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Avian pox is a highly contagious avian disease, yet relatively little is known about the epidemiology and transmission of Avipoxviruses. Using a molecular approach, we report evidence for a potential link between birds and field-caught mosquitoes in the transmission of Fowlpox virus (FWPV) in Singapore. Comparison of fpv167 (P4b), fpv126 (VLTF-1), fpv175-176 (A11R-A12L) and fpv140 (H3L) gene sequences revealed close relatedness between FWPV strains obtained from cutaneous lesions of a chicken and four pools of Culex pseudovishnui, Culex spp. (vishnui group) and Coquellitidea crassipes caught in the vicinity of the study site. Chicken-derived viruses characterized during two separate infections two years later were also identical to those detected in the first event, suggesting repeated transmission of closely related FWPV strains in the locality. Since the study location is home to resident and migratory birds, we postulated that wild birds could be the source of FWPV and that bird-biting mosquitoes could act as bridging mechanical vectors. Therefore, we determined whether the FWPV-positive mosquito pools (n=4) were positive for avian DNA using a polymerase chain reaction-sequencing assay. Our findings confirmed the presence of avian host DNA in all mosquito pools, suggesting a role for Cx. pseudovishnui, Culex spp. (vishnui group) and Cq. crassipes mosquitoes in FWPV transmission. Our study exemplifies the utilization of molecular tools to understand transmission networks of pathogens affecting avian populations, which has important implications for the design of effective control measures to minimize disease burden and economic loss.

Rabbit Haemorrhagic Disease (RHD) is a significant viral disease caused by infection with Rabbit Haemorrhagic Disease virus (RHDV). The first documented cases of RHDV in Singapore occurred in adult pet European rabbits (Oryctolagus cuniculus) in September 2020. Rabbits presented with acute hyporexia, lethargy, huddled posture, and varying degrees of pyrexia and tachypnoea. Clinical pathology consistently reflected markedly elevated Alanine Aminotransferase (ALT), Aspartate Aminotransferase (AST) and Alkaline Phosphatase (ALKP). Hepatic lobe torsion was ruled out using ultrasonography and colour doppler studies in all patients. A total of 11 rabbits owned by 3 families was presented to the clinics; 8/11 rabbits died within 48 hours of presentation, while the remaining two rabbits had recovered after prolonged hospitalisation and one rabbit was aclinical. Histopathology revealed acute, marked diffuse hepatocellular necrosis and degeneration, findings which were suggestive for RHDV infection and prompted the undertaking of further molecular diagnostics. Subsequent polymerase-chain reaction of the liver samples detected RHDV RNA. Molecular characterization of viral genomes by whole genome sequencing revealed that the outbreak strain was of the genotype GI.2 (RHDV2/RHDVb). Nucleotide sequences of the VP60 gene were compared with various RHDV variants using phylogenetic analysis. The sample genome shared highest sequence identity with a GI.2-genotyped virus from GenBank (RHDV isolate Algarve 1 polyprotein and minor structural protein (VP10) genes, GenBank accession KF442961). The combination of clinical, histopathological, molecular, and sequencing technologies enabled rapid detection and detailed genetic characterization of the RHDV virus causing the present outbreak for prompt implementation of disease control measures in Singapore. Further epidemiological investigations of potential virus introduction into Singapore are ongoing.

African horse sickness (AHS) is a highly infectious and deadly disease despite availability of vaccines. Molecular characterization of African horse sickness virus (AHSV) detected from the March 2020 Thailand outbreak was carried out by whole-genome sequencing using Nanopore with a Sequence-Independent Single Primer Amplification (SISPA) approach. Nucleotide sequence of the whole genome was compared with closest matching AHSV strains using phylogenetic analyses and the AHSV-1 virus shared high sequence identity with isolates from the same outbreak. Substitution analysis revealed non-synonymous and synonymous substitutions in the VP2 gene as compared to circulating South African strains. The use of sequencing technologies, such as Nanopore with SISPA, has enabled rapid detection, identification and detailed genetic characterization of the AHS virus for informed decision-making and implementation of disease control measures. Active genetic information sharing has also allowed emergence of AHSV to be better monitored on a global basis.

