Pyrosequencing analysis of cytochrome b (CYTb) gene mutations in Babesia gibsoni: Correlation with drug resistance and treatment efficacy in South Korea.

Abstract

Babesia gibsoni is an intraerythrocytic tick-transmitted protozoan that presents a significant health risk to canine populations worldwide. Canine babesiosis is frequently associated with severe clinical symptoms, particularly hemolytic anemia. The present study aimed to determine the prevalence of mutations in the cytochrome b (CYTb) gene of B. gibsoni using pyrosequencing, and to explore potential correlations between specific mutations and treatment outcomes. The study was conducted at Jeju National University Animal Hospital, where canine patients diagnosed with B. gibsoni infection were evaluated. It is focused on five specific CYTb mutations: M121I, V220I, I303V, P152L, and F258Y. Genetic analysis using pyrosequencing was conducted on samples from infected dogs to identify the presence of these mutations. Various treatment regimens were administered based on clinical judgment, including atovaquone-azithromycin (AA), diminazene aceturate, metronidazole-clindamycin-doxycycline (MCD), and doxycycline-enrofloxacin-metronidazole (DEM). A total of 125 samples were used for mutation analysis, and only nine samples were assessed for the treatment response. The analysis revealed that the M121I mutation was present in 17 % of the B. gibsoni-positive dogs. Significant regional differences were observed in overall mutation prevalence among Jeju, Seoul and Gyeonggi area. Jeju samples showed a significantly higher mutation prevalence than those from PobAniLab. Dog sex, breed and concurrent disease were not significantly associated with the mutation prevalence. Overall, dogs with non-mutated strains tended to respond more favorably to initial treatments, whereas those with mutated strains often required more complex therapeutic approaches. This study supports the value of genetic monitoring in guiding treatment decisions and improving clinical outcomes of canine babesiosis.