Med. Weter. 68 (12), 712-716, 2012

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Truszczyński M., Pejsak Z.
Importance and mechanism of stress in disease syndromes of food animals, caused by facultatively pathogenic bacteria
Losses in animal production caused by unfavourable environmental conditions and facultatively pathogenic bacteria, occurring relatively often as commensals in cattle, swine and poultry, are believed to be higher than those related to pathogens causing diseases irrespectively of environmental conditions, even if these conditions are favourable. Stress plays an essential role in the transition of commensals into pathogens. This review presents up-to-date definitions of stress and mechanisms, leading as a consequence of stressors, in relation to the microorganisms and the host. Stress thus suppresses the immune system and increases the susceptibility of the animal to infection by releasing neurotransmitters, cytokines and hormones into the circulation or tissues. The most important role is played by catecholamines (epinephrine and norepinephrine) and by glucocorticoids (cortisol and corticosterone). Additionally a new perspective is presented, indicating that stress-related hormones directly affect the microorganism or the host-pathogen interaction. As a result of stress, which causes neuroendocrine changes, commensals grow faster and generate pathogenic processes. This effect of stress stimulates the development of multifactorial syndromes with symptoms from the intestinal tract or the respiratory system. The above-mentioned examples refer to infections caused by certain serotypes of Escherichia coli, serovars of Salmonella enterica and Campylobacter jejuni. In conclusion, stress may influence the outcome of common bacterial infections. Since stress leads to serious losses in animal production, the implementation of procedures for preventing stress and ensuring the welfare of food animals from birth to slaughter should be a priority for animal breeders and veterinarians.
Key words: facultatively pathogenic bacteria, the role of stress in generating disease syndromes, mechanisms of stress, host, bacteria