Background and Aim: Ducks worldwide are infected with duck circovirus (DuCV), which causes feather abnormality, emaciation, and poor growth performance. DuCV is similar to other circoviruses that induce immunosuppression due to the occurrence of the bursae of Fabricius (BF) and spleen atrophies. In Thailand, retarded ducks with feather losses were submitted for disease investigation. The ducks presented low body weight gain, had small BF and spleens, and were consistent with duck-infected DuCV. Our study investigated the possibility of DuCV infection in duck flocks in Thailand. We also analyzed the genetic characteristics of the virus. Materials and Methods: BF and spleen samples were collected from affected meat and layer ducks from six farms thought to have been infected with DuCV. These tissues were then subjected to histopathological examination and molecular identification using conventional polymerase chain reaction and nucleotide sequencing. To identify DuCV, phylogenetic trees were generated using MEGA version X software. Samples of tissues or swabs were collected to determine whether coinfections with bacteria and viruses existed. Results: Phylogenetic analysis using the entire genome (1995–1996 bp) and cap gene (762 bp) revealed that the DuCV isolates circulating in Thailand belonged to DuCV genotype I, which was further subdivided into two sub-genotypes: sub-genotype I b and an unclassified sub-genotype based on reference sub-genotypes. Thai isolates have variations in 10 amino acid residues in the capsid protein. Ducks infected with Thai DuCV were also coinfected with Riemerella anatipestifer, Escherichia coli, Pasteurella multocida, duck viral enteritis, and duck Tembusu virus, which is consistent with previous DuCV infection studies. Conclusion: Six DuCVs from ducks who were previously found to have feather loss, were underweight, had growth retardation, and had poor body condition were identified in this study as belonging to genotype Ⅰ and constituting at least two sub-genotypes. Due to the immunosuppressive effects of DuCV, coinfection of bacterial and viral pathogens was typically observed in Thai DuCV-infected ducks. Keywords: duck, duck circovirus, genetic characterization, immunosuppression, phylogenetic tree.

Emerging viral diseases, such as tilapia parvovirus (TiPV), are having a significant economic impact on global tilapia aquaculture. TiPV is responsible for the mass mortality of Nile tilapia ( Oreochromis niloticus ) and red hybrid tilapia ( Oreochromis spp.) in China, India and Thailand. We, therefore, aimed to determine the current status of TiPV infection and distribution and the risk factors associated with TiPV infection in red hybrid tilapia farms in Thailand. In this cross‐sectional study, a total of 101 samples, each comprising five moribund fish, were collected from 40 red hybrid tilapia farms across various provinces in Thailand between September 2022 and March 2024. The data on the farm characteristics and management practices were obtained via questionnaires and direct observation. A total of 23 factors were assessed, including six related to farm characteristics, 13 associated with farm management practices and four concerning the presence of other pathogens. The data from 101 samples were analysed using unconditional and mixed‐effects logistic regression, revealing a percentage of TiPV infection was 11.88%. Two significant risk factors associated with TiPV infection were identified: the source of the fish ( p = 0.020) and the initial fish weight at the stocking date ( p = 0.026). Conversely, the feeding method ( p = 0.039) was found to be a protective factor against TiPV infection. This study is the first to investigate the epidemiology of TiPV infection in farmed red hybrid tilapia. Our findings are important for improving farm management practices, mitigating the risk of TiPV infection and developing effective disease control strategies.

In this study, we developed a recombinase-aided amplification combined with lateral flow dipstick (RAA-LFD) assay to compare with polymerase chain reaction (PCR) and quantitative PCR (qPCR) in detecting PCV2 in suspected field samples.

