Spatial distribution and risk factors of brucellosis in Iberian wild ungulates

Background: The role of wildlife as a brucellosis reservoir for humans and domestic livestock remains to be properly established. The aim of this work was to determine the aetiology, apparent prevalence, spatial distribution and risk factors for brucellosis transmission in several Iberian wild ungulates. Methods: A multi-species indirect immunosorbent assay (iELISA) using Brucella S-LPS antigen was developed. In several regions having brucellosis in livestock, individual serum samples were taken between 1999 and 2009 from 2, 579 wild bovids, 6, 448 wild cervids and4, 454 Eurasian wild boar (Sus scrofa), and tested to assess brucellosis apparent prevalence. Strains isolated from wild boar were characterized to identify the presence of markers shared with the strains isolated from domestic pigs. Results: Mean apparent prevalence below 0.5% was identified in chamois (Rupicapra pyrenaica), Iberian wild goat (Capra pyrenaica), and red deer (Cervus elaphus). Roe deer (Capreolus capreolus), fallow deer (Dama dama), mouflon (Ovis aries) and Barbary sheep (Ammotragus lervia) tested were seronegative. Only one red deer and one Iberian wild goat resulted positive in culture, isolating B. abortus biovar 1 and B. melitensis biovar 1, respectively. Apparent prevalence in wild boar ranged from 25% to 46% in the different regions studied, with the highest figures detected in South-Central Spain. The probability of wild boar being positive in the iELISA was also affected by age, age-by-sex interaction, sampling month, and the density of outdoor domestic pigs. A total of 104 bacterial isolates were obtained from wild boar, being all identified as B. suis biovar 2. DNA polymorphisms were similar to those found in domestic pigs. Conclusions: In conclusion, brucellosis in wild boar is widespread in the Iberian Peninsula, thus representing an important threat for domestic pigs. By contrast, wild ruminants were not identified as a significant brucellosis reservoir for livestock.

This is a contribution to the MCINN Plan Nacional research grant AGL2005-07401 on shared diseases and FEDER. The study benefited from agreements of IREC with MARM-OAPN, Castilla - La Mancha and Principado de Asturias. Additional support to the IREC is acknowledged to FISCAM (GC05-006 and PI-2007/56). CITA and UNIZAR also acknowledge support from INIA (FAU2008-00015). The Aragon Government has financed part of this work under the programme “Health status surveillance on game wildlife in Aragon”. NEIKER thanks the funding of the Department for Environment, Spatial Planning, Agriculture and Fisheries of the Basque Government and the collaboration of ACCA and Regional Governments. Grant and postdoctoral contract acknowledgements: P.M Muñoz (CITA Technologist grant and Juan de la Cierva research contract), M. Boadella (PhD grant TB-STEP, FP7). P. Acevedo (Juan de la Cierva research contract, MICINN and FEDER, project CGL2006-09567/BO). F. Ruiz-Fons (I.S. Carlos III research contract, Spanish Ministry of Health).