Pleuropneumonia

Pleuropneumonia refers to a severe form of respiratory disease characterized by inflammation of both the lung tissue (pneumonia) and the pleural membranes lining the chest cavity (pleuritis). This condition affects multiple farm animal species including cattle, goats, pigs, and sheep, with specific causative agents and disease characteristics varying by species. The concurrent involvement of the lungs and pleura creates particularly severe clinical disease, as inflammation of the pleural surfaces causes intense pain with each breath, while lung involvement compromises oxygen exchange. Pleuropneumonia conditions represent some of the most serious respiratory diseases in livestock, with certain forms designated as reportable diseases requiring notification to regulatory authorities due to their potential for devastating economic impact and international trade implications.

Contagious Bovine Pleuropneumonia (CBPP) caused by Mycoplasma mycoides subspecies mycoides is one of the most significant cattle diseases globally, though it has been eradicated from many developed countries including the United States, where it last occurred in 1892. CBPP remains prevalent in Africa and parts of Asia, causing severe economic losses and limiting livestock trade. Contagious Caprine Pleuropneumonia (CCPP) affects goats in similar regions and is caused by Mycoplasma capricolum subspecies capripneumoniae. In contrast, porcine pleuropneumonia caused by Actinobacillus pleuropneumoniae occurs worldwide and represents a major economic concern for swine producers. Less severe forms of pleuropneumonia in cattle, sheep, and goats may result from various bacterial pathogens including Mannheimia haemolytica and Pasteurella species.

The economic impact of pleuropneumonia varies significantly based on the specific disease form and the affected region. Where CBPP and CCPP occur, the diseases can devastate cattle and goat populations, with mortality rates potentially exceeding 50 percent in naive herds. These diseases severely restrict international livestock trade, as countries free of these pathogens maintain strict import controls to prevent reintroduction. Porcine pleuropneumonia causes significant economic losses in swine operations worldwide through mortality, reduced growth rates, treatment costs, and carcass condemnation at slaughter due to lung lesions. Even non-contagious forms of pleuropneumonia result in substantial animal suffering and economic losses when they occur.

Understanding the specific form of pleuropneumonia affecting a herd is essential for appropriate response, as the causative agent, regulatory status, treatment options, and prevention strategies differ significantly between disease types. The contagious mycoplasmal forms (CBPP and CCPP) are notifiable diseases in most countries, requiring immediate reporting to veterinary authorities upon suspicion. Prompt veterinary involvement is essential for diagnosis, as clinical signs alone cannot reliably distinguish between disease forms. In regions where contagious pleuropneumonia does not occur, cases of pleuropneumonia typically result from bacterial pathogens that cause severe but non-regulated respiratory disease. Working with licensed veterinarians ensures proper diagnosis, appropriate treatment where indicated, and compliance with regulatory requirements for reportable diseases.

Pleuropneumonia in farm animals results from several different bacterial pathogens depending on the species affected and the geographic region. Contagious Bovine Pleuropneumonia is caused by Mycoplasma mycoides subspecies mycoides Small Colony type, a fastidious organism lacking a cell wall that makes it resistant to many common antibiotics. Contagious Caprine Pleuropneumonia results from infection with Mycoplasma capricolum subspecies capripneumoniae, a closely related mycoplasma with similar characteristics. Porcine pleuropneumonia is caused by Actinobacillus pleuropneumoniae, a gram-negative bacterium occurring in multiple serotypes with varying virulence. Other bacteria including Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni can cause pleuropneumonia in cattle, sheep, and goats as part of or progression from respiratory disease complexes.

No genetic predisposition to pleuropneumonia has been definitively established, though individual and breed variations in disease susceptibility exist. Some evidence suggests certain cattle breeds may show somewhat different susceptibility to CBPP, though this has limited practical application given the disease's regulatory status. In swine, genetic lines may differ in susceptibility to Actinobacillus pleuropneumoniae, with some breeding programs selecting for improved respiratory disease resistance. Individual variation in immune response influences disease severity, with some animals experiencing subclinical infection while others develop fulminant fatal disease despite similar exposure. The virulence of the specific pathogen strain also significantly influences disease severity and clinical presentation.

