Prevention and Treatment of Common Pig Diseases in Autumn and Winter

With the arrival of autumn and winter, the occurrence and spread of pig diseases differ markedly from summer. First, as temperatures drop, the probability of viral diseases increases greatly (such as swine influenza, transmissible gastroenteritis, classical swine fever, and foot-and-mouth disease in pigs). At the same time, because of the need to keep warm, increased stocking density and poor ventilation lead to frequent outbreaks of respiratory diseases (such as porcine respiratory disease complex, enzootic pneumonia, and porcine reproductive and respiratory syndrome). The occurrence of the above diseases has given rise to many new features in the epidemiology of pig diseases in recent years. This article gives a brief introduction to several major diseases commonly seen in autumn and winter in recent years.

(1) Swine influenza

Swine influenza, also known as pig flu, is an acute, highly contagious respiratory disease of pigs caused by swine influenza virus (SIV) of the family Orthomyxoviridae. Clinically, it is characterized by sudden onset, coughing, difficulty breathing, fever, exhaustion, and rapid recovery. Pigs of different ages, sexes, and breeds are all susceptible to the disease, and the sources of infection are sick pigs and virus-carrying pigs. It occurs mostly in late autumn, cold winter, and early spring, and is enzootic. It is often triggered by sudden climate changes, dark and damp pig houses, overcrowding, malnutrition, and internal and external parasite infections. If management during the disease period is improper, bronchitis, pneumonia, pleurisy, and the like easily develop, increasing the mortality rate of pigs, so attention should be paid to the prevention and treatment of this disease.

1. Clinical symptoms

The disease has a high incidence rate, with an incubation period of 2 to 7 days and a course of about one week. Usually within 24 hours after the first sick pig appears, most pigs in the herd show symptoms simultaneously, including fever (40.5 to 41.7 degC), anorexia, dullness, huddling, lethargy, and exhaustion; some pigs also show open-mouth breathing, rapid breathing, and abdominal breathing as signs of difficulty breathing, as well as runny nose and redness of the conjunctiva. When there are no complications, most sick pigs recover on their own in about 1 week after antipyretic treatment. If the resistance of sick pigs decreases and secondary infection with other pathogens occurs, such as Pasteurella, Streptococcus, Toxoplasma, and Eperythrozoon, the condition worsens and often leads to death.

2. Prevention and control

At present, there is no specific therapeutic drug for swine influenza. The key is to strengthen feeding management, such as keeping pigs warm and preventing drafts; providing sufficient clean drinking water; and ensuring nutritional balance by supplementing vitamins and trace elements to improve the resistance of pigs. Antiviral drugs such as amantadine, ribavirin, and tea polyphenols, as well as antibiotics or other drugs such as tiamulin, tetracyclines, and penicillins, can be added to feed to control concurrent or secondary infections. To prevent the occurrence of swine influenza, the most effective method is to vaccinate susceptible pigs with influenza vaccine. The vaccines currently on the market are mainly inactivated vaccines and subunit vaccines containing H1N1 and/or H3N2. After vaccination, they provide good protection against infection with influenza virus of the same serotype.

(2) Transmissible gastroenteritis

Porcine transmissible gastroenteritis is an acute, highly contagious infectious disease caused by porcine transmissible gastroenteritis virus of the genus Coronavirus. It is characterized by vomiting, severe diarrhea, and dehydration leading to high mortality in piglets. Sick pigs and virus-carrying pigs are the main sources of infection for this disease. Pigs of all ages can be infected and become ill, with the highest morbidity and mortality in suckling piglets under 10 days of age, and mortality steadily declining with increasing age; other animals are not susceptible to this disease. The occurrence of this disease is clearly seasonal, and in China it is mostly epidemic in the cold seasons of winter and spring. In newly affected herds, almost all pigs can be infected and become ill, while in old epidemic areas it occurs as an enzootic disease.

1. Clinical symptoms

The incubation period of this disease is very short, generally 12 to 18 hours. After infection in piglets within 2 weeks of age, vomiting occurs within 12 to 24 hours, followed by severe watery or pasty diarrhea. The feces are yellow and often contain undigested curds, with a foul odor, rapid weight loss, and obvious dehydration. Death generally occurs in 2 to 7 days, with a mortality rate of 100%; for piglets 2 to 3 weeks old, the mortality rate is 10 to 80%. Weaned pigs become ill 2 days after infection, showing watery diarrhea that is projectile, with gray or brown feces; individual pigs vomit, and the diarrhea stops after 5 to 8 days, with few deaths, but body weight decreases and poor growth is often seen, turning them into runt pigs. Individual sows in close contact with sick piglets and repeatedly infected will show relatively severe clinical symptoms, including elevated body temperature, poor appetite, cessation of lactation, and watery diarrhea, with the fecal water being yellow-green, egg-gray, or brown and mixed with bubbles; death is rare.

2. Prevention

Strengthening feeding management is the key to preventing this disease, especially in cold seasons, paying attention to cold protection and warmth, and keeping pig houses dry, clean, and sanitary. Immunoprophylaxis is also an important aspect of controlling this disease. Immunizing sows once each at two months or half a month before farrowing with attenuated or inactivated porcine transmissible gastroenteritis vaccine can protect piglets. It is also possible to inject transmissible gastroenteritis vaccine into all breeding pigs on the farm in October to November each year.

3. Treatment

There is no specific treatment for this disease. Once the disease is found, strict isolation and disinfection should be carried out immediately. The following disinfectants are commonly used: 1% to 2% caustic soda solution, 10% bleaching powder solution, 10% to 20% fresh lime milk, 10 to 20% hot wood ash water, and 0.5% to 2% formaldehyde solution. During the illness, supplying large amounts of glucose and sodium chloride solution (friendly reminder: using Weikangzhi is more effective), large amounts of clean drinking water, and easily digestible feed can accelerate the recovery of larger sick pigs and reduce piglet deaths. Oral administration of tetracycline, chloramphenicol, sulfonamides, furazolidone, berberine, potassium permanganate, and the like can prevent secondary infection and reduce symptoms. In larger pig farms, once an outbreak occurs, after study by the leadership, artificial infection of non-farrowing sows and older pigs may be carried out to shorten the disease period and increase the antibody level in sow colostrum to passively protect piglets. However, this method carries the risk of spreading virulent virus. Therefore, it must be carried out cautiously only when there are no other infectious diseases on the farm.

(3) Foot-and-mouth disease