Seroprevalence of Rickettsia typhi and Rickettsia conorii infections in the Canary Islands (Spain)

Abstract

Objective: The aim of this work was to evaluate the prevalence of past infection due to Rickettsia typhi and Rickettsia conorii in the Canary Islands (Spain).

Methods: A representative sample of the population of the seven islands, formed of 662 people aged between 5 and 75 years (368 females, 294 males), was analyzed. Epidemiological data were obtained by direct survey. The detection of serum IgG antibodies against both microorganisms was based on an indirect immunofluorescence test, considered positive if the titers were ≥ 1/80.

Results: Of the analyzed population 3.9% had IgG antibodies against R. typhi and 4.4% against R. conorii. Out of these positive samples, only three were positive for both species. The seroprevalence was similar in both sexes. Positive results were found in all age groups, but a higher rate was noticed in those aged 46 years and older (p<0.05). R. typhi was found to be more prevalent in rural areas of all islands, as well as in farmers.

Conclusions: Our results confirm the presence of antibodies against the causative agents of murine typhus and Mediterranean spotted fever in the Canary Islands. Indirect data suggest that the detection of antibodies to R. conorii might be due to a cross-reaction between these species.