Nature of the disease

Key signs


Nature of the disease

  • Coccidiosis continues to be one of the disease problems for cattle producers. It is caused by microscopic, one-celled parasites, chiefly of the genus Eimeria. Twenty-one species of Eimeria have been reported in cattle. Only two, Eimeria bovis and Eimeria zuernii, are regularly associated with clinical infections in the field.

  • The disease is seen more commonly in calves six to nine months of age but it may occur in yearlings and adults.

  • Coccidiosis occurs most commonly in animals housed or confined in small areas contaminated with oocysts. Coccidiosis usually is sporadic during the wet seasons of the year, but may develop any time cattle are crowded together as animals confined in feedlots or calves brought together for weaning or crowding around a limited water source, which concentrates the hosts and parasites within a restricted area that may cause severe losses. Outbreaks usually occur within the first month of confinement.

  • The immunosuppressive effect of various stressors such as weaning and change of feed or severe weather or overcrowding and poor sanitation is important in precipitating clinical disease.

  • Coccidiosis can cause significant economic losses in cattle. Although most cattle are exposed to coccidia and infected, most of the infections are self-limiting and mild or asymptomatic. Economic losses from Coccidiosis may include weight loss with possible death in acute cases and growth retardation in the chronic form that may act as a stressor causing an increased susceptibility to other infections such as salmonellosis or Bovine Respiratory Disease.


History and Occurrence

  • Coccidiosis has a worldwide distribution


  • Bovine Coccidiosis is caused by unicellular protozoan parasites, chiefly of the genus Eimeria. Twenty-one species of Eimeria have been reported in cattle.

  • Of the species of Eimeria that infect cattle, E zuernii, E bovis, and E auburnensis are most often associated with clinical disease. Experimentally, other species have been shown to be mildly or moderately pathogenic.


  • Coccidiosis is commonly a disease of young cattle of all breeds (1-2 mos to 1 yr).

  • Coccidiosis is uncommon in adult cattle, but occasional cases and even epidemics do occur, especially those from one to two years.

  • Older cattle are often carriers of coccidia, and although they are immune, they continue to pass oocysts in their manure.


  • The fecal-oral route transmits coccidiosis from animal to animal. Infected fecal material contaminating feed, water, or soil serves as carriers of the oocyst for the susceptible animal to contract the disease by eating, drinking, or licking itself.

  • Calves become infected when placed on pastures or lots contaminated with sporulated oocysts from older cattle or other infected calves. Mature cattle may be infected when they are brought in from pastures and crowded into feedlots or barns.

  • Recovered animals continue to carry and excrete small numbers of oocysts

Key signs

  • The incubation period is 17-21 days. The severity of the disease depends on a number of factors including the number of oocysts eaten, the species of coccidia present and the age of the animal and stresses associated with management factors. The severity of clinical disease depends on the number of oocysts ingested. The more oocysts ingested the more severe the disease. Calves with concurrent infections (eg, coronavirus) may be more severely affected.

  • The most typical syndrome is chronic or subclinical disease in groups of growing animals. There is mild diarrhea and reduced growth rate, but not necessarily dysentery too. Calves may appear unthrifty and have soiled rear quarters. In lighter infections, cattle appear healthy and oocysts are present in normally formed feces, but feed efficiency may be reduced. Consequently, large numbers of oocysts accumulate on the ground and these infect susceptible calves when they are placed on the contaminated lots.

  • Clinical coccidiosis: Animals affected with clinical coccidiosis often show watery diarrhea and dysentry, with little or no blood, and the animal shows only slight discomfort for a few days. Severe infections are rare.

  • Severely affected cattle develop diarrhea, which consists of thin bloody fluid that may continue for > 1 wk, or thin feces with streaks or clots of blood, shreds of epithelium, and mucus. Tenesmus, dehydration, weight loss, depression, loss of appetite is common. They may develop a fever in the early stages. During the acute period, some cattle die; others die later from secondary complications (eg, pneumonia). Cattle that survive severe illness can have significant weight loss that is not quickly regained or can remain permanently stunted


  • Fecal staining of hindquarters and tissue pallor of the carcasses are common.

  • The pathogenic coccidia of cattle can damage the mucosa of the lower small intestine, cecum, and colon causing congestion, hemorrhagic enteritis, and thickening of the mucosa. Ulceration or sloughing of the mucosa may occur in severe cases.

  • The first-generation schizonts of E bovis appear as white macroscopic cyst-like bodies in the villi of the terminal ileum.



  • Diagnosis of clinical coccidiosis can be made from a combination of herd history, clinical signs, gross lesions at necropsy, and microscopic examination of faeces or scrapings of the intestinal mucosa at necropsy.

  • Diagnosis is by finding oocysts on fecal flotation, direct smear, or McMaster's technique.

