Insight on Surra Disease (Trypanosoma evansi) in Horses

The disease caused by Trypanosoma evansi, commonly known as surra, is one of the most economically significant parasitic diseases affecting animals in Egypt, particularly equines and camels. This study aimed to assess the prevalence of surra by comparing various diagnostic methods, including parasitological examinations, CATT/T. evansi, ELISA, and molecular techniques. Three hundred eighty-three blood samples were collected from horses in Cairo (158 samples) and Giza (180 samples) districts. Microscopic examination of wet smears and Giemsa-stained thin blood films revealed no positive samples for T. evansi (0%). However, 26.33% of the examined samples were positive for T. evansi antibodies using the CATT/T. evansi, with 4.73% showing strong agglutination and 21.59% demonstrating moderate agglutination. Additionally, out of one hundred examined samples using ELISA 16 samples (16%) were positive. A PCR assay targeting the ITS-1 gene successfully identified a specific band (467 bp) in seven samples, indicating the presence of Trypanosoma evansi. Phylogenetic analysis revealed that this strain belongs to T. evansi genotype A, and is closely related to strains found in water buffalo in Thailand. The ITS-PCR sequence of T. evansi isolates from Egyptian horses demonstrated a high similarity, ranging from 94.9% to 99.7% identity, with various Trypanosoma species sequences available in GenBank. Notably, the highest similarity of 99.7% was observed with a strain of T. evansi isolated from camels in Egypt. Furthermore, a high positivity was detected with the CATT/T. evansi assay indicates that this test is effective for the routine screening of surra in horses.