Environmental and management factors play crucial roles in disease transmission and expression. Close contact housing significantly increases transmission risk for all forms of pleuropneumonia, as the causative organisms spread primarily through respiratory secretions during close animal-to-animal contact. Poor ventilation concentrates airborne pathogens and increases exposure intensity. Stress from transportation, commingling, temperature extremes, or concurrent infections suppresses immune function and increases susceptibility to severe disease. Dust and other respiratory irritants may damage respiratory epithelium, reducing natural defenses. In areas where CBPP and CCPP occur, movement of infected animals, including subclinical carriers, introduces infection to new herds and regions.

Risk factors for pleuropneumonia include introduction of carrier animals, inadequate biosecurity, intensive housing, and stress events that compromise immune function. For CBPP and CCPP, the primary risk factor is contact with infected animals from endemic regions. Swine operations face ongoing risk from Actinobacillus pleuropneumoniae due to widespread carrier status in pig populations. Young growing pigs are particularly susceptible to severe porcine pleuropneumonia. Cattle experiencing shipping stress or other bovine respiratory disease complex triggers are at increased risk for pleuropneumonia caused by Mannheimia and related pathogens. Animals with concurrent viral infections have compromised respiratory defenses that facilitate bacterial invasion.

The pathophysiology of pleuropneumonia involves bacterial colonization of the lower respiratory tract followed by intense inflammatory response affecting both lung tissue and pleural surfaces. Following inhalation of contaminated respiratory droplets, bacteria establish infection in the lungs, where they multiply and release toxins that trigger massive inflammatory cascades. Neutrophils flood into affected areas, releasing enzymes and inflammatory mediators that damage tissues while attempting to control infection. Fibrin accumulates on pleural surfaces, creating the characteristic fibrinous pleuritis that causes severe pain and may lead to adhesion formation. Lung tissue undergoes consolidation as normal architecture is replaced by inflammatory infiltrates and dead cells. In severe cases, lung necrosis and sequestrum formation occur, creating pockets of dead tissue walled off from surrounding lung. The combination of extensive lung damage and painful pleuritis creates the severe clinical disease characteristic of pleuropneumonia.

Early warning signs of pleuropneumonia may be subtle or may be absent entirely in peracute cases where animals die rapidly before obvious clinical signs develop. In cases with more gradual onset, initial signs include mild depression, decreased appetite, and subtle separation from herdmates that observant producers may detect. A slight increase in respiratory rate and mild reluctance to move may precede more obvious symptoms. Low-grade fever might be the only initial finding in some animals. In pigs, early signs often include decreased feed intake, reluctance to rise, and huddling behavior. These early signs can easily be missed or attributed to other causes, emphasizing the need for vigilant observation particularly during high-risk periods.

The clinical presentation of pleuropneumonia varies by species and causative agent but shares characteristic features reflecting concurrent lung and pleural involvement. Cattle with CBPP or severe bacterial pleuropneumonia show marked depression, anorexia, fever often exceeding 104°F (40°C), and obvious respiratory distress. The breathing pattern is characteristically shallow and rapid, as deep breathing causes severe pain from inflamed pleural surfaces. Cattle often stand with elbows abducted and neck extended, attempting to maximize airflow while minimizing chest wall movement. Goats with CCPP show similar signs with rapid progression to severe illness. Pigs with pleuropneumonia may show acute respiratory distress with mouth breathing, cyanosis, and bloody froth from the nose in severe cases.

Behavioral changes in animals with pleuropneumonia reflect both severe systemic illness and the characteristic chest pain associated with pleuritis. Affected animals strongly resist movement and may refuse to walk even short distances. They often stand still with a fixed, painful expression and show distress if forced to move. Feed and water intake essentially cease as the animal focuses entirely on the effort of breathing. Lying down may be avoided because the pressure on the chest increases discomfort, leading to exhaustion in animals that refuse to rest. Social interaction ceases completely, with affected animals isolating themselves and showing no interest in herdmates. These dramatic behavioral changes typically develop rapidly over 24-48 hours as disease progresses.

