Eradication of Swine Vesicular Disease in Italy.

Swine vesicular disease (SVD) is a contagious viral disease of pigs clinically indistinguishable from other vesicular diseases, such as foot and mouth disease, vesicular stomatitis, vesicular exanthema of swine, and idiopathic vesicular disease. In Italy, where SVD was first reported in 1966, an eradication program started in 1995. The program, updated in 2008, was based on regionalization, complete control on pig movements, improvement of pig farms biosecurity, appropriate cleansing and disinfection procedures of vehicles approved for pig transportation, and a testing program using both serological and virological assays. In cases of confirmed SVD virus infection a stamping-out policy was applied. In the period 2009 to 2019, between 300,000 and 400,000 pigs were serologically tested each year. The last SVD outbreak was notified in 2015, and the last seropositive pig was detected in 2017. SVD surveillance is still ongoing and no proof of virus activity has been detected so far. All available data support the complete SVD virus eradication from the Italian pig industry.

The risk of introduction of swine vesicular disease virus into Kenya via natural sausage casings imported from Italy.

Pig production in Kenya is hampered by seasonal markets. As an alternative outlet for the finished pigs, several value-added meat-processing firms have been established. Sausage, which is produced using casings derived from intestines of pigs, is one form of processed meats. Kenya imports several kgs of natural casings every year; and a recent concern is Swine vesicular disease virus (SVDV), which has never been reported in Kenya, might be introduced via natural casings imported from Italy. To determine conditions (with associated probabilities) that could lead to the introduction of SVDV, a quantitative risk assessment model was developed. Using Monte Carlo simulations at 10,000 iterations, the probability of introducing SVDV was estimated to be 1.9x10-8. Based on the suggested volume of import and mitigations used in the analysis, contaminated casings derived from an estimated 0.003 (Range = 8.1x10-8 - 0.08) infected pigs will be included in the consignment each year. The critical pathway analysis revealed that rigorous surveillance programs in Italy have a potential to dramatically reduce the risk of introducing SVDV into Kenya by this route.

Protective immune responses in guinea pigs and swine induced by a suicidal DNA vaccine of the capsid gene of swine vesicular disease virus.

A suicidal DNA vaccine based on a Semliki Forest virus (SFV) replicon was evaluated for the development of a vaccine against swine vesicular disease virus (SVDV). The 1BCD gene of SVDV was cloned and inserted into pSCA1, an SFV DNA-based replicon vector. The resultant plasmid, pSCA/1BCD, was transfected into BHK-21 cells and the antigenicity of the expressed protein was confirmed using an indirect immunofluorescence assay. Immunogenicity was studied in guinea pigs and swine. Animals were injected intramuscularly three times with pSCA/1BCD at regular intervals. Anti-SVDV antibodies were detected by ELISA, the lymphocyte proliferation response was tested by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide method and neutralizing antibodies were measured by microneutralization tests. The data showed that SVDV-specific antibodies, neutralizing antibodies and lymphocyte proliferation were induced in both guinea pigs and swine. Furthermore, after three successive vaccinations with pSCA/1BCD, half of the pigs were protected against challenge with SVDV. These results should encourage further work towards the development of a DNA vaccine against SVDV.

Swine vesicular disease surveillance and eradication activities in Italy.

Swine vesicular disease (SVD) was first observed in Italy in 1966, and was initially diagnosed as foot and mouth disease (FMD). The causative agent of SVD was classified as an Enterovirus within the family Picornaviridae. It was included in the list of diseases notifiable to the World Organisation for Animal Health (OIE) because of the similarity of its lesions to those produced by FMD; however SVD is often mild in nature and may infect pigs subclinically. During the last decade SVD has been persistently reported in Italy, and surveillance and eradication activities are in place. The central and northern parts of Italy have been designated SVD free since 1997, while the southern regions have not achieved disease-free status. However, occasional outbreaks of SVD have occurred in central and northern Italy and have been eradicated using rigorous control measures. Most recent SVD outbreaks in Italy have been subclinical; SVD can rarely be diagnosed now on the basis of clinical signs and it is necessary to use laboratory diagnosis. This paper examines the epidemiology of SVD in Italy, and considers the measures adopted in Europe for SVD control on the basis of current knowledge of the disease.

