1 Ministry of Production Secretariat of Agriculture, Livestock, Fisheries

and Food National Service for Agrifood Health and Quality

SENASA



## ANNEX

FMD SERO-EPIDEMIOLOGICAL SURVEILLANCE

SEROLOGICAL SAMPLING 2005-2006

NATIONAL DIRECTORATE FOR ANIMAL HEALTH EPIDEMIOLOGY DIRECTORATE



### ARGENTINA

January 20072 INTRODUCTION:

FMD epidemiological surveillance implemented by SENASA is in line with Animal Health World Organization (OIE) recommendations to evidence an area is free of the disease (Annex 3.8.7 – Guidelines for FMD Surveillance). Sero-epidemiological surveillance is conducted annually to prove lack of viral circulation or infection, whether in zones with or without vaccination. In addition, immunity level conferred through vaccination is estimated in zones where vaccination is practiced. The Epidemiology Office, reporting to SENASA’s Animal Health Directorate, is responsible for survey layout, within the scope of the Epidemiology Advisory Committee. The latter is a body formed by epidemiologists from other research institutions (INTA, CONICET and Schools of Veterinary Sciences). Samples are taken and shipped by SENASA local veterinarians and regional supervisors and processed at the Animal Laboratory, reporting to SENASA’s Laboratories and Technical Control Directorate (DILAB).

SAMPLING LAYOUT

According to OIE recommendations for demonstrating FMD freedom in zones or countries with or without vaccination, sero-epidemiological sampling is implemented in two stages, namely:

- a statistically-designed initial sampling, which comprises all agricultural exploitations of the country, and

- an additional sampling (along with other investigations) in farms where animals reacting to the initial sampling were found. The purpose of additional sampling is to confirm or rule out the first result.

1. Objective:

a) Detecting viral circulation or infection by FMD virus (FMDV) throughout the Argentine Territory.

b) Estimating immunity level of cattle population in areas where vaccination against FMD is practiced.

2. Variables to be measured:

2.1 Presence of antibodies against FMDV non-capsidal proteins in vaccinated animals and antibodies against structural proteins (SP) in non-vaccinated animals, as indicator of viral infection or circulation.

2.2. Antibody titres against FMDV structural proteins in vaccinated cattle, as indicator of population immunity level.

3. Sampling framework:

3.1. Sampling comprises all livestock farms registered in the National Health Register3 of Agricultural Producers (RENSPA) throughout the country. In order to adjust sampling objectives to different epidemiological situations, the country was divided into zones, according to the following parameters:

- Animal density

- Composition of cattle population(steer/cow ratio).

- Animal movements (movements in and out).

- Geographical and political-administrative characteristics.

- Effectiveness of vaccination rounds

- Risk areas (border areas).

- Surveillance zones (in free areas)

- Results of previous serological samplings

Zones detailed below were determined following these criteria ( see Map 1 ):

1. Central-Mesopotamia and NOA-Cuyo 2. Fattening 3. Border 4. Northern A Patagonia 5. Northern B Patagonia 6. Southern Patagonia4 Map 1: Zoning

4. Animals and categories sampled: Criteria for selecting species to be sampled in each zone were preponderance of each susceptible species as well as sampling effectiveness. In areas with vaccinated cattle, the bovine species was chosen due to its preponderance and also for practical purposes, since sampling was conducted at the same time of vaccination. In areas without vaccination, sheep/goat were chosen due to their preponderance.

4.1. Cattle: the following categories were sampled in all zones, except for Southern Patagonia region.

- Category 1: 6 to 12 months old.5 - Category 2: 12 to 24 months old.

4.2. Sheep/goats: of any category and age; samples were taken only in Southern and Northern B Patagonia regions.

All sampled animals were identified with official numbered tags (snap button tag).

5. Estimation of sample size: Sampling is conducted in two stages. Herd number, from which samples are to be taken (Formula No1), is calculated first, and then the number of individuals per herd (formula No2).

