Porcine encephalomyelitis, commonly referred to as swine polio, was first identified in the Czech Republic and is also known as Jieshen disease. This viral infection primarily affects the central nervous system, leading to symptoms such as neurological disorders and limb paralysis. The causative agent is the porcine encephalomyelitis virus, which belongs to the Enterovirus genus within the Picornaviridae family. Among the different serotypes, type 1 is the most virulent and is the primary cause of the disease, while types 2, 3, and 5 exhibit lower pathogenicity. The virus is highly resistant to environmental conditions, including acid and base exposure, but can be effectively neutralized using sodium hypochlorite, 20% bleach, or 70% alcohol solutions.
**Key Diagnostic Features**
**1. Epidemiological Characteristics**
Pigs are the only natural hosts for this virus. Young pigs aged 4–5 weeks are most vulnerable, though many infections may remain asymptomatic. Infected pigs shed the virus through feces, spreading it via contaminated feed, water, or other gastrointestinal routes. Transmission can also occur through respiratory pathways. In newly affected areas, the disease often has high incidence and mortality rates, whereas in older endemic regions, the situation tends to stabilize.
**2. Clinical Signs**
The incubation period typically lasts around 6 days. Early signs include fever (40–41°C), loss of appetite, and weakness, followed by ataxia. Severe cases may present with nystagmus, muscle spasms, head and neck flexion, and even coma. Paralysis usually follows, with pigs sometimes adopting a dog-like sitting position or lying on their sides. Stimuli like noise or touch can trigger abnormal limb movements or neck bending. Most pigs recover within 3–4 days, though some may develop lasting muscle atrophy or paralysis. Milder strains result in less severe symptoms, such as reduced hind leg coordination and temporary gait abnormalities, which often resolve within a few days.
**3. Pathological Changes**
Lesions are mainly found in the spinal cord's ventral horn, cerebellar gray matter, and brainstem. Gross lesions are not always apparent, but histopathological examination reveals non-suppurative inflammation, neuronal degeneration, necrosis, and glial cell proliferation. Lymphocytes often accumulate around small blood vessels, forming a "perivascular cuff." Eosinophilic inclusion bodies are frequently observed in neurons. Prolonged cases may lead to myocardial and muscle atrophy.
**4. Laboratory Diagnosis**
Viral isolation from the cerebellum and spinal cord of infected pigs is the most accurate diagnostic method, especially in new outbreaks. Samples should be collected aseptically, stored in 50% glycerol saline, and transported promptly. Piglets can also be used for inoculation tests. Serum antibody detection methods include neutralization assays, immunofluorescence, and ELISA. Neutralizing antibodies persist for over 280 days, and a titer of 1:64 is considered positive. ELISA is more widely used due to its efficiency.
**Differential Diagnosis**
The disease must be distinguished from other neurological swine diseases, including porcine hemagglutinating encephalomyelitis, listeriosis, and pseudorabies.
- **Porcine Hemagglutinating Encephalomyelitis**: Commonly occurs in piglets under two weeks old, often introduced by new animals. It causes vomiting and lethargy before neurological symptoms appear, and the virus agglutinates red blood cells in various species, unlike porcine encephalomyelitis.
- **Listeriosis**: Affects multiple animals and presents with sepsis, difficulty breathing, and diarrhea. Neurological cases show increased cerebrospinal fluid and brain softening, which differs from porcine encephalomyelitis.
- **Pseudorabies**: Causes reproductive issues in sows and severe neurological symptoms in piglets, including excitement and paralysis, which differ from the ataxia seen in porcine encephalomyelitis.
**Prevention and Control**
There is no specific treatment for this disease. Supportive care and improved husbandry can help manage symptoms. Some practitioners use serum or blood from recovered pigs for treatment. Prevention focuses on strict biosecurity, quarantine of new animals, and rapid response to outbreaks through isolation and disinfection. Vaccination with inactivated or attenuated vaccines is recommended in severe outbreaks. Sows can be exposed to infected pigs one month before farrowing to build immunity and protect newborns.
Half Shell Mussel,Frozen Cooked Half Shell Mussel,Seafood Frozen Half Shell Mussel,Frozen Half Shell Mussel
Shengsi Xiangyuan Aquatic Products Co.,Ltd., , https://www.mytilus-edulis.com