L-5203

6/98

Swine Pneumonia
Bruce Lawhorn*

P
neumonia is an important disease of
the lower respiratory tract that impairs
animal health and lowers individual and herd
performance in swine. “Pneumonia” means inflamma-
tion of the lungs. It may be minor, subsiding quickly,
or develop into advanced pneumonia.
The cause of the lung inflammation and the devel-
opment of complications, such as secondary bacterial
infection, generally determine how severe pneumonia
becomes. Coughing and “thumping”(shallow, rapid
breathing) are typical symptoms of pneumonia in
swine. As the pneumonia becomes more severe, appe-
tite and growth rate decrease, feed is utilized less effi-
ciently, hogs may become chronic poor-doers, death
may occur and treatment and control costs escalate.
Possible causes of pneumonia are bacteria, viruses,
parasites, extreme daily temperature fluctuations,
chemicals (manure gas), dust and other respiratory tract
irritants from the environment. Most of these are in-
haled into the lungs. Infectious agents such as certain
bacteria may reach the lungs through the blood stream.
Parasites reach the lungs by larval migration through
blood vessels, tissues and organs.
defenses, predisposing them to secondary infection by
Atrophic rhinitis and upper respiratory system dis- Pasteurella multocida and other bacteria. The second-
ease in swine are discussed in the Extension fact sheet ary infection makes the lower respiratory disease worse
L-2193, “Atrophic Rhinitis.” than with the M. hyopneumoniae infection alone.

Bacterial Causes The combination of infections, first with M.

