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 Table of Contents  
Year : 2018  |  Volume : 21  |  Issue : 2  |  Page : 99-103

Prevalence and knowledge of Salmonella infections among food handlers: Implications for school health in Southwestern Nigeria

1 Department of Community Medicine, Faculty of Clinical Sciences, University of Medical Sciences Ondo Nigeria, Osogbo, Osun, Nigeria
2 Central Laboratory Unit, Osun State Hospital Management Board, Osogbo, Osun, Nigeria
3 Department of Microbiology, Ladoke Akintola University of Technology Teaching Hospital, Osogbo, Osun, Nigeria

Date of Web Publication6-Jul-2018

Correspondence Address:
Dr. Adebimpe Wasiu Olalekan
Department of Community Medicine, College of Health Sciences, Osun State University, PMB 4494, Osogbo, Osun
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DOI: 10.4103/smj.smj_27_16

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Background: Food handlers play important roles in transmission of Salmonella infections in unregulated school food programs, most especially in settings where surveillance of foodborne disease is not routine. This study assessed the determinants and prevalence of Salmonella infections among food handlers and its implications for public school health in Southwestern Nigeria. Materials and Methods: A cross-sectional descriptive study among 526 food handlers was carried out using semi-structured interviewer-administered questionnaires. Stool collection and laboratory procedures were carried out under standard techniques. The SPSS software version 17.0 was used in data analysis. Frequency tables and charts were generated while binary logistic regression was used to demonstrate predictors of Salmonella infections, and P ≤ 0.05 was considered statistically significant. Results: The mean age of the respondents was 33.0 ± 7.6 years, 504 (95.8%) were females, and 378 (71.9%) were in the lowest socioeconomic class. Two hundred and seventy-seven (52.7%) had poor, 101 (19.2%) had moderate, while 148 (28.1%) had good knowledge scores as regards transmission, prevention, and control of Salmonella infections. Twenty-two (4.2%) had positive, 18 (3.4%) had indeterminate, while 486 (92.4%) had negative test results to Salmonella infections. Predictors of positive test results were being in the lower socioeconomic class, being a female and using pit toilets. Conclusion: Food handlers studied had significant prevalence rate and poor knowledge of Salmonella infections. Improving their knowledge could bring about a positive behavioral change toward a successful school feeding program.

Keywords: Prevalence, Salmonella infections, school food vendors, Southwestern Nigeria

How to cite this article:
Olalekan AW, Oluwaseun FA, Oladele HA. Prevalence and knowledge of Salmonella infections among food handlers: Implications for school health in Southwestern Nigeria. Sahel Med J 2018;21:99-103

How to cite this URL:
Olalekan AW, Oluwaseun FA, Oladele HA. Prevalence and knowledge of Salmonella infections among food handlers: Implications for school health in Southwestern Nigeria. Sahel Med J [serial online] 2018 [cited 2020 Feb 20];21:99-103. Available from: http://www.smjonline.org/text.asp?2018/21/2/99/236062

  Introduction Top

Consumption of safe food ensures minimal risks and hazards to human health through protecting and preventing edible substances from becoming hazardous in the presence of chemical, physical, and biological contaminants.[1] In ensuring this, food handlers play important roles in ensuring food safety throughout the chain of production, processing, storage, and preparation of food.[2],[3] Whenever foods are mishandled and contaminated, consequences could include food poisoning and spread of disease.[2],[4],[5]

Poor level of knowledge of food hygiene and safety has been reported among many food handlers with attending influence on their practice. Such contamination of food with eggs and cysts, especially those hawked by food vendors, may also serve as a source of infection to consumers of such items.[2],[3] According to the World Health Organization (WHO), diarrheal diseases, mostly caused by foodborne or waterborne microbial pathogens, are leading causes of illness and deaths in developing countries, killing an estimated 1.9 million people annually at the global level.[6]

Fecal contamination with food, water, nails, and fingers etc., may suggest the importance of fecal-oral human-to-human transmission. Accordingly, food handlers with poor personal hygiene working in food-serving establishments could be potential sources of infections including  Salmonellosis More Details, with the potential of causing diarrheal diseases. Although governments all over the world are doing their best to improve the safety of food supply, the occurrence of foodborne disease remains a significant health issue in both developed and developing countries according to the WHO in 2006.[6]

Despite this, reliable statistics on foodborne diseases are not available due to poor or nonexistent reporting systems in most developing countries [7] coupled with the fact that surveillance of foodborne disease may not be a routine or active in this part of the world.

