**Tri Dev Acharya 1,2,3, Anoj Subedi 4 and Dong Ha Lee 2,\***

Received: 31 March 2019; Accepted: 17 June 2019; Published: 20 June 2019

**Abstract:** With over 6000 rivers and 5358 lakes, surface water is one of the most important resources in Nepal. However, the quantity and quality of Nepal's rivers and lakes are decreasing due to human activities and climate change. Despite the advancement of remote sensing technology and the availability of open access data and tools, the monitoring and surface water extraction works has not been carried out in Nepal. Single or multiple water index methods have been applied in the extraction of surface water with satisfactory results. Extending our previous study, the authors evaluated six different machine learning algorithms: Naive Bayes (NB), recursive partitioning and regression trees (RPART), neural networks (NNET), support vector machines (SVM), random forest (RF), and gradient boosted machines (GBM) to extract surface water in Nepal. With three secondary bands, slope, NDVI and NDWI, the algorithms were evaluated for performance with the addition of extra information. As a result, all the applied machine learning algorithms, except NB and RPART, showed good performance. RF showed overall accuracy (OA) and kappa coefficient (Kappa) of 1 for the all the multiband data with the reference dataset, followed by GBM, NNET, and SVM in metrics. The performances were better in the hilly regions and flat lands, but not well in the Himalayas with ice, snow and shadows, and the addition of slope and NDWI showed improvement in the results. Adding single secondary bands is better than adding multiple in most algorithms except NNET. From current and previous studies, it is recommended to separate any study area with and without snow or low and high elevation, then apply machine learning algorithms in original Landsat data or with the addition of slopes or NDWI for better performance.

**Keywords:** surface water mapping; machine learning; naive Bayes; recursive partitioning and regression trees; neural networks; support vector machines; random forest; gradient boosted machines; Landsat; Nepal


**3. Salmonellosis and public health**

Growth in international trade and current facilities for traveling increased not only the dissemination of pathogenic agents and contaminants in foodstuffs, but also our vulnerability. Nowadays, the world is interrelated and interdependent. Thus, local foodborne disease outbreaks have become a potential threat for the whole world. Globalization, commercialization and distribution make it possible for a contaminated foodstuff to affect the health of people in several countries at the same time. The identification of only one contaminated food ingredient may lead to the discard of literally tons of food; to considerable economic losses to the production sector; restrictions to trade; and effects on the tourism industry (Tauxe et al., 2010).

Therefore, there is an ever growing perception of the need and importance for surveillance systems and adoption of measures to ensure food safety, such as the identification of the foods involved in foodborne disease outbreaks. In 1992, the National Surveillance scheme for general Outbreaks of Infectious Intestinal Disease was introduced in England and Wales to provide comprehensive information on causative agents, sources, vehicles of infection and modes of transmission (Oliveira et al., 2010).

*Salmonella* spp. is an intestinal bacterium responsible for severe foodborne intoxications. It is one of the most important agents involved in outbreaks reported in several counties (Tessari et al., 2003)*.* Salmonellosis is an important socioeconomic problem in several counties, mainly in developing countries, where this etiological agent is reported as the main responsible for foodborne disease outbreaks (Alves et al., 2001). There are reports of foodborne salmonellosis in humans since the 19th century, caused by the ingestion of contaminated bovine meat (Barrow, 1993). It is one of the most problematic zoonosis in terms of public health all over the world because of the high endemicity, but mainly because of the difficulty in controlling it (Antunes et al., 2003, Santos et al., 2002), and the significant morbidity and mortality rates (Cardoso et al., 2002).

which encodes phase 2 antigens. These genes are expressed by a phase-variation mechanism, with fliC being found in all *Salmonellae*, and having a homologous gene found in *E*. *coli;* whereas fljB is located in a region exclusive to the *Salmonella* genome, and is found in four of the six subspecies. In some cases, triphasic strains may be isolated. Besides the other two genes, it was described that these strains presented the flagellin gene (flpA) in a plasmid. The genes that encode flagellin in *Salmonella* spp. are generally highly conserved in

