BLUETONGUE IN ITALY: RISK ANALYSIS ON THE INTRODUCTION INTO FREE TERRITORIES OF VAC- CINATED ANIMALS FROM RE- STRICTED ZONES.

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2 BLUETONGUE IN ITALY: RISK ANALYSIS ON THE INTRODUCTION INTO FREE TERRITORIES OF VAC- CINATED ANIMALS FROM RE- STRICTED ZONES. Bruxelles, 3 Dicembre 2002

3 INTRODUCTION...1 Italian strategy against bluetongue... 1 Results of the first vaccination campaign... 3 Reasons for a risk analysis... 4 HYPOTHESIS OF A NEW METHOD TO DEFINE BT-INFECTED AREAS WHERE AT LEAST 80% OF THE SUSCEPTIBLE REGIONAL POPULATION IS VACCINATED: THE CASE OF SARDINIA...4 The regulation in force The consequences of the regulation in force... 4 A proposal for a new criterion to define infected areas when at least80% of the ruminant population is vaccinated... 5 Conclusions... 6 RISK ASSESSMENT ON THE INTRODUCTION INTO FREE TERRITORIES OF VACCINATED ANIMALS ORIGINATING FROM RESTRICTED ZONES...7 Facts about vaccinated animals... 7 Assumptions and variable used... 7 Validation of the model... 9 Results... 9 Conclusions...10 REFERENCES...11 December 2002 I

4 INTRODUCTION During years from 2000 and 2002, Italy experienced the largest bluetongue (BT) epidemics in Europe. During BT epidemic (from August 2000 to May 14 th 2001) the disease involved 3 Italian Regions: Sardinia, Sicily and Calabria and has been diagnosed in 6,869 flocks. The final morbidity rate in infected flocks was 18.2% and the mortality rate was 3.3%. A total number of about 275,000 sheep and goats has been lost due to both BT mortality and slaughter of sick animals (Table 1). During BT epidemic (from May 15 th to April 14 th 2002) the disease involved 8 Italian Regions (Sardinia, Sicily, Calabria, Basilicata, Campania, Apulia, Latium and Tuscany), with 6,807 diseased flocks. The final morbidity rate was 17.8% and the mortality rate was 5.2%. A total number of about 250,000 sheep and goats has been lost due to both BT mortality and slaughter of sick animals (Table 1). At present ( BT epidemic; from April 15 th 2002), the disease has been diagnosed in 8 Regions (Basilicata, Calabria, Campania, Latium, Molise, Apulia, Sardinia and Sicily), with 402 diseased flocks. Provisory data show a 8.2% and a 6.0% morbidity and mortality rate, respectively. A total number of 2,759 sheep and goats has been lost due to both BT mortality and slaughter of sick animals (Table 1). Italian strategy against bluetongue Since BT first appeared in Sardinia in August 2000, it was clear that the infection would remain in the Italian territory for many years in the future. The first dilemma for the veterinary authority was whether to vaccinate in an attempt to reduce both mortality in sheep and virus circulation that impairs animal movements severely. A risk analysis was performed in order to provide ancillary information to veterinary authority for them to decide upon the available tools and the possible means to control the disease and to reduce virus circulation. In the meantime an harsh debate on whether to use vaccination as a control tool involved both the scientific and the animal productions world and eventually also the political one in Italy. The debate concerned the safety, transmissibility and the possible reversion to virulence of Ondersterpoort s live virus vaccine and the likelihood of reducing direct and indirect consequences of the infection without vaccination. The National Reference Centers for Veterinary Epidemiology and for Exotic Diseases, therefore, carried out a quantitative risk analysis in April 2001 (available in Italian language on the web site: focused on the possible consequences, in terms of animal losses and spread of the disease, with and without the application of a vaccination policy. In particular, risk analysis indicated that the vaccination of all ruminants in the protection zones would likely hesitate in a significant decrease in virus transmission or in the cessation of the disease after 3-5 years. The risk analysis, however, could consider only data available at the time and warned about the uncertainty arising from the incompleteness of data on vector distribution and capacity, weather and pedology, vaccine ability to prevent viraemia in cattle and vaccine safety for ruminants other than sheep. Despite the worldwide lack of experience in reducing BTvirus (BTV) circulation and the gaps in the knowledge of some Italian geographical features relevant for BTV ecology, the Italian December

