Radiologic Aspects of Mycotic Diseases

Symposium on Radiology

Radiologic Aspects of Mycotic Diseases Norman Ackerman, D.V.M.,* and Crispin P. Spencer, D.V.M. t

There are several systemic mycotic diseases that affect dogs and cats and produce lesions that may be observed radiographically. These include coccidioidomycosis, blastomycosis, histoplasmosis, aspergillosis, cryptococcosis, zygomycosis, and sporotrichosis. Because these diseases produce granulomatous lesions, their radiographic features are similar within an organ system and therefore it is not often possible to make a specific radiographic diagnosis based on the appearance of a single lesion. The diagnosis is usually based on the geographic location in which the animal has lived and the distribution of lesions within the animal. The role of radiology in the evaluation of mycotic disease is to determine· the extent of the disease, to suggest or confirm the diagnosis, or to exclude the possibility of other diseases, such as neoplasia or bacterial infection, which may present confusing clinical signs. Radiology offers an advantage over many laboratory tests in that the results are often available soon after the animal is examined; therefore the radiographic examinations can indicate what other tests should be performed. Rarely can the specific diagnosis be made solely from the radiograph. The clinician must be aware of those diseases prevalent in the geographic area, as well as the animal's age, breed, and presenting complaint when reaching a diagnosis. The purpose of this article is to review the radiographic features of mycotic disease with emphasis on their similarities, differences, and those radiographic features helpful to the clinician when other diseases such as neoplasia or bacterial infection must be excluded.

*Associate Professor of Radiology, Department of Special Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida; Diplomate, American College of Veterinary Radiology t Assistant Professor of Radiology, Department of Special Clinical Sciences, University of Florida College of Veterinary Medicine, Gainesville, Florida; Diplomate, American College of Veterinary Radiology

Veterinary Clinics of North America: Small Animal Practice-Yo!. 12, No.2, May 1982

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COCCIDIOIDOMYCOSIS

Dogs are reported to·be the species most susceptible to coccidioidomycosis;9 few cases have been reported in cats. 9· 17• 24 The disease occurs so frequently in the endemic area (southwestern United States) that most cases are probably not reported. A benign, nonprogressive form of coccidioidomycosis with mild upper respiratory infection occurs in humans, and it is likely that a similar form occurs in dogs and cats. Therefore only a few of the exposed animals develop clinical signs sufficient for them to be brought to a veterinarian's attention. In necropsy surveys conducted in endemic areas, lesions have been demonstrated in the lungs and tracheobronchial lymph nodes in apparently healthy stray dogs. 9 Most symptomatic dogs develop respiratory signs varying from a harsh to a soft, shallow, nonproductive cough, reportedly due to tracheal and bronchial compression by a granulomatous lymphadenopathy. Dissemination occurs about four months after an experimentally induced primary pulmonary infection. The majority of the disseminated cases occur in young dogs (less than two years old) and in Boxers and Doberman Pinschers. 9 The gross lesions may occur throughout the body but are most frequently confined to the thoracic cavity. In cats the clinical signs and pathologic lesions are similar to those in dogs, but the disease is much less common.9 Tracheobronchial lymphadenopathy, increased bronchial ,or interstitial density, and nodular pulmonary lesions are considered pathognomonic for coccidioidomycosis in endemic areas (Fig. 1). Focal alveolar disease and cavitated pulmonary masses also occur although less frequently, and large areas of lung lobe consolidation are rarely seenY· 20 Although pericardia! or myocardial disease has been reported in 37 per cent of a group qf infected dogs at necropsy, massive pericardia! effusion and pleural fluid have been noted rarely on thoracic radiographs. Small amounts of pleural fluid or fibrosis often accompany the pulmonary lesion. 14 Tracheobronchial lymphadenopathy is a frequent radiographic finding, although sternal lymphadenopathy was not identified. 14 This feature may be helpful in distinguishing coccidioidomycosis from lymphosarcoma in endemic areas since sternal lymphadenopathy is a frequent radiographic finding in lymphosarcoma. 2 The tracheobronchial lymphadenopathy may produce compression of the terminal trachea and stem bronchi, and this may be identified radiographically even though the lymph nodes themselves are not visible. 14 Multicentric osteomyelitis characterized by bony destruction and proliferation occurs in both the axial and appendicular skeletons.14 Most bony lesions are of a mixed pattern (productive and destructive) and affect both the periosteal and endosteal surfaces (Fig. 2). The appearance of the bone lesion can vary within an individual as well as between individuals. Early lesions tend to be more destructive and become denser with time. Solitary lesions occur, but most dogs with bone infection have multiple sites of involvement. 14

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Figure l. Lateral thoracic radiograph of a 10 month old Weimeraner with a cough and fever of two weeks' duration. A density is evident surrounding the tracheal bifurcation, indicative of tracheobronchial lymphadenopathy. The pulmonary interstitial dens ity is increased. This dog lived in an area endemic for coccidioidomycosis, which was confirmed serologically. (Courtesy of Dr. Ralph Slusher.)

