Coccidiosis in Calves and Heifers – Dr. David Carlson, Elanco Animal Health

Posted on August 29, 2013 in Starting Strong - Calf Care
By Dr. David Carlson, Elanco Animal Health

Coccidiosis is an infection of the large and small intestines caused by protozoan parasites.  Coccidiosis is a costly disease with an estimated worldwide economic impact of $400 million annually due to death loss and veterinary costs associated with clinical infection.  This estimate of economic impact does not include the cost of reduced productivity (e.g., weight gain, feed efficiency).

Infected animals shed infective oocysts in feces, which may remain dormant for weeks or months in soil, water and vegetation.  These pathogens thrive in a moist, moderate, airy environment.  Non-infected animals become infected by consuming oocysts from fecal-contaminated pasture, feed, water or bedding, and by grooming contaminated hair coats.  The infection destroys cells lining the lower GI tract, causing intestinal damage and a reduction in nutrient absorption. The lifecycle of the coccidia organisms includes several stages; during the final stage, intestinal damage and clinical signs may appear and oocysts are shed in feces.  The period of time between ingestion of the organism and onset of clinical signs is 17 to 22 days.

Clinical outbreaks of coccidiosis may be recognized by diarrhea, bloody diarrhea, depression, reduction in feed intake and death.  Subclinical incidence of the disease can include signs of poor appetite, reduced daily gains, increased incidence of secondary respiratory disease and a decreased response rate to respiratory therapy.

Coccidiosis outbreaks are most prevalent in animals younger than one year. In particular, calves older than three weeks and up to six months of age are most vulnerable to coccidiosis.  Conditions in which animals are more susceptible to coccidiosis are:

  • Overcrowded and/or confinement housing situations (freestall barns, feedlots, small pastures)
  • “Stressful” situations (weaning, pen moves, shipping and diet/weather changes)
  • Lack of an effective coccidiosis control program or lack of an effective ionophore in the diet

Producers can prevent coccidiosis in their replacement animals by limiting fecal-to-oral transmission of the coccidiosis parasite through environmental management.  Management strategies may include:

  • Minimizing exposure of animals to fecal-contaminated feed, water and soil
  • Routinely cleaning maternity pens for early prevention
  • Employing all-in/all-out hutch management (clean and relocate hutches between calves)
  • Minimizing contact between calves
  • Routinely washing boots and clothing of people in contact with calves
  • Preventing overgrazing of pastures
  • Raising water troughs above the ground
  • Supplementing an anti-coccidial agent (see table below) in the calf starter and heifer grain to prevent coccidiosis breaks
  • Managing stress (pen moves, weaning, dehorning, vaccination and diet changes)
  • Isolating animals with severe clinical signs (severe diarrhea and dehydration)

Agents are either coccidicidal (cidal), which means they KILL the parasite, or coccidiostatic (static), which do not kill the parasites, but arrest their development.  With coccidiostatic treatment, the live parasites will still be present in the calf’s intestines.

Agent Killing action Trade name Route of supplementation
Monensin Cidal Rumensin® Dry feed
Lasalocid Cidal Bovatec® Milk replacer, dry feed
Amprolium Cidal Corid® Water, dry feed
Decoquinate Static Deccox® Milk replacer, dry feed

Rumensin is a registered trademark of Elanco Animal Health.  Bovatec and Deccox are registered trademarks of Zoetis.  Corid is a registered trademark of Merial.


  1. Daugschies, A and M Najdrowski. Eimeriosis in cattle:  current understanding. J. Vet. Med. B. 52:417-427, 2005.
  2. Jolley, WR and KD Bardsley. Ruminant coccidiosis. Vet Clin. Food Anim. 22:613-621, 2006.
  3. McDougald, LR. Chemotherapy of coccidiosis. IN: The Biology of the Coccidia, ed. PL Long, University Park Press, Baltimore. 373-427, 1982.
  4. Long, PL and TK Jeffers. Studies on the stage of action on ionophorous antibiotics against Eimeria. J. Parasitol. 68:363, 1982.
  5. Ernst, JV and GW Benz. Intestinal coccidiosis in cattle. Veterinary Clinic of North America: Food Animal Practice. 2:283, 1989.
  6. Merrick’s Tech Bulletin #6RMC0811, 2006.

Directions for use of Rumensin or other compounds are available upon request.

Category: Animal handling
Animal health
Starting Strong - Calf Care