Publications

Many novel emerging orbiviruses have been isolated in the past 15 years. Important viruses include Peruvian horse sickness virus (PHSV) and Yunnan orbivirus (YUOV), pathogens of equids which were originally isolated almost simultaneously from 1997 to 1999 in the People's Republic of China, Australia and Peru. YUOV has also been isolated from cattle, sheep and a dog. The isolation of YUOV from a dog is not the first case of an orbivirus being isolated from a carnivore. Bluetongue virus and African horse sickness virus were earlier detected in carnivores which fed on contaminated meat. PHSV and YUOV both offer an opportunity to study the emergence of a single pathogen in geographically distant locations, although the original point of emergence is still unidentified. PHSV has been isolated form horses with neurological disease both in Australia and in Peru (where it is now endemic). Serological and molecular diagnostic assays have been developed for these viruses to assist in their identification and diagnosis. Other orbiviruses, such as Palyam virus and equine encephalosis virus, have more recently been identified outside their geographical boundaries and may represent a threat to domesticated livestock and horses, respectively. The article also reviews four zoonotic orbivirus species (Corriparta virus, Changuinola virus, Kemerovo virus and Orungo virus) which have been identified in livestock and/or wildlife.

BACKGROUND: Biting midges of the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) cause a significant biting nuisance to equines and are responsible for the biological transmission of African horse sickness virus (AHSV). While currently restricted in distribution to sub-Saharan Africa, AHSV has a history of emergence into southern Europe and causes one of the most lethal diseases of horses and other species of Equidae. In the event of an outbreak of AHSV, the use of insecticide treated nets (ITNs) to screen equine accomodation is recommended by competent authorities including the Office International des Epizooties (OIE) in order to reduce vector-host contact. METHODS: Seven commercially avaliable pyrethroid insecticides and three repellent compounds, all of which are licensed for amateur use, were assessed in modified World Health Organization (WHO) cone bioassay trials in the laboratory using a colony line of Culicoides nubeculosus (Meigen), 1830. Two field trials were subsequently conducted to test the efficiency of treated net screens in preventing entry of Culicoides. RESULTS: A formulation of cypermethrin (0.15% w/w) and pyrethrins (0.2% w/w) (Tri-Tec 14(R), LS Sales (Farnham) Ltd, Bloxham, UK) applied to black polyvinyl-coated polyester insect screen (1.6mm aperture; 1.6mm thickness) inflicted 100% mortality on batches of C. nubeculosus following a three minute exposure in the WHO cone bioassays at 1, 7 and 14days post-treatment. Tri-Tec 14(R) outperformed all other treatments tested and was subsequently selected for use in field trials. The first trial demonstrated that treated screens placed around an ultraviolet light-suction trap entirely prevented Culicoides being collected, despite their collection in identical traps with untreated screening or no screening. The second field trial examined entry of Culicoides into stables containing horses and found that while the insecticide treated screens reduced entry substantially, there was still a small risk of exposure to biting. CONCLUSIONS: Screened stables can be utilised as part of an integrated control program in the event of an AHSV outbreak in order to reduce vector-host contact and may also be applicable to protection of horses from Culicoides during transport.

Epitopes on the surface of the foot-and-mouth disease virus (FMDV) capsid have been identified by monoclonal antibody (mAb) escape mutant studies leading to the designation of four antigenic sites in serotype A FMDV. Previous work focused on viruses isolated mainly from Asia, Europe and Latin America. In this study we report on the prediction of epitopes in African serotype A FMDVs and testing of selected epitopes using reverse genetics. Twenty-four capsid amino acid residues were predicted to be of antigenic significance by analysing the capsid sequences (n?=?56) using in silico methods, and six residues by correlating capsid sequence with serum–virus neutralization data. The predicted residues were distributed on the surface-exposed capsid regions, VP1–VP3. The significance of residue changes at eight of the predicted epitopes was tested by site-directed mutagenesis using a cDNA clone resulting in the generation of 12 mutant viruses involving seven sites. The effect of the amino acid substitutions on the antigenic nature of the virus was assessed by virus neutralization (VN) test. Mutations at four different positions, namely VP1-43, VP1-45, VP2-191 and VP3-132, led to significant reduction in VN titre (P value?=?0.05, 0.05, 0.001 and 0.05, respectively). This is the first time, to our knowledge, that the antigenic regions encompassing amino acids VP1-43 to -45 (equivalent to antigenic site 3 in serotype O), VP2-191 and VP3-132 have been predicted as epitopes and evaluated serologically for serotype A FMDVs. This identifies novel capsid epitopes of recently circulating serotype A FMDVs in East Africa.

To rapidly return to trade, countries with OIE status, FMD-free country where vaccination is not practised, have destroyed emergency vaccinated animals, raising ethical concerns with respect to social values, the environment, animal welfare and global food security. This two-part review explores whether science could support eligibility to return to previous OIE status in 3 months irrespective of vaccinate-to-live or vaccinate-to-die policies. Here, we examine the benefits of higher potency (>/= 6 PD50 ), high-purity vaccines formulated from antigen banks for emergency use, their efficacy and performance in differentiating infected from vaccinated animals (DIVA) assays for post-outbreak surveillance. From an intensive programme of research, we conclude that high-quality, higher potency vaccines are proven to reduce FMD virus (FMDV) subclinical circulation and the risk of carriers. Broader coverage than predicted by serology suggests the potential to hold a few 'key' vaccine strains improving logistics and reducing the financial burden of antigen banks. The OIE should adopt formal definitions for emergency vaccination and emergency vaccines. In terms of supportive tools, we consider that the lack of OIE recognition of DIVA tests other than those of PANAFTOSA in cattle is a shortcoming. There is need for research on maternal antibody interference with DIVA tests and on the use of such tests to establish whether greater purification of vaccines improves performance. We consider that alignment of waiting periods for vaccinate-to-live and vaccinate-to-die in OIE Code Article 8.5.9 1 b. and c. is feasible until an acceptable level of statistical certainty for surveillance or target probability of freedom is established to substantiate the absence of FMDV infection or circulation. It is surveillance intensity rather than waiting periods that establishes the risk of residual FMDV. EU Directive 2003/85/EC implicitly recognizes this, permitting derogation of the OIE waiting periods.