Equine alveolar echinococcosis: a focus on epidemiology, clinical and pathological features, and diagnostics

Here, we review equine alveolar echinococcosis (AE), focusing on its epidemiology, clinical and pathological features, and diagnostic challenges, through comparisons with AE in other host species. AE is a zoonotic disease caused by the larval form of the Echinococcus multilocularis tapeworm. Horses are considered dead-end hosts, in which AE infection can be detected at slaughter, highlighting their potential as sentinel animals in endemic areas. Equine AE is typically asymptomatic and is generally only found incidentally during meat inspection or necropsy. Standard diagnosis involves histopathology and conventional polymerase chain reaction (PCR) testing. Epidemiological surveys in Japan, Poland, and Canada have reported larval E. multilocularis detection rates ranging from 1.5-18.8%, where infections manifest as macroscopic grayish-white solid liver nodules in slaughtered horses. Molecular phylogenetic analysis targeting the mitochondrial cytochrome b(cob) gene has revealed that parasites isolated from horses in Japan and Canada belong to distinct haplogroups, indicating utility for elucidating the geographical genetic characteristics of larval E. multilocularis infection in horses. Isothermal amplification techniques such as loop-mediated isothermal amplification (LAMP) and recombinase polymerase amplification (RPA) have demonstrated equivalent or superior sensitivity and specificity for detecting equine AE and may represent novel rapid genetic diagnostic tools as alternatives to PCR testing for rapid gene-based detection. These techniques will contribute to early detection of AE, especially in locations where specialized laboratory equipment is limited (e.g., abattoirs). Continued research on equine AE will thus greatly contribute to elucidating the environmental distribution of E. multilocularis and supporting the control of zoonotic disease.