Although the metaphyses of long bones and the nutrient artery area have been described as frequently involved sites, no specific location was detected in another report.9· 14 The bony lesion may be asymptomatic. Septic arthritis is uncommon but has been described. 14 Primary cutaneous infection has been described in a dog and a cat. No thoracic ot bony lesions were identified. 24

BLASTOMYCOSIS Dogs are reporte d to be the most susceptible animals to blastomycosis.9 The lungs are the primary focus of infection in most cases, and dissemination may occur to other sites. At least ten cases have been reported in cats. 8• 9 In the endemic area (eastern United States and southern Canada), a combination of tracheobronchial lymphadenopathy with or without pulmonary lesions combined with a history of cough and ocular or cutaneous lesions is highly suggestive of blastomycosisY The endemic area overlaps that of histoplasmosis. The wide range of clinical features includes ocular lesions, mediastinal and tracheobronchial lymphadenopathy, pneumonia, and osteomyelitis. The occurrence of a mild respiratory form of blastomycosis such as that occurring in histoplasmosis and coccidioidomycosis has not been documented.9

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F igure 2. Lateral radiographs of the left (A) and right (B) forelimbs of a one year old English Se tter presented with a left forelimb lameness and palpable swelling of the left humeral area. The dog was cachectic bu t was bright, alert, and afebrile. A mixed (productive and destructive) lesion is visible affecting the entire left humerus as well as the proximal and distal radial metaphyses . The entire right ulna and proximal right radius have similar lesions. The lesions are predominantly sclerotic. However, areas of d estruction are present (arrows). This dog lived in an area e ndemic for coccidioidomycosis, which was confirmed at necropsy.

Pulmonary interstitial lesions either b ronchial, nodular, or mixe d were reporte d to be th e most common thoracic radiographic abnormality (Fig. 3). Alveolar infiltrate s rare ly occurred and calcification was not seen. 22 Cavitation of the pulmonary lesion occurs. At necrops y varying numbers of pulmonary n odul es containing a purulent exudate may be found. In contrast to histoplasmosis and coccidioidomycosis, thoracic lym ph adenopathy is not common and is visible radiograph ically in only 20 p er cent of the dogs in one series . H owever both sternal and trach eobronch ial lymphadenopathy were described. 22 Ple ural effusion and pleural fibrosis occur in blastomycosis . I n on e dog pleural e fli_Ision was the only radiographic change obse rved. 22 Similar thoracic radiographic changes have bee n obse rved in

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Figure 3. Lateral (A) and ventrodorsal (B) radiographs of a three year old male Collie presente d with a mild cough of three days' and partial anorexia of seven days' duration. The dog was afebrile and appeared healthy. Mild dyspnea at rest and increased bronchovesicular sounds were p resent. A d iflu se nodular interstitial d ensity is evident in the lungs. The cranial mediastinum is widened (arrows) and a d ensity is evident at the tracheal bifurcation , indicative of me diastinal and tracheobronchial lymphadenopathy. This dog lived in an area endemic for blastomycosis, which was confirme d serologically. (Courtesy of D r. Royce Roberts.)

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cats. 8 A pyogranulomatous interstitial pneumonia is seen in most symptomatic cats. Pyothorax was reported in one cat. Central nervous system involvement has been reported in cats; however, radiographic signs were not described. 10 In humans, alveolar disease has been suggested as the, acute manifestation of pulmonary blastomycosis. Resolution of the disease occurs over several months. Nodular infiltrates are thought to represent chronic disease. Cavitation was an infrequent finding. 16 This sequence of events has not been described in animals. Osteomyelitis and septic arthritis occur in blastomycosis but are less common than pulmonary infection. In contrast to coccidioidomycosis, which frequently affects both the axial and appendicular skeletons, blastomycosis primarily involves the appendicular skeleton, with involvement of dorsal spinous processes reported in only one case. 18 In a review of seven dogs with blastomycotic osteomyelitis, only one lesion was detected proximal to the stifle and no lesions were detected proximal to the elbow. 18 Involvement was primarily epiphyseal but also occurred in the metaphysis and diaphysis. Radiographically the lesions were primarily osteolytic, but mixed lesions (both osteolytic and sclerotic) were observed (Fig. 4). Multiple bone involvement was observed but solitary lesions were more common. 18 Although disseminated blastomycosis will involve the abdominal viscera and produce nodules throughout the abdomen, the intestine is usually spared. 9 Diarrhea is rarely a clinical finding; therefore, in contrast to histoplasmosis and zygomycosis, there should be no abnormal findings on a gastrointestinal contrast study. HISTOPLASMOSIS