In practical conditions, rapid agglutination with polyclonal antisera (12 polivalent and 85 monovalent antisera) may frequently occur in the absence of expression of one of the phases, preventing the identification of the serovar. This may happen in some serovars, when cell subpopulations, each possessing a given antigen or set of antigens associated with their flagella, are able to produce a third or fourth type of flagellum. Identification, in these cases, requires "immobilization" of one of the phases, in order to characterize the unknown phase, a technique called "phase inversion". When the phase is not recognized, the serovar will not be conclusively diagnosed, preventing effective control actions. However, considering the complexity of flagellar antigens, if not all monovalent antisera are used, results on antigenic structure may be incorrect, such as g,m; g,t; g,p; g,q; g,p,s;

Growth in international trade and current facilities for traveling increased not only the dissemination of pathogenic agents and contaminants in foodstuffs, but also our vulnerability. Nowadays, the world is interrelated and interdependent. Thus, local foodborne disease outbreaks have become a potential threat for the whole world. Globalization, commercialization and distribution make it possible for a contaminated foodstuff to affect the health of people in several countries at the same time. The identification of only one contaminated food ingredient may lead to the discard of literally tons of food; to considerable economic losses to the production sector; restrictions to trade;

Therefore, there is an ever growing perception of the need and importance for surveillance systems and adoption of measures to ensure food safety, such as the identification of the foods involved in foodborne disease outbreaks. In 1992, the National Surveillance scheme for general Outbreaks of Infectious Intestinal Disease was introduced in England and Wales to provide comprehensive information on causative agents, sources, vehicles of infection

*Salmonella* spp. is an intestinal bacterium responsible for severe foodborne intoxications. It is one of the most important agents involved in outbreaks reported in several counties (Tessari et al., 2003)*.* Salmonellosis is an important socioeconomic problem in several counties, mainly in developing countries, where this etiological agent is reported as the main responsible for foodborne disease outbreaks (Alves et al., 2001). There are reports of foodborne salmonellosis in humans since the 19th century, caused by the ingestion of contaminated bovine meat (Barrow, 1993). It is one of the most problematic zoonosis in terms of public health all over the world because of the high endemicity, but mainly because of the difficulty in controlling it (Antunes et al., 2003, Santos et al., 2002), and the significant

extremities 5' and 3', whereas the central region is highly variable.

g,z61; m,t.

**3. Salmonellosis and public health**

and effects on the tourism industry (Tauxe et al., 2010).

and modes of transmission (Oliveira et al., 2010).

morbidity and mortality rates (Cardoso et al., 2002).

According to the World Health Organization (WHO), *Salmonella* is the bacterial agent most frequently involved in cases of foodborne disease all over the world. The agent is normally transmitted to humans by means of foods of animal origin, such as meat, eggs and milk (Nascimento et al., 2003). In the past, the main motivations for controlling *Salmonella* spp. infections in poultry were the losses caused by clinical (pullorum disease and fowl typhoid) and subclinical diseases (paratyphoid infections) (Calnek, 1997). Nowadays, due to the public health implications, prevention of foodborne transmission of *Salmonella* spp. is a priority for the poultry sector (Oliveira & Silva, 2000).

Historically, *Salmonella* Typhimurium was the most common agent of the foodborne disease in humans, although in the past decades *Salmonella* Enteritidis has been most frequently involved in salmonellosis outbreaks (Berchieri Jr. & Freitas Neto 2009; Kottwitz, et al., 2010). There is a growing concern about human infections caused by other serovars, such as Infantis, Agona, Hadar, Heidelberg and Virchow (Freitas Neto et al., 2010).

Concerns about the presence of *Salmonella* spp. in foodstuffs of poultry origin increased in the 1980s, when *Salmonella* Enteritidis phagotype 4 was responsible for several outbreaks of foodborne disease in England, caused by the ingestion of foods containing poultry ingredients (Colin, 1996; Baxter-Jones, 1996). The vertical transmission of *Salmonella* Enteritidis in commercial poultry was responsible for the increased number of cases of human infection in Europe, North America and other parts of the world (Humphrey et al., 1988; International Commission for Microbiological Safety of Foods (ICMSF), 1998). These species replaced *Salmonella* Typhimurium, which was the most common agent of human foodborne infection until the 1980s (Olsen et al., 2003; Jay, 2000).

