HERD HEALTH PIH-30
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Enteric Colibacillosis of Newborn Pigs
Authors
Erwin M. Kohler, Ohio State University
O.A.R.D.C., Wooster, Ohio
Harley Moon, USDA, Ames, Iowa
Reviewers
Dwight Armstrong, Lewisburg, Ohio
Gerald Bernard, New Vienna, Ohio
H. Fred Troutt, Virginia Polytechnic
Institute and State University
Names such as E. coli diarrhea or scours, baby pig scours,
and colibacillosis are popularly used today to label an intesti-
nal disorder of newborn swine characterized by large amounts of
liquid feces. Research has shown that some strains of Escherichia
coli bacteria can cause such intestinal disorders, but other bac-
teria and viruses can cause diseases with similar clinical signs.
Within any herd, these different infectious agents may cause
disorders concurrently or sequentially. This summary was
prepared specifically to help the readers understand some of the
current knowledge about E. coli infections.
It is often necessary to conduct laboratory tests to estab-
lish an accurate diagnosis. Properly collected specimens from
carefully selected pigs are required for meaningful diagnostic
efforts. Even then it may be difficult to establish the diagnosis
for a particular episode of diarrhea. Too frequently, costly
chemotherapeutic agents are administered on the assumption that
the diarrhea is being caused by E. coli when, in fact, the
disease is being caused by a virus (such as TGE or rotavirus) or
another microorganism that is completely unaffected by the drugs
used.
Cause
E. coli are normal inhabitants of the intestinal tract and
are present in large numbers in the large intestine but not the
small intestine of normal animals. However, certain strains are
classed as enteropathogenic, meaning that they produce disease by
developing in the intestine without necessarily invading the
other tissues of the body. Enteropathogenic E. coli are found
throughout the world. There is probably at least one strain in
each herd. It is important to understand that the incidence of
disease caused by enteropathogenic E. coli is greatly influenced
by the management of herd and facilities. Such strains of E. coli
have the ability to propagate rapidly in the small intestine.
Additionally, these strains produce toxins (enterotoxins) which
cause massive fluid losses from the body. The amount of fluid and
electrolytes in the small intestine soon exceeds the absorptive
capacity of the intestine. Consequently, large quantities of pale
yellow, watery feces are passed. The fluids are lost at such a
rapid rate that the pig becomes dehydrated and also develops aci-
dosis because a large proportion of the electrolytes lost are
basic (alkaline). The liquid feces are usually quite alkaline.
The pigs usually are thirsty and continue to nurse until they
become too weak and depressed to do so.
This fact sheet is directed primarily to neonatal enteric
colibacillosis, which is diarrhea caused by enteropathogenic E.
coli in pigs less than 7 days old. A number of host and environ-
mental factors affect the incidence of E. coli-caused diarrhea
of newborn pigs. The stomach and intestine of pigs are quickly
flooded with bacteria immediately after birth. Many of these are
``harmless,'' but if large numbers of enteropathogenic E. coli
are present, many pigs can be infected immediately after birth.
Large numbers of E. coli are usually present in the immedi-
ate environment whenever it is dirty and wet, the ventilation is
poor, and the humidity is high. However, the most important
source of infection is other young pigs with E. coli diarrhea.
These pigs will shed up to 1 billion E. coli/cc of the liquid
feces.
Temperature is probably the most important of all the
environmental influences on the well-being of the pigs. It is
also one of the easiest to control in modern farrowing facili-
ties. Young pigs are extremely sensitive to chilling, and this
stressor lowers the resistance of pigs to infections including E.
coli.
Newborn pigs normally have no antibodies at birth but
receive them from the colostrum (first milk) of the sows. Colos-
trum has antibodies against many different microorganisms depend-
ing upon what the sow has been exposed to or vaccinated with.
Frequently, gilts have had less exposure to the enteropathogenic
E. coli in the herd and consequently don't protect their pigs as
well as sows do. If the pigs drink colostrum (containing adequate
levels of antibodies against the infecting strain) immediately
after birth, and if they continue to suckle regularly, the E.
coli will usually be inhibited sufficiently to prevent the
occurrence of clinical disease. However, all protection is rela-
tive, and infection with very large numbers of enteropathogenic
E. coli or anything that interferes with frequent suckling (such
as lactation failure, injuries, or other infections) increases
the probability of development of clinical colibacillosis.
Pigs that develop E. coli-caused diarrhea must be treated
very promptly with antibacterial drugs which have been shown to
be effective against the enteropathogenic E. coli in the herd.
The disease is so acute in young pigs that, even with proper
treatment, death and performance losses make this a very costly
disease. It is much more profitable to prevent this disease than
to be continuously treating affected pigs.
With this introduction, it should be obvious that the best
possible results in the prevention of E. coli-caused diarrhea of
baby pigs can be attained only by a complete program using all
the good management practices available.