Quantitative risk assessment case study: smuggled meats as disease vectors.

Outbreaks of foot and mouth disease (FMD), African swine fever (ASF), classical swine fever (CSF) and swine vesicular disease (SVD) can cause significant economic and social costs and severe trade limitations. A number of commodities may be contaminated with these hazards, including meat and meat products derived from infected animals. Great Britain (GB) enforces a number of regulations to prevent the importation of such pathogens. However, the illegal importation of meat provides a route by which controls may be circumvented and pathogens imported. This paper discusses a series of risk assessments examining the disease risk to the GB livestock population of FMD, CSF, ASF and SVD from the illegal importation of any meat product from any region in the world. This paper describes the development of a quantitative risk assessment model designed to identify the major contributors to this risk, and discusses the challenges posed when undertaking such complex risk assessments.

Heparan sulphate mediates swine vesicular disease virus attachment to the host cell.

Heparan sulphate (HS) has been found to serve as receptor for initial cell binding of numerous viruses. Different glycosaminoglycans (GAGs), including heparin and HS, were analysed for their ability to bind swine vesicular disease virus (SVDV), a picornavirus with close homology to human coxsackie B5 virus. Binding of SVDV was established by heparin-affinity chromatography. In addition, infection of IB-RS-2 epithelial porcine cells was inhibited by treating the virus with soluble HS, heparin, and chondroitin sulphate B (CS-B), as well as by enzymic digestion of cell surface GAGs. Analysis of the infection course showed that SVDV uses cellular HS for its binding to the cell surface and that this interaction occurs during attachment of the virus, prior to its internalization into the cell. Sequence analysis of SVDV variants selected for their lack of sensitivity to heparin inhibition in vitro led to the identification of two residues (A2135V and I1266K) potentially involved in heparin/HS interaction. The location of these residues in a three-dimensional model shows that they are clustered in a well-exposed region of the capsid, providing a physical mechanism that could account for the heparin-binding phenotype.

Swine vesicular disease, studies on pathogenesis, diagnosis, and epizootiology: a review.

Swine vesicular disease (SVD) is a contagious viral disease of swine. It causes vesicular lesions indistinguishable from those observed of foot-and-mouth disease. Infection with SVD virus (SVDV) can lead to viraemia within 1 day and can produce clinical signs 2 days after a pig has come into contact with infected pigs or a virus-contaminated environment. Virus can be detected 3.5 hours after infection using immunohistochemistry. In these in vitro studies, this technique was superior to in-situ hybridization. In SVDV-infected tissues, however, more infected cells were positive using in-situ hybridization, and these were already seen 4.5 hours after infection. For serological diagnosis of SVD several new enzyme-linked immunosorbent assays (ELISA's) have been developed. The newest ELISAs, based on monoclonal antibodies, are superior to the previous tests. The new tests produce fewer less false-negative results and enable large-scale serological screening. In screening programmes a small percentage of false positive reactors have been detected. The cause of these false-positive reactions has not been identified, though infections with human Coxsackie B5 virus can be excluded.

Implementation of a system for the regional management of animal health emergencies.

A telematic system to support decisions and operations in case of animal health emergencies has been designed and implemented in the Abruzzo region of Italy. The system aims to improve decision-making by Veterinary Services in the event of an outbreak of exotic disease. The system has been tested, first by a simulated outbreak of foot and mouth disease, and then during an outbreak of swine vesicular disease. Critical problems were detected and corrected in both cases.

Potential animal health hazards of pork and pork products.

