Bluetongue In Brazil: A Spatiotemporal Analysis (2001- 2023)

Abstract

Background: Bluetongue is a non-contagious viral disease caused by the bluetongue virus (Orbivirus), affecting domestic and wild ruminants, particularly sheep. Transmission occurs primarily through vectors of the genus Culicoides, with distribution influenced by environmental and climatic factors. In Brazil, disease outbreaks are sporadic; however, bluetongue is classified as a notifiable disease due to its economic and epidemiological significance and its potential to be mistaken for foot-and-mouth disease. Materials and Methods: This study analyzed the temporal and spatial distribution of bluetongue outbreaks in Brazil from 2001 to 2023, investigating possible associations with climatic variables such as temperature, precipitation, and wind speed. Data were obtained from the Zoosanitary Information System Panel (MAPA-SIZ) and organized into spreadsheets for statistical analysis. Pearson's correlation test and spatial lag regression were applied using the Jamovi and GeoDa software, respectively. Results: A total of 51 bluetongue virus infection outbreaks were recorded, comprising 482 cases predominantly concentrated in southern Brazil. Sheep were the most affected species (73% of cases), followed by wildlife (20%), goats (6%), and cattle (2%). The analysis revealed a significant inverse correlation between the annual mean temperature and the occurrence of cases and outbreaks (r2=0.306 and r2=0.379 respectively), indicating higher disease prevalence in states with lower temperatures. No statistically significant correlations were observed between disease occurrence and either precipitation or average wind speed. However, international studies suggest that wind can facilitate the long-distance dispersion of Culicoides, while mild temperatures extend vector survival. Conclusion: The results suggest that temperature is a determining factor in the spatial and temporal distribution of bluetongue in Brazil, whereas precipitation and wind speed have limited influence. The sporadic occurrence of the disease underscores the importance of continuous surveillance to prevent outbreaks and improve disease control. Strategies that account for vector population dynamics and climatic conditions could enhance the effectiveness of monitoring and control measures.