Avian metapneumovirus (aMPV), classified within the Pneumoviridae family, wreaks havoc on poultry health. It typically causes upper respiratory tract and reproductive tract infections, mainly in turkeys, chickens, and ducks. Four subtypes of AMPV (A, B, C, D) and two unclassified subtypes have been identified, of which subtypes A and B are widely distributed across the world. In January 2024, an outbreak of severe respiratory disease occurred on turkey and chicken farms across different states in the US. Metagenomics sequencing of selected tissue and swab samples confirmed the presence of aMPV subtype B. Subsequently, all samples were screened using an aMPV subtype A and B multiplex real-time RT-PCR kit. Of the 221 farms, 124 (56%) were found to be positive for aMPV-B. All samples were negative for subtype A. Six whole genomes were assembled, five from turkeys and one from chickens; all six assembled genomes showed 99.29 to 99.98% nucleotide identity, indicating a clonal expansion event for aMPV-B within the country. In addition, all six sequences showed 97.74 to 98.58% nucleotide identity with previously reported subtype B sequences, e.g., VCO3/60616, Hungary/657/4, and BR/1890/E1/19. In comparison to these two reference strains, the study sequences showed unique 49–62 amino acid changes across the genome, with maximum changes in glycoprotein (G). One unique AA change from T (Threonine) to I (Isoleucine) at position 153 in G protein was reported only in the chicken aMPV sequence, which differentiated it from turkey sequences. The twelve unique AA changes along with change in polarity of the G protein may indicate that these unique changes played a role in the adaptation of this virus in the US poultry. This is the first documented report of aMPV subtype B in US poultry, highlighting the need for further investigations into its genotypic characterization, pathogenesis, and evolutionary dynamics.

With the rapidly increasing demand for poultry products and the current challenges facing the poultry industry, the application of biotechnology to enhance poultry production has gained growing significance. Biotechnology encompasses all forms of technology that can be harnessed to improve poultry health and production efficiency. Notably, biotechnology-based approaches have fueled rapid advances in biological research, including (a) genetic manipulation in poultry breeding to improve the growth and egg production traits and disease resistance, (b) rapid identification of infectious agents using DNA-based approaches, (c) inclusion of natural and synthetic feed additives to poultry diets to enhance their nutritional value and maximize feed utilization by birds, and (d) production of biological products such as vaccines and various types of immunostimulants to increase the defensive activity of the immune system against pathogenic infection. Indeed, managing both existing and newly emerging infectious diseases presents a challenge for poultry production. However, recent strides in vaccine technology are demonstrating significant promise for disease prevention and control. This review focuses on the evolving applications of biotechnology aimed at enhancing vaccine immunogenicity, efficacy, stability, and delivery.

Respiratory viral diseases infecting poultry lead to variable lesions in the respiratory organs, including nasal sinuses, trachea, lungs, and air sacs. Additional involvement of eyelids/conjunctiva was reported. The distribution and the intensity of lesions depend on multiple factors, including virulence, the host’s immunity, and secondary or concurrent infections. It may be challenging to detect remarkable lesions during experimental infections conducted in a controlled environment because some viruses fail to produce the intense lesions seen in field cases. This creates a challenge in developing a reliable model to study pathogenicity or vaccine efficacy experimentally. The development of the proposed histologic respiratory index (HRI) aims to help monitor the least microscopic changes that can be scored, thereby creating an objective and accurate grading of lesions in experimentally infected birds. HRI scores the changes in eyelids/conjunctiva and respiratory mucosa, including hyperplasia, metaplasia, inflammatory cellular infiltration in the submucosa, including lymphocytes and heterophils, and vascular changes (vasculitis) in nasal sinuses, trachea, and lungs. The score was validated in birds infected experimentally with avian metapneumovirus (aMPV) and low pathogenic avian influenza (LPAI-H4N6). The HRI reliably graded higher scores in the respiratory organs of experimentally infected birds compared with non-infected control ones. The HRI is the first of its type with poultry viral respiratory pathogens and it was initially proven to be a reliable in pathogenicity and vaccine trials of certain poultry respiratory viral diseases.

