THE OCCURRENCE OF TYPHOID
Typhoid occurs worldwide . It is more common in developing countries due to poor sanitary conditions and it is most common in underdeveloped areas . Typhoid is endemic in Africa , Asia, Latin America, Caribbeans and Oceania.
Typhoid fever infects approximately 21.6 million (3.6 per 1000 population) per year.
It kills an estimated 200,000 people every year.
Typhoid has no racial preferences. It mostly affects males than females due to hygienic purposes. It is common in school aged children and young adults.
It is uncommon but not absent in babies <6 months of age.
Occurrence increases steeply between 6 and 12 months of age.
It is as common among 1-2 year old as 2-5 year olds and severe among 5 year olds.
TYPHOID OCCURRENCE IN ZAMBIA
A number of typhoid outbreaks have been recorded in different African countries such as the Democratic Republic of Congo, Uganda, Malawi, Zambia, South Africa, Mozambique and the Ivory Coast.Between January 2010 to September 2012, Zambia recorded a total of 2,040 typhoid cases with a case fatality rate of. 0.5%. The disease mostly affected children less than 15 years with an even distribution of males and females.
In 2016, Zambia recorded a total of 414 typhoid cases. There was more than 50% increase in suspected cases compared to the previous year. 730 suspected cases were recorded in 2018 showing a 40% reduction from 2017.
The majority of suspected cases occurred in 2017 and 18. Lusaka province had the highest number of typhoid suspected cases in 2017 and 2018. In 2016, Northern Province had more suspected cases than Lusaka province. Central province reported zero suspected cases of typhoid in 2016 and 2018. Overall, Central province recorded the lowest number of suspected typhoid cases in the time series of 2016 to 2018. (BM Katemba, EM Musakakanya , B Gianneti, C Groenvelt , Zambia Public Health Institution )
TYPHOID OCCURRENCE IN ZAMBIA BY YEAR
2016
2017
2018
414
1035
730
(Intergrated Disease Surveillance and Response)
GLOBAL. OCCURRENCE
Typhoid occurs between time and place and varies between countries. It is endemic worldwide but more common in warm countries like Africa, Latin America and South-east Asia.
Reviewed available data on outbreaks ( WHO)
- 41 published reports 1990 - 2017
- mean 1,097 cases per outbreak
Among the 35 distinct outbreaks
- 10 (28.6%) southeast Asia region
- 8 (22.9%) Africa region
- 14 (40.0%) exceeded 100 days duration.
PUBLIC HEALTH IMPORTANCE OF TYPHOID
Globally
Estimating the global burden of typhoid fever
After incidence rates were extrapolated within and between regions and between age groups, the total number of typhoid fever cases in 2000 was calculated by age stratum for each region. The sum of total cases by region was calculated as the crude global typhoid fever burden. Because eligible studies of typhoid fever incidence usually used a single blood culture collection to confirm cases, it was necessary to adjust the crude estimate for the global typhoid fever burden to account for under-detection of cases resulting from the limited sensitivity of blood culture for diagnosis of typhoid fever. The blood culture adjustment factor was derived from published literature (12–14). The lower reported sensitivity of 50% (13) was selected in an effort to account for the impact of antimicrobial use on blood culture sensitivity. The specificity of blood culture for the diagnosis of typhoid fever was assumed to be 100%.
Case-fatality rate
Studies on the incidence of typhoid fever were further reviewed for population-based case-fatality rate estimates. Hospital-based typhoid fever case series and case-fatal
Extrapolating between countries
Because eligible studies of typhoid fever incidence were not available for every country or region, it was necessary to extrapolate typhoid fever incidence from one country to another within a region and sometimes from one region to another. Extrapolations between countries and regions were based on geographical proximity and United Nations socioeconomic indicators (11).
Extrapolating between age groups
A large proportion of eligible studies of typhoid fever incidence were conducted among age cohorts representing a narrow age range (for example, school-aged children). Therefore, to adjust the incidence obtained from such measurements to that of the general population in a region, typhoid fever age–incidence curves were generated for high (>100/100 000 cases/year), medium (10–100/100 000 cases/year), and low (<10/100 000 cases/year) incidence settings. An age-distribution curve for high incidence
COMMON FOODS WHERE SALMONELLA COLONIZES AND WHY.
