Chronic suppurative pneumonia is a difficult diagnosis in farm animal practice Figures 1, 2 and 3 because cattle have often been treated by the farmer before presentation, and other chronic bacterial infections such as peritonitis, endocarditis, pericarditis, liver abscessation, pyelonephritis, and metritis can be presented with poor production and weight loss. Cows affected by chronic suppurative pneumonia are commonly afebrile at presentation even when there has been no prior antibiotic administration. Purulent nasal discharge Figure 4 and frequent coughing are common presenting signs in cattle with chronic suppurative pneumonia but these signs are also present in infectious bovine rhinotracheitis, a disease where there are no lung lesions.
Descriptions of adventitious sounds are very variable and the extent to which these sounds can be auscultated over specific lung pathologies has been questioned in ovine respiratory diseases [1–3]. The ability to ascertain the nature and distribution of lung pathology by auscultation remains unproven [4] despite the fact that it remains the cornerstone of clinical examination of the ruminant respiratory tract [5, 6].
Reference textbooks on clinical examination describe abnormal lower respiratory sounds in ruminants as clicking, popping or bubbling sounds, crackling sounds, wheezes, and pleuritic friction rubs [7]. A wide range of descriptors has also been used in the clinical literature for abnormal lung sounds in sheep including increased vesicular sounds for a ram with severe chronic suppurative pleuropneumonia [8], and wheezing, rubbing vesicular and murmuring sounds in sheep with bacterial respiratory infections, followed by absence of residual bronchial catarrh in the same sheep during recovery [9]. However, authors in more recent papers [10, 11] have limited their descriptions of auscultation findings of the respiratory tract to distribution rather than character; no abnormal sounds recorded (score 0), abnormal sounds audible predominantly anteroventrally (score 1), abnormal sounds audible throughout the entire lung field (score 2), or have simply commented in a more general sense on the presence of ‘loud and prolonged respiratory sounds’ [12]. The lack of correlation between lungs sounds and distribution of pathology in “wheel-barrow negative” ovine pulmonary adenocarcinoma (OPA) cases [4], despite the OPA lesions extending to involve up to 20% of lung tissue, serves to emphasise the apparent lack of sensitivity and specificity of auscultation.
The purpose of this article is to present images and video recordings highlighting the clinical, sonographic, and necropsy findings of cows with chronic suppurative pnemonia. Sounds recorded over typical ultrasound images are presented with the lesion type confirmed at necropsy in those cattle that did not respond to antibiotic treatment.
Alternative approaches to the diagnosis of chronic suppurative pneumonia in general practice include the response to antibiotic therapy although this regimen would also treat chronic bacterial infections affecting other organs and does not confirm the presence of lung pathology. Radiography could be attempted but presents practical problems with access to the cranio-ventral lung lobes, health and safety regulations, cost, and availability of suitable x-ray machines. Isolation of recognised respiratory tract pathogens from the lower airways and lung via broncho-alveolar lavage and trans-tracheal wash indicates infection but does not quantify the extent of the disease process.
This case study presents clinical findings, including sound recordings over normal and diseased lung and ultrasound images, from adult cattle with chronic suppurative pneumonia. Interpretation of auscultated sounds presents numerous problems and may often be mistakenly interpreted that there is little or no lung pathology present. The primary aim of this report is to demonstrate to veterinary colleagues that ultrasonography is a cost-effective and practical ancillary test in the investigation of suspected respiratory disease on farm. Encouraging results have been achieved in some cases using an extended course of procaine penicillin injections where previous antibiotic therapy, primarily with fluoroquinolones, had failed to effect any improvement. Veterinarians are coming under increasing pressure to reduce the amounts of antibiotics they prescribe because of the perceived association between antibiotic use in farmed species and the rise in multiple antibiotic resistant bacteria in humans. This study provides evidence that extended duration of penicillin therapy achieves good success in selected cases of chronic suppurative pneumonia; veterinarians should combine data from their daily clinical work to provide the necessary information to maintain their right to prescribe.
Case description
Cases
The Farm Animal Hospital at the University of Edinburgh receives ruminant cases from local veterinary practices in south-east Scotland. Twelve adult cattle with chronic suppurative pneumonia admitted over a two year period (2009–2011) were examined by the author and included in this study; 11 Holstein dairy cattle including seven recently-calved heifers, and one pedigree Simmental cow. Adult cattle with other causes of lung pathology were excluded from the study. Six animals were receiving treatment at admission comprising a fluoroquinolone antibiotic (five cows) and oxytetracycline (one cow).
Clinical examination findings
The duration of clinical signs was reported to be between 5–14 days although this could not be verified. All cows were in poor body condition (median 1.5; range 1.5-2.5, scale 1–5). Appetite was markedly reduced and all animals refused their concentrate ration. Milk production was reported to be 25 to 50 per cent of expected yield. Eight cows, including four receiving antibiotics, presented with a sub-normal to normal rectal temperature (37°C to 38.5°C); four cows showed a slight fever (39°C to 39.2°C) including two cows receiving antibiotic treatment. All cows were reluctant to move, dull and depressed and typically stood with the neck extended and the head held lowered. Two cows were dyspnoeic at presentation. Subjective visual appraisal suggested that all cows had an anxious/painful expression. All cows coughed repeatedly during the clinical examination, ultrasonographic and sound recording session which lasted for a total of approximately 15 minutes. A purulent unilateral or bilateral nasal discharge was present intermittently but was noted in all cows at some stage during the examination period. The respiratory rate was increased in all animals above 40 breaths per minute. Marked flaring of the nostrils was observed during inspiration in four animals. No other significant infections were detected during the clinical examination or at necropsy of four cows which did not respond to treatment. Cows were treated with 12 mg/kg procaine benzylpenicillin injected intramuscularly once daily into the muscles of the neck or hindquarters. Four cows discharged before the end of the 42 days’ treatment course (two cows after 14 days; two cows after 30 days) were treated by the owner. The importance of completing the treatment course was emphasised to the owner and referring veterinarian but compliance could not be guaranteed.