Formula No 1 : Number of herds required (nr)



## ( )      

−

− ×      

− − = 2 1 1 1 1 e N NC n r e r

Where

NC Confidence level (to detect at least one positive animal within the population)

e Number of affected herds that may be detected as such within the population. This value is obtained by multiplying number of herds within the population to be surveyed (Nr) by expected prevalence of positive herds and by confidence level to be established to determine number of individuals to be sampled per herd.

N r Number of herds within the population to be surveyed

Formula N°2: Number of individuals to be sampled per herd (n i ):



## ( )      

−

− ×      

− − = 2 1 1 1 1 e N NC n i e i

Where

NC Confidence level (to detect at least one positive animal per farm)

e Number of individuals within the event that may be detected per herd. This value is obtained by multiplying number of individuals per herd (Ni) by detectable prevalence, which is the result of the product between expected prevalence (p) and sensitivity (Se) of diagnostic method (N * p * Se)

N r Average number of individuals per herd

Note: assumptions used vary from one zone to another, as explained below.6 6. Layout for viral circulation per zone:

6.1. Central- Mesopotamia and NOA-Cuyo zones:

It is comprised by Central, Mesopotamia, NOA and Cuyo regions set out in the FMD Eradication Plan 2001, except for the locations included in Fattening and Border

zones. Assumptions to detect viral activity within this zone were made taking into account historic behavior of FMD in this region and data obtained from latest samplings, namely:

- Prevalence of infected farms: 1%

- Prevalence within the farm : 10%

- Confidence level: 95%

On the basis of these assumptions, 313 farms should be selected and 28 animals should be sampled in each farm, totaling 8764 samples.

Species and categories to be sampled: 28 bovines from each farm, namely:

- 17 of Category 1 (6 to 12 months old)

- 11 of Category 2 (12 to 24 months old)

Note : For 2006 sampling plan, samples were also taken from 10 (ten) sheep/goat, from 12 to 24 months old, from the selected farm or an adjoining farm (when such species is not present in the selected farm).

6.2. Fattening zone:

This zone is formed by northwestern districts of Buenos Aires, northeastern districts of La Pampa and southern districts of Córdoba, Santa Fe and Entre Ríos.

Districts involved are detailed below:

a) Buenos Aires province: C. Casares, C. Tejedor, Colón, Daireaux, Gral. Arenales, Gral. Pinto, Gral. Villegas, Guaminí, H. Irigoyen, L.N. Alem, Lincoln, Pehuajó, C. Pellegrini, Rivadavia, Salliquelló, T. Lauquen, Tres Lomas and Ameghino. b) Santa Fe province: Caseros, Constitución, Gral. López, Rosario y San Lorenzo. c) Córdoba province: Gral. Roca, R.S. Peña and Rio Cuarto. d) La Pampa province: Capital, Catriló, Conhelo, Chapaleufú, Maracó, Q. Quemú, Rancul, Realicó and Trenel. e) Entre Rios province: Gualeguay, Gualeguaychú, Islas del Ibicuy and Victoria.

Assumptions for detection of viral circulation within this zone, for 2005 , are given below:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 20%

- Confidence level 95%7 Estimation of prevalence within the farm was higher than in other regions (20%) due to production characteristics of this zone, which presents a high contact rate among young animals. On the basis of these assumptions, 313 farms should be selected and 14 animals from each farm should be sampled (4.382 samples).

Species and categories to be sampled: 14 bovines from each farm, namely:

- 9 of Category 1 (6 to 12 months old)

- 5 of Category 2 (12 to 24 months old)

Assumptions for detection of viral circulation within this zone, for 2006 , are given below:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 15%

- Confidence level 95%

Estimation of prevalence within the farm was higher than in other regions (15%) due to production characteristics of this zone (high contact rate plus predominance of young animals). On the basis of these assumptions, 313 farms should be selected and 19 animals from each farm sampled (5.947 samples).

