Swine Pneumonia

Pneumonia is an important disease of

the lower respiratory tract that impairs

animal health and lowers individual and herd

performance in swine. “Pneumonia” means inflammation

of the lungs. It may be minor, subsiding quickly,

or develop into advanced pneumonia.

The cause of the lung inflammation and the development

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, appetite

and growth rate decrease, feed is utilized less efficiently,

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 inhaled

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.

Atrophic rhinitis and upper respiratory system disease

in swine are discussed in the Extension fact sheet

L-2193, “Atrophic Rhinitis.”

Bacterial Causes

Mycoplasma hyopneumoniae, the pneumonia agent

present in virtually all swine herds, is transmitted from

sow to piglets in the farrowing house and from pig to

pig in nurseries. After transmission, a variable incubation

period ensues, followed by nonfatal pneumonia

after the pigs are about 6 to 10 weeks old. M.

hyopneumoniae infection weakens the lungs’ normal

L-5203

6/98

*Associate Professor and Extension Swine Veterinarian, The Texas

A&M University System.

defenses, predisposing them to secondary infection by

Pasteurella multocida and other bacteria. The secondary

infection makes the lower respiratory disease worse

than with the M. hyopneumoniae infection alone.

The combination of infections, first with M.

hyopneumoniae, then with P. multocida, is considered

the most frequent form of pneumonia, and is called

“common swine pneumonia” or enzootic pneumonia.

The cost in the United States for enzootic pneumonia

has been estimated at $4.08 per pig, not including the

costs of drugs used to treat or reduce the effects of the

disease.

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

caused by APP type 7. All APP types are transmitted

through respiratory tract secretions over short distances,

such as nose-to-nose contact between adjacent

pens of hogs.

Sudden death is common after unobserved symptoms

or several hours of symptoms such as “thumping.”

On finding a sudden death from APP infection, a

producer usually says, “The hogs in this pen were fine

yesterday, but this one was found dead this morning!”

A bloody discharge from the nostrils is usual in hogs

dying from APP infection. Recovered hogs grow slower

than non-affected penmates and may suffer recurrent

pneumonia episodes.

Salmonella choleraesuis, a post-weaning disease,

initially causes a transient intestinal infection (usually

without diarrhea) from oral exposure to contaminated

feces, feed, water or environment. A bloodstream infection

develops next. It can affect many organs, including

liver, spleen, brain and lungs. Stressors such

as shipment, moving and mixing with other hogs, poor

sorting, overcrowding and outage of feed or water may

predispose swine to salmonella disease outbreaks.

Few swine are usually affected, but of those affected,

many die. Purple discoloration of the ears, snout, jowls

and abdomen is typical after death, indicating that the

hog died of a severe bloodstream infection as occurs

with S. choleraesuis infection.

Lungs can be coinfected with the enzootic pneumonia

microorganisms (M. hyopneumoniae and P.

multocida) and APP or S. choleraesuis or both, causing

severe disease; likewise, lungs can be coinfected with

both APP and S. choleraesuis without enzootic pneumonia

infection. Other bacteria such as streptococcal

species, Bordetella bronchioseptica, Haemophilus

parasuis, Pseudomonas aeruginosa, and Actinomyces

pyogenes can cause, contribute to or be associated

with pneumonia lesions in swine.

Viral Causes

Several viruses are important causes of swine pneumonia.

Porcine Reproductive Respiratory Syndrome

(PRRS) is the most common. It is transmitted

by contact with such body secretions as nasal mucus,

feces and urine from infected, shedding swine. Although

the PRRS virus generally does not survive for

long in the environment, it may survive in chlorinated

water for up to 7 days and be transmitted easily in

contaminated watering systems. It is also transmitted

in semen. Transmission by air over long distances is

not considered important.

The PRRS virus can cause pneumonia in any age of

swine, but younger pigs may be affected more severely.

Because the lungs’ natural defenses are suppressed

after PRRS infection, secondary pneumonia from a

wide array of bacteria or viruses is common.

Porcine Respiratory Disease Complex (PRDC)

is the term created recently in recognition that PRRS

virus-induced pneumonia predisposes the lungs to a

broad range of secondary bacterial or viral infections.

Thumping is usually seen after PRRS virus-induced

pneumonia. Affected swine may die or become chronic

poor-doers and stop growing.

Pregnant swine infected with PRRS virus often suffer

reproductive loss in the last trimester of gestation.