Prevention
There are three basic approaches to the prevention of E.
coli scours. The first approach is a good sanitation program to
reduce the number of enteropathogenic E. coli. Sanitary farrowing
facilities and adequate ventilation are essential to reduce the
number of pathogenic organisms and to prevent high humidity and
damp or wet floors. Promptly covering the liquid stools with dry
bedding or soil can help reduce the spread of bacteria from pigs
with E. coli diarrhea. Modern mesh flooring reduces the exposure
of pigs to feces. In addition, if E. coli diarrhea is diagnosed,
the affected pigs should be promptly treated with antibacterial
drugs known to be effective (either by laboratory tests or
experience in that herd) against the particular strains present
in the herd. This, of course, is a treatment for the affected
pigs, but it is also an attempt to decrease the number of entero-
pathogenic E. coli that these pigs are shedding in the liquid
feces. It is important that the antibacterial drugs not be used
indiscriminately because E. coli often rapidly develop resistance
to these drugs.
The second approach is to use good management practices to
maintain the ``natural'' resistance of the newborn pig at the
highest possible level. Attention to the nutritional and general
health status of the breeding herd helps insure the delivery of
vigorous pigs and satisfactory lactation. Prompt suckling after
birth, and frequent suckling thereafter, is necessary for the
pigs to acquire the full benefits of the specific and nonspecific
protective substances in the sow's colostrum and milk. Colostral
antibodies must be swallowed every few hours to keep enough in
the intestine to protect the pigs. As previously mentioned,
chilling caused by drafts, and wet or cold floors or inadequate
heaters must be avoided because chilling is one of the most
severe stressors a young pig can encounter. Pigs should be warm
enough to sleep soundly in a stretched-out position. Pigs in wet
pens, or pens with inadequate heat, huddle, shiver, and are rest-
less, continually moving to find a warmer spot in the pile group.
The third approach to the prevention of E. coli scours of
baby pigs is to increase their resistance. The pig can get
specific protection against infectious diseases from its dam
through the colostrum and milk. This can be enhanced by vaccina-
tion of the dam. Vaccination of sows to increase the protective
value of their colostrum and milk against enteropathogenic
strains of E. coli has been attempted by many people.
One vaccination method currently being used successfully in
numerous herds by veterinarians involves feeding cultures of E.
coli to dams late in gestation. The vaccinated dams then protect
their newborn pigs via antibodies in their colostrum and milk.
The program must be custom-developed for each herd, partially
because there are so many strains of E. coli that can cause
scours of baby pigs. Antibodies produced against any one of these
strains are not very effective against most of the other strains.
There are a number of precautions to follow. Only pure E.
coli cultures isolated from the herd to be vaccinated should be
used. The aim here is to avoid bacteria or viruses that are use-
less for vaccination, or even worse, feeding bacteria or viruses
that could cause disease problems in the herd. This program has
a number of rather detailed steps. Good results depend upon a
good working relationship between a veterinarian and the pro-
ducer.
Recently, several companies have introduced vaccines con-
taining the virulence factors (pili) which enable most strains of
enterotoxigenic E. coli to heavily colonize the small intestine.
These vaccines are injected into gilts and sows late in gesta-
tion. The dams respond by producing antibodies to these pili, and
these antibodies are transferred via the colostrum and milk to
the pig's intestine. Antibody against pili prevents adhesion of
the E. coli to the wall of the intestine. If the E. coli do not
adhere, they cannot grow to large enough numbers to produce
enough toxins in the small intestine to cause diarrhea, dehydra-
tion, and death. Approximately 95% of the toxin-producing strains
that affect newborn pigs produce one of the three specific pilus
types: K88, K987P, or K99. Many strains of both enterotoxigenic
and nonenterotoxigenic E. coli also produce type 1 pili. The role
of type 1 pili (if any) in the disease has not been defined and
is currently a point of controversy among researchers.
Some of the vaccines contain heat-labile toxin antigen which
is produced by some strains of enterotoxigenic E. coli. These
antigens should stimulate the sows to produce antibodies against
heat-labile toxin and to transfer these to the intestines of the
pigs. These antibodies could neutralize a limited amount of
heat-labile toxin. Although prevention of colonization by pilus
antibodies will prevent the formation of diarrhea-producing
amounts of heat-labile toxin, there is some evidence that the
heat-labile antibodies can be of value.
Many strains produce another type of enterotoxin called
heat-stable- enterotoxin. This toxin is not antigenic (sows will
not produce antibody against it), and antibody directed against
heat-labile toxin will not protect against diarrhea caused by
strains that produce heat-stable toxin.
Although the commercial vaccines have been quite safe, there
have been a few instances in which sows have aborted following
vaccination. All E. coli organisms also contain an entirely dif-
ferent type of toxin called endotoxin, and under certain condi-
tions it appears that enough endotoxin has been present in the
vaccine to cause abortion in certain sows.
To achieve optimal benefits from any vaccination program
against E. coli scours of baby pigs, it is still essential to
keep the level of pathogenic E. coli as low as possible through
good management, to insure that pigs suckle promptly and fre-
quently, and to avoid chilling, injuries, and other disease prob-
lems.