The animal health hazards associated with the importation of pork and pork products include four viral agents: foot and mouth disease, classical swine fever (hog cholera), African swine fever, and swine vesicular disease viruses. The safety of importing pork from a zone infected with one or more of these diseases can be adequately determined only through risk assessment. This also applies for the safety of importing pork products which have undergone some form of processing (fully cooked pork products are not counted here). For each disease, the agent (pH and temperature lability), target organs, agent survival in pork and pork products, and agent quantification are discussed. Agent quantification is an input of the risk assessment which measures the viral titres in waste pork and pork products in relation to the oral infective dose estimated for each disease. Two other viral diseases, transmissible gastroenteritis of pigs and porcine reproductive and respiratory syndrome, are presented to illustrate why these two diseases are not hazards when associated with pork and pork products.

[Swine vesicular disease: threat or challenge for Dutch pig farming?]. / Vesiculaire varkensziekte: bedreiging of uitdaging voor de Nederlandse varkenshouderij?

Swine vesicular disease (SVD) caused problems in 1993 when it was detected in Dutch pigs in Italy. As a result, the EC took measures against the export of live pigs. In all cases the animals had been retained at an Italian abattoir or farm for three days or more, which is longer than the minimum incubation time. Extensive clinical inspections and serological testing on the farms from where the pigs originated revealed no evidence of SVD infection. Serological testing for SVD of over 1.5 million blood samples collected from herds within the framework of export- and herd certification, and the testing of slaughter sows and slaughter boars (EC directive), was negative as well. In view of these results it has to be assumed that the Dutch pig population is free from SVD and that the pigs were infected in Italy. However, a complaint from Italy in 1994 led to the detection of two SVD virus-contaminated export collection centres. If the existing regulations on the cleansing and disinfection of the transport chains are stringently enforced and implementation of the rules is continuously supervised, then it may be expected that the problems have been overcome.

Swine vesicular disease in Great Britain.

The State Veterinary Service in Great Britain has encountered considerable difficulty in eradicating SVD. For the last four years confirmed outbreaks have been mainly confined to one region, linked directly to outbreaks in that region, or have occurred as isolated cases related to the feeding of swill. The surveillance effort to locate subclinical disease has far surpassed that of any other country. There is no doubt that the introduction of SVD into any country which adopts a stamping-out policy for FMD and does not vaccinate, could present similar problems to those experienced by Great Britain.

[Possible methods of control of virus disease in swine today and in the future. II. Specific applications (author's transl)]. / Bestrijdingsmogelijkheden van virale ziekten bij het varken nu en in de toekomst. II. Specificke toepassingen.

The four alternatives discussed in the previous paper (5), are applied to a number of virus infections which are common in pigs. The enzootic state of SMEDI enteroviruses, vomiting and wasting virus and parvovirus should be promoted by bringing the young gilts into close contact with the older sow population at a sufficiently early stage. There should preferably not be a change of herd for primiparous sows during pregnancy. In parvovirus infection, maternal immunity may be so prolonged that gilts will only be infected after the time of breeding. Therefore, mating should preferably be postponed until they are nine months of age, unless previous serological tests have shown that they are in a state of active immunity. Considering the present disease situation of swine fever in several continental West European countries and consequently they high number of existing virus sources, compulsory vaccination of sows and fattening piglets is recommended against this virus on an international scale for at least three years. This vaccination can be omitted only after the number of outbreaks has been reduced to a very low level. Vaccination is the only possible alternative left in the combat against Aujezky's disease. Caution is undoubtedly indicated in using live vaccines in these cases. So far, methods have not become available for the effective control of transmissible gastroenteritis and prospects are not encouraging. The possibility of eradication of transmissible gastroenteritis is discussed.

[Swine Vesicular Disease. A Review (author's transl)]. / Vesiculaire varkensziekte, een overzicht

The article gives a comprehensive review on swine vesicular disease (SVD). The properties of the virus, symptoms, diagnosis, epizoötiology and control of the disease are described. The clinical appearance is illustrated by photographs from experimental infections. The differences in the epizoötiology of SVD and foot-and-mouth disease are discussed.