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.

Vaccination in the control strategy of bluetongue in Italy.

The incursion of bluetongue (BT) in Italy, in August 2000, caused heavy economic losses, partly due to the direct effect of the disease on the animals, but mostly due to indirect losses due to ruminant movement restrictions conducive to heavy losses to the cattle and sheep industry. To limit losses due to both disease and virus circulation, which was the cause of movement restrictions, the Italian Ministry of Health in May 2001 ordered the vaccination of animals of all domestic ruminant species in infected and "at risk" areas. The vaccination strategy derived from a risk assessment that suggested that the vaccination of all domestic ruminants could reduce both direct losses and virus circulation significantly. The different levels of vaccination coverage, achieved in the various regions of Italy, had clear consequences on the spread of both disease and infection. In regions where more than 80% of the target populations were vaccinated properly, the disease disappeared almost completely and virus circulation was significantly reduced, as documented by the serological surveillance system, after a single vaccination cycle. This led to a significant decrease in the areas subject to movement restrictions. Data generated by both field and controlled experiments contributed to modify the EU approach to BT and to some of the conclusions of the Third OIE International Symposium on Bluetongue that will probably lead to a modification of the Office International des Epizooties (OIE) standard.

Field experiences in the control of avian influenza outbreaks in densely populated poultry areas.

From 1997 to 2003, Italy has been affected by two epidemics of highly pathogenic avian influenza (HPAI) and by several outbreaks of low pathogenic avian influenza (LPAI). In 1999-2000 a severe HPAI epidemic affected the country, causing 413 outbreaks: a total of about 16 million birds died or were stamped out. From August 2000 to March 2001, a H7N1 LPAI strain infected 78 poultry farms. The last affected flock was stamped out on the 26th of March 2001. In October 2002, another LPAI virus of the H7N3 subtype emerged and infected a total of 388 poultry holdings. Eradication measures were based on stamping out or controlled marketing of slaughtered birds on infected farms and on the prohibition of restocking. Restriction measures on the movement of live poultry, vehicles and staff were also imposed. To supplement these disease control measures, two emergency vaccination programmes, based on the "DIVA" (Differentiating Infected from Vaccinated Animals) strategy were implemented. The two vaccination campaigns (2000-2002 and 2002-2003) both resulted in the eradication of infection. However, the first campaign appeared to be more successful that the second and possible explanations are discussed.

Bluetongue virus surveillance in a newly infected area.

The occurrence of bluetongue virus (BTV) in areas in which intensive animal production is practised and where there is extensive movement of animals may have a substantial impact on both animal trade and husbandry. This situation occurred in Italy after the detection of bluetongue (BT) in August 2000. In such situations, surveillance can be used to delineate with precision those areas in which the virus is circulating and, consequently, to enforce the appropriate animal movement restrictions. Furthermore, surveillance can provide the data required to assess the risk associated with animal movement and trade. A structured surveillance system for the detection of BTV has been in place in Italy since August 2001. The system is based on the periodical testing of unvaccinated sentinel cattle that are uniformly scattered throughout Italy in a grid of 400 km(2) cells. The initial number of sentinel sites and sentinel animals, together with the width of the restricted area generated by the finding of a single seroconversion in a sentinel animal, were based on conservative criteria. Animal movement was restricted in a 20 km radius buffer zone around any positive serological result. This buffer area extends about 1,257 km(2), equivalent to the area of three grid cells. After the commencement of the BT vaccination campaign in Italy, the sentinel surveillance system was the only way in which the effectiveness of vaccination and the incidence of infection in the non-immunised strata of ruminant animals could be estimated. Data collected over two years was used to assess the risks posed by the adoption of less conservative criteria for the delineation of infected areas and by the progressive relaxation of movement restrictions of vaccinated animals. In regard to the delineation of restricted areas, a new approach was tested and validated in the field, based on a Bayesian analysis of the positive and negative results obtained by the testing of sentinel animals from defined regions. For the risks related to animal movement, the surveillance data was used in risk assessment analyses to address the movement of slaughter and breeding animals from vaccinated/infected and surrounding areas to free areas. These risk assessments led to an amendment of the relevant European Union legislation. Finally, a Montecarlo simulation model was developed to simulate different sentinel system scenarios and to decrease the total number of sentinel animals and sites required by the surveillance system. The sentinel surveillance system was complemented by an entomological surveillance system based on the use of a number of permanent blacklight traps run weekly year-round and a number of mobile blacklight traps moved through the grid cells during the summer and autumn of each year. The aim of entomological surveillance was to define the maximum distribution of vectors and their seasonal population dynamics. Furthermore, the permanent trap system provides an early warning of the start of new epidemics. The data from the entomological surveillance system were also analysed to generate probability maps of the presence of the principal BTV vector (Culicoides imicola) and to define the geographical risk of BT on a nationwide basis, and to predict the geographical distribution and the short-term spread of C. imicola in Sardinia, using spatio-temporal data. The detection, since 2001, of BT outbreaks in the absence of C. imicola and the recent identification of BTV in midges of the Obsoletus Complex also stimulated investigations on other vector Culicoides, including C. obsoletus and C. pulicaris.

