Coccidiosis - an under-diagnosed cause of scouring in piglets

By Jake Waddilove, MA, VetMB, MRCVS - This article from DAHS looks at Coccidiosis in swine, which the author states is an often under-diagnosed cause of scouring in piglets.
calendar icon 12 March 2004
clock icon 6 minute read
  • Coccidiosis is a very common cause of scouring in piglets
  • It is difficult to diagnose.
  • It can easily cause significant production losses.
  • Control is mainly based on killing oocysts in the environment.
  • This is not achieved by conventional means and requires the specialist disinfectant OO-Cide™ (DAHS).
  • The other part of control is by treatment of piglets with toltrazuril.


Coccidiosis is a piglet scour usually occurring between 8 and 15 days of age. It is characterised by moderate diarrhoea of variable consistency, which is poorly responsive to antibiotic therapy. The condition in young piglets is caused by Isospora suis. Although other forms of coccidia occur in pigs in some parts of the world, this is the most important and the one we will concentrate on here.

It is a scour which is frequently under diagnosed. It is extremely common as is well illustrated by research in Germany showing that 83% of farms there were affected by Isospora suis and that up to 48.2% of litters on these farms were infected1. Subclinical infection frequently is not diagnosed. Failure to recognise clinical or subclinical infection leads to increased farrowing house mortality, poorer weaning condition and hence increased post-weaning problems.


The coccidial egg, or oocyst, infects young piglets by mouth. Relatively heavy infections are needed to cause disease. After infection the organisms move down to the small intestine where they invade the gut wall and undergo a complexed life cycle. They emerge from the wall 5-9 days and again 11-14 days after infection. It is this emergence from the gut wall which gives rise to scouring.

Clinical signs of Coccidiosis

Scour tends to occur in individuals from about 6 days, but most of the litter scour at 8-10 days. There is variation in severity of scour throughout the litter. Scour ranges from white to pasty cream faeces, through a yellowy scour onto a yellowy watery scour. Sometimes there are yellow-white clots in the more watery scours. Piglets tend to be poorer and hairy. They grow more slowly than their litter mates. Mortality is not usually high, but acute cases have been reported with 20% mortality. In the less severe cases the economic losses are mainly due to poor growth rates. One of the real characteristics of the condition is its poor response to antibiotics.

Many people will have seen the above scour and attributed it to a nutritional or viral cause. The situation can also be complicated by secondary agents such as E. Coli and rotavirus. It has been shown that coccidiosis facilitates bacterial invasion of the gut and so secondary infections are common2. Chronic Clostridial infections and low grade coccidiosis can co-exist.


Diagnosis is not easy, especially in less severe and subclinical outbreaks. It is based on clinical signs and laboratory tests plus response to treatment with toltrazuril (Baycox – Bayer).

Laboratory tests can provide a definite diagnosis. Coccidial oocysts can occasionally be seen in faeces but usually after clinical signs have decreased. To get a real diagnosis live affected piglets at the beginning of scour need to be submitted to a laboratory. Postmortems are frequently unremarkable, with a low grade enteritis. Histological examination provides the definitive diagnosis, but freshly fixed specimens are needed. Even then confirmation of coccidiosis may take repeated post-mortems.

Important control facts

To control coccidiosis there are various facts we need to consider.

  • For significant disease to occur piglets need to be infected with relatively high numbers of oocysts.

  • Oocysts survive very well in the farrowing house environment. They are resistant to drying and nearly all disinfectants.

  • Infection from the sow plays only a very small part in the development of disease.

  • Most piglets are infected by oocysts carried over from previous litters.

  • Once the piglet has started scouring the damage to its gut wall is already done and hence treatment will not work well.


Effective control will be based on controlling challenge to the piglets, and preventing any infection which occurs from becoming established in the gut wall.

  • Medication of sows. Amprolium and monensin have been used to reduce challenge, but as the sow only plays a small part in building up the challenge this medication is not so important and is frequently not done.

  • Prevention of carry over of oocysts from previous batches is vital. Note that these are very resistant. Such heroic measures as flame guns or steam cleaning for a long period have been described. The universally successful disinfectant which is highly effective against oocysts is Oocide™ (DAHS). In most cases this is the most important part of controlling coccidiosis. If houses are thoroughly cleaned with this product coccidiosis is often controlled with no other measures.

  • Control of rapid multiplication in infected piglets can be achieved by early and sometimes repeated treatment of piglets.

  • The best product for control in piglets is toltrazuril (Baycox- Bayer). This needs to be given prior to the time that coccidial oocysts mature and invade the gut wall. It is traditionally given at 3-4 days at a dose of 10-20mg/kg. In farms which experience a delayed problem it can be repeated at 10 days. If it is given after scour has started the response is much poorer.

  • How long does toltrazuril treatment need to continue? Due to resistant nature of the oocysts it could be permanent unless environmental build-up is controlled. This depends on hygiene. Following thorough disinfection with OO-Cide™ for two cycles most units will be able to stop treatment. Then prevent recurrence by disinfecting farrowing houses with OO-Cide™ twice yearly.

  • Improve biosecurity in farrowing houses, especially when moving between pens and houses. Disinfect equipment and boots when moving and do not share equipment between houses.


1. Neistrath, M. et al 2002. The role of Isospora suis as a Pathogen in Conventional Piglet Production in Germany. Journal of Veterinary Medicine 49, 176.
2. Jarvinen, J.A. 1993. Neonatal porcine Coccidiosis facilitates bacterial invasion. Proc 38th American Association of Veterinary Parasitologists.

Further information

For further information, visit the Coccidiosis section in our Quick Disease Guide.

Source: DAHS - March 2004

OO-Cide is not available in the USA
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