The introduction of *Salmonella* Enteritidis in Brazil probably occurred in the end of the 1980s, by means of breeders acquired from European countries. This may have also facilitated the introduction and dissemination of phatogotype PT-4 beginning in 1993 (Irino et al., 1996), the predominant phagotype in Europe at this time (Wall & Ward, 1999).

In the 1990s, there were several reports of foodborne disease outbreaks in humans mainly caused by the ingestion of poultry products (Taunay et al., 1996). Between 1995 and 2011, there were 406 reported outbreaks and 16,304 cases of salmonellosis in Brazil, Chile, Argentina, Peru, Uruguay, Paraguay and Ecuador (Franco et al., 2003).

According to the National Health Surveillance Agency in Brazil [ANVISA; *Agência Nacional de Vigilância Sanitária*], among the etiological agents of foodborne diseases identified between 1999 and 2004, *Salmonella* spp. was the most prevalent in Brazil, with the predominance of *Salmonella* Enteritidis between 2001 and august 2005 (Rodrigues, 2005).

According to the WHO, *Salmonella* is one of the pathogens that causes the greatest impact on population health, and is associated with outbreaks and with sporadic cases of foodborne disease. According to data of the Brazilian Ministry of Health, 6,602 foodborne disease outbreaks were recorded between 1999 and 2008, and *Salmonella* spp. was associated with 43% of the cases in which the etiological agent was identified (Medeiros, 2011).

In the European Union, *Salmonella* Enteritidis, *Salmonella* Typhimurium, *Salmonella* Infantis, *Salmonella* Hadar and *Salmonella* Virchow are considered by the European Food Safety Authority the most important serovars in terms of public health (EFSA, 2007). In Japan, between 1999 and 2002, 32% of the cases of foodborne infection were due to *Salmonella*, with Enteritidis, Typhimurium and Infantis as the predominant serovars. In 2005, in the US, the serovars that were most frequently isolated from human sources were *Salmonella* Typhimurium, *Salmonella* Enteritidis, *Salmonella* Newport, *Salmonella* Heidelberg and *Salmonella* Javiana (Centers For Diseases Control and Prevention - CDC, 2007).

Important Aspects of Salmonella in the Poultry Industry and in Public Health 187

A large number of *Salmonellae* have to be ingested to cause gastroenteritis. Generally, the infective dose depends on the serotype, ranging from 2.0x102 to 1.0x106 CFU/g or mL (Huang, 1999). Variation in the symptoms is also related to the type of food and the species of *Salmonella* involved, once species that are adapted to men require lower infective doses to

*Salmonella* excretion in human and/or animal feces may contaminate the water, soil, other animals and foodstuffs. Animals are infected by direct contact with feces, contaminated water and food (Argôlo Filho, 2007). Because of the ability to disseminate and survive for a long period of time in the environment, *Salmonella* may be isolated from superficial freshwater bodies, from sea water in coastal areas, and from several raw materials used in

According to Nascimento (1996), contamination of poultry products (meat and eggs) destined for human consumption may occur at the slaughterhouse, during food preparation, or by cross-contamination with material from poultry with intestinal and systemic infections. As for poultry meat, even a small number of infected birds may contaminate the whole slaughter line, multiplying the chances of occurrence of foodborne disease. Because of that, slaughterhouses where carcasses are not correctly processed are a threat to public health (Nascimento, 1996); current practices of broiler slaughtering and processing may spread microorganisms from one carcass to another. When consumed, the product may be responsible for human infection (Santos, 2004). Although broiler carcasses may be contaminated with *Salmonella* Enteritidis, eggs and egg by-products - mainly homemade mayonnaise – are the main products responsible for outbreaks of the disease in

