Minimal Rickettsial Infection Rates and Distribution of Ticks in Uganda: An Assessment of the Seasonal Effects and Relevance to Tick-Borne Disease Risk in East Africa

Tick-borne diseases (TBDs) pose a significant risk to humans and represent one of the major factors influencing readiness within the United States' military worldwide. Additionally, ticks and TBDs constitute major animal health problems leading to economic losses at multiple levels affecting low- and middle-income countries the hardest. Tick control is frequently hampered by issues ranging from acaricide resistance to lack of data on tick distribution and infection rates. We conducted a cross-sectional study to assess tick species distribution, host use, and rickettsial pathogen infection rate of ticks in different areas of the Uganda Cattle Corridor. We identified 4,425 hard ticks (Ixodida: Ixodidae) comprised of seven species by morphological characters with 3,315 ticks collected from four locations during the dry season and 1,110 ticks from one location during the wet season. Rickettsial pathogen prevalence was assessed in ticks collected from two districts to determine the minimum infection rate compared across seasons, village location, and tick species. We found statistically significant differences in the abundance and distribution of tick species among districts in the dry season, host animal species, and the proportion of rickettsial positive pools between villages. Seasonality, village location, and tick species do not affect the minimum infection rate of rickettsial pathogens of ticks in Uganda, but village location affects the proportion of positive tick pools. These results indicate geographical and seasonal differences among pathogen-harboring ticks contributing to our understanding of the current distribution of ticks and TBDs in Uganda.