Análise espacial da contagem de células somáticas e prevalência de patógenos contagiosos da mastite em rebanhos leiteiros em Minas Gerais, Brasil

Abstract

Mastitis continues to be a major challenge for the milk chain and cause great losses as loss of production, the early disposal of animals, treatment costs and interference in the quality of the milk. The contagious pathogens are causing much of the problem, with this, the contents of subclinical mastitis increases, therefore leading to increased somatic cell count (SCC). The main contagious pathogens are Staphylococcus aureus and Streptococcus agalactiae. The SCC is used throughout the world as an indicator to evaluate and monitor the health of the mammary glands and assists control programs and prevention of mastitis. The knowledge generated from specific epidemiological studies, on the pattern of infection, prevalence of contagious pathogens of mastitis in dairy cattle herds, temporal and spatial distribution of contagious mastitis agents and economic analysis of sanitary and herd-level region can be used in the improvement of control and prevention of mastitis. Spatial epidemiology helps the understanding of the geographical distribution of data occurring in time and space, and allows comprehensively examine the dynamics of disease, indicating forms of the actuations problem region level. The objective of this study was to evaluate the relationship between spatial analysis of somatic cell counts and prevalence of contagious mastitis pathogens between dairy cattle herds. In a population of 112 herds, samples were collected for isolation of S. aureus and S. agalactiae and for SCC. Spatial dependence for SCC was evaluated by means of semivariograms and, when identified spatial dependency, using the Kriging method was created the map of isolines for SCC. Herds with isolation of S. aureus and S. agalactiae had 9.3 times more chances to present values above 400,000 cells/mL. High prevalence was observed (89.0 to 100.0%) and homogeneous distribution among the regions for S. aureus, however homogeneous distribution was not observed for S. agalactiae, whose prevalence ranged from medium to high (16 to 93%) among the regions studied. Moderate spatial dependence (GD = 37.6; r2= 0.31) was observed for SCC between herds. Association between the prevalence of S. agalactiae and SCC was observed in accordance with regions evaluated in accordance with the results of spatial analysis. Herds in the area of SCC have up to 5.5 times more likely to have isolated S. agalactiae of tank milk samples. The spatial analysis of the SCC of herds can be a tool to assist those involved in decision-making at the level of the region as regards the adoption of control measures and prevention of mastitis.