Species and categories to be sampled: 19 bovines from each farm, namely:

- 12 of Category 1 (6 to 12 months old)

- 7 of Category 2 (12 to 24 months old)

Note : For 2006 sampling plan, samples were also taken from 10 (ten) sheep/goat, from 12 to 24 months old, from the selected farm or an adjoining farm (when no sheep/goat was present in the selected farm).

6.3. Border zone:

This zone is formed by districts of Jujuy, Salta, Formosa, Chaco, Corrientes and Misiones provinces located next to the border with Bolivia and Paraguay. It includes the 25-km strip of land comprised in the Subproject Northern “A” Border. Sampling conducted in this zone is part of additional surveillance actions implemented in risk border areas. Assumptions for detection of viral circulation within this zone are given below:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 10%

- Confidence level 95%

On the basis of these assumptions, 313 farms should be selected and 28 animals should be sampled (8.764 samples).

Species and categories to be sampled:8 28 bovines from each farm, namely:

- 17 of Category 1 (6 to 12 months old)

- 11 of Category 2 (12 to 24 months old) Note : For 2006 sampling plan, samples were also taken from 10 (ten) sheep/goat, from 12 to 24 months old, from the selected farm or an adjoining farm (when no sheep was present in the selected farm), provided they were never vaccinated since in the zone comprised in Subproject Northern A Border sheep/goats are also vaccinated systematically.

6.4. Northern “A” Patagonia:

This zone is formed by the area of Río Negro province where vaccination against FMD is practiced (north to Río Negro river) and the district of Patagones, in Buenos Aires province (according to FMD Eradication Plan 2001).

Assumptions for detection of viral circulation within this zone are given below:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 15%

- Confidence level 95%

Due to a relatively smaller size of this zone, as compared to the rest of the zones, the layout could be adjusted to the number of farms conforming the zone (3.500). On the basis of these assumptions, 300 farms should be selected and 19 animals should be sampled (totaling 5.700 samples).

Species and categories to be sampled: 19 bovines from each farm, namely:

- 12 of Category 1 (6 to 12 months old)

- 7 of Category 2 (12 to 24 months old)

Note : For 2006 sampling plan, samples were also taken from 10 sheep/goat, from 12 to 24 months old, from the selected farm or an adjoining farm (when no sheep/goat was present in the selected farm).

6.5. Northern “B” Patagonia:

For 2005

This zone corresponds with Northern “B” Patagonia region, laid down in the FMD Eradication Plan 2001. It comprises the areas of Río Negro and Neuquén provinces where vaccination against FMD is not practiced.

Samples were taken from bovines and sheep/goats.

Assumptions for detection of viral circulation are the following:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 10%

- Confidence level 95%9 On the basis of these assumptions, 313 farms should be selected and 28 samples taken from each farm (totaling 8764 samples).

Species and categories to be sampled:

 In farms with bovines and sheep/goats, samples should be taken from:

- bovines : 11 animals from Category 1 (6 to 12 months old) 7 animals from Category 2 (12 to 24 months old)

- sheep/goats : 10 animals of whichever category and age

.

 In farms with bovines only, samples should be taken from:

- 17 animals from Category 1 (6 to 12 months old) - 11 animals from Category 2 (12 to 24 months old)

 In selected farms with sheep/goats only, samples should be taken from 28 animals of whichever category and age

.

6.6. Southern Patagonia:

For 2005

This zone corresponds with Southern Patagonia region, laid down in the FMD Eradication Plan. It comprises the provinces of Chubut, Santa Cruz and Tierra del Fuego, Antártida e Islas de Atlántico Sur. Only sheep are sampled in this zone. Assumptions for detection of viral activity are the following:

- Prevalence of infected farms: 1%

- Prevalence within the farm: 10%

- Confidence level 95%

On the basis of these assumptions, 313 farms were selected and 28 samples taken from each farm. (Totaling 8764 samples).

