BLUETONGUE IN · During years from 2000 and 2002, Italy experienced the largest bluetongue (BT)...

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

Bruxelles, 3 Dicembre 2002

December 2002 I

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. ............................................................................................................ 4 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 1

INTRODUCTION During years from 2000 and 2002, Italy experienced the largest bluetongue (BT) epidemics in Europe. During 2000-2001 BT epidemic (from August 2000 to May 14th 2001) the disease involved 3 Ital-ian 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 2001-2002 BT epidemic (from May 15th to April 14th 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 to-tal 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 (2002-2003 BT epidemic; from April 15th 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, respec-tively. 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 circula-tion 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 con-sequences of the infection without vaccination. The National Reference Centers for Veterinary Epidemiology and for Exotic Diseases, there-fore, carried out a quantitative risk analysis in April 2001 (available in Italian language on the web site: www.izs.it) 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 2002 2

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 Feb-ruary 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, conse-quently, 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 at-tempt 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 Onderster-poort�s live virus vaccine in cattle was supported by safety, potency and reversion to viru-lence studies on bovine animals carried out by the National Reference Centers. Despite the vaccination Order issued by the Ministry of Health on May 11th 2001, not a single dose of vaccine was employed during late spring and early summer 2001. 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 vac-cination 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 2002. At present the vaccination of all domestic ruminant populations is compulsory in the re-stricted zones (as defined by the Commission Decision 2001/783/EC) and in some others terri-tories 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, im-plemented 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 condi-tions;

December 2002 3

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 examina-tion, serology, virology on ruminants and captured midges;

b) definition of �infected area� (IA) as the territory of all municipalities within a 20 km ra-dius 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 Com-mission 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 sur-veys feed a BT management information system available on the Internet (www.izs.it) 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 labo-

ratory 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 ani-mal 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 sus-ceptible 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 2001-2002 epidemic to 10 in 2002-2003, and in Tuscany after the 158 outbreaks in 2001-2002 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 2002 4

cany (Figure 4). IHs, in fact, are scattered all over the territories but consistent clusters of in-fection are absent (Figure 5). Considering the incidence of seroconversion in sentinel animals, furthermore, makes the re-duction of BTV circulation induced by vaccination in Sardinia and Tuscany quite evident. Comparison with Regions where the vaccination campaign did not reach the proposed ob-jectives 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 fat-tened 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 � vec-tors 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 as-sessed 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 popu-lations induced by vaccination in the same areas;

2. proposed a new method to define BT infected areas when at least 80% of the do-mestic 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 re-strictions in the « infected area » are enforced for as long as the surveillance proves the exis-tence of viral activity and for 100 days after the last evidence of virus circulation. Virus circula-tion 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 re-duced on the basis of epidemiological, geographical, ecological or meteorological circum-stances. 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 2001-2002 epidemic (Figure 4).

December 2002 5

In Sardinia no ruminant was vaccinated before the 2001 � 2002 epidemic when a total of 6,090 outbreaks were recorded. Since the beginning of the 2002 � 2003 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 hold-ings 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 ter-ritories 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 ra-dius 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 observa-tional 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 ani-mals/vectors being infected from the source observed). It is likely that the extension of « pro-tection 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 sus-ceptible. 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. Nega-tive 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 rumi-nant population is vaccinated.

Scientific basis For the purpose of BT serological surveillance Italy has been divided into a grid of 400 km2 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 2002 6

positive animal being detected, when the incidence of infection is at least 5% or more, ac-cording to the binomial distribution. Given these assumptions, an epidemiologically homogeneous neighborhood can be de-fined, for each point on a map, and, based on the results obtained in the sentinel animals liv-ing 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 infection1 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 sen-tinel 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 proce-dure 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 georefer-enced herd within the map), is necessary to interpolate all neighborhood probabilities calcu-lated by the regular Krieging method. In Figure 11, the results of this interpolation are com-pared 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 main-tained. 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 2002 7

