When to consider aspergillosis in dogs

Aspergillus species are saprophytic fungi commonly found in compost piles, stables, and barns. They were first described in the environment in 1729 and have been associated with diseases in companion animals since 1829. Despite the ubiquitous nature of these organisms, disease occurs in only a small percentage of exposed animals.

In general, this fungal infection in dogs is either sinonasal or disseminated. The two presentations are caused by different Aspergillus species and are clinically distinct, as sinonasal aspergillosis does not lead to disseminated infection and solitary infections outside of the nasal passageways are rare.1

In this article, we review these two classic manifestations of canine aspergillosis and discuss the diagnosis and treatment of affected patients.

SINONASAL ASPERGILLOSIS

Aspergillus fumigatus is the most prevalent isolate in patients with sinonasal disease, although infection can occur with other species including Aspergillus flavus, Aspergillus niger, and Aspergillus nidulans.1 Although disease severity varies, most dogs with sinonasal aspergillosis have marked destruction of turbinate bones and mucosa. In severe cases, destruction of the frontal bones with invasion into the periorbital soft tissues and penetration through the cribriform plate into the central nervous system may occur.

Unlike the disseminated form, canine sinonasal aspergillosis occurs in apparently immunocompetent dogs. However, there is speculation that mucosal immune dysfunction predisposes certain dogs to infection.1-3 In addition, fungal virulence factors may potentiate infection through interference with mucociliary clearance and macrophage phagocytosis.

Sinonasal aspergillosis affects primarily mesaticephalic and dolichocephalic breeds; brachycephalic dogs are rarely affected.2 Most dogs with sinonasal aspergillosis are young to middle aged, with a mean age of 4.4 years (range = 1.5 to 8 years). This is substantially younger than dogs with nasal neoplasia, with a mean age of 9.5 years (range = 4 to 12 years).4

Clinical signs

Clinical findings associated with sinonasal aspergillosis include profuse purulent to mucopurulent nasal discharge, facial discomfort, depigmentation or ulceration of the nares, sneezing, and epistaxis.1,2 Depigmentation is thought to be caused by toxins in the discharge and is not routinely noted with other causes of nasal diseases in dogs (Figure 1).1 Nasal discharge is initially unilateral but can progress to bilateral because of nasal septum destruction. Other signs include decreased appetite, lethargy, stertor, stridor, and open-mouth breathing. In advanced cases, ocular discharge and exophthalmos may be seen, and, in our clinical experience, destruction of the cribriform plate may result in signs of forebrain dysfunction. In the early stages of disease, discharge may be intermittent or only associated with sneezing.

Figure 1. The nasal planum of a dog with sinonasal aspergillosis. Note the erosion and depigmentation. (Image courtesy of Dr. Debra Zoran, Texas A&M College of Veterinary Medicine & Biomedical Sciences.)

Diagnostic approach

Consider sinonasal aspergillosis in any dog with nasal discharge and other compatible clinical findings. Differential diagnoses include nasal neoplasia, idiopathic lymphoplasmacytic rhinitis, a nasal foreign body, tooth root abscessation, and oronasal fistulation.1,2

The physical examination should include facial palpation to check for symmetry and detect pain. Also evaluate airflow through each nostril by using a chilled microscope slide or a cotton wisp.5 Loss of airflow suggests a mass lesion and is not consistent with primary aspergillosis. Perform careful retropulsion of each globe since asymmetric retropulsion may suggest a mass lesion. Examine the hard and soft palates, tonsils, and teeth for evidence of neoplastic erosion or invasion or dental disease.

It is essential to definitively diagnose nasal aspergillosis before starting treatment. As most of the available diagnostic tests have limitations, a combination of tests is often necessary to confirm a diagnosis. These tests include serology, imaging studies, rhinoscopy, cytologic and histologic examinations of affected tissues, and fungal culture. Before inducing anesthesia, perform a complete blood count, serum chemistry profile, and urinalysis to rule out concurrent systemic disease.