Species and categories to be sampled: 28 sheep of whichever category and age from each farm

. 6.7 Northern B and Southern Patagonia

For 2006

Both zones were gathered taking the same assumptions, species and categories given for Northern B Patagonia in the 2005-sampling plan.

The table below summarizes assumptions used in each zone and number of farms and animals to be sampled according to the layout.10 Table N°1a: Number of farms and animals to be sampled per zone, 2005.

Samples
ZONE Farm prev. Prev. within

farm N° farms to be sampled Per farm Total Zone Species

Central-Mesop. and NOA-Cuyo 1% 10 % 313 28 8764 Bovine

Fattening 1% 20 % 313 14 4382 Bovine

Border 1% 10 % 313 28 8764 Bovine
Northern A Patag. 1% 15 % 300 19 5700 Bovine

Northern B Patag. 1% 10 % 313 28 8764 Bovine and sheep/goat Southern Patagonia 1% 10 % 313 28 8764 Sheep/ goat
TOTAL 1865 45.138

Table N°1b: Number of farms and animals to be sampled per zone, 2006.

Cattle samples Sheep samples

ZONE Prev. Farms Prev. within

farm N farms
Per farm Total

zone Per farm Total

zone

CentralMesopotamia and NOA-Cuyo 1% 10 % 313 28 8764 10 3130

Fattening 1% 15 % 313 19 5947 10 3130

Border 1% 10 % 313 28 8764 10 3130

Northern A Patagonia 1% 15 % 300 19 5700 10 3130

Northern B and Southern Patagonia 1% 10 % 313 18* 5634 10* 3130

TOTAL 1.552 34.809 15.650
* Variable according to animal stock of selected farm11 7. Diagnostic tests:

7.1. Detection of viral circulation: Bovines: ELISA 3ABC-EITB (PANAFTOSA, PHO-WHO kit) diagnostic system was used to detect Ab against FMDV non-capsidal proteins, in areas subjected to systematic vaccination, and ELISA fl (CEVAN-CONICET kit) for detecting Ab against structural proteins against virus types A2001 and O 1 Campos in areas without vaccination (Northern B Patagonia). Sheep/goats: in these non-vaccinated species measurement of Ab against FMDV structural proteins was conducted applying lp ELISA for virus types A 2001 and O1 Campo.

7.2. Estimation of immunity level: In 2005, Elisa Lp was used to measure Ab against FMDV structural proteins for virus types A 2001 and O1 Campo; strain C3 Indaial being added in 2006 (CEVAN-CONICET Kit).

8. Farms sampled

Farms sampled were chosen at random by a random drawing conducted at central level (Epidemiology Directorate). Sampling framework was given by Health Management System (SGS) database containing updated information on all farms registered in the RENSPA.

9. Sampling schedule

In zones where vaccination against FMD is practiced sampling was conducted along with the first vaccination round. In zones where such vaccination is not carried out, animals were sampled from February to May.

10. Additional sampling:

According to OIE Guidelines for the surveillance of foot and mouth disease (Annex 3.8.7 of the Code) subsequent investigations and additional sampling were conducted in all farms where at least one bovine serum was reactive to ELISA 3ABC/EITB or lp ELISA in sheep/goat during the first sampling.

Said investigation included the following:

10.1 Another visit to the farm, epidemiological questioning to its owner or person responsible of animals thereat, survey on last year’s movements of susceptible animals and clinical inspection of all animals in the farm. 10.2 Additional sampling. New blood samples were taken after clinical inspection of the following animal groups: 10.2.1 Animals bled in the first sampling (initial sampling), after at least 30 days of first sampling had passed. 10.2.2 “Contact” lot. 60 bovines from 6 to 12 months old belonging to a lot that was in “contact” with the group of animals initially sampled, whether from the same premises or adjoining premises.12 10.2.3 Non-vaccinated FMD susceptible animals. Up to 60 sheep or goats from the reactive holding or an adjoining holding.

