Foot-and-mouth disease (FMD) is a transboundary, economically devastating and highly contagious viral disease of livestock, most importantly cattle, buffalo and pig. The disease also affects goats, sheep, wild ruminant species and elephants. The causative FMD virus is antigenically diverse having seven distinct serotypes and many variants within them. Being a single stranded RNA virus, it confirms the quasispecies nature with emergences and reemergences of different genetic lineages with altered antigenicity within the serotypes, making vaccination based control programme a high cost effective, time consuming and difficult to achieve. As per the OIE and FAO, the disease is a major threat to food security of the world, and particularly the countries having the disease are more prone to food insecurity. Further, FMD free status is an indicator of development, and all developed countries are free from it. The disease is endemic in India and three serotypes of the virus viz; O, A and Asia1 are circulating. Annual direct loss due to FMD in India has been estimated at Rs. 20,000 crores. Many countries in the world are now free from FMD with or without vaccination and presence of the disease in other neighboring countries is a major threat to them. Countries having FMD face trade barrier posed by FMD free countries, causing heavy economic loss to the livestock industry. Progressive control pathway has been developed by FAO for global eradication of FMD. Vaccination based FMD control programme is in operation in India which involves biannual vaccinations of all cattle and buffaloes in selected areas, regular active surveillance and antibody monitoring in vaccinated population with the objective of creating FMD free zones. At present, the disease occurrence, severity of the clinical disease and number of outbreaks have progressively and substantially declined in the control zones as a result of last 10 rounds of vaccination with an oil adjuvanted trivalent inactivated vaccine. In this review, FMD scenario in India and in the world is briefed. Besides, the measures taken for the control and eradication of this devastating disease is presented. Besides, the initial success achieved through the FMD control programme in India, a road map for the control and eradication of FMD at national level is discussed.

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SummaryThe goal of this study was to characterize the properties and duration of the foot-

Foot-and-mouth disease (FMD) is an important transboundary disease with substantial economic impacts. Although between-herd transmission of the disease has been well studied, studies focusing on within-herd transmission using farm-level outbreak data are rare. The aim of this study was to estimate parameters associated with within-herd transmission, host physiological factors and FMD virus (FMDV) persistence using data collected from an outbreak that occurred at a large, organized dairy farm in India. Of 1,836 regularly vaccinated, adult dairy cattle, 222 had clinical signs of FMD over a 39-day period. Assuming homogenous mixing, a frequency-dependent compartmental model of disease transmission was built. The transmission coefficient and basic reproductive number were estimated to be between 16.2-18.4 and 67-88, respectively. Non-pregnant animals were more likely to manifest clinical signs of FMD as compared to pregnant cattle. Based on oropharyngeal fluid (probang) sampling and FMDV-specific RT-PCR, four of 36 longitudinally sampled animals (14%) were persistently infected carriers 10.5 months post-outbreak. There was no statistical difference between subclinical and clinically infected animals in the duration of the carrier state. However, prevalence of NSP-ELISA antibodies differed significantly between subclinical and clinically infected animals 12 months after the outbreak with 83% seroprevalence amongst clinically infected cattle compared to 69% of subclinical animals. This study further elucidates within-herd FMD transmission dynamics during the acute-phase and characterizes duration of FMDV persistence and seroprevalence of FMD under natural conditions in an endemic setting.

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Foot-and-mouth disease (FMD) is a highly contagious and economically devastating disease of livestock, primarily affecting cattle, buffalo and pigs. FMD virus serotypes O, A and Asia1 are prevalent in India and systematic efforts are on to control and eventually eradicate the disease from the country. FMD epidemiology is complex due to factors like co-circulation, extinction, emergence and re-emergence of genotypes/lineages within the three serotypes, animal movement, diverse farm practices and large number of susceptible livestock in the country. Systematic vaccination, prompt diagnosis, strict biosecurity measures, and regular monitoring of vaccinal immunity and surveillance of virus circulation are indispensible features for the effective implementation of the control measures. Availability of suitable companion diagnostic tests is very important in this endeavour. In this review, the diagnostic assays developed and validated in India and their contribution in FMD control programme is presented.

In this study we describe the adaptive changes fixed on the capsid of several foot-and-mouth disease virus serotype A strains during propagation in cell monolayers. Viruses passaged extensively in three cell lines (BHK-21, LFBK and IB-RS-2) consistently gained positively charged amino acids in the putative heparin-sulfate-binding pocket (VP2 bE-bF loop, VP1 C-terminus and VP3 b-B knob) surrounding the fivefold symmetry axis (VP1 bF-bG loop) and at other discrete sites on the capsid (VP3 bG-bH loop, VP1 C-terminus, VP2 bC strand and VP1 bG-bH loop). A lysine insertion in the VP1 bF-bG loop of two of the BHK-21-adapted viruses supports the biological advantage of positively charged residues acquired in cell culture. The charge transitions occurred irrespective of cell line, suggesting their possible role in ionic interaction with ubiquitous negatively charged cell-surface molecules such as glycosaminoglycans (GAG). This was supported by the ability of the cell-culture-adapted variants to replicate in the integrin-deficient, GAG-positive CHO-K1 cells and their superior fitness in competition assays compared with the lower passage viruses with WT genotypes. Substitutions fixed in the VP1 bG-bH loop ("3, "2 and +2 'RGD' positions) or in the structural element known to be juxtaposed against that loop (VP1 bB-bC loop) suggest their possible role in modulating the efficiency and specificity of interaction of the 'RGD' motif with a v -integrin receptors. The nature and location of the substitutions described in this study could be applied in the rapid cell culture adaptation of viral strains for vaccine production.

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