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PubMed2005

Studies of the outbreaks of foot and mouth disease in West Bengal, India, between 1985 and 2002.

Foot and mouth disease (FMD) is the major disease constraint on international trade in livestock and their products. In the state of West Bengal, India, 1,082 FMD outbreaks were reported in the 18 years from 1985 to 2002. Of the prevalent four serotypes, O type FMD virus accounted for the most outbreaks (67%), followed by Asia-1 virus type (15%) and A virus type (14%). Outbreaks of the type C FMD virus were least prevalent (4%), and no cases have been recorded since 1996. The study shows clearly that incidences were highest during the winter months and in the alluvial agro-climatic zones. The distribution and density of the FMD-susceptible population in different districts of the state also played major role in disease incidences. Due to the unrestricted movements of animals among different cattle markets, the disease was transmitted either by direct contact or by aerosols from infected to healthy animals. Cattle suffered most from the disease, accounting for about 95% of the cases. The monitoring of the disease documented in this study provides information about the endemicity of the disease that can help to formulate an effective strategy for an FMD control programme.

Animals↗
PubMed2005

Retrospective genetic analysis of SAT-1 type foot-and-mouth disease outbreaks in southern Africa.

In areas where foot-and-mouth disease (FMD) is endemic in wildlife hosts, such as the Kruger National Park (KNP) in South Africa, control measures are in place that ensure that potentially infected antelope and buffalo do not come into close contact with domestic animals. In South Africa several SAT-1 outbreaks occurred nearly simultaneously in cattle and impala between 1971-1981. Phylogenetic analysis based on partial 1D gene nucleotide sequencing indicated that several of these outbreaks were linked and it is probable that disease spread from the intermediary impala antelope host to cattle in close proximity. Evidence was found for the involvement of viruses from a single KNP genotype in precipitating outbreaks in impala over a 10-year period. In addition, several unrelated outbreaks affecting cattle and impala occurred within a single year. Characterisation of outbreak strains from Botswana similarly revealed that a single genotype affected different species over a 10-year period and that transboundary spread of SAT-1 virus occurred on at least one occasion. This retrospective analysis of outbreak strains has clearly demonstrated that FMD control policies that address the role of antelope as intermediaries in disease transmission are crucial as these wildlife species play an important role in disease dissemination.

Africa, Southern↗
PubMed1989

[Immune response against foot-and-mouth disease virus in cattle: effect of vaccination].

Foot and Mouth Disease Virus (FMDV) is one of the most feared animal virus and vaccination still has to be used in many countries. In previous reports, using a murine model, we studied the cellular basis of immune responses against FMDV and were able to show that they are atypical. In cattle, although complete protection may be attained after only one dose of killed virus vaccine, very little is known about protection against FMDV, except for antibody responses, but practically nothing concerning the cellular basis of their immune response. Moreover, since neutralizing titers do not always correlate with protection, the potency of vaccines in controlled by viral challenge. Our aim is to study cellular immune responses against FMDV, and to search for a correlate to protection. As a first step, 55 virgin cattle from a non endemic area (Patagonia) were divided into three groups: C: non immunized controls; HS: immunized with saponine containing vaccine; and EO: with oil emulsified vaccine. After vaccination, they were carried to an endemic area (Buenos Aires), where they were challenged with live FMDV. Animals were bled immediately before and 7 days after challenge, and their white blood cells and lymphocyte subpopulations were counted. All animals showed a marked neutropenia and eosinophilia, significantly higher in HS than in EO and C groups; both parameters were significantly better in the 2nd assay. Total lymphocyte counts were normal. Lymphocyte subpopulations were assessed by immunofluorescence using monoclonal antibodies: their proportions were normal and did not change during illness in group C. Several factors could have induced the observed eosinophilia and neutropenia: parasites, stress, saponine, others.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

[Recent outbreak of foot and mouth disease in Ivory Coast].

An outbreak of foot and mouth disease (FMD) due to SAT2 occurred among cattle, sheep and pigs in Côte-d'Ivoire. The morbidity and mortality were low so vaccination of only high value livestock in intensive production systems was suggested.

Animals↗
PubMed2004

No foot-and-mouth disease virus transmission between individually housed calves.

