**Abstract**

*Salmonella* is the most important gastrointestinal pathogen distributed ubiquitously. The major serovars involved in Non-typhoidal salmonellosis are *S.* Typhimurium and *S.* Enteritidis. In the viewpoint of ban in the export and import of the *Salmonella* contaminated poultry food and poultry products, the need for rapid detection and mitigation of *Salmonella* has increased mani-folds. The major problem associated with its control is the growing incidence of antimicrobial resistance, which has been reported worldwide in the recent years. From causing self limiting gastroenteritis they have found to be responsible for several fatal diseases like endocarditis, meningitis, lung infestations, appendicitis, pneumonia, and cerebral abscess in human beings. Targeting several proteins such as adhesive proteins, lipoproteins, outer membrane proteins (Omps) etc. as vaccine candidates may pave a way in its control. So, continuous monitoring using one health approach and development of effective treatment and control strategies are critical.

**Keywords:** non typhoidal *Salmonella*, gastroenteritis, multiple drug resistance, poultry, vaccine

#### **1. Introduction**

Non-typhoidal Salmonellosis is caused by bacteria belonging to Enterobacteriaceae family. In poultry, *Salmonella* is known to be present in the gastrointestinal tract without showing any symptoms [1]. This leads to an undetected condition at farm level and after consumption of such poultry products like meat and eggs, humans gets infected at fork end. Domestic animals act as a reservoir for the food-borne spread of host-generalist serovars, which accounts for worldwide incidence of non-typhoidal *Salmonella* (NTS) infections. The range of symptoms varies from self limiting gastroenteritis to various dreadful diseases like endocarditis, meningitis etc. Generally condition becomes severe in children, geriatric and immunocompromised individuals [2]. NTS accounts for 93 million enteric infections and 155,000 deaths globally on annual basis [3]. The two factors contributing to majority of NTS infections are its broad host range and multiple drug resistance (MDR), which has been reported universally in recent years [4]. In developing countries, the situation is grimmer due to poor hygienic conditions. Near about 100 cells of virulent *Salmonella* are sufficient to cause infection in humans, which will further depend upon the health condition of an individual [5], hence it is critical

to adopt multiple intervention strategies. Vaccination is considered as an effective tool to control the disease [6], but the available vaccines has their own restrictions such as short term immunity etc. which limits their applicability. So, there is a must requirement to develop a suitable vaccine against NTS. Several proteins such as lipoproteins, outer membrane proteins (Omps) and polysaccharides have been targeted to evaluate their potential as suitable vaccine candidates. This chapter aims to present a brief overview on some such valuable information on NTS.

#### **2. Non typhoidal** *Salmonella* **strains and its transmission**

Till now, more than 2500 serotypes of *Salmonella* have been identified [7]. Non typhoidal salmonellosis is caused by all serotypes of *Salmonella* except for Typhi, Paratyphi A, Paratyphi B and Paratyphi C. Poultry can get infected either with host-specific *Salmonella* serovars, like *S.* Pullorum and *S*. Gallinarum, which cause a typhoid-like systemic disease or wide ranged NTS. Wide range NTS represents *Salmonella enterica* subspecies *enterica* serovar Enteritidis and Typhimurium together with serovars such as *S.* Newport, *S*. Heidelberg and *S*. Javiana etc. Broad host ranged *S.* serotypes get colonize [8] in host and carry infection asymptomatically. *Salmonella enterica* serotype Enteritidis and Typhimurium are the two most important NTS serotypes transmitted from animals to humans in most parts of the world [9].

