Bovine Respiratory Disease: Its Radiological Features

Bovine Respiratory Disease: Its Radiological Features

ROBIN LEE'

INTRODUCTION

Bovine respiratory disease, while not showing the wide diversity of lesions seen in the dog or in man, nevertheless is an important common clinical problem in veterinary medicine. Very little information is available in the literature on the radiological appearance of the bovine lung, either normal or diseased.

An attempt has been made to study these changes in cattle presented to the Uni- versity of Glasgow during the course of an investigation into chronic respiratory disease. Particular interest has been taken in recently recognized bovine respiratory syndromes bearing close similarities to certain human respiratory conditions, and thought to have a similar course, and possibly cause. Because of the nature of these investigations, the cases studied do not necessarily include the more commonly occurring respiratory conditions observed in the field. Certain conditions such as viral pneumonia are either under rep- resented or not included a t all.

LITERATURE REVIEW

No major descriptions of the radiology of bovine respiratory disease have been found in the literature. It is not proposed to give a detailed review of the human literature, although pertinent references are included in the discussions of the specific conditions studied.

MATERIALS AND METHODS

Forty-two animals have been studied. The range of conditions seen is presented in Table 1. Thirty-five cattle were subsequently slaughtered and necropsy confirmation of the final diagnosis was ob- tained.

Standing lateral radiographs of the thorax were taken with the x-ray beam centered over the sixth rib, midway be- tween the posterior angle of the scapula and the olecranon process of the elbow. This provided a good projection of the diaphragmatic lobes and the dorsal parts of the cardiac and intermediate lobes in most instances.

Positioning was greatly facilitated by the use of a linked x-ray tube and image intensifier suspension system, which was fitted with a cassette holder (Fig. 1). This allows the x-ray tube to be positioned accurately while the cassette remains accurately centered on the x-ray beam. The x-ray tube is powered by a 200 kV, 1,000 mA, three phase generator.

Par speed 35.6 X 43.2 cm film and screen^,^ were used in conjunction with a focused grid (grid ratio 10 : 1, 44 lines/cm). Exposure factors varied with individual animals, but for most cattle were within the range 45-55 kV and 80-130 mAs a t a film focus distance of 100 cm. In some of the subjects respiratory movement blur was a problem. The use of a higher kV (70-75 kV) allowed the mAs to be reduced,

Lecturer in Veterinary Surgery, Faculty of Veterinary Medicine, University of Glasgow, Glasgow, This manuscript is based on a paper presented at the third conference of the International

Siemen 3D Suspension System, Siemens Aktiengesellschaft, Warnerwerk fur Messtechnik, Karlsruhe,

Elema Schonander Triplex Optimatic, Elema Schonander AB Industrivagen 23, Stockholm-Solna,

Kodak R. P. Royal X-Omat Film and Par-speed X-Ray Intensifying Screens, Kodak, Ltd., Lon-

Scotland. Veterinary Radiology Association in Washington, D. C., Sept. 5-7,1973.

Federal Republick of Germany.

Sweden.

don, England.

41

42 R. LEE 1974

Fig. 1. A view of the x-ray tube and image intensifier with the cassette holder attached and prepared for standing lateral radiography.

Table 1 . The Distribution of Cases of Chronic Respiratory Disease Examined Ra diog ra phica Ily

Disease No of Cases

Extrinsic allergic alveolitis (Bovine Farm- er’s lung) Diffuse fibrosing alveolitis Parasitic bronchitis due to Diclyocaulus viviparous Bronchopneumonia Chronic interstitial pneumonia Thrombosis of the posterior vena cava Hyaline membrane disease (no necropsy available) Cuffing pneumonia Clinically normal animals with no abnormality detected at necropsy

9 4

1 1

8

thus reducing the risk of movement blur. No attempt was made to obtain radiographs of the cardiac or apical areas of the lung field, as previous experience had indicated that this was of limited value. Neither was any attempt made to obtain dorsoventral projections of the thorax.