- 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 re-striction has been assessed considering different scenarios, according to percentage of ani-mal 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 vacci-nated animals is quite limited. Some relevant information regarding immunity levels in vacci-nated 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 mani-fest a detectable viraemia. These results are confirmed also in cattle by an experi-ment carried out in Italy by the National Reference Centres for Veterinary Epidemiol-ogy and Exotic Diseases (unpublished data), where 4 cows, vaccinated for BTV sero-type 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 at-tempted repeatedly - every 3 days for the first 7 weeks, and then weekly - with nega-tive results; ! field data collected by the National Reference Centers for Veterinary Epidemiology

and Exotic Diseases suggest that more than 80% of vaccinated animals have anti-body detectable by sero-neutralization for, at least, 80-90 days after vaccination. The same data indicate also that a solid immunity is reached after 20-30 days after vacci-nation (Figure 12); ! detectable viraemia due to the vaccine is rare, does not last more that 6-8 days and

titers observed are always below 103/ml that is considered the threshold for vector in-fection (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 resis-

tance to infection in field condition; ! the existence of vaccinated animal resistant to infection in field condition in the ab-

sence of circulating antibody titer. Assumptions and variable used The following assumption and variables has been, therefore, considered in the risk assess-ment:

1. Assumptions

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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 cir-

culating antibody titer; ii. only animals with serum-neutralizing antibody titer of at least 1:10 are pro-

tected 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 vacci-nated 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 na-

tional BT information system; e) average monthly incidence of infected small ruminants during previous years: ar-

chives 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 in-

fected or uninfected areas); ii. 5000 cattle from the whole of the regional population (no matter if from in-

fected or uninfected areas); iii. 500 sheep and goats from the whole of the regional population (no matter if

from infected or uninfected areas); iv. 5000 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. 5000 cattle from the uninfected areas; vii. 500 sheep and goats from the uninfected areas; viii. 5000 sheep and goats from the uninfected areas;

k) four Italian regions have been considered as paradigmatic examples:

December 2002 9

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 vacci-

nated. 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 pro-portion 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 lev-els 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 (irre-spective of the fact if selected in infected or uninfected areas), the expected number of vi-raemic animals among them is between 64 and 429, when less than 80% of the domestic ru-minants populations are vaccinated (Figures 18 and 19). This, therefore is the proportion of vi-raemic 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 2002 10

If the animals are selected only in areas were there is no virus circulation, the risk of transmis-sion 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 popu-lations 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 vacci-nated, 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 ani-mals 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, pref-erably 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 un-infected 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 POSSIBILITY OF

SHIPMENT OF ANIMALS TO FREE AREAS

SUGGESTED RISK MITIGATING MEASURE(S)

Regions where more than 80% of the susceptible population is vaccinated (infected and uninfected areas)

YES Movement of vaccinated animals only directly to slaughterhouse, preferably during daylight

Regions where less than 80% of the susceptible population is vaccinated (infected and uninfected areas)

NO Not Applicable

Regions where more than 80% of the susceptible population is vaccinated (uninfected areas only)

YES Movement of vaccinated animals only, if recently vaccinated

Regions where less than 80% of the susceptible population is vaccinated (uninfected areas only)

YES Movement of vaccinated sheep only directly to slaughterhouse, preferably during daylight

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REFERENCES European Commission. (2001). Commission Decision 2001/783/EC of 9 November 2001 on pro-tection and surveillance zones in relation to bluetongue, and on rules applicable to move-ments of animals in and from those zones. Official Journal No. L 293 of 10 November 2001, 42 � 46. 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, 74 � 83. Hunter P. and Modumo J. (2001). A monovalent attenuated serotype 2 bluetongue virus vac-cine confers homologous protection in sheep. Onderstepoort Journal of Veterinary Research. 68, 331 - 333. 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 2002 1