5 Ministry of Health decided on May 2001 to vaccinate all domestic susceptible populations in infected and neighboring regions, taking into account also two European Decisions, on February and May 2001, that approved sheep vaccination in some Italian provinces. In fact, the high economic losses due to movement restrictions in infected areas and, consequently, the need to reduce virus circulation as much as possible, persuaded the Ministry of Health to approve the use of vaccine, not only in sheep, but also in goats and cattle in an attempt to create a resistant population able to either reduce or interrupt - in zones with low levels of virus and vector pressure - BTV circulation. The possibility of using the Ondersterpoort s live virus vaccine in cattle was supported by safety, potency and reversion to virulence studies on bovine animals carried out by the National Reference Centers. Despite the vaccination Order issued by the Ministry of Health on May 11 th 2001, not a single dose of vaccine was employed during late spring and early summer This violation was allegedly due to:! the beginning of the reproduction season for most of the ewes, reducing the population of animals eligible for vaccination to a level which made mass vaccination virtually useless;! the evidence of the beginning of the vector population increase that advised against vaccinating animals for the risk of vaccine virus transmission by vectors considered to increase the risk of virus genome recombination and the possible appearance of new and unknown serotypes. The vaccination campaign, therefore, started in Sicilia in October 2001, in Sardegna and in Calabria in January 2002, and in Lazio and Toscana in March At present the vaccination of all domestic ruminant populations is compulsory in the restricted zones (as defined by the Commission Decision 2001/783/EC) and in some others territories defined at high risk of infection (Figure 1). The choice of reducing, as much as possible, areas of viral activity, by regular vaccination campaigns, is a preventive measure that Italy implemented in order to preserve Italian and other European areas, that are at present free but at risk of being infected, by BTV. The vaccination policy has been implemented jointly with a strict animal movement control in order to achieve the objective of reducing infection spread. Italian Authorities, therefore, implemented an epidemiological surveillance system and issued instructions relating to animal movements. Epidemiological surveillance is based on regular serology and entomology monitoring (Tables 2, 3, 4) aiming at: a) early detecting of wild virus circulation in protection and surveillance zones and in the rest of Italy by regular testing of more than 20,000 sentinel animals distributed in such a way as to cover the whole of Italy; b) monitoring of the BTV serotypes circulating; c) checking population immunity by random testing of more than 15,000 vaccinated animals; d) determining the dynamics of C. imicola populations in order to establish an early warning system of significant vector population growth in relevant areas (Figure 2); e) defining risk maps with simulation models able to predict BTV circulation on the basis of data on vectors density, susceptible animals population, weather and soil conditions; December

6 f) studying the possible epidemiological role of other Culicoides spp. Serology and entomology are supported by several other activities to be implemented in case of suspect or positive results and by regular clinical surveillance of all sheep and goats flocks. The basic instructions issued by the Italian Authorities for the control of animal movements are: a) definition of infected holding (IH) as holding (sheep and goat flock or bovine herd) where BTV circulation has been proven in the last 100 days by either clinical examination, serology, virology on ruminants and captured midges; b) definition of infected area (IA) as the territory of all municipalities within a 20 km radius from an IH. No susceptible animals can leave the IA, in compliance with Council Directive 2000/75/EC and Commission Decision 2001/783/EC; c) definition of restricted zone (RZ) as the territory of a Province where BTV circulation has either been proven or is highly suspected. The list of Provinces declared as RZs is constantly notified to European Commission in order to update Annex I of the Commission Decision 2001/783/EC. RZs include Protection and Surveillance Zones. Animals, vaccinated at least 30 days before shipment, may leave RZ (excluding IAs) towards free areas only if from Provinces where more than 80% of the domestic ruminant populations has been vaccinated. Data from epidemiological surveillance, compiled with meteorological data and ad hoc surveys feed a BT management information system available on the Internet ( which provides:! a weekly update of free, infected and restricted zones;! the list of activities carried out, in order to implement corrective measures when needed;! inquiries of the epidemiological surveillance database in order to acquire laboratory tests results. The existence of a BT information system available on the Internet provides the Veterinary Services with the information needed to implement properly all the measures foreseen for animal movement control. In synthesis, the ongoing attempt to reduce BTV circulation in Italy is based on the systematic vaccination of all domestic susceptible animals and the restriction of animal movements from infected areas. Regular, intensive epidemiological surveillance is used to both delimiting, as precisely as possible, the territories with virus circulation and, consequently, to manage all control activities, including animal movements. Results of the first vaccination campaign In 2002, the vaccination campaign reached the goal of vaccinating more than 80% of susceptible domestic ruminant populations only in Abruzzi, Sardinia and Tuscany Regions (Figure 3 and Table 5). Proper implementation of the vaccination campaign was conducive to reduction of the clinical disease (i.e. Sardinia and Tuscany). In Sardinia the number of clinical outbreaks dropped from 6,090 in epidemic to 10 in , and in Tuscany after the 158 outbreaks in epidemic, the clinical disease disappeared (Table 1). The effects of the vaccination campaign appear to be less evident as far as virus circulation is concerned, if one limits himself to consider only the extension of the IAs in Sardinia and Tus- December

