Predicting the Spatial Distribution of Hyalomma ssp., Vector Ticks of Crimean–Congo Haemorrhagic Fever in Iraq

Abstract

Crimean–Congo hemorrhagic fever (CCHF) typically spreads through ticks and is categorized as a viral hemorrhagic fever. CCHF is a fatal endemic disease in Iraq, and it has been reported sporadically since its first report in 1979. Recent outbreaks during 2021–2023 and their fatal consequences captured the interest of this study. CCHF is a tick-borne disease that represents a major challenge to the public health, social, and economic sectors. The geographical distribution of CCHF is closely linked with Hyalomma vector tick distribution. Therefore, predicting and mapping the spatial distribution of the disease vector in relation to relevant environmental factors provides invaluable information for establishing an early warning system based on which preventive measures can be taken to minimize the spread and, hence, the fatal consequences of CCHF. To achieve this, this study incorporates geospatial techniques and maximum entropy modeling (Maxent) to assess the habitat suitability of the Hyalomma vector and to identify the key environmental drivers contributing to its spatial distribution in Iraq. Utilizing the area under the ROC curve (AUC) as the performance metric, the model evaluation yielded successful results in predicting habitat suitability for Hyalomma vector ticks in Iraq. The AUC attained an average score of 0.885 with a regularization multiplier (β) set at 1. The Hyalomma ticks’ suitable habitat distribution within the study area covers a fraction of the total land, at approximately 51% (225,665 km2) of the entire 441,724 km2 region. Among these suitable areas, 41.57% (183,631 km2) were classified as lowly suitable, 8.61% (38,039 km2) as moderately suitable, and 0.9% (3994 km2) as highly suitable. Several factors have significantly influenced Hyalomma vector tick distribution in Iraq. These include land cover (accounting for 50.8%), elevation (contributing 30.4%), NDVI (5.7%), temperature seasonality (4.7%), precipitation seasonality (3.3%), sheep density (2.3%), goat density (2.2%), and the mean diurnal range (0.5%). The findings of this study could have significant implications for establishing a strategic early warning system and taking preventive measures beforehand to minimize and control Crimean–Congo haemorrhagic fever in Iraq and similar ecoregions in the Middle East. As a primary precaution, this study recommends focusing on highly suitable areas (3994 km2) in the southern part of Iraq for management and preventive actions.