Why is swine fever so hard to control? Five common clinical causes and countermeasures
Five common clinical causes of hard-to-control swine fever and countermeasures
Countermeasures: Use qualified vaccines, pay attention to proper storage, and standardize the methods of use and operation; do not copy schedules straight from books, but choose a reasonable immunization schedule according to the actual epidemic situation in the local area and on the farm. In general, in areas with no swine fever outbreak, piglets are immunized once with lapinized attenuated swine fever freeze-dried vaccine at 60 days of age and maintained until slaughter; in areas with few swine fever cases and a low level of contamination, piglets should preferably be immunized twice, that is, the first immunization at 21 to 25 days of age and the second at 60 to 65 days of age, with no repeated injection within 1 year; in areas with severe swine fever virus infection, piglets should receive pre-immunization.
Wrong preventive medication. Among antibiotics, furazolidone, kanamycin, sulfonamide drugs, and the like have a certain inhibitory effect on the proliferation of B lymphocytes in the body and can affect the immune effect of viral vaccines. If these drugs or feed additives containing these drugs are wrongly used before immunization injection, it will lead to a reduction in the body's white blood cells, thereby affecting the body's immune response.
Countermeasures: Within 10 days before and after immunization, furazolidone, kanamycin, sulfonamide drugs, or feed additives containing these drugs must not be used.
Mixed sources of pigs. The pigs on some pig farms come from different areas, the piglets are of different ages, and whether they have been immunized and the effect of immunization are difficult to determine. If virus-carrying sick pigs are mixed in, infection will occur after mixing.
Countermeasures: Large-scalepig farmsshould implement an all-in, all-out management system and adhere to self-breeding and self-raising; when a newly built pig farm really needs to introduce piglets from other places, it must contact the veterinary department at the source of the pigs and select piglets that have been immunized with swine fever vaccine. After introduction, a 1-week to 2-week isolation observation period should be set aside, and measures should be taken promptly if suspicious piglets are found.
Harm of vertical infection. Swine fever virus can infect vertically through the placenta, causing miscarriage, stillbirth, deformed fetuses, and the death of weak piglets several days after birth, resulting in major economic losses.
Countermeasures:Breeding pigsshould be booster-immunized once a year. To overcome the interference of maternal antibodies, weaned piglets can be injected with 3 to 4 doses of swine fever vaccine. In areas where swine fever frequently occurs, the method of pre-immunization can be used to protect piglets, that is, after the piglets are born and before suckling, inject 1 dose of swine fever vaccine, allow suckling 2 to 3 hours after injection, and then vaccinate once more at 60 to 65 days of age.
Difficulty in clinical diagnosis. After the use of vaccine immunization, although the incidence of swine fever has decreased significantly, pigs are still infected with swine fever, except that the symptoms tend to be mild, presenting as atypical or mild forms. At the same time, bovine viral diarrhea virus is closely related to swine fever virus, and the two share common antigens. Bovine viral diarrhea virus can also cause stillbirth in pigs and death of newborn piglets, and the clinical features and gross lesions of piglets are similar to those of chronic swine fever infection. Therefore, when atypical cases appear clinically, it is very difficult to make a confirmed diagnosis.
Countermeasures: Pay attention to testing the swine fever antibody levels of the pig herd and promptly give booster injections of swine fever vaccine. Large-scale pig farms should carry out swine fever immune-body interactive immunization experimental diagnosis for suspected diseased pigs, so as to accurately determine whether they are infected with swine fever virus. So far, this is also the simplest, most feasible, accurate, and reliable method for confirming swine fever. For mild swine fever, a single injection of 20 to 30 doses of swine fever vaccine can cure it. (Source: Breeding and Feed)