Prevalence of Rickettsia africae in tick vectors collected from mammalian hosts in sub-Saharan Africa: A systematic review and meta-analysis

Alicia Pillay; Tawanda Manyangadze; Samson Mukaratirwa

doi:10.1016/j.ttbdis.2022.101960

Prevalence of Rickettsia africae in tick vectors collected from mammalian hosts in sub-Saharan Africa: A systematic review and meta-analysis

Ticks Tick Borne Dis. 2022 Jul;13(4):101960. doi: 10.1016/j.ttbdis.2022.101960. Epub 2022 Apr 26.

Authors

Alicia Pillay¹, Tawanda Manyangadze², Samson Mukaratirwa³

Affiliations

¹ School of Life Sciences, Biological Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Westville Campus, Durban, South Africa. Electronic address: aliciajacksonpillay@gmail.com.
² School of Nursing and Public Health, Department of Public Health Medicine, University of KwaZulu-Natal, Durban, South Africa; Geography Department, Faculty of Science and Engineering, Bindura University of Science Education, Bag 1020, Bindura, Zimbabwe.
³ School of Life Sciences, Biological Sciences, College of Agriculture, Engineering and Science, University of KwaZulu-Natal, Westville Campus, Durban, South Africa; One Health Center for Zoonoses and Tropical Veterinary Medicine, Ross University School of Veterinary Medicine, Basseterre, St. Kitts, West Indies.

PMID: 35537238
DOI: 10.1016/j.ttbdis.2022.101960

Abstract

African tick bite fever (ATBF) is one of the most important rickettsial infections in international travellers to sub-Saharan Africa. The heterogeneity of Rickettsia africae infection rates among tick vector species has been studied. However, this information has not been systematised to allow for comparative estimates. Quantifying the trends and heterogeneity in R. africae infection rates among the different tick vector species is paramount in understanding the role in transmission to humans. A systematic search was conducted in PubMed, Web of Knowledge, Google Scholar, and SCOPUS from 2005 to 2020. The selection criteria included all studies in sub-Saharan Africa reporting R. africae infection rates in tick adults, nymphs, and larvae. A quality effects model was used in the meta-analysis due to the observed heterogeneity with an assessment of publication bias using funnel plots. The prevalence estimates were conducted by geographic region and tick genus from 32 studies reporting R. africae infection rates in ticks from sub-Saharan Africa. A total of 12,301 ticks comprising of adults (96.19%, n=11, 832), nymphs (3.6%, n=443) and larvae (0.2%, n=26) and 1214 pooled samples were evaluated for R. africae infection. The overall prevalence of R. africae was higher in Amblyomma spp. (48%, 95% CI: 26-70%) compared to Rhipicephalus spp. (1%, 95% CI: 0-5%), Hyalomma spp. (1%, 95% CI: 0-3%) and other tick genera (1%, 95% CI: 0-4%) throughout all regions. The highest prevalence in Amblyomma spp. was recorded in western Africa (53%, 95% CI: 14-90%) and in Rhipicephalus spp. in southern Africa (2%, 95% CI: 0-5%). Cattle were the most frequently sampled hosts across all tick vectors (62.98%, n=5492), followed by goats (19.07%, n= 1663) and sheep (9.1%, n= 793). To our knowledge, this is the first systematic and quantitative analysis of R. africae infection in tick vectors collected from mammalian hosts in sub-Saharan Africa. The results highlight a marked heterogeneity between species in different regions of sub-Saharan Africa and provide initial estimates of infection rates.

Keywords: African tick bite fever; Geographical distribution; Meta-analysis; Prevalence; Rickettsia africae; Tick vectors.

Publication types

Meta-Analysis
Review
Systematic Review

MeSH terms

Africa South of the Sahara / epidemiology
Amblyomma
Animals
Cattle
Mammals
Nymph
Prevalence
Rhipicephalus*
Rickettsia*
Sheep
Spotted Fever Group Rickettsiosis*

Supplementary concepts

Rickettsia africae