FMD CURRENT STATUS IN SOUTHEAST ASIA AND CHINA

Yu Qiu, Ronello AbilaOIE Sub-Regional Representation for South-East Asia,

c/o DLD, 69/1 Phaya Thai Road,Ratchathewi 10400, Bangkok, Thailand

ABSTRACT

This paper discusses the current status of FMD as an endemic disease in China and mainland Southeast Asia, its three serotypes and distinct topotypes and their genetic diversity. It also emphasizes the need for official cross control on animal movements which is important in combatting this transboundary animal disease.

Key words: Foot-and-Mouth Disease, FMD, serotype virus, Transboundary Animal Diseases

INTRODUCTION

FMD is endemic in China and in mainland Southeast Asia (SEA) comprising of Cambodia, Lao PDR, Peninsular Malaysia, Myanmar, Thailand and Vietnam, with reports of regular outbreaks. The island states comprising of Brunei Darussalam, Indonesia, the Philippines, and Singapore, as well as East Malaysia, are recognized by OIE as FMD free countries/zones without vaccination.

Serotype O, A and Asia 1 are the only three serotypes endemic to SEA and China. Serotype O is the most common circulating serotype with three distinct topotypes, consisting of the SEA topotype, the ME-SA topotype and the Cathay (pig-adapted) topotype. First reported in Myanmar in 1998, the Mya-98 strain of the SEA topotype is widely spread in this region. The ME-SA topotype, which originate from India, can be further divided into several sublineages (also called as strains), such as PanAsia, Ind2001 (a, b, c, and d), and Iran2001. The PanAsia strain was introduced into SEA in the late 1990s and into China in 2009/2010. Outbreaks caused by this strain continue to occur widely in this region and have further affected South Korea, Japan, Mongolia, and Russia. Importantly, the Ind2001d strain, indigenous in the Indian subcontinent which has further expanded to the Middle East and North Africa during 2013 to 2014, has recently been identified in SEA for the first time in its history. Outbreaks due to this strain were reported in Lao PDR in April/May 2015 and in Vietnam in September/October 2015. The first FMDV strain belonging to the Cathay topotype was isolated from pigs in Hong Kong in 1970s and shortly it became established in Hong Kong and Southern China. In the following decades, the Cathay topotype has been confirmed in several SEA countries, including Malaysia, the Philippines, Taiwan, Thailand and Vietnam. In the more recent years, the Cathay topotype is reported on a very sporadic basis in SEA, with the latest outbreak in Thailand in 2012 and Vietnam in 2015 (Table 1).

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Table 1. FMDV strains detected in SEA and China during 2011-2015, as characterized by World and/or Regional Laboratory for FMD.

Country Virus Lineage 2011 2012 2013 2014 2015Cambodia

Serotype O + + + + +O/SEA/Mya98 +O/ME-SA/PanAsia + + +O/ME-SA/Ind2001dO/CathaySerotype A + +A/Asia/Sea97 +

China Serotype O + + + +O/SEA/Mya98 + + + +O/ME-SA/PanAsia + + +O/ME-SA/Ind2001dO/CathaySerotype A + + +A/Asia/Sea97 + + +

Lao PDR Serotype O + + + + +O/SEA/Mya98 + + + +O/ME-SA/PanAsia + +O/ME-SA/Ind2001d +O/CathaySerotype A + +A/Asia/Sea97 + +

Malaysia Serotype O + + + + +O/SEA/Mya98 + + + +O/ME-SA/PanAsiaO/ME-SA/Ind2001dO/CathaySerotype A + + + +A/Asia/Sea97 + + + +

Myanmar

Serotype O + + + + +O/SEA/Mya98 +O/ME-SA/PanAsiaO/ME-SA/Ind2001dO/CathaySerotype A +A/Asia/Sea97 +

Thailand Serotype O + + + + +O/SEA/Mya98 + + + + +O/ME-SA/PanAsia + + +O/ME-SA/Ind2001dO/Cathay +Serotype A + + + + +A/Asia/Sea97 + + + + +

Viet Nam Serotype O + + + + +O/SEA/Mya98 + +O/ME-SA/PanAsia + + + + +O/ME-SA/Ind2001d +O/Cathay +Serotype A + + + +A/Asia/Sea97 + + + +

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+: the FMDV lineage present in the country.Note: data were based on the genotyping results from the Pirbright Institute (http://www.wrlfmd.org/fmd_genotyping/asia.html) and country reports presented at the 18th - 22nd  Meetings of the OIE Sub-Commission for FMD in South-East Asia and China.

GENETIC DIVERSITY

In contrast to the various topotypes within the serotype O, the Asia topotype is the only topotype of serotype A identified in SEA. The serotype A virus is widespread in this region, but it had never been isolated in Myanmar until August/September 2015, whereas specific serotype A antibodies were detected in buffalo sera collected during 2008 and 2009 from several states in Myanmar. The serotype A isolates in Myanmar are very closely related (99.8% identity in VP1 nucleotide sequences) to the isolates recovered in China and Russia in 2013 and those recovered in Thailand in 2014-15, suggesting that these viruses share a common recent ancestor and that the Myanmar serotype A outbreaks unlikely represent a new incursion of FMDV from India.

The phylogenetic analysis of serotype O and A FMDVs collected in SEA from 2012 to 2015 shows that genetic diversity exists within both serotypes. Based on the VP1 gene, the serotype O viruses were grouped into eight clusters, and the serotype A viruses were grouped into six clusters. Viruses of the same cluster can often be found in various neighboring countries, suggesting significant epidemiological links among them.

Serotype Asia 1 has not been detected in the region in recent years. It was last detected in Lao PDR in 1999, Myanmar in 2001, Malaysia in 2005, Thailand in 1998, Cambodia in 1997, Vietnam in 2008 and China in 2009. Although initially serotype Asia 1 was suspected in two of the samples from Cambodia in 2015, no evidence of the presence of this serotype could be found.

CONCLUSION

The free grazing system and irregular animal movement pattern are considered as significant risk parameters in the spread of FMD. Myanmar is generally considered as a key country in terms of regional FMD epidemiology, due to its significant cattle population and their significant export flow into other SEA countries and China. Thailand, Cambodia and Lao PDR are transiting countries, where cattle of Myanmar, India or Bangladesh origin pass through before entering Malaysia, Vietnam and China. Indeed, matching the pathways of FMD virus dissemination and animal movements in SEA reveals a good agreement: the clustering of outbreaks in southern Thailand and northern Malaysia fits the flow of cattle movement, which is most obvious prior to Malaysia’s religious festivals; the clustering of outbreaks in the southern part of Cambodia and Vietnam also follows the flow of cattle movement. All these reinforce the need for strong official controls on cross-border animal movements, as well as for enhancing multinational cooperative measures on FMD control.

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