How to diagnose and prevent sudden death syndrome caused by Clostridium welchii in pigs?

Sudden death syndrome caused by Clostridium welchii in pigs, also known as pig red intestine disease, is an enterotoxemia in pigs caused by Clostridium welchii types A, C and D.

1. Onset symptoms

The disease generally has no premonitory symptoms and presents as sudden death. Some affected pigs may also be seen before death with mania and restlessness, ataxia, hoarse squealing, abdominal distension, difficulty breathing, sudden collapse, frothing at the mouth, muscle tremors, paddling of the limbs, pale skin, opisthotonus, and death within 1 to 3 hours.

2. Pathological changes

Dead pigs are in good body condition, with complete rigor mortis; the skin is pale, and in a few cases cyanosis under the abdomen may also be seen. A small number of affected pigs have blood-tinged foam around the mouth and nose. The anus protrudes outward, and the intestinal tract is cherry red to dark red, especially with the lesions in the jejunum, ileum and anterior segment of the large intestine being the most severe. The intestinal tract is distended with gas, and the intestines are filled with blood-colored frothy liquid material; the mucosa and submucosa show extensive diffuse hemorrhagic and necrotic changes. In severe cases, the intestinal wall is covered with pinhead-sized and millet-sized gas bubbles, which feel crackling when pinched by hand. In a few cases, the blood vessels of the mesentery are filled with gas, and the blood vessels appear beaded. In some cases, the intestinal wall becomes thin or markedly thickened, and in some the contents of the large intestine are dark red. The mesenteric lymph nodes are edematous and hemorrhagic. The stomach is filled with food, and the mucosa sloughs off. The renal cortex shows numerous petechial hemorrhages. The lungs are congested, and the trachea and bronchi are filled with white or pale red foam. The submandibular and inguinal lymph nodes are edematous. Other organs have scattered hemorrhagic spots, and there is pale red exudate in the abdominal cavity.

3. Key points of diagnosis

Clinical symptoms are mostly sudden death, abdominal distension, and pale skin.

Necropsy shows that the entire intestinal segment is distended with gas, congested and hemorrhagic, mostly dark red; piercing the intestinal tract releases a foul odor, and the intestinal contents are mostly dark red.

Smears of small intestinal mucosa or intestinal contents or mesenteric lymph nodes are Gram-positive, with single or paired large thick bacilli with bluntly rounded ends; tissue smears show an obvious five-colored or pale purple capsule. Using conventional pathogen culture and isolation techniques, gas begins to form after 3 to 6 hours of anaerobic culture in meat and liver broth, and microscopic examination shows Gram-positive large thick bacilli in absolute predominance. After 48 hours of anaerobic culture on glucose blood agar plate medium, colonies are about 2 to 4 mm in diameter, round, smooth, slightly raised in the center, and have a double zone of hemolysis.

4. Prevention and control measures

Clostridium welchii in pigs is sensitive to oxytetracycline and sulfonamides, but because the disease comes on rapidly and causes death quickly, the treatment effect on affected pigs is very limited. For pigs in the same group, 100 mg/kg oxytetracycline or diaveridine can be mixed into the feed for feeding, continuously for 5 days, which can effectively prevent and stop the occurrence of the disease.