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Veterinary Mycology
Abstract
This book is a comprehensive overview of the fungi that are clinically relevant for animals and humans. It is divided in three major parts: the first part comprises the history of veterinary and medical mycology, general aspects of morphology, growth, nutrition, reproduction and classification of fungi. In the second part, the etiologic agents of cutaneous, subcutaneous and systemic mycoses are described in detail with special emphasis on emerging and uncommon pathogenic fungi. Each chapter consists of a brief history and the morphology, classification, reproduction, susceptibility to disinfectants, natural habitat, distribution, genome, isolation, growth and colony characteristics, antigenic characteristics, virulence factors. The major diseases and their routes of transmission, pathogenesis, immunity, diagnosis and treatment are also covered. The third part focuses on laboratory diagnosis including clinical sample collection, their processing for fungal isolation, special stains for microscopic visualization, culture media composition and a relevant glossary. Each chapter includes color photographs, schematic diagrams and tables for better understanding. For details: http://www.springer.com/life+sciences/microbiology/book/978-81-322-2279-8
Chapters (6)
The term ‘mycology’ was coined by H.S. Berkley (1834) as a study of fungi. Medical or veterinary mycology is the study of medically or veterinary important fungi and fungal diseases in human and animals, respectively. The term ‘mycosis’ (mykes = mushroom) is used to describe the infection of human, animal, birds and plants which is caused by numerous pathogenic fungi. The ‘mycotoxicosis’ describes the diseased condition produced by the ingestion of mycotoxins (intoxication) present in the feed. When the fungi produce the pathogenesis due to in vivo toxin production after entry within the host, it is known as ‘mycetism’.
The fungi are eukaryotic, heterogeneous, unicellular to filamentous, spore bearing, and chemoorganotrophic organisms which lack chlorophyll. The fungi have three major morphological forms, i.e. unicellular yeast, filamentous mould (mold) and yeast-like form (pseudohyphae form). The dimorphic fungi (Blastomyces dermatitidis, Coccidioides immitis, Histoplasma, Sporothrix schenckii) are able to produce both the forms (yeast and mould) depending on the temperature (thermal dimorphism). The yeast form is produced within the body of the host (in vitro at 37 °C) and the mould form is observed either in the environment or in artificial culture medium (at room temperature). The pseudohyphae form is chains of elongated ellipsoidal cells with constriction between them and it is produced by Candida albicans.
The classification of fungi relies mostly on morphological criteria such as the pigmentation, shape of hyphae, presence or absence of septa and types of spores. The taxonomy of mould and yeasts is governed by International Code of Botanical Nomenclature (ICBN). Any new proposal for classification of fungi is published in official journal of International Association for Plant Taxonomy (Taxon) and is discussed in annual meeting before acceptance. The classification of clinically relevant fungi is described in Table 3.1.
The first description of dermatophytosis was recorded by Celsus, a Roman encyclopaedist who described a suppurative infection of scalp (‘porrigo’ or ‘kerion of Celsus’) in De Re Medicina (30 A.D.). Throughout the middle ages, several descriptions of dermatophytosis were produced where it is described as ‘tinea’. The keratin-destroying moths which made circular holes in the woollen garments are known as Tinea. Due to similarity in the structure of circular lesion of dermatophytosis on the smooth skin with the circular hole made by moth, Cassius Felix introduced the term ‘tinea’ to describe the lesions. In 1806, Alibert used the term ‘favus’ to describe the honey-like exudate in some scalp infections. However, the fungal aetiology of tinea was first detected by Robert Remak, a Polish physician who first observed the presence of hyphae in the crusts of favus. This detection is also a landmark in medical history because this is the first description of a microbe causing a human disease. He himself did not publish his work, but he permitted the reference of his observations in a dissertation by Xavier Hube in 1837. Remak gave all the credits of his discovery to his mentor Schoenlein who first published the fungal etiological report of favus in 1839. He observed the infectious nature of the favus by autoinoculation into his own hands and also successfully isolated the fungus later (1945) and named Achorion schoenleinii (Trichophyton schoenleinii) in honour of his mentor. In 1844, Gruby described the etiologic agent of tinea endothrix, later became known as Trichophyton tonsurans. The genus Trichophyton was created and described by Malmsten (1845) with its representative species T. tonsurans. Charles Robin identified T. mentagrophytes in 1847 and T. equinum was identified by Matruchot and Dassonville in 1898. Raymond Jacques Adrien Sabouraud (France) first compiled the description of Trichophyton in his book (Les Teignes) in 1910 which was based on his observation in artificial culture. The sexual state of dermatophyte was described by Nannizzi (1927). Emmons (1934) first reported the classification of dermatophytes based on vegetative structures and conidia. Gentles (1958) established the successful treatment of tinea capitis with griseofulvin.
The collection of proper clinical specimens with sterile instruments and their timely shipment with appropriate arrangements into the laboratory is a crucial matter for isolation and identification of fungi. The correct type of specimen with sufficient quantity is required for proper identification. Table 5.1 describes the types of clinical specimens that can be collected from different body systems and types of fungal infection that can be identified from those specimens. The collection methods of clinical materials and their despatch are mentioned below.
