Randomised field trial to evaluate serological response after foot-and-mouth disease vaccination in Turkey

A systematic vaccination programme is ongoing in India to control the three prevailing serotypes (A, O, Asia1) of foot-and-mouth disease (FMD) virus. Under the programme, more than 120 million bovine (term bovine applicable to both cattle and buffalo in this study) population of 221 of the 666 districts in the country are being bi-annually vaccinated with trivalent vaccine since 2010. Although clinical disease has reduced in these districts because of the systematic vaccinations, an abrupt increase in the number of FMD cases was recorded in 2013. Hence, a longitudinal field study was conducted in the year 2014 to estimate the serological herd immunity level in bovines, the impact of systematic vaccinations and field efficacy of the vaccines used. Serum samples (n = 115 963) collected from 295 districts of the 18 states of the country were analysed to estimate antibody titres against structural proteins of the three serotypes. The efficacy of the vaccine was demonstrated in the control group (group-D) where animals of the group were identified by ear tags for the purpose of repeated sampling after vaccination. Progressive building of the herd immunity in the field after systematic vaccination was demonstrated. The mean antibody titre against the serotypes O, A and Asia1 was estimated as log 1.93 (95% CI 1.92-1.93), 2.02 (2.02-2.02) and 2.02 (2.02-2.02), respectively, in the states covered under the control programme. However, in other states herd immunity was significantly low [mean titre log 1.68 (95% CI 1.67-1.69), 1.77 (1.76-1.78) and 1.85 (1.84-1.86) against the three serotypes]. Inverse relationship between the herd immunity and FMD incidences was observed the states following different vaccination practices. The study helped in demarcation of FMD risk zones in the country with low herd immunity. Estimation of herd immunity kinetics in the field helped in refining the vaccination schedule under the control programme.

Section: Discussionsupporting

confidence: 80%

Herd Immunity Against Foot-and-Mouth Disease Under Different Vaccination Practices in India

Sharma

Mahajan

Matura

et al. 2016

“…An important over‐simplification of many studies predicting the benefits of control is a failure to incorporate the variable effectiveness of FMD control programmes (Knight‐Jones et al., , ; Knight‐Jones et al., a, Lyons et al., ; Elnekave et al., ; Woolhouse et al., ; Lyons et al., ). Two critical factors are (i) the variable potency and quality of vaccines used in endemic settings (Metwally et al., In press) and (ii) the limited application of biosecurity and sanitary control measures (Young et al., ).…”

Section: Fmd Smallholder Impact: What Do We Know and What Don't We Know?mentioning

confidence: 99%

“…Disease control in these settings may be heavily reliant upon vaccination alone. But FMD vaccines used in endemic countries typically provide short‐lived and limited protection (Knight‐Jones et al., ). Furthermore, mass vaccination of all cattle and pigs, and possibly sheep and goats, every 6 months, may be unrealistic in developing countries with poor infrastructure and numerous smallholdings (Knight‐Jones et al., ).…”

Section: Feasibility Of Controlmentioning

confidence: 99%

Foot-and-Mouth Disease Impact on Smallholders - What Do We Know, What Don't We Know and How Can We Find Out More?

Knight-Jones

McLaws²,

Rushton

2016

SummaryFoot‐and‐mouth disease (FMD) endemic regions contain three‐quarters of the world's FMD susceptible livestock and most of the world's poor livestock keepers. Yet FMD impact on smallholders in these regions is poorly understood. Diseases of low mortality can exert a large impact if incidence is high. Modelling and field studies commonly find high FMD incidence in endemic countries. Sero‐surveys typically find a third of young cattle are sero‐positive, however, the proportion of sero‐positive animals that developed disease, and resulting impact, are unknown. The few smallholder FMD impact studies that have been performed assessed different aspects of impact, using different approaches. They find that FMD impact can be high (>10% of annual household income). However, impact is highly variable, being a function of FMD incidence and dependency on activities affected by FMD. FMD restricts investment in productive but less FMD‐resilient farming methods, however, other barriers to efficient production may exist, reducing the benefits of FMD control. Applying control measures is costly and can have wide‐reaching negative impacts; veterinary‐cordon‐fences may damage wildlife populations, and livestock movement restrictions and trade bans damage farmer profits and the wider economy. When control measures are ineffective, farmers, society and wildlife may experience the burden of control without reducing disease burden. Foot‐and‐mouth disease control has benefitted smallholders in South America and elsewhere. Success takes decades of regional cooperation with effective veterinary services and widespread farmer participation. However, both the likelihood of success and the full cost of control measures must be considered. Controlling FMD in smallholder systems is challenging, particularly when movement restrictions are hard to enforce. In parts of Africa this is compounded by endemically infected wildlife and limited vaccine performance. This paper reviews FMD impact on smallholders in endemic countries. Significant evidence gaps exist and guidance on the design of FMD impact studies is provided.

“…This is an important but neglected area. Some field studies have used FMDV structural protein antibody titres as a proxy for protection, which allows easy comparison of different vaccine groups and schedules (Lee et al., ; Knight‐Jones et al., ), but inevitably fails to assess protection itself and other aspects of immunity. In Argentina, population immunity is estimated through field surveys of protective antibody levels as part of routine post‐vaccination monitoring.…”

Section: Literature Reviewmentioning

confidence: 99%

Global Foot-and-Mouth Disease Research Update and Gap Analysis: 3 - Vaccines

Robinson

Knight-Jones

Charleston

et al. 2016

SummaryThis study assessed research knowledge gaps in the field of FMDV (foot-andmouth disease virus) vaccines. The study took the form of a literature review combined with research updates collected in 2014 from 33 institutes from across the world. Findings were used to identify priority areas for future FMD vaccine research. Vaccines play a vital role in FMD control, used both to limit the spread of the virus during epidemics in FMD-free countries and as the mainstay of disease management in endemic regions, particularly where sanitary controls are difficult to apply. Improvements in the performance or cost-effectiveness of FMD vaccines will allow more widespread and efficient disease control. FMD vaccines have changed little in recent decades, typically produced by inactivation of whole virus, the quantity and stability of the intact viral capsids in the final preparation being key for immunogenicity. However, these are exciting times and several promising novel FMD vaccine candidates have recently been developed. This includes the first FMD vaccine licensed for manufacture and use in the USA; this adenovirus-vectored FMD vaccine causes in vivo expression of viral capsids in vaccinated animals. Another promising vaccine candidate comprises stabilized empty FMDV capsids produced in vitro in a baculovirus expression system. Recombinant technologies are also being developed to improve otherwise conventionally produced inactivated vaccines, for example, by creating a chimeric vaccine virus to increase capsid stability and by inserting sequences into the vaccine virus for desired antigen expression. Other important areas of ongoing research include enhanced adjuvants, vaccine quality control procedures and predicting vaccine protection from immune correlates, thus reducing dependency on animal challenge studies. Globally, the degree of independent vaccine evaluation is highly variable, and this is essential for vaccine quality. Previously neglected, the importance of evaluating vaccination programme effectiveness and impact is increasingly being recognized.