Source: Ministry of Agriculture, Food and Rural Affairs
Fact Sheet written by: Ron Fleming – P. Eng.,Ridgetown College/University of Guelph; OMAFRA Staff
What Is Cryptosporidium?
Cryptosporidium (krip-toe-spor-id-ee-um) is a tiny parasite, a protozoa, which reproduces and causes disease in humans and animals. This parasite has been associated with large outbreaks of human illness in Canada and the U.S. It can be found in the digestive organs and respiratory tract. Even though the organism was first identified early in the 20th century, the disease cryptosporidiosis wasn’t identified until 1976. It has caused outbreaks of illness where thousands of people were infected.
There are 6 recognized species of Cryptosporidium but C. parvum is the species of greatest concern to humans and livestock farmers. This parasite has a rapid life cycle, and can reproduce in the intestinal wall within 12 hours.
Route of Infection
The life cycle of this parasite occurs within one animal, but consists of several stages. The oocyststage is the infectious stage. The oocyst is approximately 4 µm (= 0.004 mm) in width, but is able to fold over and travel through smaller openings, creating problems with some water filtration systems. Oocysts are released from the intestinal wall into the fecal material of the infected animal or person. Other people become infected after oocysts enter their mouths. This can occur through person-to-person or animal-to-person contact, or by the ingestion of contaminated water or food.
Poor hygiene often leads to infection. Contact with toilets, diapers, dirt, or animal feces are common sources of infection. The ingestion of contaminated water or food is the most publicized route of infection.
Infection in humans may result in diarrhea, abdominal cramps, headaches, nausea, vomiting and a low-grade fever. The initial symptoms can persist and develop into weight loss and dehydration in severe cases.
Not everyone exposed to the protozoa gets sick. The infection may resolve without supportive treatment. This disease often produces no symptoms, but can still be spread to others.
People with a weak immune system are more severely affected. In these cases, symptoms may persist for long periods. Patients undergoing chemotherapy, recent transplant recipients, AIDS patients, the elderly, and young children are at greatest risk of severe disease.
To date, there is no specific treatment for cryptosporidiosis. The treatment is limited to addressing the symptoms of the disease, and making sure the patient doesn’t become dehydrated.
The symptoms are similar for animals. Most often, it is young animals that become infected. Calves become infected under 6 weeks of age, and approximately 25% of calves with diarrhea between 5 days to 1 month old are infected with C. parvum. The symptoms of an acute infection include watery, yellow diarrhea (sometimes containing flecks of blood), mild fever, dehydration, and lethargy. The symptoms of a chronic infection include semi-formed stools, little to no fever, and weight loss. Severe infections are associated with younger animals, inadequate colostrum intake, larger herd size, and poor sanitation. The duration of infection can persist for months and can take considerable effort to eliminate from the herd.
Prevalence In Livestock
Many studies have been done on the prevalence of C. parvum among farm animals worldwide. It appears from these studies, including a 1997 Ontario study that if enough samples of fresh manure are collected over a long enough period, over 50% of the farms will test positive for Cryptosporidium at least once.
Various studies on beef and dairy farms have shown that when large numbers of samples from several farms are analyzed, about a quarter of the total samples have tested positive. Swine herds are also commonly infected. The 1997 Ontario study found about a quarter of all swine manure samples contained Cryptosporidium. It was detected at least once on 18 of the 20 swine farms in the study (Figure 1).
Figure 1. Collecting manure samples in a swine barn during a recent Ontario study.
Although the oocyst shell is thick and resistant to many chemicals such as chlorine, it is susceptible to drying, freezing, and ultraviolet light. Drying appears to kill oocysts in a matter of hours. With 10 or more days of freezing, one study showed that more than 90% of the oocysts were non-infective. However, at temperatures as high as 30°C, oocysts are able to survive for up to 2 weeks. They are soon killed, though, at temperatures over 55°C, typical of composting. One viability study showed that a small percentage of oocysts could survive in surface water up to at least 6 months. Oocysts can survive for several months in typical liquid manure tanks, as demonstrated by a 1999 Ontario study.
Prevalence In Surface Waters
Because many North American cities rely on surface water as their main source of drinking water, prevalence of Cryptosporidium is important. A study of western United States surface waters foundCryptosporidium in about ¾ of the samples. Most of the studies show that between 25% and 75% of surface water samples contain at least a few Cryptosporidium organisms. Wild animals (e.g. raccoons, deer, mice) are known to carry Cryptosporidium (Figure 2).
Figure 2. Cryptosporidium, from a variety of sources, is often found in surface water.