10.3 Probang: two esophageal-pharyngeal liquid samples for Probang testing were taken from reactive animal(s), at a minimum interval of 21 days in between.

11. Estimation of population immunity

Population immunity was assessed using the same samples taken to estimate viral circulation, by taking a random sub-sample. Assumptions to determine the size of this sub-sample were based on estimations for expected immunity level of category 1 animals (with lower number of vaccinations applied):

- Expected proportion of animals covered: 65%

- Acceptable Error: 10%

- Confidence level: 95%

On the basis of these assumptions, 120 farms were randomly chosen from Central Mesopotamia and NOA/Cuyo zone, which were no reactive to ELISA 3ABC/EITB system, and 100 farms from the remaining zones. Out of each farm, 13 cattle samples were chosen at random from the following categories:

- 10 from category 1 (6 to 12 months old)

- 3 from category 2 (12 to 24 months old)

12. Results

12.1 Results of viral circulation for 2005

Results of initial sampling conducted in areas where vaccination is practiced are shown in Table 2 below.

Table 2: Results of initial sampling of cattle to detect viral circulation in zones where vaccination is practiced, per zone and category.

Category 1 Category 2

Reactive

farms Reactive Reactive

Zone Analysed farms n % N

n % N

n %

Central – Mesop/NOA-Cuyo 305 10 3,3% 4936 4 0,08% 3038 9 0,3%

Fattening 290 8 2,8% 2460 1 0,04% 1417 8 0,6%

Border 301 9 3,0% 4633 5 0,11% 2966 11 0,4%

Northern A Patagonia 311 6 1,9% 3673 8 0,22% 2123 2 0,1%

TOTAL 1207 33 2,7% 15702 18 0,11% 9544 30 0,3%13 Map 2: Distribution of (cattle) farms sampled per zone for 200514 Results for viral circulation according to initial sampling conducted in zones without vaccination (Northern B and South Patagonia) are detailed in Table 3 below.
Table 3: Results of initial sampling 2005 in zones without vaccination.

Farms Bovine serum Sheep/ goat serum Zone Analysed Reactive Analysed Reactive Analysed Reactive Northern B Patag. 318 0 2231 0 6324 0

Southern

Patag. 317 0 0 0 9044 0

TOTAL 635 0 2231 0 15368 0

Follow-up of reactive farms:

Farms where at least one animal reacted to ELISA 3ABC/EITB system in the initial sampling (33) were subjected to further investigation, pursuant to Annex 3.8.7 of the Code, Guidelines for FMD Surveillance.

A detail of farms investigated and samples taken during additional sampling is given in the following table. In some cases, sampling was also conducted in premises next to the reactive farm. Therefore, total farm number (38) is higher than reacting farms (33).

Table 4: investigated farms, samples taken and results of additional sampling.

Zone No reactive farms No sampled farms Bovine samples

taken Reactive bovine samples Sheep/goat samples

taken Reactive sheep/goat

samples Central – Mesop. / NOA-Cuyo 10 12 528 3 207 0

Fattening 8 8 339 0 73 0

Border 9 10 560 0 60 0 Northern A Patagonia 6 8 344 1 69 0

Total 33 38 1771 4* 409 0

*Each one from different premises.15 Map 3: distribution of farms presenting reactive sera in first sampling 200516 All farms were visited and animals therein inspected. Additional serum samples were taken in 32 out of 33 reactive farms to rule out or confirm initial sampling results. Re-sampling could not be carried out in one farm due to depopulation of the farm at the time of the visit. EPL samples were taken for Probang testing, from which no virus was recovered. Out of animals that reacted in the initial sampling, only one (1) remained reactive. Sero-conversion was not detected in any case. No evidence of epidemiological risk was found after activities previously mentioned (clinical inspection, movement survey, epidemiological questioning, etc.) were carried out in such premises.

