Canine and feline histoplasmosis: A review of a widespread fungus - Veterinary Medicine
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Canine and feline histoplasmosis: A review of a widespread fungus
Infection with this pathogenic fungus most commonly results from inhaling spores from contaminated soil. The infection should be treated promptly to avoid dissemination, which carries a poorer prognosis.


VETERINARY MEDICINE


Thoracic radiography


1A & 1B. Lateral and ventrodorsal thoracic radiographs of a 7-year-old American cocker spaniel with pulmonary histoplasmosis. A heavy unstructured interstitial-to-coalescing nodular interstitial pattern is seen throughout all lung fields in both views, partially obscuring the pulmonary vessels.
Dogs. Common thoracic radiographic abnormalities in canine pulmonary histoplasmosis include hilar lymphadenopathy and a bronchial-interstitial or interstitial pattern (Figures 1A & 1B).10,51 Mineralization of lymph nodes and pulmonary infiltrates is occasionally observed and may indicate inactive disease.7,10,11,17,20 Pleural effusion and sternal lymph node enlargement are infrequently observed.17,23,35 Additional unusual findings include a focal alveolar opacity affecting one lung lobe and a fungal granuloma in the thoracic cavity cranial to the heart.35,52

Cats. Unspecified thoracic radiographic abnormalities were present in 27 of 31 (87.1%) cats with disseminated histoplasmosis.1 An interstitial miliary pattern was the most common radiographic abnormality in a study of 12 cats.15 Radiographic patterns in cats with pulmonary histoplasmosis include a fine, diffuse or linear interstitial infiltrate; nodular interstitial infiltrate; or, rarely, alveolar pattern.16,53,54 Enlarged or mineralized tracheobronchial lymph nodes were not a feature of feline pulmonary histoplasmosis.16 Areas of pulmonary consolidation were reported in one cat.54

Abdominal radiography and ultrasonography

Abdominal radiographs in dogs and cats may show hepatomegaly or splenomegaly; ascites was reported in one dog.9,10,15,35,55 On abdominal ultrasonographic examination, the affected liver may have a hyperechoic appearance, as well as nodular lesions.10,36,55 Lymphadenomegaly may also be observed.9

Skeletal radiography

Dogs. Bony lesions of histoplasmosis are rarely reported in dogs; affected sites include the tibia and tarsal, carpal, and metacarpal bones.26,27,56,57 Radiographic abnormalities include soft tissue swelling and joint effusion with osteolysis and proliferative sclerosis.26,56

Cats. In a review of 96 cases of feline histoplasmosis, all seven cats with lameness had changes consistent with osteomyelitis on long bone radiographs.1 Multiple long bones, as well as carpal and tarsal bones, may be affected.38,43,44,58 A predilection for sites distal to the elbow and stifle joints exists.43 Lesions are predominantly osteolytic, with periosteal and endosteal proliferation seen in some cases.43 Bone weakening can result in pathologic fractures that heal after treating the disease.43,44 Additional radiographic changes reported in one cat included soft tissue swelling and subchondral bone collapse.58


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