Evaluation of risk factors for Cryptococcus gattii infection in dogs and cats

Forest Disturbance and Disease: Exploring the Effects of Tree Harvesting Area on Cryptococcus gattii sensu lato Infection Risk, Vancouver Island, Canada, 1998-2014

BACKGROUND

The disturbance of colonized trees and soil, such as through forestry activities, has been proposed to disperse soil- and tree-inhabiting fungal pathogens. Cryptococcus gattii sensu lato is one such pathogen that was detected on Vancouver Island, British Columbia, Canada, beginning in 1999 and caused human and animal illness.

OBJECTIVES

Our aim was to determine if C. gattii s.l. human case incidence on Vancouver Island was correlated with the intensity of landscape-level tree harvesting occurring near human settlement areas.

METHODS

We created buffers around human settlement areas with radii increments of 2.5km, from 2.5 to 20km, and summed the area of annual tree harvests occurring within each buffer zone. We then performed Spearman rank-order correlation to measure the association between case incidence and annual tree harvest intensity at each radius from 1998 through 2014.

RESULTS

The incidence of C. gattii was positively correlated with tree harvesting intensity only at distances of 7.5km (r=0.66, p=0.004) and 10km (r=0.64, p=0.005) from human settlement areas. As annual tree harvesting area increased between 1999 and 2003, so did annual C. gattii incidence in humans, before both plateaued around 2002 and decreased after 2007.

DISCUSSION

Our findings suggest that tree harvesting plays a role in the spread of C. gattii on Vancouver Island. This may be due to tree cutting or soil disturbance facilitating the aerosolization of spores to increase infection risk. This research also illustrates the contribution that geographic information systems can make to public health research on environmental disturbance and disease outbreaks. https://doi.org/10.1289/EHP12396.

Epizootiology of a Cryptococcus gattii outbreak in porpoises and dolphins from the Salish Sea

Cryptococcus gattii is a fungal pathogen that primarily affects the respiratory and nervous systems of humans and other animals. C. gattii emerged in temperate North America in 1999 as a multispecies outbreak of cryptococcosis in British Columbia (Canada) and Washington State and Oregon (USA), affecting humans, domestic animals, and wildlife. Here we describe the C. gattii epizootic in odontocetes. Cases of C. gattii were identified in 42 odontocetes in Washington and British Columbia between 1997 and 2016. Species affected included harbor porpoises Phocoena phocoena (n = 26), Dall's porpoises Phocoenoides dalli (n = 14), and Pacific white-sided dolphins Lagenorhynchus obliquidens (n = 2). The probable index case was identified in an adult male Dall's porpoise in 1997, 2 yr prior to the initial terrestrial outbreak. The spatiotemporal extent of the C. gattii epizootic was defined, and cases in odontocetes were found to be clustered around terrestrial C. gattii hotspots. Case-control analyses with stranded, uninfected odontocetes revealed that risk factors for infection were species (Dall's porpoises), age class (adult animals), and season (winter). This study suggests that mycoses are an emerging source of mortality for odontocetes, and that outbreaks may be associated with anthropogenic environmental disturbance.

Searching for clues for eighteen years: Deciphering the ecological determinants of Cryptococcus gattii on Vancouver Island, British Columbia

Cryptococcus gattii emerged on Vancouver Island in 1999 for unknown reasons, causing human and animal fatalities and illness. The apparent emergence of this fungus in another temperate area, this time in the Pacific Northwest, suggests the fungus may have expanded its ecological niche. Yet studies that directly examine the potential roles of climatic and land use changes on C. gattii are still lacking. We aim to summarize the existing global literature on the ecology of C. gattii, with particular focus on the gap in knowledge surrounding the potential effects of climatic and land use changes. We systematically reviewed English peer-reviewed literature on the ecological determinants of C. gattii. We included studies published from January 1970 through June 2016 and identified 56 relevant studies for our review. We identified environmental isolations of C. gattii from 18 countries, spanning 72 separate regions across six continents. Fifty-three tree species were associated with C. gattii, spanning 10 climate classifications and 36 terrestrial ecoregions. No studies directly tested the potential effects of climatic changes (including climatic oscillations and global climate change) on C. gattii, while only one study directly assessed those of land use change. To improve model predictions of current and future distributions of C. gattii, more focus is needed on the potential effects of climatic and land use changes to help decrease the public health risk. The apparent emergence of C. gattii in British Columbia is also an opportunity to explore the factors behind emerging infectious diseases in Canada and elsewhere.

