Levins, R.Verwoerd, Daniel Wynand2012-07-132012-07-1320122000Levins, R 2000, 'Models for regional heartwater epidemiology in a variable environment’. Onderstepoort Journal of Veterinary Research, vol. 67, no. 3, pp. 163-165.0330-2465http://hdl.handle.net/2263/19416The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. Adobe Acrobat v.9 was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.A model of the epidemic dynamics of heartwater within a cattle production unit was presented by Yonow et al. (1998). Here, the model is expanded to a region consisting of several farms to study the effect of environmental variability on control strategies. We have shown that: • In a region, where the environment of each farm is modelled with constant epidemiologic parameter values, while the between-farm parameter values differ, regional variation in the removal rate of infected cattle increases the average fraction of infected cattle across the region , while regional variation in the transmission rate of infection from ticks to cattle decreases the average fraction of infected cattle, thereby requiring control measures that keep the removal rate uniform and the transmission rate variable. • In a region, where in addition to regional variation between farms, the epidemiologic parameters of each farm are time-variant, then temporal variation in both the transmission rate and removal rate increases the average fraction of infected cattle across the region, thereby requiring control measures that keep both parameters uniform.© ARC-Onderstepoort (original). © University of Pretoria. Dept of Library Services (digital).Veterinary medicineConcaveConvexHeartwaterTime averagingTime-variantVariable environmentVeterinary medicine -- South AfricaHeartwater -- South AfricaCattle -- DiseasesArticle