First Molecular Evidence and Phylogeny of <i>Hepatozoon</i> sp. and <i>Theileria</i> sp. in Saudi Rodents

Rodents are among the most abundant and ecologically diverse mammals, playing key roles in terrestrial ecosystems and often serving as reservoirs for various zoonotic and wildlife pathogens. Among these are protozoan parasites of the genera <i>Hepatozoon</i> and <i>Theileria</i>, which are known to infect a wide range of domestic and wild animals worldwide. However, little is known about the diversity and phylogenetic relationships of these hemoprotozoans in rodent hosts, particularly in the Arabian Peninsula. The aim of this study was to investigate the presence and genetic diversity of <i>Hepatozoon</i> sp. and <i>Theileria</i> sp. in rodents from different regions of Saudi Arabia and to determine potential reservoir species. A total of 111 rodents were captured and identified by molecular analysis of the mitochondrial <i>16S</i> rRNA gene. Screening for parasites was performed using PCR amplification of the <i>18S</i> rRNA gene, followed by sequencing, haplotype analysis, and phylogenetic reconstruction using both maximum likelihood and Bayesian inference methods. Our results represent the first molecular detection of <i>Hepatozoon</i> sp. in <i>Arvicanthis niloticus</i> (31.3%), <i>Gerbillus cheesmani</i> (26.5%), <i>G. nanus</i> (28.5%), and <i>Rattus rattus</i> (32.0%) and of <i>Theileria</i> sp. in <i>G. nanus</i> (21.5%) and <i>R. rattus</i> (24.0%) in Saudi Arabia. Haplotype network analysis revealed seven distinct <i>Hepatozoon</i> haplotypes forming a star-like cluster, suggesting host specificity. One divergent haplotype (Hap_2), 19 mutation steps apart, may represent a novel lineage. Phylogenetic analyses grouped Saudi <i>Hepatozoon</i> sequences with those from reptiles and rodents, forming a clade distinct from sequences isolated from felids and canids. In contrast, <i>Theileria</i> sequences showed low diversity, clustering with a single widespread haplotype found in rodents and ruminants in several regions. These findings significantly expand the current knowledge on rodent-associated apicomplexan parasites in Saudi Arabia, revealing novel <i>Hepatozoon</i> haplotypes and highlighting the role of rodents in the transmission of reptile-associated <i>Hepatozoon</i> spp. This study provides basic molecular data crucial to understanding host–parasite relationships and the potential public and veterinary health implications of these parasites in arid ecosystems.