Farrowing live pigs that do not survive or dead pigs 4

to 5 days before the due date are typical symptoms.

Infected boars may have low fertility and intermittently

shed PRRS virus in semen.

Up to 70 percent of U.S. swine herds are thought to

contain PRRS virus-infected swine. It is also an important

disease worldwide. PRRS is discussed in more

depth in Extension fact sheet L-5137, “Porcine Reproductive

and Respiratory Syndrome.”

Swine Influenza virus causes sudden, explosive

coughing outbreaks in individual animals or herds,

particularly in fall and winter. The “flu” virus spreads

rapidly by air throughout all ages of swine. Coughing

subsides by 10 to 11 days after onset. Few swine usually

die, but deaths increase if influenza occurs as part

of the PRDC syndrome. Rectal prolapses occur commonly

in swine with severe coughing from “flu.”

Death, weight loss and treatment costs in hogs with

rectal prolapse are part of the economic loss from an

outbreak. Swine recovering from flu may take several

weeks to regain condition, which increases feed costs

and days to market.

Porcine Respiratory Coronavirus (PRCV) causes

pneumonia and is a mutant of the Transmissible Gastroenteritis

virus, which causes diarrhea and vomiting

in swine of all ages. Transmitted by air, PRCV is important

as a secondary viral infection as part of the

PRDC syndrome.

Pseudorabies virus (PRV) is a herpes virus infection

(totally unrelated to rabies virus!) that causes

central nervous system disease in young pigs, reproductive

losses from abortion and pneumonia in older

swine. Transmission is through contact with virus-containing

respiratory tract mucus and by PRV dispersed

into the air from infected animals.

Secondary bacterial complications of PRV-induced

pneumonia slow growth, worsen feed efficiency and

cause some deaths. Common in feral swine, PRV infection

is rare in domestic swine in Texas. U.S. domestic

swine are expected to be PRV-free by the year 2000

or shortly thereafter. PRV may be a complicating viral

infection in the PRDC syndrome.

Parasitic Causes

Swine internal parasite eggs, such as from roundworms,

survive for many years in soil or manure in

lots or solid floor surfaces previously contaminated by

infected hogs. Swine confined in these contaminated

environments eat microscopic roundworm eggs. Larvae

then emerge from the eggs, penetrate the intestinal

tract lining and begin migrating through tissue.

About 10 to 14 days after eggs are consumed, larvae

migrate through the lungs, producing inflammation and

coughing.

Secondary infection with P. multocida or other bacteria

can occur, especially if affected swine are exposed

simultaneously to adverse weather conditions or other

stresses.

Lungworm eggs are coughed up, swallowed and

passed in the feces of infected swine. Earthworms then

eat the eggs and larvae emerge in this intermediate host.

To be infected, a pig must eat earthworms carrying lungworm

larvae. After the earthworms are digested, larvae

migrate to the lungs,

where they mature. Migrating

larvae cause lung

hemorrhages, and

adults obstruct airways,

predisposing

the swine to infection

from influenza virus, M.

hyopneumoniae, or other bacteria.

Heavy lungworm infection causes severe coughing.

Other Causes

Extreme daily temperature fluctuations may irritate

swine respiratory tracts, resulting in secondary

bacterial infection with P. multocida. If levels are high

enough, volatile chemicals from animal waste such as

ammonia gas may predispose swine to respiratory tract

disease. Swine may inhale fine particulate dust (containing

microorganisms) and other environmental irritants

such as cell wall material (endotoxin) from

dead bacteria, causing inflammation of the upper or

lower respiratory tract.

Economic Losses

APP, S. choleraesuis and PRRS virus-induced (PRDC)

pneumonia may cause death or chronic unthriftiness

and stunting in recovered swine. Enzootic pneumonia,

swine influenza, PRCV, PRV, roundworm larval

migration, extreme daily temperature fluctuations, and

environmental dust, gas or other irritants cause few

deaths. However, they reduce appetite and growth rate,

worsen feed conversion efficiency and cause

unthriftiness, poor-doer syndrome and rectal prolapses

from chronic coughing. Treatment and control measures

costs cause further economic loss. APP may result

in carcass trim loss because of extensive adhesions

in the thoracic cavity.