12.2 Results of viral circulation for 2006

12.2.1 Initial sampling

Results of initial sampling in cattle are given in Table 5 below.

Table 5. 2006 results of initial sampling in cattle to detect viral circulation/infection, per zone and category.

Category 1 Category 2

Reactive farm Reactive Reactive Zone Analysed farm n % N

n % N

n %

Central –Mesop/NOACuyo 284 3 1,06% 4431 2 0,05% 2977 3 0,10%

Fattening 286 4 1,40% 3306 1 0,03% 1967 3 0,15%

Border 271 1 0,37% 4172 0 0,00% 2709 1 0,04%

Northern A Patagonia 303 0 0,00% 3459 0 0,00% 2091 0 0,00%

Northern B and Soutnern Patagonia 74 0 0,00% 832 0 0,00% 669 0 0,00%

TOTAL 1218 8 0,68% 16200 3 0,02% 10413 7 0,07%17 Table 6 below provides results of viral circulation/infection in sheep (non-vaccinated species) per zone.

Table 6. results of initial sampling in sheep to detect viral activity, per zone

Predios reactivos Reactivos

Zone Predios con ovinos analizados n % Muestras analizadas n %

Central – Mesop/NOA-Cuyo 199 0 0 1952 0 0

Fattening 162 0 0 1562 0 0

Border 56 0 0 494 0 0

Northern A Patagonia 122 0 0 1186 0 0

Northern B and Soutnern Patagonia 295 0 0 7408 0 0

TOTAL 834 0 0 12602 0 0

Comments : As shown in Table 5, out of a total of 1218 (0.65%) premises where cattle was sampled only 8 premises had, at least, one reactive animal. Distribution ofsuch premises among zones is not even, predominating in CentralMesopotamia/NOA-Cuyo (3 premises) and Fattening (4 premises) zone. However, the number is low and no clusters were observed. All sheep samples were no reactive.

12.2.2 Follow-up of positive cases

Additional investigations were conducted at the 8 premises where at least one reactive animal was found, which included:

12.2.2.1 Epidemiological surveys

After assessment of these surveys, no risk situations were detected from which it could be inferred disease occurrence in premises under investigation.

12.2.2.2 Clinical inspection

No evidence of FMD or FMD-compatible disease was found.

12.2.2.3 Additional sampling

Additional sampling was conducted in all premises involved. Animals from adjoining premises were included in cases where they were in-contacts of the reactive lot. Table 7 below provides detailed information on samples taken for the additional sampling and results obtained.18 Table 7: Detailed additional sampling. Samples taken Reactive samples
Premises Cattle Sheep/goat Cattle Sheep/goat

1 60 0 0 0 2 66 0 0 0 3 58 34 1 0 4 50 25 0 0 5 60 0 0 0 6 75 45 1 0 7 73 46 1 0 8 88 27 0 0

EFL-Probang samples were taken from 7 (out of 10) reactive animals in the initial sampling, no virus being isolated. The other 3 reactive animals were not available at the time the farm was visited. As shown in the table, only 3 cattle sera were reactive. Only one mantained the same result as in the initial sampling.

12.3 Analysis of sampling results for viral circulation/infection

- Samplings were conducted as established in the layout

- Due to space distribution of farms with reactive animals, particular studies for clusters were not required.

- Proportion of farms having at least one reactive animal, between zones, was homogeneous.

- Upon follow-up of premises with reactive animals, no evidence of viral circulation was found.

- No sample was reactive within the zone where vaccination is not practiced (Southern and Northern B Patagonia), confirming the “FMD-free without vaccination” condition.

Conclusion: results obtained in this study provide reliable evidence supporting lack of viral circulation/infection in zones under study.