Physical examination findings in pleuropneumonia cases provide diagnostic clues to the involvement of pleural surfaces alongside lung tissue. Temperature elevation is typically marked, often 105-107°F (40.5-41.7°C) in acute cases. Respiratory rate is dramatically increased, often to 60 or more breaths per minute, but breaths are shallow due to chest pain. Auscultation of the lungs may reveal harsh breath sounds, areas of consolidation with absent normal sounds, and characteristic pleural friction rubs that sound like creaking leather as inflamed pleural surfaces move against each other. Percussion of the chest may identify areas of dullness corresponding to consolidated lung or pleural fluid accumulation. Pain response on chest palpation is typically marked, with animals flinching or attempting to move away when pressure is applied to the ribcage.

Symptom progression in pleuropneumonia is often alarmingly rapid, with animals deteriorating from apparently normal to severely ill or dead within 24-72 hours in acute cases. The peracute form, particularly common in porcine pleuropneumonia, may cause death within hours with minimal premonitory signs. Acute cases show progressive respiratory deterioration over 1-3 days, with increasing distress and declining response to any intervention. Subacute and chronic forms develop in some survivors of acute disease, with persistent respiratory compromise, poor condition, and reduced productivity. Animals surviving acute CBPP may develop chronic lung lesions called sequestra that serve as reservoirs for ongoing infection and potential transmission.

Emergency symptoms requiring immediate intervention include severe respiratory distress with open-mouth breathing, cyanosis (blue mucous membranes), collapse, bloody nasal discharge, and temperatures exceeding 106°F (41.1°C). Animals found dead without prior observed illness indicate peracute disease requiring immediate investigation of remaining herd members. Any suspicion of CBPP or CCPP constitutes an emergency requiring immediate veterinary and regulatory notification regardless of individual animal status. Acute porcine pleuropneumonia outbreaks with multiple affected pigs require emergency response to limit mortality and spread. In all cases of severe pleuropneumonia, immediate veterinary assessment is essential to guide treatment decisions and ensure regulatory compliance for reportable disease conditions.

Clinical examination of animals with suspected pleuropneumonia combines assessment of respiratory function with careful attention to signs indicating pleural involvement. The characteristic shallow, rapid, painful breathing pattern immediately suggests pleural disease. Thorough auscultation of all lung fields identifies areas of abnormal breath sounds, consolidation, and the pleural friction rubs pathognomonic for pleuritis. Percussion helps delineate the extent of lung involvement and detect pleural fluid accumulation. Pain response during examination, particularly on chest pressure, supports pleural involvement. Temperature measurement documents the fever typical of acute bacterial infection. The overall clinical picture of fever, severe respiratory distress, and evidence of pleural involvement creates strong suspicion of pleuropneumonia.

Diagnostic testing confirms the specific causative agent and ensures appropriate regulatory response for notifiable diseases. Serological testing for CBPP and CCPP uses complement fixation tests or ELISA methods to detect antibodies, though interpretation requires expertise given cross-reactivity concerns. Culture of respiratory samples including transtracheal wash, bronchoalveolar lavage, or lung tissue from fatal cases allows identification of bacterial pathogens. Molecular testing using polymerase chain reaction (PCR) provides rapid, specific identification of mycoplasmal pathogens. In swine, serological profiling for Actinobacillus pleuropneumoniae serotypes helps characterize herd infection status. Blood chemistry and hematology support diagnosis by demonstrating inflammatory patterns consistent with severe bacterial infection.

Differential diagnosis for livestock presenting with severe respiratory disease and pleurisy includes multiple conditions requiring careful differentiation. Other causes of bacterial pneumonia including Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni can progress to involve pleural surfaces. Viral respiratory infections rarely cause primary pleuritis but may predispose to secondary bacterial pleuropneumonia. In cattle, traumatic reticulopericarditis (hardware disease) can cause respiratory distress and chest pain that may initially resemble pleuropneumonia. Pulmonary thromboembolism in cattle causes acute respiratory distress. In pigs, classical swine fever and African swine fever include respiratory signs and must be considered in appropriate geographic contexts. Careful clinical evaluation combined with appropriate diagnostic testing distinguishes these conditions.

