Prevention and Effective Treatment of Coccidiosis in Pigs

Coccidiosis (Pigs) is a parasitic disease caused by Isospora suis. Although the disease can occur in pigs of all ages, it is most commonly observed in suckling piglets, particularly those under two weeks of age. It is prevalent in pig farms with high stocking densities and poor hygienic conditions.
More than nine species of Eimeria and one species of Isospora have been identified as causative agents of coccidiosis in pigs. Piglets aged 5–15 days are most commonly infected with I. suis, which causes enteritis and diarrhea.
Coccidiosis is a common disease in newborn piglets. The characteristic symptom is watery or semi-solid diarrhea, usually milky white, then turning yellow and foul-smelling. Piglets may exhibit symptoms such as weakness, dehydration, stunted growth, reduced weight gain, and may die. A contributing factor to the high mortality rate in piglets is their constant wetness and fecal contamination from diarrhea.
In this article, the Fivevet Field Technical Department shares the causes, clinical signs, lesions, diagnosis, prevention, and control of coccidiosis in pigs.

1. Causes of Coccidiosis in Pigs
The primary causative agent of coccidiosis in piglets is Isospora suis. Most Eimeria species are of low pathogenicity (accounting for approximately 5% of infections) or are not found in this age group.
Newborn piglets become infected with Isospora suis through contact with a contaminated environment. The initial invasion occurs in the proximal small intestine. Isospora suis undergoes three generations of asexual reproduction (merogony) followed by one generation of sexual reproduction (gametogony). Successive generations of meronts develop in the more distal portions of the small intestine before invading the cecum and colon. Third-generation meronts are produced within 4–6 days, and oocysts first appear in the feces around Day 5. Oocyst shedding continues until approximately Days 8–9, with a second shedding period occurring between Days 11 and 14. Excreted oocysts can become infective within 12–24 hours at temperatures of 25–35°C and are capable of surviving in the environment for more than 10 months.
In weaned piglets and adult pigs, coccidiosis is commonly associated with multiple Eimeria species, including E. debliecki, E. neodebliecki, E. perminuta, E. polita, E. porci, E. scabra, E. spinosa, and E. suis. Many Eimeria species have a localized geographic distribution.
Eimeria debliecki primarily infects the small intestine, with less extensive involvement of the colon. The prepatent period is approximately 7 days. Eimeria neodebliecki affects the mid-jejunum, with a prepatent period of approximately 6–8 days.
In piglets, infection initially occurs in the upper small intestine and gradually extends to the lower half of the small intestine as the parasite progresses through its developmental stages. Villous atrophy develops approximately 5 days after infection and resolves spontaneously within 10–14 days. In older pigs, the distribution and severity of intestinal lesions vary depending on the Eimeria species involved.
2. Transmission of Coccidiosis in Pigs
Infection with Isospora suis occurs in piglets under all production systems, ranging from intensive indoor farming to outdoor production systems.
- Piglets are primarily exposed to oocysts shed by other infected piglets in contaminated farrowing and nursing pens. Disease severity is greater when infection occurs early in life. Thorough cleaning of slatted floors can significantly reduce or prevent infection.