Transmission of *Salmonella* in birds may occur vertically, via eggs, with the birth of infected chicks; horizontally, by means of ingestion of water, feed, fecal material, contaminated bedding material or dust; or by oral, nasal, conjunctival, cloacal and umbilical routes (Cox et al., 1996; Navarro, 1995; Nascimento, 1996). Many *Salmonella* serotypes may survive for weeks or months in manure or bedding material, in equipments, in empty sheds, in the dirt around sheds that have been cleaned and disinfected, in feces of wild poultry, in dust particles, and in bird feeders. According to these authors, *Salmonella* may survive in contaminated feed for 26 months, in feces of infected birds for more than 11 days when inside of sheds, or for 9 days in open spaces. Besides, domestic and wild animals may be carriers of *Salmonella*, spreading the microorganism in the environment where they live. These bacteria may cause acute and/or chronic disease in susceptible animals. As stated before, the epidemiological complexity of the disease, which involves vertical transmission, fecal excretion, horizontal transmission, environmental contamination and presence of carriers in different species, make salmonellosis control difficult to be

*Salmonellae* are distributed all over the world. Multiplication outside the body of the host is facilitated by high temperatures and presence of protein (for example, in residual waters). Therefore, the most important points of transmission of *Salmonella* are tropical and subtropical regions, as well as places where there is a large concentration of animals and people. *Salmonella* may also be found in products refrigerated at 2°C; the microorganism is

After entering the digestive system together with contaminated food and water, *Salmonellae* reach the intestines, where they attach to intestinal cells and multiply. Depending on the host species and age, and on the pathogenicity of the microorganism

cause the same characteristics symptoms of the disease (Pinto et al., 2004).

food production (Jakabi et al*.,* 1999).

humans (Silva, 2000).

achieved (Soncini & Back, 2001).

able to remain viable in frozen products for long periods.

In Denmark, *Salmonella* Infantis was isolated from samples of pork, which was pointed out as the source human infection (Wegener & Baggesen, 1996). In several industrialized countries, cases of human infection caused by this serovar have been described (Raevuori et al., 1978; Pelkonen et al., 1994). In Finland, *Salmonella* Infantis was described as the third most important serovar; it infects humans, and it is the most frequently isolated serovar in poultry (Pelkonen et al., 1994). In Hungary, the rate of occurrence of *Salmonella* Infantis has increased in the past years both in the poultry industry and in humans (Nógrády et al., 2008).

National and international regulations determine the absence of *Salmonella* spp. in 25 grams of sample, including poultry meat and eggs. In spite the technological development in food production and the adoption of better hygiene measures in the food production and handling, the incidence of human salmonellosis has increased in several parts of the world (Anais de Toxiinfecção Alimentar, 1996).

In the US, there are more than 800,000 notified cases of infections caused by *Salmonella* spp., with an average of 500 deaths a year. Worldwide occurrence of salmonellosis is calculated in 1.3 billion cases and 3 million deaths (Thong et al, 1995). In 1988, there were 4 million cases of foodborne disease in the US and Canada, representing an estimated cost of US\$ 4.8 billion, including losses in commercialization, productivity and labor (Todd, 1989). In a fiveyear period (1985-1989), there were 189 outbreaks in the US caused only by *Salmonella* Enteritidis, with 6,604 people involved, and 43 deaths.

Salmonellosis epidemiology and control are highly complex, and hygienic and sanitary standards vary with the region, based on feeding and cooking habits, and animal raising practices. Control of the disease is a challenge to public health because of the emergence/reemergence of serovars in different areas, both in developing and developed countries.

Carriers are the most important epidemiological factors, because of the lack of symptoms, and the technical difficulty in detecting them before or during the inspection of foods of animal origin. Considering that the main route of transmission is in the food chain, the presence of this microorganism in production animals shows that *Salmonella* is the most incident and relevant etiological agent of intestinal infections. It causes million of dollars in losses to the industry, mainly in cattle, swine and poultry production, both in local and international trade. In some countries, rigid food inspection is a constant need to produce foodstuffs of high quality.