  • An accurate way to diagnose coccidiosis at necropsy is to examine scrapings of the small intestine or colon for oocysts and merozoites. Merozoites can be looked for in direct smears; they do not float on the conventional concentrated sugar or salt solutions used for flotation of oocysts.

  • The presence of large numbers of oocysts can confirm the diagnosis, a count of 5000 oocysts per gram of faeces is considered significant and below this count do not usually suggest clinical disease but may indicate a potential source of severe infection with favorable environmental conditions.

  • Care should be taken in interpretation of oocyst counts since in severely affected diarrhoeic calves the main oocyst production phase may have passed or their numbers be misjudged due to the dilution factor of liquid faeces. Usually, diarrhea precedes the heavy discharge of oocysts by a day or two, and the diarrhea may continue after the oocyst discharge has returned to low levels. Therefore, it is not always possible to confirm a clinical diagnosis of coccidiosis by finding oocysts in the faeces. Certain coccidia may cause severe illness and even death before any oocysts have been produced. This occurs most often with Eimeria zuernii in calves. Consequently, failure to find oocysts in feces in a diarrhea disease does not necessarily mean the disease is not coccidiosis.

  • Differential diagnosis: Other conditions that should be considered and may resemble coccidiosis are salmonellosis, bovine virus diarrhea, malnutrition, toxins, or other intestinal parasites.


  • Cattle that recover from coccidiosis usually become immune to later infections, but they may continue to pass oocysts in the manure, thereby providing a source of infection for susceptible calves.

  • Although immunity against intestinal coccidiosis is attributed to both humoral and cell-mediated immune mechanisms but cellular immunity is more important in resistance against reinfection than humoral immunity.

  • Bovine coccidiosis is immunosuppressive and acts as a stressor causing an increased susceptibility to other infections such as salmonellosis or bovine respiratory disease.

  • The acquired immunity after infection is species specific and there is no cross immunity between species of coccidia.



  • In clinical coccidiosis, the clinical signs of the disease do not become noticeable until the disease is advanced and much of the invasion of intestinal mucosa has already occurred. Thus, treatment administered at this time can at best result in a lessening of the signs of coccidiosis. However, if drugs are given at an earlier stage of the disease, the clinical signs of infection can be largely or entirely prevented. The major benefits of the coccidiostats are through improved feed efficiency and rate of gain.

  • There are several anticoccidial drugs available that may be used. Outbreaks of coccidiosis in calves and feeder cattle may be handled by mass medication using sulfonamides, amprolium or monensin added to either the feed or the water. Drugs useful for treatment are not necessarily useful for prevention and vice versa,

  • Drugs that can be used for therapy of clinically affected animals include;
     -Sulfadimidine (sulfamerazine) 140 mg/kg BW /day for'3days orally.
     -Sulfamethazine 110 mg/kg BW daily for 5 days.
     -Sulfaquinoxaline 6 mg/lb BW /day for 3-5 days.
     -Amprolium: 10 mg/kg BW /day for 5 days or 65 mg/kg 6W one dose followed by
    -5 mg/kg for 16 more days in feed or water.

  • Drugs can be very useful in helping to prevent coccidiosis during periods when coccidiosis is likely to be a hazard and some of these are;
    • Amprolium 5 nig/kg BW/day for 21 days in feed
      Monensin (Rumensin®) 16.5-33 gm/tonne for 31 days or 100-360  mg/head/day. Rumensin is very toxic if mixed improperly.
    • Sulfadimidine (sulfamerazine) 35mg/kg BW /day for 15 days in feed.
    Lasalocid (Bovatec®) 1 mg/kg BW/day to a maximum of 360 mg/head/day.
    Decoquinate (Deccox®) 22.7 mg/100 Ib BW/day for 28 days.
    • Sulfonamides and chlortetracycline combination has given protection in calves (lambs).


Prevention and control measure

  • Good management practices play a critical role in the establishment of effective control programs. Because several days are required for sporulation, the oocyst stage in manure is the weakest link. Since moisture

  • Favors the development of parasites, correction of housing and ventilation deficiencies that reduce the moisture on pasture will decrease contamination.

  • Excessive moisture should be drained from the pens and replaced with ample dry bedding and pastures should be well-drained.

  • Cattle, especially calves, should not be fed directly on the ground where manure can contaminate the feed and the drinking water should be protected from contamination by raising watering troughs above the ground.

  • In these areas where cattle congregate, overgrazing should be avoided and grazing should be kept to a minimum on lush grass along the edges of ponds.

  • Infected animals should be isolated and treated to avoid exposure to other cattle


  1. El Sawalhy, A. A. (1999): "Veterinary Infectious Diseases" 2nd Edit. Ahram Distribution Agency, Egypt.