RESULTS

The Normal Bovine Lung

The appearance of the noimal adult bovine lung field is presented (Fig. 2). The most noticeable feature is the very obvious bronchovascular pattern with the main diaphragmatic bronchi and cardiac

Fig. 2. The radiographic appearance of the normal bovine lung field. Note particularly the obvious bronchovascular pattern with the main diaphragmatic bronchi passing dorso- caudally in the dorsal third of the lung field with the subdivisions radiating in a fan-like manner over lung field.

bronchi readily identifiable. The main diaphragmatic bronchus passes dorso- caudally in the dorsal third of the diaphragmatic lobe and subdivides to form acute angles of approximately 30 O with the main bronchus both dorsally and ventrally and radiate in a fanlike manner over the lung field. The ventral branches are larger than the dorsal branches.

The bronchi and pulmonary vessels run together. The vessels are not individually distinguishable. The bronchovascular subdivisions can generally he traced to the second or third branch. The aorta and caudal vena cava can, of course, be identified. In addition, care must be taken to identify either fluid or gas con- tained within the esophagus running dorsal to the caudal vena cava. This may be recognized occasionally as there may be eructation or regurgitation of ruminal contents during the course of the radiographic exposure.

The Radiological Appearance of Selected Respiratory Conditions

Bovine Parasitic Bronchitis Due to Infection with Dictyocaulus Viviparous

The clinical features and course of this condition are well recognized and described (3-6). Three cases of naturally occurring

VOL. xv BOVINE RESPIRATORY DISEASE 43

Fig. 3. Bovine parasitic bronchitis due to experimental infection with D. viviparous. A B

The normal appearance prior to infection The appeorance in the alveolar-bronchial phase, three weeks after infection showing a marked mottled loss of translucency in the periphery of the lung field and particularly around the main diaphragmatic bronchi

parasitic bronchitis have been studied in addition to three animals that were experi- mentally infected by the endobronchial administration of approximately 8,000 larvae. Radiographs were taken of the experimental animals immediately prior to infection and at weekly intervals until sacrificed five to six weeks later.

The changes in the radiological appearance were of a diffuse, mottled, honey- comb-like loss of translucency which in the early stages was most obvious in the peripheral portion of the lung field and especially noted around the terminal por- tions of the main diaphragmatic bronchi and their branches, and to a lesser extent around the cardiac bronchi (Fig. 3). In more advanced disease this mottled honey-

comb-like appearance became generalized over the whole lung field. In addition, there was associated peribronchial reaction (Fig. 4). In the latter stages of infection the appearance became very similar to that seen in chronic pneumonia,

These radiological findings correlate well with the distribution of lesions observed a t necropsy. In the earlier alveolar-bronchial phase of the disease there is diffuse interstitial eosinophilic infiltration and lobular consolidation and collapse which occur predominantly in the periphery of the lung field. In the latter patent phase of the disease, more generalized eosinophilic reaction around the bronchi and associated alveolar epitheliazation and interstitial em- physema are observed.

Extrinsic Allergic Alveolitis (Bovine Farmer’s Lung)

This is a condition only recently recognized in cattle and is probably identical to human Farmer’s lung (2, 7-11). It is seen almost exclusively in housed dairy cattle and is caused by a hypersensitivity reaction to the spores of the thermophilic fungus Micropolyspora faenia. The condition is generally associated with the feed- ing of poor quality moldy hay. Affected animals are bright but show tachypnea, cough, poor condition and a poor milk yield. They may present either as acute or chronic respiratory problems and in

Fig. 4. following infection. lung field compored to Fig. 3 B and its similarity with Fig. 8.

Experiment01 infection with D. viviparous four weeks Note the more generalized mottling of the

44 R. LEE 1974

Fig. 5. (Bovine Farmer’s Lung). peribronchial reaction. be seen on Fig. 5 6 (arrow).