Besides the importance of preventive measures against the risk of *Salmonella* infection in humans, control of salmonellosis has a positive economic impact in countries where outbreaks occur. Estimated costs of medical expenses, sick leaves and loss of productivity related to the high incidence of salmonellosis in the US range from US\$1.3 to US\$4.0 billion a year (Taitt et al., 2004).

As for fowl salmonellosis, paratyphoid *Salmonellae* are the most important ones in terms of animal and public health (Nascimento et al., 1997). These microorganisms remain in the intestinal tract of the birds, making poultry a possible source of foodborne infection for humans (Berchieri Jr., 1991). Transmission of *Salmonella* to men generally occurs by means of contaminated food and water, although person-to-person transmission may take place, mainly in hospitals. Transmission by contact with infected animals, mainly among veterinarians and farm workers (Trabulsi & Landgraf, 2004), is also possible. It should be emphasized that most serotypes in this genus are pathogenic to men; the differences observed in symptoms may be related to variation in the mechanisms of pathogenicity, age and immune response of the host (Trabulsi & Landgraf, 2004; Hofer et al., 1997).

In Denmark, *Salmonella* Infantis was isolated from samples of pork, which was pointed out as the source human infection (Wegener & Baggesen, 1996). In several industrialized countries, cases of human infection caused by this serovar have been described (Raevuori et al., 1978; Pelkonen et al., 1994). In Finland, *Salmonella* Infantis was described as the third most important serovar; it infects humans, and it is the most frequently isolated serovar in poultry (Pelkonen et al., 1994). In Hungary, the rate of occurrence of *Salmonella* Infantis has increased in the past

National and international regulations determine the absence of *Salmonella* spp. in 25 grams of sample, including poultry meat and eggs. In spite the technological development in food production and the adoption of better hygiene measures in the food production and handling, the incidence of human salmonellosis has increased in several parts of the world

In the US, there are more than 800,000 notified cases of infections caused by *Salmonella* spp., with an average of 500 deaths a year. Worldwide occurrence of salmonellosis is calculated in 1.3 billion cases and 3 million deaths (Thong et al, 1995). In 1988, there were 4 million cases of foodborne disease in the US and Canada, representing an estimated cost of US\$ 4.8 billion, including losses in commercialization, productivity and labor (Todd, 1989). In a fiveyear period (1985-1989), there were 189 outbreaks in the US caused only by *Salmonella*

Salmonellosis epidemiology and control are highly complex, and hygienic and sanitary standards vary with the region, based on feeding and cooking habits, and animal raising practices. Control of the disease is a challenge to public health because of the emergence/reemergence of serovars in different areas, both in developing and developed

Carriers are the most important epidemiological factors, because of the lack of symptoms, and the technical difficulty in detecting them before or during the inspection of foods of animal origin. Considering that the main route of transmission is in the food chain, the presence of this microorganism in production animals shows that *Salmonella* is the most incident and relevant etiological agent of intestinal infections. It causes million of dollars in losses to the industry, mainly in cattle, swine and poultry production, both in local and international trade. In some countries, rigid food inspection is a constant need to produce

Besides the importance of preventive measures against the risk of *Salmonella* infection in humans, control of salmonellosis has a positive economic impact in countries where outbreaks occur. Estimated costs of medical expenses, sick leaves and loss of productivity related to the high incidence of salmonellosis in the US range from US\$1.3 to US\$4.0 billion

As for fowl salmonellosis, paratyphoid *Salmonellae* are the most important ones in terms of animal and public health (Nascimento et al., 1997). These microorganisms remain in the intestinal tract of the birds, making poultry a possible source of foodborne infection for humans (Berchieri Jr., 1991). Transmission of *Salmonella* to men generally occurs by means of contaminated food and water, although person-to-person transmission may take place, mainly in hospitals. Transmission by contact with infected animals, mainly among veterinarians and farm workers (Trabulsi & Landgraf, 2004), is also possible. It should be emphasized that most serotypes in this genus are pathogenic to men; the differences observed in symptoms may be related to variation in the mechanisms of pathogenicity, age

and immune response of the host (Trabulsi & Landgraf, 2004; Hofer et al., 1997).

years both in the poultry industry and in humans (Nógrády et al., 2008).