Dogs are apparently very susc'eptible to histoplasmosis, and although it is primarily a pulmonary disease it may become disseminatedY Histoplasmosis has also been reported in the cat, but it rarely produces clinical signs and in most instances the disease has been demonstrated in necropsy material obtained from apparently asymptomatic animals. In the endemic areas (valleys around the Mississippi River and its tributaries), most cases of active pulmonary disease have been reported in dogs and cats less than three years of ageY Disseminated infection is more common in the dog than in any other species, but many infected dogs have subclinical disease. Animals with involvement of one or several organs outside the thorax are considered to have disseminated disease even though the thoracic lesion is mild or unrecognized. A pulmonary interstitial infiltrate with or without tracheobronchial lymphadenopathy is the most common thoracic radiographic finding in dogs with active disease (Fig. 5). 5 Alveolar infiltrate occurs much less frequently but is a sign of more severe disease. 5 It has been described as lobar with subsequent caseation, calcification, and

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F igure 4. Dorsopalmar (anteroposterior) radiograph of the left foot of a three year old Saint Bernard presented with a weightbearing lameness and swelling of the left foot, which had been present for 10 to 14 days and was unresponsive to antibiotics. The dog was afebrile, but the foot was hot and swolle n ; there were no draining tracts. Mixed bony lesions (productive and destructive) are present in the third and fifth metacarpal bones as well as the third phalanx of the second digit, second phalanx of the fourth digit, and first phalanx of the fifth digit. This dog was from an area endemic for blastomycosis, which was confirmed. (Courte sy of Dr. Royce Roberts.)

encapsulation. 9 A similar pattern has been observed in cats, although the number of reported cases is small. 4 • .5, 13 Tracheobronchial lymphadenopathy is commonly detectable and produces narrowing of the terminal trachea and stem bronchi. 1• ·5 This has been reported as a cause of chronic disease or recurrent cough after apparent recovery from the initial pulmonary infection.! This is presumably due to fibrosis (scarring) of the lymph node granuloma. Pulmonary nodule calcification is common in inactive histoplasmosis. Trach eobronchial lymph node calcification is less common but may occur (Fig. 6). 5 This calcification appears to be unique to histoplasmosis, as it was not reporte d with blastomycosis or coccidioidomycosis. Pleural effusion is not common. Pleural fibrosis or minimal effusion may be observed in the inactive disease. Dissemination of the disease to the abdomen may produce nonspecific radiographic changes. Histoplasmosis may produce peritoneal fluid (a reddish transudate), splenomegaly, mesenteric lymph-

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Figure 5. Lateral thoracic radiograph of a thre e year old English Pointer presented with a nonproductive cough of six weeks' duration. The owner had noticed a decrease in exercise tolerance, but the dog appeared healthy. A diffuse pulmonary nodular interstitial infiltrate is evident. The increased de nsity in the hilar area and ventral deviation of the main bronchus identifies the tracheobronchial lymphadenopathy. A diagnosis of histoplasmosis was confirmed se rologically.

adenopathy, and varying degrees of hepatomegaly.9 Thickened intestinal walls with a nodular mucosal surface have been identified at necropsy. However it has only rarely been demonstrated with gastrointestinal contrast studies . Bony involvement is appare ntly rare despite the frequency with which the organism may be found in the bone marrow of animals with disseminated disease. An osteolytic e xpansile lesion was identified in the femoral diaphysis of a two year old dog. 6 Osteolytic lesions involving the tibial tarsal bone (talus) and multiple carpal bones and a mixed lesion (productive and destructive) of the metaphysis and diaphysis of the third metacarpal bone were reported in histoplasma osteomyelitis and septic arthritis in a five year old cat.l 3 A prolife rative bony lesion was reported in the distal metatarsus of a three year old dog.U From the limite d information available, bony involve ment appears to be rare and no definite radiographic pattern can be established. As with other systemic mycoses either osteolytic or sclerotic bone lesions occur. ASPERGILLOSIS