Isolation of Cryptococcus gattii VGIII from feline nasal injury

Hereby we communicate the first autochthon isolation of Cryptococcus gattii VGIII in Chile, which was obtained from a nasal injury in a domestic cat in the Valparaíso region in Chile. The strain was identified using morphophysiological tests, MALDI-TOF, and URA5 gene PCR-RFLP analysis.

Skin as a marker of general feline health: Cutaneous manifestations of infectious disease

Practical relevance: Infectious disease in feline patients often presents a diagnostic challenge. This article reviews the most relevant viral, bacterial and protozoal diseases and their cutaneous manifestations. Many of the diseases discussed have overlapping presentations or may mimic more common noninfectious disease processes. The purpose of the article is to reinforce knowledge of common and uncommon infectious diseases, help practitioners identify possible infectious dermatoses, create a comprehensive and prioritized differential list, and provide guidance for the diagnosis of these diseases. A working knowledge of these clinical syndromes is important if what is thought to be a case of a common disease does not respond to conventional management.

AUDIENCE

This review is aimed at veterinarians who treat cats and especially those with an interest in feline dermatology. Tables are included to allow the reader to formulate a concise list of differential diagnoses for clinically similar presentations. The diagnostic approach to a case of ulcerative facial dermatitis is reviewed in a Case Notes quiz. Evidence base: This article includes up-to-date information regarding dermatologic manifestations of less commonly encountered feline cutaneous infectious diseases. Information has been drawn from the published, peer-reviewed literature and the most recent textbook chapters with a particular aim of describing and differentiating clinical lesions and the diagnostic approach to cutaneous disease, especially in unusual cases.

Cryptococcal Maxillary Osteomyelitis and Osteonecrosis in a 18-Month-Old Dog

An 18-month-old neutered male labradoodle was treated with surgical debridement for maxillary osteomyelitis and sequestrum formation. Histopathologic findings of the necrotic bone were consistent with Cryptococcus subspecies, confirmed with latex agglutination serum titer testing. The patient responded to a combination of fluconazole and surgical debridement and was titer negative after 8 months of medical therapy. The patient never exhibited signs of systemic illness which is commonly reported with cryptococcosis. Cryptococcus subspecies infection in dogs in the Pacific Northwest is part of an ongoing outbreak in the region, first reported in 2001, and is associated with specific risk factors. This is the first published case of oral cryptococcosis from primary inoculation.

Cryptococcus gattii infections

Understanding of the taxonomy and phylogeny of Cryptococcus gattii has been advanced by modern molecular techniques. C. gattii probably diverged from Cryptococcus neoformans between 16 million and 160 million years ago, depending on the dating methods applied, and maintains diversity by recombining in nature. South America is the likely source of the virulent C. gattii VGII molecular types that have emerged in North America. C. gattii shares major virulence determinants with C. neoformans, although genomic and transcriptomic studies revealed that despite similar genomes, the VGIIa and VGIIb subtypes employ very different transcriptional circuits and manifest differences in virulence phenotypes. Preliminary evidence suggests that C. gattii VGII causes severe lung disease and death without dissemination, whereas C. neoformans disseminates readily to the central nervous system (CNS) and causes death from meningoencephalitis. Overall, currently available data indicate that the C. gattii VGI, VGII, and VGIII molecular types more commonly affect nonimmunocompromised hosts, in contrast to VGIV. New, rapid, cheap diagnostic tests and imaging modalities are assisting early diagnosis and enabling better outcomes of cerebral cryptococcosis. Complications of CNS infection include increased intracranial pressure, severe neurological sequelae, and development of immune reconstitution syndrome, although the mortality rate is low. C. gattii VGII isolates may exhibit higher fluconazole MICs than other genotypes. Optimal therapeutic regimens are yet to be determined; in most cases, initial therapy with amphotericin B and 5-flucytosine is recommended.

