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P21SEROEPIDEMIOLOGIC SURVEY FOR Coxiella

burnetti ANTIBODIES AMONG HEALTHY ADULTS IN CHILE

Weitzel Thomas 1, López Javier 2, Acosta-Jamett Gerardo 3, Edouard Sophie , Parola Phillipe , Azócar Teresa , Morales Sara 1, Abarca Katia 5

1 Clínica Alemana de Santiago, Facultad de Medicina Clínica Alemana, Universidad del Desarrollo, Santiago, Chile. 2 Hospital Veterinario Puente Alto, Santiago, Chile. 3 Instituto de Medicina Preventiva Veterinaria y Programa de Investigación Aplicada en Fauna Silvestre, Facultad de Ciencias Veterinarias, Universidad Austral, Valdivia, Chile.4 University Hospital Institute for Infectious Diseases and Tropical Medicine, Aix-Marseille University, National Reference Center for Rickettsial Diseases, Marseille, France. 5 Laboratorio de Infectología y Virología Molecular, Departamento de Enfermedades Infecciosas e Inmunología Pediátricas, Facultad de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile

E-mail: thomas.weitzel@gmail.com

Coxiella burnetti is a zoonotic pathogen infecting various domestic and wild mammals, birds, and arthropods such as ticks. The most important reservoirs for human infections are domestic ungulates such as cattle and sheep, although pets can also be infected. Human infections (Q fever) might be asymptomatic or present as acute or chronic disease often with discrete or nonspecific symptoms. It is assumed that C. burnetii is of global distribution (with the exception of New Zealand). In South America, only few epidemiological data are available and systematic studies are lacking; so far, human infections have been reported from 7 countries. In Chile, diagnostic test for human Q fever are not available and epidemiological data on human infections have not been published. Objective:

Este documento está disponible en http://www.revbiomed.uady.mx/pdf/rb1526S154.pdf

Suplemento 1-2015 115

To determine the seroprevalence of anti-Coxiella burnetii antibodies in healthy adults of different regions of Chile. A cross-sectional study was conducted between 2010 and 2012 including 4 Chilean regions: Arica and Parinacota (XV), Coquimbo (IV), Santiago Metropolitan (RM), and Araucanía (IX). In each region, health adult volunteers were included by household-based randomized and convenience sampling performed in urban and rural settings, respectively. After written consent, serum samples were drawn and screened for phase II anti-Coxiella IgG by ELISA (Virion/Serion, Würzburg, Germany). Indeterminate or positive results were confirmed by immunofluorescence (IFA) with poly- and monospecific (IgG I, IgM I, IgA I, IgG II, IgM II, IgA II) assays (in-house, Unité des Rickettsies,

Weitzel et al.

Revista Biomédica 116

Marseille, France). Cross-reactions with Rickettsia conorii, R. typhi, R. felis, Francisella tularensis, Anaplasma phagocytophilum, Bartonella hense-lae, and B. quintana were excluded by IFA. A total of 1126 individuals were included (XV urban, 135; XV rural, 130; IV urban, 148; IV rural, 141; RM urban, 146; RM rural, 144; IX urban, 140; IX rural, 142). By ELISA screening, 4 samples were tested positive and 4 indeterminate without significant differences by region or setting. Only 1 sample (from IX rural) was confirmed showing a weakly positive result by IFA. Our study showed a very low IFA-based human C. burnetii seroprevalence of 0.09% (CI95: 0.02-0.50).

Since cross-reactions with various other bacterial pathogens such as Legionella, Bartonella, Rickettsia, Ehrlichia, and Chlamydia might cause false positive Q fever serology, it can be assumed that in Chile human Q fever is of extremely low prevalence or absent. Further studies including other Chilean regions as well as serological and molecular studies in animals and humans are necessary to confirm this result. Our study also shows that seroepidemiological studies only relying on ELISA screening might overestimate Q fever prevalence especially in low-prevalence areas, where the positive predictive value of such screening test is low.