Long‐term follow‐up of convalescent pigs and their offspring after an outbreak of acute African swine fever in Vietnam

Oh, Tae-Kwang; Nguyen, Tien M.; Ngo, Tram Thi Ngoc; Thinh, Danh; Nguyen, Trang Thi; Duc, Luc Do; Tien, Duy

doi:10.1111/tbed.14276

Cited by 7 publications

(5 citation statements)

References 13 publications

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“…In fact, ASFV strains circulating in Vietnam have been confirmed as highly virulent ASFV strains and may have originated in China (Nguyen et al 2021;Tran et al 2020;Van Phan Le et al 2019). At the beginning of ASF occurrence in Vietnam, it caused severe impacts with a very high mortality rate (Oh et al 2021). During outbreak of the study, the highest number of pigs dying in 1 day was only 5% (81 heads); most infected pigs died.…”

Section: Discussionmentioning

confidence: 88%

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The study of antigen carrying and lesions observed in pigs that survived post African swine fever virus infection

Lai

Nguyen

et al. 2022

Trop Anim Health Prod

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African swine fever (ASF) is a dangerous infectious disease of domestic pigs and wild boar caused by African swine fever virus (ASFV). In Vietnam, the ASF epidemic is gradually turning into an endemic status with several recovered pigs post infection, but there were not many studies evaluating the role of these pigs in the epidemiological context in Vietnam. The aim of this study was to evaluate the viral antigen distribution and lesions in recovered pigs post ASFV infection. Ten pigs recovered from ASF at 6 weeks of age were monitored and assessed for anti-ASFV antibodies and viremia until slaughter. The five major organs (lung, liver, spleen, kidney, and lymph nodes) of these pigs were evaluated for microscopic lesions and viral antigen distribution. Anti-ASFV antibody was consistently observed to be high (S/P% ≥ 80) until slaughter, while viremia levels were very high (7 log 10 copies/mL) at 6 weeks of age and gradually decreased to undetectable levels at 12 weeks of age (6th week post-infection). At slaughter, the ASFV-associated lesions in the organs of these pigs were mild and nonspecific. Seven out of ten pigs recovering from ASF still carried the virus in surveyed organ tissues, although not in the serum. These findings suggest that ASF-recovered pigs may be potential carriers of the virus, contributing to the increased complexity in the current endemic status in Vietnam.

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Section: Discussionmentioning

confidence: 88%

“…Positive cells were counted and averaged over 3 microfields at 400 × magnification. The degree of positivity was scored on a scale of 0 (no positive cells), 1 + (1-10 positive cells), 2 + (10-30 positive cells), 3 + (30-100 positive cells), and 4 + (> 100 positive cells) (Oh et al 2021).…”

Section: Asfv Antigen Detection By Immunohistochemistrymentioning

confidence: 99%

The study of antigen carrying and lesions observed in pigs that survived post African swine fever virus infection

Lai

Nguyen

et al. 2022

Trop Anim Health Prod

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“…Infective virus may be present in tissues, in particular lymph nodes and tonsils, for longer [ 176 ]. The role of persistently infected pigs in maintenance of ASF infection is much debated, but there is increasing evidence that pigs that fully recover from ASF are inefficient at transmitting the virus through contact [ 94 , 177 , 178 , 179 ].…”

Section: Discussionmentioning

confidence: 99%

Review of the Pig-Adapted African Swine Fever Viruses in and Outside Africa

et al. 2022

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The region in eastern, central and southern Africa (ECSA) where African swine fever (ASF) originated in a sylvatic cycle is home to all the p72 genotypes of ASF virus identified so far. While 20 of the 24 genotypes have been isolated from outbreaks in domestic pigs in the region, only five of the genotypes (I, II, VIII, IX, X) have an extended field presence associated with domestic pigs. Of the genotypes that appear to be strongly adapted to domestic pigs, two have spread beyond the African continent and have been the focus of efforts to develop vaccines against ASF. Most of the experimental ASF vaccines described do not protect against a wider spectrum of viruses and may be less useful in the event of incursions of different strains or where multiple genotypes co-exist. The other three pig-adapted strains that are currently restricted to the ECSA region might spread, and priority should be given to understanding not only the genetic and antigenic characteristics of these viruses but also their history. We review historic and current knowledge of the distribution of these five virus genotypes, and note that as was the case for genotype II, some pig-associated viruses have the propensity for geographical range expansion. These features are valuable for prioritizing vaccine-development efforts to ensure a swift response to virus escape. However, whilst ASF vaccines are critical for high-production systems, global food security relies on parallel efforts to improve biosecurity and pig production in Africa and on continued ASFV surveillance and characterisation in the ECSA region.

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“…A longitudinal study on farms in Uganda that had experienced ASF outbreaks provided no evidence for persistence of ASFV in blood or serum of pigs [ 235 ], although no culling is undertaken in LMICs where ASF is endemic. The most significant study to date followed 14 gilts that recovered from infection with a highly virulent strain of ASFV in Vietnam [ 236 ]. The gilts were derived from a group of 70 convalescent weaner pigs that had shown mild or no clinical signs and survived an outbreak which had killed 409 of their cohorts in the same barn.…”

Section: Appropriate Outbreak Responses and Starting Againmentioning

confidence: 99%

Innovative Research Offers New Hope for Managing African Swine Fever Better in Resource-Limited Smallholder Farming Settings: A Timely Update

et al. 2023

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African swine fever (ASF) in domestic pigs has, since its discovery in Africa more than a century ago, been associated with subsistence pig keeping with low levels of biosecurity. Likewise, smallholder and backyard pig farming in resource-limited settings have been notably affected during the ongoing epidemic in Eastern Europe, Asia, the Pacific, and Caribbean regions. Many challenges to managing ASF in such settings have been identified in the ongoing as well as previous epidemics. Consistent implementation of biosecurity at all nodes in the value chain remains most important for controlling and preventing ASF. Recent research from Asia, Africa, and Europe has provided science-based information that can be of value in overcoming some of the hurdles faced for implementing biosecurity in resource-limited contexts. In this narrative review we examine a selection of these studies elucidating innovative solutions such as shorter boiling times for inactivating ASF virus in swill, participatory planning of interventions for risk mitigation for ASF, better understanding of smallholder pig-keeper perceptions and constraints, modified culling, and safe alternatives for disposal of carcasses of pigs that have died of ASF. The aim of the review is to increase acceptance and implementation of science-based approaches that increase the feasibility of managing, and the possibility to prevent, ASF in resource-limited settings. This could contribute to protecting hundreds of thousands of livelihoods that depend upon pigs and enable small-scale pig production to reach its full potential for poverty alleviation and food security.

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Long‐term follow‐up of convalescent pigs and their offspring after an outbreak of acute African swine fever in Vietnam

Cited by 7 publications

References 13 publications

The study of antigen carrying and lesions observed in pigs that survived post African swine fever virus infection

The study of antigen carrying and lesions observed in pigs that survived post African swine fever virus infection

Review of the Pig-Adapted African Swine Fever Viruses in and Outside Africa

Innovative Research Offers New Hope for Managing African Swine Fever Better in Resource-Limited Smallholder Farming Settings: A Timely Update

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