Mycoplasma capricolum subspecies capripneumoniae primarily infects the respiratory tract, with a strong affinity for pulmonary and pleural tissues, which contributes to the severity and localization of disease manifestations (27, 28). CCPP is highly contagious, spreading predominantly via aerosolized respiratory droplets during close contact between infected and susceptible goats and sheep (3). Contributing risk factors include overcrowding, stress (e.g., transport, sudden climate shifts), and poor ventilation (10). The disease is most common in arid and semi-arid regions, where nomadic practices and mixed herding of sheep and goats increase exposure (2). While Mccp does not survive long in dry environments, its persistence is prolonged under moist or cold conditions, and it can remain viable in frozen pleural exudate for years (3). Importantly, subclinical carriers play a key role in disease transmission, especially when they are moved into naïve herds or exposed to stressors (29).

The clinical manifestation of CCPP can range from peracute to chronic forms. In peracute cases, sudden death may occur with minimal clinical signs (13). Acute presentations include high fever (41–43 °C), severe dyspnea, polypnea, nasal discharge, productive coughing, and pronounced postural adaptations such as extended neck and abducted forelimbs to ease breathing (3). In another study, the author reported that admission complains included weight loss, anorexia and respiratory signs that included nasal discharges polypnea, dyspnea, cough, metabolic acidosis, and open-mouth breathing in goats (30). In another recent report in sheep, authors found that clinical signs included fever, weight loss, polypnea, tachycardia, dyspnea, cough, nasal discharge, bluish mucous membranes, and open-mouth breathing (31) (Figure 1). Mortality in acute outbreaks may reach up to 60%−80%, with morbidity approaching 100% (1). Chronic cases often involve weight loss, intermittent coughing, and respiratory distress due to fibrous pleural adhesions and residual lung damage (2). Occasionally, diseased goats and sheep may die suddenly from complications such as pleural rupture or secondary infections (7). Pathologically, CCPP is characterized by unilateral fibrinous pleuropneumonia with massive pleural exudation, pulmonary consolidation, and adhesions between lung lobes and the parietal pleura (32). These changes create ideal conditions for sonographic detection (13).

Clinical assessment of CCPP relies on observing hallmark symptoms—high fever, respiratory distress, productive cough, and pleural pain evident through abdominal breathing and open-mouth posture (2, 13, 31). However, clinical diagnosis alone has limited specificity and sensitivity, as these signs overlap with other caprine respiratory diseases (3). Moreover, subclinical carriers present without obvious symptoms but remain infectious, further reducing diagnostic reliability (33). Isolation of Mccp from pleural effusion or lung tissues is considered the gold standard (34). Nevertheless, it is technically demanding, time-consuming, and requires specialized media and extended incubation periods—factors that limit its routine utility in most laboratories (2). Serologically, Mccp can be detected by complement fixation test (CFT), latex agglutination test (LAT), and competitive ELISA (cELISA) (35, 36). The LAT is reported to be more sensitive than the CFT and easier to perform than the cELISA (37). Molecular diagnostics include PCR-based assays that provide high specificity and sensitivity, especially in acute cases where bacterial load in pleural effusion is substantial (5). Multiplex and quantitative PCR approaches enhance pathogen differentiation and enable epidemiological tracking in small ruminants as previously reported (38).

Postmortem examination of goats with CCPP reveals a range of gross lesions. The postmortem findings included pulmonary consolidation, pulmonary hepatization with a marbling appearance, turbid or serosanguineous pleural effusion containing fibrin, pleural abscessation, fibrinous pleuritis, and pleural adhesions, the pericardium may be thickened, opaque, and involved with hydropericardium and adhesions (2, 13, 32, 37, 39). In peracute cases, pulmonary edema may be the only finding, whereas chronic disease features progressive pleural adhesions and extensive lung hepatization (32). Similar but less severe lesions have been reported in sheep (5).

