and perhaps as many as 500 Oocysts are required to initiate infections in mammals. The infectious dose for humans is thought to be fewer than ten.
Cryptosporidiosis typically last 10 to 14 days. However, it may linger off and on for up to 30 days and infrequently can persist for extended periods. Children may be the most susceptible, particularly six year olds and under. A rapid cure for Cryptosporidiosis has not been found. Recovery depends on the patient's overall health and immune system. The disease can be fatal for those who are already in a fragile state such as someone with AIDS or any others weakness to their immune system.
There are two varieties of the oocyst; (1) a sphere of about 4.5 micron in diameter and (2) an ellipse of about 7 x 5 micron. The thick walls of the Oocysts make it difficult, almost impractical, to kill with the UV systems in most domestic water treatment systems. Also, the cyst is much more difficult to kill using chlorine than normal coliform bacteria found in water supplies.
Ceramic filter elements are manufactured so that they remove pathogenic bacteria down to 1 micron in size; they are 100% effective in the removal of Cryptosporidium.