The conventional and modern diagnostic techniques which are used for identification of fungi are discussed below.
... Arthrospores are widely spread by dust particles, even in room without entering pet animal (Frymus et al. 2013). This type of skin disease is an occupational infection of Veterinarians, abattoir and tannery workers, farmers, and pet owners particularly the teenagers who care the infected cat and dog (Samanta 2015). Animal is commonly an asymptomatic carrier of dermatophytes because of the pathogen adaptation to the immune system of the host subsequently; zoophilic species cause severe inflammatory reactions. ...
... The vertical transmission of infection is much more common than the horizontal spread. T. schoenleinii can survive in homes for numerous generations without appropriate cleaning (Samanta 2015). It has been shown that shared wet surfaces (patios, balconies, showers, bathtubs) and shared tools may contribute to the transmission of dermatophytes among family member, as dermatophytes groups can persist on a variety of surfaces for up to 18 months (Jazdarehee et al. 2022). ...
... Branching, septate hyphae can be visualized best in the stratum corneum with a special stain such as periodic acid-Schiff (PAS) with diastase predigestion, Grocott methenamine silver and calcofluor white (CFW) stains (Jartarkar et al. 2022), Although, they may also be seen in Hematoxylin and Eosin stained preparations. The diagnostic sensitivity can be increased with biopsy which is not always possible to conduct especially in human patients suffering with diabetes (Samanta 2015). ...
In the last decade, pulmonary fungal infections such as invasive pulmonary aspergillosis (IPA) have increased in incidence due to the increased number of immunocompromised individuals. This increase is especially problematic when considering mortality rates associated with IPA are upwards of 70%. This high mortality rate is due to, in part, the length of time it takes to diagnose a patient with IPA. When diagnosed early, mortality rates of IPA decrease by as much as 30%. In this review, we discuss current technologies employed in both medical and research laboratories to diagnose IPA, including culture, imaging, polymerase chain reaction, peptide nucleic acid–fluorescence in situ hybridization, enzyme-linked immunosorbent assay, lateral flow assay, and liquid chromatography mass spectrometry. For each technique, we discuss both promising results and potential areas for improvement that would lead to decreased diagnosis time for patients suspected of contracting IPA. Further study into methods that offer increased speed and both analytical and clinical sensitivity to decrease diagnosis time for IPA is warranted.
Dermatophytosis or ringworm in rabbits is a zoonotic disease. Dermatophytes are keratinophilic fungi. Trichophyton mentagrophytes is the main microbiological agent that causes infection in rabbit farms, affecting a wide variety of breeds and causing morbidity that diminishes the performance of animals. The development of dermatophytosis in rabbits is strongly related to risk factors such as animal density and immunosuppression conditions. Rabbits may present with clinical signs such as focal alopecia, erythema, and crusting. Risk factor management and disinfection of the environment to decrease fungal loads are important components in control and prevention. As such, the sanitary measures carried out by the rabbit farmer are of extreme importance for the control of the disease. This chapter highlights the main features of dermatophytosis presence in rabbitries.
Dermatophytosis is a fungal infection that affects humans and animals. In cats, Trichophyton and Microsporum are the main causes. Microsporum canis, a zoonotic dermatophyte, causes infections and is commonly found in domesticated animals. Cats can potentially transmit this pathogen to humans. This review attempts to investigate M. canis cultural, and identification methods, alongside the infection's frequency in felines, the effects of M. canis on human health, and infection prevention. To accurately diagnose M. canis infections, fungal culture remains the "gold standard" approach. A variety of additional techniques, including counting colony forming units (CFUs), analysing fungal elements under a microscope, and examining colony morphology, are used to specifically identify M. canis. Despite M. canis's high worldwide prevalence, this review shows that prevalence varies depending on age, breed, immunity and geographic location. Cats with long coats and young cats also have higher M. canis prevalence. Moreover, asymptomatic, and lesion-free felines can be recognised as carriers of M. canis infection. To assess the prevalence of fungal infections in cats, more surveys and experimental studies are needed to look at the immunological differences and breed-specific traits between local and foreign breeds. Concerns have been raised about the regularity with which veterinarians and doctors inform patients, clients, and one another about the risks of zoonotic diseases and preventive measures. It is therefore possible to propose that to improve public health outcomes, both professions should work to close this gap. Further research with larger surveys may be helpful to identify potential risk factors for M. canis infection in felines and to obtain a more accurate estimation of prevalence.
Background: Mycotoxins naturally occur in foods. Aflatoxins can cause serious health problems in
Chitinolytic bacteria were isolated from guts and shells of the termite Microcerotermes sp. Among the nineteen morphologically different chitinolytic isolates, three isolates with highest extracellular chitinase production ratio (≥ 2.26) were selected. Based on molecular identification of 16S rRNA gene sequences and biochemical characterizations using API test kits and MALDI-TOF MS, these isolates were closely related to Bacillus thuringiensis (Mc_E02) and Paenibacillus species (Mc_E07 and Mc_G06). Isolate Mc_E02 exhibited the highest chitinase specific activity (2.45 U/mg protein) at 96 h of cultivation and the enzyme activity was optimized at pH 7.0 and 45°C. The isolate showed highest and broad-spectrum inhibitory effect against three phytopathogenic fungi (Curvularia lunata, Colletotrichum capsici, and Fusarium oxysporum). Its 36-kDa chitinase exhibited the biomass reduction and mycelium inhibition against all fungi, with highest effects to Curvularia lunata. This research provides novel information about termite chitinolytic bacteria and their effective chitinase, with potential use as biocontrol tool.