Aspergilli are found throughout the world and produce a granulomatous disease primarily involving the re spiratory system of the

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Figure 6. Lateral thoracic radiograph of an eight year old German Shorthair Pointer. The dog was asymptomatic but was radiographed prior to being anesthetized for a femoral fracture repair. Calcification of the tracheobronchial lymph nodes and multiple pulmonary calcifications are evident. Because this dog lived in an area endemic for histoplasmosis, the calcification was assumed to be due to that disease.

dog and cat. Infection of th e nasal passages and sinuses is most frequent in the dog.9 Fatal pulmonary aspergillosis has been reported in cats, and disseminated aspergillosis was reported in a dog. 1·3, l 9, 25 Osteomyelitis and discospondylitis occur and pathologic fi·acture s were observed. 25 The major diagnostic problem lies in the distinction between aspergillus nasal infection and tumor. An association has been made between areas of decreased density within the nasal passages and aspergillus infection.7 This decreased de nsity may result from necrosis and sloughing of the nasal turbinates with drainage of the exudate from the external nares. This is in contrast to n eoplastic conditions in which the tumor occupies the normal air passages and, therefore, the de nsity of the nasal passage increases or remains unchanged. Obliteration of the nasal air passages, erosion of the vomer bone or nasal septum, erosion of frontal or maxillary bones, and accumulation of fluid in the nasal passages or frontal sinues have been observed radiographically with nasal aspergillosis (Fig. 7). The difficulty in radiographic evaluation was emphasized in a review of 15 dogs w ith nasal aspergillosis, in which two lesions were incorrectly diagnosed as neoplasms and four w ere judged to be normal.7 Erosion and/or displacement or deviation of the vomer bone or nasal septum has been reported as strong evidence of nasal neoplasm. The prese nce of an external soft tissue mass has not been observed with nasal aspergillosis and when pre se nt is an indication of nasal tumor.7 Un-

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Figure 7. Lateral (A), ventrodorsal open mouth (B), and frontal (C) radiographs of a four year old German Shepherd D og presented with a right nasal discharge of four months' duration. The density of the right frontal sinus and nasal passage is increased. Areas of d ecre ased density are present within the nasal cavity (arrows). The nasal turbinate pattern is destroyed. A diagnosis of nasal aspergillosis was confirmed by biopsy. Illustration continued on foll owing page

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(Continued).

fortunately many nasal infections and tumors cannot be differentiated radiographically, especially in the early stage of the disease. In addition, nasal foreign bodies and trauma with hemorrhage in the nasal passages can produce similar radiographic changes. The clinician must take into account the complete case before making a diagnosis. Radiographic evidence of pneumonia has been described in aspergillus infection. 9 • 15• 19 Pulmonary granulomas occur. However pulmonary involvement is infrequent; therefore a specific pattern has not been described. The radiographic changes described in aspergillus osteomyelitis and discospondylitis are similar to those observed in bacterial infection at these sites. The diagnosis depends on the isolation of the organism from the lesion. Radiography is helpful in demonstrating the bony lesion as a source of the animal's clinical signs, in assessing the extent of the disease and in evaluating progression or regression of the disease, but the radiographic changes do not permit a specific diagnosis. CRYPTOCOCCOSIS

In dogs and cats, cryptococcosis is characterized b y pulmonary and central nervous system involvement and/or by localized oral and nasal lesions. 9 · 10· 23 The primary focus and means of dissemination have not been established, although most cases are thought to result from inhalation of the organism with subsequent spread to skin, bone, abdominal viscera, and brain. Pulmonary lesions and generalized infection have been described with or without central nervous system involvement. Cryptococcosis is reportedly the most freque ntly recognize d systemic fungal infection in cats and is unique in being more common in cats than in dogs. 9 • 2:3 A benign, self-limiting form of the disease has not bee n demonstrated.