The foot-and-mouth disease outbreak in The Netherlands in 2001 most likely started on a mixed veal-calf/dairy-goat farm. The outbreak among the 74 calves on this farm appeared to be limited to four animals, and no clinical signs of FMD were reported. Also on a second veal-calf farm minor clinical signs and limited virus transmission were observed. Since FMD is known to be a very contagious disease, and can cause severe lesions, these observations were disputed. Therefore, we carried out two experiments to determine whether the Dutch FMD virus isolate from 2001 does spread among individually housed calves with limited contacts, either indirect (experiment 1) or direct (experiment 2). In experiment 1, four pairs of calves were housed in an individual box at 1m distance from each other. In experiment 2, two groups of three calves were housed in individual boxes, directly bordering each other. We infected one animal per pair in experiment 1, and the calf in the middle in experiment 2. We recorded clinical signs, virus shedding in saliva and the development of antibodies. In addition, we determined whether the virus was transmitted from the inoculated calves to the neighbour(s). All inoculated calves showed mild signs of FMD--fever, and some vesicles on hooves and/or in the mouth--but only one calf showed signs that were visible without physical examination. All inoculated calves shed virus in the saliva and developed neutralising antibodies. None of the contact animals seroconverted, indicating that virus transmission did not occur. These experiments showed that no virus transmission among individual housed calves can occur. This finding supports the hypothesis of the route of virus introduction to The Netherlands in 2001 and show that the observations on the two veal-calf farms were not impossible.

Animals↗
PubMed2006

Quantification of within- and between-pen transmission of Foot-and-Mouth disease virus in pigs.

Quantified transmission parameters of Foot-and-Mouth Disease Virus (FMDV) are needed for epidemic models used for control and surveillance. In this study, we quantified the within- and between-pen transmission of FMDV in groups of pigs by estimating the daily transmission rate beta, i.e. the number of secondary infections caused by one infectious pig during one day, using an SIR (susceptible-infectious-removed) model. Within-pen transmission was studied in four groups of ten pigs in which 5 infected and 5 susceptible pigs had direct contact; between-pen transmission was studied in one group of ten pigs in which 5 infected and 5 susceptible pigs had indirect contact. Daily results of virus isolation of oropharyngeal fluid were used to quantify the transmission rate beta, using Generalised Linear Modelling (GLM) and a maximum likelihood method. In addition, we estimated the expected time to infection of the first pig within a pen T(w) and in the indirect-contact pen T(b). The between-pen transmission rate beta(b) was estimated to be 0.59 (0.083-4.18) per day, which was significantly lower than the within-pen transmission rate beta(w) of 6.14 (3.75-10.06). T(w) was 1.6 h, and T(b) was 16 h. Our results show that the transmission rate is influenced by contact structure between pigs.

Animal Husbandry↗
PubMed2004

Validation of binary ethyleneimine (BEI) used as an inactivant for foot and mouth disease tissue culture vaccine.

The complete inactivation of Foot and Mouth Disease (FMD) virus is a critical requirement in the production of FMD vaccine to ensure the safety of the product. Binary ethyleneimine (BEI) is an aziridine compound, produced from bromoethylamine hydrobromide (BEA) commonly used for the inactivation of FMD virus during vaccine manufacturing. The validation of BEI, when used as an inactivant, is essential to ensure the quality of the inactivating agent and the validity of the process. In the present study, the inactivation kinetics of Foot and Mouth Disease virus (O, A and Asia-1 serotypes) were determined for different concentrations of BEI (0.4 mM, 0.8 mM, 1.2 mM, 1.6 mM and 2.0 mM). Statistically significant differences in the inactivation kinetics were observed between 0.4 mM and 1.6 mM of BEI. The results indicated that BEI at 1.6 mM was able to inactivate the FMD virus within 8-10 h. Increasing the concentration of BEI beyond 1.6 mM did not appreciably improve the inactivation process. No differences in the inactivation kinetics were found between the various serotypes studied. This study can be used as a guideline for routine procedures for validating the quality of BEA and the inactivation process.

Animals↗
PubMed1995

Overview of foot and mouth disease in southern Africa.