Thoracic ultrasound excels at identifying hallmark lesions of CCPP—pleural effusion, pulmonary consolidation, and fibrinous exudates in large animals (18, 40). In small ruminants, ~24% of diseased goats show non-ventilated lung parenchyma with a liver-like echotexture on ultrasound (13). Depending on the extent of atelectasis, the underlying ventilated lung may be visible as faint, blurry, and well-defined reverberation artifacts (7). Post-mortem examinations confirm that the large hypoechoic areas in the cranioventral lung fields and the cranioventral regions of the main lobes correspond to consolidated lung tissue (41) (Figure 2).

The vast majority of affected goats exhibit unilateral hypoechoic pleural effusions, often accompanied by echogenic fibrin strands or “tags,” and a “liver-like” appearance of consolidated lung parenchyma (7). Pleural adhesions appear as thickened septa separating fluid pockets. In vivo and post-mortem correlations confirm echogenic tags as fibrin deposits—critical markers of disease staging and severity (13). Always the postmortem investigation correlates well with antemortem sonographic findings (Figure 3). In sheep with CCPP, pulmonary ultrasound shows consolidated lung parenchyma with a liver-like texture. In addition, pleural effusion, the most prominent sonographic finding, exhibits echogenicity ranging from anechoic to hyperechoic, with fibrin networks and precipitates of varying severity. Necropsy findings correlate also well with the picture of sonography carried out antemortem (41) (Figure 4). Moreover, TUS enables longitudinal monitoring of CCPP and can improve treatment outcome (7). The presentation of dyspnea greatly improves following the procedure of ultrasound-guided aspiration of pleural effusion (41) (Figure 5). A comparative summary of the reviewed studies (Table 1) delineates the characteristic ultrasonographic findings for CCPP, their pathological confirmation, and the associated strengths and limitations of this diagnostic approach.

While TUS offers a valuable, non-invasive tool for rapid, pen-side diagnosis of contagious caprine pleuropneumonia (CCPP), it should be regarded as one component of a comprehensive diagnostic and control strategy. Confirmatory diagnosis ideally requires integration of clinical assessment, ultrasonographic findings, and laboratory techniques described earlier. Nevertheless, TUS represents a practical on-farm tool for rapid case identification, particularly in remote settings where laboratory confirmation may be delayed or unavailable (30).

Evidence from dairy and beef production systems demonstrates that early detection of subclinical lung lesions is associated with improved clinical and production outcomes, underscoring the broader value of early respiratory disease diagnosis across livestock species (42–44). Calves presenting with lung consolidation at arrival are at increased risk of developing chronic pneumonia and exhibit reduced average daily gain, as well as lower carcass weight and quality (43). Early identification at purchase enables timely therapeutic intervention, potentially improving treatment success, and supports targeted management strategies, including specialized recovery diets, enhanced supportive care, and segregation of affected animals to limit disease transmission. Detection of pneumonia at purchase may also inform economic decisions, such as adjustment of purchase prices (45). In feedlot calves, TUS facilitates field-based assessments and supports informed decisions regarding antimicrobial therapy and herd management (46). Similarly, pulmonary ultrasonography has been reported as a convenient diagnostic technique for ovine respiratory complex in fattening lambs (17).

Control of CCPP in endemic areas requires a multipronged approach combining early detection, prompt isolation of affected goats and sheep, and appropriate antibiotic therapy to reduce bacterial shedding and disease progression (11). During severe outbreaks, strategic culling or slaughter of chronically infected goats and sheep may be required to control the spread of the disease. Vaccination, particularly using inactivated Mccp strains, has shown efficacy in reducing morbidity and mortality, although availability and strain coverage remain challenges (14). Improvements in husbandry—such as reducing animal density, ensuring adequate ventilation, and minimizing stress—also play critical roles in disease prevention and overall herd health (47). Thus, combining imaging modalities like TUS with these broader management strategies can enhance the early identification and control of CCPP outbreaks.