Herd-level diagnostics address outbreak investigation and surveillance for contagious diseases requiring regulatory response. Postmortem examination of animals that die or are euthanized provides crucial diagnostic information through characteristic gross lesions including fibrinous pleuritis, lung consolidation, and sequestrum formation in chronic CBPP cases. Necropsy findings guide sample collection for confirmatory laboratory testing. Serological surveys of exposed animals help define infection extent within affected herds and detect subclinical carriers. In regions free of CBPP and CCPP, any suspicion of these diseases triggers investigation by regulatory authorities to confirm or rule out these devastating conditions. Herd-level investigation also identifies management factors contributing to non-contagious forms of pleuropneumonia.

Emergency treatment for pleuropneumonia depends critically on the suspected causative agent and regulatory status of the disease. For non-regulated bacterial pleuropneumonia, immediate initiation of broad-spectrum antimicrobial therapy is essential, with drug selection targeting likely pathogens based on species and regional patterns. Non-steroidal anti-inflammatory drugs provide fever reduction and, importantly, analgesia for the severe chest pain characteristic of pleuritis. Supportive care including fluid therapy for dehydrated animals and stress reduction helps maintain physiological function while antimicrobials take effect. For suspected CBPP or CCPP, treatment decisions are complicated by regulatory considerations, and immediate veterinary and regulatory consultation is mandatory before any intervention.

Medical management of treatable forms of pleuropneumonia relies primarily on antimicrobial therapy targeting the causative bacteria. For Actinobacillus pleuropneumoniae in swine, various antimicrobials including penicillins, cephalosporins, florfenicol, and tilmicosin show efficacy depending on regional susceptibility patterns. Cattle and small ruminant pleuropneumonia caused by Mannheimia and Pasteurella species responds to similar antimicrobial classes used for other bacterial pneumonias. Treatment must begin early for optimal results, as extensive lung damage and fibrin deposition reduce treatment success. Duration of therapy typically requires 5-10 days to adequately address the severe tissue infection. Withdrawal times for meat and milk must be observed strictly, and all treatment must comply with drug regulations for food-producing animals.

Surgical intervention plays limited role in pleuropneumonia management but may occasionally be considered in specific circumstances. Thoracocentesis to drain pleural fluid accumulation can provide relief in cases with significant effusion, though this is an uncommon presentation. Surgical drainage of walled-off abscesses might theoretically benefit selected cases, but this is rarely practical or successful. The diffuse nature of lung involvement and the severity of systemic illness typically make surgical approaches impractical. Chronic cases with sequestra or extensive adhesions are generally not candidates for surgical repair. The primary treatment approach remains medical management for treatable forms and regulatory response for notifiable diseases.

Supportive care complements antimicrobial therapy and may influence survival in severely affected animals. Maintaining hydration through provision of easily accessible water or parenteral fluid administration supports cardiovascular function and drug distribution. Minimizing stress and handling reduces oxygen demand and prevents exacerbation of respiratory distress. Providing a comfortable, well-ventilated environment with appropriate temperature control reduces metabolic demands. Maintaining nutritional intake as much as possible supports immune function and healing, though force-feeding stressed animals is counterproductive. Isolation of affected animals prevents spread while allowing more intensive individual care and monitoring.

Herd treatment protocols address outbreak situations requiring intervention beyond individual animal treatment. In porcine pleuropneumonia outbreaks, metaphylactic treatment of exposed but not yet clinically affected pigs may reduce mortality and morbidity. Water or feed medication provides mass treatment options, though injectable antimicrobials provide more reliable blood levels in sick animals. Strategic depopulation combined with cleaning and restocking may be necessary for severe outbreaks in swine facilities. For CBPP and CCPP, treatment decisions are made at the regulatory level, with stamping-out policies often preferred over treatment due to chronic carrier development and concerns about vaccine interference.

Treatment decision factors for pleuropneumonia balance animal welfare, economic considerations, and regulatory requirements. Animals with advanced disease, particularly those showing cyanosis or collapse, have poor prognosis regardless of treatment intensity. The regulatory status of suspected contagious pleuropneumonia constrains treatment options and may mandate slaughter rather than treatment. Economic analysis of treatment costs versus animal value influences decisions for commercial livestock. Chronic cases with permanent lung damage and sequestra rarely return to acceptable production and may be better served by humane euthanasia. Consultation with veterinary professionals ensures treatment decisions comply with regulations and appropriately balance competing considerations.