(Anais de Toxiinfecção Alimentar, 1996).

countries.

foodstuffs of high quality.

a year (Taitt et al., 2004).

Enteritidis, with 6,604 people involved, and 43 deaths.

A large number of *Salmonellae* have to be ingested to cause gastroenteritis. Generally, the infective dose depends on the serotype, ranging from 2.0x102 to 1.0x106 CFU/g or mL (Huang, 1999). Variation in the symptoms is also related to the type of food and the species of *Salmonella* involved, once species that are adapted to men require lower infective doses to cause the same characteristics symptoms of the disease (Pinto et al., 2004).

*Salmonella* excretion in human and/or animal feces may contaminate the water, soil, other animals and foodstuffs. Animals are infected by direct contact with feces, contaminated water and food (Argôlo Filho, 2007). Because of the ability to disseminate and survive for a long period of time in the environment, *Salmonella* may be isolated from superficial freshwater bodies, from sea water in coastal areas, and from several raw materials used in food production (Jakabi et al*.,* 1999).

According to Nascimento (1996), contamination of poultry products (meat and eggs) destined for human consumption may occur at the slaughterhouse, during food preparation, or by cross-contamination with material from poultry with intestinal and systemic infections. As for poultry meat, even a small number of infected birds may contaminate the whole slaughter line, multiplying the chances of occurrence of foodborne disease. Because of that, slaughterhouses where carcasses are not correctly processed are a threat to public health (Nascimento, 1996); current practices of broiler slaughtering and processing may spread microorganisms from one carcass to another. When consumed, the product may be responsible for human infection (Santos, 2004). Although broiler carcasses may be contaminated with *Salmonella* Enteritidis, eggs and egg by-products - mainly homemade mayonnaise – are the main products responsible for outbreaks of the disease in humans (Silva, 2000).

Transmission of *Salmonella* in birds may occur vertically, via eggs, with the birth of infected chicks; horizontally, by means of ingestion of water, feed, fecal material, contaminated bedding material or dust; or by oral, nasal, conjunctival, cloacal and umbilical routes (Cox et al., 1996; Navarro, 1995; Nascimento, 1996). Many *Salmonella* serotypes may survive for weeks or months in manure or bedding material, in equipments, in empty sheds, in the dirt around sheds that have been cleaned and disinfected, in feces of wild poultry, in dust particles, and in bird feeders. According to these authors, *Salmonella* may survive in contaminated feed for 26 months, in feces of infected birds for more than 11 days when inside of sheds, or for 9 days in open spaces. Besides, domestic and wild animals may be carriers of *Salmonella*, spreading the microorganism in the environment where they live. These bacteria may cause acute and/or chronic disease in susceptible animals. As stated before, the epidemiological complexity of the disease, which involves vertical transmission, fecal excretion, horizontal transmission, environmental contamination and presence of carriers in different species, make salmonellosis control difficult to be achieved (Soncini & Back, 2001).

*Salmonellae* are distributed all over the world. Multiplication outside the body of the host is facilitated by high temperatures and presence of protein (for example, in residual waters). Therefore, the most important points of transmission of *Salmonella* are tropical and subtropical regions, as well as places where there is a large concentration of animals and people. *Salmonella* may also be found in products refrigerated at 2°C; the microorganism is able to remain viable in frozen products for long periods.

