08 May Cryptosporidiosis in calves
By Rebecca Hodges, Kansas State University Extension
Introduction Cryptosporidium parvum: Cryptosporidium parvum, commonly referred to as Crypto, is a protozoan (a one-celled organism) that causes diarrhea in calves (as well as other mammals). This extra-cytoplasmic organism invades enterocytes (cells that line the intestines) in the distal small intestine and large intestine; therefore, intestinal pathology is worst in these portions of the intestines.
Life Cycle: The infective stage of the life cycle of Crypto is the oocyst which is passed in the feces and which contains four sporozoites. When the oocyst is ingested the sporozoites are released. These sporozoites invade the cells in the intestine. These sporozoites go through several life stages and ultimately produce more oocysts. Both thick-walled and thin-walled oocysts are produced. The thick-walled organisms are passed in the feces. The thin-walled oocysts can rupture and the sporozoites can infect new host enterocytes resulting in autoinfection which may lead to relapses or protracted disease. Infection of cells leads to cell destruction and results in atrophy and fusion of intestinal villi (finger-like projections extending from the intestinal lumen that are primarily responsible for nutrient absorption).
Presentation/Clinical Signs: Calves affected with Crypto are usually one to four weeks of age. These calves become weak and lethargic and present with loose to watery stool that may be mild or severe in intensity. Feces can contain mucus, blood, undigested milk, or bile. Tenesmus (straining to defecate) may be seen. Oocyst shedding typically begins with diarrhea and continues for a few days passed resolution of clinical signs. This is important to remember when determining the time to return previously isolated ill calves to a healthy herd.
Diagnosis: A presumptive diagnosis of Cryptosporidiosis can be made based on history, and clinical signs. Definitive diagnosis can be made by doing a fecal floatation and Giemsa or acid-fast stains. Infections in recently dead calves can be diagnosed via microscopic examination of mucosal scrapings or fixed tissue secretions.
Treatment: There is no effective or approved treatment for Cryptosporidiosis. Morbidity is high with this disease but mortality is generally low. However, calves do need intensive supportive care. Sick calves should be housed in a clean, warm, and dry environment. They need fluid therapy to counteract and prevent further dehydration as well as electrolytes to replace those lost due to diarrhea. They also need nutritional support to give them energy to fight disease and repair their bodies. A recent study showed no clinical benefit to administering decoquinate as a preventative treatment for cryptosporidiosis. (Moore, D.)
Economic Loss: Mortality with this disease is generally low. However, calves that suffer from cryptosporidiosis usually have a slower growth rate than other calves. There is also increased cost in the labor involved in supporting these calves through their disease and in the cost of rehydration fluids.
Transmission: Infection with this organism is caused by ingestion of infectious oocysts. Crypto is very resistant to disinfectants (even chlorine bleach) and can survive in the environment for very long periods of time. Oocysts can be killed at temperatures in excess of 160o F (hotter than most domestic tap water). Oocysts can also be desiccated and killed by thorough drying in a clothes dryer.
Prevention: Although the organism is very resistant, moving unaffected calves to a clean area and away from affected calves may prevent the spread of disease on the farm. General sanitation practices are also a primary control method that yields high results. While Cryptosporidium is highly resistant to chlorine (sodium hypochlorite / bleach) disinfection, with high enough concentrations and contact time, Cryptosporidium will be inactivated by chlorine dioxide and ozone treatment. Chlorine dioxide, has been proven to be extremely effective when used as a premise sanitizer on walls, floors and feeding equipment.
Although it has been shown that calves that do not receive colostrum are not more likely to get cryptosporidiosis that calves that do receive colostrum, efforts should always be made to ensure adequate colostrum intake by calves. However, receiving adequate colostrum immediately after birth helps prevent invasion of opportunistic pathogens which can worsen or compound the severity of disease in calves with cryptosporidiosis.
Studies have been done to test trial vaccines. Some of these vaccines have been shown to be clinically significant (no field trial have been done) not only in preventing clinical disease but in reducing environmental contamination with the organism. However, there are currently no vaccines commercially available to prevent the disease.
Zoonosis Crypto can also infect humans as well as most mammals. Anyone handling an animal with cryptosporidiosis should take great care to practice good personal hygiene. Crypto is most commonly spread to humans through contact with a contaminated water source such as a contaminated well or recreational water source (lake or swimming pool). The disease may also be spread through contamination of food through an infected food service worker.
Bowman, D. Georgas, Parasitology for Veterinarians. W. B. Saunders Company, Philadelphia, 1999.
Cryptosporidiosis (Crypto) [Internet] Available from: http://www.cvm.missouri.edu/favpdseries/Course 20I/Homework Reading/Food Animal Diseases/Cattle Diseases/Cryptosporidiosis (Crypto).doc [Accessed December 8, 2004]
Harp, J, Goff, J. (1995) “Protection of Calves with a Vaccine against Cryptosporidium parvum”. [Internet] Available from: http://www.extension.iastate.edu/Pages/dairy/report95/health/dsl-52.pdf [Accessed December 8, 2004]
Kneen, B, Darling, S, Lemley, A. (2000) “Cryptosporidium: A Waterborne Pathogen”. [Internet] USDA Water Quality Program, Cornell Cooperative Extension. Available from: http://www.cce.cornell.edu/factsheets/wq-factsheets/cryptosporidium.htm [Accessed December 17, 2004]
Moore, D, et al. Prophylactic use of decoquinate for infections with Cryptosporidium parvum in experimentally challenged neonatal calves. JAVMA 2003: 223 (6): 839-844.
Vaala, W, House, J. “Manifestations of Disease in the Neonate” from Large Animal Internal Medicine. Mosby, St. Louis, 2002.