Some state governments in Southwestern Nigeria offer free education to students in both primary and secondary schools, with free school meal as a component of the program in primary schools.

To this effect, the need to conduct screening tests for food handlers employed into the program becomes imperative since they cook and handle food in the various schools. The objective of this study was to determine the prevalence of  Salmonella More Details infections among food handlers and its implications for public school health in Southwestern Nigeria.

  Materials and Methods Top

Study area

Osun is a state in Southwestern region of Nigeria, with Osogbo town as the state capital. The state has a population of about 3.2 million at the last national census with a rural-to-urban ratio of 1.4.[8] Majority of inhabitants are farmers, traders, artisans, and civil servants. Good road network, fairly stable electricity, and functional and accessible health facilities characterized the urban areas compared to rural. There are over 200 public and private primary and secondary schools in the state, and the state government is currently running free mid-day school feeding program in public schools. A total of 1260 food vendors were employed and registered into the government-sponsored school feeding program.

Study design

This was a cross-sectional study to determine the prevalence of Salmonella infections among food handlers and its implications for public school health in Southwestern Nigeria. This study was carried out between January and March 2015.

Study population

The study population included all 1260 registered food handlers currently engaged in the “O meal” program of the Ministry of Education in Osun State. Only vendors who were directly involved in cooking, processing, and serving of food to students and pupils were eligible for the study. Food handlers who refused to give their consent or who were not registered nor employed by this public service were excluded from the study. Food handlers who took medications for an intestinal ailment in the last 3 months were also excluded from this study. Only two of such ineligible vendors were found.

Sample size estimation

Using the Leslie Fischer's formula for calculation of sample size for single proportions,[9] the calculated minimum sample size was 480, and this was increased to 540 for better representation and to account for attrition and poor or incomplete responses.

Sampling method

A multistage sampling technique was used as follows:

  • Stage 1: From the list of the 3 senatorial zones in the state, 2 zones were selected using simple random sampling technique (balloting)
  • Stage 2: From the list of 10 local government areas (LGAs) in each of the senatorial zones, 8 were selected, respectively, using simple random sampling technique (balloting)
  • Stage 3: On every sample collection day, a list (sampling frame) of all food vendors present was drawn. A systematic sampling of one in 3 food vendors was used in selecting food vendors for the test, with the first food vendor randomly selected as the starting point.

In case, the allocated number of questionnaires was exhausted in any LGAs, another LGA was selected from the list, and respondents recruited as earlier explained until all questionnaires were filled.

Data collection

This included interviewed administered, semi-structured, precoded, and pretested questionnaires conducted by 8 trained and qualified laboratory scientists or research assistants/co-researchers who could also speak local language. A vernacular (Yoruba language) version of the questionnaire was prepared for the uneducated respondents to reduce inter-observer variation in interpretation during the interview, and this was back translated into English language by an independent research collaborator. Sections in the questionnaire included sociodemographic variables, knowledge about personal hygiene, and safety and results of Salmonella screening test done.

Sample collection and stool examinations

Direct smear examination for stool samples was carried out on a glass microscope slide, and about 1–2 mg of stool was emulsified in a drop of normal saline (0.85% NaCl) on the left and Lugol's iodine on the right side of the slide. A coverslip was then placed on each side, and the slides were scanned under ×10 and ×40 objective lenses of a light microscope, as required. Stool sample was collected medical laboratory technicians from each case in a clean stool cup. The samples were cultured into the plates of Salmonella-Shigella agar (Oxoid), and after incubation for 24 h at 37°C, the plates were examined, and bacterial species were identified following standard procedures.[10] The formalin-ether concentration sedimentation procedure was also followed to check for intestinal parasites in the stool samples.[11]

Ethical consideration and limitation

Ethical approval to conduct this study was obtained from the Research Ethics Committee of Lautech Teaching Hospital, Osogbo 10th September 2014. Approvals were also obtained from the local authorities of the free food program, as well as written informed consent from each food handlers. They were assured of confidentiality and privacy of information collected.

