Heat stress impairs egg production in commercial laying hens infected by fowl typhoid

ABSTRACT

Salmonella Gallinarum (SG) is an avian-restricted pathogen that causes fowl typhoid in poultry. Although it has been reported frequently over many decades in poultry flocks worldwide, the microorganism is more commonly associated with poultry in developing countries, particularly those with high ambient temperatures, where the acute form of the disease results in considerable economic losses. A more detailed investigation of environmental factors that affect the course of disease may assist in identifying effective prevention and control measures. Heat stress is known to impair the immunological response to a variety of pathogens and clearly may be an important contributory factor in the prevalence of disease in countries with warm or hot climates. Thus, the objective of the present study was to evaluate the effects of heat stress on chickens infected with SG. For this, light and semi-heavy commercial laying hens were distributed randomly within four groups as follows: infected and non-infected groups in rooms held at ambient temperature, and infected and non-infected groups under heat stress. Clinical signs, egg production, and mortality were recorded daily. Bacteriological counts in liver and spleen samples were estimated at 2, 5, 7, and 14 days post-infection. The results showed that both SG infection and heat stress had similar effects on egg production and a synergistic effect of the two stressors was observed. The data show an interaction between disease and heat stress which could point towards environmental and biosecurity approaches to resolving the possible 30% fall in production observed in such countries.

KEYWORDS:

• Avian salmonellosis
• fowl typhoid
• heat stress
• Salmonella Gallinarum
• laying hens
• poultry

Acknowledgements

Thanks to Post Graduate Program in Veterinary Medicine, Agricultural and Livestock Microbiology and Pro-rectory of Teaching and Research (PROPe), School of Agricultural and Veterinary Sciences Sao Paulo State University (FCAV/UNESP), Jaboticabal, SP, Brazil.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by São Paulo Research Foundation (FAPESP) and Coordination for the Improvement of Higher Education Personnel (CAPES) and the National Council of Technological and Scientific Development (CNPq) [grant numbers 2019/23634-1 (G.B. Viana) and 2018/03189-0 (A. Berchieri Junior)].