Several studies have been carried out to understand the explicit role of
C. perfringens in causing NE. It was initially found that
C. perfringens type A having alpha toxin gene is responsible for causing this disease in poultry [
9]. Later on, with the discovery of new toxin in 2008, it was found that the presence of
netB toxin is essential [
6] and the toxinotype having
netB toxin gene in addition to alpha gene was named as
C. perfringens type G in 2018 (which may or may not be having additional toxin genes) [
5]. Some studies still claim that type A alone can also cause NE in poultry [
9] while many others insisted the presence of
netB toxin gene as a key factor in causing the disease [
17]. Interestingly,
C. perfringens type G strains sometimes can also be isolated from healthy chicken [
8,
18]. In this perspective, researchers have found that other predisposing factors are of key importance, which alters the intestinal environment and favors more toxin production leading to moderate to severe intestinal lesions [
10]. Besides several other critical factors, coinfection with coccidia, high protein diet and use of wheat as a dietary source are considered to play a vital role in developing NE infection [
19,
20]. This study established the fact that
C. perfringens type G alone is sufficient to cause NE while other factors, which are critical and play an important role in determining/enhancing the virulence of
C. perfringens toxinotypes were not able to significantly enhance the NE lesion score in the chicken [
17]. The strains used in this study were freshly isolated from field NE outbreak and also grown in enriched media before preparation of inoculum for use according to the set protocol. Fresh 18–20 h culture of
C. perfringens was used for oral administration to chicks.
In this study, the role of
C. perfringens was studied in causing NE with or without other predisposing factors. The main focus of this animal model experimentation was to find out the influence of
netB positive strains, which was successfully established. The type G strains used were confirmed as positive for
netB gene by Sanger dideoxy sequencing method and these NE positive isolates were not positive for other toxins including
cpb2,
tpeL, and
cpe (data not shown). CP(FJ6) and (C8-1) strains were recently isolated field strains with no in vivo and limited in vitro passages, and were observed to produce lesions in more than 50% of challenged chicks. Some other studies also established the fact that only
netB strain can reproduce consistent levels of disease [
17,
21‐
23]. It is also noted in this experimental model, that both
C. perfringens strains produced severe lesions and more number of foci in the duodenum as compared to jejunum and ileum [
24]. Some other experimental models reported more lesions in the jejunum part of small intestine [
9].
In the presence of dietary factor, there was non-significant increase in the severity and lesion score in the challenged birds. One reason for this non-significant increase might be the use of maize based diet, which according to different studies had a lesser impact on NE lesion score than wheat based or other diets, which can somehow delay the retention of diet in the intestine, thereby facilitate the multiplication of microflora at a higher rate. Eimeria necatrix was used alone in this study to cause NE which resulted in significant lesion score in the chicken as compared to the control group however this strain did not enhance the severity of lesions significantly, when used in combination with C. perfringens strains and dietary factor.