Toxoplasmosis In Zoos

Toxoplasmosis is a zoo management problem because wild felids can excrete T. gondii oocysts in their feces (Jewell et al., 1972; Miller et al., 1972; Lukesová and Literák, 1998) and because of the occurrence of feral cats in zoos (Gorman et al., 1986).

Oocysts excreted by these felids can make their way into highly susceptible species.

Mammalian species that frequently develop toxoplasmosis in zoos include Australian marsupials (Dobos-Kovacs, 1974; Boorman et al., 1977; Dubey et al., 1988a; Hartley et al., 1990), New World and arborial monkeys (Cunningham et al., 1992; Dietz et al., 1997; Pertz et al., 1997; JuanSalles et al., 1998; Epiphanio et al., 2000), lemurs (Dubey et al., 1985; Spencer et al., 2004), and Pallas cats (Riemann et al., 1974; Dubey et al., 1988b; Kenny et al., 2002; Basso et al., 2005) (Figure 6.2). Lesions in these animals are consistent with acute toxoplasmosis, and are usually most severe in visceral tissues such as the lungs, liver, and spleen.

Sporadic cases of acute toxoplasmosis have been reported in exhibited dik-dik (Madoqua guentheri smithi) (Dubey et al., 2002b), slender-tailed meerkats (Suricata suricatta) (Juan-Salles et al., 1997), and porcupine (Coendou mexicanus) (Morales et al., 1996). A case of abortion due to T. gondii has been reported in a Greenland muskox (Ovibos moshatus wardi) (Crawford et al., 2000).

Abortion and neonatal death have been observed in captive nilgais (Boselaphus tragocamelus). Toxoplasma gondii DNA was demonstrated in the tissues of the nilgais using PCR (Sedlak et al., 2004).

Fatal toxoplasmosis was diagnosed in a captive, adult female saiga antelope (Saiga tatarica). Toxoplasma gondii was detected in the liver, lung, spleen, kidney, and intestine, and confirmed by PCR (Sedlák et al., 2004).

Acute toxoplasmois has been seen in captive Cuvier's gazelle (Gazella cuvieri), slender-horned gazelle (G. leptoceros), dama gazelle (G. dama), and gerenuk (Litocranius walleri) housed in North American zoos (Stover et al., 1990; Junge et al., 1992). These infections are disseminated, and most lesions are in the liver (Figure 6.3), lungs, lymph nodes, adrenal glands, spleen, intestines, and brain.

Outbreaks of toxoplasmosis also occur in avian species exhibited in zoos (Poelma et al., 1972; Hubbard et al., 1986). Toxoplasmosis in canaries has been reported from aviaries worldwide (reviewed by Dubey, 2002). Toxoplasma gondii genotype III was isolated from five of five black-winged lorys (Eos cyanogenia) from an acute toxo-plasmosis outbreak in an aviary in South Carolina (Dubey et al., 2004b).

Management and husbandry programs can be designed to help achieve prevention of toxoplasmo-sis in highly susceptible species in zoos and aviaries. Felids should never be fed fresh, unfrozen meats because of the possibility of contamination with T. gondii tissue cysts. Meat that has been frozen

FIGURE 6.2 Necrosis associated with T. gondii in small intestine. H & E stain.

(A) Necrosis of lamina propria (arrows) of villi 7 days after feeding oocysts to a mouse. The surface epithelium is not affected. Numerous tachyzoites are present in lesions, but are not visible at this magnification. Bar = 100 |im.

(B) Necrosis of the lamina propria cells including blood vessels in a naturally infected Pallas cat. Numerous tachyzoites (small arrows) are present. The surface epithelium (large arrow) was not affected. Bar = 10 |im.

FIGURE 6.2 Necrosis associated with T. gondii in small intestine. H & E stain.

(A) Necrosis of lamina propria (arrows) of villi 7 days after feeding oocysts to a mouse. The surface epithelium is not affected. Numerous tachyzoites are present in lesions, but are not visible at this magnification. Bar = 100 |im.

(B) Necrosis of the lamina propria cells including blood vessels in a naturally infected Pallas cat. Numerous tachyzoites (small arrows) are present. The surface epithelium (large arrow) was not affected. Bar = 10 |im.

FIGURE 6.3 Section of liver from a gazelle with toxoplasmosis showing a central area of hepatitis. Note T. gondii (arrows) in hepatocytes at the periphery of the lesion. H & E stain. Bar = 25 |im.

solid and then thawed can be safely fed, because freezing kills T. gondii tissue cysts (Kotula et al., 1991). Feral cats should be actively controlled in zoos to prevent them from shedding oocysts. Highly susceptible species should not be housed near felids.

Outdoor aviaries are at risk because of oocysts excreted by domestic cats. Aviaries should be designed to exclude cat feces and transport hosts (flies, roaches, etc.) which may bring in T. gondii on or in their bodies.

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