Background
Dermatophytes are infectious zoonotic fungal agents that are common in animals worldwide. A new loop‐mediated isothermal amplification (LAMP) method and quantitative (q)PCR can be used for identifying these agents. Both methods have high specificity and sensitivity, and are simple and quick to use.
Hypothesis/Objectives
To develop a LAMP and a rapid multiplex qPCR method for detecting Microsporum canis and Trichophyton mentagrophytes, which are the most common fungal species isolated from cats and dogs.
Material and Methods
Both methods targeted the CHS‐1 gene. Their specificity and sensitivity were tested using 64 M. canis and 44 T. mentagrophytes field strains. The validation of the methods was performed using 250 clinical fungal‐positive hair samples.
Results
The specificity value was 100% for both methods. For LAMP, the sensitivity value was 96.9% for M. canis and 93.2% for T. mentagrophytes. For qPCR, the sensitivity values were 98.4% for M. canis and 97.7% for T. mentagrophytes. Similar specificity and sensitivity results were obtained from the validation study using 250 clinical hair samples. LAMP and multiplex qPCR took 30 and 45 min (respectively) for both targets. The limit of detection (LOD) assays for both targets were 10 and 1 spore/mL for LAMP and multiplex qPCR, respectively.
Conclusion
These findings demonstrate that the LAMP and multiplex qPCR methods targeting CHS‐1 gene developed in this study can be used both for point‐of‐care testing and in the laboratory for detecting M. canis and T. mentagrophytes with high specificity and sensitivity with an internal control.
Dermatophytes are highly infectious fungi that cause superficial infections in keratinized tissues in humans and animals. This group of fungi is defined by their ability to digest keratin and encompasses a wide range of species. Classification of many of these species has recently changed due to genetic analysis, potentially affecting clinical diagnosis and disease management. In this review, we discuss dermatophyte classification including name changes for medically important species, current and potential diagnostic techniques for detecting dermatophytes, and an in-depth review of Microsporum canis, a prevalent zoonotic dermatophyte. Fungal culture is still considered the “gold standard” for diagnosing dermatophytosis; however, modern molecular assays have overcome the main disadvantages of culture, allowing for tandem use with cultures. Further investigation into novel molecular assays for dermatophytosis is critical, especially for high-density populations where rapid diagnosis is essential for outbreak prevention. A frequently encountered dermatophyte in clinical settings is M. canis, which causes dermatophytosis in humans and cats. M. canis is adapting to its primary host (cats) as one of its mating types (MAT1-2) appears to be going extinct, leading to a loss of sexual reproduction. Investigating M. canis strains around the world can help elucidate the evolutionary trajectory of this fungi.
Wild animals are an important component of the ecosystem, and play a major role in it. However, in recent years, there has been an astronomical increase in the incidence of wildlife mycotic diseases leading to wildlife extermination. It is important to note that most of these mycotic diseases are zoonotic, and since there is a lot of attention given to zoonosis of a bacterial or viral origin in recent times, it is important to look into the mycotic diseases which may have zoonotic potential. Previously, the authors expatiated on some major wildlife mycotic diseases. In this review, we shed light on the etiology, epidemiology, diagnosis, pathogenesis, pathogenicity, macroscopic and microscopic pathology, and hematological and serum biochemical findings of dermatophytosis, coccidioidomycosis, blastomycosis, and sporotrichosis, which are very important mycoses of wildlife.
In the past few years, there has been a spurred tripling in the figures of fungal diseases leading to one of the most alarming rates of extinction ever reported in wild species. Some of these fungal diseases are capable of virulent infections and are now considered emerging diseases due to the extremely high number of cases diagnosed with fungal infections in the last few decades. Most of these mycotic diseases in wildlife are zoonotic, and with the emergence and re-emergence of viral and bacterial zoonotic diseases originating from wildlife, which are causing devastating effects on the human population, it is important to pay attention to these wildlife-borne mycotic diseases with zoonotic capabilities. Several diagnostic techniques such as fungal isolation, gross pathology, histopathology, histochemistry, cytology, immunohistochemistry, radiography, CT, and molecular methods such as PCR or ELISA have been invaluable in the diagnosis of wildlife mycoses. The most important data used in the diagnosis of these wildlife mycoses with a zoonotic potential have been re-emphasized. This will have implications for forestalling future epidemics of these potential zoonotic mycotic diseases originating from wildlife. In conclusion, this review will highlight the etiology, epidemiology, diagnosis, pathogenesis, pathogenicity, pathology, and hematological/serum biochemical findings of five important mycoses found in wild animals.