THE MERCK VETERINARY MANUAL
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Coccidiosis of Pigs

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Eight species of Eimeria and 1 of Isospora infect pigs in the North America. Piglets 5–15 days old are characteristically infected with only I suis, which produces enteritis and diarrhea. These agents must be differentiated from viruses, bacteria, and helminths that also cause scours in neonatal pigs.

I suis is prevalent in neonatal pigs. Infection is characterized by a watery or greasy diarrhea, usually yellowish to white and foul smelling. Piglets may appear weak, dehydrated, and undersized; weight gains are depressed, and sometimes piglets die. A contributing factor to mortality is that piglets become covered with diarrheic feces and stay damp. Oocysts are usually shed in the feces and can be identified by their size, shape, and sporulation characteristics; however, in peracute infections, diagnosis must be based on finding stages of the parasite in impression smears or histologic sections of the small intestine because pigs can die before oocysts are formed. In severely affected piglets, histologic lesions confined to the jejunum and ileum are characterized by villous atrophy, blunting of villi, focal ulceration, and fibrinonecrotic enteritis with parasite stages in epithelial cells.

Preventive control by feeding anticoccidials to sows from 2 wk before farrowing through lactation or to neonatal pigs from birth to weaning has been reported; however, effectiveness of the latter has not been confirmed. Although the sow is a logical source of infection for piglets, this has not been well documented. Thorough removal of feces and disinfection of farrowing facilities between litters greatly decreases infection. Piglets that recover from infection are highly resistant to reinfection.

Although less commonly associated with clinical coccidiosis, E debliecki, E neodebliecki, E scabra, and E spinosa have been found in pigs ∼1–3 mo old with diarrhea. Illness may last 7–10 days, with pigs remaining unthrifty.

Treatment of coccidiosis may include sulfamethazine in drinking water. The control of coccidiosis in newborn piglets infected with I suis has been unreliable. The use of coccidiostats in the feed of the sow for several days or a few weeks before and after farrowing has been recommended and used in the field, but the results are variable. Amprolium and monensin are ineffective for the prevention of experimental coccidiosis in piglets. A control program designed to decrease the number of oocysts has been recommended and consists of proper cleaning, disinfection, and steam cleaning of the farrowing housing. Amprolium (25% feed grade) at the rate of 10 kg/tonne of sows' feed started 1 wk before farrowing and continued until the piglets are 3 wk of age has been recommended, but the results are unsatisfactory. A single dose of toltrazuril (20 mg/kg, PO) decreased oocyst excretion, the incidence of diarrhea, and weight gain impairment in piglets with experimentally induced coccidiosis. Diclazuril (5 mg/kg) is being investigated as an oral anticoccidial in piglets.

Last full review/revision March 2012 by Peter D. Constable, BVSc (Hons), MS, PhD, DACVIM

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