NTS transmission usually occurs through consumption of contaminated food i.e. chicken, eggs, pork, beef, dairy products, and water contaminated with animal feces. However, contact with animals such as reptiles and animal environment are equally important sources [10]. Majority of reptiles are known to carry *Salmonella* as part of their natural intestinal flora. In poultry, mode of transmission can be vertical or horizontal. Vertical transmission occurs when parent poultry is suffering from systemic infection or transovarian infection which results in infection of infants. *S.* Enteritidis serovar have a particular preference to this mode of transmission. Polluted feed and drinking water, dirty cages, fomites etc. includes horizontal mode of transmission. Colonization of *Salmonella* in poultry without showing any sign and symptoms is common, hence, its transmission in layers (vertical) and broilers (horizontal) can occur at primary production level [11]. Transmission through eggs and meat from such healthy poultry with colonized NTS is common [12]. The degree of *Salmonella* colonization depends on parameters specific to *Salmonella* and effects of environmental stimuli on gene expression. Factors such as age, environmental and physiological stress, diet, and survival of *Salmonella* through gastric barrier, use of antimicrobials in the farm, chicken health, and genetic background of the chicks could possibly influence the colonization [13]. In poultry farms transmission can also occur through workers, vehicles, clothing, footwear, garbage, insects, rodents, wild birds, pets, equipment, and many other factors. In humans, factors contributing to susceptibility of NTS infections include pernicious anemia, any previous gastric surgery, excessive use of medications responsible for gastric barrier reduction etc. [14]. Other associated susceptibilities include homozygosity for sickle cell anemia [15], HIV [16], malaria [17], malnourished infants, and young adults [18].

#### **3. Global disease epidemiology**

In many countries, over the past years, the incidence of NTS has increased markedly. In western countries, the predominant serotypes are *S.* Typhimurium

#### *Non-Typhoidal Salmonellosis: A Major Concern for Poultry Industry DOI: http://dx.doi.org/10.5772/intechopen.96400*

and *S.* Enteritidis. In United States, each year NTS causes approximately 1.35 million illnesses, 26,500 hospitalizations, and 420 deaths [19]. As per the fact sheets of World Health Organization, NTS is 1 of 4 key global causes of diarrhea. The burden is so substantial that every year 33 millions of lives are lost. In Europe, NTS is the second most investigated zoonosis responsible for causing gastrointestinal infections in humans. As per the European Food Safety Authority (EFSA) and European Centre for Disease Prevention and Control (ECDPC) reports, the number of confirmed cases of salmonellosis in Europe still remains high, with a total of 91,857 cases reported in 2018 [20]. The estimation of the total number of NTS infections is a difficult task in developing and under-developed countries, a possible reason to this may be non-reporting of the diseased cases to hospitals. The epidemiological pattern has been variable over the past decade in African countries. Sub-Saharan African region is principally affected region in Africa. According to the hospital based studies of Africa, NTS is the second most frequently occurring pathogen in children and is leading cause of bacteremia in adults [21]. A population-based surveillance data reported the incidence to be between 0 and 54 cases per 100,000 person-years of observation in 13 surveillance sites [22]. The disease incidence ranged from 1.4/100,000 population/year in South Africa (all ages) to 2,520/100,000 population/year in Ghana (<5 years of age) [18]. The community acquired NTS bacteremia prevalence varied from 8% in Nigeria to 45% in Central African Republic [18]. From Kenya, documented incidences were found to be 4134/100,000 person-years [23]. According to the Statistical Committee of the Republic of Armenia, a total of 4,392 cases of salmonellosis were reported during the period 2010–2019, comprising at least 50% of patients below 6 years of age [24]. There is a scarcity in data related to NTS infections from several regions of Asia, limited reports are available from India [25], and Taiwan [26]. A hospital-based multicenter study from Indonesia, Thailand, and Vietnam, investigated NTS positivity rates of 27.5% and 11.7% in children and adults respectively from bacteremia cases [27]. From 2009 to 2013, the prevalence rate of NTS was found to be limited 20/12,940 in bacteremia patients with 25% case fatality report in Bangladesh [28]. In Malaysia, reported prevalence was 16.2%, among which most of the affected cases were from children below 1 year of age [29]. A variety of NTS serovars are known to be present in South-East Asia [30], even some less common serovars are also known to be prevalent such as occurrence of *S. enterica* Weltevreden from the farms of Vietnam [31].
