Dermatophytic pseudomycetoma (DPM) is a rarely reported invasive fungal infection of humans and animals, especially cats. This study aimed to identify dermatophytes, breed associations, and the frequency of extracutaneous (EC) involvement in feline DPM. Electronic records and formalin-fixed paraffin-embedded tissue (FFPET) from 32 suspected DPM cases in 30 cats were retrieved from a diagnostic laboratory between 2018 and 2024. To confirm DPM and molecular identity, DNA was extracted from FFPET for ITS2 sequencing, and immunohistochemistry was performed on PCR-negative cases. All cases were confirmed as DPM. Microsporum canis was the only dermatophyte identified. The sensitivity and specificity of ITS2 sequencing for M. canis identification in FFPET were 22/32 (68.8%) and 21/22 (95.5%), respectively. Exotic (36.7%) and Persian (23.3%) but not British breeds (26.3%) were over-represented compared to feline admissions at an affiliated veterinary hospital (8.5%, p < 0.001; 3%, p < 0.001; 21.6%, p = 0.817, respectively). Five cases (16.7%) had EC lesions; two had intra-abdominal masses; two had oral cavity masses, including one which extended into the cranial vault; and one had superficial cervical lymph node invasion. Exotic and Persian breeds are over-represented for DPM and M. canis is the primary cause. EC lesions of DPM may occur more commonly than previously thought.

Phaeohyphomycosis caused by Exophiala species represents an important disease of concern for farmed and aquarium-housed fish. The objective of this study was to summarize the clinical findings and diagnosis of Exophiala infections in aquarium-housed Cyclopterus lumpus. Clinical records and postmortem pathology reports were reviewed for 15 individuals from 5 public aquaria in the United States and Canada from 2007 to 2015. Fish most commonly presented with cutaneous ulcers and progressive clinical decline despite topical or systemic antifungal therapy. Antemortem fungal culture of cutaneous lesions resulted in colonial growth for 7/12 samples from 8 individuals. Amplification of the internal transcribed spacer region (ITS) of nuclear rDNA identified Exophiala angulospora or Exophiala aquamarina in four samples from three individuals. Postmortem histopathologic findings were consistent with phaeohyphomycosis, with lesions most commonly found in the integument (11/15), gill (9/15), or kidney (9/15) and evidence of fungal angioinvasion and dissemination. DNA extraction and subsequent ITS sequencing from formalin-fixed paraffin-embedded tissues of seven individuals identified E. angulospora, E. aquamarina, or Cyphellophora sp. in four individuals. Lesion description, distribution, and Exophiala spp. identifications were similar to those reported in farmed C. lumpus. Antemortem clinical and diagnostic findings of phaeohyphomycosis attributable to several species of Exophiala provide insight on the progression of Exophiala infections in lumpfish that may contribute to management of the species in public aquaria and under culture conditions.

With the increase in keeping exotic companion mammals as pets, concerns about antimicrobial resistance (AMR) and its impact on animal and human health are growing. Guinea pigs, a popular pet in Hong Kong and globally, have limited studies regarding antimicrobial culture and sensitivity results. We reviewed bacteriologic and antimicrobial sensitivity results from clinically ill pet guinea pigs from 2019 to 2023 using data from the City University Veterinary Diagnostic Laboratory. Of the 234 clinical samples from 22 veterinary clinics in Hong Kong, 134 (57.3%) showed positive bacterial growth, of which 23 (17.2%) showed mixed bacterial growth. In total, 156 bacterial isolates were identified. Gram-positive bacteria (n = 104, 66.7%) were most commonly recovered, representing 25 bacterial species, most commonly Streptococcus spp., Staphylococcus spp., and Corynebacterium spp. The majority of positive samples were from the integument (43.6%) and urinary tract (33.8%). A total of 85.9% of all isolates were resistant to at least one antimicrobial agent, with over 40% of isolates exhibiting resistance to three or more antimicrobial agents, and 27.6% were multidrug resistant (resistant to at least one agent in three or more antimicrobial classes). High resistance rates were observed for penicillin (45.6%), gentamicin (43.7%), doxycycline (42.1%), and azithromycin (36.3%). In contrast, isolates were highly susceptible to ceftazidime (84.1%), chloramphenicol (82.6%), ciprofloxacin (72.7%), and marbofloxacin (72.2%). These findings highlight the high frequency of AMR in this population of clinically ill pet guinea pigs in Hong Kong and the need for informed and judicious antimicrobial use.

This retrospective study analysed pathological findings in tissue biopsies from eight exotic pet mammal species submitted to the CityU Veterinary Diagnostic Laboratory in Hong Kong between January 2019 and December 2024. Tissue biopsies were submitted from 287 rabbits, 161 hamsters, 131 hedgehogs, 64 guinea pigs, 22 chinchillas, 20 rats, seven mice and six ferrets. Across all investigated species, both neoplastic and non-neoplastic lesions were prevalent with species-specific tendencies in affected organ system. Skin and soft tissues, along with the reproductive system, were the most affected organ system in all investigated species. Except for chinchillas, neoplastic lesions outnumbered non-neoplastic lesions in all studied species. Adenocarcinoma (15.2%) mostly of the uterus and mammary gland was the most commonly diagnosed lesion in rabbits followed by trichoblastoma (14.5%). Adenoma (14.6%), mostly of the mammary gland, was the most frequently submitted lesion from hamsters, followed by lymphoma (9.8%). Sarcomas of uncertain differentiation were the most prevalent lesions in hedgehogs (21.4%) and were primarily cutaneous and uterine sarcomas, while cystic endometrial hyperplasia (CEH) ranked second (15.3%). In guinea pigs, CEH (21.5%) was the most commonly identified pathology followed by mammary adenoma (13.8%). The reproductive system accounted for more than half of the lesions diagnosed in chinchillas with CEH and endometritis being the most prevalent lesions, each representing 18.2% of submitted biopsies from chinchillas. Mammary gland fibroadenoma was the most frequent diagnosis in rats (55%) and equal in frequency with adenocarcinoma in mice, each representing 25% of submitted biopsies. Ferrets had seven distinct diagnoses. These findings emphasize the significance of reproductive and integumentary health in exotic pet mammals and reveal species-specific disease patterns critical for diagnosis and preventive care.