Cook, Raymond W.

English

Texas A&M University

L·2283
Texas Agricultural Extension Service
Salmonellosis
Raymond W. Cook
Extension Veterinarian
The Texas A &M University System
Salmonella, a bacteria found throughout nature, is the
cause of an intestinal disorder known as salmonellosis.
There are more than 2,000 sero-types of salmonella; but
only 8 to 12 types are important in poultry. Many years of
cooperation between government and industry have almost
eradicated some strains of salmonella that cause poultry
disease, but have not eliminated all salmonella from every
carcass that reaches the slaughter plant. The two most
important types in poultry are S. pullorum and S.
gallinarum.
The organism, widely prevalent in the environment, is
carried by dust, dirt, insects, rodents, reptiles, animals,
free-flying birds, dogs, cats, raccoons and man. However,
the amount of salmonella you normally come in contact
with is not great enough to cause illness. Human
salmonellosis caused by S. pullorum occasionally has been
produced by massive exposure following ingestion of
contaminated foods. S. gallinarum is rarely isolated from
humans and has little public health significance.
Recent media stories about salmonella in raw ~hickens
have caused consumers to want to know more about the
illness it can cause.
The infection is characterized by rapid onset of severe
signs of acute enteric infection, usually followed by
recovery without treatment. Persons with undeveloped or
weakened immune systems are most at risk of serious
Texas Agricultural Extension Service
Zerle L. Carpenter, Director
The Texas A&M University System
College Station, Texas
health effects from salmonellosis. Salmonella in the small
intestine causes stomach pain and diarrhea. Other
symptoms include nausea, vomiting, chills and fever. The
symptoms usually last from 2 to 5 days. Most human
infections are related to animal reservoirs but some
persons can be persistent carriers of some strains such as
Salmonella typhi.
Although many people associate salmonella with poultry,
improper handling can lead to salmonella poisoning from
many foods. Good food handling in the kitchen before,
during and after cooking is the key factor in the prevention
of most foodborne infections, including salmonella.
Usually, food poisoning is directly related to careless
handling of food in the kitchen. Salmonella can be found
in a number of foods including red meats, fish, raw milk,
raw vegetables and eggs.
Factors (with comments on prevention) that contribute
to outbreaks of foodborne disease are (in order of frequency
of occurrence):
1) Inadequate cooling of foods. Place food in freezer to
cool rapidly. Make sure the food remains under 40 degrees
F. in the refrigerator.
2) Lapse of a day or more between preparing and
serving. Foods which are to be stored cold should be
refrigerated within 1 V2 hours of cooking so that surviving
organisms will not have the opportunity to multiply.
3) Infected persons having touched foods which are not
subsequently heat-processed. Any person suffering from
acute salmonellosis (looseness of the stool) is likely to be
excreting large numbers of organisms. It is difficult in
these cases to completely wash the bacteria off the ends of
the fingers. Hands should always be washed with soap and
hot water before and after handling raw meat and fish and
before working with other foods.
4) Inadequate time or temperature, or both, during heat
processing of foods (canning, cooking, processing). Cook
meat to an internal temperature of 185 degrees F. Never
partially cook meat and finish cooking it later. Bacteria,
some of which produce toxins not destroyed by cooking,
can survive in partially cooked foods.
5) Insufficiently high temperature during hot storage of
foods. Place hot cooked foods in holding equipment which
is already at a temperature of at least 140 degrees F.
Always keep hot foods above 140 degrees F. and cold foods
below 40 degrees F.
6) Inadequate time or temperature, or both, during
reheating of previously cooked food. It has been generally
accepted that cooking poultry to an internal temperature
of 185 degrees F. produces optimum doneness and reduces
normal microbial contamination to a safe level for
consumption.
7) Ingesting contaminated raw foods or raw ingredients.
Food poisoning from consumption of raw food invariably
follows the use of untreated food such as raw milk, raw
steaks and uncooked or lightly cooked eggs.
8) Cross-contamination from raw foods, raw meat,