Feline nasal granuloma due to Cryptoccocus gattii type VGII

The aims of this study are to make a more precise identification of the etiologic agent of a nasal granuloma in a cat, to verify the susceptibility to the antifungal drugs: ketoconazole, itraconazole, fluconazole, posaconazole, voriconazole, amphotericin B and the proper treatment. Part of the granuloma's fragment was removed, added to a saline solution and sent to the Laboratory of Mycology. The solution was then seeded in Sabouraud dextrose agar, and the yeast was primarily identified by the traditional methods. The confirmation of the specie Cryptococcus gattii and its molecular type were performed using the PCR-RFLP molecular techniques. The antifungal susceptibility was verified by using the E-test method, and the cat was treated with itraconazole associated with 5-flucytosine. The isolated strain was identified as C. gattii type VGII and was susceptible to all antifungal drugs tested. The treatment with itraconazole associated with 5-flucytosine led to the cure of granulomatous lesions in the feline after 6 months. The characterization and molecular investigation of this microorganism are relevant because they could help us better understand the epidemiology of the infection and to guide us to treat properly the disease.

Strategies for collaboration in the interdisciplinary field of emerging zoonotic diseases

The integration of the veterinary, medical and environmental sciences necessary to predict, prevent or respond to emerging zoonotic diseases requires effective collaboration and exchange of knowledge across these disciplines. There has been no research into how to connect and integrate these professions in the pursuit of a common task. We conducted a literature search looking at the experiences and wisdom resulting from collaborations built in health partnerships, health research knowledge transfer and exchange, business knowledge management and systems design engineering to identify key attributes of successful interdisciplinary (ID) collaboration. This was followed by a workshop with 16 experts experienced in ID collaboration including physicians, veterinarians and biologists from private practice, academia and government agencies. The workshop participants shared their perspectives on the facilitators and barriers to ID collaboration. Our results found that the elements that can support or impede ID collaboration can be categorized as follows: the characteristics of the people, the degree to which the task is a shared goal, the policies, practices and resources of the workplace, how information technology is used and the evaluation of the results. Above all, personal relationships built on trust and respect are needed to best assemble the disciplinary strength of the professions. The challenge of meeting collaborators outside the boundaries of one's discipline or jurisdiction may be met by an independent third party, an ID knowledge broker. The broker would know where the knowledge could be found, would facilitate introductions and would help to build effective ID teams.

Cryptococcus gattii: an emerging fungal pathogen infecting humans and animals

Infectious fungi are among a broad group of microbial pathogens that has and continues to emerge concomitantly due to the global AIDS pandemic as well as an overall increase of patients with compromised immune systems. In addition, many pathogens have been emerging and re-emerging, causing disease in both individuals who have an identifiable immune defect and those who do not. The fungal pathogen Cryptococcus gattii can infect individuals with and without an identifiable immune defect, with a broad geographic range including both endemic areas and emerging outbreak regions. Infections in patients and animals can be severe and often fatal if untreated. We review the molecular epidemiology, population structure, clinical manifestations, and ecological niche of this emerging pathogen.

A decade of experience: Cryptococcus gattii in British Columbia

It has been over a decade since Cryptococcus gattii was first recognized as the causative organism of an outbreak of cryptococcosis on Vancouver Island, British Columbia. A number of novel observations have been associated with the study of this emergent pathogen. A novel genotype of C. gattii, VGIIa was described as the major genotype associated with clinical disease. Minor genotypes, VGIIb and VGI, are also responsible for disease in British Columbians, in both human and animal populations. The clinical major genotype VGIIa and minor genotype VGIIb are identical to C. gattii isolated from the environment of Vancouver Island. There is more heterogeneity in VGI, and a clear association with the environment is not apparent. Between 1999 and 2010, there have been 281 cases of C. gattii cryptococcosis. Risk factors for infection are reported to be age greater than 50 years, history of smoking, corticosteroid use, HIV infection, and history of cancer or chronic lung disease. The major C. gattii genotype VGIIa is as virulent in mice as the model Cryptococcus, H99 C. neoformans, although the outbreak strain produces a less protective inflammatory response in C57BL/6 mice. The minor genotype VGIIb is significantly less virulent in mouse models. Cryptococcus gattii is found associated with native trees and soil on Vancouver Island. Transiently positive isolations have been made from air and water. An ecological niche for this organism is associated within a limited biogeoclimatic zone characterized by daily average winter temperatures above freezing.

