What are the main causes of sudden death in pigs?

In the process of pig production, many problems often occur. Some problems are fleeting, some occur from time to time, and some emerge one after another. As managers and technicians of a @#@227@#@ farm, one should learn to let go of the "fleeting ones," pay attention to the "recurring ones," and focus on solving the "endless ones." The problem of sudden death in pigs belongs to the "recurring ones," which often puzzles farmers and requires the attention and concern of managers and technicians.

There are many cases of sudden death in pigs, and the causes are not the same. The body weight of the pigs and the stage of the disease at onset also vary. The main causes of sudden death in pigs include white muscle disease in piglets, foot-and-mouth disease in suckling piglets, acute aflatoxin poisoning, edema disease in piglets, the early stage of swine dysentery, acute yellow scour of newborn piglets, acute swine erysipelas, intestinal hemorrhagic syndrome, and stress syndrome.

I. Sudden death diseases that mainly occur in piglets

(1) Swine dysentery

Piglets 49-84 days old, occurring in all four seasons, first as an acute outbreak, then becoming chronic, and difficult to eliminate. In the early stage of the epidemic, they die suddenly without showing symptoms. Most have diarrhea of varying degrees, first passing soft stool, gradually becoming yellow loose feces mixed with mucus or blood. The main findings are swelling, congestion, and hemorrhage of the cecal and colonic mucosa, with the intestinal lumen filled with mucus and bran-like pseudomembranes. Microscopic examination of intestinal mucosal smears shows large numbers of spirochetes. Oral administration and injection of mequindox are very effective.

(2) Acute yellow scour of newborn piglets

It is most commonly seen in piglets 1-3 days old, and the most acute cases die suddenly a few hours after birth without visible symptoms. Affected piglets pass yellow loose feces containing small curd particles, which flow down along the anus and usually leave no fecal traces around it, so it is easily overlooked. When diarrhea is severe, the tip of the vulva and the hind limbs of young female pigs are soiled with fecal fluid; affected pigs eat less or stop nursing, are in poor spirits, have a relaxed anal sphincter, fecal incontinence, dehydration, and emaciation, and finally collapse into coma and die.

(3) White muscle disease (muscular dystrophy)

White muscle disease mostly occurs in piglets around 20 days old, and affected piglets are physically strong but suddenly become ill. Body temperature is normal, appetite decreases, spirits are low, breathing is labored, they prefer lying down, and they often die suddenly. The cause of white muscle disease is selenium deficiency.

(4) Foot-and-mouth disease in suckling piglets

It usually presents as acute gastroenteritis and myocarditis, leading to sudden death.

(5) Edema disease in piglets

It mostly occurs around weaning and can occur in all four seasons. It is more common in well-nourished and physically strong piglets, which become ill and die suddenly. Some first have mild diarrhea and then constipation, some have edema of the eyelids and other areas, or show neurological symptoms such as ataxia. Autopsy findings mainly include edema, jelly-like edema of the gastric mucosa and muscular layer at the greater curvature and cardia, and edema of the mesentery and subcutaneous tissue as well.

II. Other major sudden death diseases in growing and finishing pigs

(1) Aflatoxin poisoning

Symptoms appear 5-15 days after pigs eat moldy feed. Acute cases may die during exercise, or die within two days after onset. Affected pigs show listlessness. Appetite decreases or they refuse to eat, the hindquarters are weak, and walking is unsteady. The mucous membranes are yellow-stained, body temperature is normal, and feces are dry. They die within a few days after onset, or die suddenly without showing symptoms.

(2) Acute swine erysipelas

It presents with septicemic symptoms. In the early stage of the epidemic, individual healthy pigs die suddenly without showing any symptoms. Most affected pigs show reduced feeding, or vomiting, chills, and a sudden rise in body temperature to above 42°C; they often lie down and are unwilling to move, and their feces are dry. Some have diarrhea in the later stage; red patches of varying shape and size appear on the skin and fade when pressed with a finger. If piglets contract erysipelas, they often have convulsive neurological symptoms.

(3) Intestinal hemorrhagic syndrome

It refers to a syndrome of sudden death caused by massive hemorrhage in the pig intestine. The disease is more commonly seen in specific-pathogen-free (SPF) herds and lean-type breeding pig herds. It can occur in pigs of all ages after weaning, but the incidence is higher in young replacement gilts, boars 6-9 months old, and pigs 4-8 weeks old after weaning. It occurs in outbreaks and sporadically, and the course of disease is generally very short. Stress factors are the triggers of this disease, especially in individually sporadic cases of sudden stress death in boars and fattening pigs 6-9 months old, confirmed by findings such as small intestinal hemorrhage at necropsy. Clinically, it mainly presents as sudden death; dead pigs and affected pigs in the same group mostly show pale skin, passage of soft feces containing blood or feces with fibrin casts, while other aspects are normal. During the growing period, they often show poor development and periodically pass bloody feces. Necropsy shows a large amount of blood in the small intestine, and the hemorrhage usually extends from the ileum to the entire small intestine and large intestine, with no obvious bleeding point found. In some cases, there is thickening of the intestinal wall at different sites in the posterior one-third of the small intestine, that is, proliferative hemorrhagic enteropathy. In chronic cases, secondary bacterial infection can lead to necrotic enteritis. Prevention and control methods: (1) Add furazolidone 200 mg/kg to the feed. (2) For infection accompanied by proliferative enteropathy and Campylobacter mucosalis, add tylosin 200 mg/kg to the feed or use it in combination with penicillin 100 mg/kg to control it. (3) For acute cases, a combined trial of antihistamines, corticosteroids, and vitamins has been successful.

(4) Sudden death stress syndrome

It mainly occurs when animals are stimulated by strong stressors, with sudden death without any clinical symptoms. For example, boars may die suddenly from excessive excitement during mating; pigs may be overly frightened when being chased, or overly crowded during transport, and all of these may cause sudden death due to excessive nervous tension, when the "sympathetic-adrenal" system is strongly stimulated and becomes overactive, causing shock or circulatory collapse. Prevention and control methods: Specific prevention and control measures should be selected according to the nature of the stressor and the stress syndrome: (1) Remove stressors and improve feeding management, such as ensuring good ventilation in pig houses and preventing damp-heat crowding, sudden changes in temperature, noise, and disturbance. Do not feed or reduce feeding within 12-24 hours before marketing, and provide oral rehydration salt water; pay attention to transport by vehicle or ship or driving on land to avoid excessive stimulation; or before marketing and transport, use anti-stress hormones, anti-stress additives, or sedatives such as chlorpromazine in stress-sensitive pigs to prevent the occurrence of stress phenomena. For pigs with heat stress and heatstroke, pour cool water on the head and give cold-water enemas. (2) Pay attention to selection and breeding work. Pigs that are timid and nervous, difficult to manage, easily frightened, prone to red patches on the skin, have elevated body temperature, and appear plump are mostly stress-sensitive types and are best not selected for breeding. When necessary, use modern scientific and technological testing of whole blood or serum CPK (creatine phosphokinase), as well as the halothane screening test, to further eliminate such pigs from the breeding herd.