Serology. Tests that can detect serum antibodies against Aspergillus species include agar gel immunodiffusion (AGID), complement fixation, and ELISA techniques. The antibodies detected with AGID vary depending on the laboratory; however, most commercial laboratories detect antibodies to A. fumigatus, A. niger, and A. flavus.6 This test is widely available through veterinary diagnostic laboratories and is probably the most commonly performed fungal serologic test at this time. However, a recent study indicated a test sensitivity of only 67% in dogs with sinonasal aspergillosis, suggesting that one-third of affected dogs would have a negative result.7 This reduced sensitivity may be due to infection with a less common Aspergillus species. The test specificity was high at 98%, indicating that false positive results are unlikely. It is important to remember, however, that a positive result with any serologic test does not eliminate the possibility of nonfungal rhinitis and is not enough evidence for a definitive diagnosis of sinonasal aspergillosis.7

In human patients, a sandwich enzyme immunoassay (Platelia Aspergillus EIA—Bio-Rad Laboratories, Marnes-la-Coquette, France) has been used to confirm infection with Aspergillus species by the detection of a cell wall component called galactomannan. This component can be identified in serum and other body fluids such as cerebrospinal fluid or bronchoalveolar lavage fluid.8 Limited information is available on the reliability of antigen detection tests in veterinary medicine, but in a recent study, the sensitivity of this test in dogs with sinonasal disease was only 23.5%.6 The poor sensitivity may reflect the noninvasive nature of this disorder, with limited release of antigens into the circulation.

A recent study evaluated the use of real-time broad-spectrum polymerase chain reaction test fungal DNA detection in whole blood or tissue samples. Detection of fungal DNA in blood was of little diagnostic use because of low positive and low negative predictive values, while identification of Penicillium and Aspergillus species DNA in nasal tissues lacked specificity for sinonasal aspergillosis.9

Imaging studies. All imaging studies should be completed before rhinoscopy and the collection of biopsy samples as hemorrhage can limit lesion detection. Radiographs of the nasal cavity and frontal sinus can be diagnostically useful, but the patient must be anesthetized during the radiographic examination to permit proper positioning. Ideally, lateral, ventrodorsal (both open- and closed-mouth) and rostrocaudal views should be obtained. Common radiographic changes associated with aspergillosis are areas of increased radiolucency, which suggest turbinate destruction.10 Opacification of the nasal cavities and frontal sinuses may also be noted.

The diagnostic sensitivity of radiography is limited by superimposition of bony structures and the complexity of the nasal turbinates. Various studies have shown that magnetic resonance imaging (MRI) and computed tomography (CT) are superior imaging choices in these patients. In 25 dogs with confirmed aspergillosis, CT had a sensitivity of 88% vs. 72% for standard skull radiography.11 In addition, CT and MRI can distinguish unilateral vs. bilateral disease and identify destruction of the bony nasal septum (Figure 2). MRI provides more information about the soft tissue structures of the face, but CT permits detailed evaluation of the cribriform plate and is presently the more popular imaging modality in veterinary patients with overt nasal or sinus disease. Both techniques are useful in determining the best place for a nasal biopsy or the collection of other samples.

Figure 2. A transverse CT image of the nasal passages of a dog with bilateral sinonasal aspergillosis. Note the loss of turbinate structures. (Image courtesy of Dr. Kyle Mathews, North Carolina State University College of Veterinary Medicine.)

Rhinoscopy and sinuscopy. Rhinoscopy allows visualization of the nasal cavity and guided collection of biopsy samples and is routinely performed after imaging studies. In addition, direct examination of the nasal passages may reveal other causes of nasal discharge such as neoplasia or a foreign body. A rigid endoscope (e.g. a cystoscope) or a narrow flexible endoscope (e.g. a pediatric bronchoscope) can be used for this purpose. Premeasure the endoscope from the nasal planum to the ipsilateral medial canthus to avoid penetrating the cribriform plate.

Figure 3. A rhinoscopic image of the nasal cavity of a dog with sinonasal aspergillosis. Note the extensive loss of the normal turbinate structures. (Image courtesy of Dr. Kyle Mathews, North Carolina State University College of Veterinary Medicine.)

