SALMONELLA TYPHI / SHIGELLA / E. COLI / HEPATITIS A VIRUS
SALMONELLOSIS
Identification
A bacterial disease commonly manifested by an acute enterocolitis, with sudden onset of
headache, abdominal pain, diarrhea, nausea and sometimes vomiting. Dehydration, especially
among infants or in the elderly, may be severe. Fever is almost always present. Anorexia and
diarrhea often persist for several days. Deaths are uncommon, except in the very young, the very
old, the debilitated and the immunosuppressed.
Occurrence
Salmonellosis is classified as a foodborne disease because contaminated food, mainly of
animal origin, is the predominant mode of transmission. The incidence rate of infection is highest
in infants and young children. Epidemiologically, Salmonella gastroenteritis may occur in small
outbreaks in the general population. About 60-80% of all cases occur sporadically; however,
large outbreaks in hospital, institutions for children, restaurants and nursing homes are not
uncommon and usually arise from food contaminated at its source, or less often, during handling
by an ill person or a carrier, but person to person spread can occur.
Mode of transmission
By ingestion of the organisms in food derived from infected animals or contaminated by
feces of an infected animal or person. This includes raw and undercooked eggs and egg products,
raw milk and raw milk products, contaminated water, meat and meat products, poultry and
poultry products. In addition, turtles, iguanas and chick, and unsterilized pharmaceuticals of
animal origin are potential sources of these bacteria. Recently, several outbreaks of salmonellosis
have been traced to consumption o f raw fruits and vegetables that were contaminated during
slicing. Fecal-oral transmission from person to person is important, especially when diarrhea is
present; infants and stool incontinent adults pose a greater risk of transmission than do
asymptomatic carriers.
Epidemics are usually traced to foods such as processed meat products, inadequately cooked
poultry and poultry products; uncooked or lightly cooked foods containing eggs and egg
products, raw milk and dairy products, including dried milk; and foods contaminated with feces
by an infected food handler. Epidemics may also be traced to foods such as meat and poultry
products that have been processed or prepared with contaminated utensils or on work surfaces or
tables contaminated in previous use.
Methods of Control
 Educated food handlers and preparers about the importance of a) handwashing before,
during and after food preparation; b) refrigerating prepared foods in small containers; c)
thoroughly cooking all foodstuffs derived from animal sources, particularly poultry, pork,
egg products and meat dishes; d) avoiding recontamination within the kitchen after
cooking is completed; and e) maintaining a sanitary kitchen and protecting prepared
foods against rodent and insect contamination.
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Educate the public to avoid consuming raw or incompletely cooked eggs, as in eggs
cooked “over easy” or “sunny side up,” in eggnogs or homemade ice cream, and using
dirty of cracked eggs.
Pasteurized or irradiated egg products should be used to prepare dishes in which eggs
would otherwise be pooled before cooking or when the dish containing eggs is not
subsequently cooked.
Exclude individuals with diarrhea from food handling and from care of hospitalized
patients, the elderly and children.
Indoctrinate known carriers on the need for very careful handwashing after defecating
(and before handling food) and discourage them from handling food for others as long as
they shed organisms.
Recognize the risk of salmonella infections in pets. Chicks, duckling and turtles are
particularly dangerous pets for small children.
SHIGELLA
Identification
An acute bacterial disease involving the large and distal small intestine and characterized by
diarrhea accompanied by fever, nausea and sometimes toxemia, vomiting, cramps and tenesmus.
In typical cases, the stools contain blood and mucus (dysentery) resulting from mucosal
ulcerations and confluent colonic crypt microabscesses caused by diarrhea. Convulsions may be
an important complication in young children. Bacteremia is uncommon. Mild and asymptomatic
infections occur. Illness is usually self-limited, lasting an average of 4-7 days.
Occurrence
Worldwide; it is estimated that shigellosis causes about 600,000 deaths per year in the
world. Two thirds of the cases, and most of the deaths, are in children under 10 years of age.
Illness in infants under 6 months is unusual. Outbreaks commonly occur under conditions of
crowding and where personal hygiene is poor, such as in jails, institutions for children, day care
centers, mental hospitals and crowded refugee camps. Shigellosis is endemic in both tropical and
temperate climates; reported cases represent only a small proportion of cases, even in developed
areas.
Mode of transmission
Mainly by direct or indirect fecal oral transmission from a symptomatic patient or a short
term asymptomatic carrier. Infection may occur after the ingestion of very few (10-100)
organisms. Individuals primarily responsible for transmission are those who fail to clean hands
and under fingernails thoroughly after defecation. They may then spread infection to others
directly by physical contact or indirectly by contaminating food. Water and milk transmission
may occur as the result of direct fecal contamination; flies can transfer organisms from latrines to
uncovered food items.