Feline cryptococcosis: impact of current research on clinical management

DISEASE SUMMARY: Cryptococcosis, principally caused by Cryptococcus neoformans and Cryptococcus gattii, is the most common systemic mycosis of cats worldwide. Cats may be infected following inhalation of spores from the environment, with the nasal cavity suspected as being the initial site of colonization and subsequent infection. Other sites of infection in cats are the skin, lungs, lymph nodes, central nervous system (CNS), eyes and, occasionally, periarticular connective tissue. Cryptococcosis can be diagnosed using serology (antigen testing), cytologic examination of smears, histopathology or culture. Treatment of localized disease is generally successful using azole antifungal drugs; however, cats with CNS involvement or disseminated disease require additional treatment with amphotericin B, with or without flucytosine. The prognosis is variable, depending on host and pathogen factors. Some cats require long-term (>1 year) treatment or indefinite therapy.

PATIENT GROUP

Cats of any breed, gender and age may be affected. Retroviral status does not appear to be a risk factor for developing cryptococcosis and indoor cats are not protected from disease.

GLOBAL IMPORTANCE

Feline cryptococcosis occurs worldwide, but is most frequently reported in Australia, western Canada and the western United States. Species and molecular type vary in different geographical regions and may affect clinical presentation and antifungal susceptibility patterns.

CLINICAL CHALLENGES

Serologic tests that detect cryptococcal antigen in serum are sensitive and specific, but false negatives can occur in cats with localized disease. Long-term drug therapy can be expensive and has the potential for toxicity. The extent to which the pathogenicity and antifungal susceptibility is affected by molecular type is currently under study.

EVIDENCE BASE

This review draws on recent literature relating to epidemiology, CNS involvement and advanced diagnostic imaging to update clinicians regarding research findings relevant to clinical practice.

Cryptococcosis: update and emergence of Cryptococcus gattii

Cryptococcosis is a fungal disease that occurs throughout the world. Recent reclassification of Cryptococcus species along with a change in the distribution pattern has prompted reevaluation of the organism and the diseases caused by this pathogen. This review highlights the emergence of Cryptococcus gattii as a primary pathogen in North America and summarizes our current understanding of the disease in mammals and birds.

The emergence of Cryptococcus gattii in British Columbia and the Pacific Northwest

An unprecedented emergence of cryptococcal infections in animals and otherwise healthy humans was recognized in 1999 on the east coast of Vancouver Island, British Columbia. Unexpectedly, these infections were caused by Cryptococcus gattii, a species closely related to the AIDS-associated fungal pathogen Cryptococcus neoformans. Human cases have continued over the past 8 years and now total approximately 170 with eight deaths. Extensive environmental sampling, coupled with detailed molecular typing of isolates, revealed areas of permanent and transient colonization with primarily three genotypes of the fungus. C. gattii was found in air, soil, water, and in association with numerous tree species. Importantly, there is solid evidence for human-mediated dispersal of the pathogen, and C. gattii has now been detected in the environment on the mainland of British Columbia and in the Pacific Northwest. Associated animal and human cases are now being reported and further spread of the pathogen may be inevitable.

Cryptococcosis in domestic animals in Western Australia: a retrospective study from 1995-2006

A retrospective study of cryptococcosis in domestic animals residing in Western Australia was conducted over an 11-year-period (from 1995 to 2006) by searching the data base of Murdoch University Veterinary Teaching hospital and the largest private clinical pathology laboratory in Perth. Cryptococcosis was identified in 155 animals: 72 cats, 57 dogs, 20 horses, three alpacas, two ferrets and a sheep. There was no seasonal trend apparent from the dates of diagnosis. Taking into account the commonness of accessions to Murdoch University, cats were five to six times more likely to develop this disease than dogs, and three times more likely than horses, while horses were almost twice as likely as dogs to become infected. Amongst the feline cohort, Ragdoll and Birman breeds were over-represented, while in dogs several pedigree breeds were similarly overrepresented. Dogs and horses tended to develop disease at an early age (one to five years), while cats were presented over a much wider range of ages. In cats and dogs the upper respiratory tract was the most common primary site of infection, while horses and alpacas tended to have lower respiratory involvement. The most striking finding of the study was the high frequency with which C. gattii was identified, with infections attributable to this species comprising 5/9 cats, 11/22 dogs, 9/9 horses and 1/1 alpaca, where appropriate testing was conducted. Preliminary molecular genotyping suggested that most of the C. gattii infections in domestic animals (9/9 cases) were of the VGII genotype. This contrasts the situation on the eastern seaboard of Australia, where disease attributable to C. gattii is less common and mainly due to the VGI genotype. C. gattii therefore appears to be an important cause of cryptococcosis in Western Australia.

