When to consider aspergillosis in dogs - Veterinary Medicine
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When to consider aspergillosis in dogs
Sinonasal and disseminated aspergillosis—the two classic presentations—are caused by different Aspergillus fungi. Learn how to manage these clinically distinct infections, and find out how the prognoses for affected dogs differ between the two.


VETERINARY MEDICINE


DISSEMINATED ASPERGILLOSIS

Disseminated aspergillosis is relatively rare in dogs compared with the sinonasal form. Infection is thought to occur through the respiratory tract with subsequent hematogenous spread to other sites, including intervertebral disks, kidneys, and irises as well as other organs, muscles, and long bones.1

Although several Aspergillus species have been isolated from dogs with disseminated disease, Aspergillus terreus and Aspergillus deflectus predominate.23 Many affected dogs have underlying immunocompromise, such as diabetes mellitus or bacterial infections, or are receiving immunosuppressive medications, such as glucocorticoids or chemotherapeutics. Genetic factors may also play a role, as German shepherds are substantially predisposed to this disease.1,23

Clinical findings


Figure 6. A lateral radiograph of the lumbar spine of a dog with diskospondylitis at the L4-L5 disk space. Lytic and proliferative changes are noted at the vertebral end plates. The metal pins had been placed several years earlier after a traumatic injury. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)
The clinical signs of disseminated disease depend on the organ systems involved, although many dogs have nonspecific signs such as anorexia, lethargy, and fever.23 As diskospondylitis is commonly noted, many dogs present with vertebral pain, paraparesis, paraplegia, or lameness. While the disease develops over several months in most cases, dogs may present with a relatively acute onset of illness.

Diagnostic approach


Figure 7. A lateral spinal radiograph of a dog with extensive diskospondylitis of the thoracic vertebrę. Severe lysis of numerous vertebral bodies and end plates is evident. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)
As most patients present with systemic illness, a thorough diagnostic evaluation is necessary. Abnormalities in the complete blood count results are expected and may include mature neutrophilia, eosinophilia, and monocytosis, along with a normocytic, normochromic, nonregenerative anemia.1,23 Hyperglobulinemia, hypoalbuminemia, and azotemia may be noted on a serum chemistry profile. Various degrees of hypercalcemia may also occur, secondary to the granulomatous inflammation or renal failure.23

Imaging studies. Radiographs and CT may reveal lesions associated with diskospondylitis (collapsed disk spaces, proliferative bony changes adjacent to the intervertebral disk spaces, sclerosis) or lysis and destruction of long bones (Figures 6-8).


Figure 8. A transverse CT image of the dog in Figure 7 taken at the level of the T4-T5 disk space. Note the lysis of the proximal ribs and vertebral end plate. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)
Ultrasonography may reveal changes in affected organs. Dogs with renal infection may have pyelectasia with hyperechoic debris within the renal pelvis (Figure 9).

Confirmatory testing. Cytologic identification of Aspergillus species can be made by sampling affected tissues (urine, blood, synovial fluid, lymph node, bone or intervertebral disk material).1,23 In addition, Aspergillus species may be cultured from the urine of affected dogs.


Figure 9. An ultrasonographic image of the kidney of a dog with disseminated aspergillosis and a positive urine fungal culture result for A. terreus. Note the turbid material within the dilated renal pelvis. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)
As with sinonasal aspergillosis, serum antibodies provide useful supportive evidence but cannot be relied upon to establish a definitive diagnosis. False negative results are common, as the AGID generally uses antigens from A. fumigatus, A. niger, and A. flavus and these species are rarely found in dogs with disseminated disease.23 The Platelia Aspergillus EIA appears to be useful in diagnosing invasive disease in people, but little information is available about this test in dogs with disseminated infection.8 One study comparing an ELISA-based antibody detection method with antigen measurement in dogs showed a lower sensitivity with the latter.24


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