Thoracic ultrasound is grounded in the propagation and reflection of high-frequency sound waves at tissue interfaces (48). In healthy lungs, the aerated alveolar spaces act as a barrier, creating a bright pleural line with reverberation “A-lines” beneath it—artifacts produced by reflection from air–tissue interfaces (49). Lung sliding—seen as a shimmering motion synchronized with respiration—indicates normal pleural apposition, while diseased lungs with reduced aeration permit greater ultrasound penetration (50). Consolidation appears as tissue-like hypoechoic regions, sometimes with vertical artifacts as comet-tail “B-lines” or air bronchograms (51). A-lines usually appear in healthy lungs as horizontal, hyperechoic lines resulting from blockage of ultrasound wave propagation by the air contained within lung tissue (19, 52). However, in affected lungs, comet-tail artifacts (B-lines) appear as vertical lines that may be numerous, indicating localized pleural thickening or surface irregularity (45). Similar pathological artifacts have been reported in dairy buffaloes and cattle calves suffering from pulmonary emphysema and interstitial syndrome (53).

Pleural effusions show anechoic/hypoechoic fluid with floating debris or septa (7). This visual clarity enables detection of even small fluid volumes (13). Pleural thickening/adhesions manifest as irregular, non-sliding pleural lines, often indicating fibrinous changes (31).

Thoracic ultrasound for small ruminants requires a portable ultrasound machine equipped with linear (7.5–10 MHz) or micro-convex probes (5–10 MHz), offering optimal resolution for superficial thoracic structures (21). Micro-convex probes are generally preferred for TUS in small ruminants due to their smaller footprint, wider field of view, and superior penetration depth (7). These features allow easier intercostal access and better visualization of pleural effusion and deeper lung lesions. While linear probes offer higher resolution for superficial structures, their limited depth and larger size make them less practical for comprehensive lung assessment in goats and sheep (7).

In addition, power source options include portable generators or rechargeable batteries, enabling field deployment may be required. Additional accessories may be required such as coupling gel, protective covers, and optional Doppler capability, useful for evaluating vascularization of pleural or mediastinal lesions (49). Linear ultrasound probes offer superior pleural surface detail, while micro-convex probes facilitate access between ribs, especially in smaller animals (54). Goats and sheep can be examined standing, in lateral, or sternal recumbency (55), and in sheep with dense wool, clipping may be necessary to improve probe–skin contact—a less critical issue in goats (56).

Systematic scanning of predefined intercostal sites allows ultrasonographic findings to be summarized into a standardized scoring system. The ultrasound staging system recently used to describe the ovine respiratory complex in lambs (17) categorizes lung lesions based on predefined ultrasonographic patterns, including A-lines, B-lines, consolidation (CON), pleural effusion (PE), and abscesses (ABS). Findings across all scanned sites are then summed to assign a severity score, reflecting the extent of pulmonary involvement: Score 0 indicates normal lungs with predominantly A-lines; Score 1, more than five sites displaying B-lines without consolidation; Score 2, more than five sites displaying B-lines with fewer than five sites showing consolidation; and Score 3, more than five sites with consolidation and/or the presence of pleural effusion or abscesses. This system provides an objective and reproducible framework for quantifying lung lesions and linking ultrasonographic findings to clinical severity.

Thoracic ultrasound offers distinctive imaging patterns that support the diagnosis of pulmonary pathologies in small ruminants. Pleural effusion may be present only as attenuated lung sounds and appears ultrasonographically as anechoic fluid layers that deepen ventrally (56, 57). Fibrinous pleurisy, often clinically silent, is characterized by reduced sounds on the affected side and a lattice-like sonographic pattern with interspersed fluid (16, 57). In pyothorax, overlapping rumen sounds may obscure auscultation, while ultrasound reveals fluid with hyperechoic gas echoes (14, 57).

Pleural abscesses may go undetected when focal but, when diffuse, cause systemic signs such as fever, wasting and dyspnea; ultrasonography shows encapsulated hypoechoic to anechoic cavities (58–60). Pleuropneumonia is more clinically evident, with abnormal lung sounds, coughing, and pyrexia, while imaging demonstrates consolidated parenchyma with hyperechoic foci and pleural effusion (19, 56, 60). Further clinical and ultrasonographic details are summarized in Table 2.

To facilitate the clinical evaluation of respiratory disorders in small ruminants, a structured diagnostic workflow employing TUS has been established (Figure 6). This workflow consolidates characteristic ultrasonographic features to support differential diagnosis of prevalent pleuropulmonary conditions. This diagnostic pathway is based on established scientific literature, incorporating the research and clinical observations of experts in the field (16, 18, 38, 56, 57, 61).