(A and 6) Two examples of extrinsic allergic alvealitis Both of these examples illustrate the

Examples of the nodular opacities can

general several animals in a herd are affected. Often there is a concurrent history of Farmer’s lung in the farmer or animal ’ attendants. Precipitating anti- bodies for Micropolyspora faenia spores are present in the serum.

The radiographs of nine animals in which this condition has been diagnosed clinically

have been examined. The degree of change varied. In a proportion of cattle there was relatively little radiological abnormality. Where there were abnor- malities, the appearance was of a variable degree of peribronchial reaction with delineation of many of the finer bronchioles not generally visualized. In addition a fine generalized granular mottling of the parenchyma was observed. A common feature was the presence of a variable number of fairly discrete nodular opacities, varying in size from 2--6 mm in diameter (Fig. 5).

At necropsy examination there were generally widespread pulmonary lesions with infiltration of the alveolar walls by lymphocytes and plasma cells and the presence of epithelioid granulomata and bronchiolitis obliterans. There was fre- quent cellular infiltration of the bronchial walls.

The pathological appearance is in general agreement with the changes seen in human Farmer’s lung. The radiological appearance bears similarity to the changes seen in the chronic disease in humans and correlates well with the pathological appearance.

Diffuse Fibrosing Alveolitis This is a disease recognized only recently

in cattle. It closely parallels a well recognized human respiratory syndrome (1, 9). The cause is not known but the condition is thought to be the end product of a variety of chronic respiratory diseases. The clinical features are of bright but tachypneic coughing animals showing loss of condition. On clinical examination there are widespread adventitious sounds over both lung fields. Exercise is tolerated very poorly. Only four animals have been examined in which this condition has been diagnosed. The appearance was of a generalized rather hazy loss of radiolucency most noticeable around the main bronchi (Fig. 6). In addition, two of the cattle examined had small discrete opacities intermixed with this generalized change which may indicate that in these animals a


Fig. 6 . The appearance of diffuse fibrosing olveolitis in the bovine with a much more generalized loss o f translucency throughout the whole of the diaphragmatic lobes, most noticeable in the peribronchial areas.

pre-existing allergic alveolitis was an initiating factor. The changes are, however, more diffuse and ill-defined than in other diseases.

At necropsy the lungs do not appear grossly abnormal, but are pale and extremely heavy. On histopathologic examination there is cellular infiltration and fibrosis of the alveolar septa, hyper- plasia and metaplasia of the alveolar epithelium, and in certain areas cuboidal or columnar cells lining the alveoli.

Bronchopneumonia Six cows with the classical pathological

changes of purulent bronchopneumonia

Fig. 7. An example of purulent bronchopneumonia in the adult bovine showing areas of consolidation (arrow No. 1) intermixed with areas of increased radiolucency indicative of emphysematous bullae (arrow No. 2).

Fig. 8. An example of chronic interstitial pneumonia probably resulting from a previous viral pneumonia and showing the generalized reticular mottling of the lung fields very similar to the appearance seen in the chronic stage of porasitic bronchitis (Fig. 4).

(6) identified a t necropsy have been radio- graphed. These radiographs usually had a markedly abnormal appearance with a marked increase in irregular bronchovascular markings. There tended t o be no generalized loss of radiolucency but rather localized patchy areas of alveolar consolidation intermixed with numerous areas of increased radiolucency, probably indicative of emphysematous bullae (Fig. 7) f

Chronic Pneumonia Four examples of chronic pneumonia

were seen in young cattle. These were probably the end result of a viral “cuffing” pneumonia. There were marked radiographic changes of generalized reticular mottling of the lung fields tending to be more obvious ventral to the main diaphragmatic bronchus and extending t o the periphery of the lung field, often with the presence of air bronchograms (Fig. 8). As mentioned previously this appearance was very similar to the end appearance of parasitic bronchitis and in fact this may have in some instances been the initiating pathological change.

