Investigation of the parasite Sarcocystis spp. in rabbit by conventional and molecular methods.

Background: Sarcocystosis is an intracellular protozoan infection that causes mild gastrointestinal signs such as diarrhea and nervous signs such as Seizures, hind-limb weakness, circling behavior, and stargazing in many different hosts that result from contamination of grass and water with feces of final hosts. Aim: To diagnose the infection with Sarcocystis spp. In imported and local rabbits in Mosul City, Iraq. Methods: For the estimation, the incidence of Sarcocystis spp. in rabbits in Mosul, Iraq. Specimens were collected from rabbits across October 2023 and March 2024. All muscle samples were analyzed using classic microscopically examination, enzymatic digestion (pepsin and trypsin), staining with Giemsa, and molecular detecting. Results: Macroscopic and microscopic examination of the infected tissue revealed the presence of tissue cysts containing bradyzoites within the muscles. The overall infection rate was 70.1%. Both male and female are similarly vulnerable to Sarcocystis spp. infection, despite some differences in percentages. 2-4 months old Showed had the highest infection rate (47.5%) while 2 years old infection rate reach to (35%), and 1-1.5-year-olds had the lowest rate (17.5%). Six positive samples for pepsin and trypsin digestion technique were selected for for extraction of DNA and restrained to polymerase chain reaction (PCR) utilizing definite primers for exaggeration of sectional fragment of nucleotide sequence of the small ribosomal RNA gene (18SrRNA). The sequences were registered in National Center for Biotechnology Information (NCBI) and then compared with gene sequence data from NCBI by means of phylogenetic tree analysis, which revealed sequence identity with NCBI-BLAST, Sarcocystis halieti (No. EES1: LC830205), Sarcocystis japonica (No. ESS2: LC830206), Sarcocystis speeri (ESS3 LC830207) and Sarcocystis zamani (ESS4 LC830208), confirming the results with isolates from Norway, Japan, and Australia. Conclusion: Our study indicated that the PCR is the most accurate diagnostic test used to confirm the diagnosis of S. halieti, S. japonica, S. speeri, and S. zamani isolates, revealing genetic diversity and classification. The phylogenetic tree analysis demonstrated similarities between local and registered isolates, indicating potential genetic similarities.