7 cany (Figure 4). IHs, in fact, are scattered all over the territories but consistent clusters of infection are absent (Figure 5). Considering the incidence of seroconversion in sentinel animals, furthermore, makes the reduction of BTV circulation induced by vaccination in Sardinia and Tuscany quite evident. Comparison with Regions where the vaccination campaign did not reach the proposed objectives makes the positive effect of vaccination clearer (Figure 6). Reasons for a risk analysis Before the occurrence of BT, cattle left Sardinia, Sicily and the southern regions to be fattened and slaughtered in Northern Italy - during the tracing of animals that had left infected areas, in 2000, it was shown that only for Sardinia 10,957 bovine animals had left the Island from June to August 2000 and were scattered throughout continental Italy. Since August 2000, animal trade between infected and free areas has come to a complete standstill. Sardinia, in particular, due to the its climatic and epidemiological conditions vectors survive for almost the whole year - has not been able to export any ruminant toward the mainland. Long term standstill, therefore, not only leads to great economical losses and social consequences, but without compensation, is also almost impossible to enforce indefinitely. The National Reference Centers for Veterinary Epidemiology and for Exotic Diseases have assessed the vaccination campaign effects on BTV circulation and: 1. performed a risk analysis in order to assess the risk associated with animal movement from restricted areas, according to the level of immunity of susceptible animal populations induced by vaccination in the same areas; 2. proposed a new method to define BT infected areas when at least 80% of the domestic ruminant population present in the area is vaccinated. HYPOTHESIS OF A NEW METHOD TO DEFINE BT-INFECTED AREAS WHERE AT LEAST 80% OF THE SUS- CEPTIBLE REGIONAL POPULATION IS VACCINATED: THE CASE OF SARDINIA. The regulation in force. Article 6 of 20 November 2000 Council Directive 2000/75/EC laying down specific provisions for the control and eradication of bluetongue, foresees that the official authority shall extend movement restriction measures to holdings located within a radius of 20 kilometres around the infected holding or holdings and gives, thus, the basic definition to delimit the IAs. The restrictions in the «infected area» are enforced for as long as the surveillance proves the existence of viral activity and for 100 days after the last evidence of virus circulation. Virus circulation can be shown by clinical, serological, virological or entomological surveillance activities. The same Directive, however, considers that «the 20 km zone» may be either extended or reduced on the basis of epidemiological, geographical, ecological or meteorological circumstances. The consequences of the regulation in force. «Infected zones» in the current epidemic season cover most of the Sardinian territory and are virtually as extended as those of the epidemic (Figure 4). December

8 In Sardinia no ruminant was vaccinated before the epidemic when a total of 6,090 outbreaks were recorded. Since the beginning of the epidemic season the total number of outbreaks reported has been 10-5 of which in the last 100 days (August 20 - November 28). A total of 28 positive (0.65%) of 4,281 sentinel animals in 23 (5.51%) of 417 holdings were detected, in the last 100 days (Figure 7). Vaccination of whole domestic susceptible animal population is a variable able to modify the epidemiology of the infection considerably, as shown in Results of the first vaccination campaign above. BTV circulation, in fact, appears to be quite rare and scattered, in the territories where at least the 80% of the susceptible domestic animals have been vaccinated. This seems to indicate that BTV transmission, in these zones, is limited to rather confined local microhabitats. In this context, the definition of the infected zone, as a buffer of 20 Km of radius around proven infection, does not appear to be fully justifiable, if one considers the real extension of the area in which virus transmission is actually taking place. When sensitive sentinel and entomological surveillance systems are implemented, the area where virus circulates can be defined on a scientific basis by statistical analysis of observational surveillance data. This appears more reasonable than defining the infected area by an a priori system based upon the possible occurrence of an hypothetical event (i.e.: new animals/vectors being infected from the source observed). It is likely that the extension of «protection zones» can be reduced considerably compared to the present 20 km radius, in case of territories where the whole susceptible animal population is vaccinated. In fact, serological surveillance results show (Figure 8) that the areas reported as infected in Figure 4 are far wider than the areas where virus circulation actually takes place. Viral circulation appears, at present, to be limited to residual pockets of infection randomly scattered amongst uninfected areas (Figure 8). The definition of «infected area» according to Council Directive 2000/75/EC takes into account only positive results and the informative value of negative results in sentinel animals is neglected. This conservative approach can be justified when the infection is actively spreading in a ruminant populations completely susceptible. However, in case of a population largely resistant to the infection (because of the vaccination campaign), a more refined and detailed definition of «infected area» taking into account negative results appears necessary. In fact, when infection is observed in a susceptible population spread of the agent is the most likely phenomenon and the definition of large «protection and surveillance zones» appears necessary. The presence of negative animals appears to be «irrelevant» given the high probability of them becoming positive. When, on the contrary, infection occurs in a largely resistant population the spread of the agent is likely to be quite limited and does not warrant large scale restrictive measures. Negative animals become «quite relevant» given that they are the proof of the infection spread being stifled by the resistant animals in the population. A proposal for a new criterion to define infected areas when at least80% of the ruminant population is vaccinated. Scientific basis For the purpose of BT serological surveillance Italy has been divided into a grid of 400 km 2 cells. A sample of 58 sentinel animals is selected In each cell, and serologically tested, every second week. This sampling procedure is designed to give a 95% probability of at least one December

