Rickettsia felis, the agent of flea-borne spotted fever, in mosquitoes on St Kitts, West Indies
Authors: Matthew John Valentine, Md Monirul Hoque, Chengming Wang, Patrick John Kelly
Journal: The Lancet Microbe (2021)

Rickettsia felis, the agent of flea-borne spotted fever, is an emerging vector-borne pathogen with a worldwide distribution.1Abdad MY Stenos J Graves S Rickettsia felis, an emerging flea-transmitted human pathogen.Emerg Health Threats J. 2011; 47168Crossref PubMed Scopus (56) Google Scholar The established vector and reservoir of R felis is the cat flea (Ctenocephalides felis), but recently the organism has been detected in mosquitoes in Africa, China, and the USA,2Barua S Hoque MM Kelly PJ et al.First report of Rickettsia felis in mosquitoes, USA.Emerg Microbes Infect. 2020; 9: 1008-1010Crossref PubMed Scopus (4) Google Scholar and Anopheles gambiae has been identified as a potential vector.3Dieme C Bechah Y Socolovschi C et al.Transmission potential of Rickettsia felis infection by Anopheles gambiae mosquitoes.Proc Natl Acad Sci USA. 2015; 112: 8088-8093Crossref PubMed Scopus (75) Google Scholar As part of an ongoing study of mosquito-borne diseases in the Caribbean,4Valentine MJ Ciraola B Aliota MT et al.No evidence for sylvatic cycles of chikungunya, dengue and Zika viruses in African green monkeys (Chlorocebus aethiops sabaeus) on St. Kitts, West Indies.Parasit Vectors. 2020; 13: 540Crossref PubMed Scopus (1) Google Scholar we tested individual mosquitoes from 24 locations on St Kitts, West Indies for R felis using citrate synthase (gltA)-based fluorescence resonance energy transfer (FRET) and nested PCRs, and standard PCRs for outer membrane protein B (ompB) and the R felis-specific biotin synthase (BioB) genes.2Barua S Hoque MM Kelly PJ et al.First report of Rickettsia felis in mosquitoes, USA.Emerg Microbes Infect. 2020; 9: 1008-1010Crossref PubMed Scopus (4) Google Scholar PCR and DNA sequencing revealed R felis DNA (GenBank accession numbers MW450784, MW459165) in individual Culex quinquefasciatus (six [13%] of 46), Aedes aegypti (two [6%] of 34), and Aedes taeniorhynchus (one [4%] of 28). This is, to our knowledge, the first report of R felis in these mosquito species, all of which readily feed on people and are known vectors of viruses including chikungunya, dengue virus, yellow fever virus, and Zika virus (Ae aegypti); Venezuelan equine encephalitis virus, Eastern equine encephalitis virus, and Western equine encephalitis virus (Ae taeniorhynchus); West Nile virus, St Louis encephalitis virus, and, the non-viral disease, lymphatic filariasis (Cx quinquefasciatus). Mosquitoes that were positive for R felis were found in eight (33%) of the 24 sites sampled in St Kitts, indicating that infected mosquitoes are widespread on the island. R felis is already known to occur in cat fleas on St Kitts and Dominica,5Kelly PJ Lucas H Eremeeva ME et al.Rickettsia felis, West Indies.Emerg Infect Dis. 2010; 16: 570-571Crossref PubMed Scopus (15) Google Scholar another Caribbean island. On the basis of our current findings, when travel restrictions due to COVID-19 resolve and tourism resumes, health-care workers should be alerted to the possibility of flea-borne spotted fever in patients returning from holidays in the Caribbean with a history of flea bites or mosquito bites. Definitive diagnosis of infection is by PCR of whole blood or serum samples for R felis, and treatment with doxycycline appears effective.1Abdad MY Stenos J Graves S Rickettsia felis, an emerging flea-transmitted human pathogen.Emerg Health Threats J. 2011; 47168Crossref PubMed Scopus (56) Google Scholar We declare no competing interests.