Satya Parida

Vaccination against foot-and-mouth disease virus: strategies and effectiveness

Although present conventional foot-and-mouth disease (FMD) vaccines can prevent clinical disease, protection is short lived (∼6 months), often requiring frequent revaccination for prophylactic control, and vaccination does not induce rapid protection against challenge or prevent the development of the carrier state. Furthermore, it is clear that the clinical protection depends upon the length of immunization and the duration of exposure/challenge methods. This review summarizes the present and future strategies for FMD control in endemic and FMD-free countries, the effectiveness of FMD vaccines in cattle, sheep and pigs, new methods for selecting vaccine strains, suggestions for alternative methods of vaccine testing, suggestions for the development of new-generation efficacious vaccines and their companion tests to differentiate infection in vaccinated animals.

Visibility and incidence of respiratory diseases during the 1998 haze episode in Brunei Darussalam

— Air pollution episodes as a result of forest fires in Brunei Darussalam and neighbouring regions have reached hazardous levels in recent years. Such episodes are generally associated with poor visibility and air quality conditions. In the present study, data on PM10 (particulate matter of size less than 10 microns) and CO in Brunei Darussalam have been considered to study the incidence of respiratory diseases whereas data on relative humidity (RH) in addition to PM10 have been used to explain the visibility with a particular emphasis on haze episode during 1998.¶Initial exploratory analysis indicates significant correlation of visibility with PM10 and RH. An attempt has been made to explain visibility on the basis of PM10 and RH using multiple linear regression analysis. The regression model shows that PM10 and RH are two significant factors affecting the visibility at a given site. Further, canonical correlation, a multivariate method of analysis, has been used to explain the incidence of respiratory diseases as a function of air quality during the haze period. The results indicate that PM10 and CO levels during the haze period have a significant bearing on the incidence of respiratory diseases (Asthma, Acute Respiratory Infections and Influenza (ARII)).

Peste des petits ruminants

Peste des petits ruminants virus causes a highly infectious disease of small ruminants that is endemic across Africa, the Middle East and large regions of Asia. The virus is considered to be a major obstacle to the development of sustainable agriculture across the developing world and has recently been targeted by the World Organisation for Animal Health (OIE) and the Food and Agriculture Organisation (FAO) for eradication with the aim of global elimination of the disease by 2030. Fundamentally, the vaccines required to successfully achieve this goal are currently available, but the availability of novel vaccine preparations to also fulfill the requisite for differentiation between infected and vaccinated animals (DIVA) may reduce the time taken and the financial costs of serological surveillance in the later stages of any eradication campaign. Here, we overview what is currently known about the virus, with reference to its origin, updated global circulation, molecular evolution, diagnostic tools and vaccines currently available to combat the disease. Further, we comment on recent developments in our knowledge of various recombinant vaccines and on the potential for the development of novel multivalent vaccines for small ruminants.

Strategies for differentiating infection in vaccinated animals (DIVA) for foot-and-mouth disease, classical swine fever and avian influenza

The prophylactic use of vaccines against exotic viral infections in production animals is undertaken exclusively in regions where the disease concerned is endemic. In such areas, the infection pressure is very high and so, to assure optimal protection, the most efficient vaccines are used. However, in areas considered to be free from these diseases and in which there is the possibility of only limited outbreaks, the use of Differentiation of Infected from Vaccinated Animals (DIVA) or marker vaccines allows for vaccination while still retaining the possibility of serological surveillance for the presence of infection. This literature review describes the current knowledge on the use of DIVA diagnostic strategies for three important transboundary animal diseases: foot-and-mouth disease in cloven-hoofed animals, classical swine fever in pigs and avian influenza in poultry.

Peste des petits ruminants: a suitable candidate for eradication?

This year will see the final announcement, accompanied by much justifiable celebration, of the eradication from the wild of rinderpest, the ‘cattle plague’ that has been with us for so many centuries. The only known rinderpest virus (RPV) remaining is in a relatively small number of laboratories around the world, and in the stockpiles of vaccine held on a precautionary basis. As we mark this achievement, only the second virus ever eradicated through human intervention, it seems a good time to look at rinderpests less famous cousin, peste des petits ruminants (‘the plague of small ruminants’) and assess if it should, and could, also be targeted for global eradication.

Efficient production of foot-and-mouth disease virus empty capsids in insect cells following down regulation of 3C protease activity.

Highlights ► Efficient expression of FMDV empty capsids in insect cells after moderation of 3C protease action. ► Expression cassette productive in multiple insect cell lines. ► Empty capsids visualised by transmission electron microscopy. ► Empty capsids react with wide range of positive sera as well as authentic virus. ► Efficient empty capsid synthesis may allow development as a vaccine.