9 positive animal being detected, when the incidence of infection is at least 5% or more, according to the binomial distribution. Given these assumptions, an epidemiologically homogeneous neighborhood can be defined, for each point on a map, and, based on the results obtained in the sentinel animals living in this neighborhood, the probability of an incidence of infection 5% can be calculated (Figure 9). Then, given the criterion originally chosen to define the sample size for the sentinel network, areas where the probability of infection 1 is greater or lower than 5%, can be defined. Example Step 1: definition of homogeneous neighborhoods. The distance d between each negative herd and the nearest positive one is calculated for each negative sentinel herd. A circle with radius equal to d, drawn around the negative sentinel herd, will enclose only other negative herds, i.e. defines an area where viral circulation is unlikely. This area is defined as the " homogeneous neighborhood" of that specific herd. To define the " homogeneous neighborhood" where viral circulation is likely, the same procedure can be used centering around positive herds (Figure 10). Step 2: definition of the probability of the presence of infection at each point on the map where a sentinel herd is present. The total number of both tested and positive sentinels (if any) present in the sentinel herds within the homogenous neighborhood is calculated and used to estimate the probability that infection incidence is at least 5% within the sentinel herd which is located in the very center of that specific neighborhood, according to the binomial distribution (Figure 9). Specific neighborhoods are calculated for all sentinel herds. Step 3: the interpolation. To define the probability of infection for each single point on the map (i.e: any georeferenced herd within the map), is necessary to interpolate all neighborhood probabilities calculated by the regular Krieging method. In Figure 11, the results of this interpolation are compared with the distribution of positive and negative sentinel herds in Sardinia. Step 4: the definition of the infected zone around clinical outbreaks. Clinical outbreaks can not be included in the proposed criterion, at present and, therefore, the criterion used at present to define infected areas around the outbreak has to be maintained. Conclusions A new criterion for the demarcation of infected areas in regions where at least 80% of the susceptible population is vaccinated is proposed: - an epidemiologically homogeneous neighborhood is defined around each sentinel herd; - the total number of sentinel animals and the total number of positive sentinel animals within this neighborhood are used to calculate the probability of infection in the center of this neighborhood; - data calculated for the center of each neighborhood are interpolated using the regular Krieging technique; - areas where the probability of infection is at least 5% or more are considered infected; 1 where "infection" = incidence 5% December

10 - around each clinical outbreak of BT, the territory of all municipalities falling within a 20 km radius from the IH is considered the IA. RISK ASSESSMENT ON THE INTRODUCTION INTO FREE TERRITORIES OF VACCINATED ANIMALS ORIGI- NATING FROM RESTRICTED ZONES The risk of introducing BTV in infection free zone by animal movement from zones under restriction has been assessed considering different scenarios, according to percentage of animal vaccinated in the population of the zone of origin. Facts about vaccinated animals Current knowledge on the possible epidemiological role played in BTV transmission by vaccinated animals is quite limited. Some relevant information regarding immunity levels in vaccinated animals, however, exists. In particular,:! according to published data (Hunter P. and Modumo J., 2001), sheep subjected to vaccination and subsequently challenged with homologous wild virus, do not manifest a detectable viraemia. These results are confirmed also in cattle by an experiment carried out in Italy by the National Reference Centres for Veterinary Epidemiology and Exotic Diseases (unpublished data), where 4 cows, vaccinated for BTV serotype 2 in May 2001, have been challenged in July 2002 with the homologous wild BTV. All cows have been examined until October 2002 and virus isolation has been attempted repeatedly - every 3 days for the first 7 weeks, and then weekly - with negative results;! field data collected by the National Reference Centers for Veterinary Epidemiology and Exotic Diseases suggest that more than 80% of vaccinated animals have antibody detectable by sero-neutralization for, at least, days after vaccination. The same data indicate also that a solid immunity is reached after days after vaccination (Figure 12);! detectable viraemia due to the vaccine is rare, does not last more that 6-8 days and titers observed are always below 10 3 /ml that is considered the threshold for vector infection (IZSAM, 2001). Various other aspects of immunity against BTV are not known clearly yet. This uncertainty must be taken into account when assessing risk linked to the movement of vaccinated animals. In particular, the main aspects that are at present unclear are:! for how long vaccinated animals will be resistant to infection;! the existence of a minimum circulating antibody titer indicative of the animal resistance to infection in field condition;! the existence of vaccinated animal resistant to infection in field condition in the absence of circulating antibody titer. Assumptions and variable used The following assumption and variables has been, therefore, considered in the risk assessment: 1. Assumptions December

