HERD HEALTH                                       PIH-118


                 Streptococcus suis Disease in Pigs

S. Ernest Sanford, Huron Park, Ontario, Canada
Roy Schultz, Avoca, Iowa
Barbara Straw, Cornell University

Martin Bergeland, University of Minnesota
William Ingalls, The Ohio State University
Patricia Tuttle, University of Kentucky

     Streptococcus suis infection is an emerging disease in swine
operations.  Diagnostic laboratories recently have reported Strep
suis as the fifth most common disease and the  leading  cause  of
meningitis, an inflammation of the brain tissue. In a recent sur-
vey of 200 swine practitioners, Strep suis was listed second as a
disease that will cause increasing problems in the next 5 years.

     Strep suis is a bacterium that lives in the tonsils of  some
pigs  and is capable of causing disease in the brain (meningitis)
and other organs (septicemia). While Strep  suis  is  most  often
associated  with  meningitis, other manifestations in pigs caused
by Strep suis include pneumonia, a  ``fading  piglet  syndrome,''
polyserositis,  arthritis,  valvular  endocarditis,  myocarditis,
pericarditis, and abortion.

     There are several types of Strep suis. Although in the past,
type  2  has  been  most commonly identified with meningitis out-
breaks, types other than 2 may also cause  meningitis.  In  fact,
type  7  is more frequently isolated than type 2 from pigs at the
Veterinary Diagnostic Laboratory at Iowa State University.

Clinical Signs

     Although pigs from birth to adult  may  be  affected,  Strep
suis  disease  outbreaks occur most frequently in recently weaned
pigs. Typically, meningitis is seen in the  post-weaning  period.
It  may  involve  1  to 5% of the herd.  Meningitis may appear as
sudden deaths or pigs with convulsions dying in the  first  three
weeks  post-weaning.  Previously  robust  pigs  may be found dead
without having shown clinical signs. Usually, however, pigs  with
Strep  suis  meningitis  go  through  a  progression  of  loss of
appetite, reddening of skin, fever, depression, loss of  balance,
lameness, paralysis, paddling, shaking, and convulsing. Blindness
and deafness may also occur.  Septicemia  and  arthritis  in  the
absence  of meningitis are less striking and may go unrecognized.
The outbreak may be brought on by stress such as mixing,  moving,
weighing,  vaccinating,  and weather changes that affect ventila-
tion and heating in buildings.

     Strep suis septicemia in newborn pigs  produces  a  ``fading
piglet  syndrome.''  These pigs are born in good health, and ini-
tially they suck avidly, but some time over the first day or  two
of  life  they  stop  nursing,  become lethargic, and cold to the
touch and die usually 12 to 24 hours after  birth.  The  ``fading
pig''  syndrome  can  be confused with starve-outs, but pure cul-
tures of Strep suis are often cultured from the heart, blood, and
joints of these pigs.

     In breeding herds, Strep suis infections  are  less  common;
however,  there  have  been cases in which the herd experienced a
drop in farrowing rate from 85%  to  about  70%  over  a  3-month
period.  Strep suis 2 could be cultured from stillborn fetuses as
well as from uteri of infected sows. In one herd, abortions at 60
to 80 days gestation were observed. The sows were obviously sick,
running temperatures of 106 to 107o F.

     Pneumonias due to Strep suis are most common  in  2-  to  4-
week-old  pigs  but  are  seen in the growing-finishing period as
well. The Strep suis organism  is  quite  often  associated  with
other  organisms such as Pasteurella multocida, Haemophilus pleu-
ropneumoniae,  or  with  Pseudorabies  virus.  In  the  finishing
period,  the  condition is commonly observed after treating pneu-
monias with tetracyclines.


     Strep suis is one more  in  a  series  of  newly  recognized
diseases  afflicting  pigs  in our modern pig production systems.
Strep  suis  disease  is  prevalent  in  the   intensive,   high-
population-density  systems.  Poor  ventilation,  buildup  of pit
gases, overcrowding, and other stress  factors  such  as  mixing,
moving,  weighing,  and vaccinating are all associated with Strep
suis outbreaks.

     Strep suis is introduced into new herds by  healthy  carrier
pigs  that harbor the organism in their tonsils or nares. Healthy
pigs can develop meningitis after months of carrying the organism
in  their  tonsils with no ill effects. The introduction of these
healthy carrier pigs (breeding gilts,  boars,  or  weaners)  into
noninfected  herds  usually  results in disease in weaners and/or
growing pigs in recipient herds. When carrier  gilts  are  intro-
duced  into  an uninfected herd, they spread Strep suis organisms
to their piglets. The piglets can carry the  organisms  into  the
nursery,  infecting other pigs. Strep suis can affect pigs of all
ages, but most cases occur between 3 and  12  weeks  of  age  and
especially  after weaned pigs are mixed together. Less than 5% of
weaners are usually affected.

     English workers have found that  breeding  stock  can  carry
Strep  suis  in  their tonsils for at least 512 days. There is no
test to detect the infective or carrier state in breeding  stock.
Medication does not eliminate the carrier state.

