Serological and molecular genetics of avian metapneumovirus infection in broilers and layers isolated from Kazakhstan

The purpose of this study was to conduct serological and molecular genetic characterisation of avian metapneumovirus infection isolates identified in Kazakhstan to assess their genetic variability and the effectiveness of preventive measures against infection. Three big poultry farms in North Kazakhstan and Almaty districts provided 1,500 broiler and laying hen samples for the investigation. Polymerase chain reaction confirmed avian metapneumovirus RNA in samples, and enzyme-linked immunosorbent test showed significant bird antibody levels. Laying hens in North Kazakhstan had the highest immunological response, suggesting preventive measures are more successful there. The isolates' genetic sequencing demonstrated modest virus variants, with more substantial alterations in the Almaty Region, indicating regional virus circulation. All farms tested had high antibody levels, with laying hens in the North Kazakhstan Region having the highest values (1.92 ± 0.10 OD) and broilers having a more balanced response (1.78-1.85 OD). North Kazakhstan isolates had 5 genome variants, 97.2% similarity to reference strains, while Almaty isolates had up to 8 variations, 94.5% similarity. Epizootological data showed lower incidence rates in North Kazakhstan (12.5% in broilers, 15.3% in laying hens) and higher rates in Almaty farms, especially with higher housing density (20.1%). Hipraviar SHS vaccination boosted antibody levels by 67-85% in North Kazakhstan and 55-78% in Almaty farms and reduced clinical symptoms within 10-14 days. Vaccination and veterinarian control are highly efficient, as shown by regional viral circulation variances.