Molecular characterization of Sarcocystis spp. from opossums (Didelphis spp.) and serological detection of anti-Sarcocystis spp. antibodies in horses from Southeastern and Midwestern Brazil

Author(s)

Mariele De Santi

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2023-03-23.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2023-02-24
• Advisor: Rosangela Zacarias Machado; Karin Werther

Abstract

Opossums (Didelphis spp.) are definitive hosts of Sarcocystis neurona, Sarcocystis speeri, Sarcocystis lindsayi and Sarcocystis falcatula. In Brazil, several studies have demonstrated a high frequency of Sarcocystis falcatula-like in sporocysts derived from opossums, and high genetic diversity has been observed in surface antigen-encoding genes (SAGs). In this study, genetic diversity of Sarcocystis spp. derived from Didelphis albiventris and Didelphis aurita from the cities of Campo Grande and São Paulo, was accessed by sequencing SAG2, SAG3, SAG4, the first internal transcribed spacer (ITS-1) and cytochrome c oxidase subunit I (cox1). Additionally, indirect fluorescent antibody test (IFAT) was used to detect IgG antibodies against Sarcocystis falcatula-like (Dal-CG23) and S. neurona (SN138) in equine sera from 342 horses sampled in the same regions. Molecular identification was performed for 16 DNA samples obtained from sporocyst or culture-derived merozoites. The ITS-1, cox1, and SAG3 fragments were cloned, whereas SAG2 and SAG4 were sequenced directly from PCR products. Twenty-seven allele variants were found for ITS-1, all phylogenetically related to S. falcatula-like previously described in birds and/or opossums in Brazil. Sarcocystis sp. phylogenetically related to Sarcocystis rileyi was evidenced by cox1 in three opossums. Twenty-one new SAG alelles were described, four in SAG2 (n=4), 13 in SAG3 (n=13) and four in SAG4 (n=7). On IFAT using 1:25 cutoff, IgG antibodies against S. falcatula-like were detected in 177/342 samples (51.75%), whereas IgG antibodies against S. neurona were detected in 239/342 samples (69.88%). IgG antibodies against both isolates were detected in 132 samples (38,59%). No reactivity was observed in 16.95% (58/342) horses. The high seroprevalence observed here may be related to the lower cutoff, and the presence of opossums infected with Sarcocystis falcatula-like and Sarcocystis spp. in the regions where the horses were sampled. Owing to the similarity among antigens targeted in immunoassays, reports on S. neurona-seropositive horses in Brazil might also derived from exposure of horses to other Sarcocystis species. The role of other Sarcocystis species in causing neurological diseases in horses in Brazil remains unclear. (AU)

• FAPESP's process: 19/08294-0 - Detection and molecular characterization of Sarcocystis spp. in Marsupials (Didelphis spp.) from Campo Grande, MS e São Paulo, SP, Brazil
• Grantee: Mariele de Santi
• Support Opportunities: Scholarships in Brazil - Doctorate