An outbreak of relapsing fever unmasked by microbial paleoserology, 16th century, France

Objectives Depicting past epidemics currently relies on DNA-based detection of pathogens, an approach limited to pathogens with well-preserved DNA sequences. We used paleoserology as a complementary approach detecting specific antibodies under a mini line-blot format including positive and negative control antigens. Methods Mini line blot assay incorporated skim milk as negative control,Staphylococcus aureusas positive control, and antigens prepared from lice-borne pathogensRickettsia prowazekii,Borrelia recurrentis,Bartonella quintana, andYersinia pestis. Paleoserums were extracted from rehydrated dental pulp recovered from buried individuals. Mini line blots observed with the naked eye, were quantified using a scanner and appropriate software. Paleoserology was applied to the indirect detection of lice-borne pathogens in seven skeletons exhumed from a 16th-17th century suspected military burial site (Auxi-le-Chateau); and 14 civils exhumed from a 5th-13th century burial site (Saint-Mont). Direct detection of pathogens was performed using quantitative real-time PCR. Results In Auxi-le-Chateau, paleoserology yielded 7/7 interpretable paleoserums including 7/7 positives forB. recurrentisincluding one also positive forB. quintana. In Saint-Mont, paleoserology yielded 8/14 interpretable paleoserums and none reacted against any of the four pathogens. Antibodies againstR. prowazekiiandY. pestiswere not detected. The seroprevalence was significantly higher in the military burial site of Auxi-le-Chateau than in the civil burial site of Saint-Mont. Real-time PCR detection ofB. quintanayielded 5/21 positive (3 at Saint-Mont and 2 at Auxi-le-Chateau) whereasB. recurrentiswas not detected. Conclusions Paleoserology unmasked an outbreak of relapsingB. recurrentisfever in one 16th - 17th century military garrison, missed by real-time PCR. Paleoserology offers a new tool for investigating past epidemics, in complement to DNA sequence-based approaches.