Introduction of African swine fever (ASF)
activities in Vietnam
Hu Suk Lee
International Livestock Research Institute (ILRI)
2020 International Workshop on Veterinary Epidemiology
South Korea, 17 June 2020

Outline
• ASF situations in Vietnam
• Risk communication & interventions
• ASF simulation modelling research

Biography
Education
PhD (2013): Epidemiology, Vet school, Purdue Univ, USA
Master (2009): Epidemiology, Royal Vet. College & LSHTM, UK
DVM (2005): Vet. School, Jeju National University, South Korea
International working experience
ILRI: 2015-Present (Vet. epidemiologist), SEA regional office Hanoi
FAO: 2016 (Consultant), SEA regional office Bangkok
OIE: 2013-2014 (Vet. epidemiologist), Paris
KOICA: 2005-2007 (Veterinary officer), Tanzania

ASF situations

ASF outbreaks in Asia

Pig production in
Vietnam
• Pig population:
• Before ASF introduction (Feb 2019): > 30 mil.
• Update in August 2019: 25 mil. (>20% death/culling)
• Breeding pigs:
• Before ASF introduction (Feb 2019): 3.8 mil. (sows)
• Update in August 2019: 2.7 mil. (sows)
Resource: Department of animal
health, MARD

First detection of ASF outbreak
• Hung Yen province: About 60km from Hanoi and 217km
from Tan Thanh border gate to China
• Family farm and 100% industrial barn
Resource: Prof. Phan from UNUA

Genotype II
Genotype XV
Genotype X
Genotype IX
Fig. 1. Phylogenetic tree based on P54 gene of ASF.
Vietnamese ASFV strains; Chinese ASFV strains
1. Hung Yen
2. Ha Noi
3. Thai Binh
4. Hai Duong
5. Hoa Binh
Vietnamese ASFV
strains shared 100% at
both nt and aa identity
compared with Chinese
ASFV strains
Genetic characterization of ASF virus
Resource: Prof. Phan from UNUA

Evolution of the outbreaks since the first case
As of 26 April 2020, 44/63 provinces have not had any outbreaks
for more than 30 days
Resource: FAO
Cumulative number of affected communes/week
Provinces with no new
ASF outbreaks for more
than 30 days

Potential risk factors for ASF in Vietnam
• Illegal human and vehicle movements cross the long
borders
• Carry meats and food products etc.
• low biosecurity; few outbreaks occurred in commercial
farms
• Urgently, selling pigs through illegal means during
the outbreaks, especially Tet holiday period
• Insect vectors (?) (ticks, rodents etc.) / wild boars (?)

Current control measures
• Early detection, culling, disinfection and compensation
• Small farms: infected farms are only culled, but neighboring
farms without any suspected cases are not culled and closely
monitored
• Large farms: all pigs of infected pens are only culled and pigs
in other pens are monitored or slaughtered for self-
consumption.
• Movement control
• Biosecurity and re-stocking
• Requested all big farms have to apply strict biosecurity
measures and frequently cleaning and disinfection of all risk
factors
• Re-stocking only after the outbreaks are resolved for at least

Risk communication

Risk
communication
• Multi-collaborations among
the Department of Animal
Health and other international
organizations
• Key actors: traders, authorities,
general public and pig farmers
for biosecurity guidelines

Risk communication: Media interviews
https://thediplomat.com/2019/07/the-battle-to-curb-swine-
fever-in-southeast-asia/

Risk communication: High-level meeting

Intervention activities

Intervention activities
• Study site: Son La province – Maison district
• Main objectives:
 To improve animal health management for livestock farmers
 To strengthen the capacity of Animal health professionals
• Major national partners:
 National Institute of Veterinary Research (NIVR)
 Sub-DAH and local authority
• Workshop/training (participatory approach)
 Farmers: biosecurity, disinfection and animal
health/management
 Animal health professionals: outbreak investigation, data
recording, vaccine / drug use, risk communication etc.

Intervention activities

Intervention activities

Simulation modelling

A simple disease model
Infectious diseases
S I R
RISN 
A simple disease model
𝑑𝑆
𝑑𝑡
= −𝛽SI
𝛽 𝛾
𝑑𝐼
𝑑𝑡
= 𝛽SI − γI
𝑑𝑅
𝑑𝑡
= γI

Direct transmission Indirect transmission
Animal to animal contact Movement of vehicles, equipment
and personnel
Reproductive transmission –
Trichomoniasis and PRRS
Food-borne – Salmonella
blood – virus disease Vectors – Rift Valley Fever and JE
Skin to skin – FMD Airborne – Influenza
Sneezes, coughs – swine influenza Environmental reservoirs – water
and soil
Examples of transmission routes

• Canada / US joint project working on the
development of the North American Animal Disease
Spread Model (NAADSM): http://www.naadsm.org/
• A stochastic disease-state-transition computer
simulation model by user-defined parameters
• To simulates several methods of controlling diseases
(such as quarantine, movement restriction,
depopulation and vaccination)
Simulation model: background

Simulation model of ASF
• Total farms in the RRD: 7,882
• Small<100 pigs; medium≥100; large
≥ 1000
• Probabilities of infection transfer
between farms
 direct / indirect contact
• Contact distance between farms

Simulation scenarios of ASF
• Contact rates: mean contact rate/week
-> Poisson distribution
 Direct contact: introduction of new pigs
 Indirect contact: vehicles, human
movements and sharing equipment,
every 6 months
• What if one farm become infected?
• What if movement restriction is
imposed? (by 25%, 50% and 75%)

Results for simulation scenarios
Sensitivity analysis of simulation model
Movement restrictions on the contact rates

Conclusion & discussion
• This study offers valuable insight into how ASF virus can be
transmitted via direct and indirect contact
control
• The enforcement of movement restrictions is an effective control
measure if implemented as soon as outbreaks are confirmed
• Movement restrictions need to reach at least between 50% and
75% of the population, and they need to be applied in a timely
manner
• Cost-benefit analysis needs to be conducted in the future

Research Information
• Challenge trials of ASF
 Gene expression analysis
 Clinical assessment
• Epi. farm investigation of ASF
 Identification of risk factors
• A new zoonotic report (COVID-19)
will be released on 5 July
https://www.unenvironment.org/news-and-
stories/story/preventing-pandemics-new-report-
zoonotics-be-released-july

Acknowledgments
Prof. Phan (Vietnam
National University of
Agriculture)
Dr. Long (Department
of Animal Health,
MARD)
NIVR team -
MARD

This presentation is licensed for use under the Creative Commons Attribution 4.0 International Licence.
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