David John Hampson

Bacterial diseases of poultry tend to cause significant losses to the poultry industry worldwide annually. This chapter focuses on some of the sporadic bacterial diseases. The less common pathogens included in this chapter are Staphylococcus, Streptococcus, Erysipelas, spirochetes, and tuberculosis. The section on enterococci and its association with disease is included with the streptococci. These organisms have an increased influence in poultry production due to their ability to cause local and systemic disease and in light of the limited use of growth promoters. The chapter also includes a section devoted to miscellaneous organisms that have caused disease in poultry or are a public health concern. Bacterial culture is required for diagnosis, as clinical signs and gross lesions of acute enterococcal infections overlap with other bacterial diseases of chickens. Prevention and control require reducing stress and preventing immunosuppressive diseases and conditions. Proper cleaning and disinfection can reduce environmental enterococcal resident flora to minimize external exposure.

This chapter reviews a group of diseases of swine resulting from infection with anaerobic intestinal spirochetes of the genus Brachyspira. These include swine dysentery (SD), a severe mucohemorrhagic colitis caused by infection with strongly hemolytic Brachyspira species, as well as milder forms of brachyspiral colitis caused by weakly hemolytic Brachyspira species. SD occurs mainly in grower and finisher pigs and less frequently in weaner pigs. Brachyspiral colitis is an umbrella term used to describe diarrhea and colitis in pigs infected with one or more pathogenic Brachyspira spp. Brachyspira pilosicoli colonizes human beings who are usually either immunocompromised or live in developing communities where hygiene is poor and fecal contamination of water supplies may occur. Porcine intestinal spirochetosis or porcine colonic spirochetosis has been reported in most pig‐producing countries. Transmission occurs by the fecal‐oral route, and infection may be introduced into naïve herds by carrier pigs.

The ‘colonic’ spirochetes assigned to the genus Brachyspira are slow-growing anaerobic bacteria. The genus includes both pathogenic and non-pathogenic species, and these variously colonise the large intestines of different species of birds and animals, including humans. Scientific understanding of the physiology and molecular biology of Brachyspira spp. remains very limited compared with that of other pathogenic spirochetes, and there are few descriptions of successful genetic manipulations undertaken to investigate gene function. An important boost to knowledge occurred in 2009 when, for the first time, the whole genome sequence of a Brachyspira strain (Brachyspira hyodysenteriae strain WA1) was obtained. The genomics analysis provided a significant increase in knowledge: for example, a previously unknown ~36 Kb plasmid was discovered and metabolic pathways were constructed. The study also revealed likely acquisition of genes involved in transport and central metabolic functions from other enteric bacterial species. Four subsequent publications have provided a similarly detailed analysis of other Brachyspira genomes, but of these only two included more than one strain of a species (20 strains of B. hyodysenteriae in one and three strains of B. pilosicoli in the other). Since then, more Brachyspira genomes have been made publicly available, with the sequences of at least one representative of each of the nine officially recognised species deposited at public genome repositories. All species have a single circular chromosome varying in size from ~2.5 to 3.3 Mb, with a C + G content of around 27%. In this chapter, we summarise the current knowledge and present a preliminary comparative genomic analysis conducted on 56 strains covering the official Brachyspira species. Besides providing detailed genetic maps of the bacteria, this analysis has revealed gene island rearrangements, putative phenotypes (including antimicrobial drug resistance) and genetic mutation mechanisms that enable brachyspires to evolve and respond to stress. The application of Next-Generation Sequencing (NGS) to generate genomic data from many more Brachyspira species and strains increasing will improve our understanding of these enigmatic spirochetes.

Spirochete infections of birds are caused by helical-shaped bacteria of the order Spirochaetales, family Spirochaetaceae. Two distinct syndromes exist because of differences in spirochete colonization, pathogenesis, and lesion production; non-relapsing, tickbourne, acute septicemic borreliosis caused by Borrelia anserina; and subacute-to-chronic intestinal disorders of varying severity caused by a divese group of spirochetes of the genus Brachyspira.

This chapter includes a collection of miscellaneous organisms that have caused disease in poultry or are a public health concern. The less common pathogens implicated in poultry loss included are Staphylococcosis, Streptococcus and Enterococcus, Erysipelas, avian intestinal spirochetosis, tuberculosis. Disease syndromes included in the chapter include beak necrosis, venereal disease of geese, and liver granulomas, but are not identified to a specific organism responsible because of the multifactorial nature of the disease. Staphylococcosis is diagnosed by culturing suspected clinical material including exudate from joints, yolk material, and stab swabs of internal organs. Staphylococcosis can resemble infection with Escherichia coli, Pasteurella multocida, Salmonella gallinarum, Mycoplasma synoviae, reoviruses, or any other infection of bones or joints that is hatchery‐related, associated with mechanical trauma, or causes septicemia. Prevention and control of Enterococcus infections require reducing stress and preventing immunosuppressive diseases and conditions. Proper cleaning and disinfection can reduce environmental enterococcal resident flora to minimize external exposure.

Amongst environmental factors, the composition of the diet is well understood to be a critical determinant of economic pig production, but its potential impact on specific enteric diseases is often overlooked. Pigs suffer many economically important diseases and disorders of the gastrointestinal tract (GIT), and these require control to prevent overt disease, reduce morbidity and mortality, maintain welfare, and to improve the efficiency of production. Veterinarians, feed manufacturers, nutritionists and producers have generally relied upon antimicrobial compounds such as antibiotics and dietary minerals (e.g. zinc oxide, copper sulphate) for a large part of this control. However, concern related to antimicrobial resistance and environmental contamination has resulted in questioning of these current strategies to control enteric bacterial diseases. A plethora of strategies for control have been examined and sometimes implemented, but unfortunately in practice there remains no simple and universal alternative means to reduce susceptibility to pathogens in the GIT. The current chapter focuses on sonic of the ways that the diet can influence specific enteric infections, with particular emphasis on the proliferative enteropathies (PE), caused by the intracytoplasmic bacterium Lawsonia intracclluIaris, and swine dysentery (SD), caused by the anaerobic spirochaetal bacterium Brachyspira hyodysenteriae. Both diseases remain extremely important in pigs throughout the world. A relatively small number of studies have addressed whether manipulation of diet texture and/or composition can influence the occurrence of these two diseases. Evidence to date suggests that SD may be more amenable to nutritional manipulation than PE, but irrespective of the disease, considerable variation exists in the disease severity and prevalence observed in different studies, even from the same institution. This makes it currently difficult to recommend firm dietary guidelines to prevent/reduce these two enteric bacterial diseases.