Symptoms and Prevention and Treatment Methods of Japanese Encephalitis in Pigs
An acute infectious disease caused by a virus that affects both humans and animals. After pigs contract this disease, it mainly causes abortion in sows and acute orchitis in breeding boars.
[Pathogen]
It is caused by the Japanese encephalitis virus. This virus is very small and exists in the brain, spleen, blood and swollen testes of diseased animals; in addition, blood-sucking Aedes mosquitoes and Culex mosquitoes are the reservoir hosts of this virus.
The virus has weak resistance, and general disinfectants can quickly kill it.
[Epidemiology]
(1) It often occurs in late summer and early autumn, with obvious seasonality, which is related to the transmission of this disease by Aedes mosquitoes and Culex mosquitoes. This disease can also infect fetuses through the placenta and be transmitted through mating.
(2) Both boars and sows that have reached sexual maturity can be infected.
(3) The epidemiological characteristics are: high infection rate, low incidence rate (20%-30%), and even lower mortality rate. Deaths are mostly caused by complications, and the vast majority of recovered animals do not relapse. When a pig farm has its first outbreak, the incidence rate is relatively high and the disease is severe; afterward it gradually lessens year by year, and finally the pigs become asymptomatic virus carriers.
[Symptoms]
(1) Sudden reduction in eating to not eating, with body temperature rising to about 41°C.
(2) Listlessness and lethargy; after being driven up, the pig soon lies down again, appearing very exhausted; feces are dry and pellet-like, covered with mucus, and some contain blood.
(3) Some diseased pigs may show mild paralysis of the hind limbs and unsteady walking, and some have swelling and pain in the hind limb joints and lameness.
(4) Pregnant sows suddenly abort or have stillbirths, and most retain the fetal membranes, with reddish-brown or grayish-brown mucus flowing from the vagina. Some abort only after the symptoms disappear; some give birth after the expected due date to stillborn and normal fetuses, with live fetuses varying greatly in size, and the live-born piglets develop spasms and fall to the ground and die within 1-2 days after birth.
(5) When boars are affected, the testis on one side is mostly enlarged by 0.5-1 times, and the scrotal skin on the same side becomes swollen and shiny. In most cases, the swelling gradually subsides after 2-3 days, returning to normal or with the testis shrinking and hardening, thus losing breeding value.
[Prevention and Treatment]
(1) About 30 days before mating, sows are injected subcutaneously with 2 doses of live attenuated freeze-dried vaccine for Japanese encephalitis in pigs. About 30 days before the first mating, breeding boars are injected subcutaneously with 2 doses of this vaccine, and then 1 more injection is required each year in early summer.
(2) Once the disease occurs, 40 ml of Banlangen injection can be used, injected intramuscularly once, once a day; after 2 consecutive injections, the dosage is halved and 2 more injections are given. To prevent secondary infection, penicillin and streptomycin can be injected intramuscularly. After abortion, to prevent retention of the fetal membranes, 20 units of oxytocin can be injected intramuscularly.