# Ticks on the run: A mathematical model of Crimean-Congo Haemorrhagic Fever (CCHF)-key factors for transmission

**Authors:** Suman Bhowmick, Khushal Khan Kasi, Jörn Gethmann, Susanne Fischer, Franz J. Conraths, Igor M. Sokolov, Hartmut H. K. Lentz  
**arXiv:** [2101.11471](https://arxiv.org/abs/2101.11471)  
**Date:** 2021-01-27  
**Summary page:** https://www.summarizepaper.com/en/paper/2101.11471v1/

## Key points

- Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne zoonotic disease caused by the CCHFV virus
- Ticks belonging to the genus \textit{Hyalomma} are the main vectors and reservoir for the virus
- CCHFV is prevalent in wide geographical areas including Asia, Africa, South-Eastern Europe and the Middle East
- Several outbreaks of CCHFV have been observed in Europe over the last decade, mainly in Mediterranean countries
- The disease has a high case/fatality ratio in humans, sometimes reaching up to 40%
- Climate change and invasion of CCHFV vectors into Central Europe suggest that transmission could be established there in future
- A compartment-based nonlinear Ordinary Differential Equation (ODE) system was developed to model disease transmission involving ticks, livestock and humans
- Decreasing tick survival time is an effective method to eradicate CCHF according to sensitivity analysis of basic reproduction number $R_0$
- Tick-to-tick transmission through co-feeding and CCHFV circulation through trasstadial and transovarial stages sustain the disease cycle
- The proposed model dynamics were calibrated through an empirical multi-country analysis revealing different sets of disease parameters across countries burdened with CCHF; this information may help select more efficient control strategies.

## Summary

Crimean-Congo haemorrhagic fever (CCHF) is a tick-borne zoonotic disease caused by the Crimean-Congo hemorrhagic fever virus (CCHFV). Ticks belonging to the genus \textit{Hyalomma} are the main vectors and reservoir for the virus, which is maintained in nature in an endemic vertebrate-tick-vertebrate cycle. CCHFV is prevalent in wide geographical areas including Asia, Africa, South-Eastern Europe and the Middle East. Over the last decade, several outbreaks of CCHFV have been observed in Europe, mainly in Mediterranean countries. Due to its high case/fatality ratio in humans, sometimes reaching up to 40%, it is of great importance for public health. Climate change and the invasion of CCHFV vectors into Central Europe suggest that transmission could be established there in future. To better understand this disease's transmission dynamics and develop potential control measures for eradicating or controlling outbreaks, researchers developed a compartment-based nonlinear Ordinary Differential Equation (ODE) system that models the disease transmission cycle involving blood-sucking ticks, livestock and humans. Sensitivity analysis of the basic reproduction number $R_0$ shows that decreasing tick survival time is an effective method to eradicate CCHF. The model also highlights important factors that sustain the disease cycle such as tick-to-tick transmission through co-feeding and CCHFV circulation through trasstadial and transovarial stages. The proposed model dynamics were calibrated through an empirical multi-country analysis revealing different sets of disease parameters across countries burdened with CCHF; this information may help select more efficient control strategies. In conclusion, this study provides insight into key factors influencing CCHF transmission dynamics and suggests potential control measures for eradicating or controlling outbreaks. With climate change increasing vector distribution ranges worldwide, understanding how diseases like CCHF spread can aid public health officials in taking proactive steps towards preventing future outbreaks.