Recovery timelines for pleuropneumonia vary dramatically based on the specific disease form, severity, and timing of treatment initiation. Mild cases of non-contagious bacterial pleuropneumonia treated promptly may show significant improvement within 3-5 days, though complete resolution of pleural inflammation requires weeks. Moderate cases typically require 2-4 weeks before clinical signs fully resolve, with ongoing healing continuing for months. Severe cases that survive have prolonged recovery periods, often 6-12 weeks or longer, and frequently suffer permanent lung damage. Animals with CBPP that survive acute disease may develop chronic carriers status with sequestra that persist indefinitely. Porcine pleuropneumonia survivors often have residual lung lesions detectable at slaughter.

Post-treatment care and monitoring focus on detecting relapse, supporting continued healing, and assessing residual lung damage. Treated animals require daily observation for return of fever, respiratory distress, or other signs suggesting treatment failure or disease progression. Gradual return to normal activity allows assessment of exercise tolerance and residual respiratory compromise. Nutritional support during the recovery period helps rebuild body condition lost during illness. Serial examination including auscultation and potentially imaging helps assess healing progress. Animals failing to improve despite treatment require reassessment for complications, treatment resistance, or alternative diagnoses.

Prognosis for pleuropneumonia depends heavily on the disease form, severity at diagnosis, treatment timing, and individual animal factors. Mild to moderate non-contagious pleuropneumonia treated within the first 24-48 hours of clinical signs generally carries a favorable prognosis for survival, though some permanent lung damage is common. Severe cases with extensive lung consolidation, high fever, and profound respiratory distress have guarded to poor prognosis even with aggressive treatment. Porcine pleuropneumonia has variable prognosis depending on serotype virulence and treatment timing, with peracute cases often fatal before treatment is possible. CBPP prognosis is complicated by the potential for chronic carrier development even in apparent survivors, making full recovery in the traditional sense impossible.

Return to production considerations following pleuropneumonia recovery address both animal capability and economic factors. Animals with significant residual lung damage may never achieve their genetic potential for growth, production, or reproduction. Reduced exercise tolerance limits use for working animals or breeding stock requiring mobility. Lung lesions detected at slaughter may result in carcass condemnation or trim loss, reducing economic value. Breeding animals that survived pleuropneumonia may transmit pathogens to offspring or herdmates, particularly in the case of CBPP carriers. The decision to return animals to production versus culling requires honest assessment of residual damage, disease transmission risk, and economic value. Veterinary guidance helps producers make appropriate decisions for individual animals and overall herd management.

Vaccination protocols for pleuropneumonia depend on the specific disease and regional availability of vaccines. Vaccines against Actinobacillus pleuropneumoniae are available for swine, with various products protecting against different serotypes; vaccination programs should target serotypes present in specific operations based on diagnostic testing. CBPP vaccines are used in endemic regions of Africa but are not available in disease-free countries, where prevention relies entirely on exclusion. CCPP vaccines exist for use in endemic areas. Vaccines against Mannheimia haemolytica and other respiratory pathogens help prevent the bacterial pneumonia that can progress to pleuropneumonia in cattle and small ruminants. Vaccination programs should be developed with veterinary guidance to ensure appropriate products, timing, and integration with other herd health measures.

Biosecurity measures form the foundation of pleuropneumonia prevention, particularly for the highly contagious mycoplasmal forms. For CBPP and CCPP, preventing introduction through strict controls on animal movement from endemic regions is essential. In disease-free countries, import regulations restrict entry of animals and animal products from affected regions. For porcine pleuropneumonia, all-in/all-out management, source verification, and quarantine of incoming animals reduce introduction risk. Maintaining closed herds eliminates the primary route of new pathogen introduction. When new animals must be acquired, purchasing from sources with known health status and implementing quarantine with observation before herd integration provides protection. Site security preventing contact with neighboring livestock or feral animals reduces disease introduction risk.

Nutritional prevention supports immune function capable of resisting respiratory infection. Adequate protein, energy, vitamins, and trace minerals support optimal immune response. Particular attention to vitamin A, vitamin E, selenium, copper, and zinc levels ensures these immune-critical nutrients are available. Maintaining consistent body condition without nutritional stress reduces immune suppression that predisposes to disease. Quality colostrum management in newborn animals provides passive immunity during the vulnerable early life period. Avoiding sudden feed changes and maintaining consistent feeding programs prevents metabolic stress that could compromise respiratory defenses.