The flowchart operates as a decision tree, starting with the initial ultrasonographic examination of the chest. It guides the user through a series of key questions based on the observed images, such as the presence or absence of the “gliding sign” (indicating normal lung movement), the appearance of comet-tail artifacts, and the characteristics of any abnormal fluid or tissue. Based on the answers, the workflow branches out to suggest possible diagnoses, which correlate with the pathologies detailed in Table 1, such as pleural effusion, fibrinous pleurisy, pyothorax, lung consolidation, and abscesses. The ultimate goal of the chart is to lead the practitioner from a generic clinical suspicion to a more specific sonographic diagnosis. Accordingly, when TUS identifies abnormalities such as pulmonary consolidation, pleural effusion, or mass-like lesions, additional diagnostics (e.g., targeted PCR, bacterial culture, or necropsy) should be undertaken promptly to optimize diagnostic accuracy and clinical decision-making.

This structured approach directly enhances diagnostic efficiency at the point-of-care, enabling quicker and more accurate differentiation between common pleuropulmonary pathologies such as pleural effusion, pyothorax, and consolidated pneumonia. Consequently, it empowers clinicians to move beyond presumptive diagnoses and make informed, evidence-based decisions. The ultimate benefit is the facilitation of earlier, more targeted therapeutic interventions and improved herd health management, solidifying TUS as an indispensable non-invasive diagnostic modality in the field.

Despite the growing application of thoracic ultrasound (TUS) in the diagnosis and management of CCPP, several important knowledge gaps remain. While TUS has proven effective in identifying pleural effusion, pulmonary consolidation, and fibrinous adhesions, there is currently no standardized, disease-specific TUS scoring system for CCPP that links ultrasonographic findings with disease severity, prognosis, or herd-level outcomes. Interpretation of ultrasonographic findings therefore remains largely descriptive and operator dependent, contributing to variability in diagnostic conclusions across clinicians and field settings.

In addition, the diagnostic performance of TUS is constrained by several technical and biological limitations. Sensitivity may be reduced during early stages of CCPP, as subtle parenchymal changes and mild clinical signs may not be detectable. Visualization of deep or densely consolidated pulmonary lesions can also be challenging, particularly in obese or large sheep, further limiting diagnostic accuracy. Moreover, key ultrasonographic findings such as pleural effusion and pulmonary consolidation are not disease specific and may occur in other respiratory conditions, complicating differentiation of CCPP from clinically similar disorders (41).

Artificial intelligence promises to enhance both the accuracy and consistency of TUS (64). AI driven tools employing convolutional neural networks have already improved detection of pleural effusion and pulmonary patterns in animal radiographs (64, 65), with cross-modal potential for TUS in ruminants. Veterinary imaging experts recognize AI not as a replacement but as a powerful decision-support tool—reducing operator variability, accelerating image interpretation, and flagging subtle lesions (66). Adaptation of these systems to TUS in small ruminants could facilitate instant lesion detection and scoring, improving diagnostic consistency in field environments (7).

To maximize the benefits of TUS, targeted and scalable training initiatives are essential. A notable example saw veterinary students mastering equine TUS in just 3 weeks using remote self-driven modules and handheld devices (67). Such frameworks could be adapted for small ruminants, combining online tutorials, hands-on workshops, and remote mentorship. In regions where paraprofessionals carry out herd surveillance, structured training programs—employing tele-ultrasound platforms—could dramatically improve early detection rates for CCPP. Field-deployable TUS systems, augmented with AI and telemedicine, can support rapid detection of zoonotic respiratory pathogens—protecting both livestock and communities (68, 69). Additionally, centralized databases of anonymized lung ultrasound images from sheep and goats could support epidemiological tracking of respiratory outbreaks, environmental risk factor mapping, and cross-species disease surveillance (7).

Emerging research (53) underscores TUS's role in not only identifying various pulmonary pathologies and assessing disease severity but also in monitoring treatment responses over time. Looking ahead, integrating TUS into routine veterinary practice could revolutionize the management of respiratory disorders in ruminants, enabling more precise tracking of disease progression and optimization of treatment protocols.