Necrotic Enteritis: A Devastating Disease Caused by C. perfringens
What is Necrotic Enteritis?
The bacterium Clostridium perfringens causes necrotic enteritis (NE). It is a type of gastrointestinal condition called enterotoxemia. NE has a single causative agent and thus is a much simpler disease than bacterial enteritis, which it is commonly confused with. Although many of the contributory factors are the same the diseases are quite different and necrotic enteritis is less complex than its bacterial counterpart.
C. perfringens can infect many species. However, it causes different types of enterotoxemias in sheep, goats, cattle, pigs and chickens among others. C. perfringens is a gram positive, spore-forming, rod-shaped bacterium. It is found nearly everywhere in an animal’s environment, usually present in the feed, bedding, faeces, dust and so is typically a commensal bacteria in chickens and turkeys. Therefore, it is a very difficult bacterium to remove from the environment and animals. That is, unless they are raised from SPF eggs (in the case of chickens) and then brought up in a contained facility with good biosecurity. While this is an option, it is usually unrealistic for the large majority of animal keepers.
Considering C. perfringens is omnipresent, NE happens relatively rarely, due to the other risk factors required for its emergence. Necrotic Enteritis Beta toxin (NetB)-producing strains cause NE, in combination with a change in the intestinal mucosa due to coccidiosis, worms, mycotoxicosis, infection with other bacteria. Therefore the disease is multifactorial and cannot emerge without the presence of the relevant bacteria and a cause for change in the gut microbiota. NetB toxins cause severe damage to the small intestine and liver, often consequently ending in mortality. A single clone virulent NetB producing strain will outcompete other commensal Clostridia in the gut, and so cause severe necrosis by targeting tight junctions between cells.
What are the clinical signs of necrotic enteritis?
- The disease can be acute or chronic
- Intestinal necrosis, inflammation and haemorrhage
- Liver lesions (cholangiohepatitis)
- Sudden increase in mortality within the flock
- Depression – antisocial and inactive behaviour for example
- Ruffled feathers
- “Turkish towel” appearing mucosal intestinal membrane
- Foul smelling intestinal fluid
How do I diagnose NE?
There are a few options to detect a C. perfringens infection during an outbreak:
- Post-mortem assessment of gross lesions in the small intestine
- Gram stained smear to determine if gram positive rods are present
- Isolation of large numbers of C. perfringens and then culture with differential media
Of course, usually the disease is acute and serious and therefore necropsies may be the route of choice, by an experienced vet.
How can I get prevent and treat NE?
You can reduce the risk of coccidiosis, which then can lead to necrotic enteritis, by giving feed containing anticoccidials and vaccinating your animals. You can also minimise any changes to the gut flora or any stress to the gut by avoiding radical changes to the diet, ensuring amounts of cereals containing non-starch polysaccharides (NSP) like wheat, barley, or rye and fishmeal in the diet are low (not applicable to all animals). Furthermore the use of pre and probiotics for healthy maintenance of the gut flora and reducing the change of NetB+ C perfringens outcompeting other commensals.
There is a range of antibiotics licensed for C perfringens. Users must ensure that they use them correctly, due to the ever-increasing pressure of antibiotic resistance.
VetWorks Poultry Gut Health Training, Belgium (Sep 2018)
Shojadoost, et al. Vet Res 43, 74 (2012)