After entering the digestive system together with contaminated food and water, *Salmonellae* reach the intestines, where they attach to intestinal cells and multiply. Depending on the host species and age, and on the pathogenicity of the microorganism

Important Aspects of Salmonella in the Poultry Industry and in Public Health 189

feed containing contaminated fish meal that came from Peru. This case is an example of the

The intensive breeding system adopted by the poultry industry favors the introduction, establishment, permanence and dissemination of these bacteria (Berchieri Jr. & Freitas Neto, 2009). Therefore, the stage when animals are raised is very important in the dissemination of *Salmonella* spp. among the birds, and consequently, in giving rise to contaminated food products (Bersot, 2006). *Salmonella* may affect all segments of poultry production, such as breeder facilities, incubators, commercial raising operations, feed factories, slaughterhouses,

Globalization incorporated the sanitary restrictions imposed by the European Community to international traders of foods of animal origin, mainly poultry. The occurrence of cases of foodborne infection linked to *Salmonella* Enteritidis and *Salmonella* Typhimurium show the sanitary importance of Brazilian poultry production, in social and economic terms. When the World Trade Organization (WTO) was created, the guidelines and Codex Alimentarius regulations were determined for international trade, and for agreements on sanitary and phytosanitary (SPS) measures and technical barriers to trade (TBT). With these agreements, WTO country members should review, establish and implement internal control systems,

*Salmonellae* are short Gram-negative bacilli, about 0.7-1.5 x 2-5 μm, readily stained, and nonsporulating. Most of them move using peritrichial flagella, although serotypes such as *Salmonella* Pullorum and *Salmonella* Gallinarum are nonmotile. They are either aerobic or facultative anaerobic, and grow between 5 and 45°C. Optimum growth occurs at 37°C. Ideal pH for multiplication is 7, but *Salmonella* survives in pH values between 4 and 9. They grow in culture medium for enterobacteria and in blood agar. Colonies are 2-4 mm in diameter, with smooth and round edges. They are slightly raised in medium containing carbon and nitrogen. Colonies may remain viable for a long time when stored in peptone (Holt et al.,

Biochemically, *Salmonella* strains have the ability to metabolize nutrients, and catabolize Dglucose and other carbohydrates, except lactose and sucrose, with production of acid and gas. They are catalase positive and oxidase negative, as are all genera in the *Enterobacteriaceae* family. They do not ferment malonate, do not hydrolyze urea, do not produce indol, use citrate as a sole source of carbon, reduce nitrate to nitrite, and may

Conventional culture methods for isolating *Salmonella* spp. in poultry or animal feed or in feed ingredients have been reported in a number of studies, which were summarized by Williams (1981). Although all methods follow the basic strategy of preenrichment followed by selective enrichment, differential plating and biochemical or serological confirmation,

The Food and Drug Administration (FDA), for example, recommends lactose broth for preenrichment (Andrews el al*.* 1998), while Wyatt et al*.* (1993) used buffered peptone water. Cox et al. (1982) reported that preenrichment decreased the recovery of *Salmonella* spp. from artificially contaminated poultry feed when compared with direct enrichment. Suggested protocols also vary with the substrate: Kafel (l981) suggested the use of anaerobic lactose broth, followed by selection in tetrathionate brilliant green broth and plating on brilliant

there is no single internationally accepted procedure for *Salmonella* spp. detection.

that is, adopt the Hazard Analysis and Critical Control Points System (HACCP).

epidemiological complexity of this disease.

**4. Detection methods**

1994; Gast, 1997).

produce hydrogen sulfide (Quinn et al., 2000).

transportation systems and commercialization facilities.

and its adaptation to the host, *Salmonellae* may cause severe disease, or go unnoticed and remain in the host for months or years. In this case, the host will be a reservoir of the bacteria for susceptible animals.

The most common symptoms include diarrhea, abdominal pain, vomit and nausea, and may occur together with prostration, muscle pain, drowsiness and fever. Although symptoms generally disappear after 5 days, the microorganisms may be excreted in the feces for many weeks (Jay, 1992). Children, mainly those younger than 1 year of age, elderly and immunocompromised patients are much more susceptible to the disease, and may present more severe infections, such as sepsis, which may lead to death (Gomez & Cleary, 1998; Pinto et al., 2004)

Salmonellosis is not limited to intestinal infection and gastroenterocolitis. The microorganism may infect other organs; as *Salmonellae* are able to reach the circulation, they may cause diffuse extraintestinal infections, such as meningitis, osteomyelitis, arthritis, pneumonia, cholecystitis, peritonitis, pyelonephritis, cystitis, endocarditis, pericarditis, vasculitis and other disorders (Gelli, 1995).

