What is the reason for the high incidence of Haemophilus parasuis in pig farms?

Researcher Wang Guiping, Institute of Veterinary Medicine, Guangdong Academy of Agricultural Sciences 1. Haemophilus parasuis is a common bacterium in the upper respiratory tract (nasal cavity, tonsils and anterior trachea) of pigs. ) was previously considered as a sporadic and stress disease of piglets. Various stress factors can induce and promote the occurrence and prevalence of this disease, such as sudden temperature change, serious air pollution, poor ventilation, cold and humidity, mixed breeding of pigs of different ages, excessive density, improper management, poor feed quality, long-distance transportation, etc., which can all lead to the occurrence of this disease. 2. According to my isolation of Haemophilus parasuis, the disease is regarded as a secondary pathogen. Studies have shown that pigs are infected with blue ear virus or some immunosuppressive viral diseases, which are more likely to be secondary. 3. Serotypes, virulence and virulence factors are still unclear. The distribution of serum is regional, and the cross-protection rate caused by vaccine immunization among different serotypes is very low. Due to the lack of good preventive measures, the outbreak of diseases is becoming more and more serious. Guangdong Dahua Nong Animal Health Products Co., Ltd. Romanlin suffers from many immunosuppressive diseases, especially circovirus, porcine reproductive and respiratory syndrome, and the intensive breeding of pigs worsens the breeding environment. Job cattle in Shandong Heze Hongxingyuan Breeding Pig Co., Ltd. is an opportunistic pathogen, which is mainly parasitic on the upper respiratory mucosa of pigs and often appears in the form of secondary infection. In recent years, due to the prevalence of immunosuppressive diseases in many pig farms (such as blue ear disease, circovirus II, classical swine fever, etc.). ), coupled with the serious infection of mycoplasma pneumoniae, influenza virus and respiratory coronavirus, Haemophilus parasuis took advantage of it and brought huge losses to the pig industry, such as the occurrence in several southern provinces last year. Cai Shaoge, technical director of Baoding Jizhong Pharmaceutical Co., Ltd., is mainly caused by low immunity of pigs. The reasons leading to the low immunity of pigs are: the existence of immunosuppressive diseases, such as blue ear disease and circovirus disease; The prevalence of mycotoxins in feed; Abuse some growth-promoting additives, such as high copper, high arsenic and high zinc; Add some antibiotics for a long time, such as aminoglycoside antibiotics and chloramphenicol antibiotics; Long-term stress and so on. Zhang Ruijie, Technology Department of Sichuan Hengtong Animal Pharmaceutical Co., Ltd. 1. In fact, Haemophilus parasuis has become a permanent bacterium in pigs. As long as the resistance of pigs is reduced, Haemophilus parasuis may break out, and as long as pigs are infected with certain diseases, Haemophilus parasuis may be secondary. 2. In addition, there are many serotypes of Haemophilus parasuis (existing serotype 15), and there are still a large number of isolates that cannot be typed, so there are many difficulties in laboratory detection. In addition, different serotypes have different sensitivities to drugs and strong drug resistance, which adds new challenges to laboratory diagnosis and drug sensitivity tests. 3. Infected pig farms carry bacteria all the year round, cured or drug-resistant pigs carry bacteria all the year round, infected pigs and chronically infected pigs are the sources of infection of this disease. Reasons for Zeng Youquan's high incidence in Fujian Weierdong Pharmaceutical Co., Ltd.: (1) Haemophilus parasuis is a kind of bacteria in the upper respiratory tract of pigs, which can often be isolated from nasal cavity, tonsils and the front of trachea without any clinical symptoms. (2) When the environment changes or the factors causing immunosuppression exist (such as group switching, weaning, mixed group, sudden change of feed or poor ventilation, immunosuppressive diseases), diseases will occur. (3) In recent years, the complication of respiratory diseases and the continuous recurrence of viral diseases in the whole pig industry are one of the reasons for the continuous increase of Haemophilus parasuis.