Emergency vaccination of sheep against foot-and-mouth disease: Significance and detection of subsequent sub-clinical infection

This study has quantified the level of foot-and-mouth disease virus (FMDV) replication and shedding in vaccinated sheep and correlated this to the severity of clinical signs, the induction of antibodies against FMDV non-structural proteins (NSPs) and the transmission of virus to in-contact vaccinated sentinel sheep. To mimic an emergency vaccination regime in the field, sheep were vaccinated with O(1) Manisa vaccine and 4 or 10 days later were indirectly challenged with aerosols from O(1) UKG FMDV infected pigs. Vaccinated and control unvaccinated sheep were monitored for a minimum of 39 days post-challenge. The vaccinated sheep became sub-clinically infected, with reduced virus replication and excretion compared to unvaccinated and clinically infected sheep. Seroconversion to NSP was weak and transient in sheep in which virus replication was of low level and short duration. Virus transmission from vaccinated sub-clinically infected sheep to introduced vaccinated sentinels was not sufficient to cause NSP seroconversion or significant virus shedding. 10% of 10 days and 20% of 4 days vaccinated sheep were virus carriers at greater than 28 days post-challenge compared to 37.5% in the unvaccinated and clinically infected sheep. These results suggest that the low levels of virus replication likely if an effective vaccine is administered at least 4 days prior to challenge exposure are unlikely to result in the spread of infection even under intensive management conditions. Although it may be difficult to detect this infection by serosurveillance, the significance of missing it is likely to be low and the main value of such testing will be to detect undisclosed clinical infection resulting from lack of observation or from exposure to virus before or very soon after vaccination or from vaccine failure due to maladministration or inappropriate strain selection.

Serological Survey for Foot-and-Mouth Disease Virus in Wildlife in Eastern Africa and Estimation of Test Parameters of a Nonstructural Protein Enzyme-Linked Immunosorbent Assay for Buffalo

ABSTRACT In this study we estimate the seroprevalence of foot-and-mouth disease virus (FMDV) in wildlife from eastern and central Africa. Sera were sourced from between 1994 and 2002 from a rinderpest surveillance program. Our study compared a nonstructural protein enzyme-linked immunosorbent assay (Cedi test) with a virus neutralization test. The study shows that there is only a low seroprevalence of FMDV in sampled nonbuffalo species. The seroprevalence in the Cape buffalo was high for SAT2, lower for SAT1, and lowest for SAT3. As the SAT2 serotype was most prevalent, the Cedi test largely reflected the occurrence of SAT2-positive animals. The results also suggest that SAT2 became dominant around 1998, with a large increase in seroprevalence. The sensitivity and specificity of the Cedi test were estimated by comparison to the combined virus neutralization test results from all three SAT tests. A Bayesian implementation of the Hui-Walter latent class model was used to estimate the test parameters. The model permits estimation in the absence of a gold standard test. The final model, using noninformative priors and assuming conditional independence of test performance, estimated Cedi test sensitivity at 87.7% and specificity at 87.3%. These estimates are similar to those for domestic bovines; they suggest that the Cedi test is a useful tool for screening buffalo for infection with the various serotypes of FMDV.

Molecular Evolution of Peste des Petits Ruminants Virus

Sequence data will increase understanding of virus evolution, adaptability, and pathogenicity.

Evaluation of cross-protection between O1 Manisa and O1 Campos in cattle vaccinated with foot-and-mouth disease virus vaccine incorporating different payloads of inactivated O1 Manisa antigen.

Serology is used to predict vaccine induced protection against challenge with a heterologous strain of the same serotype of foot-and-mouth disease virus (FMDV). To evaluate the accuracy of such predictions, we compared the protection afforded to cattle vaccinated with the O(1) Manisa strain of FMDV against challenge with either a homologous (O(1) Manisa) or a heterologous strain (O(1) Campos). Serology by virus neutralization test (VNT) using O(1) Manisa antiserum predicted an acceptable protection against such a challenge. Two experiments were carried out to compare the results for consistency. A total of 78 naïve cattle were vaccinated with different antigen payloads (60-0.94 μg) of O(1) Manisa. They were challenged by intradermolingual inoculation with live FMDV, either O(1) Manisa or O(1) Campos. Unvaccinated naïve control cattle (n=20) were also challenged with either the O(1) Manisa or O(1) Campos viruses and all developed generalized FMD. The protection results for the vaccinated cattle revealed that higher payloads of O(1) Manisa vaccine were needed to protect against heterologous challenge compared to that for homologous challenge. The 50% protective dose (PD(50)) values for the vaccine in experiments 1 and 2 were found to be 28.78 and 9.44 for the homologous challenge and 3.98 and 5.01 for heterologous challenge. Furthermore, protection against O(1) Campos required a higher level of vaccine-induced antibody against this virus compared to the level of O(1) Manisa neutralizing antibody associated with protection against homologous challenge. The 50% protective level of in vitro neutralizing antibody was found to be log(10)1.827 for O(1) Campos and log(10)0.954 for O(1) Manisa based on O(1) Manisa based virus neutralization test.