Diagnosis at Slaughter

Swine veterinarians routinely inspect market hogs

at slaughter to identify for their clients the specific disease

conditions reducing production efficiency and causing

carcass trim. Although often present in more than

half of all marketed swine, pneumonia usually does not

harm pork carcass quality (except for APP pneumonia,

which causes extensive trim loss). Economic losses from

pneumonia are predominately from death, reduced

growth rate and inefficient feed conversion.

The effect of pneumonia on production efficiency

may be determined by a veterinarian who combines

the production records for growth rates, morbidity,

mortality and percent poor-doer hogs along with findings

from slaughter inspections of lungs and livers (evidence

of previous roundworm larval migration

through the liver to the lungs is liver

“milk spots”or white scars).

The veterinarian and producer

may then develop

treatment and control

strategies and monitor

progress by follow-up slaughter

inspections, coupled with production

records. A veterinarian can also inspect swine that

die on the farm after showing pneumonia symptoms.

Samples can be submitted to a diagnostic laboratory

for identification of the cause(s). Animals dead for only

a short time and not treated with any medication make

the best candidates for sampling. When the causative

bacteria or virus is identified, the veterinarian can make

specific recommendations for treatment and control.

Live-Animal Diagnosis

Thumping and coughing are typical signs of swine

pneumonia. Sickness is also demonstrated by a rectal

temperature of 104 to 106 degrees F or above in an

unexcited hog. Hogs sick from any disease, including

pneumonia, usually lie down; therefore a sick hog in a

group is the one that is lying down, while normal hogs

are up and moving alertly, inspecting their surroundings.

Subclinical or a small degree of pneumonia may not

be evident as a cough until an affected hog is walked.

Thumping when resting undisturbed is a sign of severe,

life-threatening pneumonia. Such swine may also

be mouth-breathing at rest or when coaxed to rise and

move. Mouth-breathing is usually a sign of impending

death.

Thumping and coughing do not provide enough information

to specify the cause of pneumonia. To help

diagnose parasite-induced pneumonia, have a veterinarian

examine fecal specimens under a microscope

for roundworm and lungworm eggs. Sample older, recovered

animals as well as recently coughing swine to

improve chances of finding worm eggs.

Procedures to specifically diagnose bacterial or viral-

caused swine pneumonia are usually impractical

for live, commercially raised swine. However, information

from dead swine — from laboratory analysis

of samples taken from previous slaughter inspections,

and from postmortem inspections of swine dying on

the farm — can be very helpful in pinpointing the specific

causes of pneumonia in swine on the farm and in

choosing specific antibacterial drugs.

Treatment

Swine exhibiting such pneumonia symptoms as

thumping or coughing are best treated with injectable

antibacterials. Tylan® 200 (Elanco) and Liquamycin®

LA 200® (Pfizer) are examples of over-the-counter (OTC)

antibiotics approved to treat swine pneumonia caused

by P. multocida. Tylan® 200 has a 14-day withdrawal

time and Liquamycin® LA 200® has a 28-day withdrawal

time based on their use in accordance with strict

label instructions.

Because sick swine may not eat or drink normally,

treating them with antibacterials in feed or water is

inferior to injections. Even if hogs are eating and drinking

normally, feed or water treatment is generally less

effective than injected antibacterials (Note that

Pulmotil® is a very effective feed medication for pneumonia.).

This is because approved injectable antibacterials

reach affected lung tissue more effectively than

the lower levels of antibacterials in approved feed or

water medication.

Nevertheless, producers may need to mass-medicate

groups of hogs that are coughing but still eating and

drinking adequately. In such cases, a veterinarian may

recommend chlortetracycline at the highest legal level

of 400 grams/ton feed (zero day withdrawal at this level)

until coughing subsides. Chlortetracycline (CTC 50

[Alpharma], AUREO-MYCIN® 50 [Roche]) at 400 grams/

ton feed is approved to treat bacterial pneumonia caused

by P. multocida susceptible to chlortetracycline.

For feed drugs, all extra-label use, or administration

other than what is specifically listed on the label, is

illegal. Drugs and their legal levels and indications for

use are described in the Feed Additive Compendium,

published by The Miller Publishing Company, 12400

Whitewater Drive, Suite 160, Minnetonka, Minnesota,

55343.

Swine respond better to treatment if the correct drug

is injected soon after symptoms appear. Also, for a

better chance of recovery, move treated hogs into a

sick pen to minimize the stress of being harassed by

normal penmates. A veterinarian can recommend the

appropriate antibacterial for treatment by injection,

feed or water based on previous slaughter inspections

of market swine, necropsies of and laboratory tests on

swine dying with pneumonia symptoms, or examination

of an individual or group of swine with pneumonia.