The prevalence of foot and mouth disease (FMD) in the southern African subcontinent between 1931 and 1990 is summarised, together with the major features of the epidemiology and control of the disease. The author emphasises the role of wildlife, especially African buffalo (Syncerus caffer). A proposal is made for a more structured and co-operative approach to investigating the extent and nature of antigenic variation within the Southern African Territories (SAT) types of FMD virus. Quantification of the economic impact of FMD on the agro-economics of the subcontinent is attempted, and the importance of the social values of rural peoples in this respect is explained.

Africa, Southern↗
PubMed2002

Clinical variation in foot and mouth disease: pigs.

In intensively reared pigs, the introduction of foot and mouth disease (FMD) results in severe clinical disease and vesicular lesions in adult and fattening animals, and high mortality in piglets. Vaccination of uninfected herds can assist FMD control and eradication programmes by reducing susceptibility of pigs older than 12 to 14 weeks and providing early protection to piglets through maternal antibody, but once FMD is established on a farm, vaccination alone will not prevent recurrent outbreaks of clinical disease.

Animals↗
PubMedDate not supplied

The carrier state in foot and mouth disease--an immunological review.

The carrier state in foot and mouth disease (FMD) is characterized by the asymptomatic low-level excretion of foot and mouth disease virus (FMDV) from the oropharynx of ruminants for periods that are species and virus strain-dependent. Persistent infection with FMDV readily occurs following the failure of virus elimination at the acute stage of infection, a process thought to be mediated through the phagocytosis of antibody/virus immune complexes. Recent evidence supports the view that carrier cattle are important in the epidemiology of FMD in the field. The absence of histopathological change in persistently infected tissues and the reduced cytopathology of carrier virus isolates in tissue culture suggest that less lytic FMDV variants are generated or selected in the carrier animal. Altered virus replication, due to attenuation or interference, rather than antigenic variation may therefore allow evasion of the exaggerated FMDV-specific systemic and local humoral immune responses that occur in the carrier state. Although cell-mediated immune mechanisms for FMDV clearance have not been described, the eventual elimination of many persistent virus infections involves this arm of the immune system. Thus, further investigation of cellular elements of the immune response, more particularly the local interaction of mononuclear cell infiltrates with persistently infected cells, represents an area of research that has the potential to elucidate the carrier state problem.

Animals↗
PubMed1979

Stability and immunogenicity of empty particles of foot-and-mouth disease virus.

Three strains of foot-and-mouth disease virus were shown to contain significant amounts of naturally occurring 75S, empty particles as well as the infectious, 140S full particles. One of these strains--A Pando (1970)--was studied in detail. The empty particles from this virus strain were shown to have an observed sedimentation coefficient of 67S in 0.04 M phosphate buffer; they were labile in SDS, non-infectious and probably RNA-free and, on heating, they broke down to 12S subunits as did the 140S particles. The empty particles differed from the full particles in their polypeptide composition since they contained VP0, but there was no evidence for a diminished content of VP4. The 75S particles were shown to be present in significant amounts and to be stable to AEI inactivation. At 4 degrees C they were stable for at least two years. In guinea pigs they were as immunogenic as the 140S particles. The antisera raised against the 75S particles had the same serological specificity in neutralization tests as sera prepared against the 140S particle. It was concluded that the 75S particles from the A Pando (1970) strain of FMD virus may provide as important a contribution as 140S particles to the immunogenicity of inactivated vaccines prepared from this virus strain.

Antigens, Viral↗
PubMed1994

Sequence of the S fragment of foot-and-mouth disease virus type A12.

The foot-and-mouth disease virus (FMDV) genome contains a 5' untranslated region (S fragment) capable of forming a stem-loop structure of over 350 bases, which is separated from the remainder of the genome by a homopolymeric cytidylic acid tract (poly(C)) of variable length. The sequence of the S fragment of serotype A12 appears more similar to those of type O1 or type C3 than to subtype A10. The relatively large difference between the S fragment sequences of two type A viruses suggests that the sequences per se of this region of the genome are not critical for the maintenance of function, and suggests the possibility of a relatively recent recombination event within the poly(C) region of the A12 genome.

Amino Acid Sequence↗