Salmonellosis Case Study Essay

Question 1: How is salmonellosis diagnosed? How does the method of diagnosis impact our understanding of the occurrence of salmonellosis in the community (e.g., burden of disease, trends over time, high-risk populations)?
Diagnosis of salmonellosis involves testing a sample of stool, as well as isolation from samples of tissue, blood, or urine. Since it is commonly mistaken for the flu and involves similar symptoms to other illnesses, the method of diagnosis for salmonellosis is pretty hard to come by. Most people with salmonellosis don’t seek treatment, so they’re never aware that they even had it. Since it is a foodborne pathogen, has a common route of infection via oral ingestion, and is found in food products that we consume on a daily

basis (milk, meat, eggs, etc.), the burden of disease is high. Immunocompromised persons, owners of reptiles, birds, etc. and international travelers are more susceptible to this illness. Also, everyone does (if not, should) understand the importance of handwashing as well as proper food prep.
Question 2: Describe how serotype results can be used in public health practice.

In public health practice, serotype results can be used to determine which particular isolate was the source of Salmonella in a case. If epidemiologists find that one main isolate is a common factor to the source of numerous of different cases, then they can use whatever measures to control possible outbreaks of Salmonella in the population. Also, health interventions can be put into place if they determine which food sources are the main cause of Salmonella.

Question 3: To detect outbreaks of infectious diseases (e.g., salmonellosis) and investigate risk factors for infection, what characteristics should a communicable disease surveillance system have?

A communicable disease surveillance system should have characteristics that involve: gathering information, analyzing/interpreting, and distributing data to members of the community (including health workers). It also should monitor outbreaks in the community along with those risk factors for infection/chronic diseases.

Question 4: Diagram the flow of information in the Caribbean communicable disease surveillance system.

Question 5: Evaluate the Caribbean communicable disease surveillance system with respect to the desired goals of outbreak detection and investigation of risk factors for infection. What changes would you make to the surveillance system? Why?
I would improve the timeliness/sensitivity of reporting because it is best if outbreaks are brought to the attention of health care workers, the community, and clinical lab staff as soon as possible, for timely implementation of effective control measures. I’d also improve communication and require lab confirmations for diseases to improve efficiency. .
Question 6: What might be done to encourage acceptance of the surveillance system and improve reporting?
To encourage acceptance and improve reporting of the surveillance system, clinical labs and health care providers should be informed about the purpose of the system, then continue with teaching them exactly how to use it. The system should be easily manageable, not too difficult. Additionally, feedback should be given, so that healthcare providers know whether they are within the guidelines of the system and what exactly to change. They should also have multiple ways of submitting reports (via phone, fax, etc.).
Question 7A: Calculate the incidence of laboratory-confirmed salmonellosis (all serotypes combined) for Trinidad and Tobago in 1997. (Assume that only one isolate was received for each patient. The population of Trinidad and Tobago was estimated to be 1,265,000 in July of 1997.)
* incidence rate=(# of new cases)/(total population at risk) over a time period x multiplier
incidence of lab-confirmed salmonellosis: 109/1,265,000= 8.617 x 10-5 = 9 isolates / 100,000 people per year
Question 7B: The annual incidence of laboratory-confirmed Salmonella infections in Trinidad and Tobago is approximately 9 per 100,000 populations. Assume that: 1) approximately one in every 10 people with diarrhea go to the doctor, 2) doctors request submission of a stool specimen from approximately one in every 10 patients with diarrhea that they see, and 3) approximately two in every three stool specimens are properly tested for Salmonella and are reported through the surveillance system. Given these assumptions, what is the true burden of Salmonella in Trinidad and Tobago?
*Multiplier of 150 because 10 (1 in 10 people w/ diarrhea) x 10 (1 in 10 patients seen) x (2 in every 3 tested stool specimens) 1.5 = 150
true incidence (burden)=9/100,000 x 150=0.0135 x 100,000=1,350 cases of Salmonella/100,000 pop.in Trinidad and Tobago
Question 8: Create a line graph of the number of Salmonella isolates by serotype by year of diagnosis for Trinidad and Tobago from 1988 to 1997. Interpret the graph.

