Prevention and Treatment Methods and Key Technical Points for Several New Pig Diseases

I. Post-weaning Multisystemic Wasting Syndrome in Pigs

This disease is a new disease caused by porcine circovirus type II (PCV2), characterized mainly by rapid or difficult breathing, diarrhea, anemia, obvious lymphoid lesions and progressive emaciation in weaned piglets. The incidence of this disease is 5%-20%, sometimes as high as 100%, and the mortality rate is 100%. It severely affects pig growth and development, has caused huge economic losses, and has evolved into a worldwide disease that has attracted widespread attention from countries around the world.

The disease mostly occurs in pigs from 6 weeks to 9 weeks of age. Clinical manifestations include progressive emaciation, rapid or difficult breathing, coughing, and sometimes diarrhea, paleness and jaundice; necropsy shows enlarged lymph nodes but without hemorrhage, rubber-colored lungs, and enlarged waxy kidneys with white spots visible on the kidney surface; microscopic changes include emptying of lymphoid follicles and granulomatous inflammation in lymph nodes, liver and other tissues, and lymphocytic interstitial pneumonia can also be seen in the lungs. Because the clinical symptoms are not specific, diagnosis can only be confirmed by laboratory testing for PCV2 antigen or nucleic acid.

In the prevention and treatment of this disease, in addition to measures such as introducing healthy pigs, improving feeding management, reducing stress factors, and strengthening quarantine and disinfection, the best approach is immunization by injection. PCV2 vaccines are already available, and vaccination can effectively prevent this disease. For treatment, Inmodulen is a newly developed biological immune therapeutic preparation that can significantly reduce the mortality rate.

II. Haemophilus parasuis disease

Haemophilus parasuis disease is a new infectious disease of pigs caused by Haemophilus parasuis, characterized by polyserositis, arthritis and meningitis. The disease is prone to occur under stress conditions such as feed changes, group transfers, temperature changes, immunization and castration. This disease is very widespread, and the pathogen exists in major @#@227@#@ countries. In recent years, due to large-scale and frequent introduction of breeding stock from abroad, this disease has been brought into China and has begun to occur in some areas, so high vigilance is required.

Symptoms: characterized by coughing, difficulty breathing, emaciation and rough hair coat. The main manifestations are fever, poor appetite, anorexia, difficulty breathing, joint swelling, lameness, trembling, slow response, ataxia, cyanosis of visible mucous membranes, and purplish-blue discoloration of the ear tips and abdomen; in acute cases in weaned piglets, edema occurs under the skin and in the lungs, and death occurs quickly after stress or the appearance of neurological symptoms; acute infection in sows can cause abortion; boars develop lameness symptoms.

Necropsy: multiple serous and purulent fibrinous exudation, most commonly in the peritoneum, pericardium and pleura, and sometimes also on the meninges and joint surfaces, especially the carpal joints and tarsal joints; occasional hemorrhagic spots can be seen on the kidney surface.

Prevention and treatment: immunization with inactivated Haemophilus parasuis vaccine can effectively prevent this disease. Once the disease occurs, treatment with penicillins or cephalosporins is effective. For a group, when one pig is affected, in addition to treating individual key cases, medication for the whole group can effectively control the spread of this disease.

III. Porcine Proliferative Enteropathy

Porcine proliferative enteropathy, also called proliferative ileitis, is an infectious disease caused by Lawsonia intracellularis, characterized by adenoma-like proliferation of epithelial cells in the crypts of the small intestinal mucosa of pigs. In recent years, the incidence has shown an upward trend in the United States, Australia, Brazil, France, Denmark, the United Kingdom and other countries, and it has therefore received increasing attention.

The clinical feature of this disease is tar-like diarrhea. Acute cases often occur in growing-finishing pigs from 6 weeks to 20 weeks of age, and sometimes also in nursery piglets and adult boars and sows. Gross necropsy mainly shows proliferative enteropathy, hemorrhage, and diffuse necrotizing typhlocolitis, similar to swine dysentery. Laboratory diagnosis can use microscopic examination combined with PCK and specific hyperimmune rabbit serum or monoclonal antibody fluorescent immunoassay techniques to detect bacteria in feces.

Vaccination of breeding herds and weaned fattening herds can effectively control this disease. Lactating sows and replacement gilts can also be given lincomycin-spectinomycin in feed for 8 consecutive weeks, which can effectively prevent and treat the occurrence of this disease. Once the disease occurs, intravenous injection of erythromycin can take effect quickly.

IV. Porcine Dermatitis and Nephropathy Syndrome

This disease mainly affects pigs from 8 weeks to 18 weeks of age, with an incidence of 12%-30% and a case fatality rate of 5%-14%. Clinical manifestations include extensive purplish-red round or irregular lesions of varying size and shape on the skin of the chest, abdomen, thighs and front legs, which may coalesce; affected pigs show anorexia, depression and fever of about 41°C, and 60%-80% of pigs with skin lesions die. Necropsy shows enlarged, pale kidneys with lesions in a mottled pattern, sometimes with hemorrhage and edema; enlarged and hemorrhagic lymph nodes, button ulcers at the ileocecal junction, pulmonary edema or rubber-like lungs, and occasionally gastric ulcers and colitis. Attention should be paid to distinguishing this disease from classical swine fever and swine erysipelas to avoid misdiagnosis.

There is no specific prevention or immunization and no specific drug treatment for this disease. Control of this disease is based on good management and high-level biosecurity measures, as well as all-in-all-out and effective disinfection measures as safeguards, in order to achieve the purpose of prevention and treatment.

V. Swine Hepatitis E

Swine hepatitis E is one of the emerging zoonotic infectious diseases that has attracted considerable attention. Hepatitis E virus (SHEV) is a major cause of viral hepatitis in humans. The incidence in young adults shows a relatively high proportion of fulminant hepatitis, with a mortality rate of 0.5%-3%, but in pregnant women the mortality rate can be as high as 15%-20%.

For prevention and treatment of this disease in pigs, early weaning (17-19 days of age) can be adopted to prevent vertical transmission, and strict isolation of piglets can prevent horizontal transmission. These measures help establish virus-free pigs. For humans in areas where hepatitis E is endemic, effectively improving water quality and boiling water before drinking will be the key to controlling the spread of this disease, because the virus mainly spreads through contaminated water sources.

VI. Porcine Blue Eye Disease

Porcine blue eye disease is a new type of pig disease caused by porcine parotitis virus. The disease mainly infects boars. After infection, boars show enlarged testes and epididymides, severe changes in sperm, decreased sperm concentration, damaged sperm acrosomes and weakened motility, and the virus is carried in semen and can be shed through semen. This disease is easily confused with porcine Japanese encephalitis, and attention should be paid to differentiation. To confirm this disease, indirect immunofluorescence assay can detect the virus in the semen of infected boars.

The best way to prevent and treat this disease is vaccination. A commercial inactivated vaccine for porcine blue eye disease in Mexico has already been launched and can be used for emergency preventive injection.