Discussion and Conclusions The incidence and prevalence of UBT in cows and in farms steadily increased during the analyzed period. The percentage of cows affected by UBT ranged from 2,5 to 17,5% in the counties, with more frequent values between 5 and 10%. However, the percentage of herds affected by UBT ranged from 15 to 95% in the analyzed counties. There was a progressive gradient from the counties with less cases to those with more cases. The maps regarding the prevalence of UBT in dairy cows and in farms in SMI showed a similar pattern. Stronger correlations with UBT occurrence were found when the land was rented than when the land was owned by the farmer. Permanent pastures also showed higher correlations with UBT occurrence than temporary pastures and forage crops. The number of cattle and the number of farms per county are correlated with prevalence of UBT. No correlations were found between animal density and the number of land units on one hand, and the occurrence of UBT on the other. The counties ranking according to the incidence and prevalence of UBT, might help to direct control actions to the more affected counties, in order to reduce the heavy financial burden associated to the relatively high occurrence o UBT in SMI. P. aquilinum has a wide distribution in São Miguel Island. Introduction Bracken Pteridium aquilinum (L.) Kuhn is very common in the Azores Islands, specially in marginal habitats, but also in pastures. Its presence has been associated with the common occurrence of Bovine Enzootic Haematuria in São Miguel Island (Pinto et al. 2004), and in other Islands of the Archipelago. The aim of this study was to characterize the bovine enzootic haematuria (BEH) in the counties of São Miguel Island (SMI) from the epidemiologic point of view. It was tested the hypothesis of correlation between several descriptors of the land and dairy herd structures and the occurrence of urinary bladder tumours (UBT). A characterization regarding the occurrence of UBT in cattle in SMI, using incidence and prevalence indicators and to mapping in GIS. To assess the economic impact of BEH. Methods Data Sources: Meat Inspection Service of São Miguel abattoir, SIARA, SNIRB, SIBOV and POSEIMA data base systems from Serviço de Desenvolvimento Agrário de São Miguel Island and General Agriculture Census 1999 (INE). These data bases were used to obtain the following data: Distribution of UBT cases by counties; Used agricultural land surface (ha) – total, rented or owned by the farmer, and land area per farm (ha/farm); Number of land units per farm; Temporary pastures and forage crops (ha); Permanent pastures (ha). Cattle farms, animals, dairy farms, dairy cows numbers per county. Occurrence of UBT in dairy cattle in São Miguel Island - Evaluation of the annual incidence of UBT from bovine carcasses rejected at the São Miguel abattoir (MSM), from 1994 to 2002; - Evaluation of the annual prevalence of UBT in dairy farms, from 1994 to 2002; -UBT prevalence data mapping, using ArcView 3.2 (ESRI, 1992). Correlation between several descriptors of land and dairy farm structure and the occurrence of UBT in SMI Counties, from 1994 to 2002 Evaluation of the economic impact of BEH Funds spent from 2000 until October 2005, considering: - The insurance regulations to compensate the farmers; and the data regarding carcass rejection caused by UBT; - The compensatory funds expended from 1998 to 2004, supported by the Azorean Regional Government, attributed to farmers affected by UBT. Statistical Analysis Frequency distributions of cows and farms affected by UBT per county; Evaluation of the correlation between the average percentage of tumour occurrence in animals and in farms; Correlation between the total number of farms affected by UBT, the mean annual number of farms affected by UBT, the total number of affected cows, the average annual number of affected cows, and the different descriptors of farm structure and land use, with SPSS 11. (Statistical Analysis for Social Sciences). Bovine enzootic haematuria in São Miguel Island (Azores): analysis by county and correlation with land and herd traits Leitão 1, M., Pinto 1, C., N. & Silva 2, L. 1 Divisão de Sanidade Animal e Higiene Pública Veterinária, Serviço de Desenvolvimento Agrário de São Miguel, Ponta Delgada, Portugal; 2 Departamento de Biologia, Universidade dos Açores, Ponta Delgada, Portugal Aknowledgements This work is part of a project supported by FCT, POCTI AGG/48737/2002. We thank Xènia Illas for the edition of the maps. References Pinto, C.A.; Januário, T.; Geraldes, M.; Machado, J.; Lauren, D.R.; Smith, B.L. and Robinson R.C. (2004). Bovine Enzootic Haematuria on São Miguel Island - Azores. In: T. Acamovic, C.S Stewart, and T.W. Pennycott (eds.). Poisonous Plants and Related Toxins. CAB International, Wallingford. Dairy cow in direct contact with bracken fern Results Annual incidence of UBT in dairy cows slaughtered at MSM. Annual ocurrence of UBT in herds from São Miguel Frequency distribution of dairy cows affected by UBT in 54 counties from São Miguel. Average annual prevalence of UBT in dairy cows breed at 54 counties in São Miguel. Average annual prevalence of UBT in dairy farms at 54 counties in São Miguel. Map of São Miguel counties showing the mean annual prevalence of UBT (percentage intervals) in dairy farms. Map of São Miguel counties showing the mean annual prevalence of UBT (percentage intervals) in dairy cows. Correlations between UBT occurrence and several descriptors regarding land and farm structure. Based on data from 54 counties from São Miguel Island. r, Pearson correlation; p, probability. Significant correlations are shown in bold (60,0) (55,0) (46,9) (40,8) (28,3) (21,0) (15,3) (6,2) (7,4) (9,1) TB no MSM (nº) Explorações com TB (nº) e (%) Explorações (nº) Vacas leiteiras (nº) Ano (60,0) (55,0) (46,9) (40,8) (28,3) (21,0) (15,3) (6,2) (7,4) (9,1) UBT at MSM (nº) Herds with UBT (nº) and (%) Herds (nº) Dairy Cows (nº) Year Frequency distribution of dairy farms affected by UBT in 54 counties from São Miguel.