11 a) besides vaccination, no other epidemiologically relevant factor (e.g. abundance of vectors, vector activity, climatic variables, etc.) differed significantly compared to previous years; b) incidence of infection has been estimated assuming a decrease in a vaccinated population compared to a non-vaccinated population proportional to the product of infected by susceptible animals; c) in the lack of a minimal protective antibody titers, the expected number of positive sentinel animals has been simulated considering 2 scenarios: i. all vaccinated animals are protected against the infection, irrespective of circulating antibody titer; ii. only animals with serum-neutralizing antibody titer of at least 1:10 are protected against the infection; Results of the scenarios have been compared with actual surveillance data and the first scenario has been chosen for the subsequent simulations in other words all vaccinated animals have been considered to be resistant irrespective of their circulating antibody titer following vaccination; d) viremia duration of 60 days (conservative assumption); e) random selection of animals to be moved to uninfected area. 2. Variable used in the model and sources of data b) animal populations (cattle, sheep and goats): local veterinary services; c) number of vaccinated animals, divided by animal species: local veterinary services d) average monthly incidence of infected cattle in previous years: archives of the national BT information system; e) average monthly incidence of infected small ruminants during previous years: archives of the national BT data base; f) frequency distribution of SN antibody titers: archives of the national BT data base; g) monthly number of new cases in the vaccinated population: simulated on the basis of the binomial distribution, the total number of susceptible animals and the incidence of infection in the vaccinated population; h) incidence of infection in free areas surrounding IAs: calculated on the basis of: i. the mean delay from the onset of a new case of infection and the adoption of restrictions; ii. the population living within a circle of 20 km radius from the new case; iii. monthly number of new cases in the vaccinated population; i) prevalence of viraemic animals in the vaccinated population: calculated on the basis of the monthly number of new cases and of the assumed duration of viraemia; j) number of viraemic animals moved to a free area: simulated on the basis of the prevalence of viraemic animals and of 8 different scenarios of animal movement to free areas: i. 500 cattle from the whole of the regional population (no matter if from infected or uninfected areas); ii cattle from the whole of the regional population (no matter if from infected or uninfected areas); iii. 500 sheep and goats from the whole of the regional population (no matter if from infected or uninfected areas); iv sheep and goats from the whole of the regional population (no matter if from infected or uninfected areas); v. 500 cattle from the uninfected areas; vi cattle from the uninfected areas; vii. 500 sheep and goats from the uninfected areas; viii sheep and goats from the uninfected areas; k) four Italian regions have been considered as paradigmatic examples: December

12 i. Tuscany, where >80% of the total animal population has been vaccinated and the incidence of infection during the previous years was low; ii. Sardinia, where >80% of the total animal population has been vaccinated and the incidence of infection during the previous years was high; iii. Latium, where about 50% of the total animal population has been vaccinated; iv. Campania, where a negligible fraction of the total population has been vaccinated. Validation of the model The validation of the model was performed together with the assessment of the role played by the animals without detectable circulating antibody. The model was used to simulate the expected number of positive sentinel animals. In Figure 13, the probability distributions of the number of positive sentinels in Tuscany and Sardinia, respectively, are shown. The observed number of positive sentinels during the last 100 days in Tuscany was 6, that is compatible with both scenarios considered, while in Sardinia the number of observed positive sentinels was 28, that is compatible with immune protection of animals in the absence of circulating antibody. The number of positive sentinels foreseen by the model varied from 26 to 34, with a median value of 30. The model, therefore, was considered to be able to predict the expected monthly number of new cases. In subsequent simulations, therefore, all vaccinated animals were considered protected against the infection. Results If 5,000 bovine animals are chosen at random from any of the five regional populations tested (irrespective of the fact if selected in infected or uninfected areas), the expected number of viraemic animals among them is between 384 and 938, when less than 80% of the domestic ruminant populations are vaccinated (Figures 14 and 15). This, therefore, is the proportion of viraemic animals that would be sent from infected regions to free areas in case of free animal movement. It does not seem possible to reduce these figures to acceptable levels using available risk mitigation measures. When more than 80% of the domestic ruminant populations are vaccinated (Figures 16 and 17), on the contrary, the expected numbers of viraemic cattle sent to free areas is between 0 and 56. If one selects from the population only animals that have been vaccinated and send them only for direct slaughter, preferably during daylight hours, the risk of spread of infection in the receiving regions is virtually nil. If 5,000 sheep are chosen at random from any of the five regional populations tested (irrespective of the fact if selected in infected or uninfected areas), the expected number of viraemic animals among them is between 64 and 429, when less than 80% of the domestic ruminants populations are vaccinated (Figures 18 and 19). This, therefore is the proportion of viraemic animals that would be sent from infected regions to free areas in case of free animal movement. It does not seem possible to reduce these figures to acceptable levels using available risk mitigation measures. When more than 80% of the domestic ruminants populations are vaccinated (Figures 20 and 21), on the contrary, the expected numbers of viraemic sheep sent to free areas is between 0 and 12. If one selects from the population only animals that have been vaccinated and send them only for direct slaughter, preferably during daylight hours, the risk of spread of infection in the receiving regions is virtually nil. December