Antifungal drug discovery through the study of invertebrate model hosts

There is an urgent need for new antifungal agents that are both effective and non-toxic in the therapy of systemic mycoses. The model nematode Caenorhabditis elegans has been used both to elucidate evolutionarily conserved components of host-pathogen interactions and to screen large chemical libraries for novel antimicrobial compounds. Here we review the use of C. elegans models in drug discovery and discuss caffeic acid phenethyl ester, a novel antifungal agent identified using an in vivo screening system. C. elegans bioassays allow high-throughput screens of chemical libraries in vivo. This whole-animal system may enable the identification of compounds that modulate immune responses or affect fungal virulence factors that are only expressed during infection. In addition, compounds can be simultaneously screened for antifungal efficacy and toxicity, which may overcome one of the main obstacles in current antimicrobial discovery. A pilot screen for antifungal compounds using this novel C. elegans system identified 15 compounds that prolonged survival of nematodes infected with the medically important human pathogen Candida albicans. One of these compounds, caffeic acid phenethyl ester (CAPE), was an effective antifungal agent in a murine model of systemic candidiasis and had in vitro activity against several fungal species. Interestingly, CAPE is a potent immunomodulator in mammals with several distinct mechanisms of action. The identification of CAPE in a C. elegans screen supports the hypothesis that this model can identify compounds with both antifungal and host immunomodulatory activity.

Nasal cryptococcosis in two dogs in New Zealand

CASE HISTORY

Two young, large-breed female dogs were presented with an acute onset of sneezing and nasal discharge. One patient had concurrent epistaxis and facial deformity.

CLINICAL FINDINGS

Decreased airflow was noted through the left nostril in Case 1, while Case 2 showed facial deformity. Nasal radiographs from Case 1 showed a soft tissue opacity in the left nasal cavity and frontal sinus. Rhinoscopy revealed roughened, erythematous nasal turbinates in both patients, and a mass in the left caudal nasal cavity of Case 1. Cryptococcus spp. were demonstrated histopathologically on a nasal biopsy. Tissue culture and serum antigen titres were positive for Cryptococcus spp.

DIAGNOSIS

Chronic rhinitis secondary to Cryptococcus gattii infection in Case 1, and Cryptococcus neoformans infection in Case 2.

CLINICAL RELEVANCE

These are the first reported cases of Cryptococcus spp. rhinitis in dogs in New Zealand.

Cryptococcus gattii with bimorphic colony types in a dog in western Oregon: additional evidence for expansion of the Vancouver Island outbreak

Cryptococcus gattii was isolated from a 1.5-year-old dog with systemic cryptococcosis in Oregon. The dog had no link to Vancouver Island or British Columbia, Canada. Samples from a nasal swab and from a granulomatous mass within the cranial cavity were pooled for culture. Colonies on Sabouraud dextrose agar were mucoid and exhibited bimorphic morphology, melanin-pigmented and unpigmented. Pigmented colonies were encapsulated budding spherical yeast, whereas unpigmented colonies were of unencapsulated ovoid budding yeast. In addition to defective melanin production, the unpigmented colony type exhibited defective mating. Genetic analysis by high-resolution multilocus sequence typing revealed that the 2 isolates are genetically identical at 8 unlinked loci tested and that the 2 isolates are both the VGIIa Vancouver Island major genotype. Findings are consistent with expansion of the Vancouver Island outbreak onto the mainland Pacific Northwest region of the United States.