Some pneumonias may respond only to prescription

or extra-label drugs that must be dispensed by a

veterinarian to be used legally. For example, Naxcel®

or Excenel® contain the same drug, ceftiofur (Upjohn),

and are both approved as a prescription drug (not an

OTC drug) to treat swine pneumonia caused by APP,

S. choleraesuis, P. multocida, Streptococcus suis or combinations

of them.

An extra-label drug is one approved for use in another

animal species but not in swine; the veterinarian

recommends it because no approved swine drug

can reasonably be expected to treat the specific pneumonia

diagnosed. A veterinarian-client-patient relationship

(VCPR) should exist before such a drug is dispensed.

It is illegal for a producer to use any drug (even

an approved OTC swine drug) in an extra-label manner

without specific recommendations from a veterinarian

in the context of a VCPR.

A VCPR generally means that a local veterinarian

has examined the sick animal(s) in question or, because

of previous farm visits or slaughter inspections, knows

of the disease problems on the farm where sick swine

are located. The producer receiving instructions using

the prescription or extra-label drugs must agree to:

• Use them properly;

• Identify treated swine; and

• Adhere to recommended withdrawal times.

The VCPR allows for the local veterinarian to be

available for follow-up consultation if swine react adversely

to the prescribed drug or if the drug is ineffective.

If internal parasites are a possible contributor to

coughing and pneumonia, Atgard® C for feed

(Boehringer Ingelheim), Ivomec® injection or premix

(Merial), Dectomax® injection (Pfizer), levamisole

(Levasole® for water, Tramisol® for feed [Mallinckrodt]),

Safe-Guard® for feed (Hoechst-Roussel), Banmith®

premix (Pfizer) and piperazine for water (Duravet) are

effective dewormers for adult roundworms. Safe-

Guard® is effective against some migrating larval stages

of roundworms; Banmith® continuously in feed prevents

roundworm larval migration by killing larvae as

they emerge from eggs in the intestines.

Effective against lungworms are Ivomec® injection

or premix, Dectomax® injection, Safe-Guard® for feed

and levamisole in water or feed. When using

dewormers, read and follow label instructions carefully

for withdrawal times. Safe-Guard® and Atgard®

C have zero withdrawal days.

Controlling swine internal parasites is discussed in

depth in Extension fact sheet L-2423, “Internal Parasite

Control in Farrowing Operations.”

To become better trained in preventing violative drug

residues in pork, producers can participate in the ongoing

Pork Quality Assurance (PQA) program, sponsored

by the National Pork Producers Council. This

program applies particularly to injected, feed or water

antibacterials used to treat pneumonia and other conditions.

Larger pork packers may require that producers

participate in this program and be verified at PQA

level III before they buy hogs from them.

For more information about this program, call the

local county Extension agent, the Veterinary Extension

office (409-845-4353) or the pork producers council

(515-223-2600).

Prevention and Control

Feed medications may be used to prevent pneumonia.

Lincomix® 10 (lincomycin [Upjohn]) is an example

of a feed antibiotic approved for swine to reduce the

severity of Mycoplasma pneumonia caused by M.

hyopneumoniae (at the 200gram/ton feed; 6-day withdrawal

time). Pulmotil® 18 (Tilmicosin [Elanco]) is a feed

antibiotic approved for controlling swine respiratory

disease associated with APP and P. multocida (at 181 -

363 gram/ton feed; 7-day withdrawal time). Pulmotil®

18 can be used only after a licensed veterinarian has

issued a veterinary feed directive for its use.

Weigh the cost-effectiveness of any preventive feed

additive against other disease-prevention options such

as vaccines and management techniques. Veterinarians

can help producers make such decisions.

Age-segregated rearing is a term describing the

management techniques of All-In All-Out (AIAO)

animal flow plus weaning from 28 days down to 14

to 17 days old (early weaning). In AIAO animal flow,

a producer removes all swine from a room or pen,

cleans and disinfects the room and then moves a new

group of similar-age swine into that room or pen. AIAO

prevents disease-causing microorganisms from being

transmitted from a group of older swine to younger,

more susceptible animals in the same location.