Dogs with aspergillosis typically have substantial turbinate loss (Figure 3) and copious, mucopurulent discharge. In addition, fungal plaques may be noted; these are off-white or greenish fuzzy lesions adherent to the mucosa (Figure 4), which may be confused with mucoid material by inexperienced clinicians.1,2 Biopsy samples can be collected through the endoscope or by adjacent placement of a rigid device. It can be helpful to gently roll one sample over a slide for cytologic evaluation before placement in formalin. In addition to nasal passage examination, the nasopharynx can be viewed by using a small retroflexed endoscope or a dental mirror with a rigid endoscope. Biopsy collection is difficult in this area, but a brush may be passed through a flexible endoscope to obtain cytologic samples.

Figure 4. A rhinoscopic image of the left nasal cavity of a dog with sinonasal aspergillosis. The white fuzzy object is a fungal plaque. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)

Although the frontal sinuses may be accessed by using a rostral nasal approach, it can be technically challenging. Alternatively, trephination may be performed to permit insertion of a rigid endoscope.5 Trephination prolongs anesthesia time and increases postoperative discomfort but may provide essential diagnostic information in veterinary patients without rhinoscopic evidence of fungal disease. In one study of 46 dogs with sinonasal aspergillosis, 17% had fungal plaques in the sinuses but not in the nasal cavity.12

In classic cases, the results of CT or MRI studies along with the identification of fungal plaques with rhinoscopy or sinuscopy are enough to establish a diagnosis of aspergillosis, and treatment (described later) can be performed during the same anesthetic event.

Cytology and histology. Histologic and cytologic examinations can provide direct evidence of fungal hyphae (Figure 5), which is strongly supportive of a diagnosis of aspergillosis. The sensitivity of these methods is high if samples are taken from the fungal plaques but tends to be lower if samples are collected without direct visualization.13 Classic histologic findings associated with aspergillosis in dogs include mucosal ulceration and inflammation, with a predominance of lymphocytes and plasma cells.3 However, these changes are nonspecific and may be reported in dogs with severe idiopathic lymphoplasmacytic rhinitis.

Figure 5. Cytologic preparation of a fungal plaque from a dog with sinonasal aspergillosis. Numerous branching hyphæ are evident (modified Romanowksi stain; 400X). (Image courtesy of Dr. Debra Zoran, Texas A&M College of Veterinary Medicine & Biomedical Sciences.)

Fungal culture. Fungal culture has been used in combination with other tests in the diagnosis of sinonasal aspergillosis in veterinary patients. However, false positive and false negative results confound its diagnostic use. Aspergillus species are ubiquitous in the environment and can be cultured from normal dogs and those with neoplastic or inflammatory nasal diseases.1 If a culture is warranted to confirm Aspergillus species vs. other fungal agents, positive results are more likely if the material is obtained by direct sampling of fungal plaques during rhinoscopy.14

Treatment

Effective treatment of canine sinonasal aspergillosis is challenging. Different treatment modalities have been described, including topical and systemic antifungal medications (Table 1) and invasive surgical procedures.

Table 1 Selected Drugs for Treating Aspergillosis in Dogs

Topical antifungals. Topical antifungal medications are regarded as the treatment of choice if the cribriform plate is intact. When used topically, both enilconazole and clotrimazole appear to be more effective in the treatment of sinonasal aspergillosis than oral antifungal agents are. The topical azoles have poor solubility and minimal intestinal absorption and are fungicidal (rather than fungistatic) at higher concentrations.

The first described technique for topical therapy in dogs required surgically placing tubes into the frontal sinus followed by enilconazole instillation twice a day for one or two weeks. This method was 90% effective in dogs without extranasal infection.15

An alternative topical method involves one infusion via both nares of either clotrimazole or enilconazole, performed while the patient is under general anesthesia. A detailed description is beyond the scope of this article, so veterinarians unfamiliar with this procedure should consult additional resources or refer patients to a specialist. In a study to determine the efficacy of nonsurgically placed intranasal catheters, topical clotrimazole was shown to resolve clinical disease in 65% of dogs after one treatment and in 87% of dogs after two treatments.16 A similar study using topical enilconazole in dogs reported 57% resolution of clinical disease after one treatment and 94% after one to three treatments.17 This study also evaluated the role of extensive rhinoscopic débridement before enilconazole infusion and concluded that it improved patient outcome.

