Necrohemorrhagic enteritis induced by Clostridium perfringens type C infection occurs in practically all countries with intensive pig production.
Suckling pigs usually get sick in the first days after birth and sometimes at the age of 2–4 weeks. When a litter is subject to necrohaemorrhagic enteritis, 50% of suckling pigs are affected on average. The mortality rate among diseased suckling pigs is often 100%.
The suckling pigs receive clostridium perfringens type C immediately after they are born. The bacteria attack the mucous membrane of the small intestine, where they multiply. This causes tissue death in the mucous membrane with effusion of blood to the inner intestines. In case of prolonged disease, diphtheria-like, stripe-shaped, thick membranes are formed on the diseased intestinal mucous membrane.
The occurrence of necrohemorrhagic enteritis in a litter of pigs depends on the balance between the amount of antibodies achieved by immunisation and the amount of trypsin-inhibitor in the colostrum. Unfortunately, this balance is not possible to determine in practice. The effect of immunisation against necrohemorrhagic enteritis is also influenced by the surrounding environment and the replacement rate in the sow herd. The higher the risk of infection and the higher the number of gilts introduced every year, the greater the demands on the effect of vaccines.
In this connection it should also be noted that it is not possible to use vaccines to compensate for poor housing environments and inadequate cleaning and disinfection.
Outbreaks of necrohemorrhagic enteritis in spite of regular immunisation are well-known. They occur at varying points in time relative to birth. It has been observed in recent years that the timing of outbreaks of the disease has shifted to sometimes occur in the second and subsequent weeks of life. There can be several reasons for this, including an ineffective vaccine or sows and particularly gilts can have produced too few antibodies, and, finally, the high risk of infection plays a role.