Knowledge of prevention and treatment of highly pathogenic blue ear disease in pigs

The disease is a serious viral disease of pigs in recent years, which is caused by a mutant strain of porcine reproductive and respiratory syndrome virus (PRRSv). The virus is highly contagious, the incidence of piglets in infected pig farms can reach 100%, the mortality rate can reach more than 50%, and the abortion rate of sows can reach more than 30%. It is characterized by the disease and death of finishing pigs.

1. Pathogen:

The pathogen of the disease is porcine reproductive-respiratory syndrome virus, which is caused by Lelistad virus.

2. Epidemiology:

Pigs of all ages and species can be infected, but pregnant sows and piglets within one month of age are the most susceptible. The incubation period is 2-4 days for piglets and 4-7 days for pregnant sows. The main route of infection was respiratory tract, and air transmission, contact transmission and vertical transmission were the main modes of transmission. Piglets produced by diseased pigs, infected pigs and infected sows and contaminated environmental appliances were the sources of infection. Mice may be the carriers and communicators of the disease. The disease spreads more easily among piglets than among adult pigs.

Third, clinical symptoms:

The main symptoms of the disease are reproductive disorders of sows and respiratory symptoms of piglets.

Sows: low spirits, poor appetite, temporary high body temperature, cough, varying degrees of dyspnea, abnormal estrus or infertility, pregnant sows giving birth prematurely or giving birth to stillbirths, mummified fetuses and sick piglets, the abortion rate can reach more than 30%. Some postpartum no milk, placenta stagnation, a few sows ears, ventral and vulvar skin have transient cyan-purple or blue-purple plaques.

Suckling piglets: body temperature up to 41 ℃, dyspnea, sometimes abdominal breathing, anorexia, diarrhea, red ears, conjunctivitis, rough coat, ataxia, easy to develop other diseases, morbidity up to 100%, mortality up to 50%. The piglets have been emaciated for a long time and their growth is slow. Fattening pigs: mild influenza-like symptoms, temporary anorexia and mild dyspnea. A few pigs cough and have transient dark bluish purple plaques on the back, edge and tail skin of both ears.

Boar: low incidence, about 2Mel 10%, anorexia, dyspnea, weight loss. And a few boars have discolored skin on both ears. The semen quality of boar decreased. In addition, because the pathogen of the disease has obvious variability, the clinical manifestation of the disease is very complex, which can be divided into acute type, subclinical type and chronic type. In addition, the symptoms are also different in different countries, different strains and management factors may affect the occurrence of clinical symptoms and production loss.

4. Changes of pathological examination:

A large amount of clear fluid could be seen in the chest of stillborn and debilitated piglets, liver degeneration area in lung of suckling piglets, no thinning of colon, and edema of mesenteric lymph nodes, subcutaneous and muscles. There were no visible changes in boars, sows and finishing pigs. After autopsy, there were infarcted foci on the edge or surface of spleen, khaki in kidney, massive bleeding spots from needle tip to millet grains on the surface, bleeding spots and bleeding spots in subcutaneous, tonsil, heart, bladder, liver and intestinal tract. Gastrointestinal bleeding, ulcer and necrosis can be seen in some cases.

5. Diagnosis:

The disease is difficult to diagnose only according to symptoms and epidemiology, and laboratory diagnosis is needed. The presence of the disease can be judged according to the following conditions: the rate of premature delivery, abortion, stillbirth and debilitated piglets in sows, an increase in postpartum non-milk sows, an increase in respiratory symptoms in piglets less than one month old, and redness in the ears of some piglets. Diarrhea increased, lean piglets increased, the cure rate decreased, the weight gain rate decreased, and the mortality increased significantly. The whole herd of pigs have had cold-like symptoms recently, and some pigs have bluish purple or blue-purple patches on their ears, abdomen, perineum and tail.

VI. Prevention and control:

Comprehensive epidemic prevention measures and vaccine immunization are effective ways to control and reduce the incidence of blue ear disease.

First, it is necessary to strengthen quarantine and strictly implement the isolation and feeding system when introducing and purchasing piglets, so as to put an end to the introduction of virus from the epidemic areas.

Second, it is necessary to advocate self-breeding and self-feeding, implement closed feeding management, strictly implement the system of isolation and disinfection, implement delivery room isolation, weaning piglets should be weaned as soon as possible, and establish disease-free clean pig farms.

Fourth, it is necessary to adopt the "all in and all out" system for fattening pigs, and thoroughly disinfect the pig house after the pigs are out of the pen.

Fifth, the vaccine should be used correctly. Attention should be paid to distinguish the different use characteristics of live attenuated vaccine and inactivated vaccine. Inactivated vaccines should be used when vaccinating pigs in disease-free pig farms, while attenuated vaccines must be used when vaccinating pigs that already have blue-ear disease. Reasonable immunization procedures should be formulated according to the local reality to prevent immunosuppression.

Porcine blue ear disease is often secondary to classical swine fever, porcine infectious pleuropneumonia, porcine lung disease and other diseases. Therefore, once the pig farm is infected with blue ear disease, in addition to harmless treatment of dead fetus and dead pigs and cleaning and disinfection of pig houses, diseased pigs should also be fed with high-energy feed, vitamins and adequate electrolytes, and sows should be mixed with aspirin before delivery. When treating diseased pigs, antibiotics should be used to prevent secondary infection. At the same time, the right medicine should be given according to different symptoms of secondary infection.