As topical administration of antifungal agents is only appropriate if the cribriform plate is intact, a CT scan is warranted before each treatment.

Systemic therapy. Although oral antifungal medications are expensive and side effects are common, systemic therapy is recommended if there is fungal invasion of extranasal structures. Several azole drugs have been used to treat dogs with sinonasal aspergillosis, but the success rates are moderate at best. One treatment protocol using ketoconazole and surgical débridement was curative in only three of seven dogs, while six of 10 dogs with fungal rhinitis due to either Aspergillus or Penicillium species responded to fluconazole.18,19 One report describes the successful treatment of a dog with sinonasal aspergillosis using itraconazole alone, while others have reported positive responses in dogs given itraconazole after surgical and topical therapy.20,21 Anorexia, vomiting, and hepatotoxicosis have been reported with long-term use of these three antifungal agents in dogs, so monitor serum alanine transaminase activity regularly.1

Prognosis

The prognosis of dogs with sinonasal aspergillosis depends on the extent of extranasal involvement and the response to initial therapy. Most dogs treated with topical antifungals do well, although a series of treatments may be necessary. In some patients with extensive turbinate damage, nasal discharge may persist, and bacterial rhinitis occurs in up to 25% of dogs after successful resolution of the primary fungal disease.1 The response to treatment is indicated by a reduction of clinical signs and is supported by repeat CT examination. The use of serology to assess response to treatment is limited, as antibody titers remain high for up to five years after successful therapy.1

In a recent report of three dogs successfully treated for frontal sinus aspergillosis, sinonasal tumors were diagnosed 13 to 30 months after standard treatment with topical clotrimazole.22 Although it was hypothesized that the infection, inflammatory response, or drug may have been carcinogenic, no causal associations were evident and no conclusions can be made from this small veterinary case series.

In general, dogs without extranasal involvement carry a good prognosis, and recurrence of aspergillosis after successful treatment is rare.

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

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.

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.)

Diagnostic approach

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

Figure 7. A lateral spinal radiograph of a dog with extensive diskospondylitis of the thoracic vertebræ. Severe lysis of numerous vertebral bodies and end plates is evident. (Image courtesy of Texas A&M College of Veterinary Medicine & Biomedical Sciences.)

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).

Ultrasonography may reveal changes in affected organs. Dogs with renal infection may have pyelectasia with hyperechoic debris within the renal pelvis (Figure 9).

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.)

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

Treatment

Supportive therapy is often necessary initially, including fluid therapy and pain relief. Once a diagnosis has been established, initiate systemic antifungal therapy either empirically or guided by the results of fungal culture. Traditional antifungal treatments include amphotericin B and itraconazole (Table 1).1 Amphotericin B is a macrolide polyene drug with a broad spectrum of antifungal activity. It appears to be primarily fungistatic but may be fungicidal against some organisms depending on the drug concentration.25 Marked nephrotoxicosis has been reported in veterinary patients after administration of this agent, although the more expensive lipid-based formulations appear to be less toxic and have improved tissue penetration. Some controversy exists in the human literature about the concurrent administration of amphotericin B and azole drugs, since amphotericin B binds to ergosterol within the fungal cell membrane causing cellular contents to leak, while azole drugs inhibit the synthesis of ergosterol. Theoretically, therefore, the efficacy of amphotericin may be blunted in patients receiving azole therapy.

