| Summary: | Outbreaks of neurological disease associated with Sarcocystis calchasi have been observed in captive and free-ranging rock pigeons (Columba livia) in Europe and the United States as well as in wild Brandt's cormorants (Phalacrocorax penicillatus) and captive psittacines in California, USA. Experimental and field studies have identified northern goshawks (Accipiter gentilis) and European sparrowhawks (A. nisus) as definitive hosts in Europe while the definitive hosts elsewhere remain unknown. In this study, we aimed to identify the potential definitive host(s) of S. calchasi through molecular analysis of intestinal samples from seven predatory (n=85) and one omnivorous (n=11) bird species in California. In total, apicomplexan-generic 28S rRNA PCR products were obtained and sequenced for 42 raptors. Three of 16 (18.8%) Cooper's hawks (A. cooperii) and two of 26 (5.6%) red-tailed hawks (Buteo jamaicensis) also tested positive for the S. calchasi-specific ITS1 PCR and sequencing of the 28S rRNA PCR product was 100% homologous to S. calchasi. In addition to S. calchasi (5.9%; 5/85), other Sarcocystis spp. detected in raptors included: S. jamaicensis (21.2%; 18/85), S. columbae (8.2%; 7/85), S. turdusi (7.1%; 6/85), and S. halieti (4.7; 4/85%). Infections with closely related S. jamaicensis and S. (Frenkelia) microti (9.4%; 8/85) could not be distinguished for eight raptors. Eumonospora henryae (1.2%; 1/85) was detected in one raptor. Our results indicate for the first time that S. calchasi may have a definitive host range in North America that includes at least two raptors, Cooper's hawks and red-tailed hawks, within the family Accipitridae.
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