Necrotic enteritis in poultry

Necrotic enteritis is a bacterial disease of the intestinal tract of the chicken. It is an important disease, and is usually seen in birds of 4 weeks of age or older. It is quite a common disease. There are sudden deaths that are caused by severe necrosis (death) of the inner intestinal lining. Mortality in untreated flocks can reach 10% or more, and is most common in broilers. The disease is often established after an outbreak of coccidiosis. The author has come across severe necrotic enteritis in the caeca of young broiler chicks in cases of caecal coccidiosis, caused by E.imeria ten ella (see 'caecal coccidiosis').

Cause

Necrotic enteritis is caused by the growth of a bacterium called Clostridium perfringens (type A and C) in the

caeca and large intestine. Afterwards, this organism migrates to the small intestine where it produces toxins.

These toxins cause death of cells lining the intestine and are responsible for the characteristic changes of necrotic enteritis. Contaminated feed and litter act as sources of infection.

Predisposing Factors

These are those factors which make the bird easily prone to infection. Necrotic enteritis is produced when there is damage to the inner intestinal lining. This allows the bacteria to grow and produce toxins which damage the intestine and cause death. The predisposing factors of necrotic enteritis include:

I. Outbreaks of coccidiosis, especially mild and subclinical.

2. Partial impaction of the lower intestine due to litter and/or grain ingested without the provision of insoluble grit.

3. Rapid changes in feed components.

4. Removal of the antibiotic growth promoters from the feed results in a significant increase in the incidence of necrotic enteritis. This is because of their direct effect on control of the causative organism Clostridium perfringens. However, the most important predisposing cause of necrotic enteritis, both in broilers and layers, appears to be coccidiosis. Therefore, every outbreak of necrotic enteritis must be examined for coccidiosis, and if present, must be treated. Likewise, in every outbreak of coccidiosis, necrotic enteritis must be ruled out, and if present, must be treated.

Symptoms

I. There may be no symptoms. Clinical disease is very short, and often, birds are just found dead.

2. The birds may show depression (Fig. 63), loss of appetite, unwillingness to move, diarrhoea, ruffled feathers, and increasing mortality.

Postmortem Findings

I. Postmortem findings are usually confined to the middle part of the small intestine. The intestine is

distended and filled with a foul-smelling brown fluid. The inner intestinal lining is covered by a brownish membrane .

2. Similar changes in the caeca may also occur .

3. The small intestine is greatly thickened due to extensive velvet-like (looking like silk) necrosis (death) of the intestinal lining (mucosal lining) .

4. The intestinal lining (mucosa) is covered by a loose to tight yellow or green layer (Fig. 64, 65) that may be deeply cracked. Spots or small patches of blood may occur, but haemorrhage is not a feature.

Diagnosis

Diagnosis can be made from the characteristic postmortem findings.

Treatment

A number of antibiotics (amoxycillin, ampicillin, chloramphenicol, ciprofloxacin, doxycycline, neomycin,

erythromycin, furazolidone) given in drinking water may be helpful in treating the condition. Others (lincomycin,

tylosin, bacitracin, and furazolidone) in feed reduce the number of organisms shed in the faeces.

Control

I. Identify the predisposing factor and make sure that it is controlled. Give particular attention to coccidiosis and Gumboro disease.

2. Drugs which have an effect on the causative organism such as lincomycin, ampicillin, penicillin, virginiamycin, bacitracin, furazolidone and others may be included in the feed.

3. Probiotics reduce the severity of necrotic enteritis.

4. Anticoccidial drugs, e.g., the ionophores, in the feed are also helpful.

5. Good management and sanitation practices should be followed.

Fig.