Bluetongue vaccines: the past, present and future

Abstract

Bluetongue (BT) is a noncontagious and arboviral disease of both domestic and wild ruminants. The disease is enzootic in areas where reservoirs (cattle and wild ruminants) and vectors exist for the BT virus (BTV). A total of 24 BTV serotypes have been recognized worldwide. The major control measures include restriction of animal movement, vector control applying insecticides, slaughter of infected animals and vaccination. Prophylactic immunization of sheep against BT is the most practical and effective control measure to combat BT infection. At present, attenuated vaccines are used in the Republic of South Africa, the USA and other countries. However, EU countries were using attenuated vaccines, only recently shifting to inactivated vaccines owing to their safety and efficacy. In India, inactivated vaccines are in experimental stages and are expected to be on the market shortly. Inactivated vaccines generate serotype-specific long-lasting protective immunity after two injections, and may help in controlling epidemics. Differentiating infected from vaccinated animals (DIVA) is theoretically possible with inactivated vaccines but has not yet been developed, whereas the attenuated live vaccines are not candidates for DIVA. Attenuated live vaccines are efficacious but safety issues are of great concern. New-generation vaccines (subunit, virus-like particles, core-like particles and vectored) can be employed for DIVA. Recombinant vaccines, which generate cross-protection against multiple BTV serotypes, have great potential in BT vaccine regimens. Furthermore, new-generation vaccines are safe and efficacious experimentally, but large-scale field trials are warranted. Alternative areas, such as antivirals, siRNA, interferon and nanotechnology, may be of future use in the control of BT. We give an overview of BT vaccines, starting from conventional to recent developments, and their feasibility in controlling BT infection.

An experimental subunit vaccine based on Bluetongue virus 4 VP2 protein fused to an antigen-presenting cells single chain antibody elicits cellular and humoral immune responses in cattle, guinea pigs and IFNAR(−/−) mice

“…The eradication of BTV from enzootic areas may not be easy, but, in non-enzootic areas, vaccination with inactivated vaccine incorporating the prevalent serotypes is advantageous [30]. However, inactivated vaccines are available in a few countries, including the European Union, India, the USA and China [30].…”

Clinical and Laboratory Picture in Calves in Rearing with Incidence Bluetongue

“…In cattle and goats, BTV infections are usually subclinical, whereas natural infection of BTV-8 [6,7,16,25] and experimental infection with some BTV strains [26] of pregnant cows during early gestation may result in congenital brain defects, in particular hydranencephaly of the foetuses or calves [27]. Infection with BT in pregnant animals, causes abortions, giving birth to stillborn offsprings or malformated calves and lambs depending on the stage gravidity [2,5,27,28].…”

Current and next-generation bluetongue vaccines: Requirements, strategies, and prospects for different field situations

“…Officially, MLVs for other serotypes were never used in Europe but have been detected, and are likely introduced via unknown introduction routes (De Clercq et al, 2009;van Rijn et al, 2012). In several parts of the world, such as the USA, Turkey, Africa, and India, MLVs are still used to protect the ruminant population against BT (Bhanuprakash et al, 2009;McVey & MacLachlan, 2015). However, uncontrolled spread of MLVs is not desired if BT eradication is the ultimate goal.…”