Swine anthrax is a bacterial disease of pigs

Anthrax is an acute septicemic infectious disease caused by Bacillus anthracis that affects various livestock, wild animals and humans alike. Clinically it presents with septicemia symptoms; necropsy findings include poor blood clotting, markedly enlarged spleen, and hemorrhagic gelatinous infiltration under the skin and serous membranes. In pigs it occurs sporadically, mostly in subacute or chronic form.

Epidemic characteristics: Bacillus anthracis forms spores that can survive for a very long time in the external environment; pigs become infected through the digestive tract, and grazing pigs can be infected by rooting in the soil for food; pigs have relatively low susceptibility; cases are mostly sporadic or discovered at slaughter; there are slightly more cases in summer.

Clinical symptoms: pigs mostly have a chronic course, with no obvious clinical symptoms before death, and are mostly discovered only during meat inspection after slaughter; some pigs (subacute type) show pharyngitis symptoms, with elevated body temperature, listlessness and loss of appetite, obvious swelling of the throat and parotid region, difficulty swallowing and breathing, stiff neck movement, cyanosis of the oral and nasal mucosa, and may finally die of suffocation; individual pigs may also show acute septicemia symptoms.

Pathological changes: to prevent spread of the pathogen and creation of new epidemic foci, dissection is prohibited when anthrax is suspected. In pigs with acute septicemia, rapid putrefaction is seen, with incomplete rigor mortis, dark purple mucous membranes, red or red-yellow gelatinous infiltration in the subcutaneous tissue, muscles and serous membranes, along with hemorrhagic spots; blood clots poorly and is thick and tarry like coal tar; the spleen is highly enlarged and soft, with the splenic pulp on the cut surface soft and muddy, dark red; lymph nodes are enlarged and hemorrhagic; the heart, liver and kidneys show degeneration; the gastrointestinal tract shows hemorrhagic inflammation. Pharyngeal anthrax shows necrosis of the tonsils, inflammatory edema of the larynx, epiglottis and neck tissues, and swelling, hemorrhage and necrosis of the surrounding lymph nodes. The characteristic changes of chronic anthrax in pigs after slaughter are: inflammation of the pharynx, enlargement and necrosis of the tonsils; enlargement, hemorrhage and necrosis of the submandibular lymph nodes, with a dry, lusterless cut surface, brick-red in color, with gray or gray-yellow necrotic foci; yellow-red infiltration of the surrounding tissues.

Diagnosis: take peripheral blood or spleen from suspected dead pigs, make smears, and perform anthrax capsule staining (formaldehyde gentian violet or methylene blue staining), which reveals large bacilli with capsules; or isolate and culture, which reveals the characteristic colonies of Bacillus anthracis.

Prevention and treatment methods: when a pig farm is severely contaminated with swine anthrax, consider using 0.5 ml of avirulent anthrax spore vaccine or 1 ml of No. 2 anthrax spore vaccine, injected subcutaneously; immunity develops two weeks after injection and lasts for one year. Once disease occurs, immediately treat with 50-100 ml of anti-anthrax serum (for large pigs) and antibiotics (penicillin, tetracycline, etc.) or sulfonamides; at the same time report the epidemic, and adopt resolute measures of blockade, isolation, disinfection and destruction of carcasses to stamp out the epidemic as quickly as possible.

Slaughterhouses and meat processing plants should strengthen quarantine inspection of slaughtered pigs, especially the head inspection after bleeding.