*Salmonellae* cross the intestinal epithelium, and reach the *lamina propria* (the layer where epithelial cells are anchored), where they multiply. They are phagocyted by macrophages and monocytes, causing an inflammatory response as a consequence of the hyperactivity of the reticuloendothelial system. Different from what happens in typhoid fever, penetration of *Salmonella* spp. is limited to the *lamina propria* in cases of enterocolitis. In these cases, sepsis or systemic infection are rarely observed, and infection is restricted to the intestinal mucous membrane. Inflammatory response is also related to the release of prostraglandins, which stimulate adenylate cyclase, leading to increased secretion of water and electrolytes and aqueous diarrhea (Franco & Landgraf, 2004).

From 1980 on, human outbreaks caused by *Salmonella* Enteritidis, showed common sources in the US, Great Britain and other European countries (CDC, 2005). Epidemiological surveys from the CDC identified the consumption of eggs or egg-based foods as responsible for most of the outbreaks involving specific phagotypes (PT) of *Salmonella* Enteritidis; PT-4 in European countries, and PT-8 and PT-13a in the US (Perales & Audicana, 1989). The predominant serotypes involved in foodborne diseases changed, in the past decades, from *Salmonella A*gona, *Salmonella* Hadar and *Salmonella* Typhimurium to *Salmonella* Enteritidis, which is the predominant cause of salmonellosis in several countries (Suresh et al., 2006). Changes in the predominance of serotypes reflect changes in animal raising practices and dissemination of new serotypes due to increased international trade. Nowadays, the main concern is the emergence of *Salmonella* serotypes that are resistant to multiple antibiotics (Huang, 1999).

Cases of disease caused by four serovars of subspecies *enterica* are subject to mandatory reporting, according to regulation number 207 of the Brazilian Agency of Agricultural Defense [SDA; *Secretaria da Defesa Agropecuária*] , reviewed in July 30th, 1995. These serovars are part of the list B of the World Organization for Animal Health (OIE), of diseases that cause regional economic losses. Among them, *Salmonella* Pullorum, Gallinarum, Typhimurium and Enteritidis. About 90 serovars of *Salmonella* spp. are more frequent in cases of human and animal infection (Berchieri Jr. & Freitas Neto, 2009).

The typification of serovars is important to track the source of infection. For example, *Salmonella* Agona affected humans in the US, in European countries and in Brazil (Synnott et al., 1998; CDC, 2007). According to Clark et al. (1973), human outbreaks in the US and Europe that occurred around 1970 were caused by poultry meat. Animals were infected by feed containing contaminated fish meal that came from Peru. This case is an example of the epidemiological complexity of this disease.

The intensive breeding system adopted by the poultry industry favors the introduction, establishment, permanence and dissemination of these bacteria (Berchieri Jr. & Freitas Neto, 2009). Therefore, the stage when animals are raised is very important in the dissemination of *Salmonella* spp. among the birds, and consequently, in giving rise to contaminated food products (Bersot, 2006). *Salmonella* may affect all segments of poultry production, such as breeder facilities, incubators, commercial raising operations, feed factories, slaughterhouses, transportation systems and commercialization facilities.

Globalization incorporated the sanitary restrictions imposed by the European Community to international traders of foods of animal origin, mainly poultry. The occurrence of cases of foodborne infection linked to *Salmonella* Enteritidis and *Salmonella* Typhimurium show the sanitary importance of Brazilian poultry production, in social and economic terms. When the World Trade Organization (WTO) was created, the guidelines and Codex Alimentarius regulations were determined for international trade, and for agreements on sanitary and phytosanitary (SPS) measures and technical barriers to trade (TBT). With these agreements, WTO country members should review, establish and implement internal control systems, that is, adopt the Hazard Analysis and Critical Control Points System (HACCP).