**D NSA** 
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  1 

### FMD Epidemiological surveillance: **Serological s ampling**  **2011**
**Introduction :**  The Directorate for Epidemiology, dependent of the National Directorate of Animal Health of SENASA, designs these studies which are prepared and advised by the Integrated Epidemiology Advisory Committee, made up by a group of epidemiologists of the O fficial S ervice and other agencies (INTA, CONICET and faculties of veterinary Schools). The regulatory framework to carry out this study responds to the current international regulation on FMD in accordance with the Terrestrial Animal Health Code of the World Organization for Animal Health (OIE), SENASA carries out surveillance in conformity with articles 8.8.40 to 8.5.46; with the objective to demonstrate absence of disease, both in f ree zones with vaccination, as well as where vaccination is not practised. In the zone with vaccination absence of virus circulation is demonstrated and immunity given by the vaccine at a cattle population is estimated. As to operational sample collection and delivery, these are in charge of the regional local veterinarians of SENASA, while the diagnosis is carried out in the Animal Laboratory of the Directorate for Laboratories and Technical Control (DILAB

-SENASA). **Objetives :**  a) To detect virus circulation or infection by the foot

-and

-mouth disease virus (FAV ) in the national territory. b) To estimate the population immunity level for foot

-and

-mouth disease in the cattle population in the area with vaccination. **Variables to measure :**  a) Infection or virus activity indicators: presence of antibodies against non- structural proteins (NSP) in cattle and against structural proteins (SP) in species other than cattle. b) Immunity level in the vaccinated population: in cattle that previously were negative to the NSP tests, the values of antibodies against SP for types of virus present in the vaccine are determined**D NSA** 
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  2 **Sampling framework :**  This study is carried out throughout the country, although due to the geographical diversity, climates and production systems, the territory is divided into zones in regard to vaccination implementation. It is for this reason that the vaccination zone is subdivided into sub

-zones (1, 2 and 3). Based on this zoning for zones 1 and 2 according to the bovine density, majorit

y in the first one, while in the second one extensive production systems predominate. Zone 3, according to the regionalization of the FMD Eradication Plan , corresponds to Patagonia North A; created with the objective of protecting the rest of the Patagonia (Patagonia North B and Patagonia South ) that is separated from the rest of the country and is treated as a special zone without vaccination. Figure 1 shows the map with the different sub

-zones .

**Figure 1**  **: Map with the zonin g of Argentina.** 

**Sample size :**  The objective of this sampling consists in the detection of an event in each of the zones and was carried out in two stages. The considered assumptions are represented in table 1. References : 1. EAST ZONE 2. WEST ZON E 3. PATAGONIA NORT H A ZON E 4. PATAGONIA NORTH B ZONE AND PATAGONIA S OUTH 

## 2 **1 3**  **4 D** **NSA**
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  3 **Table 1. Assumptions considered i n this**  **sampling** Prevalence of infected herds 1% Prevalence of infected animals 10% Confidence 95% From these assumptions **350 livestock farms** were selected in each zone, where 28 animals were sampled in each establishment. **Species and categories of s ampled animals**  **:** The sampled species were cattle, sheep and goats. All of different categories or ages, according to each zone:

 Zones **with** vaccination (1, 2 and 3): o Cattle: 28 animals by each establishment :  **17** animals of **category 1** (6 to 12 months of age).  **11** animals of **categor**

**y 2**  (12 to 24 months of age). o Sheep /goats if any, in each establishment:  **10** animals 6 to 24 months of age . This is because the production areas of these species coincide with marginal zones or of low receptivity, making distribution of these populations very irregular.

 Zone **without** vaccination (zone 4): **28** animals of any of the susceptible species (bovine, ovine or caprine animals) according to the stocks of the selected farm. Measure adopted due to the non-vaccination condition, added to the geographical and climatic diversity. **Diagnostic tests :**  All of the samples are processed at the SENASA central laboratory ( Directorate for Laboratories and Technical Control, Martínez, Buenos Aires province), which is the FMD reference laboratory of the World Organization for Animal Health (OIE). Cattle :

 ELISA 3 ABC

-EITB (KIT NCPanaftosa) for the detection of antibodies against non- structural proteins (NSP) of foot

-and

-mouth disease virus (FMDV) as infection indicator.**D NSA** 
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  4  ELISA fl for the detection of antibodies against structural proteins (SP) of types O1 Campos, A2001 and C3 Indaial of FMDV, to estimate immunity in vaccinated populations. Sheep/goat:s:  ELISA fl for the detection of antibodies against structural proteins (SP) of types O1 Campos, A2001 and C3 Indaial of FMDV, to estimate immunity in vaccinated populations. In regard to samples of esophageal

-pharyngeal fluid (LEF) collected in reactor animals at initial sampling, these are processed by Complement Fixation Test at 50% in each of the two passages in BHK cell culture s . Results of vir

us activity

in the vaccination zone: Table 2 and 3 show the number of bovine animals sampled in the zone with vaccination and the results obtained by categories are listed in the table 2 and 3. It is considered as reactor animal those whose sera were reactors to 3ABC and EITB ELISA tests. Table 4 and 5 show the number of establishments sampled and the results obtained from sheep/goats. **Table 2: Number of sampled cattle in the zones with vacc ination (zones 1, 2 and 3).**  **Zone No. of farms**  **No. of cattle** 1 350 9537 2 315 8065 3 332 7819 **Total 997**  **25421**

