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Swine Respiratory Disease SRD

The leading cause of swine mortality in the U.S.

Swine Respiratory Disease (SRD)

Swine Respiratory Disease (SRD) is the prevalent cause of nursery pig and grower/finisher deaths, according to the National Animal Health Monitoring System.1

Often, multiple infectious agents are involved. Primary pathogens include Mycoplasma hyopneumoniae, Actinobacillus pleuropneumoniae (APP) and Bordetella bronchiseptica, as well as the viral agents, such as porcine reproductive and respiratory syndrome (PRRS) virus and swine influenza virus (SIV). Common secondary invaders include Pasteurella multocida, Streptococcus suis, Haemophilus parasuis, Actinobacillus suis and Salmonella choleraesuis.  

These infectious agents act together to increase the severity and duration of the disease.

1. National Animal Health Monitoring System. 1996. Swine `95: Grower/Finisher. Part II. Reference of 1995 U.S. Grower/Finisher Health and Management Practices, p. 14–16. U.S. Department of Agriculture, Fort Collins, Colo.

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    Symptoms can vary depending on the pathogens present.

    Mycoplasmal (Enzootic) Pneumonia
    A dry, hacking, non-productive cough typically is the initial clinical sign of mycoplasmal (enzootic) pneumonia, which is caused by M. hyopneumoniae. Not all pigs in a pen will cough, but several may start to cough with others coughing in nearby pens. As pigs become sick, they eat less feed and feed consumption drops. This can be difficult to detect because not all pigs are sick at once. Variability in pigs the same age will develop as feed efficiency deteriorates and growth stall outs occur.

    Actinobacillus pleuropneumoniae (APP)
    APP is a severe and contagious respiratory disease. The clinical course is peracute, acute, subacute or chronic. Pigs die very suddenly in the peracute form. They have very high temperatures – up to 107°F – and very little, if any respiratory signs. Near the end, pigs may have severe breathing difficulties, with open-mouth breathing and a foamy, blood-tinged discharge from the nose and mouth. The skin on the nose, ears, legs and perhaps the whole body takes on a blue color from the lack of oxygen in the blood.

    Animals are generally depressed in the acute form. They refuse to eat and have severe breathing problems, coughing and sometimes open-mouth breathing. Cardiac and circulatory failure also can be present.

    In the subacute and chronic forms, there is little to no fever, and the intensity and spontaneity of the cough change considerably. Appetite tends to decrease, and many pigs that survive gain poorly.

    Bordetella bronchiseptica and Pasteurella multocida
    B. bronchiseptica and P. multocida typically act as secondary invaders in swine respiratory disease. Immune systems are compromised by a primary invader, such as M. hyopneumoniae, thereby creating an environment in the damaged lungs for these bacteria to move in and cause severe pneumonia. Clinical signs include those of the primary disease agent, but also include chronic occasional coughing, labored breathing, decreased growth rate and feed conversion.

    Porcine Reproductive and Respiratory Syndrome (PRRS)
    PRRS virus targets macrophages in the lungs, leaving the lungs highly susceptible to common viral and bacterial pathogens. The virus is spread by nasal secretions, saliva, feces, urine, semen, movement of carrier pigs, airborne transmission (up to 2 miles) and contaminated boots and clothing. Pigs infected with PRRS virus show systemic signs of disease, including fever and reduced appetite. Their respiratory rate may increase, but coughing is not typical. A decrease in thriftiness and increase in mortality is common.

    Swine Influenza Virus (SIV)
    SIV is known for its rapid onset, and pigs usually show signs within the first 12-48 hours of being infected. A noticeable sign of SIV-infected pigs is a harsh, barking cough followed by flu-like symptoms. Pigs lose their appetite, become lethargic, huddle and pile on one another. Affected pigs run high temperatures (105° to 107°F) and show labored, open-mouth, abdominal breathing (thumping).

    Streptococcus suis
    S. suis is commonly carried in the tonsil and nasal cavity of pigs and is often an opportunistic and secondary contributor to pneumonia. It is ubiquitous in swine and survives in dust and feces in their normal environment. Along with respiratory symptoms of pneumonia, it can increase morbidity and mortality and cause poor weight gain. The results of infection are influenced by the immune status of the host, environmental factors and virulence factors of the organism.

    Haemophilus parasuis
    H. parasuis
    is a common bacterial resident of the upper respiratory tract of swine and it causes a severe systemic condition (Glässer’s Disease) characterized by fibrinous
    polyserositis (inflammation of the membrane lining body cavities), arthritis and meningitis. Clinical signs in naïve herds include fever and listlessness followed by a diminished appetite and anorexia. Difficult breathing, squealing (indicating pain), swollen joints, lameness, tremors, lack of coordination, cyanosis, recumbency and sudden death may ensue.

    In conventional herds, chronic infections in nursery pigs may result in poor-performing pigs. Cough (sometimes of only two or three episodes), difficult breathing, weight loss, lameness and rough hair coat are the chief clinical signs. 

  • Work with your veterinarian to identify the agents involved with swine respiratory disease. Proper diagnosis will help determine the different pathogens present so the most effective prevention and treatment options can be implemented.

    Regularly submitting blood and tissue samples to a diagnostic laboratory will help keep you up-to-date on what’s going on in your operation.  


    STOMP PLUS® – a diagnostic program created by Zoetis – helps producers and their veterinarians study the disease dynamics in their herd. Using a combination of serology, post-mortem and PCR testing, information is gathered to help determine what diseases are occurring, the timing and severity of disease. This allows health programs to be placed for maximum impact. Contact your veterinarian or Zoetis representative if you’re interested in putting STOMP Plus to work in your operation.  

