The Cryptosporidium Parasite and its effect on Calves and Humans

Mother Nature throws many obstacles in the path of ranchers on a daily basis and keeping cows and calves healthy is one of the biggest challenges. This challenge intensifies when the concern for contracting diseases from livestock poses a threat. Cryptosporidiosis is a zoonotic disease, meaning transmission from sick calves to humans is possible, is one such disease that creates a concern for people in contact with cattle.

Cryptosporidium parvum, commonly referred to as Crypto, is a group of single-celled intestinal parasites in animals and humans that causes the disease Cryptosporidiosis. Historically, reported cases of the disease originate from fecal contaminated drinking water or food. The risk to livestock handlers is that the disease is contracted from ingesting infectious Cryptosporidium parva oocytes, or immature eggs, from direct contact with fecal material from animals actively shedding these eggs. The incidence of bovine Crypto diarrhea is higher on dairy farms where confinement and the moist environment is conducive to the spread of these protozoa. However, it is also being identified more often in beef herds in the west. In fact, according to veterinarian Scott Davis, who works throughout central Oregon, Crypto in calves is fairly common.

The most common clinical sign of this condition is diarrhea in calves and other mammals. People not only experience explosive diarrhea, but also suffer from abdominal cramps, dehydration, headaches, vomiting, fever, malaise and muscle cramps. If medical attention is not administered, death can occur in severe cases. Children, pregnant women, people with compromised immune systems and the elderly are the most vulnerable and typically have the most severe reaction to this parasite. Unfortunately, there is no commonly advised specific treatment for cryptosporidiosis, and recovery usually depends on the health of your immune system and medical assistance.

Historically, North American outbreaks of cryptosporidiosis in humans have primarily been associated with stool contamination of water supplies. However, this only accounts for 10% of cases reported in the USA. The source of infection in the rest of these cases is usually unknown, but transmission from animals, particularly Cryptosporidium parvum from calves is suspected in some cases. Calves are most commonly infected with the zoonotic species of Cryptosporidium parvum. Although, calves after weaning tend to be more commonly infected with other species of Cryptosporidium that are not zoonotic.

This zoonotic risk poses challenges to humans working with or around 1-4 week old calves. If infected, these animals could potentially transmit Cryptosporidium parvum to people and make them extremely ill. Crypto can be passed by putting anything in one's mouth that has been in contact with the feces of an infected person or animal. Those sickened with Crypto often do not suspect contamination from the feces of sick calves and therefore do not know to tell medical personnel of their handling and contact with young calves. This can put off testing for the disease and delay accurate diagnosis. Ranchers, dairymen, veterinarian students and others working around young calves need to be aware of and take precautions against infection.

Cryptosporidium parvum was first described in 1907. Since then, over 30 species of Cryptosporidium have been discovered that infect a wide range of host species. There are four species that commonly infect cattle. They are C. parvum, C. bovis, and C. andersoni, and a Cryptosporidium deer-like genotype. Of the four, only Cryptosporidium parvum is a zoonotic disease. In the early 1970s it was first reported in cattle. At that time, the observed clinical disease could not be solely attributed to Cryptosporidium because there was evidence of co-infection with other viral and bacterial pathogens. In 1983, diarrhea in experimentally infected calves reported Cryptosporidium species as the single infective agent. It is now recognized as endemic in cattle worldwide and is one of the most important causes of neonatal enteritis in calves globally.

Nationally, infections began to rise in the early millennium, but the incidence of disease has stabilized since 2009. Oregon’s incidence of Cryptosporidium remains twice the national rate (2.6 per 100,000 persons). Cases occur year-round with peaks in August that coincide with increases in exposure to recreational water. Late winter and spring calving season poses a threat to Oregon cattlemen and women as young calves are handled in order to vaccinate, tag and brand. Contact with infected calves during these activities has been blamed for the transmission of Cryptosporidium to ranchers. As it is a communicable disease, cases must be reported to the Public Health Division.

Though neonatal calves less than six weeks of age are most commonly infected with the zoonotic species of Cryptosporidium parvum, adult cows can also be infected. However, adult cows may not show any signs of infection depending on the strength of their immune system. Calves infected with Cryptosporidium parvum can become weak and lethargic and have diarrhea that can be mild or severe in intensity. Feces can contain mucus, blood, or undigested milk. Feces are yellow or pale, and watery. In some cases, the persistent diarrhea may result in marked weight loss and emaciation. In most cases, the diarrhea is self-limiting after several days. Cryptosporidium is most infectious when the parasite is passed in feces and then ingested. Infected calves can have Crypto in their feces for weeks after they are no longer sick. When the immature eggs are ingested, fertilized spores are released and invade the cells of the intestines. Infection of cells leads to cell destruction and results in atrophy and fusion of intestinal villi, the finger-like projections extending from the intestinal lumen that are primarily responsible for nutrient absorption. This kind of an event can negatively influence the calf’s ability to grow and develop even when it survives the illness.