13 If the animals are selected only in areas were there is no virus circulation, the risk of transmission decreases further. If 5,000 bovine animals are chosen at random from any of the five regional populations tested only from uninfected areas, when less than 80% of the domestic ruminant populations are vaccinated, the expected numbers of viraemic animals sent to free areas is between 28 and 141 when less than 80% of the domestic ruminants populations are is vaccinated (Figures 22 and 23), while is between 0 and 14 when more than 80% of the domestic ruminants populations are vaccinated, in particular when the animals are vaccinated recently (Figures 24 and 25). If 5,000 sheep are chosen at random from any of the five regional population tested only from uninfected areas, when less than 80% of the domestic ruminant populations are vaccinated, the expected numbers of viraemic animals sent to free areas is between 0 and 69 when less than 80% of the domestic ruminants populations are vaccinated (Figures 26 and 27), while it is between 0 and 3 when more than 80% of the domestic ruminants populations are vaccinated, in particular when the animals are vaccinated recently (Figures 28 and 29). In case of sheep it would appear, therefore, that if one selects from the population only animals that have been vaccinated, irrespective of whether the 80% vaccination level has been reached in the domestic ruminant populations and send them only for direct slaughter, preferably during daylight hours, the risk of spread of infection in the receiving regions is virtually nil. It would seem, also, that indeed any movement of vaccinated sheep and cattle from uninfected areas, when vaccination levels in the domestic ruminant populations is more than 80%, will generate only negligible risk of spread of infection in the receiving regions. Conclusions A synthesis of the possible trade of animals from vaccinated to free areas and risk mitigation measures indicated by the results of the risk assessment is summarized in following table. SYNTHESIS OF THE POSSIBLE TRADE OF ANIMALS FROM VACCINATED TO FREE AREAS AND RISK MITIGATION MEASURES ORIGIN OF ANIMALS Regions where more than 80% of the susceptible population is vaccinated (infected and uninfected areas) Regions where less than 80% of the susceptible population is vaccinated (infected and uninfected areas) Regions where more than 80% of the susceptible population is vaccinated (uninfected areas only) Regions where less than 80% of the susceptible population is vaccinated (uninfected areas only) POSSIBILITY OF SHIPMENT OF ANIMALS TO FREE AREAS YES NO YES YES SUGGESTED RISK MITIGATING MEASURE(S) Movement of vaccinated animals only directly to slaughterhouse, preferably during daylight Not Applicable Movement of vaccinated animals only, if recently vaccinated Movement of vaccinated sheep only directly to slaughterhouse, preferably during daylight December

14 REFERENCES European Commission. (2001). Commission Decision 2001/783/EC of 9 November 2001 on protection and surveillance zones in relation to bluetongue, and on rules applicable to movements of animals in and from those zones. Official Journal No. L 293 of 10 November 2001, European Council. (2000). Council Directive 2000/75/EC of 20 November 2000 laying down specific provisions for the control and eradication of bluetongue. Official Journal No. L 327 of 22 December 2000, Hunter P. and Modumo J. (2001). A monovalent attenuated serotype 2 bluetongue virus vaccine confers homologous protection in sheep. Onderstepoort Journal of Veterinary Research. 68, IZSAM - Istituto Zooprofilattico Sperimentale dell Abruzzo e del Molise G. Caporale. (2001). Project on Safety and potency testing of bluetongue vaccines. Contract DG SANCO/00/0127. Final report, 19 pp. December

15 December

16 Table 1 Bluetongue diseased flocks in Italy during following epidemics. NUMBER OF SHEEP AND GOATS NUMBER OF DISEASED FLOCKS REGIONS In diseased flocks Diseased Dead Killed epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic epidemic BASILICATA ,766 5, CALABRIA ,166 52, ,676 10, , ,026 9, CAMPANIA , , , LATIUM , MOLISE APULIA , SARDINIA 6,264 6, ,360,614 1,294,365 2, , , ,624 72, , ,636 4 SICILY , , TUSCANY , TOTAL 6,869 6, ,451,540 1,409,798 41, , ,662 3,496 93,339 72,973 2, , , NOTE:! epidemic: from August 2000 to May 14th 2001;! epidemic: from May 15th to April 14 th 2002;! epidemic: from April 15th December

17 Table 2 Number of sentinel animals tested for bluetongue in Italy during year REGIONS NUMBER OF SENTINEL ANIMALS TESTED IN YEAR 2002 January February March April May June July August September October ABRUZZI , ,199 1,238 1,134 1,038 BASILICATA 1,052 1,473 1,399 1,279 1,267 1,321 1,469 1,027 1, BOLZANO PROV CALABRIA CAMPANIA 2,177 2,021 2,097 2,163 2,312 2,146 2,198 2,025 1,880 1,417 EMILIA ROMAGNA ,872 2,109 2,176 1,844 1,898 FRIULI VENEZIA GIULIA LATIUM 812 1,373 1,951 1,168 1,707 1, LIGURIA 1, , ,080 1,022 1,042 1,091 1,042 1,058 LOMBARDY ,447 1,615 2,018 1,964 1,960 1,370 MARCHE 1,177 1,122 1,375 1,321 1,463 1,390 1,502 1,692 1,587 1,412 MOLISE , PIEDMONT ,424 2,520 2,656 2,525 2,744 2,479 APULIA 2,756 2,540 2,776 2,910 3,088 2,870 2,989 2,994 2,754 2,888 SARDINIA 4,993 3,066 2,766 2,460 2,686 2,883 3,123 2,587 2,914 2,725 SICILY 4,526 3,825 5,061 4,614 5,094 2,711 2,462 2,386 2,272 2,290 TUSCANY 1,189 1,492 1,712 1,650 1, TRENTO PROV UMBRIA 1,103 1,162 1,188 1,212 1,152 1,263 1,291 1,311 1,308 1,199 VALLE D'AOSTA VENETO 1, , ,694 1,723 1,795 1,809 1,319 - TOTAL 23,896 21,790 24,988 23,255 32,982 31,116 31,047 29,925 27,967 22,718 December