- Although sows rarely shed Isospora suis oocysts, they serve as important reservoirs and sources of transmission for Eimeria spp. to their offspring. Older pigs may also acquire infection from sows, and with E. scabra, clinical disease may occur from 4–8 weeks of age onwards. Infection may be introduced into previously uninfected herds through wild boars or newly introduced replacement gilts.
Following exposure to Isospora suis, pigs develop strong active immunity. Likewise, exposure to Eimeria species induces a robust protective immune response. In adult pigs, immunity is generally maintained and boosted through repeated low-level natural exposure. However, sows may exhibit periparturient oocyst shedding, releasing oocysts into the environment during the period immediately before and after farrowing.
3. Clinical Signs of Coccidiosis in Pigs
- In piglets:
The small intestine is typically flaccid and contains intestinal contents ranging from watery fluid to creamy, semi-solid material. Gross lesions include thickening of the intestinal wall, with necrosis of the mucosa confined to the small intestine, particularly the jejunum and ileum. Affected piglets are commonly emaciated and dehydrated. Histopathological examination reveals large numbers of merozoites and male and female gametocytes within the intestinal wall. Microscopic lesions include villous atrophy, villous blunting, focal ulceration, increased mitotic activity in the intestinal crypt epithelium, and, in severe cases, fibrinonecrotic enteritis with developmental stages of coccidia present in the intestinal epithelium.
- In adult pigs:
Clinical disease is generally mild. Affected pigs typically develop watery diarrhea, and the feces may contain foam or mucus, accompanied by weight loss. These clinical signs usually appear 9-12 days after infection. Although most pigs recover, some may remain stunted and exhibit poor growth performance.
4. Lesions of Coccidiosis in Pigs
- In piglets:
The small intestine is typically flaccid and contains intestinal contents ranging from watery fluid to creamy, semi-solid material. Gross lesions include thickening of the intestinal wall, with mucosal necrosis confined to the jejunum and ileum. Affected piglets are commonly emaciated and dehydrated. Histopathological examination reveals large numbers of merozoites and both male and female gametocytes within the intestinal wall. Microscopic lesions include villous atrophy, villous blunting, focal ulceration, increased mitotic activity of the intestinal crypt epithelium, and, in severe cases, fibrinonecrotic enteritis with developmental stages of coccidia present in the intestinal epithelium.
- In adult pigs:
Localized inflammatory lesions with desquamation of the intestinal mucosa are observed in the jejunum and ileum. Histologically, moderate villous atrophy is present, accompanied by fibrinonecrotic debris at the tips of the intestinal villi.
5. Diagnosis of Coccidiosis in Pigs
Coccidiosis in pigs can be diagnosed based on clinical signs, the age of affected animals, characteristic intestinal lesions, and laboratory detection of coccidial oocysts in fecal samples.
- Coccidial oocysts can be detected using saturated sodium chloride or glucose flotation solutions. Oocysts can be identified based on their size, morphology, and sporulation characteristics. In piglets that die before oocyst shedding occurs, stained mucosal smears prepared from the jejunum and ileum can provide a rapid diagnosis.
- Fluorescent antibody assays and polymerase chain reaction (PCR) assays may also be used for the diagnosis of coccidiosis.
- Necropsy findings can provide valuable support for the diagnosis of coccidiosis. Cytological smears prepared from affected intestinal areas reveal the developmental stages of coccidia. Histopathological examination of the distal small intestine demonstrates characteristic lesions together with both the asexual (merogony) and sexual (gametogony) stages of the coccidial life cycle.
Coccidiosis should be differentiated from other causes of diarrhea in piglets, including bacterial and viral infections, digestive disorders associated with nutritional or management factors, and inappropriate housing conditions.
6. Prevention and Treatment of Coccidiosis in Pigs

- Farrowing pens should be thoroughly cleaned and disinfected, with an adequate downtime between batches before sows are moved in for farrowing.
- Maintain pig housing in a clean, dry, and warm condition. Apply disinfectants regularly, such as spraying Five-Perkon 3S once weekly, or spread hydrated lime directly on the floor to reduce environmental contamination and eliminate disease-causing pathogens.
- Prevention: Five-Cox 5% 1 ml/head and inject Five-Fe.B12 when piglets are 3 days old.
- Effective treatment for coccidiosis: Five-Cox 5% 1 ml/2.5 kg, used continuously for 2–3 days.
Use in combination with Five-Enzym, Five-Prozyme 5 Way, and Five-Orgacid to promote beneficial gut microbiota, supply essential vitamins, improve digestion and nutrient utilization, and maintain gastrointestinal health.

To minimize losses caused by coccidiosis, farmers should prioritize proper hygiene in farrowing pens, perform routine disinfection, maintain a clean, dry, and warm environment, and implement preventive measures for piglets from the first few days after birth. When piglets show signs of diarrhea suspected to be caused by coccidiosis, early detection, prompt and appropriate treatment, and supportive care are essential to promote rapid recovery and reduce disease impact.
This article was prepared by the Field Technical Department of Central Veterinary Medicine Joint Stock Company No. 5 (Fivevet).
The technical information presented in this article is referenced from the MSD Veterinary Manual: Coccidiosis of Pigs.
Frequently Asked Questions (FAQs)
1. Which age group is most commonly affected by coccidiosis in pigs?
Coccidiosis most commonly affects suckling piglets, particularly those 5–15 days of age.
2. What are the typical clinical signs of coccidiosis in piglets?
Typical clinical signs include milky white or yellow diarrhea with a foul odor, accompanied by weakness, dehydration, emaciation, and poor growth.
3. Is coccidiosis contagious in pigs?
Yes. Pigs become infected primarily by ingesting coccidial oocysts present in contaminated feces, pen floors, or the surrounding environment.
4. How can coccidiosis be prevented in piglets?
Effective prevention includes thoroughly cleaning and disinfecting farrowing pens, maintaining a clean, dry, and warm environment, allowing adequate pen downtime between farrowing batches, and implementing preventive measures for piglets during the susceptible period.
5. Can coccidiosis cause death in piglets?
Yes. In severe cases, piglets may die as a result of prolonged diarrhea, dehydration, debilitation, and severe intestinal damage.