Wide distribution of Mediterranean and African Spotted fever agents and the first identification of Israeli Spotted Fever agent in ticks in Uganda
Authors: Eneku Wilfred , Erima Bernard , Byaruhanga Anatoli Maranda , Atim Gladys , Tugume Titus , Ukuli Qouilazoni A. , Kibuuka Hannah , Mworozi Edison , Burrows Christina , Koehler Jeffrey W. , Cleary Nora G. , von Fricken Michael E. , Tweyongyere Robert , Wabwire-Mangen Fred , Byarugaba Denis K. 
Published: March 2023

Rickettsiamicroorganisms are causative agents of several neglected emerging infectious diseases transmitted to humans by ticks among other arthropod vectors. In this study, ticks were collected from four geographical regions of Uganda, pooled in sizes of 1-179 ticks based on location, tick species, life stage, host, and time of collection, and were tested by real time PCR forRickettsiaspecies harboured. The tick pools were tested with primers targetinggltA, 17kDaandompA genes, followed by Sanger sequencing of17kDaandompAgenes. Of the 471 tick pools tested, 116 (24.6%) were positive forRickettsiaspp. by thegltAprimers. The prevalence ofRickettsiavaried by district with Gulu recording the highest (30.1%) followed by Luwero (28.1%) and Kasese had the lowest (14%). Tick pools with highest positivity rates were from livestock (cattle, goats, sheep, and pigs), 26.9%, followed by vegetation 23.1% and pets (dogs and cats) 19.7%. Of 116gltA-positive tick pools, 86 pools were positive using17kDaprimers of which 48 purified PCR products were successfully sequenced. The predominantRickettsiaspp. identified wasR. africae(n=15) in four tick species, followed byR. conorii(n=5) in three tick species (Haemaphysalis elliptica, Rhipicephalus appendiculatus, andRh. decoloratus).Rickettsia conoriisubsp.israelensiswas detected in one tick pool. These findings indicate that multipleRickettsiaspp. capable of causing human illness are circulating in the four diverse geographical regions of Uganda including new strains previously known to occur in the Mediterranean region. Physicians should be informed aboutRickettsiaspp. infections as potential causes for acute febrile illnesses in these regions. Continued and expanded surveillance is essential to further identify and locate potential hotspots withRickettsiaspp. of concern.

Author Summary

Tick-borne rickettsioses are emerging infectious diseases of public health importance worldwide. Spotted fever rickettsioses transmitted by ticks can cause mild to severe human illness depending on theRickettsiaspp. and co-morbidities. Their diagnosis is challenging due to non-specific symptoms particularly in limited resource settings. Little is known about their prevalence in Uganda. Using entomological and molecular tools, we surveyed and studied tick-borne spotted fever rickettsioses in five districts from four diverse eco-regions of Uganda. Overall, 24.6% (116/471) tick pools were positive forRickettsiaspecies. By sequencing the17kDaandompAgenes ofRickettsia, we identifiedR. africaeas the most common agent, followed byR. conoriiandR. conoriisubsp.israelensis. The findings indicate multipleRickettsiaspp. that can cause febrile illness in humans are circulating in the four geographically diverse regions of Uganda. Physicians should be aware these agents are potential causes of febrile illness in these areas, particularly in individuals who encounter livestock or their grazing areas.