European Journal of Epidemiology 12: 245-250, 1996. © 1996 Kluwer Academic Publishers. Printed in the Netherlands. Seroepidemiological survey of Q fever in Le6n Province, Spain j. Su~irez_Estrada 1,2 J.I. Rodriguez-Barbosa ~, C.B. Guti6rrez-Martin 1, M.R. Castafieda-L6pez 2, J.M. Fernfindez-Marcos 2, O.R. Gonzfilez-Llamazares ~ & EoF. Rodriguez-Ferri ~ Departamento de Patologfa Animal (Sanidad Animal), Unidad de Microbiologia e Inmunologia, Facultad de Veterinaria de Le6n, Spain; 2Centro de Atenci6n Primaria de Salud, Mansilla de las Mulas, Le6n, Spain Accepted in revised form 15 March 1996 Abstract. A seroepidemiological survey, using an indirect immunofluorescence test against Coxiella burnetii (antigenic phase II), was carried out in Le6n province, north-western Spain. A total of 406 serum samples was collected from people (from 15 to more than 65 years old) living in a rural environment during the winter and spring of 1994. The overall prevalence was 40.6%, titres ranged from 1:80 to 1:640, and a titre of 1:80 was encountered among 60.6% of positive samples. A significant higher prevalence was observed among males globally, as well as among those aged 15-44 and 45-64 years old; however, no difference was encountered among males and females older than 64 years. In the same way, a significant higher Q fever prevalence was observed among individuals having occupations related to agriculture and among those having close relationship with animals. Key words: Coxiella burnetii, Q fever, Sero-epidemiology, Spain ~ntroduction Coxiella burnetii is a gram-negative, short, rod- shaped organism, belonging to the family Rickettsiaceae. It is the causative agent of Q fever, a zoonotic disease of worldwide distribution. C. burnetii has been isolated from arthropods like ticks, birds and many domestic and wild mammalians. Among them, the infection is particularly prevalent in cattle, sheep and goats, which are considered to be the main reservoirs for this organism [1]. In man, Q fever can occur in two clinical presentations: acute and chronic. The acute form is usually a flu-like disease accompanied by fever and severe headache, but interstitial pneumonia, hepatitis or meningoen- cephalitis may sometimes develop. The chronic form is characterized by a severe endocarditis, often resulting in the destruction of heart valves. This last form may appear several years after the acute disease [2-4]. It is generally accepted that Q fever is a profes- sional disease, appearing mainly among individuals involved in the transport or care of domestic animals and in meat and dairy industries. However, the high degree of resistance of Coxiella burnetii to chemical agents, dessication and elevated temperatures because of the formation of an endospore-like body, as well as the fast spread of tile infection by aerosols, increase considerably the number of individuals susceptible to this disease [2, 3]. Unlike other zoonosis in Spain, Q fever is not subjected to epidemiological vigilance either recorded individually as a disease to be diagnosed in medical morbidity questionnaires. For this reason, data on their incidence are only obtained from hos- pitalized clinical cases, different outbreaks recog- nized in some Autonomous Communities, and papers published in scientific journals. Different sero- epidemiological prospecting surveys carried out in several Autonomous Communities in Spain showed a great difference in the distribution of infection (see Table 1). Up to date, no kind of serological survey has been made in Le6n province and, therefore, no data about incidence and prevalence of Q fever are available. However, the presence of infection can be easily suspected because of the high density of cattle, sheep and goat herds in Le6n Province, as well as the high percentage of population directly or indirectly involved in agrarian works. The goal of our survey was to determine whether Q fever infection occurs in Le6n Province (north- western Spain). Therefore, 406 human sera coming from a mainly agrarian rural area were tested for the presence of serum antibodies directed to C. burnetii by using an indirect fluorescent antibody test (IFAT). Individuals and methods Population study. A collection of 406 sera was sampled from human donors in Le6n Province, Autonomous Community of 'Castilla y Le6n' (north-