What are the noteworthy issues concerning Haemophilus parasuis?
Several noteworthy issues concerning Haemophilus parasuis!
Although Haemophilus parasuis is not an immune-mediated disease, multiple studies have shown that when Haemophilus parasuis disease is prevalent in pigs, the immune effect of vaccines is very poor, and after Haemophilus parasuis is effectively controlled and the pigs recover, the immune effect of various vaccines is effectively improved. It has been reported that piglets immunized twice with classical swine fever cell vaccine (5 doses at 21 days of age and 5 doses at 63 days of age), with blood samples collected at 84 days of age for testing, across 3 consecutive batches of 16 pigs each, showed an antibody titer qualification rate above 90%. However, during periods when Haemophilus parasuis is prevalent, the antibody qualification rate is only around 40%. Although Haemophilus parasuis is not an immune-mediated disease, when Haemophilus parasuis disease is severely prevalent on a pig farm, the immune effect is very poor, and it can be significantly improved by controlling Haemophilus parasuis. The possible reason is that after pigs are infected with Haemophilus parasuis, due to prolonged high fever that does not subside, viruses are inactivated in the body, and some attenuated vaccines, such as classical swine fever and pseudorabies vaccines, cannot colonize in the body, thereby causing immune failure. In addition, Haemophilus parasuis can cause circulatory disturbances, which is also an important reason for the significantly reduced immune response capacity.
2. The inflammatory exudation problem in the pathology of Haemophilus parasuis
The effusion in the thoracic cavity, abdominal cavity, and joint cavities as well as fibrinous exudates in pigs with Haemophilus parasuis disease are all results caused by inflammatory exudation and cardiac edema in the pathology of Haemophilus parasuis, and this is alsotreatmentan important problem that must be solved during the process.
3. The endotoxin problem of Haemophilus parasuis
Why is it that some pigs with Haemophilus parasuis disease, when only using drugs fortreatment, not only do their symptoms not lessen, but instead worsen, or even result in death? This is because Haemophilus parasuis, like other Gram-negative bacilli, can produce endotoxin. Endotoxin is a component of the cell wall of Gram-negative bacteria, called lipopolysaccharide, which is toxic to the host. Endotoxin is released only after the bacteria die and dissolve or after the bacterial cell wall is destroyed by artificial methods, so it is called endotoxin. Currently, the relatively effective approaches for anti-endotoxintreatmentare, first, limiting the production of endotoxin, and second, using endotoxin antagonists. Traditional Chinese medicine preparations such as Astragalus polysaccharide and Epimedium can promote the inactivation of endotoxin, reduce its activity, and achieve the purpose of adjunctivetreatment.
4. Why some drugs have poor curative effects on Haemophilus parasuis
In drug sensitivity tests, some drugs are sensitive to Haemophilus parasuis, but thetreatmenteffect is unsatisfactory. This is mainly because Haemophilus parasuis is present in large numbers in the serosa, joints, meninges, lungs, and other sites, while the capillaries in the serosa, joints, meninges, and other areas are sparsely distributed, and there is a blood-lung barrier between the lungs and the blood, making it difficult for general drugs to reach these sites where Haemophilus parasuis is distributed. Therefore, in the selection of drugs, conducting only drug sensitivity tests to choose drugs is insufficient; drugs with strong penetration and high tissue distribution concentration must be used, and only in this way can they penetrate deep into the sites where Haemophilus parasuis adheres.
5. Immunization against Haemophilus parasuis
It is recommended to use the Haemophilus parasuis polyvalent oil emulsion inactivated vaccine
Sows: basic immunization, immunize twice with a 3-week interval, then once every 6 months or once per litter 40 days before farrowing.
Piglets: on farms with severe infection, the inactivated vaccine can be used to immunize piglets once at 7 days of age and once at 21 days of age.
6. Treatment
of Haemophilus parasuis
Once pigs develop Haemophilus parasuis, the drugs of first choice are ceftiofur and cefquinome, followed by ampicillin, etc., with injection administration being preferable. To enable antibiotics to reach the brain and joint cavities, an injection route is usually required to be effective.NL For preventive injectable medication, piglets can be given intramuscular injections of amoxicillin or ceftiofur twice at 1 day of age and 7 days of age, or three injections of amoxicillin or ceftiofur before weaning; long-acting oxytetracycline can also be administered by intramuscular injection 3-4 days before the onset of disease. Forbreeding pigs, ceftiofur can be administered by intramuscular injection one day before farrowing to reduce thebreeding pigs