hyopneumoniae, then with P. multocida, is considered
Mycoplasma hyopneumoniae, the pneumonia agent the most frequent form of pneumonia, and is called
present in virtually all swine herds, is transmitted from “common swine pneumonia” or enzootic pneumonia.
sow to piglets in the farrowing house and from pig to The cost in the United States for enzootic pneumonia
pig in nurseries. After transmission, a variable incuba- has been estimated at $4.08 per pig, not including the
tion period ensues, followed by nonfatal pneumonia costs of drugs used to treat or reduce the effects of the
after the pigs are about 6 to 10 weeks old. M. disease.
hyopneumoniae infection weakens the lungs’ normal
Actinobacillus pleuropneumoniae (APP) type 1 and
5 cause a very severe form of pneumonia occurring
usually between 8 to 26 weeks old. A milder form
*Associate Professor and Extension Swine Veterinarian, The Texas caused by APP type 7. All APP types are transmitted
A&M University System.
through respiratory tract secretions over short dis- Porcine Respiratory Disease Complex (PRDC)
tances, such as nose-to-nose contact between adjacent is the term created recently in recognition that PRRS
pens of hogs. virus-induced pneumonia predisposes the lungs to a
broad range of secondary bacterial or viral infections.
Sudden death is common after unobserved symp-
Thumping is usually seen after PRRS virus-induced
toms or several hours of symptoms such as “thump-
pneumonia. Affected swine may die or become chronic
ing.” On finding a sudden death from APP infection, a
poor-doers and stop growing.
producer usually says, “The hogs in this pen were fine
yesterday, but this one was found dead this morning!” Pregnant swine infected with PRRS virus often suf-
A bloody discharge from the nostrils is usual in hogs fer reproductive loss in the last trimester of gestation.
dying from APP infection. Recovered hogs grow slower Farrowing live pigs that do not survive or dead pigs 4
than non-affected penmates and may suffer recurrent to 5 days before the due date are typical symptoms.
pneumonia episodes. Infected boars may have low fertility and intermittently
shed PRRS virus in semen.
Salmonella choleraesuis, a post-weaning disease,
initially causes a transient intestinal infection (usually Up to 70 percent of U.S. swine herds are thought to
without diarrhea) from oral exposure to contaminated contain PRRS virus-infected swine. It is also an impor-
feces, feed, water or environment. A bloodstream in- tant disease worldwide. PRRS is discussed in more
fection develops next. It can affect many organs, in- depth in Extension fact sheet L-5137, “Porcine Repro-
cluding liver, spleen, brain and lungs. Stressors such ductive and Respiratory Syndrome.”
as shipment, moving and mixing with other hogs, poor
Swine Influenza virus causes sudden, explosive
sorting, overcrowding and outage of feed or water may
coughing outbreaks in individual animals or herds,
predispose swine to salmonella disease outbreaks.
particularly in fall and winter. The “flu” virus spreads
Few swine are usually affected, but of those affected, rapidly by air throughout all ages of swine. Coughing
many die. Purple discoloration of the ears, snout, jowls subsides by 10 to 11 days after onset. Few swine usu-
and abdomen is typical after death, indicating that the ally die, but deaths increase if influenza occurs as part
hog died of a severe bloodstream infection as occurs of the PRDC syndrome. Rectal prolapses occur com-
with S. choleraesuis infection. monly in swine with severe coughing from “flu.”
Lungs can be coinfected with the enzootic pneumo- Death, weight loss and treatment costs in hogs with
nia microorganisms (M. hyopneumoniae and P. rectal prolapse are part of the economic loss from an
multocida) and APP or S. choleraesuis or both, causing outbreak. Swine recovering from flu may take several
severe disease; likewise, lungs can be coinfected with weeks to regain condition, which increases feed costs
both APP and S. choleraesuis without enzootic pneu- and days to market.
monia infection. Other bacteria such as streptococcal
Porcine Respiratory Coronavirus (PRCV) causes
species, Bordetella bronchioseptica, Haemophilus
pneumonia and is a mutant of the Transmissible Gas-
parasuis, Pseudomonas aeruginosa, and Actinomy-
troenteritis virus, which causes diarrhea and vomiting
ces pyogenes can cause, contribute to or be associated
in swine of all ages. Transmitted by air, PRCV is im-
with pneumonia lesions in swine.
portant as a secondary viral infection as part of the
PRDC syndrome.
Viral Causes
Pseudorabies virus (PRV) is a herpes virus in-
Several viruses are important causes of swine pneu- fection (totally unrelated to rabies virus!) that causes
monia. Porcine Reproductive Respiratory Syn- central nervous system disease in young pigs, repro-
drome (PRRS) is the most common. It is transmitted ductive losses from abortion and pneumonia in older
by contact with such body secretions as nasal mucus, swine. Transmission is through contact with virus-con-
feces and urine from infected, shedding swine. Al- taining respiratory tract mucus and by PRV dispersed
though the PRRS virus generally does not survive for into the air from infected animals.
long in the environment, it may survive in chlorinated
water for up to 7 days and be transmitted easily in Secondary bacterial complications of PRV-induced
contaminated watering systems. It is also transmitted pneumonia slow growth, worsen feed efficiency and
in semen. Transmission by air over long distances is cause some deaths. Common in feral swine, PRV in-
not considered important. fection is rare in domestic swine in Texas. U.S. domes-
tic swine are expected to be PRV-free by the year 2000
The PRRS virus can cause pneumonia in any age of or shortly thereafter. PRV may be a complicating viral
swine, but younger pigs may be affected more severely. infection in the PRDC syndrome.
Because the lungs’ natural defenses are suppressed
after PRRS infection, secondary pneumonia from a
wide array of bacteria or viruses is common.
Parasitic Causes from chronic coughing. Treatment and control mea-
sures costs cause further economic loss. APP may re-
Swine internal parasite eggs, such as from round- sult in carcass trim loss because of extensive adhe-
worms, survive for many years in soil or manure in sions in the thoracic cavity.
lots or solid floor surfaces previously contaminated by
infected hogs. Swine confined in these contaminated Diagnosis at Slaughter
environments eat microscopic roundworm eggs. Lar-
vae then emerge from the eggs, penetrate the intesti- Swine veterinarians routinely inspect market hogs