  • EXCEDE® (ceftiofur crystalline free acid) Sterile Suspension

    EXCEDE® is a complete treatment with a single dose. This treatment is the ONLY single dose injectable antibiotic that has been proven to deliver at least seven days of therapeutic plasma levels.1 It starts working right away to treat the pig and helps stop the shedding of bacteria.  

    EXCEDE provides treatment against the following bacteria associated with SRD.

    • A. pleuropneumoniae
    • P. multocida
    • H. parasuis
    • S. suis

    It also controls SRD associated with Actinobacillus pleuropneumoniae, Pasteurella multocida, Haemophilus parasuis and Streptococcus suis in groups of pigs where SRD has been diagnosed. 

    EXCEDE should not be administered to pigs known to be hypersensitive to cephalosporins or penicillins. Following label use as a single treatment, a 14-day pre-slaughter withdrawal period is required.


    DRAXXIN® (tulathromycin) Injectable Solution

    DRAXXIN works to fight all five bacterial respiratory pathogens that are key causes of SRD:

    • A. pleuropneumoniae
    • P. multocida
    • B. bronchiseptica
    • H. paraseis
    • M. hyopneumoniae 

    It’s a one-dose formula that is absorbed into the blood stream within 15 minutes and is distributed to lung tissues. DRAXXIN helps reduce shedding, which helps prevent other pigs from getting infected. It provides extended therapy and effectiveness while minimizing labor.

    DRAXXIN should not be used in animals known to be hypersensitive to the product. The pre-slaughter withdrawal time for DRAXXIN in swine is five days.


    LINCOMIX® (lincomycin) Feed Medication

    LINCOMIX is the only FDA approved feed medication for mycoplasmal pneumonia, which is caused by M. hyopneumoniae, a leading bacterial agent in SRD. LINCOMIX offers zero-day U.S. withdrawal at all feeding levels and has no weight restrictions. 

     1. Study 1121R-60-04-215

  • Help control SRD by vaccinating against M. hyopneumoniae and swine influenza virus (SIV).


    Because pigs may be infected with M. hyopneumoniae within the first three weeks of life, it may make sense to vaccinate early in a pig’s life. RespiSure-ONE has label claims that let producers vaccinate newborn pigs as early as one day of age to help reduce chronic pneumonia, severity of colonization and shedding of M. hyopneumoniae. This timing offers the convenience of vaccinating at Day 1 when pigs are being handled at processing. 

    FluSure XP®

    Swine influenza virus (SIV) continues to evolve and challenge swine herds. Zoetis has responded by updating FluSure XP® to include an H1N2 strain. The product still includes two strains of H1N1 and one H3N2, but now is the only commercial vaccine to contain H1N2.

    Researchers recently identified the subclusters Delta 1 and Delta 2 in the Delta H1 cluster.1-4 That’s why Zoetis updated FluSure XP in 2011 to include a Delta H1N2 strain and is a result of their commitment to surveying the ever-changing landscape of SIV and aggressively updating their vaccines as necessary.

    FluSure XP helps protect against the most current strains of SIV in the U.S. Updated FluSure XP, when used with FluSure® Pandemic as part of the FluSure XP Defense System™, helps protect against 9 out of 10 of the most current flu strains.5

    Control environmental factors

    Certain environmental factors can help transmit and increase the severity of the swine respiratory disease complex. Environmental factors that contribute to SRD include:

    • Overcrowding
    • Frequent mixing of pigs
    • High humidity
    • Dust
    • High ammonia levels
    • Temperature fluctuation

    Working to minimize these factors can help improve pig health.



    1. Vincent A, Ma W, Lager K, Gramer M, Richt J, Janke B. 2009. Characterization of a newly emerged genetic cluster of H1N1 and H1N2 swine influenza virus in the United States. Virus Genes. 39:176-185.
    2. Vincent A, Harland M, Lorusso A, et al. 2010. Genetic and antigenic characterization of 2008 swine influenza viruses from the United States. Proceed. 21st IPVS, p.259.
    3. Rapp-Gabrielson V, Nitzel G, Yonkers T, et al. 2010. Antigenic and genetic variations of endemic human-like (delta cluster) swine influenza H1N1 and H1N2 field isolates from the United States. Proceed. 41st AASV, p 377-78.
    4. Rapp-Gabrielson V, Evan J, Czach J, et al. 2010. Antigenic and genetic diversity of delta cluster swine influenza virus H1N1 and H1N2 field isolates from the United States. Proceed 21st IPVS, p.258.
    5. Genetic comparison of viruses characterized by the University of Minnesota Veterinary Diagnostic Laboratory in the last three years demonstrated that 9 out of 10 currently circulating U.S. strains were at least 90% similar to FluSure XP and/or FluSure Pandemic strains.

  • There are big economic factors that face producers if SRD isn’t treated properly.

    • High mortality rate
    • Sort loss
    • Increased days to market
    • Lower feed efficiency
    • Higher cull rate
    • High treatment costs

    Mortality is a key economic issue facing producers. A survey in 2006 by the National Animal Health Monitoring System (NAHMS) discovered that respiratory disease was the main producer-identified cause of swine mortality – 44.2% of nursery pigs and 61.1% of grower/finisher pigs.1 

    1. USDA. 2008. Part IV: Changes in the U.S. Pork Industry, 1990-2006. USDA-APHIS-VS, CEAH. Fort Collins, CO.



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