Retrospective study of the epidemiological risk and serological diagnosis of human babesiosis in Asturias, Northwestern Spain

Abstract

Background: Babesiosis is a globally growing tick-borne disease in humans. Severe babesiosis caused by Babesia divergens has been recently reported in patients from Asturias (Northwestern Spain) suggesting an undetected risk of the disease. To analyze this risk, we retrospectively evaluated the seroprevalence of babesiosis in the Asturian population from 2015 through 2017, an intermediate period when severe human babesiosis cases occurred. Methods: To detect B. divergens IgG antibodies in 120 serum samples from Asturian patients infected with the tick-transmitted spirochete Borrelia burgdorferi sensu lato (s.l.) indirect fluorescent assay (IFA) and Western-blot assays were performed. This condition indicated exposure to tick bites Results: This retrospective study confirmed a B. divergens seroprevalence rate of 39.2% according to IFA results. B. divergens incidence was 7.14 cases/100,000 population, exceeding previously reported seroprevalence rates. No differences in epidemiology and risk factors were found between patients infected solely with B. burgdorferiand those doubly infected with B. burgdorferi s.l. and B. divergens. Patients with both infections lived in Central Asturias, had a milder clinical course and, according to Western-blot results, developed different humoral responses against B. divergens. Conclusions: B. divergens parasites have circulated for several years in Asturias causing unnoticed infections in humans. Epidemiological evidences of babesiosis makes Asturias an emerging risk area for this zoonosis. Silent human babesiosis could also be relevant in other Spanish and European regions affected by babesiosis. Hence, the potential risk of babesiosis on human health in Asturias and other European forest regions needs to be addressed by the sanitary authorities.

Clinical, analytical, imaging and ECG differences in adult patients infected by Borrelia burgdorferi and doubly-infected by Babesia divergens-Borrelia burgdorferi

“…In Europe B. microti and B. divergens positive antibodies were observed in 16.3% of Swedish patients seropositive for Borrelia 8 .Since 2011 two cases of severe infection by B.divergens have been reported in Asturias, probably the iceberg of an undetected B.divergens-infected population 9,10 . We detected a B.burgdorferi-B.divergens coinfection rate of 39.2% in adult patients with con rmed borreliosis from Asturias in a retrospective study 11 . The number of symptoms and duration of illness in American patients with concurrent Lyme disease and babesiosis due to B. microti were higher than in patients with either infection alone 7,12,13 .…”

“…The strength of our study relies in being the rst report studing clinical differences, analytical, imaging and ECG between patients mono or doubly-infected with B.divergens-B.burgdorferi. Their B.divergens infection had been previously diagnosed using some novel diagnostic techniques 11 . The mean weakness of the study is derived of its retrospective design lacking universal ECG, cardiac biomarkers and echocardiograms testing that might provide deeper insight into the mechanism of cardiac complications in these doubly infected patients.…”

“…In a subsequent study, stored serum samples seropositive for B. burgdorferi s.l. were used again to detect IgG antibodies against B. divergens by an in-house indirect uorescent assay (IFA) and by Western Blot at the Parasitology Service, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain 11 .…”

“…Detection of B. burgdorferi s.l. antibodies was done using an automated qualitative test (Vidas, BioMerieux, Madrid, Spain) 11 and by immunoblot (Borrelia IgG IgM EcoLine, Sekisui Diagnostics, Russelsheim, Germany) 3,11 . Patients' serum samples positive for Lyme disease were stored at -80ºC at the Microbiology Service of the HUCA for further studies.…”