nal tract lining and begin migrating through tissue. at slaughter to identify for their clients the specific dis-
About 10 to 14 days after eggs are consumed, larvae ease conditions reducing production efficiency and caus-
migrate through the lungs, producing inflammation and ing carcass trim. Although often present in more than
coughing. half of all marketed swine, pneumonia usually does not
harm pork carcass quality (except for APP pneumonia,
Secondary infection with P. multocida or other bac-
which causes extensive trim loss). Economic losses from
teria can occur, especially if affected swine are exposed
pneumonia are predominately from death, reduced
simultaneously to adverse weather conditions or other
growth rate and inefficient feed conversion.
stresses.
The effect of pneumonia on production efficiency
Lungworm eggs are coughed up, swallowed and
may be determined by a veterinarian who combines
passed in the feces of infected swine. Earthworms then
the production records for growth rates, morbidity,
eat the eggs and larvae emerge in this intermediate host.
mortality and percent poor-doer hogs along with find-
To be infected, a pig must eat earthworms carrying lung-
ings from slaughter inspections of lungs and livers (evi-
worm larvae. After the earthworms are digested, larvae
dence of previous roundworm larval migration
migrate to the lungs,
through the liver to the lungs is liver
where they mature. Mi-
“milk spots”or white scars).
grating larvae cause lung
hemorrhages, and The veterinarian and pro-
adults obstruct air- ducer may then develop
ways, predisposing treatment and control
the swine to infection strategies and monitor
from influenza virus, M. progress by follow-up slaugh-
hyopneumoniae, or other bacteria. ter inspections, coupled with produc-
Heavy lungworm infection causes severe cough- tion records. A veterinarian can also inspect swine that
ing. die on the farm after showing pneumonia symptoms.
Samples can be submitted to a diagnostic laboratory
Other Causes for identification of the cause(s). Animals dead for only
a short time and not treated with any medication make
Extreme daily temperature fluctuations may ir- the best candidates for sampling. When the causative
ritate swine respiratory tracts, resulting in secondary bacteria or virus is identified, the veterinarian can make
bacterial infection with P. multocida. If levels are high specific recommendations for treatment and control.
enough, volatile chemicals from animal waste such as
ammonia gas may predispose swine to respiratory tract Live-Animal Diagnosis
disease. Swine may inhale fine particulate dust (con-
taining microorganisms) and other environmental ir- Thumping and coughing are typical signs of swine
ritants such as cell wall material (endotoxin) from pneumonia. Sickness is also demonstrated by a rectal
dead bacteria, causing inflammation of the upper or temperature of 104 to 106 degrees F or above in an
lower respiratory tract. unexcited hog. Hogs sick from any disease, including
pneumonia, usually lie down; therefore a sick hog in a
Economic Losses group is the one that is lying down, while normal hogs
are up and moving alertly, inspecting their surround-
APP, S. choleraesuis and PRRS virus-induced (PRDC) ings.
pneumonia may cause death or chronic unthriftiness
and stunting in recovered swine. Enzootic pneumo- Subclinical or a small degree of pneumonia may not
nia, swine influenza, PRCV, PRV, roundworm larval be evident as a cough until an affected hog is walked.
migration, extreme daily temperature fluctuations, and Thumping when resting undisturbed is a sign of se-
environmental dust, gas or other irritants cause few vere, life-threatening pneumonia. Such swine may also
deaths. However, they reduce appetite and growth rate, be mouth-breathing at rest or when coaxed to rise and
worsen feed conversion efficiency and cause move. Mouth-breathing is usually a sign of impending
unthriftiness, poor-doer syndrome and rectal prolapses death.
 Thumping and coughing do not provide enough in- better chance of recovery, move treated hogs into a
formation to specify the cause of pneumonia. To help sick pen to minimize the stress of being harassed by
diagnose parasite-induced pneumonia, have a veteri- normal penmates. A veterinarian can recommend the
narian examine fecal specimens under a microscope appropriate antibacterial for treatment by injection,
for roundworm and lungworm eggs. Sample older, re- feed or water based on previous slaughter inspections
covered animals as well as recently coughing swine to of market swine, necropsies of and laboratory tests on
improve chances of finding worm eggs. swine dying with pneumonia symptoms, or examina-
tion of an individual or group of swine with pneumo-
Procedures to specifically diagnose bacterial or vi-
nia.
ral-caused swine pneumonia are usually impractical
for live, commercially raised swine. However, infor- Some pneumonias may respond only to prescrip-
mation from dead swine — from laboratory analysis tion or extra-label drugs that must be dispensed by a
of samples taken from previous slaughter inspections, veterinarian to be used legally. For example, Naxcel®
and from postmortem inspections of swine dying on or Excenel® contain the same drug, ceftiofur (Upjohn),
the farm — can be very helpful in pinpointing the spe- and are both approved as a prescription drug (not an
cific causes of pneumonia in swine on the farm and in OTC drug) to treat swine pneumonia caused by APP,
choosing specific antibacterial drugs. S. choleraesuis, P. multocida, Streptococcus suis or com-
binations of them.
Treatment An extra-label drug is one approved for use in an-
Swine exhibiting such pneumonia symptoms as other animal species but not in swine; the veterinar-
thumping or coughing are best treated with injectable ian recommends it because no approved swine drug
antibacterials. Tylan® 200 (Elanco) and Liquamycin® can reasonably be expected to treat the specific pneu-
LA 200® (Pfizer) are examples of over-the-counter (OTC) monia diagnosed. A veterinarian-client-patient relation-
antibiotics approved to treat swine pneumonia caused ship (VCPR) should exist before such a drug is dis-
by P. multocida. Tylan® 200 has a 14-day withdrawal pensed. It is illegal for a producer to use any drug (even
time and Liquamycin® LA 200® has a 28-day with- an approved OTC swine drug) in an extra-label man-
drawal time based on their use in accordance with strict ner without specific recommendations from a veteri-
label instructions. narian in the context of a VCPR.

