Morphological evidence of gregarines (Phylum: Apicomplexa) in Triatoma dimidiata, Chagas disease vector in Mexico: Rediscovering Machadoella triatomae and a new intestinal gregarine.

The objective of this study was to morphologically characterize the structures suggestive of gregarines found in the feces of Triatoma dimidiata collected in five municipalities in Yucatan, Mexico. Three hundred ninety-six specimens of T. dimidiata collected during 2022 and 2023 were analyzed, of which 8.84 % (n = 35) showed evidence of infection by a gregarine in the intestine and 1.77 % (n = 7) of infection with vermiform gregarine in Malpighian tubules. With microscopic examination, it was possible to obtain measurements and micrographs that allowed the rediscovery of Machadoella triatomae (vermiform gregarine) as well as a potential new gregarine species not previously described in T. dimidiata, which, based on its morphological characteristics, could be another Schizogregarina of the genus Caulleryella (flask-shaped). Additionally, the dissections of some specimens helped correctly identify the site where these gregarines parasitized T. dimidiata. Furthermore, of the three staining techniques used in this study, Lugol's solution and Wright's stain provided greater contrast and were therefore useful for visualizing these microorganisms. Scanning electron microscopy of the new gregarine revealed the three-dimensional shape of merozoites inside and outside a ruptured meront in detail. This study provides morphological evidence of two gregarines (Phylum: Apicomplexa) parasitizing Triatoma dimidiata in multiple regions of Yucatan, Mexico. M. triatomae was isolated in Malpighian tubules, and another gregarine, possibly of the genus Caulleryella, was isolated in the intestine.