Methods of Control
 An organized effort to promote careful handwashing with soap and water is the single
most important control measure to decrease transmission rates in most settings.
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ENTEROHEMORRHAGIC E. COLI (EHEC)
Identification
This category of diarrheogenic E. coli was recognized in 1982 when an outbreak of
hemorrhagic colitis occurred in the USA and was shown to be due to an unusual serotype, E. coli
O157:H7, that had not previously been incriminated as an enteric pathogen. The diarrhea may
range from mild and nonbloody to stools that are virtually all blood but contain no fecal
leukocytes. The most feared clinical manifestations of EHEC infection are the hemolytic uremic
syndrome (HUS) and thrombotic thrombocytopenic purpura (TTP). Approximately 2-7% of
subjects who manifest EHEC diarrhea progress to develop HUS. EHEC elaborate potent
cytotoxins called Shiga toxins 1 and 2. Shiga toxin 1 is identical to Shiga toxin elaborated by
Shigella dysenteriae 1; notably, HUS is also a well recognized severe complication of S.
dysenteriae 1 disease.
Occurrence
These infections are now recognized to be an important problem in North America, Europe,
South Africa, Japan, the southern cone of South America and Australia. Serious outbreaks,
including cases of hemorrhagic colitis, HUS, and some deaths, have occurred in the USA from
inadequately cooked hamburgers, unpasteurized milk, apple cider (made from apple that were
probably contaminated by cow manure) and alfalfa sprouts.
Mode of transmission
Transmission occurs mainly by ingestion of contaminated food; as with salmonella, it is most
often due to inadequately cooked beef (especially ground beef) and also raw milk and fruit or
vegetables contaminated with ruminant feces. As with Shigella, transmission also occurs directly
from person to person, in families, child care centers and custodial institutions. Waterborne
transmission has also been documented; one outbreak was associated with swimming in a
crowed lake and one was caused by drinking contaminated unchlorinated municipal water.
Methods of Control
 Heat beef adequately during cooking, especially ground beef. The 2002 Oregon Food
Sanitation Rules states to cook ground beef to an internal temperature of 155 F for at
least 15 seconds. Reliance on cooking until all pink color is gone is not as reliable as
using a meat thermometer.
 Protect, purify and chlorinate public water supplies; chlorinate swimming pools.
 Ensure adequate hygiene in childcare centers, especially frequent handwashing with soap
and water.
Outbreaks Linked to Restaurants or Public Gatherings
Likely sources include undercooked meat, cross-contaminated food, or possibly food
contaminated by an infected food handler. Any investigation should focus on implicating
specific food items and evaluating their method of preparation. Ask about recent illness among
food handlers.
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HEPATITIS A VIRUS (HAV)
Identification
Onset of illness in adults in nonendemic areas is usually abrupt with fever, malaise, anorexia,
nausea and abdominal discomfort, followed within a few days by jaundice. In general, severity
of illness increases with age, but complete recovery without sequelae or recurrences is the rule.
Generally, hepatitis A is considered a disease with a relatively low case-fatality rate.
Occurrence
In developed countries, disease transmission is frequent among household and sexual
contacts of acute cases, and also occurs sporadically in day care centers with diapered children,
among travelers to countries where the disease is endemic, among injecting drug users and
among men who have sex with men. Where environmental sanitation is poor, infection is
common and occurs at an early age. In the USA, 33% of the general population has serologic
evidence of prior HAV infection.
Mode of transmission
Person to person by the fecal-oral route. The infectious agent is found in feces, reaches peak
levels the week or two before onset of symptoms and diminishes rapidly after liver dysfunction
or symptoms appear, which is concurrent with the appearance of circulating antibodies to HAV.
Common source outbreaks have been related to contaminated water; food contaminated by
infected food handlers, including foods that are not cooked or are handled after cooking; raw or
undercooked molluscs harvested from contaminated waters; and contaminated produce such as
lettuce and strawberries. A number of outbreaks in the USA and Europe have been associated
with injecting and noninjecting drug use.
Methods of Control
 Educate the public about good sanitation and personal hygiene, with special emphasis on
careful handwashing and sanitary disposal of feces.
 Provide proper water treatment and distribution systems and sewage disposal.
 Management of day care centers should stress measures to minimize the possibility of
fecal-oral transmissions, including thorough handwashing after every diaper change and
before eating.
 Oysters, clams and other shellfish from contaminated areas should be heated to a
temperature of 185 F – 194 F for 4 minutes or steamed for 90 seconds before eating.
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