Data management

The Statistical Package for Social Sciences software version 17.0 (SPSS Inc, Chicago, IL, USA was used for data entry and analysis. Validity of data collected was ensured by double entry and random checks for errors. Socioeconomic class of the women was based on the occupational classification of their husband or spouse. A 15-point rating scale was used to assess the respondents' knowledge on food safety and hygiene as well as Salmonella infection with a maximum attainable score of 15. A score of 0–5 points was graded/assessed as poor knowledge, 6–10 moderate knowledge, and scores of 10 and above as good knowledge.

The professional occupations were put in Class 1 (highest socioeconomic class), the skilled labor in Class II, the semi-skilled in Class III, and the unskilled occupations in Class IV (lowest socioeconomic class). Occupation was eventually recategorized into high (Classes I and II) and low (Classes III and IV) for inferential analysis. A binary logistic regression was used to determine factors that predict positive Salmonella test result. A 95% confidence interval (CI) was used in the study and P ≤ 0.05 considered statistically significant.

  Results Top

A total of 526 out of the estimated 540 food vendors completed this study giving a response rate of 97.4%. The mean age of respondents was 33.0 ± 7.6 years with about 248 (47.2%) being in the 30–39 age group. Twenty-two (4.2%) were male, 419 (79.7%) were married, 97 (18.4%) lived in rural area, 68 (12.9%) lived in slum areas, and 372 (70.7%) lives in the inner city. Three hundred and fifty-six women (67.7% of total respondents) were in the lowest socioeconomic class while 21 (4.0%) were in the highest socioeconomic class.

Two hundred and twelve (40.3%) used pit latrine while 103 (19.6%) practice open defecation, 434 (82.5%) dumped their refuse openly, while only 131 (24.9%) had tap water as source of water [Table 1]. Concerning the prevalence and pattern of Salmonella infection among respondents in this study, 22 (4.2%) had positive, 18 (3.4%) had indeterminate, while 486 (92.4%) had negative results, respectively [Figure 1]. Two hundred and seventy-seven (52.7%) had poor, 101 (19.2%) had moderate, while 148 (28.1%) had good knowledge scores as regards transmission and prevention and control of Salmonella infections shown in [Figure 2].
Table 1: Socioeconomic characteristics of respondents

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Figure 1: Bar chart showing composite mean knowledge score of respondents about Salmonella infections and food hygiene practice

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Figure 2: Bar chart showing pattern (percentage) of Salmonella infection results among respondents

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According to [Table 3], respondents with lower socioeconomic status were 1.8 times more likely to have a positive Salmonella results than those in the higher socioeconomic class (odds ratio [OR]: 1.80, 95% CI: 0.276–2.138 and P = 0.300). Respondents using pit toilets were 3 times more likely to have a positive test result compared to those using nonpit toilets (OR: 3.10, 95% CI: 1.230–7.818 and P = 0.007). Female respondents were also 2.5 times more likely to have positive test results compared to males (OR: 2.40, 95% CI: 0.520–11.073 and P = 0.1450) though this observation was not statistically significant according to [Table 2].
Table 2: Knowledge of respondents about Salmonella infections (“Yes” options only)

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Table 3: Binary logistic regression of factors predicting positive Salmonella test result

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  Discussion Top

The socioeconomic characteristics of respondents in this study showed that females were more engaged as food vendors than their male counterparts, and this supports the findings of some other Nigerian studies.[12],[13] Sources of water and types of toilets used by respondents were also in agreement with findings of studies conducted elsewhere.[12],[13]

The prevalence of Salmonella infection found in this study also agreed with what was obtained in another study conducted in Ethiopia which reported a prevalence of 6.5%.[14] The two countries are developing and may probably have the same level of exposure based on prospect for infectious disease control measures.

The poor knowledge of transmission and control and prevention of Salmonella infection agreed with other studies.[12],[13] However, a slightly higher knowledge score was reported in another related study.[15] Good knowledge of food safety and hygiene could contribute to positive attitudes toward prevention of Salmonella infection, as well as taking appropriate actions and seeking medical care in the event of a food handler having infective diarrheal disease.