Other Diseases In one calf with a tentative clinical

diagnosis of hyaline membrane disease, the radiographic appearance was of a very

46 R. LEE 1974

Fig. 9. Radiograph of a 1 -week-old calf with a clinical diagnosis of hyaline membrane disease showing a rather diffuse ground glass-like opacity of the lung fields and the presence of airbronchograms (arrows).

even ground glass-like opacity of the lung fields which would be consistent with the presumed pathological changes occurring in this disease (Fig. 9). In this animal the condition subsequently resolved and no final pathological confirmation was available.

Two cows with caudal vena cava thrombosis and multiple arterial emboli in the lungs have been examined. One of these had a rather nonspecific over-all mottling of the lung fields with some small discrete

Fig. 10. Multiple pulmonary arterial emboli secondary to thrombosis of the posterior vena cava were present in the lung flelds of this animal and the radiograph shows a rather nonspecific overall opacity of the lung fields particularly noticeable in the perihilar area. A feature of note on this radiograph i s the visibility of the gas filled esophagus (arrow).

Fig. 11. Example of viral or “cuffing” pneumonia in a faur- month-old calf showing generalized peribronchial infiltration and reaction.

opacities peripherally, presumed to be areas of embolic infarction and collapse. This was confirmed a t necropsy (Fig. 10). In the other cow, in addition to the rather generalized mottling seen in the preceding one, there was a very marked loss of radiolucency in the central portion of the diaphragmatic lobe surrounding the main diaphragmatic bronchus. A t necropsy this was found to be a large intrapulmonary hematoma associated with an aneurysm of the pulmonary artery.

Despite the common occurrence of acute viral “cuffing” pneumonia in the field, only one case has been seen in this series (Fig. 11). This animal was used initially as a control for the experimental parasitic bronchitis animals, but developed a “cuffing” pneumonia during the course of the experiment and was culled. The radiographic appearance was of a very marked peribronchial and peribroncheolar reaction. This correlates well with the pathologic changes described in standard texts.


DISCUSSION

The technic of examining the bovine thorax radiographically used in this series may not be ideal in that it does not allow for examination of all areas of the lung field. This, however, has been recognized and accepted as a limitation. The main advantage of the procedure was that the majority of animals could be examined rapidIy and with a minimal amount of restraint or sedation. In the future a modification of exposure technic to employ a somewhat higher kV will enable the use of a shorter exposure time and may be advisable.

Although this study is based on a selected series of cases and many of the commoner conditions are under-rep- resented, it is hoped that it has been pos- sible to demonstrate that certain of these conditions do in fact have a fairly char- acteristic radiological appearance which, while probably not being of great benefit as a diagnostic aid in veterinary practice, are recognizable. Further study and investigation should enable more accurate differentiation of conditions based on the radiographic appearance. This should prove a valuable additional means of study of bovine respiratory disease in develop- mental and experimental veterinary medicine and pathology.

SUMMARY

The radiographic technic utilized in obtaining standing lateral thoracic radiographs of adult bovines is described. The radiological appearance of the normal bovine lung field and the features observed in bovine parasitic bronchitis, bovine Farmer’s lung, diffuse fibrosing alveolitis, bronchopneumonia, chronic pneumonia and similar chronic respiratory problems in the bovine are described and illustrated, and the appearances related to the pathologic changes. Department of Veterinary Surgery University of Glasgow Veterinary School Bearsden Road, Bearsden, Glasgow G61 lQH, Scotland

ACKNOWLEDGMENTS: I would like to ac- knowledge the considerable help in provision of case material and clinical and pathological data from members of the Medicine and Pathology Depart- ments a t the University of Glasgow.

REFERENCES 1. Hamman, L., and Rich, A. R.: Acute Dif-

fuse Interstitial Fibrosis of the Lungs. Bulletin of the John Hopkins Hospital 74: 177, 1944.