Early weaning reduces the time of pigs on sows

and thus the time that sows can transmit disease-causing

organisms to pigs. Segregated early weaning

(SEW) is a management technique in which pigs may

be weaned at 14 to 17 days old. When early-weaned

pigs are injected with antibiotics or sows are vaccinated

pre-farrowing for specific disease-causing organisms

in the herd, the term medicated early weaning

(MEW) is used.

For segregated or medicated early weaning to be

effective, producers must provide early-weaned pigs

an excellent nursery environment and special diets.

When pigs are weaned at 28 days old or older but sows

are vaccinated and pigs are medicated as in MEW, the

term used is modified medicated early weaning

(MMEW).

Pigs grow much more rapidly in effective SEW,

MEW or MMEW programs plus AIAO animal flow

(age-segregated rearing) than those weaned at 28 days

into continuous flow nurseries. To take full advantage

of age-segregated rearing, maintain AIAO animal flow

as these nursery pigs pass through the grower-finisher

stage of production. In fact, later exposure of age-segregated

reared pigs to groups of disease-carrying hogs

can result in pneumonia, diarrheal disease and much

economic loss.

Many vaccines prevent bacterial and viral pneumonia

in swine. For example, to prevent pneumoniacaused

M. hyopneumoniae infection, producers in virtually

every farrowing operation should consider giving

a killed M. hyopneumoniae vaccine such as

Respisure® (Pfizer Smith Kline Beecham, Inc.) in two

doses to pigs at 1 and 3 weeks old. To prevent death

loss from App pneumonia in show pigs, administer two

doses of Pneu Pac®-ER (Schering-Plough) or

Pleuroguard-4® (Pfizer Smith Kline Beecham, Inc.) at

purchase and 4 weeks later.

In a herd using MEW where sow-to-pig transmission

of Actinobacillus pleuropnemoniae needs to be minimized,

sows may be vaccinated with either of these

App-killed vaccines before farrowing. For terminal

show pigs, use modified-live virus (MLV)PRRS vaccine

such as RespPRRS/Repro™ (NOBL ) or Prime Pac® PRRS

(Schering-Plough) once in the first week after purchase

or as early as 3 weeks of age. Do not expose PRRS

virus-negative breeding swine to show pigs vaccinated

with PRRS MLV vaccine.

Before using any vaccine, consider its cost-effectiveness.

Consult a veterinarian for specific information

on cost-effectiveness and instructions on using vaccines

to prevent pneumonia in individual pigs and in swine

herds.

Roundworm infection is best prevented by eliminating

swine exposure to environments contaminated

with worm eggs. To eliminate lungworm infection,

separate swine from earthworms.

Summary

Swine pneumonia can have many causes and may

result in mild to severe disease symptoms and economic

losses. Correctly diagnosing the specific cause(s)

of pneumonia is most important for the correct approach

to treat individual animals and to treat, control

and prevent pneumonia in swine herds. Veterinarians

can help animal owners and producers diagnose, treat

and prevent pneumonia in swine.

For more information

Selected Articles in Proceedings of the American Association

of Swine Practitioners, 1995-1998.

Straw, B. E. and Clark, L. K., “Mycoplasmal Pneumonia of

Swine,” PIH – 29, Pork Industry Handbook, Purdue University,

West Lafayette, Indiana, 1992.

Larson, J. L., Anderson, G., McKean J., et al, “Porcine

Pleuropneumoniae,” PIH – 82, Pork Industry Handbook,

Purdue University, West Lafayette, Indiana, 1994.

Cole, J. R., Nietfeld, J. C., and Schwartz, K. J., “Salmonella

choleraesuis in Pigs,” PIH – 131, Pork Industry Handbook,

Purdue University, West Lafayette, Indiana, 1993.

Sanford, E. S., Schultz, R., and Straw, B. E., “Streptococcus

Suis Disease in Pigs,” PIH – 118, Pork Industry Handbook,

Purdue University, West Lafeyette, Indiana, 1993.

Stewart, B. S., Stromberg, B. E., Lawhorn, D. B., “Internal

Parasites of Swine,” PIH – 44, Pork Industry Handbook,

Purdue University, West Lafayette, Indiana, 1993.

Dungworth, D. L., “The Respiratory System,” in Pathology of

Domestic Animals, Jubb, K.V.F., Kennedy, P. C., and Palmer,

N., (editors), 4th Edition, Volume 2, 1993.

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