Management practices reducing stress and transmission pressure provide practical disease prevention. Adequate ventilation in enclosed housing removes airborne pathogens and reduces respiratory irritation. Appropriate stocking density prevents overcrowding-related stress and pathogen concentration. Temperature regulation protecting animals from heat and cold stress maintains immune competence. Gentle handling and minimizing unnecessary procedures reduces stress-related immune suppression. Separating animals by age and source reduces pathogen transmission between groups. Dust control in housing and feeding areas reduces respiratory irritation that damages airway defenses.

Quarantine and testing protocols provide systematic approaches to disease exclusion and early detection. Quarantine of all incoming animals for at least 2-4 weeks with careful observation allows detection of developing disease before herd exposure. Testing incoming animals for specific pathogens such as Actinobacillus serotypes helps characterize disease status before introduction. Surveillance testing of existing herds identifies infection levels and guides control programs. For CBPP and CCPP, any suspicion of disease triggers regulatory testing and investigation. Postmortem examination of animals dying with respiratory disease provides diagnostic information supporting disease surveillance. Working with veterinary professionals ensures testing programs meet operation-specific needs and regulatory requirements.

Daily management and monitoring for pleuropneumonia prevention requires systematic observation of respiratory health across the herd or flock. Visual assessment of all animals at least once daily allows early detection of depression, appetite changes, or abnormal breathing. Particular attention to recently stressed animals, newly introduced stock, and young growing animals helps catch problems in their earliest stages. Establishing normal respiratory rate and effort patterns allows recognition of subtle changes preceding clinical disease. Training all personnel to recognize early respiratory disease signs ensures continuous surveillance. Recording and reporting observations creates a communication system ensuring responsible parties are aware of developing problems.

Housing and environmental management significantly impacts pleuropneumonia risk through effects on pathogen exposure and respiratory health. Ventilation systems should provide adequate air exchange to remove airborne pathogens and respiratory irritants while avoiding drafts that stress animals. Recommended ventilation rates vary by species and housing type but generally require at least four air exchanges per hour in enclosed facilities. Temperature and humidity control within comfortable ranges reduces respiratory stress and pathogen survival. Bedding management maintaining dry, clean conditions reduces ammonia generation and pathogen accumulation. Stocking density appropriate for the facility type and species prevents overcrowding-related stress and disease transmission.

Herd health programs should incorporate respiratory disease prevention as a central component alongside other health priorities. Vaccination programs targeting respiratory pathogens should be implemented based on regional disease risks and operation-specific concerns. Parasite control programs prevent concurrent infections that could compromise respiratory immunity. Processing and handling procedures should be designed to minimize cumulative stress on animals. Nutritional programs ensuring adequate vitamin and mineral status support immune function. Working with veterinarians to develop comprehensive health programs ensures integration of prevention measures across all aspects of operation management.

Record keeping and monitoring systems support effective respiratory disease prevention and facilitate outbreak response. Individual animal identification allows tracking of health events and linking disease cases to specific sources or time periods. Recording all respiratory disease cases including clinical signs, treatment, and outcomes helps identify patterns and evaluate prevention effectiveness. Mortality records including necropsy findings when available support disease surveillance. Production records help quantify the impact of respiratory disease on operation performance. Movement records documenting animal sources and destinations support disease tracing if needed.

Economic considerations influence prevention investment decisions and must balance costs against disease risk and impact. Vaccination costs represent ongoing expenses that must be justified by disease risk and potential losses. Facility improvements for ventilation and housing require capital investment but provide long-term benefits for disease control and animal welfare. Biosecurity measures may restrict management flexibility but protect against potentially devastating disease introduction. The economic impact of pleuropneumonia outbreaks can be severe, including direct mortality losses, treatment costs, reduced production, and potential regulatory consequences for notifiable diseases. Consultation with veterinary and economic advisors helps producers make informed decisions about appropriate prevention investments for their specific operations and risk situations.

