History
A 3-year-old castrated male American Cocker Spaniel was evaluated at the North Carolina State University Veterinary Health Complex Small Animal Emergency Service because of a sudden onset of signs of pain. The dog had a 2-month history of diarrhea, which began as diarrhea of small bowel origin and progressed after 1.5 months to diarrhea of large bowel origin, and a 1-week history of decreased appetite.
Gross and Clinicopathologic Findings
Findings on the initial physical examination were unremarkable except for hyperemia in both eyes and mild hind limb neurologic deficits. Initial CBC findings included mild normocytic normochromic anemia with slight polychromasia noted on the blood smear review, mild leukocytosis characterized by mild neutrophilia with a slight regenerative left shift and moderate monocytosis, and mild thrombocytosis (Table 1). A reticulocyte count was not performed. Serum biochemical panels were performed at the initial evaluation and at intervals over the next 2 weeks, and the consistent findings included hypoalbuminemia and high-normal to mildly high phosphorus concentration. Abdominal ultrasonography revealed multiple eccentric and concentric intestinal masses effacing the wall of the descending colon, transverse colon, and multiple jejunal segments. The largest jejunal mass measured 5 × 1.4 cm. Ultrasound-guided fine-needle aspirates of a small intestinal mass were obtained and submitted for cytologic evaluation.
Abnormal clinicopathologic findings identified in a 3-year-old dog that had a sudden onset of signs of pain, a 2-month history of diarrhea (diarrhea of small bowel origin that progressed after 0.5 months to diarrhea of large bowel origin), and a 1-week history of decreased appetite.
| Diagnostic test | Variable | Test result | Reference interval |
|---|---|---|---|
| Initial CBC | RBC count (× 106 RBCs/μL) | 5.19 | 5.7–8.01 |
| Hemoglobin (g/dL) | 12.5 | 13.8–20.3 | |
| Hct (%) | 37.7 | 39.2–55.9 | |
| Mean cell volume (fL) | 72.7 | 61.8–75.1 | |
| Mean corpuscular hemoglobin concentration (g/dL) | 33.2 | 30.8–35.4 | |
| WBC count (× 103 WBCs/μL) | 16.31 | 4.39–11.61 | |
| Neutrophil count (× 103 cells/μL) | 10.438 | 2.841–9.112 | |
| Band neutrophil count (× 103 cells/μL) | 0.163 | 0 | |
| Monocyte count (× 103 cells/μL) | 2.936 | 0.075–0.85 | |
| Platelet count (× 103 platelets/μL) | 599 | 190–468 | |
| Serum biochemical panels performed at the initial evaluation and at intervals over the next 2 wk | Range of albumin concentrations (g/dL) | 2.1–2.6 | 3–3.9 |
| Range of phosphorus concentrations (mg/dL) | 5.6–6.6 | 2.5–5.6 |
Formulate differential diagnoses from the history, clinical findings, and Table 1—then turn the page →
Cytologic Findings
The fine-needle aspirate samples of a small intestinal mass were examined microscopically. The preparations were of adequate cellularity with scattered clumps of epithelioid macrophages (Figure 1). Within these clumps were many extracellular, round yeast organisms that varied in size from approximately 5 μm up to 15 to 20 μm. After Wright-Giemsa staining, the organisms appeared pale blue to pink, often had a prominent folded region of the cell wall, and were surrounded by a variably sized (scant to moderate) clear-staining capsule. Occasional narrow-based budding was also observed.
Photomicrograph of a fine-needle aspirate sample obtained from a small intestinal mass in a 3-year-old dog that was evaluated because of a 2-month history of diarrhea (diarrhea of small bowel origin that progressed after 0.5 months to diarrhea of large bowel origin) and a 1-week history of decreased appetite. Scattered clumps of epithelioid macrophages and many extracellular round yeast organisms (approx 5 to 20 μm in diameter) that have a variably sized clear-staining capsule and occasional narrow-based budding are visible. Wright-Giemsa stain; bar = 20 μm. Inset—Cryptococcus organism undergoing narrow-based budding. Wright-Giemsa stain; bar = 10 μm.
Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.893
Cytologic Diagnosis and Case Summary
Cytologic diagnosis and case summary: granulomatous inflammation with intralesional yeast organisms consistent with a Cryptococcus sp in a dog.
Comments
Cryptococcosis is a fungal disease principally caused by Cryptococcus neoformans or Cryptococcus gattii.1,2 Cryptococcus neoformans and C gattii differ biochemically, genetically, ecologically, and epidemiologically. Cryptococcus neoformans has a worldwide distribution and has been strongly associated with weathered bird (especially pigeon) guano and decaying plant matter. Cryptococcus gattii has a strong association with eucalyptus trees and was initially considered to be restricted to tropical or subtropical regions in Australia, South America, southeast Asia, parts of Africa, and 1 site in California, but there is an increased concentration within the Pacific Northwest of North America.1,3 Specific identification of the infecting species of Cryptococcus was not pursued in the case described in this report; however, given the dog's lack of travel history and the region of the country in which it lived, it seems likely that the dog was infected with C neoformans.
The pathogenesis of cryptococcosis is dependent on the amount of the inoculum, the virulence of the cryptococcal strain, and the status of host defense. The route of infection is unproven, but in most cases, the likely route is via inhalation. The means of infection in the dog of the present report was unknown but, given the distribution of the lesions, may have been ingestion of the infective stage of the yeast.
Regardless of the infecting Cryptococcus sp, clinical signs of cryptococcosis are similar, but C gattii appears more virulent and has a greater propensity to infect the CNS.1 In cats and dogs, the nasal cavity is thought to be the primary site of infection with Cryptococcus spp.4 In dogs, neurologic signs, often accompanied by malaise, are common. The dog of the present report had gastrointestinal tract signs and a sudden onset of signs of pain, which are unusual. In general, there are more reports of gastrointestinal tract lesions in dogs than in cats1; however, there are few reports5,6 describing gastrointestinal tract signs as the primary clinical signs of cryptococcosis in dogs.
The diagnosis of cryptococcosis can be made by identification of the organism in cytologic or histologic preparations. Mayer's stain can be used to stain the capsule rose-red, causing the organisms to appear pink against a blue background when examined microscopically. Other, nonspecific stains such as periodic acid–Schiff, methenamine silver, or Fontana-Masson stain can also be used to detect the yeast but do not specifically stain the capsule. Although a PCR assay could be used as a sensitive and specific means of diagnosis, it is not considered clinically useful as a routine test.4 Latex agglutination assays can detect cryptococcal capsular antigen of all known serotypes in serum, urine, or CSF samples and are being increasingly used in dogs and cats.7 Even though safe culture of cryptococcal organisms is easy to accomplish, the fruiting stage of Cryptococcus spp does pose a risk of transmission to laboratory personnel.1 For infected dogs, abnormal results of CBCs and serum biochemical analyses are nonspecific. Mild nonregenerative anemia, lymphopenia, and monocytosis may be observed. Occasionally, hyperglobulinemia with polyclonal gammopathy and low albumin-to-globulin concentration ratio may be noted. In the present case, CBC findings were consistent with anemia of inflammatory disease, an inflammatory leukogram, and reactive thrombocytosis. Differential diagnoses included intestinal granuloma or neoplasia. Hypoalbuminemia was consistent with gastrointestinal losses and possibly renal losses, whereas the abnormal phosphorus concentration may reflect renal phosphorus retention or possible underlying renal disease. Further evaluation of the dog's renal system was not performed.