When It Shows Up In Water, Who Is To Blame?
There are actually quite a few potential sources of Cryptosporidium in the environment. The list of most likely sources includes:
- sewage treatment plant discharge
- municipal storm sewer discharge
- overland runoff from manure storages and feedlots
- illegal connections of domestic septic systems to subsurface drains emptying into surface water
- runoff from fields receiving livestock manure
- runoff from fields receiving sewage sludge
- livestock manure entering streams as a result of defecation in or near streams
- other sewage sources (e.g. interception of septic plumes by surface water or marine discharge)
A 1999 Ontario study found significantly higher levels of Cryptosporidium in tile drainage water from livestock watersheds than non-livestock areas (Figure 3). However, there were infective organisms in drainage waters from the non-livestock areas also. Other than the association with livestock watersheds, a larger number of samples may have helped narrow down other significant contributors, and studies continue to be carried out to determine these influences.
Figure 3. Cryptosporidium has been found in tile drainage water, even in watersheds with no livestock.
Prevention in People
The best way to prevent infection is to limit contact with feces. Following are specific recommendations.
- Farm workers should pay close attention to personal hygiene, and hygiene between the barn and house.
- Make sure children wash their hands as thoroughly as possible. Cryptosporidium parvum and other pathogens are present in animal manure. Farm safety includes controlling exposure of young children in the barn or around the barnyard.
- Wash hands with soap and water following contact with toilets, diapers, animals or animal feces, after working in dirt or touching objects that may have come in contact with fecal matter and before preparing or serving food.
- Avoid drinking untreated surface water or water from a poorly constructed or maintained well.
- If there was any possible contact with manure, wash thoroughly all fruit and vegetables to be eaten raw.
- Practise proper personal hygiene when treating sick livestock.
- Seek proper medical care when dealing with persistent gastrointestinal problems in animals and humans.
- Check well water in rural areas at least once a year (more often for shallow wells) for the potability of the water.
- Follow proper well-head construction to limit the possibility of contamination by manure or septic systems.
Control Measures on Farms
The best method of control is to limit the fecal–oral route of transmission of oocysts between young animals. Since the oocysts are not killed by most disinfectants, emphasis must be on cleanliness and reasonable levels of young livestock density. Below are recommendations for control and for preventing environmental impacts.
- Raise young animals in clean and dry environments. In the case of dairy farms, raise the young calves in separate hutches.
- Separate healthy and sick animals and the manure of these animals.
- Control mice and rat populations as much as possible, since they may be a reservoir for infective feces.
- Ensure adequate colostrum intake.
- Seek diagnosis from a veterinarian in cases of persistent diarrhea.
- When bringing new animals into the herd, ensure that the health history of the herds of origin do not include persistent diarrhea problems.
- Quarantine for 2 weeks all purchased animals to observe for scouring.
- Collect and store liquid manure in proper storages and store any runoff liquid from solid manure systems and barnyards.
- Manure storage facilities are regulated under Nutrient Management Act (NMA) Regulation, Part VIII, s. 62–88.
- Spread manure so as to minimize any risks of surface water or ground water contamination.
- Verify with the NMA Regulation to determine the distance required between surface water and manure application. All operations should avoid spreading manure within 13 m of surface water unless special precautions are taken to reduce the risk of runoff to the surface water.
- Maintain vegetated buffer zones adjacent to surface waters in fields where manure is applied.
- Land applications are regulated under NMA Regulation, Part VI, s. 39–50.
- After manure application, wait before returning animals to graze in those fields; wait 2 months before grazing horses or cattle and 6 months before grazing swine, sheep or goats.
- After manure application, avoid cutting forages for 3 weeks and wait until all signs of manure have disappeared
- See NMA Regulation, Part VI. s. 51–52 for pre-grazing and pre-harvest waiting periods.
- Restrict livestock from access to surface watercourses.
- Livestock access to surface watercourses is regulated under NMA Regulation, Part VII, s. 57.
Fleming, R., Hocking, D., Fraser, H., and Alves, D. 1999. Extent and magnitude of agricultural sources of Cryptosporidium in surface water. Final report to Agricultural Adaptation Council, Guelph, for the National Soil and Water Conservation Program. Available for download from the Ridgetown College website.
- Ontario Environmental Farm Plan (the Farm and Food Care and OMAFRA websites has information on the Ontario Farm Environmental Coalition)
- Best Management Practices – Water Wells, BMP 12 The BMP publications can be ordered through the OMAFRA Home Page.
- Nutrient Management Protocol, Construction and Siting Protocol, Nutrient Management Act, 2002 and O. Reg. 267/03.