Abstract

We report a case of in utero maternofetal transmission of Cryptococcus gattii with fatal outcomes in a wild porpoise. Cryptococcus neoformans and C. gattii are two environmental, encapsulated yeasts that cause invasive and potentially life-threatening infections in humans and animals.¹ C. neoformans classically causes disease in immunocompromised hosts, while C. gattii is also pathogenic amongst immunocompetent hosts.² Since 1999, C. gattii induced cases of cryptococcosis in humans and terrestrial animals have appeared on southern Vancouver Island (British Columbia, Canada) and nearby surrounding areas.^2,3 Spread beyond Vancouver Island has been documented along the Pacific Northwest (PNW) coast, but the mechanism remains undetermined.⁴ A pregnant dead-stranded harbor porpoise (Phocoena phocoena) was reported on 22 February 2007 on the west side of Whidbey Island, in Puget Sound, Washington State (48.2833 N/ 122.7283 W). The carcass was placed on ice and necropsied on 24 February. Histological tissues were processed by conventional methods. Selected sections were stained with mucicarmine. The 177 cm long adult was in poor body condition based on the reduced blubber layer. Both lungs were exposed, extensively scavenged, firm, nodular and on sectioned surface, exuded clear to slightly opaque gelatinous to mucinous discharge. The mediastinal lymph nodes were grossly enlarged, multinodular and firm with large numbers of yeast visible via microscopy. The uterus was gravid in the right horn with a mid-term fetus. No other gross lesions were identified. Microscopically, the lung lesions correlated with granulomatous to pyogranulomatous infiltrates, often with a myriad of yeast. The 30 cm long male fetus was examined at a different facility from the dam, using separate equipment. The fetus appeared grossly normal externally, and was approximately 5–6 months gestation.⁵ Mediastinal lymph nodes were mildly granulomatous and contained numerous yeasts morphologically consistent with Cryptococcus spp. The lymph nodes were partially replaced with intra and extracellular multilobulated aggregates of 8–20 µm yeasts with pale eosinophilic central regions and a thin refractile wall, peripherally bound by a 5 µm wide non-staining capsule. Special staining revealed a prominent mucicarminophilic capsule consistent with Cryptococcus spp. Fetal infection was likely hematogenous with spread from a primary maternal pulmonary source to the uterus, and subsequently to the placental vasculature and internal fetal tissues. Infection of the fetus by aspiration or ingestion of infected amniotic fluid is also possible. Wild PNW porpoises, being nearshore inhabitants of the waters surrounding Vancouver Island, may come into contact with air containing C. gattii at the air-water interface or ingest the organism while feeding in seawater containing the yeast.⁶ Their proximity to habitat containing Coastal Douglas Fir (Pseudotsuga menziesii) and Western Hemlock (Tsuga heterophylla) may play a role in the epidemiology of C. gattii, as these trees have been associated with cases of C. gattii.⁷ Cryptococcal infection during pregnancy has been reported in humans and horses.^8,9 This fetal case of cryptococcosis may have important human and animal health implications. Further studies should be undertaken to assess possible fetal involvement with confirmed maternal infections when pregnant, and to provide information on risk-reduction and improving diagnosis and treatment.

Acknowledgements

The authors thank Mary Jo Adams, Jill Hein, Caroline Spehar, Corrie Allen, volunteers with the Central Puget Sound Marine Mammal Stranding Network, who collected and assisted with the necropsy, and the volunteers who have responded to cetacean strandings in the Pacific Northwest. Susan Berta and Sandy Dubpernell kindly transferred tissue samples to the diagnostic laboratories. C. gattii culture and molecular typing was conducted by the British Columbia Center for Disease Control, Public Health Microbiology and Reference Laboratory, Vancouver, BC. This study was supported by the John H. Prescott Marine Mammal Rescue Assistance Grant Program (NA06NMF4390144).

References

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