Necrotic Enteritis in the Post-AGP Era: A Complex Multifactorial Challenge

Necrotic Enteritis in the Post-AGP Era: A Complex Multifactorial Challenge

The restriction on antibiotic growth promoters (AGPs) in the broiler industry has led to a significant resurgence of enteric diseases, particularly necrotic enteritis (NE). This complex disease, estimated to cost the global industry USD 6 billion annually, requires a deeper understanding to develop effective control strategies. A recent review by Shahna Fathima, Walid Ghazi Al Hakeem, Revathi Shanmugasundaram, and Ramesh K. Selvaraj, published in Microorganisms (2022, 10, 1958. https://doi.org/10.3390/microorganisms10101958), synthesizes the current knowledge on the pathogen, pathogenesis, and prevention of NE.

For producers and professionals, the review reinforces that NE is a multifactorial issue. The proliferation of Clostridium perfringens is often preceded by one or more predisposing factors. These include:

Coccidiosis: There is a strong association between NE and coccidiosis, as intestinal damage from Eimeria supports the growth of C. perfringens.
Mycotoxins: Contaminants such as deoxynivalenol and fumonisins can disrupt the intestinal epithelium's structure and function, predisposing birds to NE.
Immunosuppression: Viral infections, including Marek’s disease, chicken infectious anemia, and infectious bursal disease, can alter the bird's immune status and increase susceptibility.
Management: Factors like high stocking density have been associated with a significantly higher number of C. perfringens in the ceca.

For academics and key opinion leaders, the review highlights a critical debate: the uncertainty surrounding the primary virulence factors. While alpha-toxin, beta-toxin, and the NetB toxin are considered principal contributors, their precise roles are controversial. The review points to "inconsistencies" regarding alpha-toxin, noting that mutant strains lacking the toxin were still capable of inducing NE lesions. Similarly, while the NetB toxin was a major discovery, the review notes conflicting studies. One assessment found that 41.7% of C. perfringens isolates from chickens with NE were NetB-negative, while other isolates from healthy chickens were found to be NetB-positive. The authors state, "Hence, it is still unclear and controversial as to which toxin is the cause of NE".

This gap in understanding is a significant hurdle. The review concludes that while research into antibiotic alternatives (such as immune modulation and nutritional manipulation) has intensified, the currently available options are not as effective as antibiotics in controlling NE. A greater understanding of the pathogenesis and true virulence factors is required to develop a new generation of effective supplements and control strategies.

Given the ongoing controversy over which C. perfringens toxin is the primary driver of NE, where should the industry focus its resources for developing new vaccines and effective alternatives?