(Figures 1-18 to 1-20)

Cats are definitive hosts for about 11 species of Sarcocystis (Table 5) and intermediate hosts for 1 named species Sarcocystisfelis.

Sarcocystisfelis Dubey, Hamir, Kirkpatrick, Todd, and Rupprecht, 1992

ETYMOLOGY:Sarco (muscle) cystis (cyst) and felis (cat)

HISTORY: Sarcocysts of a Sarcocystis species have been found in a number of felids including domestic cats (Kirkpatrick et al., 1986; Everiit et al., 1987; Fiori and Lowndes, 1988; Hill et al., 1988; Edwards et al., 1988) and wild felids (Kluge, 1967; Greiner et al., 1989, Anderson et al., 1992; Dubey et al., 1992; Dubey and Bwangamoi, 1994). The ultrastructural features of sarcocysts from different feline hosts are indistinguishable and Dubey et al. (1992) gave the name Sarcocystisfelis to the parasite.

HOSTS: The type host is the bobcat (Felisrufus). Other hosts include domestic cats (Felisdomesticus), leopards (Pantherapardus), Florida bobcats (Felisrufusfloridanus), Florida panthers (Felisconcolorcoryi), cougars (Felisconcolorstanleyana), cheetahs (Acinonyxjubatus), and lions (Felisleo).

GEOGRAPHIC DISTRIBUTION: Probably worldwide. Most current reports have been from domestic and wild felids in the United States. The prevalence in domestic cats is unknown. It is apparently common in wild felids. It has been found in 4 of 4 cougars (Greiner et al., 1989), 11 of 14 panthers (Greiner et al., 1989), 4 of 6 bobcats (Dubey et al., 1992), and 30 of 60 Florida bobcats (Anderson et al., 1992). Additionally, it was found in 7 of 10 cheetahs from a captive breeding colony in Oregon (Briggs et al., 1993). The same or a similar parasite has been observed in 2 lions and a leopard from zoos in India (Bhatavdekar and Purohit, 1963, Somvanshi et al., 1987). Dubey and Bwangamoi (1994) described the parasite from a 7 year-old lioness from the Nairobi National Park in Kenya.

PARASITE IDENTIFICATION: Tentative identification is based on observing the sarcocysts in muscle tissue. In muscle squash preparations, sarcocysts are up to 1 cm in length (Greiner et al., 1989). In tissue sections, sarcocysts can approach 2,000 m, are septate, and have regularly spaced, finger-like projections from the tissue cyst wall. No inflammatory response is associated with the tissue cysts (Greiner et al., 1989; Briggs et al., 1993). Definitive identification of S. felis is based on observation of the ultrastructural features of the tissue cyst wall (Dubey et al., 1992). The parasitophorous vacuole membrane (PVM) of he the primary cyst wall is folded into hobnail-like bumps and villar projections that are 0.6-1.2 m long by 0.3-0.4 m wide at uneven distances. The villi lack microtubules. The PVM including villi and hobnail bumps are lined by a 66 nm electron dense thick layer. Ground substance is 0.7-1.0 m thick and is composed of amorphous material and a few electron dense granules. Septa are 0.1-0.2 m thick. Bradyzoites are 7.0-10.0 by 1.5-2.0 m and contain micronemes that are confined to the anterior third od the bradyzoite.

LIFE CYCLE: Sarcocysts are the only life cycle stage that have been observed (Fig. 1-19. Sarcocysts have been observed in heart, tongue, masseter, esophagus, diaphragm and biceps femoris. Precystic stages probably occur in vascular endothelial cells. The definitive host is not known.

CLINICAL PRESENTATION AND PATHOGENESIS: Clinical signs of infection in cats have not been reported.

TREATMENT:Sarcocystisfelis infection does not cause clinical disease in cats and no treatment is needed.


Anderson AJ, Greiner EC, Atkinson CT, Roelke ME. 1992. Sarcocysts in Florida bobcats (Felisrufusfloridanus). J Wildl Dis 28:116-120.

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Briggs et al., 1993

Dubey JP, Speer CA, Fayer R. 1989. Sarcocystosis of Animals and Man. CRC

Press, Boca Raton, Fla. pp. 131-135.

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Figure 1-18.Sarcocystis sp. Sporocyst as it appears when passed in the feces..

Figure 1-19.Sarcocystis felis. Sarcocyst in secton of sleletal muscles from an African lioness. Note villar projections on the cyst wall, septa, and bradyzoites. Hematoxylin and eosin stain. (From: Dubey JP, Bwangamoi G. 1994. Sarcocystis felis (Protozoa: Sarcocystidae) from the African lion (Panthera leo). J Helmithol Soc Wash 61:113-114.

Figure 1-20.Sarcocystis gigantea. Sarcocysts in laryngeal area of a naturally infected ewe. (From: Dubey JP, Leek RG, Fayer R. 1986. Prevalence, transmission, and pathogenicity of Sarcocystisgigantea of sheep. JAVMA 188:151-154.