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Although pulmonary involvement is rare, miliary granulomatous nodules and solitary small abscesses or large solid lesions occur. 23 Lesions in the upper respiratory tract may be demonstrated radiographically as increased density of the nasal passage and frontal sinuses. Involvement of the bulla ossea has been described; however bony proliferation is' rare (Fig. 8). 9 • 23 It has been suggested that cryptococcosis occurs only in subjects whose resistance has been lowered by debility, malnutrition, immune deficiency, immunosuppression, or preexisting disease. Cryptococcosis has been reported in a dog and in three cats with lymphoma.9· 12• 23 The clinician should examine the radiograph for evidence of other coexisting diseases. ZYGOMYCOSIS

Zygomycosis was thought to be a rare disease in dogs and cats. 9 A recent report of 17 cases over an eight year period suggests that the disease may be more prevalent and the true disease incidence has not been established. 3 There are apparently no geographic limitations to this organism, and it has been found widely distributed in soil, water, decomposing organic matter, and food. 9 The conditions required for animal infection are unknown. Zygomycosis appears to be a disease of young animals. It may produce a localized granulomatous mass involving the skin and subcutaneous tissues of the extremities and extending into the bone. The radiographic appearance of this infection in bone has not been described. . Granulomatous lesions have been described throughout the intestinal tract. A gastrointestinal contrast study is required to establish the diagnosis, locate the lesions, and determine the extent of involvement. A soft tissue mass or thickened intestinal wall may be evident on noncontrast radiographs (Fig. 9). Ulceration of the mucosal surface, irregularity of the luminal margins, rigid bowel walls with an absence of peristalsis, and a thinned contrast column may be evident in the contrast study (Fig. 10). The lesions may be solitary or multiple. The animal's age will suggest a granulomatous rather than a neoplastic lesion since the radiographic features of these conditions are similar. Biopsy of the lesion is necessary for a definitive diagnosis. The prognosis in this disease appears to be grave, with death due to peritonitis or failure to respond to therapy. 3 The incidence of a mild or inapparent infection that occurs in many mycotic diseases is not known. SPOROTRICHOSIS

Sporotrichosis is a chronic granulomatous disease that has been reported primarily as a wound infection in dogs and cats. The orga-

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Figure 8. Lateral (A ), ventrodorsal open mouth (B), and frontal (C) radiographs of a four year old cat presented with a nasal exudate and a gradually increasing swelling of one year's duration. The density of the left nasal passage and frontal sinus is increased. The left frontal bone is thickened and distorte d. The nasal turbinate pattern is destroyed. Cryptococci were ide ntifie d in smears of the nasal exudate . Illustration continued on fo llowing page

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(Continued ).

Figure 9. Lateral abdominal radiograph of a one year old Schnauzer presented with a history of intermitte n t vomiting of four months' duration . T he dog exhibited pain upon abdominal palpation. An irregular soft tissue dense mass is visible in the crania l ventra l abdomen (arrows).

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Figure 10. Late ral abdominal radiograph from a barium gastrointestinal series on the Schnauzer in Figure 9. The irregular mucosal pattern of the small intestine is evident (arrows) as it passes through the soft tissue mass. Z ygomycosis was identified histologically after resection of the granulomatous mass.

nism becomes implanted subcutaneously following cutaneous injury. Disseminated disease with metastatic granulomatous lesions throughout the viscera has been reported in the dog. 9 In contrast to most mycotic diseases, primary respiratory infection is unknown or unreported. Radiographic manifestations of sporotrichosis have not been describe d . The organism is found throughout the world as a saprophyte ; the re fore, the potential for infection exists. Only a few cases 'have been . reported and these were limite d to wound infections, with only one reporte d case of disseminated infection without a description of radiographic signs.9 CONCLUSION

The radiographic feature s of mycotic diseases are similar; how ever, each dise ase has its unique feature s. The lymph node and pulmonary calcification common in histoplasmosis is not reporte d in coccidioidomycos is or blastomycosis. The bony involvement in the latter two diseases is rare in histoplasmosis. Cryptococcosis and aspergillosis affect the nasal p assages and sinuses more often than the lung. Zygomycosis will produce intestinal granulomas not observed with most othe r mycotic diseases. Sporotrichosis seems to b e confine d to cutaneous lesions, and radiographic manifestations have not bee n describe d.

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The geographic distribution of mycotic diseases and the fact that most affect young animals is extremely helpful in their recognition, especially in light of the overlap of clinical and radiographic features. Radiographic evaluation is useful in confirming the disease, evaluating the extent of involvement, and following the course of the disease. The radiographic changes may be found throughout the body, and it is often the distribution of the lesions rather than their specific appearance that makes the radiographic diagnosis of mycotic disease possible.