18 Table 3 Number of Culicoides collections made in Italy during year REGIONS NUMBER OF CULICOIDES COLLECTIONS MADE IN YEAR 2002 January February March April May June July August September October ABRUZZI BASILICATA BOLZANO PROV CALABRIA CAMPANIA EMILIA ROMAGNA FRIULI VENEZIA GIULIA LATIUM LIGURIA LOMBARDY MARCHE MOLISE PIEDMONT APULIA SARDINIA SICILY TUSCANY TRENTO PROV UMBRIA VALLE D'AOSTA VENETO TOTAL December

19 Table 4 Number of active permanent traps in Italy during year REGIONS NUMBER OF ACTIVE PERMANENT TRAPS IN YEAR 2002 January February March April May June July August September October ABRUZZI BASILICATA BOLZANO PROV CALABRIA CAMPANIA EMILIA ROMAGNA FRIULI VENEZIA GIULIA LATIUM LIGURIA LOMBARDY MARCHE MOLISE PIEDMONT APULIA SARDINIA SICILY TUSCANY TRENTO PROV UMBRIA VALLE D'AOSTA VENETO TOTAL December

20 Table 5 Results of the vaccination campaign against bluetongue in 2002 in Italy. REGIONS SUSCEPTIBLE POPULATION Cattle and Buffaloes Sheep and Goats VACCINATED ANIMALS Cattle and Buffaloes Sheep and Goats OVERALL PER- CENTAGE ABRUZZI 5,912 13,085 5,793 11, % BASILICATA 95, ,000 34, , % CALABRIA 166, ,524 46, , % CAMPANIA 438, ,168 8,886 29, % LATIUM 198, ,351 46, , % MOLISE 57, ,000 3,419 10, % APULIA 186, ,395 8,263 42, % SARDINIA 281,876 3,283, ,471 3,219, % SICILY 381,140 1,238,800 57, , % TUSCANY 59, ,419 40, , % TOTAL 1,871,419 7,304, ,695 4,709, % December

21 Figure 1 Territories where the vaccination against bluetongue is compulsory. VALLE D'AOSTA PIEMONTE TRENTINO-ALTO ADIGE FRIULI-VENEZIA GIULIA LOMBARDIA VENETO Serotype of the vaccine BTV 2 BTV 2 and 9 LIGURIA EMILIA-ROMAGNA TOSCANA MARCHE UMBRIA ABRUZZI LAZIO MOLISE PUGLIA CAMPANIA BASILICATA SARDEGNA CALABRIA SICILIA December

22 Figure 2 Geographical distribution of permanent traps for Culicoides in Italy and C. imicola catching in year Presence of C. imicola Absence of C. imicola December

23 Figure 3 Results of the vaccination campaign against bluetongue in 2002 in Italy. Vaccination percentage 0 % < 40 % 40 % % 60 % % 80 % December

24 Figure 4 Geographical distribution of Infected Areas (IAs) in Sardinia and Tuscany during and epidemic EPIDEMIC EPIDEMIC EMONTE LIGURIA EMILIA-ROM AGNA MONTE LIGURIA EMILIA-ROM AGNA TOSCANA TOSCANA UM UM SARDEGNA SARDEGNA December

25 Figure 5 Geographical distribution of Infected Holdings (IHs) in Sardinia and Tuscany during and epidemic EPIDEMIC EPIDEMIC EM MONTE LIGURIA EMILIA-ROMAGNA MONTE LIGURIA EMILIA-ROMAGNA AGNA TOSCANA TOSCANA UMB B UM SARDEGNA SARDEGNA December

26 Figure 6 Temporal distribution of incidence of seroconversion in sentinel animals and cumulative percentage of vaccinated animals in Sardinia, Tuscany, Lazio and Puglia Regions. SARDINIA TUSCANY 100% 1,4% 100% 1,4% 90% 80% 70% 60% 50% 40% 30% 20% % OF VACCINATION COVERAGE 10% 1,2% 1,0% 0,8% 0,6% 0,4% 0,2% 90% 80% 70% 60% 50% 40% 30% 20% INCIDENCE OF SEROCONVERSIONS IN SENTINELS % OF VACCINATION COVERAGE INCIDENCE OF SEROCONVERSIONS IN SENTINELS 10% 1,2% 1,0% 0,8% 0,6% 0,4% 0,2% 0% 8/2001 9/ / / /2001 1/2002 2/2002 3/2002 4/2002 5/2002 6/2002 7/2002 8/2002 9/ /2002 0,0% 0% 8/2001 9/ / / /2001 1/2002 2/2002 3/2002 4/2002 5/2002 6/2002 7/2002 8/2002 9/ /2002 0,0% MONTHS MONTHS Percentage of vaccinated animals (cumulative value) Percentage of vaccinated animals (cumulative value) Incidence of seroconversions in sentinel animals Incidence of seroconversions in sentinel animals LATIUM APULIA 100% 1,4% 100% 1,4% 90% 80% 70% 60% 50% 40% 30% 20% % OF VACCINATION COVERAGE 10% 1,2% 1,0% 0,8% 0,6% 0,4% 0,2% 90% 80% 70% 60% 50% 40% 30% 20% INCIDENCE OF SEROCONVERSIONS IN SENTINELS % OF VACCINATION COVERAGE INCIDENCE OF SEROCONVERSIONS IN SENTINELS 10% 1,2% 1,0% 0,8% 0,6% 0,4% 0,2% 0% 8/2001 9/ / / /2001 1/2002 2/2002 3/2002 4/2002 5/2002 6/2002 7/2002 8/2002 9/ /2002 0,0% 0% 8/2001 9/ / / /2001 1/2002 2/2002 3/2002 4/2002 5/2002 6/2002 7/2002 8/2002 9/ /2002 0,0% MONTHS MONTHS Percentage of vaccinated animals (cumulative value) Percentage of vaccinated animals (cumulative value) Incidence of seroconversions in sentinel animals Incidence of seroconversions in sentinel animals December