Bluetongue in Italy: Part I.

The eastern focus of the current outbreak of bluetongue (BT) in the Mediterranean Basin commenced in late 1998, infecting Turkey and some of the eastern islands of Greece. In the summer of 1999 it moved to continental Greece and for the first time to Bulgaria. By the late summer of 2000, BT spread progressively through Greece and to the Balkan states. The BT virus (BTV) serotypes involved were BTV-4, BTV-9 and BTV-16. The west-central focus of the outbreak, involving BTV-2, appeared in Tunisia in December 1999 and the following summer also in Algeria. In August 2000, BTV-2 was reported for the first time in Italy (in Sardinia) and soon thereafter in France (Corsica) and in Spain (the Balearic Isles). In the autumn of 2000, a second serotype (BTV-9) emerged in southern peninsular Italy. Eventually this incursion of virus into the central Mediterranean region resulted in the largest epidemic of BT ever to affect Europe. Some features of this epidemic differ significantly from those observed previously, namely: a) its deep penetration northwards (reaching 44 degrees N both in Italy and in the Balkans) b) its persistence across four seasons in various zones of Italy and the Balkans, implying that BT could become endemic over a wide geographic area c) its successful invasion of areas separated from previously infected ones by fairly large distances (Sardinia, Sicily, Calabria, and the Balearic islands). The pattern of the spread of BT across Italy, before the introduction of vaccination, is described. The possible role of climate, soil and insect vectors on the incidence of the disease, and the overwintering of the virus, are discussed. Some hypotheses on the possible origins and modes of introduction of BTV into Italy are postulated.

Bluetongue in Italy: Part II.

In summer 2000, bluetongue (BT) infection was reported in Italy and caused a widespread epidemic involving a total of ten southern and central regions and is still in progress after three years. From the date of the first case (18 August 2000) to 14 May 2001, when the lowpoint in the first epidemic curve was reached, a total of 310,234 animals in 6,869 flocks of three regions had been involved. From 15 May 2001 to 14 April 2002, when a second epidemic wave swept through central and southern Italy, a total of 323,635 animals in 6,807 flocks in seven regions were involved. During 2000 and 2001 virtually no susceptible ruminants were vaccinated. On 11 May 2001, the Italian Ministry of Health ordered the vaccination of all susceptible domestic ruminant species (i.e. sheep, goats, cattle and water buffalo) in the infected and surrounding areas. The vaccination strategy stemmed from a risk assessment that demonstrated the possibility of such a strategy preventing most of the direct economic losses and decreasing the level of virus circulation. Vaccination of the target populations commenced in January 2002. In July 2002, when the new epidemic peak was reached, the percentage of vaccinated populations varied between the regions with direct consequences on the spread of BT. The relationship between vaccination coverage of the target populations and animal losses due to disease and virus circulation, and as detected by the sentinel surveillance system, was analysed. The effectiveness of the vaccination campaign in limiting virus circulation and consequently indirect losses due to animal movement restrictions was analysed and evaluated. At the end of 2002, a second risk assessment led to the authorization of the movement of vaccinated animals from infected areas (where at least 80% of the susceptible population was vaccinated) directly to slaughter in unvaccinated areas free from infection. This risk assessment also generated new criteria to define zones where animal movement restrictions should be applied. Following the second vaccination campaign (January to May 2003), a third risk assessment was performed and the results from vaccination trials performed in controlled and in field conditions studied. These studies indicated that procedures to move vaccinated breeding animals from zones where infection exists to unvaccinated infection free zones could be contemplated.

Surveillance system of bluetongue in Italy.

The authors provide details of the bluetongue surveillance and the Internet-based information systems that were implemented in Italy. The systems were structured with the aim of gathering and spreading information and data to support decision-making, management of control activities and provide an early warning system. Information and data generated by the surveillance system enabled the detailed analysis of bluetongue epidemiology, vector distribution and vector population dynamics. This information and data also allowed the analysis of risk factors associated with vector spread and animal movements, which resulted in and increased the flexibility and the efficiency of the enforcement of control measures.

Bluetongue vaccination in Europe: the Italian experience.