1.POULTRY
Raw and undercooked poultry such as chicken, duck and turkey has a high risk of causing food poisoning caused by salmonella. The salmonella is commonly found in the guts and features of these birds. This bacterium often contaminates fresh poultry meat during the slaughtering process and they can survive until cooking kills them. To reduce your risk, ensure poultry meat is cooked through completely, wash raw meat and ensure that raw meat does not come into contact with utensils, kitchen surfaces, chopping boards and other foods, since this can result into cross contamination.
2.VEGETABLES AND LEAFY GREENS
Vegetables and leafy greens are a common source of salmonella poisoning, especially when eaten when raw. Fruits and vegetables have caused a number of food poisoning outbreaks, particularly lettuce, spinach, cabbage, celery and tomatoes. Vegetables can be contaminated with bacteria salmonella. Contamination can occur from dirty processing equipment and unhygienic food preparation practices. Leafy greens are especially risky because they often consumed raw. To minimize risk, always wash salad leaves thoroughly before eating. Do not purchase bags of salad mix that contain spoiled mushy leaves and avoid prepared salads that have been left to sit at room temperature.
3.FISH AND SHELLFISH
Fish and shellfish are also a common source of salmonella poisoning. Fish that has not been stored at the correct temperature has a high risk of being contaminated with histamine, a toxin produced by bacteria in fish. Histamine is not by normal cooking temperatures and results in food poisoning. Another type of fish poisoning is ciguatera fish poisoning. Shellfish such as clams, mussels, oysters and scallops. Store bought shellfish is usually safe to eat. However, shellfish caught from unmonitored areas may be unsafe due to contamination from sewage, storm water drains and septic tanks. Keep fish chilled and refrigerated before cooking. Make sure fish is cooked thoroughly and cook clams and mussels till shell opens. Throw away the shells that don’t open.
4.RICE
Rice is a high risk food when it comes to food poisoning. Uncooked rice can be contaminated because salmonella can live in dry conditions as well as cooked rice. Cooked rice left standing at room temperature the salmonella bacteria can thrive and multiply in warm, moist environment. To reduce risk, serve rice as soon as it has been cooked and refrigerate leftover rice as quickly as possible after cooking. When reheating cooked rice, make sure it is steaming hot all way through.
5.DELI MEATS
Deli meats including Ham, Bacon, Salami and Hot dogs can be a source of salmonella poisoning. They can become contaminated during processing and manufacturing. Contamination can occur directly through contact with contaminated raw meat or by poor hygiene by deli staff, poor cleaning practices and cross contamination from unclean equipment such as slicer blades. Sliced lunch meats should be stored in the refrigerator until they are ready to be eaten.
6.UNPASTURIZED DAIRY
Pasteurization is the process of heating a liquid or food to kill harmful microorganisms. Food manufacturers pasteurize dairy products including milk and cheese to make them safe to consume. pasteurization kills harmful bacteria like salmonella. To reduce risk store dairy at or under 5 degrees Celsius.
7.EGGS
Eggs carry salmonella bacteria which can contaminate both the shell and the inside of an egg. To reduce risk, do not consume eggs with a cracked or dirty shell.
8.FRUITS
A number of fruit products including berries, melons and pre-prepared fruit salads have been linked to food poisoning. Fruits grown in the ground eg water melon are high risk fruits.To reduce risk wash fruits before eating .
FACTORS THAT SUPPORT ITS GROWTH AND MULTIPLICATION
Physical requirements
a. Temperature
Bacteria have a minimum, optimum, and maximum temperature for growth and for the typhoid bacteria; Mesophiles are bacteria that grow best at moderate temperatures. Their optimum growth temperature is between 25C and 45C. Most bacteria are mesophilic and include common soil bacteria and bacteria that live in and on the body. Temperatures at 65 and beyond will kill it.
b. Oxygen requirements
Bacteria show a great deal of variation in their requirements for gaseous oxygen. The typhoid bacteria is a, Facultative anaerobe that grows with or without oxygen, but generally better with oxygen. They obtain their energy through aerobic respiration if oxygen is present, but use fermentation or anaerobic respiration if it is absent. Most bacteria are facultative anaerobes.
c. pH
Typhoid Microorganisms based on their optimum ph; Neutrophiles grow best at a pH range of 5 to 8.
