Kvet Forum
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Coccidial species are as follows:
- Cattle: Eimeria zuernii, E. bovis, and E. ellipsoidalis; E. alabamensis, E. auburnensis, and E. wyomingensis
- Sheep: E. arloingi A (ovina), E. weybridgenis (E. arloingi B), E. crandallis, E. ahsata, and E. ovinoidalis (previously known as E. ninakohlyakimovae), and E. gilruthi
- Goats: E. arloingi, E. faurei, and E. gilruthi, E. caprovina, E. ninakohlyakimovae and E. christenseni
- Pigs: Isospora suis; numerous species of Eimeria (no clinical importance), including E. debliecki, E. neodebliecki, E. polita, E. perminuta, E. scabra, and E. suis
- Horses and donkeys: E. leuckarti (ubiquitous, but of no clinical significance)
Coccidiosis is most frequently seen in livestock animals housed or confined in small areas contaminated with oocysts. Coccidia are usually host specific, and there is no cross-immunity between species of coccidia. Clinical disease is common in cattle and sheep. Coccidiosis causing diarrhea in newborn piglets is a major problem in some swine herds.
Coccidiosis is most common in young animals, with a seasonal incidence that may be associated with the time young calves and lambs are brought together for weaning or moved into feedlots or fed in small areas.
Epidemiology
Adult Cattle
Coccidiosis is uncommon in adult cattle, but occasional cases and even epidemics can occur, sometimes in dairy cows that have calved 6 to 8 weeks earlier. Older animals can serve as a source of infection for younger calves in the herd.
Sheep and Goats
Coccidiosis can be a major problem in housed lambs. Disease can occur commonly in lambs following introduction into a feedlot situation with problems of overcrowding and other stressors. Lambs with no previous exposure to coccidia are highly susceptible to infection.
Coccidiosis is one of the most important diseases of goats kept in large numbers under intensive management conditions. The prevalence of infection may be as high as 100% in some goat farms. Kids are the major source of pasture contamination, and newly weaned kids can have high oocyst counts.
Pigs
Isospora suis is a common parasite on pig farms. It can be found in 90% of herds and 25% to 50% of litters. The prevalence may be higher when piglets and their sows are kept on solid concrete floors. Rotavirus infection may occur concurrently with I. suis infection in piglets of 1 to 3 weeks of age, which may be important causes of steatorrhea or unspecified diarrhea, known as milk scour, white scour, or 3-week diarrhea. I. suis infection commonly occurs in large pig producing farming systems; the highest rate of infection occurs in litters at 3 to 4 weeks of age.
Transmission
The source of infection is the feces of clinically affected or carrier animals, and infection is acquired by ingestion of feed and water contaminated with sporulated coccidial oocysts or by licking the hair coat contaminated with such oocysts.
Unsporulated oocysts are passed in the feces and require suitable environmental conditions to sporulate. Moist, temperate, or cool conditions favor sporulation, whereas high temperatures and dryness impede it.
Ingestion of the sporulated oocysts results in infection. Large numbers of oocysts usually arise by continual reinfection and a buildup of the degree of environmental contamination. This is most common when calves or lambs are crowded into small pens or confined in feedlots. Lambs can become infected within a few weeks after birth from lambing grounds heavily contaminated by the ewes. Overcrowding of animals on irrigated pastures, or around surface water holes in drought conditions, may also lead to heavy infections and disease.
Young calves and lambs on pasture may shed large numbers of oocysts for long periods, which results in a buildup of coccidial populations.
Clinical Findings
Cattle and Sheep
mild fever may occur in the early stages, but in most clinical cases body temperature is normal or subnormal. The first sign of clinical coccidiosis is the sudden onset of diarrhea with foul-smelling, fluid feces containing mucus and/or blood. Blood may appear as a dark, tarry staining of the feces or as streaks or clots, or the evacuation may consist entirely of large clots of fresh, red blood.
The perineum and tail are commonly smudged with bloodstained feces. Severe straining is characteristic, often accompanied by the passage of feces, and rectal prolapse may occur. The degree of hemorrhagic anemia is variable, depending on the amount of blood lost, and in most naturally acquired cases in calves anemia is not a feature. Nonetheless, in exceptional cases, anemia can occur with pale mucosa, weakness, staggering, and dyspnea. Dehydration is common, but is not usually severe if affected animals continue to drink water.
Inappetence is common and, in exceptional cases, there may be anorexia. The course of the disease is usually 5 to 6 days, but some animals undergo a long convalescent period in which feed consumption and body weight gains are reduced. Severely affected calves do not rapidly regain body weight losses that occurred during the clinical phase of the disease. In mild cases of coccidiosis, diarrhea and reduced growth rate may occur. Subclinical cases may show inferior growth rates and chronic anemia only.
Lambs
Coccidiosis in lambs is similar to that in calves, but with much less dysentery. In groups of lambs raised and fed under intensive conditions, inferior growth rate, diarrhea (with or without blood), low-grade abdominal pain, gradual onset of weakness, inappetence, fleece damage, mild fever, recumbency, emaciation, or death with a course of 1 to 3 weeks is seen. The diarrhea may escape cursory examination, but clinical examination of affected lambs reveals a perineum smudged with feces, and soft feces in the rectum. Lambs moved directly from range pasture to a feedlot and with little or no previous exposure to coccidia often develop acute disease with a high morbidity and case fatality rate.
Piglets
In piglets, severe outbreaks of coccidiosis occur between 5 and 15 days of age, irrespective of time of the year. Anorexia and depression are common. There is profuse diarrhea; the feces are yellow, watery, and sometimes appear foamy. The diarrhea may persist for several days when dehydration and unthriftiness are obvious. Although affected piglets continue to suck, they become dehydrated and lose weight. Vomiting may occur. Entire litters may be affected, and the case fatality rate may reach 20%. The disease may persist in a herd for several weeks or months, particularly where a continuous farrowing program is used.
Treatment
Sulfadimidine is used widely empirically for the treatment of acute coccidiosis in calves. Amprolium is also used for treatment, and there may be a beneficial effect in terms of increased body weight gains and feed consumption compared to animals left to recover spontaneously.
Triazinetriones are effective against the asexual and sexual stages of experimental I. suis infection in piglets and are most effective before the onset of clinical signs.
Control
The population density of animals in pens should be reduced. All feed and water supplies should be elevated from the ground to avoid fecal contamination. Feeding cattle on the ground should be avoided if possible, particularly when overcrowding is a problem.
Lambing pens should be kept dry, cleaned out frequently, and bedding disposed of, such that oocysts do not have time to sporulate and become infective.1 All measures that minimize the amount of fecal contamination of hair coats and fleece should be practiced.