Toxoplasma gondii in cetaceans of Brazil: a histopathological and immunohistochemical survey

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.

The Pathology of Cetacean Morbillivirus Infection and Comorbidities in Guiana Dolphins During an Unusual Mortality Event (Brazil, 2017–2018)

“…18,22,23,39,46,61 In cetaceans from Brazil, T. gondii has been described in 3 Guiana dolphins, an Atlantic bottlenose dolphin, a captive killer whale ( Orcinus orca ), and a Bryde’s whale ( Balaenoptera edeni ). 4,14,18,29 Seropositivity has been detected in free-living Amazon river dolphins ( Inia geoffrensis ). 58 Freshwater run-offs with cat feces or soil contaminated with oocysts from coastal terrestrial areas are possible sources of T. gondii in the marine environment.…”

Bacteriological and histopathological findings in cetaceans that stranded in the Philippines from 2017 to 2018

“…A better understanding of the biology, epidemiology, and pathogenesis of tissue-encysting coccidian organisms that parasitize marine mammals is needed to properly assess the risks and burden of protozoal disease in aquatic ecosystems [ 65 – 67 ]. The transmission of these parasites is still poorly understood in marine mammals, although it is known that they are found in striated muscles of intermediate hosts [ 68 – 71 ]. The most likely modes of transmission of these parasites to aquatic animals are via ingestion of water-borne oocysts or sporocysts originating from sewage runoff or through infected prey [ 65 , 66 , 72 – 74 ].…”

Long-Term Consequences of High Polychlorinated Biphenyl Exposure: Projected Decline of Delphinid Populations in a Hotspot for Chemical Pollution

“…In addition to being a hotspot of chemical pollutants that act as an underlying factor leading to an important reduction in immunological function, these regions are also a hotspot for etiological agents . Several viruses, bacteria, and parasites have already been identified in delphinids from the SE region, such as morbillivirus, poxvirus, helminths, and Toxoplasma gondii . − Some of those are strongly associated with declines in population size by interfering in reproductive processes, increase in mortality rates, and/or vulnerability to other diseases . It is important to note that the same pathogens have been recorded affecting dolphins found stranded on the Brazilian coast, including rough-toothed dolphins from S Brazil. , There is increasing alarm regarding emerging infectious diseases in cetaceans, their pathogeny in vulnerable populations, and interaction with immunosuppressant cofactors, such as chemical pollutants .…”