Porcine reproductive and respiratory syndrome (PRRS) is a serious disease that causes reproductive failure and late abortion in breeder farms, as well as severe respiratory manifestations in pigs of all ages. In the United States, the swine industry has been affected by PRRSV-2, particularly due to control challenges and the virus’s ongoing evolution. In this study, we conducted a genetic characterization of the 642 PRRSV-2 ORF5 sequences generated from diagnostic submissions at the Animal Disease Research and Diagnostic Laboratory (ADRDL) at South Dakota State University (SDSU). These sequences were generated over a 3-year period from 2023 through 2025, with 208 (32.4%), 130 (20.2%), and 304 (47.4%) sequences in 2023, 2024, and 2025, respectively. These sequences were from swine diagnostic submissions from ten states in the Midwest, including Minnesota (MN; 350/642, 54.5%), South Dakota (SD; 182/642, 28.3%), and Iowa (IA; 73/642, 11.4%), collectively accounting for 94.2% of submitted sequences. The genetic typing revealed that the L1C sub-lineage was the most frequently detected among the submitted sequences, accounting for around 60%, with L1C.5 as the major contributor (371/642). Other sub-lineages, such as L5A, L1A, L1D, and L1H, were also detected, but in smaller numbers. More than 80% of the detected sequences were classified as wild-type or wild-like based on ORF5 identity to commercial vaccine reference strains. Interestingly, this study documented increased detection of the recently reported L1C.5.32 variant, which was the most frequently detected variant in 2025 (123 detections), particularly in Minnesota. Moreover, L1C.5.34, L1C.5.36, L1C.3.25, and L1C.2 variants were also detected, and the L1H.18 variant showed increased detection, especially in 2025. In conclusion, this study provides genetic characterization of PRRSV-2 ORF5 sequences from Midwestern U.S. diagnostic submissions (a key U.S. swine production region), submitted to the SDSU ADRDL.

From January 2019 to April 2020, the Minnesota Veterinary Diagnostic Laboratory (MVDL) received cases of hepatitis and spiking mortality in young turkey poults (average age 15.5 days) from multiple turkey-producing states. Meat-type turkeys were mainly affected, with a few cases in breeders. Of 188 cases, 88 (47.5%) tested positive for reovirus by virus isolation, with most of the positive cases from 7 to 14-day-old birds (n = 42). Gross lesions consisted of hepatosplenomegaly with acute, multifocal necrosis in both liver and spleen. Microscopically, liver sections showed congestion of hepatic sinusoids and necrotizing hepatitis with infiltration of lymphocytes, plasma cells, and macrophages. Reovirus was detected in liver samples by electron microscopy and in situ hybridization (ISH). Sections of spleen showed areas of necrosis with infiltration of the mixed population of inflammatory cells and depletion of lymphocytes. We consistently isolated reoviruses from livers and tentatively named the virus “Turkey Hepatitis Reovirus” (THRV). Phylogenetic analysis of the newly emerged THRVs revealed their clustering into four distinct groups. This study also highlighted the close antigenic relation between TARV and THRV compared to turkey enteritis reoviruses (TERVs), which shed light on the probable origin of this newly emerged pathotype. In summary, further molecular and pathogenicity studies are recommended on THRVs to help diagnose and control this serious variant.

Viral respiratory diseases infecting poultry lead to variable lesions in the respiratory or-gans, including nasal sinuses, eyelids, trachea, lungs, and air sacs. The distribution and the intensity of lesions depend on multiple factors, including virulence, the host’s im-munity, and secondary or concurrent infections. It may be challenging to detect remarka-ble lesions during experimental infections conducted in a controlled environment. This creates a challenge in developing a reliable model to study pathogenicity or vaccine effi-cacy experimentally. The development of the proposed histologic respiratory index (HRI) aims to help monitor the least microscopic changes that can be scored, thereby creating an objective and accurate grading of lesions in experimentally infected birds. HRI scores the changes in respiratory mucosa, including hyperplasia, metaplasia, inflammatory cellular infiltration in the submucosa, including lymphocytes and heterophils, and vascular changes (vasculitis) in nasal sinuses, eyelids, trachea, and lungs. The score was validated in birds infected experimentally with avian metapneumovirus (aMPV) and low patho-genic avian influenza (LPAI-H4N6). The HRI was reliable in grading lesions in the respir-atory organs of experimentally infected birds compared with non-infected control birds. The HRI was initially proven to be a reliably recruited in pathogenicity and vaccine trials of certain poultry respiratory viral diseases.