A review of lobomycosis and lobomycosis-like skin disease in cetaceans worldwide, with new data from the Gulf of Guayaquil, Ecuador

Abstract

Lobomycosis, also called paracoccidioidomycosis ceti, is a chronic mycotic cutaneous disease affecting odontocetes. Lobomycosis-like disease (LLD) has a clinical presentation consistent with lobomycosis but lacks a histological and molecular diagnosis. We review the literature on lobomycosis aetiology, clinical signs and pathogenesis, species affected and geographic distribution and examine the factors influencing the presence, transmission and prevalence of the disease, to better understand its ecology. In addition, we provide unpublished information on LLD in two common bottlenose dolphin (Tursiops truncatus) communities inhabiting the Gulf of Guayaquil, Ecuador. Lobomycosis and LLD occur in Delphinidae from the Atlantic, Pacific, and Indian Oceans between 33°N and 35°S. Primary risk factors include habitat, sex, age, sociality, and pollution. In dolphins from the Americas and Japan, lobomycosis is caused by Paracoccidioides ceti, family Ajellomycetaceae. The disease is characterized by cutaneous granulomatous lesions that may occur anywhere on the body, grow to large size, and may ulcerate. Histologically, the lesions consist of acanthosis and histiocytic granulomas between the skin and subcutaneous tissues, with inflammatory changes that extend deep into the dermis. Multiple yeast cells with a double refringent layer stained positive using Gomori-Grocott methenamine silver in the dermis of a T. truncatus from Ecuador diagnosed with LLD since 2011, a first record for the Southeast Pacific. Injuries may enable the entry of P. ceti into the dermis while skin contact likely favours transmission, putting males at higher risk than females. Lobomycosis and LLD may have a negative impact on small communities already threatened by anthropogenic factors.