Multifactorial correspondence analysis of risk factors for sheep and goat brucellosis seroprevalence

This paper reports the investigation of herd characteristics as potential risk factors for sheep and goat brucellosis seroprevalence, based on multifactorial correspondence analysis. The survey was carried out on 4123 herds in Trás-os-Montes e Alto Douro, in the north-east of Portugal. Brucellosis in small ruminants is a disease with Obligatory Notification status in Portugal and is the subject of an Official Eradication Campaign. Multifactorial correspondence analysis identified an association between herds with high seroprevalence (≥5%), intermediate seroprevalence (>0% and <5%), 3 or more positive animals, 2 positive animals, 1 positive animal, and larger herds (150 or more analyzed animals), and this group supplied contrasting results to the group of no positive animals and small herds. Within this study, larger herds were associated with milk production and intermediate seroprevalence values (of >0% and <5%), and contrast with those herds with 3 or more positive animals and high seroprevalence. The significant contribution made by the principal and secondary axes consolidates this explanation. The results of this study suggest that herd size and production type might have an impact on brucellosis seroprevalence.