Besnoitia darlingi

Besnoitiadarlingi (Brumpt, 1913) Mandour, 1965

ETYMOLOGY:Besnoitia (for Dr. C. Besnoit) darling (for Dr. S. T. Darling)

SYNONYMS:Sarcocystisdarlingi Brumpt, 1913; Besnoitiapanamensis Schneider, 1965; Besnoitiasauriana Garnham, 1966.

GEOGRAPHIC DISTRIBUTION AND PREVALENCE: The prevalence of this parasite in cats is unknown. It has been described from naturally infected opossums (Didelphisviginiana and D. marsupialis) in North and South America and from naturally infected lizards (basilisk lizards Basiliscusbasliscus, Basiliscusvittatus and the borriguero lizard Ameivaameivapraesignis) from South America. Only cyclic transmission between opossums and cats has been documented (Smith and Frenkel, 1977, 1984). Infection is apparently common in opossums in North America ranging from 10 to 60% (Conti-Diaz et al., 1970; Flatt et al. 1971; Smith and Frenkel, 1977).

PARASITE IDENTIFICATION: Oocysts measure 11.8-12.8 by 10.2-12.8 m (mean, 12.3 by 11.9 m). No micropyle or polar granule are present. Two elliptical sporocysts are present. Sporocysts measure 6.2-8.9 by 4.8- 6.2 m (mean, 7.9 by 5.4 m) and do not contain Stieda bodies. Four sporozoites are present in each sporocyst and they measure approximately 5 by 2 m.

LIFE CYCLE: Oocysts are excreted by cats fed tissue cysts but not oocysts (Smith and Frenkel, 1984). The prepatent period is 9 to 14 days (mean, 11.5 days), and the patent period is 3 to 13 days (mean, 8 days). Oocysts are excreted unsporulated in the feces. Unsporulated oocysts sporulate in 2 to 3 days at room temperature (Smith and Frenkel, 1977). The location and structure of developmental stages in the cat intestine is not known. Extraintestinal development apparently does not occur in cats (Smith and Frenkel, 1984). Cats become immune to challenge infection but do not usually develop high antibody titers. Cats fed oocysts do not excrete oocysts, do not develop extraintestinal infections, do not develop measurable antibody titers, and do not become immune to challenge with tissue cysts (Smith and Frenkel, 1984).

It is not known if the organism named B. darlingi in reptiles and B. darlingi in opossums is the same species. Experimentally mice and hamsters can serve as intermediate host for B. darlingi isolated from opossums and cats. The tissue cysts are grossly visible and are characteristic for the genera.

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

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



Conti-Diaz IA, Turner C, Tweeddale DT, Furclow ML. 1970. Besnoitiasis in the opossum (Didelphismarsupialis). J Parasitol 56:457-460.

Flatt RE, Nelson LR, Patton NM. 1971. Besnoitiadarlingi in the opossum (Didelphismarsupialis). Lab Anim Sci 21:106-109.

Smith DD, Frenkel JK. 1977. Besnoitiadarlingi (Protozoa: Toxoplasmatinae) cyclic transmission by cats. J Parasitol 63:1066-1071.

Smith DD, Frenkel JK. 1984. Besnoitiadarlingi (Apicomplexa, Sarcocystidae, Toxoplasmatinae) transmission between opossums and cats. J Protozool 31:584-587.

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