Prolonged clinical remission has been reported in dogs given oral itraconazole, and it is probably the most commonly administered azole drug in dogs with disseminated aspergillosis.23,26 Although fluconazole would be a less expensive option, we are not aware of any reports of successful management of canine disseminated aspergillosis using this agent. In addition, several studies in the human field suggest poor efficacy of fluconazole for this condition.27,28

Many new azoles have been developed in recent years, including voriconazole (Vfend—Pfizer). Voriconazole appears to be more effective against invasive Aspergillus species in people and is associated with fewer adverse events than amphotericin B.29 Other new azoles, including posaconazole and ravuconazole, have been shown to be efficacious against aspergillosis in vitro but their use in companion animals has not been explored.30

Additional antifungal options include terbinafine and caspofungin. Terbinafine is a squalene epoxidase inhibitor and may work synergistically with azole drugs.25 It is generally well-tolerated by dogs, and positive results have been reported in dogs with Malassezia species dermatitis.31 Caspofungin is the first member of a new class of antifungal drugs called the echinocandins. It prevents fungal cell wall synthesis by inhibiting a glucan synthase and has been used successfully in people with invasive aspergillosis who fail to respond to conventional antifungal medications.25 However, we are unaware of any reports of a positive response after the administration of either agent to dogs with disseminated aspergillosis.

Prognosis

Survival times for dogs with disseminated aspergillosis are variable, but owners should generally be given a guarded prognosis. Dogs with mild disease can have prolonged survival after antifungal drug therapy, although many months of treatment are necessary and relapse may occur if medications are prematurely discontinued. Sadly, more severely compromised dogs often succumb to complications of their infection or are euthanized because of quality of life concerns.

Whitney Nelson, DVM

Audrey K. Cook, BVM&S, MRCVS, DACVIM, DECVIMCA

Department of Small Animal Clinical Sciences

College of Veterinary Medicine & Biomedical Sciences

Texas A&M University

REFERENCES

1. Sharp NJH, Mathews KG. Canine nasal aspergillosis-penicilliosis. In: Greene CE, ed. Infectious diseases of the dog and cat. 3rd ed. Edinburgh, UK: Elsevier Saunders, 2006;613-627.

2. Peeters D, Clercx C. Update on canine sinonasal aspergillosis. Vet Clin North Am Small Anim Pract 2007;37:901-916.

3. Peeters D, Day MJ, Clercx C. An immunohistochemical study of canine nasal aspergillosis. J Comp Pathol 2005;132:283-288.

4. Meler E, Dunn M, Lecuyer M. A retrospective study of canine persistent nasal disease: 80 cases (1998-2003). Can Vet J 2008;49:71-76.

5. Benitah N. Canine nasal aspergillosis. Clin Tech Small Anim Pract 2006;21:82-88.

6. Billen F, Peeters D, Peters IR, et al. Comparison of the value of measurement of serum galactomannan and Aspergillus-specific antibodies in the diagnosis of canine sinonasal aspergillosis. Vet Microbiol 2009;133:358-365.

7. Pomrantz JS, Johnson LR, Nelson RW, et al. Comparison of serologic evaluation via agar gel immunodiffusion and fungal culture of tissue for diagnosis of nasal aspergillosis in dogs. J Am Vet Med Assoc 2007;230:1319-1323.

8. Mennink-Kersten MA, Donnelly JP, Verweij PE. Detection of circulating galactomannan for the diagnosis and management of invasive aspergillosis. Lancet Infect Dis 2004;4:349-357.

9. Peeters D, Peters IR, Helps CR, et al. Whole blood and tissue fungal DNA quantification in the diagnosis of canine sino-nasal aspergillosis. Vet Microbiol 2008;128:194-203.

10. Saunders JH, Clercx C, Snaps FR, et al. Radiographic, magnetic resonance imaging, computed tomographic, and rhinoscopic features of nasal aspergillosis in dogs. J Am Vet Med Assoc 2004;225:1703-1712.

11. Saunders JH, van Bree H. Comparison of radiography and computed tomography for the diagnosis of canine nasal aspergillosis. Vet Radiol Ultrasound 2003;44:414-419.

12. Johnson LR, Drazenovich TL, Herrera MA, et al. Results of rhinoscopy alone or in conjunction with sinuscopy in dogs with aspergillosis: 46 cases (2001-2004). J Am Vet Med Assoc 2006;228:738-742.

13. De Lorenzi D, Bonfanti U, Masserdotti C, et al. Diagnosis of canine nasal aspergillosis by cytological examination: a comparison of four different collection techniques. J Small Anim Pract 2006;47:316-319.