2. Hapke, E. J., Seal, R. M. E., Thomas, G. O., Hayes, M., and Meek, J. C.: Farmer’s Lung. A Clinical, Radiographic, Functional and Serological Correlation of Acute and Chronic Stages. Thorax 23: 451, 1968.

The Pathology of Some Types of Pneumonia and Associated Pulmonary Diseases of the Calf. British Veterinary Journal 112: 431,1956.

4. Jarrett, W. F. H., Jennings, F. W., McIn- tyre, W. I. M., Mulligan, W., and Urquhart, G. M.: The Natural History of Parasitic Bronchitis wity Notes on Prophylaxis and Treatment. Veterinary Record 69: 1329, 1957.

5. Jarrett, W. F. H., McIntyre, W. I. M., and Urquhart, G. M.: The Pathology of Experimen- tal Bovine Parasitic Bronchitis. Journal of Path- ology and BacterioIogy 73: 183, 1957.

6. Jubb and Kennedy: The Pathology of Domestic Animals, 2nd Ed. Academic Press, New York, 1970.

7. Pirie, H. M., Dawson, C. O., Breeze, R. G., Selman, I. E., and Wiseman, A.: Fog Fever and Precipitins to Microorganisms of Mouldy Hay. Research in Veterinary Science 12: 586, 1971a.

8. Pirie, H. M., Dawson, C. O., Breeze, R. G., Wiseman, A., and Hamilton, J.: A Bovine Disease Similar to Farmer’s Lung: Extrinsic Allergic Alveolitis. Veterinary Record 88: 346,1971b.

9. Pirie, H. M., Dawson, C. O., Breeze, R. G., Selman, I. E., and Wiseman, A.: Precipitins to M. faeni in the Adult Cattle of Selected Herds in Scot- land and North West England. Clinical Allergy

A Bovine Pulmonary Disease Resembling Human Diffuse Fibrosing Alveoljtis. Proc. Royal Society of Medicine 65: 987, 1972.

11. Wiseman, A., Dawson, C. O., Pirie, H. M., Breeze, R. G., and Selman, I. E.: The Incidence of Precipitins to M . faenia in Cattle Fed Hay Treated with an Additive to Suppress Bacterial and Mould Growth. Journal of Agricultural Science, in press.

12. Wiseman, A., Selman, I. E., Dawson, C. O., Breeze, R. G., and Pirie, H. M.: Bovine Farmer’s Lung: A Clinical Syndrome in a Herd of Cattle. Veterinary Record, in press.

3. Jarrett, W. F. H.:

2: 181-187,1972. 10. Pirie, H. M., and Selman, I. E.:

ZUSAMMENFASSUNG Die rontgenologische Technik, die benutzt wird,

48 R. LEE

bei der Gewinnung von stehenden, lateralen Rontgenaufnahmen des Brustkorbes von erwach- senen Rindern wird beschrieben. Die rontgenologische Erscheinung des normalen Lungenfeldes beim Rind und die Merkmale, die bei parasitischer Bronchitis des Rindes beobachtet wurden, sowie Farmer’s Lunge beim Rind, diffuse fibrosierende Alveolitis, Bronchopneumonie, chronische Pneu- monie und ahnliche chronische Atrnungsprobleme beim Rind werden beschrieben und illustriert, und die Erscheinungen, die sich auf die pathologische Veranderungen beziehen.

1974

RESUME La technique radiographique utilisee pour

obtenir les radios thoraciques laterales en position debout chez des bovides adultes est d6crite. L’aspect radiologique du champ du poumon bovin normal et les signes observes dans la bronchite parasitaire bovine, le poumon de Fermier, l’alv6o- lite B fibrose diffuse, la broncho-pneumonie et des problBmes respiratoires sjmilaires chez le bovid6 sont d6crits et illustr6s ainsi que les aspects reli6s aux changements pathologiyues.

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Bovine Respiratory Disease: Its Radiological Features