Space-time clustering of rabies in equines in Brazil from 2006 to 2023.

Overview

• This study analyzed how rabies cases in horses in Brazil were distributed across different regions and over time from 2006 to 2023.
• It identified patterns and clusters of rabies cases, highlighting areas with the highest risks and trends in disease incidence.

Background and Objectives

• Rabies is a deadly disease caused by the rabies virus, often spread by vampire bats in Brazil.
• Brazil has the largest horse population in South America, making equine rabies a significant concern for both economic and public health reasons.
• The main goal was to understand where and when rabies cases in horses were occurring to improve disease monitoring and control.

Data and Methods

• Data Source: Rabies cases data from the Zoosanitary Information System (SIZ), managed by the Brazilian Ministry of Agriculture, Livestock, and Food Supply (MAPA).
• Study Duration: 2006 to 2023.
• Incidence Risk Calculation: Risk was measured as the number of rabies cases per 100,000 horses in different regions and administrative units (Federative Units).
• Spatial and Temporal Analysis:
  • Spatiotemporal scan analysis using the Poisson statistical model performed with SaTScan™ software to detect clusters of cases in both space and time.
  • Temporal trend analysis using segmented log-linear regression with Joinpoint Regression to identify changes in rabies incidence rates over the years.

Findings – Spatial Distribution

• A total of 2170 equine rabies cases were reported during the study period.
• The Southeast region of Brazil had the highest number of cases (41.66%), followed by the Central-West region (24.47%).
• Federative Units with highest incidence risk per 100,000 equines:
  • Espírito Santo: 124.68
  • São Paulo: 69.97
  • Rio de Janeiro: 69.03
• Four major clusters of rabies cases were identified retrospectively, with significant clusters occurring in:
  • São Paulo
  • Mato Grosso
  • Espírito Santo
  • Rio de Janeiro
  • Amazonas
• Prospective (current active) clusters were found in:
  • São Paulo
  • Espírito Santo
  • Amazonas

Findings – Temporal Trends

• Overall, the incidence of equine rabies in Brazil showed a decreasing trend from 2006 to 2023.
• The annual percentage change (APC) was -3.9%, indicating an average yearly decline.
• This decline was statistically significant within a 95% confidence interval ranging from -6.2% to -1.5%.

Implications and Recommendations

• Identification of high-risk regions and active clusters supports targeted epidemiological surveillance and vaccination campaigns.
• Declining trend suggests current control measures may be effective but ongoing monitoring is essential to prevent resurgence.
• Findings help policymakers allocate resources efficiently, focusing on the most affected Federative Units such as Espírito Santo, São Paulo, and Rio de Janeiro.
• Understanding spatial and temporal patterns aids in predicting outbreaks and implementing timely interventions, minimizing economic losses and public health risks.