Novel Recombinant Foot-and-Mouth Disease Virus Circulating in Vietnam.

We report the genome sequences of 12 recombinant foot-and-mouth disease virus isolates from Vietnam. The recombinant strain has a capsid region from an A/Sea-97 strain and a nonstructural segment from an O/ME-SA/PanAsia strain. The isolates were obtained from two outbreak samples collected in June 2017 and 10 subclinical samples collected between 2017 and 2019.

Foot-and-Mouth Disease Virus Serotype O/CATHAY Genome Sequences from Five Outbreaks in Vietnam, 2017 to 2019.

We report the genomes of five foot-and-mouth disease viruses (FMDVs) from distinct provinces in Vietnam. All five viruses were grouped within the O/CATHAY topotype. Sequences contain the full polyprotein coding sequence and partial untranslated regions. These genomes provide critical data on the spread and evolution of FMDVs in the region.

First Genome Sequence of Foot-and-Mouth Disease Virus Serotype O Sublineage Ind2001e from Southern Vietnam.

We report the polyprotein coding sequence of the newly defined Ind2001e sublineage of foot-and-mouth disease virus (FMDV) serotype O, isolated from a bovine epithelial tissue sample collected in 2017 in Kon Tum Province, Vietnam. This discovery updates FMDV diversity in Vietnam, has implications for FMDV epidemiology, and influences future vaccine selections.

First Detection and Genome Sequence of Senecavirus A in Vietnam.

In 2018, senecavirus A was detected for the first time in Vietnam. This report contains the first complete genome of a senecavirus A isolate collected from pigs in Kon Tum Province, Vietnam. This novel incursion has substantial implications for regional control of vesicular transboundary diseases.

First detection of foot-and-mouth disease virus O/Ind-2001d in Vietnam.

In recent years, foot-and-mouth disease virus (FMDV) serotype O, topotype Middle East-South Asia (ME-SA), lineage Ind-2001d has spread from the Indian subcontinent to the Middle East, North Africa, and Southeast Asia. In the current report, we describe the first detection of this lineage in Vietnam in May, 2015 in Dak Nông province. Three subsequent outbreaks caused by genetically related viruses occurred between May-October, 2015 after which the virus was not detected in clinical outbreaks for at least 15 subsequent months. The observed outbreaks affected (in chronological order): cattle in Dak Nông province, pigs in Dak Lak province and Dak Nông province, and cattle in Ninh Thuan province. The clinical syndromes associated with these outbreaks were consistent with typical FMD in the affected species. Overall attack rate on affected premises was 0.85 in pigs and 0.93 in cattle over the course of the outbreak. Amongst 378 pigs at risk on affected premises, 85 pigs died during the outbreaks; there were no deaths among cattle. The manner in which FMDV/O/ME-SA/Ind-2001d was introduced into Vietnam remains undetermined; however, movement of live cattle is the suspected route. This incursion has substantial implications for epidemiology and control of FMD in Southeast Asia.

Genome Sequence of Foot-and-Mouth Disease Virus Serotype O Lineage Ind-2001d Collected in Vietnam in 2015.

In 2015, foot-and-mouth disease (FMD) virus lineage Ind-2001 was detected for the first time in Southeast Asia. This report contains the first near-complete genome sequence of a viral isolate from this lineage collected from an outbreak in Vietnam. This novel incursion has substantial implications for regional FMD control measures.

Highly pathogenic avian influenza (H5N1) in ducks and in-contact chickens in backyard and smallholder commercial duck farms in Viet Nam.

Scavenging ducks are thought to play an important role in the maintenance and transmission of highly pathogenic avian influenza (HPAI) H5N1 virus among domesticated and wild bird populations in South East Asia, but detailed field epidemiological results describing the infection status of domestic ducks and in-contact chickens have not been published. We conducted a longitudinal study, monitoring ducks and in-contact chickens in 80 flocks in the Mekong Delta of Viet Nam with bi-monthly testing from May 2007 until May 2008. Because H5 vaccination campaigns are conducted at regular intervals in poultry flocks in Viet Nam, both unvaccinated sentinel and H5 vaccinates were monitored. On each farm, a total of 10 birds were selected: 7 ducks (4 unvaccinated and 3 vaccinated) and 3 chickens (2 unvaccinated and 1 vaccinated) that were in close contact with the ducks. Blood samples were tested for H5 antibodies using the hemagglutination inhibition test, with H5 antibody titers ≥2(4) considered to indicate past exposure to H5 field or vaccine virus. Titers of vaccinated birds were analyzed for samples collected more than 3 weeks post-vaccination. Pooled oropharyngeal and cloacal swabs were assessed for H5 viral RNA using real-time PCR. Bird- and flock-level prevalences were estimated accounting for sampling fractions and clustering under the multi-stage sampling design with birds being sampled within flocks within villages in four different provinces. In total, serum and swab samples from 5409 birds-samplings were analyzed. Bird-level seroprevalence was 17.5% (95% CI: 14.1, 20.9) amongst unvaccinated ducks and 10.7% (95% CI: 7.4, 14.4) amongst unvaccinated in-contact chickens. Flock-level seroprevalence (proportion of flock-visits with at least one unvaccinated bird test positive) was 42.6% (95% CI: 38.0, 47.2) for ducks and 19.0% (95% CI: 13.6, 24.4) for chickens. Only 54.3% (95% CI: 39.2, 69.3) of vaccinated ducks and 55.5% (95% CI: 46.8, 64.2) of vaccinated in-contact chickens had H5 antibodies at more than 3 weeks post-vaccination. At about 40% and 48% of flock-visits, less than 50% of sampled vaccinated ducks and chickens, respectively, had positive titers. The flock-level virus prevalence (proportion of flocks with at least one bird positive for H5 virus of the vaccinated and unvaccinated birds tested) was 0.7% (95% CI: 0.0, 2.1). No HPAI outbreaks or mortality suspected to be due to HPAI occurred in study flocks during the observation period. Our results indicate that a substantial proportion of ducks and in-contact chickens were exposed to H5 virus during the study period. In the face of this widespread exposure to H5 virus, and despite only moderate proportions of birds developing positive titers post-vaccination, flocks were not affected by HPAI outbreaks during our study period. The higher bird-level seroprevalence in ducks compared to in-contact chickens may be due to greater durations of antibody persistence in ducks or greater rates of H5 virus exposure. These findings indicate that ducks are potentially an important source of H5 virus for other bird species.