Cryptococcus gattii: Emergence in Western North America: Exploitation of a Novel Ecological Niche

The relatively uncommon fungal pathogen Cryptococcus gattii recently emerged as a significant cause of cryptococcal disease in human and animals in the Pacific Northwest of North America. Although genetic studies indicated its possible presence in the Pacific Northwest for more than 30 years, C. gattii as an etiological agent was largely unknown in this region prior to 1999. The recent emergence may have been encouraged by changing conditions of climate or land use and/or host susceptibility, and predictive ecological niche modeling indicates a potentially wider spread. C. gattii can survive wide climatic variations and colonize the environment in tropical, subtropical, temperate, and dry climates. Long-term climate changes, such as the significantly elevated global temperature in the last 100 years, influence patterns of disease among plants and animals and create niche microclimates habitable by emerging pathogens. C. gattii may have exploited such a hitherto unrecognized but clement environment in the Pacific Northwest to provide a wider exposure and risk of infection to human and animal populations.

Immune response to fungal infections

The immune mechanisms of defence against fungal infections are numerous, and range from protective mechanisms that were present early in evolution (innate immunity) to sophisticated adaptive mechanisms that are induced specifically during infection and disease (adaptive immunity). The first-line innate mechanism is the presence of physical barriers in the form of skin and mucous membranes, which is complemented by cell membranes, cellular receptors and humoral factors. There has been a debate about the relative contribution of humoral and cellular immunity to host defence against fungal infections. For a long time it was considered that cell-mediated immunity (CMI) was important, but humoral immunity had little or no role. However, it is accepted now that CMI is the main mechanism of defence, but that certain types of antibody response are protective. In general, Th1-type CMI is required for clearance of a fungal infection, while Th2 immunity usually results in susceptibility to infection. Aspergillosis, which is a disease caused by the fungus Aspergillus, has been the subject of many studies, including details of the immune response. Attempts to relate aspergillosis to some form of immunosuppression in animals, as is the case with humans, have not been successful to date. The defence against Aspergillus is based on recognition of the pathogen, a rapidly deployed and highly effective innate effector phase, and a delayed but robust adaptive effector phase. Candida albicans, part of the normal microbial flora associated with mucous surfaces, can be present as congenital candidiasis or as acquired defects of cell-mediated immunity. Resistance to this yeast is associated with Th1 CMI, whereas Th2 immunity is associated with susceptibility to systemic infection. Dermatophytes produce skin alterations in humans and other animals, and the essential role of the CMI response is to destroy the fungi and produce an immunoprotective status against re-infection. The resolution of the disease is associated with a delayed hypersensitive response. There are many effective veterinary vaccines against dermatophytoses. Malassezia pachydermatis is an opportunistic yeast that needs predisposing factors to cause disease, often related to an atopic status in the animal. Two species can be differentiated within the genus Cryptococcus with immunologic consequences: C. neoformans infects predominantly immunocompromised hosts, and C. gattii infects non-immunocompromised hosts. Pneumocystis is a fungus that infects only immunosupressed individuals, inducing a host defence mechanism similar to that induced by other fungal pathogens, such as Aspergillus.

First contemporary case of human infection with Cryptococcus gattii in Puget Sound: evidence for spread of the Vancouver Island outbreak

We report a case of cryptococcosis due to C. gattii which appears to have been acquired in the Puget Sound region, Washington State. Genotyping confirmed identity to the predominant Vancouver Island genotype. This is the first documented case of human disease by the major Vancouver Island emergence strain acquired within the United States.

Cryptococcus gattii dispersal mechanisms, British Columbia, Canada

C. gattii may be spread through soil disturbances, wind, water, distribution of tree and soil byproducts, and human movement.

Recent Cryptococcus gattii infections in humans and animals without travel history to Vancouver Island, as well as environmental isolations of the organism in other areas of the Pacific Northwest, led to an investigation of potential dispersal mechanisms. Longitudinal analysis of C. gattii presence in trees and soil showed patterns of permanent, intermittent, and transient colonization, reflecting C. gattii population dynamics once the pathogen is introduced to a new site. Systematic sampling showed C. gattii was associated with high-traffic locations. In addition, C. gattii was isolated from the wheel wells of vehicles on Vancouver Island and the mainland and on footwear, consistent with anthropogenic dispersal of the organism. Increased levels of airborne C. gattii were detected during forestry and municipal activities such as wood chipping, the byproducts of which are frequently used in park landscaping. C. gattii dispersal by these mechanisms may be a useful model for other emerging pathogens.