Hepatozoon martis in Italy: first evidence based on histopathological characterization and molecular confirmation in Martes foina

Abstract Background Hepatozoon martis is an apicomplexan parasite infecting mustelids, but its geographical distribution and pathological relevance remain incompletely understood. To date, its presence in Italy has not been documented. This study aimed to investigate the occurrence of H. martis in martens from northern and central Italy using an integrated pathological and molecular approach. Methods Between 2023 and 2025, carcasses of 17 martens ( Martes spp.) collected within wildlife health surveillance programs were examined. Tissue samples were screened for apicomplexan DNA by qPCR, and conventional PCR targeting the 18S rDNA, followed by sequencing and phylogenetic analyses, were applied for species characterization. Histopathological examinations were performed on tissues from freshly deceased animals. Results Eight of 17 martens (47%), 16 identified as Martes foina and one Martes martes , tested positive for Hepatozoon infection. Sequencing confirmed H. martis in multiple tissues, including spleen, heart, lymph nodes, and muscle. Histopathological analysis revealed multifocal granulomatous myocarditis and myositis, with intracellular zoites and type II meronts observed within inflammatory lesions. Phylogenetic analyses of short and long 18S rDNA fragments showed that Italian isolates clustered with H. martis sequences from other European countries, displaying low genetic variability. Hepatozoon DNA was also detected in one Ixodes sp. collected from an infected animal. Conclusions This study provides the first evidence to our knowledge of H. martis infection in Italy and highlights its pathogenic potential in stone martens. The low genetic diversity observed among European isolates suggests widespread circulation and gene flow across regions. Further investigations are required to elucidate transmission pathways, identify competent vectors, and assess the pathological significance of H. martis in wildlife. Graphical Abstract