Background and Aim: Duck circovirus (DuCV) is an immunosuppressive pathogen linked to poor growth, feather abnormalities, and increased susceptibility to co-infections, leading to significant economic losses in duck production. Rapid and large-scale serological screening tools are essential for epidemiological surveillance and biosecurity. This study aimed to develop and validate an indirect enzyme-linked immunosorbent assay (iELISA) based on a recombinant capsid (Cap) protein for sensitive and specific detection of antibodies against DuCV. Materials and Methods: The cap gene from a Thai DuCV genotype I isolate was cloned into the pQE-31 vector and expressed in Escherichia coli M15. The 27 kDa recombinant Cap protein was purified under denaturing conditions, and its antigenicity was confirmed by Western blotting. The iELISA was optimized by checkerboard titration to determine the optimal antigen coating concentration and serum dilution. Diagnostic sensitivity, specificity, cross-reactivity, repeatability, reproducibility, and agreement with Western blotting were assessed using 80 positive, 103 negative, and 189 field serum samples. Results: The optimized iELISA used 12 μg/well of antigen and a 1:20 serum dilution, producing the highest positive-to-negative optical density ratio. Receiver operating characteristic curve analysis yielded an area under the curve of 0.996, with 97.5% sensitivity and 98.1% specificity. No cross-reactivity was detected with sera positive for duck Tembusu virus, duck viral enteritis virus, or Riemerella anatipestifer. Intra- and inter-assay coefficients of variation were below 6.5% and 9.1%, respectively. Diagnostic agreement with Western blotting across 189 field sera was 91.0%, with a Cohen’s kappa of 0.752, indicating substantial concordance. Conclusion: The developed recombinant Cap-based iELISA provides a reliable, specific, and reproducible tool for large-scale DuCV serosurveillance. Its high diagnostic accuracy and scalability support its application in flock-level monitoring, pre-movement screening, and epidemiological studies, facilitating improved biosecurity and informed disease control strategies within the duck industry. Keywords: capsid protein, duck circovirus, indirect enzyme-linked immunosorbent assay, recombinant protein, serodiagnosis.

Background and Aim: The sun conure (Aratinga solstitialis), a bird belonging to the Psittaciformes family, is a popular pet because of its bright color and beautiful appearance. The sun conure is a monomorphic bird with similar appearances between males and females, making sex identification difficult by observing the external morphology. Therefore, molecular techniques are utilized. Loop-mediated isothermal amplification (LAMP) is a molecular technique that is often applied for sex identification in birds and is a quick and simple method that can be used in the field. This study used the LAMP technique to improve sex identification in sun conures by observing the color change of hydroxy naphthol blue. Materials and Methods: Two primer sets, SunSpin-W and SunSpin-Z, were designed for sex identification in sun conures using the LAMP technique specific to the spindlin gene. The developed LAMP reaction was tested for optimal conditions, sensitivity, and specificity compared with the polymerase chain reaction (PCR) technique. Results: The SunSpin-W primer set amplified only female birds, whereas the SunSpin-Z primer set amplified DNA from both male and female birds. The primer sets were optimized at 62°C for 45 min. A positive result was visible to the naked eye from the color change of the reaction. In the LAMP assay, the lowest detectable concentration was 10 pg/μL and in the PCR assay, it was 1 ng/μL, while a 100% accuracy rate in sex identification was observed when comparing the LAMP assay results with the PCR assay. Conclusion: This study successfully developed a LAMP technique for sex identification of sun conure, which took 45 min to complete and can be expanded for use in the field. Keywords: loop-mediated isothermal amplification, sex identification, spindlin gene, sun conure.

Bovine respiratory syncytial virus (BRSV) is a major viral pathogen associated with bovine respiratory disease (BRD), a leading cause of illness and economic loss in cattle worldwide. In June 2022, an acute respiratory outbreak occurred in a dairy herd in Photharam District, Ratchaburi Province, Thailand, affecting 25 of 103 cows (24.3%) and resulting in three deaths (2.9%). This study aimed to confirm BRSV as the etiological agent of the outbreak and to genetically and phylogenetically characterize Thai BRSV strains using partial G gene sequencing. Clinical signs included fever, nasal discharge, coughing, and subcutaneous emphysema. Nested reverse transcription-polymerase chain reaction (nested RT-PCR), a sensitive method for detecting viral RNA and targeting the F and G genes, confirmed BRSV in all samples. At the same time, bovine parainfluenza virus type 3 (BPIV-3), bovine viral diarrhea virus (BVDV), and bovine herpesvirus 1 (BoHV-1) were not detected. Phylogenetic analysis of partial G gene sequences showed that all Thai isolates clustered closely within subgroup III, with 100% nucleotide identity among themselves and 85.9–97.7% similarity to subgroup III strains from other countries. Amino acid alignment indicated conservation of key antigenic motifs, including the cysteine noose, with only minor substitutions compared to some foreign strains. This study provides the first genetic and phylogenetic characterization of BRSV in Thailand, highlighting the genetic stability of subgroup III and providing baseline molecular data to support regional surveillance, diagnostics, and vaccine strategies.