Rickettsial exposure in ruminants from Somalia

Rickettsia spp. are Gram-negative obligate intracellular bacteria, with Rickettsia africae being transmitted by Amblyomma ticks and posing a zoonotic risk. The status of diseases like rickettsiosis is largely unknown in Somalia. Our study investigates rickettsial exposure in livestock across two different regions in the country. A cross-sectional study collected 372 (190 goats, 133 cattle, 49 sheep) serum samples from the Benadir and Lower Shabelle regions of Somalia. Indirect immunofluorescence assays (IFA) were used to detect anti-R. africae and anti-Rickettsia rhipicephali antibodies, with sera diluted in two-fold increments starting at 1:64. Out of 372 samples, 188/372 (50.5 %) (endpoint titer: 64-2048) were seropositive for rickettsial antigens, with R. africae alone detected in 78/372 (21.0 %) and R. rhipicephali alone in 38/372 (10.2 %). Co-reactivity to both rickettsial antigens occurred in 72/372 (19.4 %) of samples. Cattle showed the highest seroreactivity at 90.2 %, mainly for R. africae, followed by sheep at 28.6 %, and goats at 28.4 %. Cattle and sheep were more likely to be seropositive than goats (OR: 24.5 and 1.1, respectively). This study provides the first serological evidence of Rickettsia spp. in ruminants from Somalia. Our findings suggest heightened susceptibility in cattle, posing health risks to humans, especially if cattle are considered sentinels for human exposure to R. africae.