**Table 3: Results to the**  **ELISA 3ABC -** **EITB tests in cattle of the zone with vaccination, by category.**  **Animals in category 1 Animals in ca** **tegory 2 Zon** **e sampled**  **Reactors sampled**  **Reactors N** **o. %**  **N o.**  **%** 1 5794 0 0 3743 0 0 2 4771 1 0,02 3294 4 0,12 3 4795 0 0 3024 1 0,03 **Total 15360**  **1 0,01**  **10061 5**  **0,05 D** **NSA**
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  5 **Table 4. Results to the ELISA fl tests for the virus types A2001, O1 Campos and C3 Indaial** 

**in sheep/goats of the zone with vaccination. Zone**  **No. farms No. sheep and/or goats**  1 216 2111 2 180 1719 3 168 1928 **Total 564**  **5758 Table 5. Farms and samples collected of sheep/goats.**  **Zone No sheep and/or goats**  **No. of reactors** 1 2111 0 2 1719 0 3 1928 0 **Total 5758**  **0** In regard to the number of sampled farms, there were some zones where sample collection could not be concluded as requested. This was due to severe weather problems (drought) that affected large areas of the country, making it impossible to keep the animals in corrals due to extreme weakness. However, the validity of the study was not affected given that a larger number of samples than those requested in the design. Figure 2 shows the map with the geographical distribution of the sampled cattle farms.

**Figure 2. Geographic al**  **distribution of the sampled cattle farms. D** **NSA**
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  6 Figure 3 shows a map with the distribution of sampled farms with sheep/goats in the zone with vaccination (zones 1, 2 and 3).

**Figure 3. Geographic al**  **distribution of the sheep/goats sampled farms**

Figure 4 shows the geographical location of the farms that resulted with at least one bovine reactor to the serological tests carried out. Figure 4. Geographical distribution of the farms with bovine reactors to ELISA 3 ABC
EITB tests .**D NSA** 
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  7 **Supplementary Studies:** When there was an animal positive to the confirmatory tests, the official laboratory informed the fact to the Epidemiology Directorate for the result and, according to the OIE Terrestrial Code, in that farm where the animal was found, a follow

-up study was carried out. For this purpose, the official veterinarian of the jurisdiction corresponding to the mentioned farm, where the supplementary investigation was carried out was informed, which consisted in visiting the farm and interviewed the owner or the person responsible for the animals, movements of susceptible animals (entries and exits) were studied, additionally a supplementary serological study was carried out, which consisted in:
• Clinical inspection and new serology of the same group of animals of the first sampling. • Clinical inspection and serology of a group of contact animals of the first lot. • Clinical inspection and serology of a group of non-vaccinated susceptible animals (sheep/goats), in case they are available at this farm or at a neighboring farm. • Extraction of esophageal

-pharyngeal fluid (LEF) for PROBANG of the reactor animal. This sample is repeated in 21 days In each of the 6 investigated farms, where there was a single reactor animal, indicated activities were carried out. In total 474 supplementary serum samples were collected and LEF samples were collected in those cases where the reactor animal was located. In none of these investigated farms there was evidence of virus circulation or of disease, both by clinical inspections and surveys, supplementary serology or virological surveillance (LEF). Results in the zone without vaccination : The zone without vaccination (zone 4) is recognized by the OIE as a " FMD Free Zone where Vaccination is not practised " and corresponds to Patagonia South and Patagonia North B. The design applied in this zone included sample collection in bovine, ovine and caprine species. However, due to the predominance of sheep production in all Patagonia, in most of the selected farms only this species was sampled. Table 6 details the number of farms and samples collected, by specie s, as well as the results obtained.**D NSA** 
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  8 **Table 6. Farms and animals sampled and their results in zone 4 (without vaccination)**

**Farms reactors**  **% Animals**  **reactors %**  **Sheep/goats** 326 0 0 8753 0 0 **Cattle** 24 0 0 Category 1 286 0 0 0 0 Category

2 220 0 0 **Total 350**  **0 0**  **9259 0**  **0** Figure 5 shows the geographical distribution of the sampled farms in zone 4 (zone without vaccination) with sheep/goats and cattle. **Figure 5: Geographical distribution of the sampled**  **farms with cattle (blue) and sheep**  **/ goats (green** **) in zone 4. D** **NSA**
**– Dirección de Epidemiología y Análisis de Riesgo**  **- Programa de Fiebre Aftosa**  9 **Conclusions:** Through these activities of active surveillance, no evidence of virus circulation or of infection of FMD virus was found, by clinical inspections and surveys, supplementary serology or virological surveillance (LEF), both in the zone with vaccination as in those in where vaccination is not practised. In addition to these results, it is also taken into account other activities of epidemiological surveillance that are carried out across the country for the purpose of demonstrating the health situation in both zones in regard to FMD.
o Ante

- and post-mortem inspection at the time of slaughter (approximately 12 million cattle, 3 million pigs and 1 million sheep annually in establishment with SENASA inspection). o Inspections at the time of FMD vaccination by trained personnel, two times per year in all the bovine population of the zone with vaccination. o Inspecciones oficiales en diversos controles efectuados por personal de campo de SENASA o veterinar

ios acreditados: o Official inspections in various control posts carried out by SENASA field staff or accredited veterinar

ians : o Herds to slaughter for export. o Auctions, fairs and exhibitions o Inspections for transfer to zones of different status in regard to tick. o Inspections by other health programs (sheep scab program in Patagonia, for example). o Inspections for movement of animals in protected areas (exit of animals in High Surveillance Zone; entry of susceptible animals to Patagonia North ).