Salmonella infection is transmitted through fecal-oral route. Predictors of positive test results were being in the lower socioeconomic class, being a female and using pit toilets; and this trend could be explained. Gender being a predictor of Salmonella infection could be because women usually keep long nails in the name of fashion or manicure, and this could serve as a potential disease reservoir. In addition, people with lower socioeconomic status are likely to have a higher probability of using less sanitary sewage disposal system (such as pit latrine) that may predispose them to free handling of feces and contamination of water and surface soil with feces and infective microorganism. Significant prevalence level could hinder health in two ways. First is the high chance of many food handlers becoming a chronic carrier of the Salmonella infection with poor prospect for disease control. Second, school pupils have a high chance of contracting this disease directly from infected food handlers most especially in schools with inadequate sanitation. These observations have been supported by several other studies.[12],[13],[14],[15],[16]

  Conclusion Top

Food handlers studied had significant prevalence rate and poor knowledge of Salmonella infections. It is important that the food handlers are well informed about the cause, transmission, and ways by which typhoid fever spreads toward effective disease control and a successful school health and food program.


The authors are grateful to the medical directors of the health facilities where data were collected and the individual food handlers who gave written informed consent toward participation in this study.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

Majara O. Food safety and knowledge of hygienic practices among hoteliers. Daily Mirror 2010;20:3-6.  Back to cited text no. 1
Chukwuocha UM, Dozie IN, Amadi AN, Nwankwo BO, Ukaga CN, Aguwa OC, et al. The knowledge, attitude and practices of food handlers in food sanitation in a metropolis in South Eastern Nigeria. East Afr J Public Health 2009;6:240-3.  Back to cited text no. 2
Okojie OH, Wagbatsoma VA, Ighoroge AD. An assessment of food hygiene among food handlers in a Nigerian university campus. Niger Postgrad Med J 2005;12:93-6.  Back to cited text no. 3
Viedma Gil de Vergara P, Colomer Revuelta C, Serra Majem L. Assessment of the effectiveness of health training courses offered for food handlers in a health care district of Gandía, Valencia. Rev Esp Salud Publica 2000;74:299-307.  Back to cited text no. 4
Claytona DA, Griffitha CJ, Priceb P, Adrian CP. Food handlers' beliefs and self-reported practices. Int J Environ Health Res 2002;12:25-39.  Back to cited text no. 5
World Health Organization. “Five Keys to Safer Food Manual”; 2006. Available from: http://www.who.int/foodsafety/publications/consumer/manual_keys.pdf. [Last accessed on 2013 Jul 24].  Back to cited text no. 6
World Health Organization. Prevention and Control of Intestinal Parasitic Infections. Geneva: World Health Organization; 1987. p. 7-18.  Back to cited text no. 7
National Population Commission (NPC). Nigeria Demographic and Health Survey. Calverton, Maryland: NPC and ORC Macro; 2006. p. 45-7.  Back to cited text no. 8
Araoye MO. Sampling methods. In Research Methodology with Statistics for Health and Social Sciences. Ilorin, Nigeria: Nathadex Publishers; 2004. p. 117-20.  Back to cited text no. 9
Bailay WR, Scott ES. Diagnostic Microbiology. 4th ed. Saint Louis: Mosby; 1994.  Back to cited text no. 10
Beaver PC, Jung RC, Cupp EW, editors. Examination of specimens for parasites. In: Clinical Parasitology. Philadelphia: Lea and Fabiger; 1984. p. 733-58.  Back to cited text no. 11
Smith SI, Agomo CO, Bamidele M, Bolanle OO, Olusimbo OA. Survey of food handlers in bukas (a type of local restaurant) in Lagos, Nigeria about typhoid fever. Health 2010;2:951-6.  Back to cited text no. 12
Jennifer JO. Food-borne illness incidence rates and food safety risks for populations of low socioeconomic status and minority race/ethnicity: A review of the literature. Int J Environ Res Public Health 2013;10:3634-52.  Back to cited text no. 13
Jiwa SF, Krovacek K, Warstrom T. Enteropathogenic bacteria in food and water from an Ethiopian community. Appl Environ Microbiol 1981;41:1010-9.  Back to cited text no. 14
Varga C, Pearl DL, McEwen SA, Sargeant JM, Pollari F, Guerin MT. Evaluating area-level spatial clustering of Salmonella enteritidis infections and their socioeconomic determinants in the greater Toronto area, Ontario, Canada (2007–2009): A retrospective population-based ecological study. BMC Public Health 2013;13:1078.  Back to cited text no. 15
El-Sherbeeny MR, Saddik MF, Bryan FL. Microbiological profile of foods served by street vendors in Egypt. Int J Food Microbiol 1985;2:355-64.  Back to cited text no. 16


  [Figure 1], [Figure 2]

  [Table 1], [Table 2], [Table 3]


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