14. Billen F, Clercx C, Le Garérrès, et al. Effect of sampling method and incubation temperature on fungal culture in canine sinonasal aspergillosis. J Small Anim Pract 2009;50(2):67-72.

15. Sharp NJ, Sullivan M, Harvey CE, et al. Treatment of canine nasal aspergillosis with enilconazole. J Vet Intern Med 1993;7:40-43.

16. Mathews KG, Davidson AP, Koblik PD, et al. Comparison of topical administration of clotrimazole through surgically placed versus nonsurgically placed catheters for treatment of nasal aspergillosis in dogs: 60 cases (1990-1996). J Am Vet Med Assoc 1998;213:501-506.

17. Zonderland JL, Stork CK, Saunders JH, et al. Intranasal infusion of enilconazole for treatment of sinonasal aspergillosis in dogs. J Am Vet Med Assoc 2002;221:1421-1425.

18. Sharp NJH, Burrell MH, Sullivan M, et al. Canine nasal aspergillosis: serology and treatment with ketoconazole. J Small Anim Pract 1984;25:149-158.

19. Sharp NJH, Harvey CE, O'Brien JA. Treatment of canine nasal aspergillosis/penicilliosis with fluconazole. J Small Anim Pract 1991;32:513-516.

20. McCarthy TC. Nasal aspergillosis in a Welsh corgi puppy. Vet Med 2002;97:731.

21. Claeys S, Lefebvre JB, Schuller S, et al. Surgical treatment of canine nasal aspergillosis by rhinotomy combined with enilconazole infusion and oral itraconazole. J Small Anim Pract 2006;47:320-324.

22. Greci V, Stefanello D, Di Giancamillo M, et al. Sinonasal tumor in 3 dogs after successful topical treatment for frontal sinus aspergillosis. Can Vet J 2009;50:1191-1194.

23. Schultz RM, Johnson EG, Wisner ER, et al. Clinicopathologic and diagnostic imaging characteristics of systemic aspergillosis in 30 dogs. J Vet Intern Med 2008;22:851-859.

24. Garcia ME, Caballero J, Cruzado M, et al. The value of the determination of anti-Aspergillus IgG in the serodiagnosis of canine aspergillosis: comparison with galactomannan detection. J Vet Med B Infect Dis Vet Public Health 2001;48:743-750.

25. Odds FC, Brown AJ, Gow NA. Antifungal agents: mechanisms of action. Trends Microbiol 2003;11:272-279.

26. Kelly SE, Shaw SE, Clark WT. Long-term survival of four dogs with disseminated Aspergillus terreus infection treated with itraconazole. Aust Vet J 1995;72:311-313.

27. Morgenstern GR, Prentice AG, Prentice HG, et al. A randomized controlled trial of itraconazole versus fluconazole for the prevention of fungal infections in patients with haematological malignancies. U.K. Multicentre Antifungal Prophylaxis Study Group. Br J Haematol 1999;105:901-911.

28. Ullmann AJ, Lipton JH, Vesole DH, et al. Posaconazole or fluconazole for prophylaxis in severe graft-versus-host disease. N Engl J Med 2007;356:335-347.

29. Herbrecht R, Denning DW, Patterson TF, et al. Voriconazole versus amphotericin B for primary therapy of invasive aspergillosis. N Engl J Med 2002;347:408-415.

30. Pfaller MA, Messer SA, Hollis RJ, et al. Antifungal activities of posaconazole, ravuconazole, and voriconazole compared to those of itraconazole and amphotericin B against 239 clinical isolates of Aspergillus spp. and other filamentous fungi: report from SENTRY Antimicrobial Surveillance Program, 2000. Antimicrob Agents Chemother 2002;46:1032-1037.

31. Rosales MS, Marsella R, Kunkle G, et al .Comparison of the clinical efficacy of oral terbinafine and ketoconazole combined with cephalexin in the treatment of Malassezia dermatitis in dogs-a pilot study. Vet Dermatol 2005;16:171-176.