REFERENCES l. Ackerman, N., Cornelius, L. M., and Halliwell, W. H.: Respiratory distress associated with histoplasma-induced tracheobronchial lymphadenopathy in dogs. J. Am. Vet. Med. Assoc., 163:963, 1973. 2. Ackerman, N., and Madewell, B. R.: Thoracic and abdominal radiographic abnormalities in th~ multicentric form of lymphosarcoma in dogs. J. Am. Vet. Med. Assoc., 176:36, 1980. 3. Ader, P. L.: Phycomycosis in fifteen dogs and two cats. J. Am. Vet. Med. Assoc., 174:1216, 1979. 4. Breitschwerdt, E. B., Halliwell, W. H., Burk, R. L., et a!.: Feline histoplasmosis. J. Am. Anim. Hosp. Assoc., 13:216, 1977. 5. Burk, R. L., Corley, E. A., and Corwin, L.A., Jr.: The radiographic appearance of pulmonary histoplasmosis in the dog and cat: A review of 37 case histories. Vet. Radio!., 19:2, 1978. 6. Burk, R. L., and Jones, B. D.: Disseminated histoplasmosis with osseous involvement in a dog. J. Am. Vet. Med. Assoc., 172:1416, 1978. 7. Harvey, C. E., Biery, D. N., Morello, J., eta!.: Chronic nasal disease in the dog: Its radiographic diagnosis. Vet. Radio!., 20:91, 1979. 8. Hatkin, J. M., Phillips, W. E., and Utroska, W. R.: Two cases of feline blastomycosis. J. Am. Anim. Hosp. Assoc., 15:¥.17, 1979. 9. Jungerman, P. F., and Schwartzman, R. M.: Veterinary Medical Mycology. Philadelphia, Lea and Febiger, 1972. 10. Kornegay, J. N.: Feline neurology. Compend. Contin. Ed., 3:203, 1981. ll. Lau, R. E., Kim, S. N., and Piruzok, R. P.: Histoplasma capsulatum infection in a metatarsal of a dog. J. Am. Vet. Me d. Assoc., 172:1414, 1978. 12. Madewell, B. R., and Ackerman, N.: Lymphosarcoma and cryptococcosis in a cat. J. Am. Vet. Med. Assoc., 175:65, 1979. 13. Mahaffey, E., Gabbert, N., Johnson, D., et a!.: Disseminated histoplasmosis in three cats. J. Am. Anim. Hosp. Assoc., 13:45, 1977. 14. Millman, T. M., O'Brien, T. R., Suter, P. F., eta!.: Coccidioidomycosis in the dog. Vet. Radio!., 20:50, 1979. 15. Fakes, S. P., New, A. E., and Benbrook, S. C.: Pulmonary aspergillosis in a cat. J. Am. Vet. Med. Assoc., 151:950, 1967. 16. Rabinowitz, J. G., Busch, J., and Buttram, W. R.: Pulmonary manifestation of blastomycosis. Radiology, 120:25, 1976. 17. Reed, R. E., Hoge, R. S., and Trautman, R. J.: Coccidioidomycosis in two cats. J. Am. Vet. Med. Assoc., 143:953, 1963. 18. Roberts, R. E.: Osteomyelitis associated with disseminated blastomycosis in nine dogs. Vet. Radio!., 20:124, 1979. 19. Sautter, J. H., Steele, D. S., and Henry, J. F.: Aspergillosis in a cat. J. Am. Vet. Med. Assoc., 127:518, 1955. 20. Silverman, S., Poulos, P. W., and Suter, P. F.: Cavitary pulmonary lesions in animals. Vet. Radio!., 17:134, 1976. 21. Stickle, J. E., and Hribernik, T. N.: Clinicopathological observations in disseminated histoplasmosis in dogs. J. Am. Anim. Hosp. Assoc., 14:105, 1978.

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22. Walker, M. A.: A review of thoracic blastomycosis and a study ofits radiographic manifestations in 40 dogs. Vet. Radial., 22:22, 1981. 23. Wilkinson, G. T.: Feline cryptococcosis: A review and seven case reports. J. Small Anim. Pract., 20:749, 1979. 24. Wolf, A. M.: Primary cutaneous coccidioidomycosis in a dog and cat. J. Am. Vet. Med. Assoc., 174:504, 1979. 25. Wood, G. L., Hirsh, D. C., Selcer, R. R., et al.: Disseminated aspergillosis in a dog. J. Am. Vet. Med. Assoc., 172:704, 1978. College of Veterinary Medicine University of Florida J-102, JHMHC Gainesville, Florida 32610