d. Osmosis
Osmosis is the diffusion of water across a membrane from an area of higher water concentration (lower solute concentration) to lower water concentration (higher solute concentration). Osmosis is powered by the potential energy of a concentration gradient and does not require the expenditure of metabolic energy. While water molecules are small enough to pass between the phospholipids in the cytoplasmic membrane, their transport can be enhanced by water transporting transport proteins known as aquaporins . The aquaporins form channels that span the cytoplasmic membrane and transport water in and out of the cytoplasm. To understand osmosis, one must understand what is meant by a solution . A solution consists of a solute dissolved in a solvent . In terms of osmosis, solute refers to all the molecules or ions dissolved in the water (the solvent). When a solute such as sugar dissolves in water, it forms weak hydrogen bonds with water molecules. While free, unbound water molecules are small enough to pass through membrane pores, water molecules bound to solute are not.Therefore, the higher the solute concentration, the lower the concentration of free water molecules capable of passing through the membrane. In an isotonic environment(good for the Typhoid bacteria), both the water and solute concentration are the same inside and outside the cell and water goes into and out of the cell at an equal rate.
Nutritional requirements
In addition to a proper physical environment, microorganisms also depend on an available source of chemical nutrients. Microorganisms are often grouped according to their energy source and their source of carbon.
a. Energy source
Chemotrophs use the oxidation and reduction of chemical compounds as their primary energy source.
b. Carbon source
Carbon is the structural backbone of the organic compounds that make up a living cell. Based on their source of carbon. Heterotrophs : require organic forms of carbon. A Heterotroph cannot synthesize organic molecules from inorganic nutrients, specifically a Chemolithoautotroph (typhoid bacteria) uses inorganic compounds such as hydrogen sulfide, sulfur, ammonia, nitrites, hydrogen gas, or iron as an energy source and carbon dioxide as their main carbon source.
c. Nitrogen source
Nitrogen is needed for the synthesis of such molecules as amino acids, DNA, RNA and ATP . Depending on the organism, nitrogen, nitrates, ammonia, or organic nitrogen compounds may be used as a nitrogen source.
d. Minerals
1. Sulfur
Sulfur is needed to synthesizes sulfur-containing amino acids and certain vitamins. Depending on the organism, sulfates, hydrogen sulfide, or sulfur-containing amino acids may be used as a sulfur source.
2. Phosphorus
Phosphorus is needed to synthesize phospholipids , DNA, RNA, and ATP . Phosphate ions are the primary source of phosphorus.
3. Potassium, magnesium, and calcium. These are required for certain enzymes to function as well as additional functions.
4. Iron
Iron is a part of certain enzymes.
5. Trace elements
Trace elements are elements required in very minute amounts, and like potassium, magnesium, calcium, and iron, they usually function as cofactors in enzyme reactions. They include sodium, zinc, copper,molybdenum, manganese, and cobalt ions. Cofactors usually function as electron donors or electron acceptors during enzyme reactions.
e. Water
f. Growth factors
Growth factors are organic compounds such as amino acids , purines , pyrimidines , and vitamins that a cell must have for growth but cannot synthesize itself. Organisms having complex nutritional requirements and needing many growth factors are said to be fastidious .
Summary
Bacteria have a minimum, optimum, and maximum temperature for growth and can be divided into 3 groups based on their optimum growth temperature: psychrophils, mesophils, thermophils, or hyperthermophils.
Bacteria show a great deal of variation in their requirements for gaseous oxygen. Most can be placed in one of the following groups: obligate aerobes, microaerophils, obligate anaerobes, aerotolerant anaerobes, or facultative anaerobes.
Microorganisms can be placed in one of the following groups based on their optimum pH requirements: neutrophiles, acidophiles, or alkaliphiles.
A bacterium's osmotic environment can affect bacterial growth.
Bacteria can be grouped according to their energy source as phototrophs or chemotrophs.
Bacteria can be grouped according to their carbon source as autotrophs or heterotrophs.
Combining their nutritional patterns, all organisms in nature can be placed into one of four separate groups: photoautotrophs, photoheterotrophs, chemoautotrophs, and chemoheterotrophs.
Bacteria also need a nitrogen source, various minerals, and water for growth.
Organisms having complex nutritional requirements