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2000

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2001

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2002

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3 ep

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2000

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1 ep

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2001

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2 ep

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2002

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3 ep

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2000

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2001

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2002

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2000

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2001

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2002

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2000

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2001

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2 ep

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2002

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3 ep

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BASI

LIC

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-

63

5

9

-

4,76

6

5,

145

-

152

22

3

-

1

6

96

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-

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CA

LABR

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589

42

7

14

8

9,16

6

52,

722

68

4

15,

676

1

0,17

6

77

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6,62

4

236

-

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13,0

26

9,

877

7

7

CA

MPA

NIA

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1

24

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20,

711

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1,96

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492

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11

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-

-

1

-

-

16

-

-

1

-

-

-

-

-

-

APU

LIA

-

-

1

4

-

-

1,

907

-

-

21

7

-

-

27

-

-

1

SARD

INIA

6,26

4

6,

090

1

0

1,3

60,6

14

1,2

94,3

65

2,

120

246

,908

239

,178

2

8

46,

624

7

2,50

2

5

213

,026

159

,636

4

SIC

ILY

16

6

47

1,76

0

853

1

0,17

0

175

2

9

959

9

1

29

83

3

94

-

-

TUSC

AN

Y

-

158

-

-

3

3,98

8

-

-

693

-

-

11

9

-

-

560

-

TOTA

L

6,86

9

6,

807

40

4

1,4

51,5

40

1,4

09,7

98

41,

434

262

,759

250

,662

3,49

6

93,

339

7

2,97

3

2,

481

426

,146

170

,429

28

3

NO

TE:

!

2000

-200

1 ep

idem

ic: f

rom

Aug

ust 2

000

to M

ay 1

4th

2001

; !

2001

-200

2 ep

idem

ic: f

rom

Ma

y 15

th to

Ap

ril 1

4th

2002

; !

2002

-200

3 ep

idem

ic: f

rom

Ap

ril 1

5th

2002

.

December 2002 3

Table 2 � Number of sentinel animals tested for bluetongue in Italy during year 2002.

NUMBER OF SENTINEL ANIMALS TESTED IN YEAR 2002 REGIONS

January February March April May June July August September October

ABRUZZI 315 537 785 1,128 868 991 1,199 1,238 1,134 1,038

BASILICATA

1,052 1,473 1,399 1,279 1,267 1,321 1,469 1,027 1,141 916

BOLZANO PROV. - - - - 790 816 868 747 328 -

CALABRIA 829 474 962 313 960 575 592 725 850 376

CAMPANIA 2,177 2,021 2,097 2,163 2,312 2,146 2,198 2,025 1,880 1,417

EMILIA ROMAGNA 374 420 273 659 955 1,872 2,109 2,176 1,844 1,898

FRIULI VENEZIA GIULIA 750 726 802 829 395 -

LATIUM 812 1,373 1,951 1,168 1,707 1,855 596 443 470 383

LIGURIA 1,028 972 1,095 986 1,080 1,022 1,042 1,091 1,042 1,058

LOMBARDY - - - 15 1,447 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 127 449 481 469 924 868 792 1,037 914 794

PIEDMONT 377 16 59 18 2,424 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 1,387 993 517 465 356 217

TRENTO PROV. - - - - 521 597 615 532 443 -

UMBRIA 1,103 1,162 1,188 1,212 1,152 1,263 1,291 1,311 1,308 1,199

VALLE D'AOSTA - - - - 413 359 412 322 312 258

VENETO 1,061 848 1,008 890 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 2002 4

Table 3 � Number of Culicoides collections made in Italy during year 2002.

NUMBER OF CULICOIDES COLLECTIONS MADE IN YEAR 2002 REGIONS


ABRUZZI 33 32 32 30 29 56 45 32 34 28

BASILICATA 22 24 23 23 37 30 65 55 50 45

BOLZANO PROV. 16 13 21 31 34 27 34 27 14 -

CALABRIA 47 41 42 31 35 44 57 40 40 25

CAMPANIA 10 5 12 28 47 47 65 37 44 56 EMILIA ROMAGNA 45 46 5 32 59 65 81 88 89 39 FRIULI VENEZIA GIULIA 8 25 29 31 31 25 37 30 23 -

LATIUM 23 28 33 33 46 201 65 51 44 60

LIGURIA 13 21 19 23 24 22 27 42 42 22

LOMBARDY 53 64 10 41 71 72 102 95 90 36

MARCHE 24 18 21 32 36 32 36 33 33 28

MOLISE - - - - 3 4 5 4 12 22

PIEDMONT 58 79 75 84 88 82 97 95 76 42

APULIA 40 43 43 43 42 38 59 35 96 78

SARDINIA 54 64 67 69 65 66 66 53 14 1

SICILY 29 28 24 22 66 69 116 65 64 45

TUSCANY 57 59 65 63 85 88 96 90 77 70

TRENTO PROV. 4 12 15 17 18 16 22 18 12 -

UMBRIA 27 24 26 34 35 33 35 35 32 29

VALLE D'AOSTA 5 4 10 10 11 9 14 13 6 4

VENETO 46 48 46 53 65 64 73 69 37 6

TOTAL 614 678 618 730 927 1.090 1.197 1.007 929 636

December 2002 5

Table 4 � Number of active permanent traps in Italy during year 2002.

