Suchergebnisse

During the early years of the last three decades, the animal- and public-health problems associated with Salmonella in poultry increased to such an extent to become major political issues, of which the general public become very aware. Salmonella Enteritidis, in particular, became a worldwide problem, arising mainly from poultry (Rodrigue et al ., 1990). In many countries, individual phage types of this serovar replaced S. Typhimurium as the most dominant type in poultry and humans. Control in poultry has become a major issue and immunity, whether acquired or, more speculatively, innate, is seen as one of the possible means of containing the problem. As a result, Commission Regulation (EC) No 1177/2006 (EC, 2006) prescribes the application of vaccination programmes against S. Enteritidis, at least during rearing, for all laying hens providing they did not demonstrate a prevalence of less than 10% (EC, 2006). In the UK cattle industry, clinical salmonellosis in its acute and chronic forms, together with subclinical infection, remains a major economic, welfare and health problem. While the incidence of acute clinical salmonellosis in pigs is less of a problem compared with that of cattle, subclinical Salmonella infections that result in carcass contamination lead to the introduction of the organism into the food-chain (EFSA, 2008). Widespread use of antibiotics has led to the emergence of multiple antibiotic-resistant bacteria, especially S . Typhimurium. These problems have indicated to the industry and government agencies an increasing requirement for effective vaccines to control this important zoonotic infection. This review discusses the reasons for the relatively poor success in immunizing food animals against those non-host-specific Salmonella serovars that usually produce food poisoning, compared with the success obtained with the small number of serovars that more typically produce systemic _etyphoid-like_f diseases in a restricted range of host species. Most of our understanding of immunity to salmonellosis arises from experimental work with typhoid-like diseases, mainly S. Typhimurium infection in mice. Such work may not be entirely relevant to the, often disease-free, colonization by most Salmonella serovars. However, during the last decade our knowledge, especially on the immune response of poultry after exposure to non-host-adapted serovars, has increased considerably. Whereas live, attenuated vaccines against host-specifi c serovars are highly protective, similarly developed vaccine strains have traditionally been less effective in protecting chickens, calves and pigs against intestinal colonization. Newer methods of attenuation are being developed, but their exploitation and success will depend on appropriate attenuation, delivery, their use for the types of infection that have been shown to be amenable to immune control and their effectiveness under fi eld conditions. One of the key questions is to fi nd the balance between an accepted level of attenuation and an unaffected ability to induce protection involving innate as well as adaptive immunity. This will be possible realistically only through the use of molecular genetics to generate precisely defi ned Salmonella mutants. From the point of view of consumer safety there is a school of thought that considers inactivated or subunit vaccines to be the safest. The benefi ts of developing effective killed or subunit vaccines over the use of live vaccines are enormous. Recently, there have been signifi cant advances in the development of adjuvants, for example microspheres or cytokines, which are capable of potent immunostimulation and modulating the immune response in a more controlled and specific manner (Morein et al. , 1996; Schmidt et al. , 2007; Dey and Srivastava, 2011). The exploitation of such technology in conjunction with the ongoing developments in identifying key Salmonella virulence determinants should form the next generation of Salmonella subunit vaccines for the control of this group of pathogens.

A recent European Union Directive required member states to put monitoring and control programmes in place, of which vaccination is a central component. Live Salmonella vaccines generally confer better protection than killed vaccines, because the former stimulate both cell-mediated and humoral immunity. Administering Salmonella bacteria orally to newly hatched chickens results in extensive gut colonization and a strong adaptive immune stimulus but broiler chickens are immunologically immature. However, colonization exerts a variety of rapid (within 24 h) protective effects. These include specific colonization-inhibition (competitive exclusion) in which the protective bacteria exert a profound resistance to establishment and colonization by other related bacteria. This is thought to be primarily a metabolic attribute of the vaccinating bacteria but may also involve competition for attachment sites. The presence of large numbers of bacteria originating from a live Salmonella vaccine in the intestine can also induce infiltration of polymorphonuclear cells into the intestinal wall, which confers resistance to invasion and systemic spread by virulent Salmonella strains. This opens new perspectives for vaccine usage in broilers, layers and breeding poultry but also in other animals which show increased susceptibility to infection because of their young age or for other reasons, such as oral chemoprophylaxis or chemotherapy, where the lack of established normal gut flora is an issue. We recommend that all live vaccines considered for oral administration should be tested for their ability to induce the two protective effects described above. Further developments in live Salmonella vaccines are, however, currently hindered by fears associated with the use and release of live vaccines which may be genetically modified.

Die Überwachung und Bekämpfung vom Tier auf den Menschen übertragbarer Krankheiten (Zoonosen) wurde in der Europäischen Union durch das In-Kraft-Treten einer neuen Zoonosenrichtlinie kürzlich auf eine neue Grundlage gestellt. Eine Überwachungspflicht für Brucellose, Campylobacteriose, Echinokokkose, Listeriose, Salmonellose, Trichinellose und die jeweiligen Erreger, Tuberkulose (soweit sie durch Mycobacterium bovis verursacht ist) sowie Verotoxin bildende Escherichia coli wird festgelegt. Für weitere Zoonosen und Zoonosenerreger gilt die Überwachungspflicht je nach der epidemiologischen Situation. Auf diesem Hintergrund werden der aktuelle Kenntnisstand und die epidemiologische Situation wichtiger von Nutz- und einigen Wildtieren auf den Menschen übertragbarer Infektionskrankheiten in Deutschland dargestellt. ; The control of infectious diseases transmitted from animals to humans (zoonoses) was recently put on a new basis in the European Union when a new Zoonoses Directive entered into force. Brucellosis, campylobacteriosis, echinococcosis, listeriosis, salmonellosis, trichinosis, and the respective causative agents, tuberculosis due to Mycobacterium bovis, and verotoxigenic Escherichia coli must be included in monitoring. Additional zoonoses and zoonotic agents are to be monitored according to the epidemiological situation. Against this background, the current knowledge on important zoonoses transmitted from livestock and some wildlife animals to humans as well as the epidemiological situation in Germany with regard to these diseases is summarized.