Geographical Distribution and Molecular Characterization of Dirofilaria spp. in Dogs Across Kazakhstan

Canine dirofilariosis caused by Dirofilaria immitis and Dirofilaria repens is a vector-borne zoonotic infection of considerable veterinary and public health importance. Despite reports of the circulation of Dirofilaria spp. in neighboring countries, data on the molecular prevalence, species composition, and genetic diversity of these parasites in dogs from Kazakhstan remain limited. In the present study, owned, shelter, and stray dogs, which serve as the principal reservoirs of infection, were examined for the presence of microfilariae in blood, and the circulation of Dirofilaria spp. was molecularly confirmed. The study was conducted between September 2024 and January 2026 and included 751 canine blood samples collected from 10 regions of Kazakhstan. Initial screening was performed using the modified Knott test. Molecular identification was carried out through amplification of the mitochondrial cox1 gene, followed by DNA sequencing and comparative analysis with reference sequences available in GenBank. Phylogenetic analysis was performed to assess the genetic relationships of the detected isolates. The overall molecular prevalence of Dirofilaria spp. was 3.6% (27/751). The highest infection rate was recorded in the Aktobe region (22.3%), while positive cases were also detected in the Akmola (2.7%), Kostanay (1.7%), and West Kazakhstan (1.8%) regions. Species identification revealed the predominance of D. repens, whereas D. immitis was detected only in Aktobe region. Phylogenetic analysis confirmed the species identity of all obtained sequences and demonstrated a high degree of genetic similarity with Dirofilaria isolates previously reported from Europe and Asia. These findings confirm the circulation of Dirofilaria spp. among dogs in several regions of Kazakhstan and indicate the ongoing expansion of canine dirofilariosis in Central Asia. This study provides the first molecular genetic data on Dirofilaria spp. in dogs from Kazakhstan and highlights the need for continued epidemiological surveillance and assessment of potential risks to animal and human health.