Sarcocystis sp. parasites in the Mexican Great-tailed Grackle (Quiscalus mexicanus), Bronzed Cowbird (Molothrus aeneus), and Stripe-headed Sparrow (Aimophila ruficauda)

Abstract

The objective of this study was to describe the morphological and ultraestructural characteristics, the polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) results, the sequences and the phylogenetic analysis of a specific fragment of internal transcribed spacer 1 (ITS-1), amplified using the 25/396 primers, of the Sarcocystis sp. parasites identified in the muscles of wild great-tailed grackles, bronzed cowbirds, and stripe-headed sparrows in Mexico. Fifteen birds with sarcocystosis in their skeletal muscles were studied: 7 great-tailed grackles (Quiscalus mexicanus), 6 bronzed cowbirds (Molothrus aeneus), and 2 stripe-headed sparrows (Aimophila ruficauda). Histopathological analysis revealed thin-walled mature parasite cysts. Ultrastructurally, the cyst wall consisted of a granular layer with villar protrusions and numerous microtubules. The bradyzoites measured 4.1 × 1.6 µm, and micronemes appeared in the anterior third of the conoid. For molecular identification, PCR-RFLP was performed using sequences of a specific fragment of internal transcribed spacer 1 (ITS-1) using the primers 25/396 and Hinf I. Hind III did not cut this fragment. The sequencing results indicated a 100% similarity among the Sarcocystis parasites from the three bird species, and a BLAST search revealed 96% sequence similarity with S. neurona. The phylogenetic analysis shows that the sequences studied are topologically distant to those sequences reported for S. neurona in the United States and in South America and are not related to any group previously reported. Although our morphological and molecular analysis data provide strong evidence that S. neurona uses these bird species as intermediate hosts, future molecular studies with additional DNA fragments, combined with biological studies, will ultimately allow us to convincingly identify these parasites. This is the first report of a Sarcocystis sp. parasite in wild birds in Mexico that may be S. neurona.