Because sick swine may not eat or drink normally, A VCPR generally means that a local veterinarian
treating them with antibacterials in feed or water is has examined the sick animal(s) in question or, because
inferior to injections. Even if hogs are eating and drink- of previous farm visits or slaughter inspections, knows
ing normally, feed or water treatment is generally less of the disease problems on the farm where sick swine
effective than injected antibacterials (Note that are located. The producer receiving instructions using
Pulmotil® is a very effective feed medication for pneu- the prescription or extra-label drugs must agree to:
monia.). This is because approved injectable antibac- • Use them properly;
terials reach affected lung tissue more effectively than
the lower levels of antibacterials in approved feed or • Identify treated swine; and
water medication. • Adhere to recommended withdrawal times.
Nevertheless, producers may need to mass-medicate The VCPR allows for the local veterinarian to be
groups of hogs that are coughing but still eating and available for follow-up consultation if swine react ad-
drinking adequately. In such cases, a veterinarian may versely to the prescribed drug or if the drug is ineffec-
recommend chlortetracycline at the highest legal level tive.
of 400 grams/ton feed (zero day withdrawal at this level)
until coughing subsides. Chlortetracycline (CTC 50 If internal parasites are a possible contributor to
[Alpharma], AUREO-MYCIN® 50 [Roche]) at 400 grams/ coughing and pneumonia, Atgard® C for feed
ton feed is approved to treat bacterial pneumonia caused (Boehringer Ingelheim), Ivomec® injection or premix
by P. multocida susceptible to chlortetracycline. (Merial), Dectomax® injection (Pfizer), levamisole
(Levasole® for water, Tramisol® for feed [Mallinckrodt]),
For feed drugs, all extra-label use, or administration Safe-Guard® for feed (Hoechst-Roussel), Banmith®
other than what is specifically listed on the label, is premix (Pfizer) and piperazine for water (Duravet) are
illegal. Drugs and their legal levels and indications for effective dewormers for adult roundworms. Safe-
use are described in the Feed Additive Compendium, Guard® is effective against some migrating larval stages
published by The Miller Publishing Company, 12400 of roundworms; Banmith® continuously in feed pre-
Whitewater Drive, Suite 160, Minnetonka, Minnesota, vents roundworm larval migration by killing larvae as
55343. they emerge from eggs in the intestines.
Swine respond better to treatment if the correct drug Effective against lungworms are Ivomec® injection
is injected soon after symptoms appear. Also, for a or premix, Dectomax® injection, Safe-Guard® for feed
and levamisole in water or feed. When using isms in the herd, the term medicated early weaning
dewormers, read and follow label instructions care- (MEW) is used.
fully for withdrawal times. Safe-Guard® and Atgard®
For segregated or medicated early weaning to be
C have zero withdrawal days.
effective, producers must provide early-weaned pigs
Controlling swine internal parasites is discussed in an excellent nursery environment and special diets.
depth in Extension fact sheet L-2423, “Internal Para- When pigs are weaned at 28 days old or older but sows
site Control in Farrowing Operations.” are vaccinated and pigs are medicated as in MEW, the
term used is modified medicated early weaning
To become better trained in preventing violative drug
(MMEW).
residues in pork, producers can participate in the on-
going Pork Quality Assurance (PQA) program, spon- Pigs grow much more rapidly in effective SEW,
sored by the National Pork Producers Council. This MEW or MMEW programs plus AIAO animal flow
program applies particularly to injected, feed or water (age-segregated rearing) than those weaned at 28 days
antibacterials used to treat pneumonia and other con- into continuous flow nurseries. To take full advantage
ditions. Larger pork packers may require that produc- of age-segregated rearing, maintain AIAO animal flow
ers participate in this program and be verified at PQA as these nursery pigs pass through the grower-finisher
level III before they buy hogs from them. stage of production. In fact, later exposure of age-seg-
regated reared pigs to groups of disease-carrying hogs
For more information about this program, call the
can result in pneumonia, diarrheal disease and much
local county Extension agent, the Veterinary Extension
economic loss.
office (409-845-4353) or the pork producers council
(515-223-2600). Many vaccines prevent bacterial and viral pneu-
monia in swine. For example, to prevent pneumonia-
Prevention and Control caused M. hyopneumoniae infection, producers in vir-
tually every farrowing operation should consider giv-