     While the most common method of spreading Strep suis between
herds  is  through  introduction  of carrier pigs, flies and dead
carcasses may also transport the bacteria. Strep suis  will  live
in  flies  for  at least 5 days. Flies regurgitating as they feed
may spread Strep suis throughout a hog  unit  or  between  units.
Flies  will  travel  up  to 2 miles on their own, and may hitch a
ride on or in vehicles much farther. Carcasses of dead  pigs  are
also  a good source of the infection. Proper disposal of infected
carcasses by burning, burial, or removal  from  the  premises  is

     Since at least one strain of Strep suis (Strep suis type  2)
also  causes  meningitis in humans, it is comforting to note that
the Strep suis bacterium is easily killed by commonly used  soaps
and disinfectants.


     Definitive diagnosis is made when the Strep  suis  bacterium
is  isolated  and  typed from diseased organs. Clinical signs and
postmortem findings are helpful but not specific. One of the best
ways  to  obtain  a  definitive diagnosis is to culture the brain
tissue from affected or dead pigs. An antibacterial  susceptibil-
ity  test  performed  on  organisms  isolated  from  an affected,
untreated pig will identify the most effective treatment for  use
in the herd.

Treatment and Control

     Prior to learning the antibacterial  susceptibility  of  the
strep organism, affected piglets may be treated individually with
injections of penicillin  or  ampicillin,  and  given  supportive
nursing  care.  Early  treatment prevents death and may result in
complete recovery. Generally streptococcal organisms are somewhat
resistant to the tetracyclines. If the pig is down or convulsing,
tranquilizers and fluids may  also  be  used.  The  affected  pig
should  be removed from the pen. Water and/or electrolytes may be
given orally or per rectum.  Fluids are given at the rate  of  12
ml/kg body weight (5 ml/lb). The affected pig should be kept com-
fortable, warm, and propped up on its sternum. Typically,  tetra-
cyclines are effective on only about 6% of isolates.

     Treatments aimed at the rest of the group must also be  con-
sidered.  Injection  of the whole group with penicillin, ampicil-
lin, or another antibiotic to which the strep is susceptible  may
be  of  value.  This is especially true if others are affected or
history shows the chances for that are good.

     Alteration of management practices to minimize  stress  from
overcrowding,  poor ventilation, mixing, and moving pigs is a key
factor in effecting some control.  Strategic antibiotic feed med-
ication  prior  to known periods of heightened risk is beneficial
but often results in shifting the expression of clinical cases to
a  later  period in the production cycle. If the economic effects
of the disease warrant it, depopulation and restocking with clean
stock may be the only effective means of eradication.

     Practical preventive programs, include the use of  bacterins
in herds with both the meningitis and reproductive problems. Some
failures have been observed with commercial bacterins, and may be
caused  by  other types of streptococcus.  Even autogenous bacte-
rins frequently fail to reduce disease. This may be because  most
bacterins contain killed bacteria. Solid immunity is developed by
live or avirulent organisms. Less  immunity  is  demonstrated  by
killed organisms.

     In uninfected herds, to avoid introduction of Strep suis ask
the source of new stock whether it is a problem in the herd. Have
your veterinarian talk with the veterinarian in  charge  of  that
herd.  Artificial  insemination,  embryo  transfer, or C-sections
with cross-fostering can be used to bring genetics from  infected
to noninfected herds.

Monitoring Herds

     Monitoring herds for the presence or absence of  Strep  suis
presents  a difficult problem. Serological tests frequently cross
react so are of little value.

     Collecting tonsillar cultures and checking for the  presence
of  disease-producing  strains of streptococcus may help identify
problems. However, the techniques are difficult to accomplish and
generally more suited to research purposes than for practical use
as a monitoring method. Strep suis is difficult to find in  young
pigs in the first week of life in immune herds.

     There is an extreme amount of  variation  in  the  virulence
(infectivity) of streptococcus between herds. Some may be present
but cause no problem, others may cause severe problems.

     Eradication or elimination from a herd may be  done  by  SPF
techniques and medicated early weaning. This method requires med-
ication of the sow, with the piglets removed from the sow  during
the  first week after birth. The piglets are then reared in clean
quarters apart from animals in the rest of the herd and are  pro-
vided with feed containing appropriate medication.

     Mass medication that doesn't include  offspring  segregation
at  an early age does not necessarily eliminate the organism from
a herd.

Zoonotic Strep suis (Infection in Humans)

     So far, 17 different strains of Strep suis have been identi-
fied.  As mentioned above, one of the strains of Strep suis (type
2), also affects humans,  producing  septicemia  and  meningitis.
Those  at  greatest risk are meat handlers, but housewives, farm-
ers, and veterinarians may also be exposed. Butchers  and  others
become  infected  through  cuts  and abrasions while handling and
cutting pig carcasses. Human cases have been reported  from  Den-
mark, Holland, France, United Kingdom, Canada, and Hong Kong. The
disease may manifest itself as a ``flu-like'' disease followed by
meningitis.  Sixty percent of the human recovered cases have per-
manent hearing loss.
NEW 5/89 (5M)

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