Interaction of Eimeria with other poultry diseases: Necrotic Enteritis

In the field, necrotic enteritis and coccidiosis infections usually go hand in hand. Necrotic enteritis is a bacterial infection of poultry caused by Clostridium perfringens and lesions usually localize around the small intestine (1).  Clostridium perfringens is a bacterium that can readily be found anywhere, including among the naturally present intestinal flora of chickens (2).  Development of necrotic enteritis requires favourable intestinal conditions such as a weakened intestinal barrier produced by predisposing factors such as diet composition and intestinal cell damage (e.g. caused by coccidiosis) (3).

This website will focus on the relationship between coccidiosis and necrotic enteritis. For information on the other potential predisposing factors for development of necrotic enteritis refer to:

Van Immerseel, F., J. De Buck, F. Pasmans, G. Huyghbaert, F. Haesebrouck and R. Ducatelle, 2004. Clostridium perfringens in poultry: An emerging threat for animal and public health. Avian Pathol., 33: 537-549.

Clostridium perfringens lacks about 13 essential amino acids that can be acquired from the host (2).  Bacteria can access these required amino acids from the host in many ways such as leakage of proteins (made up of many amino acids) into the intestine after intestinal cell damage or from mucous (made up of mostly glycoproteins and water) lining the intestinal tract (3).  Consequently, Eimeria species that damage cells of the small intestine as well as cause an increase in mucous production during infection, specifically E. maxima, E. acervulina, E. necatrix or E. brunetti, can predispose birds to subsequent necrotic enteritis (3). Other Eimeria species induce excess mucous production in the small intestine (E. praecox and E. mitis) but they induce minimal intestinal lesions and therefore may be less associated with development of necrotic enteritis.

Simplified illustration of intestine

Figure 1. Simplified illustration of possible ways Clostridium perfringens can access required amino acids from a chicken intestinal tract with coccidiosis. The healthy gastrointestinal tract consists of a mucus and epithelial layer as well as a basal lamina to act as a barrier between the indigenous microbiota, lumen, and lamina propria, respectively (A). Coccidiosis can predispose chickens to necrotic enteritis outbreaks (B). During coccidiosis lesions are caused during the asexual cycle usually when the motile asexual stage exits the cell, breaks the intestinal cell membrane [1, 2] and kills the intestinal cell [3]. Clostridium perfringens usually occurs in the small intestine and requires access to amino acids. Eimeria species that damage cells of the small intestine [1-3], causing leakage of proteins, and cause and increase in mucous production [4] permits Clostridium perfringens replication [5].

Coccidial lesions may have formed and partially or completely resolved by the time clinical necrotic enteritis arises. Thus, a lack of coccidial lesions concurrent with necrotic enteritis does not mean that a coccidial infection did not occur (3).  However, necrotic enteritis is unlikely to predispose a bird to coccidiosis because clostridial lesions produce an environment that is unsuitable for asexual development of Eimeria species (3).

Necrotic enteritis is considered an illness mainly of broiler birds between two and six weeks of age (3) but has also been noted in commercial layer replacement pullets at 16 weeks of age or later (4).  While managing coccidiosis prior to these ages may not eliminate the potential for a necrotic enteritis outbreak, it can help to limit one of the predisposing factors. 

For further reading on the relationship between coccidiosis and necrotic enteritis please refer to:

Williams, R.B., 2005. Intercurrent coccidiosis and necrotic enteritis of chickens: rational, integrated disease management by maintenance of gut integrity. Avian Pathol., 34: 159-180.


1. Timbermont, L., F. Haesebrouck, R. Ducatelle, and F. Van Immerseel. Necrotic enteritis in broilers: an updated review on the pathogenesis. Avian Pathology 40:341-347. 2011.

2. Cooper, K.K., and J.G. Songer. Necrotic enteritis in chickens: a paradigm of enteric infection by Clostridium perfringens type A. Anaerobe 15:55-60. 2009.

3. Williams, R.B. Intercurrent coccidiosis and necrotic enteritis of chickens: rational, integrated disease management by maintenance of gut integrity. Avian Pathology 34:159-180. 2005.

4. Frame, D.D., and A.A. Bickford. An outbreak of coccidiosis and necrotic enteritis in 16-week-old cage-reared layer replacement pullets. Avian Diseases 30:601-602. 1986.