Colibacillosis in Older Pigs
The intestinal disorders characterized by yellow to white
runny or smeary feces frequently observed in suckling pigs 10-35
days of age are often called white or milk scours. In contrast to
those of newborn pigs with colibacillosis, these stools are usu-
ally neutral or acidic. These stools also have a different
appearance from the pale yellow, watery, gassy feces of E. coli
diarrhea of baby pigs. In many cases this syndrome is also called
colibacillosis. Current research indicates that enteropathogenic
E. coli can be present and occasionally play a significant role
in the severity of the disease. However, research reports indi-
cate that a virus (rotavirus) that is probably present in all
swine herds destroys some of the epithelial cells that line the
small intestine. (Although the rotavirus can affect newborn pigs,
field investigations indicate that it rarely causes clinical
disease in pigs less than a week of age if they're nursing
healthy sows.) The resulting maldigestion and malabsorption are
similar (although less severe) to those in TGE. Coccidia can also
cause diarrhea in a similar way.
The diseases caused by these viruses are discussed in other
fact sheets. The role of enteropathogenic E. coli in these cases
is secondary to the damage caused by the virus. In some cases, E.
coli may contribute to fluid losses. In other cases, it appears
that the E. coli become closely associated with the damaged lin-
ing of the intestine and may enter the body or release toxins
(endotoxins) that are absorbed into the body and cause shock and
rather sudden death. Complete diagnostic procedures are indi-
cated, but in the absence of the demonstration of a definite role
for E. coli in the outbreak it is difficult to justify the
administration of chemotherapeutic agents. In fact, it has been
repeatedly observed they are ineffective in controlling ``white''
or ``milk'' scours.
Although enteropathogenic E. coli undoubtedly can and do
contribute to postweaning scours, the precise role and signifi-
cance is not well defined. As additional research is directed
toward postweaning scours, it may well be found that there is a
complex interaction of etiologic agents and factors among which
E. coli may act only in a secondary role here as well.
If a complete diagnosis has been made that definitely
incriminates enteropathogenic E. coli as having a significant
role in an outbreak of diarrhea in pigs over a week of age, the
incriminated strains of E. coli should be tested to determine
which antibacterial drugs are effective against them. The
selected drug should be given orally. Good sanitation and venti-
lation, avoiding overcrowding, and adequate heat as well as prop-
erly formulated feed and feeding practices are important manage-
ment practices. At present, further proof is needed before a vac-
cination program directed at preventing colibacillosis of pigs
over 10 days of age can be recommended.
Summary
Colibacillosis is a term often used loosely and consequently
used both correctly and incorrectly. Careful diagnostic study of
appropriately collected specimens from carefully selected pigs is
required to render an accurate diagnosis. In addition to the
detection of substantial numbers of enteropathogenic E. coli, the
possible role and significance of other enteric pathogens must be
evaluated in each outbreak of diarrhea.
Although many drugs are advertised for use in treating E.
coli diarrhea of newborn pigs, most of these drugs have little
effect in many herds since strains of E. coli have developed con-
siderable resistance to them. Laboratory tests with the causative
strain of E. coli or experience in the herd are necessary to make
accurate recommendations about the particular antibacterial drug
to use for treatment.
Prevention of E. coli diarrhea of newborn pigs is more
economical in the long run than treatment of large numbers of
cases. There are three basic approaches to prevention. The first
is a good sanitation program, including adequate ventilation to
maintain dry farrowing pens and to keep the number of entero-
pathogenic E. coli as low as possible. The careful design of
facilities with only a few farrowing crates per room can be very
helpful in making a sanitation program work. The second approach
is to establish a good nutritional and health program for the
breeding herd to insure the birth of vigorous pigs and a good
milk supply. The farrowing house must be operated to avoid
stressful conditions for the sows (particularly overheating) and
the pigs (particularly chilling). The third approach is to vac-
cinate the sows so that they can provide better protection for
the pigs.
A vaccination program may be indicated where there is a high
incidence of E. coli scours of newborn pigs. This may occur when
a very pathogenic strain is introduced into a herd or when there
are deficiencies in the management and farrowing facilities.
Either a commercial vaccine containing the 3 pilus antigensK88,
K99, K987P, or the oral vaccination method using enterotoxigenic
strains isolated from the herd can be used. The optimal benefits
from vaccination can be achieved only when these deficiencies in
the management and farrowing facilities are corrected. Diarrhea
in pigs over a week of age should not be assumed to be caused by
E. coli, but a careful diagnosis should be made. If E. coli are
demonstrated to be an important cause of the problem, antibac-
terial drugs that are effective against the causative strains
should be given orally.
_____________________________________________
|Related Publications |
|PIH-47 Transmissible Gastroenteritis (TGE) |
|PIH-61 Rotaviral Diarrhea in Pigs |
|___________________________________________|
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lar. Persons using such products assume responsibility for their
use in accordance with current directions and the manufacturer.
REV 6/84
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