By looking at the graph, you can see that in the early 90s, Typhimurium was most prevalent and in the late 90s it shifted to Enteritidis. Although, enteritidis was stagnant until ‘92. “Other” serotypes just drifted along the middle. Also, it’s likely that the increases of isolation may have been a result of introduction to surveillance methods.
Question 9: Interpret the grouped bar chart of laboratory-confirmed S. Enteritidis cases by age group. What age group(s) is at highest risk for infection?
This bar graph compares cases of S. Enteritidis infection of people between the age groups of 0 to over 50 years old. Laboratory-confirmed S. Enteritidis cases for 20-49 year olds tend to have the least amount of risk. Children from the age of 0 up to 4 years old are at highest risk for infection.
Question 10: Describe the occurrence of S. Enteritidis infection in Trinidad and Tobago by month of diagnosis?
During the months of March and April of 1996, there were large increases in the number of cases. September was the month of the least amount of cases total. Just as the number of cases were wavering but dwindling down as the months passed along, December saw a bit of a spike in cases.
Question 11: What is the measure of association in a case-control study? How is it interpreted?
In this case-control study, we had the case group (patients with S. Enteritidis infection) and the control group (people who shared the same neighborhood with the infected but had no diarrheal illness in the previous 4 weeks). The measure of association is the risk ratio of an event (relative risk) or the ratio of the odds of an event (odds ratio). Risk ratio is interpreted as the probability of an event with vs. without infection. Odds ratio is easiest to interpret when first converted to risk ratio.
Question 12: Interpret the odds ratios for the above exposures. What exposures appear to be risk factors for S. Enteritidis infection in Trinidad and Tobago?
The exposures in the associated cases are based in the 3 days before onset of the illness. Buying refrigerated eggs is an exposure with the lowest odds. Eating ground beef and being exposed to live chickens both have an odds ratio of 1.3. Eating dishes that contain raw or undercooked eggs or eating shell eggs appear to be risk factors for S. Enteritidis infection in Trinidad and Tobago.
Question 13: Discuss possible interpretations of the same phage type among Salmonella isolated from patients with salmonellosis and suspect food samples.
This could possibly mean that if either of these foods are consumed (especially by immunocompromised people), then there is a great chance of them getting Salmonella. It could also mean that the food and Salmonella share the same strain of bacteria.
Question 14: What control measures would you consider at this point?
At this point, I’d consider reiterating to the community the importance of handwashing, proper food prep, and being careful around animals (especially reptiles). Also, I’d let them know to avoid cross-contamination and don’t go from handling raw meat to playing with an infant.
Question 15: Why were the eggshells cultured separately from the egg contents? Why were the eggs sanitized before the contents were cultured?
The eggshells were cultured separately from the egg contents to better determine whether the egg shells or its contents had the greater source of Salmonella.

Also, to see if there were different serotypes between the egg vs. egg content cultures. The eggs were sanitized as part of a control measure to see whether that can be a method for eliminating the Salmonella.
Question 16: What specific activities would you undertake as part of an environmental health assessment of the egg-producing farms?
I would test the quality of air/water supply on the farms. I’d also carefully examine and possibly test the chickens who laid the eggs for possible infection (including their daily feed and litter type). I’d take notes of the kinds of animals/insects that roam the farms. Lastly, I’d involve the community by educating them on ways to prevent Salmonella and properly handle the eggs.
Question 17: What food safety practices at the egg-producing farms might help prevent or reduce the risk of salmonellosis from the consumption of eggs from these farms?
Reducing the risk of salmonellosis from these farms would include food safety practices such as: washing eggs and hands thoroughly, making sure that the farm is kept in good condition, feeding the chickens good food, and using fresh water

sources.
Question 18: In addition to the testing of eggs and flocks for Salmonella, how might you monitor the impact of Salmonella control measures in Trinidad and Tobago?
I might monitor the impact by viewing the number of Salmonella cases in people in the community. I’d also monitor the farms to see if farmers are practicing good techniques. Testing of the food from local markets, restaurants, etc. might also be measured.