NUMBER OF ACTIVE PERMANENT TRAPS IN YEAR 2002 REGIONS


ABRUZZI 5 5 4 4 3 4 4 4 5 5

BASILICATA 4 5 5 5 6 6 8 6 7 8

BOLZANO PROV. 3 4 6 7 8 8 8 7 8 -

CALABRIA 11 12 11 10 10 12 11 10 10 8

CAMPANIA 2 1 3 9 10 11 10 9 9 7 EMILIA ROMAGNA 12 11 1 11 14 16 16 16 16 16 FRIULI VENEZIA GIULIA 3 7 8 8 8 8 8 8 8 -

LATIUM 8 11 9 9 13 10 10 11 10 11

LIGURIA 6 6 6 6 6 6 6 6 6 6

LOMBARDY 8 9 1 8 9 10 10 9 8 8

MARCHE 5 5 5 8 8 8 8 8 8 8

MOLISE - - - - 1 1 1 2 3 3

PIEDMONT 15 19 18 19 20 21 20 20 20 18

APULIA 6 6 6 7 7 9 8 8 8 8

SARDINIA 18 20 20 21 21 19 17 15 2 -

SICILY 6 6 6 6 18 17 20 15 14 15

TUSCANY 15 15 15 14 16 16 16 15 16 13

TRENTO PROV. 1 4 4 5 5 5 5 5 5 -

UMBRIA 4 4 4 4 4 4 3 3 3 3

VALLE D'AOSTA 2 2 3 3 3 3 3 3 2 2

VENETO 14 14 12 13 14 15 15 16 14 12

TOTAL 148 166 147 177 204 209 207 196 182 151

December 2002 6

Table 5� Results of the vaccination campaign against bluetongue in 2002 in Italy.

SUSCEPTIBLE POPULATION VACCINATED ANIMALS REGIONS Cattle and Buffa-

loes Sheep and Goats Cattle and Buffa-loes Sheep and Goats

OVERALL PER-CENTAGE

ABRUZZI 5,912 13,085 5,793 11,520 91.1%BASILICATA 95,000 401,000 34,443 239,081 55.1%CALABRIA 166,126 582,524 46,643 253,664 40.1%CAMPANIA 438,856 319,168 8,886 29,097 5.0%LATIUM 198,383 576,351 46,892 367,265 53.5%MOLISE 57,800 107,000 3,419 10,749 8.6%APULIA 186,619 408,395 8,263 42,474 8.5%SARDINIA 281,876 3,283,247 241,471 3,219,422 97.1%SICILY 381,140 1,238,800 57,921 189,080 15.2%TUSCANY 59,707 375,419 40,964 347,075 89.2%

TOTAL 1,871,419 7,304,989 494,695 4,709,427 56.7%

December 2002 7

Figure 1 � Territories where the vaccination against bluetongue is compulsory.

ABRUZZIABRUZZIABRUZZIABRUZZIABRUZZI

BASILICATABASILICATABASILICATABASILICATABASILICATA

CALABRIACALABRIACALABRIACALABRIACALABRIA

CAMPANIACAMPANIACAMPANIACAMPANIACAMPANIA

EMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNA

FRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIA

LAZIOLAZIOLAZIOLAZIOLAZIO

LIGURIALIGURIALIGURIALIGURIALIGURIA

LOMBARDIALOMBARDIALOMBARDIALOMBARDIALOMBARDIA

MARCHEMARCHEMARCHEMARCHEMARCHE

MOLISEMOLISEMOLISEMOLISEMOLISE

PIEMONTEPIEMONTEPIEMONTEPIEMONTEPIEMONTE

PUGLIAPUGLIAPUGLIAPUGLIAPUGLIA

SARDEGNASARDEGNASARDEGNASARDEGNASARDEGNA

TOSCANATOSCANATOSCANATOSCANATOSCANA

TRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGE

UMBRIAUMBRIAUMBRIAUMBRIAUMBRIA

VALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTA VENETOVENETOVENETOVENETOVENETO

