Varroosis in Honey Bees in West Kazakhstan: Prevalence and Molecular Diagnosis

Varroosis is a widespread parasitic disease that poses a serious threat to honey bee health, colony productivity, and pollination activity. This study aimed to assess the level of Varroa mite infestation in Apis mellifera honey bees in the West Kazakhstan Region using microscopy and to identify the detected pathogen as Varroa destructor at the molecular level by real-time polymerase chain reaction. Samples were collected in spring 2024 from 12 apiaries located in the Terekti, Baiterek, and Burlin districts and the city of Uralsk. A total of 321 individual bees were examined microscopically, while 158 samples were subjected to molecular genetic analysis. Live bees were immobilized by freezing and stored in 96% ethanol at −22 °C. Part of the biological material was preserved by drying. Before molecular analysis, the bee tissues were homogenized in liquid nitrogen, and the total nucleic acid pool was extracted. A SYBR Green I-based real-time PCR assay was performed to detect the target genomic fragment of V. destructor. The expected length of the amplification product was 79 bp. The specificity of the products was assessed by melting curve analysis and agarose gel electrophoresis. Microscopic examination detected Varroa mites in seven of the 12 apiaries, resulting in an apiary-level detection rate of 58%. Negative microscopy results were obtained for the remaining five apiaries. Real-time PCR detected the target fragment of the V. destructor genome in 90% of the samples included in the molecular analysis, while no amplification was recorded in 10% of the samples. The species identity of the pathogen was confirmed by a single characteristic melting peak at approximately 78 °C and the presence of the expected 79 bp amplicon. Because the microscopy and PCR findings represent different units of analysis, they should be regarded as complementary results. The combined application of microscopic screening, real-time PCR, melting curve analysis, and gel electrophoresis enables reliable detection of varroosis and species-level identification of its causative agent. The findings support the need for regular epizootiological monitoring, quantitative assessment of infestation intensity, and timely veterinary preventive measures in apiaries across West Kazakhstan.