Coxiella burnetii in camels (Camelus dromedarius) from Algeria: Seroprevalence, molecular characterization, and ticks (Atari: Ixodidae) vectors

Q fever is a widespread zoonotic disease caused by Coxiella burnetii that most commonly infects not only a variety of mammals but also arthropods and in particularly ticks. The aim of this study was to detect C. burnetii infection in camels including ixodid ticks using serological and molecular assays. Between July 2018 to June 2019, blood samples from 184 male and female camels (Camelus dromedarius) were collected from 3 regions of South East Algeria and serum samples were tested for antibodies against Coxiella burnetii using indirect enzyme-linked immunosorbent assay (ELISA) kit. The positive sera and a total of 60 ticks were tested by quantitative PCR (qPCR) for detection of C. burnetii with primers and probes specific to the transposon-like repetitive region (IS1111 gene). Positive samples were genotyped by amplification and sequencing of partial sequences based on the IS1111 gene. The seroprevalence of antibodies against C. burnetii was 75.5%. Statistical analysis pointed out three potential risk factors associated with Q fever infection: geographic location, age class and season. No positive DNA of camel blood sample was observed. However, five Hyalomma dromedarii, one H. impeltatum and one H. excavatum tick species were detected positive for Coxiella burnetii DNA by qPCR, with an overall prevalence rate of 11.66% (7/60). The revealed Algerian strains by phylogenetic and comparative analysis of the IS1111 nucleotide sequences were clustered with several pathogenic C. burnetii strains isolated from ticks, human, and cattle located in Tunisia, Greece and in some Mediterranean countries, respectively. The study results clearly indicate that camels and their ticks in Algeria may play an important role as a reservoir for C. burnetii and can be considered as a significant source of Q fever transmission to other animal species and humans.