Using spatial tools for high impact zoonotic agents’ surveillance design in backyard production systems from central Chile

Abstract

Specific locations of backyard production systems (BPSs) in Chile remain unclear, creating dificulties for designing surveillance activities for promptly detecting zoonotic agents with high impacts on health, such as avian influenza and Salmonella spp. This study aims to prove the use of spatial tools for improving the surveillance of BPSs in central Chile. A stratified and proportional random sampling was performed in 15 provinces of the Valparaiso, Libertador General Bernardo O'Higgins and Metropolitana regions. In this sampling, 329 BPSs were detected. In the first stage, 329 random sample points were allocated within the study area that searched for BPSs with poultry or swine breeding. Then, these random points were validated with remote sensing and in the field by searching for the presence of rural or semi-rural areas, nearby crops and houses or small towns within a 5 km radius around each point, while points allocated over hills or water sources (lakes or rivers) were discarded. Over 70 % of the sampling points were correctly allocated. In Los Andes, Cordillera and Chacabuco, less than 50 % of the points were allocated within feasible sampling areas. From the total BPSs sampled, 89 % met the 5 km radius criteria, and in the provinces of Valparaiso, Cordillera and Cachapoal, over 20 % of the sampling points were outside the radius criteria. This study is the first in Chile to explore the locations and sanitary statuses of BPSs. Given the lack of knowledge about the specific locations of BPSs, their identification during field activities represents a high cost for the surveillance of pathogens. We argue that using spatial tools in BPS surveillance design is an important support for healthcare management.

First detection and characterization ofSalmonellaspp. in poultry and swine raised in backyard production systems in central Chile

“…A proportional stratified random sampling approach was used, based on the 15 provinces included in the study area, using a random allocation of sampling points, as previously described [20]. Equation (1) was used adjusted by equation (2) to estimate the sample size [21]: where n = sample size, Z α = the value of Z α required for confidence level = 1 − α , where α corresponds to the level of confidence; Z α is the percentile of a standard normal distribution (1 − α /2); p = the expected prevalence of the pathogen, q = (1 − p) and L = the precision of the estimation, also known as ‘allowable error’ or ‘margin of error’.…”

“…in BPS located in central Chile, sample size was calculated based on a prevalence of 50%, ensuring maximum sample size possible when using an estimating a proportion approach [21], a confidence level of 95% and a precision of 5%. Pigs reared on BPS were used for sample size calculation, assuming that they would also breed poultry, the number of BPS, by province, were obtained from the last available agricultural census from 2007 [19, 20]. A final sample size of 329 BPS was used (Table 1).…”

Movement Restriction and Increased Surveillance as Efficient Measures to Control the Spread of Highly Pathogenic Avian Influenza in Backyard Productive Systems in Central Chile

“…Therefore, a dataset of 16,289 random geolocations was generated and stratified by province (Figure 1) according to the census information using the Surface Tool in ArcGIS-10 software (Esri, California, USA). This methodology was previously validated in Chile by Alegria-Moran et al (30) indicating that the approach followed a realistic spatial distribution.…”

Detección del virus de la enfermedad de Newcastle en aves de traspatio en Chile

“…Bernardo O'Higgins. The target population included BPS in central Chile that raised poultry and were no larger than 100 birds (13). According to data from the last agricultural and forestry census in 2007 (Instituto Nacional de Estadísticas), the number of BPS that raise birds in this area was 16.289 units.…”

“…El estudio fue llevado a cabo entre 2013 y 2015 en la zona central de Chile, que incluye las regiones de Valparaíso, Metropolitana y Libertador General Bernardo O'Higgins. La población objetivo del presente estudio contempló SPT de la zona central de Chile que criaban aves de corral y cuyo tamaño no superaba las 100 aves (13). Según datos del último censo agropecuario y forestal de 2007 (Instituto Nacional de Estadísticas), el número de SPT que crían aves en esta área era de 16.289 unidades.…”