27 Figure 7 location of clinical outbreaks and positive sentinel holdings detected in Sardinia from August 20 to November 28, Clinical outbreaks Positive sentinel holdings All infected holdings December

28 Figure 8 location of all negative (green dots) and positive (red dots) sentinel holdings detected in Sardinia from August 20 to November 28, Sentinel holdings Negative Positive December

29 Figure 9 - Probability distribution of the incidence of infection according to the results obtained testing a sample of animals. 100% Probability that the incidence be >x 80% 60% 40% 20% 0% 0% 5% 10% 15% 20% 25% 30% x n=58 pos.=0 n=58 pos.=1 n=30 pos.=0 n=30 pos.=1 n=10 pos.=0 n=10 pos.=1 December

30 Figure 10 - The definition of a homogeneous neighborhood. Sentinel holdings Negative Positive December

31 Figure 11 - Areas in Sardinia where a probability 5% exists that the incidence of infection is 5% (red areas), compared to the results of the sentinel herd testing. December

32 Figure 12 Percentage of vaccinated animals resulted positive to sero-neutralization (total number of animals tested: n = 1,590). 100% 90% 80% Percent positives 70% 60% 50% 40% 30% 20% 10% 0% Days post vaccination Cattle (n = 346) Sheep (n = 931) Goats (n = 313) December

33 Figure 13: Expected numbers of positive sentinels in Tuscany and in Sardinia according to the hypotheses that (1) all vaccinated animals are protected against the infection or (2) only animals with an antibody titer of at least 1:10 are protected against the infection. Probability that the number of pos. sent. be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Sardinia; vaccinated are protected Tuscany; vaccinated are protected Sardinia; titre 1:10 are protected Tuscany; titre 1:10 are protected Figure 14: Expected number of viraemic cattle moved from Latium to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Latium; N=500 Latium; N=5000 December

34 Figure 15: Expected number of viraemic cattle moved from Campania to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Campania; N=500 Campania; N=5000 Figure 16: Expected number of viraemic cattle moved from Tuscany to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Tuscany; N=500 Tuscany; N=5000 December

35 Figure 17: Expected number of viraemic cattle moved from Sardinia to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Sardinia; N=500 Sardinia; N=5000 Figure 18: Expected number of viraemic small ruminants moved from Latium to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Latium; N=500 Latium; N=5000 December

36 Figure 19: Expected number of viraemic small ruminants moved from Campania to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Campania; N=500 Campania; N=5000 Figure 20: Expected number of viraemic small ruminants moved from Tuscany to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Tuscany; N=500 Tuscany; N=5000 December

37 Figure 21: Expected number of viraemic small ruminants moved from Sardinia to free areas in case of a random selection of animals from the whole of the regional population (no matter if from infected or uninfected areas). Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Sardinia; N=500 Sardinia; N=5000 Figure 22: Expected number of viraemic cattle moved from uninfected free areas of Latium to free areas. Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Latium; N=500 Latium; N=5000 December

38 Figure 23: Expected number of viraemic cattle moved from uninfected free areas of Campania to free areas. Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Campania; N=500 Campania; N=5000 Figure 24: Expected number of viraemic cattle moved from uninfected free areas of Tuscany to free areas. Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Tuscany; N=500 Tuscany; N=5000 December

39 Figure 25: Expected number of viraemic cattle moved from uninfected free areas of Sardinia to free areas. Probability that the number of inf. cattle be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Sardinia; N=500 Sardinia; N=5000 Figure 26: Expected number of viraemic small ruminants moved from uninfected free areas of Latium to free areas. Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Latium; N=500 Latium; N=5000 December

40 Figure 27: Expected number of viraemic small ruminants moved from uninfected free areas of Campania to free areas. Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Campania; N=500 Campania; N=5000 Figure 28: Expected number of viraemic small ruminants moved from uninfected free areas of Tuscany to free areas. Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Tuscany; N=500 Tuscany; N=5000 December

41 Figure 29: Expected number of viraemic small ruminants moved from uninfected free areas of Sardinia to free areas. Probability that the number of inf. sheep be > 1 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, ,5 1 1,5 2 2,5 3 3,5 Sardinia; N=500 Sardinia; N=5000 December