Toxoplasmosis in Zoo Animals: A Retrospective Pathology Review of 126 Cases

Abstract

Toxoplasma gondii is an extremely successful zoonotic protozoan parasite that has been demonstrated in a wide range of endo- and poikilothermic species. Although infection is widespread amongst domestic animals, overt disease other than abortion in small ruminants is sporadic. This survey evaluates toxoplasmosis in zoo animals based on a systematic review of pathology archive material (n = 33,506 submissions) over a 16-year study period. A total of 126 submissions, deriving from 32 zoos, two educational facilities and two private owners, were included in the study, based on gross lesions, cytological, histological and immunohistological diagnosis of toxoplasmosis. Clinical history, signalment, annual distribution and post-mortem findings were evaluated. A total of 31 species (mammalian 97%/avian 3%) were represented in the study material. Ring-tailed lemurs, slender tailed meerkats, Pallas’ cats, and squirrel monkeys were most affected. An unusual outbreak occurred in Asian small-clawed otters, in which toxoplasmosis has not been reported to date. Clinically, adult animals presented with non-specific symptoms (anorexia, weight loss, lethargy, debilitation), neurological, gastrointestinal or respiratory signs and sudden death. Systemic disease predominated, with a propensity for encephalitis in meerkats and Pallas’ cats and systemic disease involving lymphoid tissues in ring-tailed lemurs. Cases in the UK occurred year-round, with species-specific peaks and increases between August and November. This study reinforces the importance of toxoplasmosis as a significant cause of sporadic and epizootic mortalities in a wide range of zoo animals. Feral cat control is crucial to reduce infection pressure.

Pathology and epidemiology of fatal toxoplasmosis in free-ranging marmosets (Callithrix spp.) from the Brazilian atlantic forest

“…Pathological findings of fatal toxoplasmosis in this study were characterized by a multifocal random necrotizing hepatitis, associated with random lipidosis; interstitial pneumonia rich in alveolar foamy macrophages and fibrin deposition; necrotizing myocarditis; and necrotizing splenitis. These findings are compatible with lesions previously described in cases of NWP lethal infections [1][2][3][4][5][6]14]. Necrotizing lesions are an important feature in T. gondii infection and are caused by the direct rupture of the cells by the tachyzoite forms during replication and exit from the host cell, leading to cell death and necrosis surrounded by an acute inflammatory response [15].…”

“…YF in susceptible NWP is characterized by a midzonal to massive necrotizing hepatitis with coagulative necrosis, scarce inflammatory cells, and apoptotic hepatocytes, which are traditionally called Councilman-Rocha Lima bodies [23][24][25][26]. Animals infected with toxoplasmosis, usually develop a multifocal random necrotizing hepatitis with lytic necrosis, variable inflammatory infiltrate and intralesional zoites, as was observed in our cases [1][2][3][4][5][6]. Importantly, in agreement with histopathological findings, no infected marmoset from this study was co-infected with YFV, based on negative RT-qPCR and IHC testing for YFV performed at the official diagnostic laboratory.…”

“…Domestic and wild cats are the definitive hosts, in which the sexual form of the coccidia develops, generating infective oocysts that are shed in the feces [1]. Neotropical primates (New World Primates; NWP) are highly susceptible to toxoplasmosis [1][2][3]. In captive NWP, toxoplasmosis is characterized by a hyperacute to acute, systemic disease with difficult treatment approach, that evolves quickly to death, being sometimes associated with outbreaks with high lethality [1][2][3][4][5][6][7].…”

“…Neotropical primates (New World Primates; NWP) are highly susceptible to toxoplasmosis [1][2][3]. In captive NWP, toxoplasmosis is characterized by a hyperacute to acute, systemic disease with difficult treatment approach, that evolves quickly to death, being sometimes associated with outbreaks with high lethality [1][2][3][4][5][6][7]. There are differences in susceptibility between NWP species, with capuchins being considered more resistant than other neotropical species [2,6].…”

Seroprevalence and Risk Factors of Human Brucellosis and Toxoplasmosis in Ghazni Province of Afghanistan

“…Brucellosis and toxoplasmosis, both of which have serious health and socioeconomic consequences, are considered neglected zoonotic diseases with a worldwide distribution (Denk et al, 2022;Firoozi Jahantigh et al, 2020;Schurig et al, 2021). Given the importance of ruminants as the primary source of income for the majority of Afghans (Samadi and Hailat, 2019), abortion and stillbirths in ruminants caused by Brucella and Toxoplasma infections could be devastating for the country's farmers and rural communities.…”