ABSTRACT
Foot-and-mouth disease (FMD) is endemic in Eastern Africa with circulation of multiple serotypes of the virus in the region. Most of the outbreaks are caused by serotype O followed by serotype A. The lack of concerted FMD control programmes in Africa has provided little incentive for vaccine producers to select vaccines that are tailored to circulating regional isolates creating further negative feedback to deter the introduction of vaccine-based control schemes. In this study a total of 80 serotype O FMD viruses (FMDV) isolated from 1993 to 2012 from East and North Africa were characterized by virus neutralisation tests using bovine antisera to three existing (O/KEN/77/78, O/Manisa and O/PanAsia-2) and three putative (O/EA/2002, O/EA/2009 and O/EA/2010) vaccine strains and by capsid sequencing. Genetically, these viruses were grouped as either of East African origin with subdivision into four topotypes (EA-1, 2, 3 and 4) or of Middle-East South Asian (ME-SA) topotype. The ME-SA topotype viruses were mainly detected in Egypt and Libya reflecting the trade links with the Middle East countries. There was good serological cross-reactivity between the vaccine strains and most of the field isolates analysed, indicating that vaccine selection should not be a major constraint for control of serotype O FMD by vaccination, and that both local and internationally available commercial vaccines could be used. The O/KEN/77/78 vaccine, commonly used in the region, exhibited comparatively lower percent in vitro match against the predominant topotypes (EA-2 and EA-3) circulating in the region whereas O/PanAsia-2 and O/Manisa vaccines revealed broader protection against East African serotype O viruses, even though they genetically belong to the ME-SA topotype.
Subject(s)
Antigens, Viral/genetics , Antigens, Viral/immunology , Foot-and-Mouth Disease Virus/isolation & purification , Foot-and-Mouth Disease/prevention & control , Serogroup , Viral Vaccines/immunology , Africa, Eastern/epidemiology , Animals , Capsid Proteins/genetics , Cattle , Disease Outbreaks/prevention & control , Foot-and-Mouth Disease/epidemiology , Foot-and-Mouth Disease Virus/classification , Foot-and-Mouth Disease Virus/genetics , Foot-and-Mouth Disease Virus/immunology , Neutralization Tests , Phylogeny , RNA, Viral/genetics , Sequence Analysis, DNAABSTRACT
Foot-and-mouth disease (FMD) is endemic in Southeast Asia (SEA) and East Asia with circulation of multiple serotypes and multiple genotypes within each serotype of the virus. Although countries like Japan and South Korea in the Far East were free of FMD, in 2010 FMD serotype O (O/Mya-98) outbreaks were recorded and since then South Korea has experienced several FMD outbreaks despite regular vaccination. In this study a total of 85 serotype O FMD viruses (FMDV) isolated from 2007 to 2012 from SEA, East Asia and Far East were characterized by virus neutralisation tests using antisera to four existing (O/HKN/6/83, O/IND/R2/75, O/SKR/2010 and O/PanAsia-2) and one putative (O/MYA/2009) vaccine strains, and by full capsid sequencing. Serological studies revealed broad cross-reactivity with the vaccine strains; O/PanAsia-2 exhibited a good match with 95.3%, O/HKN/6/83 with 91.8%, O/IND/R2/75 with 80%, and the putative strain O/MYA/2009 with 89.4% isolates employed in this study. Similarly O/PanAsia-2 and O/IND/R2/75 vaccines showed a good match with all eight viruses belonging to O-Ind-2001d sublineage whereas the vaccines of O/Mya-98 lineage, O/MYA/2009 and O/SKR/2010 exhibited the lowest match indicating their unsuitability to protect infections from O-Ind-2001d viruses. A Bayesian analysis of the capsid sequence data indicated these circulating viruses (nâ¯=â¯85) to be of either SEA or Middle East-South Asian (ME-SA) topotype. The ME-SA topotype viruses were mainly detected in Lao PDR, Vietnam, Myanmar and Thailand reflecting the trade links with the Indian subcontinent, and also within the SEA countries. Implications of these results in the context of FMD control in SEA and East Asian countries are discussed.
Subject(s)
Foot-and-Mouth Disease Virus/immunology , Foot-and-Mouth Disease Virus/isolation & purification , Foot-and-Mouth Disease/prevention & control , Serogroup , Viral Vaccines/immunology , Animals , Antigens, Viral/immunology , Asia, Southeastern/epidemiology , Bayes Theorem , Capsid Proteins/genetics , Cattle , Cross Reactions , Disease Outbreaks/prevention & control , Asia, Eastern/epidemiology , Foot-and-Mouth Disease/epidemiology , Foot-and-Mouth Disease/immunology , Neutralization Tests , Phylogeny , Vaccination , Viral Vaccines/isolation & purificationABSTRACT
Peste des petits ruminants is responsible for an economically important plague of small ruminants that is endemic across much of the developing world. Here we describe the detection and characterisation of a PPR virus from a recent outbreak in Tamil Nadu, India. We demonstrate the isolation of PPR virus from rectal swab and highlight the potential spread of disease to in-contact animals through faecal materials and use of faecal material as non-invasive method of sampling for susceptible wild ruminants. Finally we have performed a comprehensive 'multi-gene' assessment of lineage IV isolates of PPRV utilising sequence data from our study and publically available partial N, partial F and partial H gene data. We describe the effects of grouping PPRV isolates utilising different gene loci and conclude that the variable part of N gene at C terminus gives the best phylogenetic assessment of PPRV isolates with isolates generally clustering according to geographical isolation. This assessment highlights the importance of careful gene targeting with RT-PCR to enable thorough phylogenetic analysis.
