Clinical Diagnosis and Prevention of Common Reproductive Disorder Diseases in Small and Medium-Sized Pig Farms (2)
Clinical Diagnosis and Prevention of Common Reproductive Disorder Diseases in Small and Medium-Scale Pig Farms (2)
2.3 Porcine Circovirus Disease
The reproductive disorder form of porcine circovirus disease mainly manifests as affected sows with body temperature rising to 41°C-42°C, decreased appetite, abortion, stillbirth, weak piglets and mummified fetuses, as well as respiratory organ disorders characterized by dyspnea and coughing; some cases show jaundice of the skin and visible mucous membranes, diarrhea and lethargy; piglets infected with this disease present with congenital tremor of piglets and post-weaning multisystemic wasting syndrome. After the disease, sows have low conception rates or infertility, and pre-weaning piglet mortality rises to over 10%.
Congenital tremor shows no obvious necropsy lesions; when post-weaning multisystemic wasting syndrome occurs, it manifests as necrotizing or fibrous myocarditis; some pigs develop jaundice, pulmonary atrophy and interstitial pneumonia; the kidneys are enlarged and pale; the liver shows a certain degree of atrophy; the body surface and mesenteric lymph nodes show congestion, hemorrhage and edema. Necropsy shows stillborn and mummified fetuses, hydrothorax and hydroperitoneum in newborn piglets, and an enlarged, flaccid, pale heart with congestive heart failure.
2.4 Porcine Parvovirus Disease
When pregnant sows are infected in early pregnancy, it causes abortion and embryonic death. When early embryos are infected, their mortality rate can reach 80%-100%, and they are rapidly absorbed by the mother, causing infertility and repeated estrus. Infection in mid-to-late pregnancy often forms mummified fetuses of varying degrees, which are expelled during normal farrowing, accounting for an average of about 10% of the number of pigs delivered. Generally, after 70 d of gestation, most fetuses can produce a meaningful immune response to viral infection and survive, but these piglets often carry antibodies and virus. Other types of pigs show no obvious clinical symptoms after infection.
Pathological changes mainly manifest as mild endometritis in affected sows, partial calcification of the placenta, and dissolution, tissue softening and absorption of fetuses in the uterus. Infected fetuses may show congestion, edema, hemorrhage, body cavity effusion, dehydration and mummification. Weak piglets show petechiae and hemorrhagic spots about half an hour after birth, first at the ear tips, then on the neck, chest, abdomen and the inner sides of the upper limbs, and the skin turns completely purple within half a day, resulting in death. Necropsy sometimes shows enlargement, fragility or atrophy and darkening of the liver, spleen and kidneys.
2.5 Mild Classical Swine Fever
In recent years, mild classical swine fever or atypical classical swine fever has been the main form of classical swine fever, manifesting as reproductive disorders in sows, with abortion, premature birth, stillbirth or mummified fetuses, and failure to come into estrus or infertility; piglets are congenitally infected, weak after birth, have diarrhea, and die successively; some also suffer severe mortality around 20 days of age or before and after weaning, with occasional congenital tremor.
Pathological changes mainly manifest as systemic septicemia, with extensive pinpoint hemorrhages in the throat, pectoral muscles, serosa, kidneys and digestive tract; systemic lymph nodes are swollen, congested and hemorrhagic, appearing purple-black on the surface; the kidneys are swollen, flushed, hemorrhagic, and the cut surface appears marbled; the edges of the spleen have hemorrhagic infarcts, but it is generally not swollen; some affected pigs have scattered hemorrhagic spots on the mucosa of the small intestine, large intestine and bladder. In chronic cases in piglets, button-like ulcers can be seen at the ileocecal valve of the colon, and systemic hemorrhagic changes are not obvious.