poultry, eggshells or unpasteurized egg product to cooked
foods. Do not let raw meat juices drip on other foods.
Utensils, such as cutting boards, should be washed in hot
soapy water before using them for other foods. Use acrylic
cutting boards for meat because salmonella may survive in
the crevices in a wooden board. Acrylic boards can be put
in a dishwasher.
9) Inadequate cleaning of equipment. Thoroughly wash
equipment with hot soapy water and rinse. Chlorine
bleach can be applied as directed on the label.
10) Obtaining foods from unsafe sources. Select perish-
able foods with care. Make sure frozen foods are solid and
that refrigerated foods feel cold. Many products are dated.
Make sure the date has not expired.
11) Using leftovers. Divide meat, dressing and potato
salad into smaller portions before freezing. This allows the
food to cool quickly to temperatures at which bacteria quit
growing.
The factors that most often contribute to outbreaks of
foodborne disease vary, depending on the type of establish-
ment in which foods are handled.
Annual foodborne disease surveillance data show that
foods implicated in outbreaks are frequently mishandled
in food service establishments and homes. For instance
from 1973 to 1976,67.4 percent of the outbreaks involved
foods that were mishandled in food service establishments
and 26.6 percent involved foods mishandled in homes.
Current epidemiologic evidence indicates that meat
source animals are major reservoirs of salmonella. Animals
become infected either from feed, which frequently
contains salmonella, or from their environment, which
has been contaminated by previous flocks or herds.
The infection rate increases when swine or cattle are
transferred to slaughter and held in pens. A few infected
(or superficially contaminated) animals are the source of
salmonella spread from fecal matter to many of the
carcasses.
Considerable contamination occurs early in processing,
during defeathering of fowl or dehairing of swine. Washing
reduces the level of contamination, but subsequent
handling enhances the possibility of cross-contamination,
which increases the number of contaminated carcasses.
The primary sources of almonella in retail stores, food
processing establishments and homes are poultry carca ses,
cut of meat and unwashed eggshells. Consequently,
poultry, meat and eggs have been more commonly
associated with salmonella outbreaks than have other
foods.
Foods implicated in outbreaks of salmonellosis usually
become contaminated by salmonella in one of the following
ways:
Animal and fowl carcasses are contaminated with fecal
matter during processing.
Foods that receive no further heat treatment or that are
inadequately heated are contaminated by the addition of
raw ingredients, such as checked or cracked raw eggs that
already contain salmonella or have them on their shells.
Cooked foods become contaminated by touching un-
washed or inadequately cleaned equipment that has been
used to process contaminated raw foods of animal origin,
or by persons who have previously handled such con-
taminated foods (cross-contaminated).
To a lesser extent, human carriers who practice poor
personal hygiene can contaminate foods.
It has been difficult to determine, during outbreak
investigations, whether infected food workers were carriers
and the source of contamination or whether they had
eaten the same foods as did the other persons who had
become ill or had handled the contaminated food.
To become dangerous, foods contaminated by salmonella
usually must be held long enough at suitable temperatures
for salmonella to multiply to sufficient numbers to cause
infection. In most episodes of salmonellosis, the ill have
ingested millions of salmonella. But smaller numbers of
some sero-types apparently can cause illness in susceptible
persons.
Educational programs conducted by the Texas .4gricultural Extension Service
serve people of all ages regardless of socioeconomic level, race, color, sex,
religion, handicap or national origin.
Is ued in furtherance of Cooperative Extension Work in Agriculture and
Home Economics, Acts of Congress of May 8,1914, as amended, and June
30,1914, in cooperation with the nited States Department of Agriculture.
Zerle L. Carpenter, Director, Texas Agricultural Extension Service, The
Texas A&M University System.
lOM-7-88, New VM


Salmonellosis.

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Salmonellosis.

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