All breeds of cattle, goats, and pigs are susceptible to their respective forms of pleuropneumonia, with no breed demonstrating complete resistance. For CBPP, all breeds of cattle can be infected, though some studies have suggested possible differences in clinical severity between breeds, which may relate to genetic variations in immune response or historical selection in endemic areas. Similarly, all goat breeds are susceptible to CCPP when exposed. For porcine pleuropneumonia, all commercial pig breeds can be infected with Actinobacillus pleuropneumoniae, though some genetic lines may show somewhat different susceptibility or clinical responses. These breed considerations are generally minor compared to the influence of exposure, pathogen strain, and management factors on disease occurrence and severity.

Production type influences pleuropneumonia risk primarily through management system characteristics rather than breed genetics. Intensive swine production facilities face ongoing porcine pleuropneumonia risk due to the close housing and animal flow patterns that characterize modern pork production. Finishing operations receiving pigs from multiple sources face particular challenges with disease introduction. Feedlot cattle are at increased risk for pleuropneumonia as part of the bovine respiratory disease complex due to shipping and commingling stress. In regions where CBPP and CCPP occur, traditional extensive management systems may experience rapid disease spread during outbreaks as communal grazing and watering facilitate transmission between herds. Understanding how production system characteristics influence risk helps target prevention measures appropriately.

Genetic selection for pleuropneumonia resistance remains limited by the complexity of respiratory disease susceptibility. No simple genetic markers have been identified that reliably predict resistance to pleuropneumonia in any livestock species. General selection for robustness and reduced health problems may indirectly improve respiratory disease resistance over time. In swine, some breeding companies have incorporated respiratory disease resistance indices into their selection programs, though progress is gradual given the complex genetics involved. Culling animals with recurrent respiratory problems removes susceptibility genetics from the breeding population. Maintaining genetic diversity through appropriate outcrossing supports broad immune competence. Working with geneticists and breeding advisors helps producers understand opportunities for genetic improvement within the constraints of current knowledge.

Several conditions commonly co-occur with or predispose animals to pleuropneumonia through effects on respiratory defenses. Viral respiratory infections including bovine respiratory syncytial virus, parainfluenza, and infectious bovine rhinotracheitis damage respiratory epithelium and suppress immunity, facilitating bacterial invasion that may progress to pleuropneumonia. In swine, PRRS virus and swine influenza predispose to secondary bacterial pneumonia. Mycoplasma species other than those causing CBPP and CCPP cause respiratory disease that may occur concurrently with or predispose to bacterial pleuropneumonia. Internal parasitism, particularly lungworms in ruminants, creates respiratory compromise that increases susceptibility to bacterial infection. These predisposing conditions should be addressed as part of comprehensive respiratory disease prevention.

Differential diagnosis for severe respiratory disease with pleural involvement includes multiple conditions producing similar clinical presentations. Simple bacterial pneumonia without significant pleural involvement may initially appear similar but typically lacks the extreme respiratory pain of pleuropneumonia. Traumatic reticulopericarditis in cattle causes respiratory distress and chest pain that may resemble pleuropneumonia. Pulmonary thromboembolism causes acute respiratory distress. In swine, classical and African swine fever include respiratory signs and must be considered in appropriate geographic contexts. Hemophilus parasuis infection causes polyserositis in pigs that can include pleuropneumonia. Thorough clinical examination combined with appropriate diagnostic testing, including testing for reportable diseases when indicated, differentiates these conditions.

Complications of pleuropneumonia reflect the severe tissue damage characteristic of this condition and shape long-term outcomes. Fibrous adhesions form between pleural surfaces as fibrinous exudate organizes, permanently restricting lung expansion and reducing respiratory capacity. Lung sequestra develop particularly in CBPP, creating walled-off areas of dead tissue that harbor viable organisms and serve as reservoirs for ongoing transmission. Chronic pneumonia with permanent lung scarring develops in survivors of severe acute disease, resulting in chronic poor performance. Empyema (pus accumulation in the pleural space) may develop in some cases, requiring drainage if the animal is to survive. Systemic spread of infection can cause septicemia and multi-organ involvement. These complications emphasize the importance of prevention and early aggressive treatment when appropriate to limit acute damage and long-term consequences.