Sarcocystis in horses from Rio Grande do Sul, Brazil: Molecular identification of Sarcocystis bertrami and Sarcocystis neurona in muscle tissues.

The study investigates the prevalence of two species of protozoan parasites, Sarcocystis bertrami and Sarcocystis neurona, in muscle tissues of horses in Rio Grande do Sul, Brazil, and reveals a high rate of detection that is considered alarming, especially given the risk of zoonotic transmission through consumption of infected horse meat.

Research Methodology

• The research examined 108 muscle samples from 24 horses that had been necropsied at the Veterinary Pathology Laboratory of the Federal University of Santa Maria.
• The animals were tested for the presence of sarcocysts, a type of cyst formed by Sarcocystis species in the striated muscles of their intermediate hosts.
• The tests involved direct examination of the samples, during which microscopic tissue cysts were found in the tongue and esophagus samples of two horses.
• Extractions were conducted on both the cysts and other tissues that did not reveal any visible sarcocysts under direct examination.

DNA Extraction and Analysis

• Extracted DNA from the tissue samples underwent Nested-PCR (Polymerase Chain Reaction) using Tg18s primers. This technique allows the detection of even small amounts of Sarcocystis DNA.
• The resulting amplified DNA products were examined with Restriction Fragment Length Polymorphism (RFLP) method using DdeI and HpaII enzymes.
• Results showed that DNA from Sarcocystis spp. was amplified in tissue samples from 91.7% (22 out of 24) of the horses, and 67.6% (73 out of 108) of the overall samples tested positive in the Nested-PCR reaction.
• Cysts, identified through nucleotide sequencing, were determined to be S. bertrami. In addition, S. neurona was identified in some samples with instances of co-infection detected in some cases.

Significance of the Findings

• The tissues with the highest detection frequency for Sarcocystis spp. were the diaphragm, gluteal muscle, and esophagus.
• The high detection rate is a concern due to the protozoan’s circulation, particularly that of S. bertrami, a zoonotic species.
• The S. bertrami was found in all tissues commonly exported for human consumption which raises public health concerns given its zoonotic potential.