**1. Introduction**

Salmonellosis of poultry are caused by bacteria of the *Salmonella* genus and are configured as one of the main systemic diseases or localized in the gastrointestinal tract of these animals, whose effects are associated with serious losses in poultry farming. Some of these diseases are zoonotic and, because of this, have a highlighted position in the exercise of public health surveillance worldwide. Despite all the technological development in the field of epidemiology and the normative regulations regarding infectious diseases through prevention and control programs, which aim to preserve human health and poultry farms, the prevalence and notification of cases involving public and animal health are still increasing and worrying [1].

Starting from the increasing attention to the health of commercial poultry, public and private sectors have fomented the development of diagnostic and prevention instruments to reduce or eliminate *Salmonella* spp. from poultry flocks [2]. These bacteria are among the main pathogens involved in epidemics or outbreaks of diseases carried by food involving public health with vast dissemination, especially through eggs and meat, since poultry are the main reservoirs for the human species [3]. Thus, salmonellae stand out as one of the most pathogenic enterobacteria, responsible for intestinal and systemic damage and different degrees of mortality in their hosts [4].

The poultry industry has been constantly challenged by bacterial and viral pathogens, with serious economic losses. Among the infectious agents that challenge poultry production, the major responsible for losses in the sector is *Salmonella* spp.. Salmonellae belong to the family *Enterobacteriaceae* and can cause three specific diseases in poultry, including Avian Typhoid caused by *Salmonella* Gallinarum, Pulorosis caused by *Salmonella* Pullorum, and Avian Paratyphoid caused by the other serovars of the *Salmonella* genus [5].

Gastroenteritis and septicemia accompanied by elevated mortality in young birds are typically caused by the serotypes *Salmonella* Pullorum and *Salmonella* Gallinarum, which are transmitted horizontally and vertically. Cases caused by the other serovars, with the exception of serotypes Gallinarum and Pullorum, characterize paratyphoid infections, which can be transmitted by direct and indirect contact with individuals of the same species, such as birds themselves or with reservoirs represented by the reptiles, mammals, rodents, and the man [4].

Other *Salmonella* serotypes have public health importance, as are the cases of *Salmonella* Enteritidis and *Salmonella* Typhimurium. In these cases, the consumption of chicken meat and eggs is the most commonly described cause in the transmission of this bacterium to humans [6]. In man, these salmonellosis stand out as one of the main bacterial diseases which cause gastrointestinal disorders described worldwide [7]. Most cases of salmonellosis of importance in health surveillance are described as a self-limiting gastroenteritis characterized by diarrhea, fever, and abdominal cramps in humans. However, there are reports of mortality in children and the elderly. Furthermore, in the socioeconomic sphere, salmonellosis are described in association with absenteeism and medication expenses, besides the development of resistance to antimicrobials [8].

Over the years, the mechanisms and transmission pathways of salmonellosis in poultry have been a constant concern for the poultry industry. Given the epidemiological importance of poultry within the chain of transmission of *Salmonella* spp. to man, this study dedicates itself to questioning the presence of this agent in facilities aimed at poultry production, which represents a potential risk to public and animal health, with serious losses to the poultry agribusiness [6]. The detection of *Salmonella* spp. in commercial poultry flocks is probable, for this bacterium is widespread throughout the world, mainly in regions where there is a high poultry density [2].

In commercial farms, fallowing is one of the most commonly employed techniques to combat *Salmonella* spp. in contaminated farms. The fallowing method consists of the period between cleaning and disinfection of the poultry house and the housing of the next flock [9]. In counterpart, some authors define fallowing as a prophylaxis measure in epidemiology, represented by a period of time that must be applied to empty and disinfected premises to reduce the load of pathogenic microorganisms

and, therefore, minimize the microbiological challenge to the birds later housed in these premises [10].

Salmonellae are highly resistant bacteria in the environment and survive in poultry equipment and facilities for more than a thousand days [11]. Since this bacterium is responsible for great losses to the poultry sector and damage to public health, the present study is justified by the economic, social, and medical relevance of *Salmonella* spp. to society. Thus, it is necessary to analyze the effectiveness of fallowing used to promote its elimination from contaminated farms, as it is a widespread technique.

Considering the resistance in the environment and the survival in poultry equipment and facilities for long periods, it was questioned in this work the possibility of isolating *Salmonella* spp. in poultry farms with a history of *Salmonella* Gallinarum, after the completion of a 149-day fallow period. The possibility that after this period it would still be possible to isolate *Salmonella* spp. was admitted, given its characteristic of high viability or resistance to environmental conditions.

This study's overall objective was to investigate the environmental presence of *Salmonella* spp. bacterium in poultry houses of a commercial establishment destined for the confinement of poultry of the species *Gallus gallus*. The specific objectives were to verify the effectiveness of the fallowing technique applied for 149 days in poultry farms with a history of *Salmonella* Gallinarum isolation, to perform the isolation of *Salmonella* spp. in highly selective culture medium from environmental drag swabs, to characterize the isolated colonies in the culture medium, and to carry out an epidemiological inquiry in order to know the conditions of application of fallowing and the sanitary management practices adopted that are related to the epidemiology of *Salmonella* spp. in order to subsidize the bacteriological diagnosis.