SICILIASICILIASICILIASICILIASICILIA

BTV 2

BTV 2 and 9

Serotype of the vaccine

ABRUZZIABRUZZIABRUZZIABRUZZIABRUZZI

BASILICATABASILICATABASILICATABASILICATABASILICATA

CALABRIACALABRIACALABRIACALABRIACALABRIA

CAMPANIACAMPANIACAMPANIACAMPANIACAMPANIA

EMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNA

FRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIAFRIULI-VENEZIA GIULIA

LAZIOLAZIOLAZIOLAZIOLAZIO


LOMBARDIALOMBARDIALOMBARDIALOMBARDIALOMBARDIA

MARCHEMARCHEMARCHEMARCHEMARCHE

MOLISEMOLISEMOLISEMOLISEMOLISE

PIEMONTEPIEMONTEPIEMONTEPIEMONTEPIEMONTE

PUGLIAPUGLIAPUGLIAPUGLIAPUGLIA



TRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGETRENTINO-ALTO ADIGE

UMBRIAUMBRIAUMBRIAUMBRIAUMBRIA

VALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTAVALLE D'AOSTA VENETOVENETOVENETOVENETOVENETO

SICILIASICILIASICILIASICILIASICILIA

BTV 2

BTV 2 and 9

Serotype of the vaccine

December 2002 8

Figure 2 � Geographical distribution of permanent traps for Culicoides in Italy and C. imi-cola catching in year 2002.

Presence of C. imicola

Absence of C. imicola





December 2002 9

Figure 3 � Results of the vaccination campaign against bluetongue in 2002 in Italy.

Vaccination percentage

0 %< 40 %40 % - 59.9 %60 % - 79.9 %≥ 80 %

Vaccination percentage

0 %< 40 %40 % - 59.9 %60 % - 79.9 %≥ 80 %

December 2002 10

Figure 4 � Geographical distribution of Infected Areas (IAs) in Sardinia and Tuscany during 2001-2002 and 2002-2003 epidemic.

EMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNALIGURIALIGURIALIGURIALIGURIALIGURIA

MONTEONTEMONTEMONTEMONTE



UMUMUMUMUM


EMONTEMONTEMONTEMONTEMONTE



UMUMUMUMUM

2001 � 2002 EPIDEMIC 2002 � 2003 EPIDEMICEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNA





UMUMUMUMUM


EMONTEMONTEMONTEMONTEMONTE



UMUMUMUMUM

2001 � 2002 EPIDEMIC 2002 � 2003 EPIDEMIC

December 2002 11

Figure 5 � Geographical distribution of Infected Holdings (IHs) in Sardinia and Tuscany dur-ing 2001-2002 and 2002-2003 epidemic.


EMONTEMONTEEMONTEEMONTEEMONTE



UMBUMBUMBUMBUMB





UMUMUMUMUM

2001 � 2002 EPIDEMIC 2002 � 2003 EPIDEMICEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNAEMILIA-ROMAGNA


EMONTEMONTEEMONTEEMONTEEMONTE



UMBUMBUMBUMBUMB





UMUMUMUMUM

2001 � 2002 EPIDEMIC 2002 � 2003 EPIDEMIC

Dec

embe

r 200

2 12

Figur

e 6

� Te

mpo

ral d

istrib

utio

n of

inci

den

ce o

f ser

ocon

versi

on in

sen

tinel

ani

ma

ls a

nd c

umul

ativ

e pe

rcen

tage

of v

acc

ina

ted

ani

mal

s in

Sar

dini

a,

Tusc

any,

La

zio a

nd P

uglia

Reg

ions

. SARD

INIA

TUSC

AN

Y

LATIU

MA

PULI

A

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2

MO

NTHS

% OF VACCINATION COVERAGE

0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%

INCIDENCE OF SEROCONVERSIONS IN SENTINELS

Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2

MO

NTHS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2M

ONT

HS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2M

ONT

HS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

SARD

INIA

TUSC

AN

Y

LATIU

MA

PULI

A

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2

MO

NTHS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2

MO

NTHS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2M

ONT

HS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

0%10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

8/20

019/

2001

10/2

001

11/2

001

12/2

001

1/20

022/

2002

3/20

024/

2002

5/20

026/

2002

7/20

028/

2002

9/20

0210

/200

2M

ONT

HS


0,0%

0,2%

0,4%

0,6%

0,8%

1,0%

1,2%

1,4%


Perc

enta

ge o

f vac

cina

ted

anim

als

(cum

ulat

ive

valu

e)

