Disseminated toxoplasmosis Toxoplasma gondii in a wild Florida manatee Trichechus manatus latirostris and seroprevalence in two wild populations

Abstract

Marine mammals are important indicators for ecosystem health and serve as sentinel species for infectious agents including zoonoses. Histological examination of tissues from a stranded Florida manatee Trichechus manatus latirostris revealed protozoal cysts in the cerebrum and intrahistiocytic tachyzoites in the liver and caudal mesenteric lymph node. Disseminated Toxoplasma gondii infection was confirmed by immunohistochemistry and sequencing of the nuclear ribosomal internal transcribed spacer region of formalin-fixed tissues. The lack of baseline information on Florida manatees' exposure to this pathogen prompted a study into the seroprevalence of T. gondii in 2 separate geographic habitats in Florida, USA, during the winters from 2011−2014. Serum was collected during routine health assessments of 44 apparently healthy manatees from Crystal River (n = 26) on the west central coast of Florida and Brevard County (n = 18) on the east coast of Florida. Serum was screened for detection of T. gondii immunoglobulin G (IgG) antibodies via the modified agglutination test. Two animals from Crystal River from 2011 and 2012 (7.7%) and one animal from Brevard County from 2011 (5.6%) tested positive for T. gondii antibodies. Overall seroprevalence for T. gondii was low in the 2 sampled populations and may reflect a low seroprevalence or animal susceptibility. However, continued monitoring of this pathogen in aquatic ecosystems is warranted due to both possible anthropogenic sources and zoonotic potential.

Investigating seagrass in Toxoplasma gondii transmission in Florida (Trichechus manatus latirostris) and Antillean (T. m. manatus) manatees

“…Our study indicates a lower seroprevalence (0%) of T. gondii in both subspecies than previous reports of 3% (n = 30) in Antillean manatees (Bossart et al 2012) and 6% (n = 44) in Florida manatees (Smith et al 2016). Possible explanations for the variation in seroprevalence reports in these manatee subspecies include: our sample size is too low, titers are below MAT-detectable limits, or the behavior of wild manatees reduces their exposure risk to the infective T. gondii oocysts and the cats that shed them as compared to captive or range-dependent animals.…”

“…Although the MAT has been used extensively in many terrestrial and marine species, it has not been validated in these species and does not determine the presence or absence of disease. Given previous reports of low titers (1:25 and 1:32) in both subspecies of the West Indian manatee (Bossart et al 2012, Smith et al 2016) and in the Amazonian manatee (Delgado et al 2013), it is possible that our study titers were below the detection limit of 1:32. The high seroprevalence in Amazonian manatees often without signs of clinical disease suggests that T. gondii infections in immunocompetent manatees are likely subclinical (Delgado et al 2013).…”

“…The first documented toxoplasmosis mortality in Florida manatees revealed tissue cysts with mild lesions but no tachyzoites present in the brain (Buergelt & Bonde 1983). Most recently, Smith et al (2016) reported disseminated toxoplasmosis with T. gondii tissue cysts and tachyzoites stained by immunohistochemistry and confirmed by PCR in a Florida manatee. That study also reported a 6% seroprevalence in Florida manatees (n = 44).…”

Toxoplasma gondii seroprevalence and genotype diversity in select wildlife species from the southeastern United States

“…Toxoplasma gondii infection occurs in many species of wild mammals and birds, particularly those that are carnivorous or ground dwelling. Clinical toxoplasmosis occurs in a wide variety of US wildlife, including threatened and endangered terrestrial and marine mammals and birds [ 4 , 5 ]. Epidemiology studies of white-tailed deer populations have reported seroprevalence from 30% to 76% in areas including Pennsylvania, Minnesota, Mississippi, New Jersey, Iowa and Ohio [ 6 – 10 ].…”

Infectious and Non-Infectious Diseases in Manatees in Brazil

“…Ambos os estudos ocorreram por meio de sorologia e em nenhum foi relatado óbito ou comprometimentos clínicos por causa do agente. No entanto, durante necropsias de animais da espécie T. manatus de Porto Rico e da Flórida foram identificados casos de presença de cistos protozoários no cérebro e taquizoítos no fígado e linfonodo mesentérico caudal, além de processos inflamatórios ocasionados pelo parasito [25,56]. O levantamento realizado sugere que o T. gondii pode ser uma doença emergente para os peixes-bois no Brasil, mesmo não tendo sido ainda encontrada em achados de necropsia.…”