Hepatitis E is a significant liver disease caused by infection with Hepatitis E virus (HEV). The risk factors for hepatitis E in developed countries include blood transfusion and ingestion of undercooked meat or meat products derived from HEV-infected animals. Since 2000, there have been increased human hepatitis E incidence reported in Singapore. Although the causes of this increase have not been established, several studies have linked zoonotic HEV infections in humans to pork consumption. It is therefore important to closely monitor the presence of HEV in food sources for the prevalence and virulence. In this study, we demonstrated the presence of HEV in pigs imported into Singapore for consumption through serological and molecular investigation of live pig and post-slaughter samples collected between 2000 and 2019. Among imported pigs, anti-HEV antibodies prevalence remained at a level around 35% until 2017, with a statistically significant increase in 2018. HEV RNA was detected in 8.40% (34/405) of the fecal samples, indicative of an active infection in the pigs. HEV RNA was also detected in 6.67% (4/60) of liver samples obtained post-slaughter. We also report the development of an RT-PCR-based Next-Generation Sequencing (NGS) method that enabled full sequencing of the HEV genome in HEV RNA-positive samples in a relatively short span of time. Phylogenetic analysis identified the HEV in one of the imported pigs (HEV-S28) as Genotype 3a, which clustered together with the human HEV strains previously identified in Singapore. We found that the HEV-S28 strain exhibited amino acid substitutions that are associated with reduced HEV replication efficiency. The increase in anti-HEV seroprevalence in the pig population from 2018 is worth further exploration. We will continue to monitor the prevalent HEV strains and assess the genetic diversity of HEV in the imported pigs to confirm the potential association with human infections.

Equine influenza (EI) is a respiratory disease caused by equine influenza A virus (EIV, H3N8) infection. Rapid diagnosis is essential to limit the disease spread. We previously reported that some rapid antigen detection (RAD) tests are fit for diagnosing EI although their sensitivity is not optimal. Here, we evaluated the performance of the newly developed RAD test using silver amplification immunochromatography (Quick Chaser Auto Flu A, B: QCA) to diagnose EI. The detection limits of QCA for EIVs were five-fold lower than the conventional RAD tests. The duration of virus antigen detection in the infected horses was longer than the conventional RAD tests. We conclude that QCA could be a valuable diagnostic method for EI.

To facilitate the temporary importation of horses for competition and racing purposes, with a minimum risk of transmitting equine influenza, the World Organisation for Animal Health (Office International des Epizooties, or OIE), formally engaged in a public&ndash, private partnership with the Federation Equestre Internationale (FEI) and the International Federation for Horseracing Authorities (IFHA) to establish, within the context of existing OIE standards, a science-based rationale to identify the ideal time period for equine influenza vaccination prior to shipment. Field trials using vaccines based on different technologies were carried out on three continents. The antibody response post-booster vaccination at intervals aligned with the different rules/recommendations of the OIE, FEI, and IFHA, was monitored by single radial haemolysis. It was determined that 14 days was the optimum period necessary to allow horses adequate time to respond to booster vaccination and for horses that have previously received four or more doses of vaccine and are older than four years, it is adequate to allow vaccination within 180 days of shipment. In contrast, the results indicate that there is a potential benefit to younger (four years old or younger) horses in requiring booster vaccination within 90 days of shipment, consistent with the current OIE standard.

We report pathogenic feline parvovirus and canine parvovirus-2c infection in wild Asian palm civets (Paradoxurus hermaphroditus), as demonstrated by histopathology and immunohistochemistry findings of parvoviral enteropathy. We performed molecular characterization and phylogeny studies to obtain an improved understanding of disease transmission dynamics between domestic and wild carnivores.

Policies and guidelines regarding sale of ready-to-eat raw fish dishes have been updated., We assessed microbial safety and quality of raw fish sold in Singapore during 2015–2016 to complement epidemiologic findings for an outbreak of infection with group B Streptococcus serotype III sequence type (ST) 283 associated with raw fish consumption. Fish-associated group B Streptococcus ST283 strains included strains nearly identical (0–2 single-nucleotide polymorphisms) with the human outbreak strain, as well as strains in another distinct ST283 clade (57–71 single-nucleotide polymorphisms). Our investigations highlight the risk for contamination of freshwater fish (which are handled and distributed separately from saltwater fish sold as sashimi) and the need for improved hygienic handling of all fish for raw consumption. These results have led to updated policy and guidelines regarding the sale of ready-to-eat raw fish dishes in Singapore.

Melioidosis is a notifiable infectious disease registered with the Ministry of Health (MOH) and Agri-Food & Veterinary Authority (AVA), Singapore. From a clinical perspective, increased awareness of the disease has led to early detection and treatment initiation, thus resulting in decreasing mortality rates in recent years. However, the disease still poses a threat to local pet, zoo and farm animals, where early diagnosis is a challenge. The lack of routine environmental surveillance studies also makes prevention of the disease in animals difficult. To date, there have been no reports that provide a complete picture of how the disease impacts the local human and animal populations in Singapore. Information on the distribution of Burkholderia pseudomallei in the environment is also lacking. The aim of this review is to provide a comprehensive overview of both published and unpublished clinical, veterinary and environmental studies on melioidosis in Singapore to achieve better awareness and management of the disease.