Feed medications may be used to prevent pneumo- ing a killed M. hyopneumoniae vaccine such as
nia. Lincomix® 10 (lincomycin [Upjohn]) is an example Respisure® (Pfizer Smith Kline Beecham, Inc.) in two
of a feed antibiotic approved for swine to reduce the doses to pigs at 1 and 3 weeks old. To prevent death
severity of Mycoplasma pneumonia caused by M. loss from App pneumonia in show pigs, administer two
hyopneumoniae (at the 200gram/ton feed; 6-day with- doses of Pneu Pac®-ER (Schering-Plough) or
drawal time). Pulmotil® 18 (Tilmicosin [Elanco]) is a feed Pleuroguard-4® (Pfizer Smith Kline Beecham, Inc.) at
antibiotic approved for controlling swine respiratory purchase and 4 weeks later.
disease associated with APP and P. multocida (at 181 -
363 gram/ton feed; 7-day withdrawal time). Pulmotil® In a herd using MEW where sow-to-pig transmis-
18 can be used only after a licensed veterinarian has sion of Actinobacillus pleuropnemoniae needs to be mini-
issued a veterinary feed directive for its use. mized, sows may be vaccinated with either of these
App-killed vaccines before farrowing. For terminal
Weigh the cost-effectiveness of any preventive feed show pigs, use modified-live virus (MLV)PRRS vaccine
additive against other disease-prevention options such such as RespPRRS/Repro™ (NOBL ) or Prime Pac® PRRS
as vaccines and management techniques. Veterinarians (Schering-Plough) once in the first week after purchase
can help producers make such decisions. or as early as 3 weeks of age. Do not expose PRRS
Age-segregated rearing is a term describing the virus-negative breeding swine to show pigs vaccinated
management techniques of All-In All-Out (AIAO) with PRRS MLV vaccine.
animal flow plus weaning from 28 days down to 14 Before using any vaccine, consider its cost-effective-
to 17 days old (early weaning). In AIAO animal flow, ness. Consult a veterinarian for specific information
a producer removes all swine from a room or pen, on cost-effectiveness and instructions on using vaccines
cleans and disinfects the room and then moves a new to prevent pneumonia in individual pigs and in swine
group of similar-age swine into that room or pen. AIAO herds.
prevents disease-causing microorganisms from being
transmitted from a group of older swine to younger, Roundworm infection is best prevented by elimi-
more susceptible animals in the same location. nating swine exposure to environments contaminated
with worm eggs. To eliminate lungworm infection,
Early weaning reduces the time of pigs on sows separate swine from earthworms.
and thus the time that sows can transmit disease-caus-
ing organisms to pigs. Segregated early weaning Summary
(SEW) is a management technique in which pigs may
be weaned at 14 to 17 days old. When early-weaned Swine pneumonia can have many causes and may
pigs are injected with antibiotics or sows are vacci- result in mild to severe disease symptoms and eco-
nated pre-farrowing for specific disease-causing organ- nomic losses. Correctly diagnosing the specific cause(s)
 of pneumonia is most important for the correct ap- Purdue University, West Lafayette, Indiana, 1994.
proach to treat individual animals and to treat, control Cole, J. R., Nietfeld, J. C., and Schwartz, K. J., “Salmonella
and prevent pneumonia in swine herds. Veterinarians choleraesuis in Pigs,” PIH - 131, Pork Industry Handbook,
can help animal owners and producers diagnose, treat Purdue University, West Lafayette, Indiana, 1993.
and prevent pneumonia in swine.
Sanford, E. S., Schultz, R., and Straw, B. E., “Streptococcus
Suis Disease in Pigs,” PIH - 118, Pork Industry Handbook,
For more information Purdue University, West Lafeyette, Indiana, 1993.
Selected Articles in Proceedings of the American Association Stewart, B. S., Stromberg, B. E., Lawhorn, D. B., “Internal
of Swine Practitioners, 1995-1998. Parasites of Swine,” PIH - 44, Pork Industry Handbook,
Purdue University, West Lafayette, Indiana, 1993.
Straw, B. E. and Clark, L. K., “Mycoplasmal Pneumonia of
Swine,” PIH - 29, Pork Industry Handbook, Purdue Uni- Dungworth, D. L., “The Respiratory System,” in Pathology of
versity, West Lafayette, Indiana, 1992. Domestic Animals, Jubb, K.V.F., Kennedy, P. C., and Palmer,
N., (editors), 4th Edition, Volume 2, 1993.
Larson, J. L., Anderson, G., McKean J., et al, “Porcine
Pleuropneumoniae,” PIH - 82, Pork Industry Handbook,

Produced by AgriLife Communications & Marketing, The Texas A&M System

Extension publications can be found on the Web at: http://AgriLifebookstore.org

Educational programs of the Texas AgriLife Extension Service are open to all citizens without regard to race, color, sex, disability, religion, age or national origin.
Issued 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 United States Department of Agriculture. Texas AgriLife Extension Service, The Texas A&M System.
3,000, New VM, AS 7