The incursion of bluetongue (BT) into Italy in August 2000 caused heavy economic losses, partly due to the disease itself, but mostly because of disruption caused to the national animal trade structure. To limit direct losses and the circulation of BT virus (BTV), the Italian Ministry of Health ordered, on 11 May 2001, the vaccination of all susceptible domestic ruminant species (i.e. sheep, goats, cattle and water buffalo) in both infected and surrounding areas. The vaccination strategy was based on a risk assessment that suggested it would prevent direct economic losses and significantly reduce virus circulation. Vaccination of the target animal populations commenced in January 2002, prior to the epidemic peak of BT that began in July 2002. The proportion of vaccinated animals differed between the various regions and the varying levels of vaccination of these populations had clear consequences on the occurrence of clinical disease and the spread of BTV infection. In those regions where more than 80% of the target population were properly vaccinated, the disease disappeared almost completely and virus circulation was reduced significantly. The importance of this reduced circulation of BTV (i.e. infection did not spread from affected areas) was immediately obvious in areas affected by the less virulent BTV serotype 9 where, despite the virtual absence of clinical disease, trade of animals to other areas was prohibited. The areas affected by the highly virulent BTV-2 also benefited from vaccination because it eliminated clinical disease while animal movements were prohibited. The main consequence of the reduction of virus circulation after vaccination, as documented by serological surveillance, was a significantly reduced expansion of the areas that were subjected to animal movement restrictions. Subsequently, analysis of surveillance data, coupled with specific risk assessments, led to a progressive relaxation of movement restrictions even in areas where the infection was still present but where most of the population had been adequately vaccinated. The effectiveness of the strategy used in Italy (i.e. vaccination of all domestic ruminants) was reinforced by extensive experimental and field studies. The aim of these studies was to: a) evaluate levels of individual and herd immunity and resistance to challenge conferred by vaccination, and b) quantify the frequency and severity of the adverse effects of vaccination on domestic ruminants. Ongoing research has focused on the ability of vaccination to suppress or reduce viraemia in ruminants following natural challenge by a virulent BTV strain. These studies address the issue of safety of the trade and movement of vaccinated animals that originate from areas in which BTV continues to circulate and could justify the reversal in current policy that restricts the international trade of animals vaccinated against BT.

Implementation of a new contingency plan for bluetongue disease in Italy.

Since the first appearance of bluetongue (BT) in Italy in late August 2000, the ecology of vectors and the environmental conditions affecting their distribution and survival proved to be the most difficult factors to monitor, and represented a serious challenge to the effectiveness of the National Contingency Plan promulgated in 1991. Moreover, the Italian Ministry of Health considered the national management plan of BT inadequate to prevent further spread of the disease. The authors describe the implementation of a new BT contingency plan, integrating an operations manual and an ad hoc information system, which operated also as a decision-support system both at local and central levels. The plan describes the national capacity for dealing with BT outbreaks, the composition and duties of the National Disease Control Centre and Local Disease Control Centres, the chain of command and the strategies adopted.

Health management of large transhumant animal populations and risk of bluetongue spread to disease-free areas.

Transhumance, or seasonal grazing, in central Italy is a husbandry practice that is over two thousand years old. It involves the seasonal movement of sheep, goats and cattle from the southern lowlands of mainly the Puglia and Lazio regions, to summer pastures in the mountains of Abruzzo and Molise. Bluetongue (BT) made its appearance in Italy in 2000. In the early summer of 2001, disease was present in three regions: Sardinia, Sicily and Calabria. Neither an effective surveillance system nor a vaccination campaign had been implemented. Movement of ruminants to the disease-free regions of Abruzzo and Molise was therefore banned. The Italian Veterinary Services had to meet the challenge of the movement of ruminants from surveillance to disease-free zones, given the impossibility of stopping transhumance. The General Directorate of Veterinary Public Health, Food and Nutrition of the Ministry of Health developed a plan for both the Puglia and Abruzzo regions based on serological, virological and entomological surveillance. The plan was implemented between May and June 2001 when 7,000 animals moved from the Puglia surveillance zone to the infection-free summer pastures. In the early summer of 2002, eight regions were infected (Sardinia, Sicily, Calabria, Basilicata, Puglia, Campania, Lazio and Tuscany). Simultaneously, a nationwide surveillance system and a vaccination campaign, were implemented in infected regions. In the provinces where vaccination was compulsory, deviation from the animal movement ban was allowed if at least 80% of susceptible stock had been vaccinated. However, this objective was not achieved in the provinces of Rome and Viterbo (Lazio) where a large transhumant population was present and where sporadic virus circulation had been detected. A specific control plan to allow transhumance from Lazio to Abruzzo, Marche and Umbria was designed and implemented to increase the number of animals that could be moved. Between May and June 2002, authorisation was granted to move 28,000 head, whereas prohibition of movement was ordered for 12,000 sheep (belonging to 21 flocks). Regional authorities financed feeding, watering and housing for these animals. Transhumance did not spread infection to disease-free areas either in 2001 or in 2002.