Porcine encephalomyelitis is also known as swine polio. The disease first took place in the Czech city of Czech Republic, which also called Jieshen disease. The main violation of the central nervous system, showing symptoms of central nervous system disorders and limb paralysis. The pathogen is the porcine infectious encephalomyelitis virus in the genus Enterovirus of the Picornaviridae family, in which the virulence of serum type 1 is the strongest and is the main pathogen, and the toxicity of type 2, 3, and 5 is lower. The virus is resistant to acids and bases and has strong resistance to the external environment, but it can be killed with sodium hypochlorite, 20% bleach and 70% sprinkling.
First, the diagnostic points
(I) Popular features
Pigs are the only susceptible animals. Young piglets (4-5 weeks old) are most susceptible to morbidity, and most of the pigs are occult. Diseased pigs and healthy poisoned pigs excrete virus with the feces, mainly through contaminated feed, drinking water and other digestive tract infections, and may also be transmitted through the respiratory tract and other routes. In the new epidemic areas, the incidence and mortality are high, and they are mostly distributed in the old epidemic areas.
(b) Clinical symptoms
The incubation period averages about 6 days. Early fever of the disease (40-41 °C), no food, fatigue, followed by ataxia. Severe illness, nystagmus, muscle twitching, head and neck bending, coma. Then paralysis occurs, sometimes sitting in a dog, or lying on the side, stimulated by noises or touches, can cause disharmonious movements of the limbs, or head and neck bending, usually within 3-4 days of the onset of symptoms. Some cases are acute. Afterwards, it can be exempted from death under intensive care, but muscle atrophy and paralysis symptoms remain.
The symptoms caused by the less virulent strains were mild, and the morbidity and mortality were low. At the beginning of the illness, the body temperature rises, hind leg control ability decreases, movement is disordered, and the back is weak. Most of these symptoms can disappear within a few days. Some of the sick pigs then appear to be excitable, with imbalanced balance, uncontrolled exercise, and finally limb paralysis and other symptoms. , call it a benign local snoring.
(c) pathological changes
The lesions were mainly distributed in the ventral horn of the spinal cord, cerebellum gray matter, and brainstem. The gross lesions were not obvious. Histopathological examination showed that the non-suppurative cerebrospinal was changed to severe inflammation, neuronal degeneration and necrosis of the gray matter, glial cell proliferation and aggregation, obvious neuropathy, and a large number of lymphocytes infiltrated around the small blood vessels. , the formation of a clear sleeve phenomenon. There are eosinophilic inclusion bodies in the cytoplasm of neurons. Longer duration, myocardial and muscle atrophy.
(D) Laboratory Inspection
Viral isolation is the most accurate method for diagnosing this disease. This is especially important in areas where the disease is new. Aseptically, the grey part of the cerebellum and spinal cord was taken from sick pigs, refrigerated or placed in 50% glycerol saline and sent for laboratory examination. Piglets can also be used for inoculation test. The diseased material is made into 10% suspension and centrifuged. The supernatant is taken directly into the brain for inoculation. If the vaccinated pig is infected for about 10 days, the same symptoms and pathological histology as natural diseases appear. Changes, in the case of exclusion of the disease, can be diagnosed as the disease.
For detection of serum antibodies, neutralization assays, immunofluorescence assays and enzyme-linked immunosorbent assays can be used. Neutralizing antibodies for the recovery of sick pigs were kept for at least 280 days, and the neutralizing titer of 1 to 64 was judged to be positive. Due to the time-consuming and laborious nature of the neutralization test, ELISAs are often performed using enzyme-linked immunosorbent assays.
Second, the type of disease identification
The disease should be differentiated from other swine diseases that present with neurological symptoms. Special attention should be paid to the identification of porcine hemagglutinating cerebrospinal disease, listeriosis, and pseudorabies.
(I) Porcine Hemagglutinating Cerebral Disease
The encephalitis type of this disease is similar to the porcine infectious cerebrospinal arterial fire, but most of the hemagglutinating encephalomyelitis in pigs is caused by the introduction of new pigs. It mostly occurs in suckling piglets less than 2 weeks of age, and it generally affects one of the pigs. After a litter or a few litters of suckling pigs, the epidemic naturally ceases. The sick pigs had vomiting, constipation and lethargy symptoms before they developed neurological symptoms. Most of the sick pigs did not increase their body temperature. Porcine hemagglutinating encephalomyelitis virus has agglutination and adsorption of red blood cells in chickens, rats, mice, hamsters and turkeys. Porcine infectious encephalomyelitis has no such features.
(b) Listeriosis
This disease can invade a variety of livestock and wildlife and is usually distributed. The piglets have mostly sepsis symptoms, difficulty in breathing, blue-purple skin, and diarrhea. In pigs with neurological symptoms, the cerebrospinal fluid was increased, slightly turbid, contained more cells, the brain stem became soft, there was a small septal area, and neutrophils were infiltrated by the cerebral blood vessels. The liver has small necrosis. There is a significant difference from porcine contagious encephalomyelitis.
(c) Pseudorabies
The disease can invade a variety of livestock and wildlife. After a pregnant sow is infected, she often suffers miscarriage, mummification, stillbirth, and incapacitated fetuses. After getting sick, suckling piglets often exhibit dyspnea, vomiting, diarrhoea, and characteristic neurological symptoms (excited initial state, late palsy). The neurological symptoms of porcine contagious encephalomyelitis are dominated by exercise ataxia and have a strong response to mild irritation.
Third, prevention and control measures
(a) There is currently no specific treatment for this disease. Carry out symptomatic treatment on the basis of strengthening nursing, have certain effect. You can also try the healing pig's serum or blood for treatment.
(b) Prevention should pay special attention to the introduction of quarantine breeding so as to prevent the introduction of virus-borne pigs. Once this disease occurs, it must be quickly diagnosed and resolutely taken measures such as isolation and disinfection to eliminate it. When the epidemic is severe, the organization may train the inactivated vaccine or the attenuated vaccine, or let the sow be in contact with the pig in the pighouse where the disease has occurred one month before the pregnancy to make it lightly infected and produce immunity to protect the future. Born suckling piglets.
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