Abstract
Toxoplasmosis is a parasitic disease caused by the protozoan Toxoplasma gondii. In cetaceans, T. gondii infection is a significant cause of morbidity and mortality. Despite the worldwide range and broad cetacean host record of T. gondii infection, there is limited information on toxoplasmosis in cetaceans from the Southern hemisphere. We investigated the occurrence of T. gondii by histopathology and immunohistochemistry in tissue samples of 185 animals comprising 20 different cetacean species from Brazil. Three out of 185 (1.6%) animals presented T. gondii-associated lesions: a captive killer whale Orcinus orca, a free-ranging common bottlenose dolphin Tursiops truncatus and a free-ranging Guiana dolphin Sotalia guianensis. The main lesions observed in these animals were necrotizing hepatitis, adrenalitis and lymphadenitis associated with protozoal cysts or extracellular tachyzoites presenting immunolabeling with anti-T. gondii antibodies. This study widens the spectrum of species and the geographic range of this agent in Brazil, and provides the first reports of T. gondii infection in a captive killer whale and in a free-ranging common bottlenose dolphin in South America.
Highlights
Toxoplasma gondii is a zoonotic intracellular coccidian protozoan of the phylum Apicomplexa (DUBEY, 2008)
Three of 185 (1.6%) animals were IHC-positive for T. gondii-: a captive killer whale, a free-ranging common bottlenose dolphin, and a free-ranging Guiana dolphin
Despite the widespread geographical range of T. gondii infection, in Brazil, the current knowledge regarding cetacean toxoplasmosis is limited to few species and studies (BANDOLI & OLIVEIRA, 1977; SANTOS et al, 2011; GONZALES-VIERA et al, 2013)
Summary
Toxoplasma gondii is a zoonotic intracellular coccidian protozoan of the phylum Apicomplexa (DUBEY, 2008). The exposure and infection by this protozoan has been detected through serological, pathological and molecular techniques in a wide variety of captive and free-ranging cetaceans worldwide (INSKEEP et al, 1990; OMATA et al, 2006; MAZZARIOL et al, 2012; GONZALES-VIERA et al, 2013; IQBAL et al, 2018). Most of these studies have covered individual cases or small groups of cetaceans (DI GUARDO et al, 2010; GONZALES-VIERA et al, 2013). Toxoplasmosis is a significant cause of morbidity and may lead to stranding and death, and is considered one of the most important emerging diseases in cetaceans worldwide (VAN BRESSEM et al, 2009; DI GUARDO et al, 2010; GONZALES-VIERA et al, 2013; BIGAL et al, 2018)
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