Molecular Detection of Francisella spp. Among Ticks Attached to Camels in Egypt

This study was conducted to investigate the possible role of camels and attached ticks in the epidemiology of Francisella spp. including Francisella tularensis. For this purpose, a total of 319 ticks (248 Hyalomma dromedarii and 71 Amblyomma spp.) as well as 100 blood and 50 fecal samples collected from camels were screened for the presence of Francisella spp. by PCR through amplification of Francisella 16S rRNA gene. Positive samples were then tested for F. tularensis by PCR. In addition, serum samples from 75 camel abattoir workers were examined for the presence of IgG antibodies against F. tularensis using enzyme-linked immunosorbent assay (ELISA). Of the examined ticks, 15 were positive for Francisella spp. with prevalence of 4.7%, all positive results were recorded in Hyalomma dromedarii (6%). Neither blood nor fecal samples from camels yielded Francisella spp. even camels which carried Francisella spp. positive ticks. Moreover, F. tularensis could not be detected among Francisella-positive ticks. Phylogenetic analysis of some Francisella 16S rRNA gene sequences obtained in this study points out that these sequences are closely related to Francisella-like endosymbionts. In contrast, seroprevalence of F. tularensis antibodies among examined abattoir workers was 9.3% with significantly high prevalence among workers frequently exposed to tick bites (20.7%) rather than occasionally exposed workers (2.2%). In conclusion, however, F. tularensis could not be detected in this study; the high seroprevalence among camel abattoir workers especially those frequently exposed to tick bites underlines the possible role of ticks attached to camels in transmission of tularemia to humans.