A review of vaccine development and research for industry animals in Korea

Lee, Nak-Hyung; Lee, Jung-Ah; Park, Seung-Yong; Song, Chang-Seon; Choi, In-Soo; Lee, Joong-Bok

In general, modern vaccines against zoonotic agents in industry animals should be marker vaccines because the industry would use it massively and then resulting immunity could be differentially measured by companion diagnostic methods. The marker vaccine which will not interfere with the current diagnostic procedures in vaccinated animals will certainly help in controlling zoonotic diseases. The development of a more specific diagnostic method to replace the current test, will allow the development of both live and killed vaccine. Various vaccines have shown limited effectiveness in reducing transmission of zoonotic agents to humans through the consumption of animal-derived products. It should be noted that certain generic procedures can be applied to preventing the establishment of zoonotic agents in livestock, and keeping the animals free of infection by preventing contact between them and other potentially infected animals, and maintaining clean housing and food. Nevertheless, more research is required to develop a complementary vaccine and sanitation program to protect humans from zoonotic infection. The present section focuses on animal vaccines selected for zoonotic agents economically significant in industry animals. Among enteric bacteria which are frequently present, E. coli O157:H7 is the most deadly bacteria which is often present in the gut feces, and other skin of healthy cattle and sheep. The bacteria are well adapted to the host without showing evident clinical signs. The bacteria can survive for a couple of months at various environment conditions, could transmit to humans via food; notably under cooked ground beef and raw milk. Human outbreaks are associated with hemolytic uremic syndrome (a severe consequence among a small percentage of cases). Although various intervention strategies were introduced in feedlots in the US, strict hygienic measures account for the decline of O157:H7 outbreaks. Recently, a subunit vaccine containing secreted virulence factors has been tested in the field in feedlot cattle but the results were still far from clearance of the bacteria. Clearly, vaccination could be an aid in the future reduction in the number of outbreaks, but only in combination with hygiene measures. Among many serotypes of Salmonella species, clinical salmonellosis for industry animals is the result of infection with host-restricted serotypes of Salmonella, such as S. Enteritis, S. Gallinarum, S. Dublin, and S. Pullorum. Sometimes, non-host specific Salmonella serotypes sometimes induce self-limiting gastrointestinal infection but can cause systemic infection in a wide variety of host animals including humans. Among Salmonella spp., S. Typhimurium and S. Enteritidis are the two serotypes most commonly associated with foodborne disease in humans but they mostly occur asymptomatically in livestock. For poultry, various killed and live vaccines are commercially available. For swine, S. Typhimurium infections are mostly subclinical but can be transferred by meat product to humans. Several vaccines for swine have been shown to be effective to interfere with homologous or heterologous serotypes. Vaccination for livestock is considered to be one of the cornerstones of the strategy to reduce human Salmonella infections. In general, the protection against to Salmonella is required for cellular immunity as well as in particular, local mucosal immunity in the gastrointestinal tract to prevent colonization in the gut and eliminate