This zoonotic risk poses challenges to people working with or around infected young calves. The risk of infection is substantial as eggs are passed in the manure of infected calves in very large numbers (up to 10 million per gram of manure). During an average infection, a calf may excrete the Crypto eggs for six to nine days, scour for three days, and shed approximately 40 billion eggs. Due to the potential of large amounts of eggs in a gram of manure, simple actions like wiping your mouth with the back of your hand, touching your mouth, or even handling clothes and equipment contaminated with manure and then touching your mouth can spread the parasite.

“It’s not unusual for calves to be sickened with a disease and then develop Crypto as a secondary disease since immunosuppressed and stressed animals are more susceptible to Crypto. In addition, Cryptosporidium parvum can further degrade the calf’s immunity making the animal at greater risk for co-infection with other diseases,” says Dr. Davis. Dr. Davis recommends checking for Crypto in the feces of sick calves in order to approach treatment in an effective and timely manner. The best way to diagnose Cryptosporidium parvum is to work with your veterinarian and submit a fecal sample to the Oregon State Diagnostic lab. The lab can run a real time polymerase chain reaction (PCR) test that will determine if Crypto is present.

There is no effective or approved treatment for Cryptosporidiosis in cattle. However, many cases will recover on their own. Sick calves should be housed in a clean, warm, and dry environment and receive intensive support. They need fluids to counteract and prevent further dehydration as well as electrolytes to replace fluids lost due to diarrhea. They also need nutritional support to give them energy to fight disease and repair their bodies. Keeping sick calves hydrated and adequately nourished is critical to a short disease course. Moving unaffected cows and calves to a clean area and away from infected calves will help prevent the spread of disease to other calves. Ranchers should exercise caution when bringing in dairy calves to graft onto beef cows, as dairy calves can be a source of infection.

Unfortunately, there is not a vaccine commercially available to prevent the disease in cattle and no licensed treatments for sick calves. Therefore, good biosecurity and sanitation practices are essential as a control method that can help limit the duration and spread of the disease. Keeping corrals and livestock pens clean of manure is essential. Crypto eggs have a tough outer shell and are very resistant to disinfectants, even chlorine bleach, and can survive outside the body and in the environment for very long periods of time. Generous applications of a 3% hydrogen peroxide do work as well as exposure to high temperatures in excess of 160° F, which is hotter than most domestic tap water, and cold temperatures below -4° F. The Crypto eggs can also be desiccated and killed by completely drying clothes in a hot dryer after washing them.

The potential transmission of Cryptosporidium parvum from sick calves to people requires an understanding of preventative strategies for working with these animals. Wear dedicated clothing and shoes when working in the barn or corral. Remove all of it before entering the main part of the house. “It is a good idea to use separate boots, clothing, and equipment for dealing with sick calves,” says Dr. Davis. Wash hands with soap and running water for 20 seconds before eating or drinking after working with animals on the farm. Avoid touching your mouth when working with animals. Avoid eating or drinking in the barn. Keep pets out of the barn to keep them from becoming infected and tracking manure into the house. Provide play areas for children that are located away from calf housing or other areas of the farm that may be contaminated with manure. It is generally recommended that immunosuppressed people avoid contact with diarrhetic calves since they are at higher risk for zoonotic transfer.

This scour-related disease, Cryptosporidiosis, can impose a loss of potential income to cattlemen. In extreme cases, death can occur from this disease. The biggest expenses to the producer come from treatment costs, slow weight gain, and susceptibility to other diseases.& Additionally, the threat of a zoonotic disease is significant enough to prompt people working with cattle and sick calves to take sufficient care with hygiene when handling calves in order to avoid catching, suffering, and spreading the disease.


  • Thomson, Sarah., et al. 2017. “Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies”. Veterinary Research 48:42.
  • Lewis, Roy. 2016. “Beef 911: Crypto presents a number of challenges”. Manitoba Co-operator.
  • Chako, C.Z., et al. 2010. Cryptosporidiosis in People: It’s Not Just About the Cows. Journal Veterinarian Medicine. 24:37-43.
  • Hodges, Rebecca. n.d.. Cryptosporidiosis in Calves.
  • Cryptosporidium For Pet Owners. (2008, September 4.)
  • Cryptosporidiosis. (2015). Public Health Division.
  • Cryptosporidiosis Fact Sheet. (2018, May)
  • Reif, J.S., et al. 1989. “Human Cryptosporidiosis Associated with an Epizootic in Calves”. American Journal of Public Health 0090-0036/89.
  • Pelzer, K.D. and N. Currin. 2009. “Zoonotic Diseases of Cattle”. VCE Publications / 400/400-460.

Related Content from OSU Extension

Have a Question? Ask an Expert!

Ask an Expert is a way for you to get answers from the Oregon State University Extension Service. We have experts in family and health, community development, food and agriculture, coastal issues, forestry, programs for young people, and gardening.

Ask Us a Question