12.4 Population immunity

12.4.1 Interpretation of results

According to LP ELISA titre obtained for each serum, immunity level was classified into the following categories: Low, Medium or High, on the basis of percentage protection expectancy (PPE) for each titre and serotype under study. PPE was calculated by correlating lp ELISA titres with Podal Generalization Protection (PGP). Ranges for each category are given in the table below.19 Table 8: Interpretation of liquid phase (lp) ELISA results according to PPE. Lp ELISA. titre O1Campos A2001 PPE RESULT

< 1.77 < 2.1 < 75% Low 1.77 – 1.91 2.1 – 2.3 75% a 85% Medium > 1.91 > 2.3 > 85% High

Animals with PPE equal or over 75% had suitable protection levels against natural exposure to FMDV. Therefore, and for better understanding the results, categories Medium and High were grouped as Medium-High.

Population immunity was assessed with sera obtained at the time prior to revaccination, being the basal protection level of the cattle herd (i.e. worst immunity condition).

Only population immunity results for 2005 are given since at the time this report was prepared, data for 2006 was not yet available. NCP tests concluded recently.

Results:

The following graphs provide detailed results for population immunity obtained in 2005 sampling plan. Results are expressed as percentage of sera with Medium-High immunity level for each category, zone and virus type.

Inmunidad Poblacional 2005.

Categoría 2 Virus A 2001

0,00% 20,00% 40,00% 60,00% 80,00% 100,00%

CM/NC Engorde Frontera PatagNor teA Inm unidad Poblacional 2005. Cate goría 2 Virus O1

0,00% 20,00% 40,00% 60,00% 80,00% 100,00%

CM/ NC Engorde Frontera PatagNor teA20 Inm unidad Poblacional 2005.

Categoría 1 Virus A2001

0,00% 20,00% 40,00% 60,00% 80,00% 100,00%

CM/ NC Engor de Fr onter a PatagNor teA Inm unidad Poblacional 2005. Categoría 1 Virus O1

0,00% 20,00% 40,00% 60,00% 80,00% 100,00%

CM/ NC Engor de Fr ont er a PatagNor teA

Percentage of sera with medium-high PPE is satisfactory in all zones. Lowest values were found in border zone, in category 1 for virus type A 2001. Such titres reflect the maximum drop in the immunity curve of previous vaccination and are prior to immediate revaccination.

To compare data from previous samplings, graphs show results of the last three annual samplings (2003 to 2005) together. Please note that for sampling 2005, Central/Mesopotamia and NOA / Cuyo zones were unified. The bar for 2003 and 2004 belong to Central / Mesopotamia zone, since most sera taken during 2005 originated in that zone.21 Graphs of compared population immunity for 2003, 2004 and 2005 per zone, category and virus
type.

By comparing results for 2003-2004 and 2005, a progressive increase of the proportion of animals with medium-high PPE is observed in category 1, which could reflect improvements in vaccination strategies.

Conclusions: Population immunity levels are satisfactory and compatible with good vaccinal coverage, enough to prevent FMDV circulation and transmission. Inm unidad Poblacional Comparada 2003, 2004 y 2005. Categoría 2 Virus O1

0,00% 10,00% 20,00% 30,00% 40,00% 50,00% 60,00% 70,00% 80,00% 90,00% 100,00%

2003

2004

2005 Inm unidad Poblacional Comparada 2003, 2004 y 2005. Categoría 1 Virus A2001

0,00% 10,00% 20,00% 30,00% 40,00% 50,00% 60,00% 70,00% 80,00% 90,00% 100,00%

Cent ral – Mesop Engor de Fr onter a Pat agNor teA 2003

2004

2005 Inm unidad Poblacional Comparada 2003, 2004 y 2005. Categoría 1 Virus O1

0,00% 10,00% 20,00% 30,00% 40,00% 50,00% 60,00% 70,00% 80,00% 90,00% 100,00%

2003

2004

2005

Inm unidad Poblacional Comparada 2003, 2004 y 2005. Categoría 2 Virus A
2001

0,00% 10,00% 20,00% 30,00% 40,00% 50,00% 60,00% 70,00% 80,00% 90,00% 100,00%

2003

2004

2005