The prognosis for dogs and cats with cryptococcosis is variable, but more likely to be good if treatment begins early in the course of infection. The reported success rates for treatment range from 20% to 75%.4 Treatment is required for months to years and, even when continued for more than a year, does not preclude relapse, reinfection, or development of subclinical colonization by the yeast in the nasal cavity.1 When feasible, surgical excision of large aggregates of infected tissues before or shortly after starting medical treatment is recommended. Five drugs are commonly used to treat cryptococcosis in dogs and cats: amphotericin B, flucytosine, fluconazole, itraconazole, and ketoconazole. Also, terbinafine was recently reported to be effective in a dog that underwent 2 surgical procedures to remove affected lymph nodes and areas of intestine and did not respond to treatment with amphotericin B and fluconazole.5 In the case described in the present report, the dog received IV amphotericin B treatments and oral fluconazole treatment following diagnosis.
Two weeks after initial evaluation, the dog had an acute vestibular event after receiving an amphotericin B treatment and died of cardiac arrest; the owner consented to a necropsy. On gross examination, a 6-cm section of the colonic wall was transmurally and circumferentially expanded up to 2 cm by a cellular infiltrate (Figure 2). Similar, smaller lesions were identified in 4 other locations in the jejunum. Multifocally throughout the mesentery, peripancreatic fat and periportal region lymph nodes were enlarged by edema, hemorrhage, and cellular infiltrate. Bilateral retinal detachment was also noted.
Photograph of a cut portion of the colon from the dog in Figure 1. Notice that the colonic wall is transmurally expanded by a cellular infiltrate.
Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.893
Histologic examination of portions of affected intestinal wall revealed multifocal, transmural, and segmental to circumferential effacement of the intestinal wall by coalescing granulomatous lesions with central areas of necrosis and numerous extracellular and intrahistiocytic round to crescentic, nonstaining yeast with a 5- to 10-μm clear capsule (Figure 3). Multiple layers of epithelioid macrophages surrounded the necrotic cores and were, in turn, surrounded by numerous fibroblasts. Granulomas extended transmurally and were multifocally present within the mesenteric fat. Similar findings were seen in the brain, meninges, mesenteric lymph nodes, pancreas, adrenal glands, and eyes, thereby confirming a final morphologic diagnosis of multifocal to coalescing granulomas with intralesional cryptococcal organisms.
Photomicrograph of a section of the affected colon in Figure 2. The intestinal wall is expanded and infiltrated by granulomatous inflammation with areas of necrosis and numerous extracellular round to crescentic, nonstaining yeast with a 5- to 10-μm clear capsule. H&E stain; bar = 10 μm. Inset—Cryptococcus organism undergoing narrow-based budding. H&E stain; bar = 20 μm.
Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.893
References
1. Lester SJ, Malik R & Barlett KH, et al. Cryptococcosis: update and emergence of Cryptococcus gattii. Vet Clin Pathol 2011; 40: 4–17.
2. Trivedi SR, Malik R & Meyer W, et al. Feline cryptococcosis: impact of current research on clinical management. J Feline Med Surg 2011; 13: 163–172.
3. Lester SJ, Kowalewich NJ & Bartlett KH, et al. Clinicopathologic features of an unusual outbreak of cryptococcosis in dogs, cats, ferrets, and a bird: 38 cases (January to July 2003). J Am Vet Med Assoc 2004; 225: 1716–1722.
4. Skyes JE & Malik R. Cryptococcosis. In: Greene CE, ed. Infectious diseases of the dog and cat. 4th ed. St Louis: Elsevier Inc, 2012;621–634.
5. Olsen GL, Deiz KL & Flaherty HA, et al. Use of terbinafine in the treatment protocol of intestinal Cryptococcus neoformans in a dog. J Am Anim Hosp Assoc 2012; 48: 216–220.
6. Malik R, Hunt GB & Bellenger CR, et al. Intra-abdominal cryptococcosis in two dogs. J Small Anim Pract 1999; 40: 387–391.
7. Trivedi SR, Sykes JE & Cannon MS, et al. Clinical features and epidemiology of cryptococcosis in cats and dogs in California: 93 cases (1988–2010). J Am Vet Med Assoc 2011; 239: 357–369.
