Bacterial disease of pigs-Haemophilus parasuis

Haemophilus parasuis, also known as fibrinous serositis and arthritis, is gram-negative bacilli, showing sporadic polyserositis and arthritis. With the development of the world industry, the application of large-scale feeding technology and high density of feeding, as well as the emergence of new respiratory syndrome and other factors, the disease is becoming more and more popular and harmful. In the past two years, it has been reported that Haemophilus parahaemophilus causes polyseritis and arthritis in pig farms in China, especially when the immune function of large-scale pig farms decreases after being infected by blue ear disease and garden ring disease. Haemophilus parasitosis broke out waiting for an opportunity, resulting in serious economic losses.

[epidemiology]

Haemophilus parasuis mainly occurs in young pigs after weaning and in the care stage, with an incidence of 10%-15% and a mortality rate of up to 50% in severe cases. The bacteria parasitic in the nasal cavity and other upper respiratory tract, is a conditional bacteria, can be induced by a variety of factors. Infected pigs or infected pigs mainly infect other healthy pigs through air and direct contact, and other routes of transmission such as digestive tract can also be infected. At present, only larger laboratories are doing laboratory tests, so it is difficult for general pig farms to get correct diagnosis in time. From the analysis of the incidence of the disease, it is mainly related to pig body resistance, environmental hygiene and feeding density in pig farms. If blue ear disease has occurred in pigs, when resistance decreases, Haemophilus parasuis is easy to enter; pigs are dense and overcrowded. The air in the house is turbid, the smell of ammonia is strong, and it often occurs during group conversion, group mixing or transportation. When pigs have respiratory diseases, such as mycoplasma pneumonia, swine influenza, pseudorabies and porcine respiratory coronavirus infection, the presence of Haemophilus can aggravate and complicate their conditions.

[clinical symptoms]

1. Acute type: often first occurs in pigs with good body condition, fever, body temperature rising to 40.5 ℃ ~ 42.0 ℃, depressed spirit, slow response, loss of appetite or anorexia, cough, dyspnea, abdominal breathing, rapid heartbeat, red or pale skin, purple tip of ears, subcutaneous edema of eyelids, nasal discharge, slow walking or reluctance to stand in some diseased pigs. Claudication or unilateral claudication, enlargement of wrist and tarsal joints, ataxia, lying on the side or limbs before death. Sometimes it will die suddenly without obvious symptoms, and in severe cases, sows will have a miscarriage. In the occurrence of arthritis, it can be seen that one or more joints swelling, fever, initial pain, more common in the wrist and tarsal joint, difficult to stand up, hindlimb disharmony.

2. Chronic cases are more common in nursing pigs, mainly loss of appetite, cough, dyspnea, rough fur, weakness or claudication of limbs, poor growth, or even failure and death.

[dissection changes]

Multiple inflammation such as pleurisy, peritonitis, meningitis, pericarditis and arthritis can be seen during dissection, including fibrous or serous exudation, increased pleural effusion and ascites, lung swelling, bleeding, congestion, and sometimes adhesion between the lung and the thoracic cavity. these phenomena often occur in different combinations and rarely exist alone.

[diagnosis]

According to the epidemic situation, clinical symptoms and pathological changes of autopsy (especially the pathological changes of autopsy), the preliminary diagnosis can be made, and the diagnosis needs bacterial isolation and identification or serological examination. In serological diagnosis, Agar diffusion test, complement fixation test and indirect hemagglutination test were used. The disease is mainly differentiated from infectious pleuropneumonia: the lesions caused by porcine Haemophilus paraphaemophilus infection include meningitis, pleurisy, pericarditis, peritonitis and arthritis, while typical infectious pleuropneumonia mainly causes fibrin pleurisy and pericarditis, and is limited to the chest.

[prevention and control measures]

Once pig farms are correctly diagnosed or have obvious clinical symptoms, large doses of antibiotics must be used and drug prophylaxis should be carried out for the whole or the same herd of pigs; most Haemophilus suis are sensitive to ampicillin, fluoroquinolones, cephalosporins, tetracyclines, gentamicin and synergistic sulfonamides, but resistant to erythromycin, aminoglycosides, spectinomycin and lincomycin.

When the disease occurs in pig farms, the following measures can be taken:

① will isolate all sick pigs in the pig house, eliminate stiff or seriously sick pigs with no feeding value, rinse the pig house, strictly disinfect it, improve the ventilation condition of the pig house, evacuate the pig herd, reduce the density, and strictly prohibit mixed breeding.

② whole-group administration: amoxicillin 400g 5% Purejian 1000 g chlortetracycline 2000 g / ton feed for 7 days, stop for 3 days, and then feed for 3 days. Or choose one or two kinds of medicine mixture, such as 50~100PPM, florfenicol 50~100PPM, 1000PPM, 44~1000PPM, 100PPM, lincomycin 200PPM, ciprofloxacin 150PPM, etc.

③ for isolated sick pigs, those who can eat according to the above methods, do not eat or have poor appetite, can be changed to add amoxicillin 200g / ton water, and intramuscular injection of floxacin or 30% Plejian injection 3.57.0ml / 10kg body weight.

④ should eliminate all kinds of inducement, improve feeding management and environmental disinfection, and reduce all kinds of stress, especially to do a good job in prevention and immunity of classical swine fever, pseudorabies and blue ear disease.

⑤ immunization: to prevent sows from being immunized with inactivated vaccine, first immunization 40 days before parturition, and second immunity 20 days before delivery. The pigs can be immunized once 30 days before delivery. Piglets in pig farms seriously threatened by the disease should also be immunized. Pigs from 10 to 60 days of age should be injected with one milliliter at a time, preferably repeated 15 days later.