Inci

denc

e of

ser

ocon

vers

ions

in s

entin

el a

nim

als

December 2002 13

Figure 7 � location of clinical outbreaks and positive sentinel holdings detected in Sardinia from August 20 to November 28, 2002.

Clinical outbreaks Positive sentinel holdings

All infected holdings

Clinical outbreaks Positive sentinel holdings

All infected holdings

December 2002 14

Figure 8 � location of all negative (green dots) and positive (red dots) sentinel holdings de-tected in Sardinia from August 20 to November 28, 2002.

Sentinel holdingsNegativePositive


December 2002 15

Figure 9 - Probability distribution of the incidence of infection according to the results ob-tained testing a sample of animals.

0%

20%

40%

60%

80%

100%

0% 5% 10% 15% 20% 25% 30%

x

Prob

abili

ty th

at th

e in

cide

nce

be >

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 2002 16

Figure 10 - The definition of a homogeneous neighborhood.




December 2002 17

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 2002 18

Figure 12 � Percentage of vaccinated animals resulted positive to sero-neutralization (total number of animals tested: n = 1,590).

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

11-20 21-30 31-40 41-50 51-60 61-70 71-80 81-90

Days post vaccination

Perc

ent p

ositi

ves

Cattle (n = 346) Sheep (n = 931) Goats (n = 313)

December 2002 19

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.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 10 20 30 40 50 60

X

Prob

abili

ty th

at th

e nu

mbe

r of

pos

. sen

t. be

> X

Sardinia; vaccinated are protected Sardinia; titre 1:10 are protectedTuscany; vaccinated 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 in-fected or uninfected areas).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 100 200 300 400 500 600

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X

Latium; N=500 Latium; N=5000

December 2002 20

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).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 100 200 300 400 500 600 700 800 900 1000

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X

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 in-fected or uninfected areas).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12 14

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X

Tuscany; N=500 Tuscany; N=5000

December 2002 21

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 in-fected or uninfected areas).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 10 20 30 40 50 60

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X

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).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 20 40 60 80 100 120 140 160

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


December 2002 22

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 mat-ter if from infected or uninfected areas).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 50 100 150 200 250 300 350 400 450 500

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


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).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 1 2 3

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


December 2002 23

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).

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12 14

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


Figure 22: Expected number of viraemic cattle moved from uninfected free areas of Latium to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 10 20 30 40 50 60 70 80 90 100

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X


December 2002 24

Figure 23: Expected number of viraemic cattle moved from uninfected free areas of Cam-pania to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 20 40 60 80 100 120 140 160

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X


Figure 24: Expected number of viraemic cattle moved from uninfected free areas of Tuscany to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 2 4 6 8 10 12 14 16

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X


December 2002 25

Figure 25: Expected number of viraemic cattle moved from uninfected free areas of Sardinia to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 1 2 3 4 5 6 7 8 9 10

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

catt

le b

e >

X


Figure 26: Expected number of viraemic small ruminants moved from uninfected free areas of Latium to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 5 10 15 20 25 30

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


December 2002 26

Figure 27: Expected number of viraemic small ruminants moved from uninfected free areas of Campania to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 10 20 30 40 50 60 70 80

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


Figure 28: Expected number of viraemic small ruminants moved from uninfected free areas of Tuscany to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 1 2 3

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


December 2002 27

Figure 29: Expected number of viraemic small ruminants moved from uninfected free areas of Sardinia to free areas.

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1

0 0,5 1 1,5 2 2,5 3 3,5

X

Prob

abili

ty th

at th

e nu

mbe

r of

inf.

shee

p be

>

X


BLUETONGUE IN · During years from 2000 and 2002, Italy experienced the largest bluetongue (BT)...

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Transcript of BLUETONGUE IN · During years from 2000 and 2002, Italy experienced the largest bluetongue (BT)...