May 8, 1997 - Results. The prevalence of anti-phase n Coxiella IgG (titre 3=1:16) was 48.6% (95% con- fidence interval: 44.6-52.6%), with 81.3% having a titre of ^1:64. ... ducing endocarditis, osteoarthritis, etc.1'4 Q fever is an endemic disease in .... ^1:64. (one of them with IgM s« 1:256) was detected at the same time.
O Internationa] Epidemiological Association 1998
Inumatkmal Journal of Epidemiology 1998;27:142-145
Printed in Great Britain
High seroprevalence of Coxiella burnetii infection in Eastern Cantabria (Spain) F Pascual-Velasco,a M Montes, b JM Marim6n b and G Cillab
Background Coxiella burnetii is the causative agent of Q fever, a worldwide zoonosis which shows a wide diversity of clinical manifestations. The objective of this seroepidemiological study was to estimate the prevalence of antibodies to C. burnetii in a representative population of the Eastern area of the Cantabrian Community (Northern Spain). Methods A cross-sectional study was conducted in 595 subjects from Eastern Cantabria. Four different zones (one urban and three rural zones) were defined according to the geographical characteristics of the area and the economic activities of the population. The population sample for this study was collected between December 1994 and March 1995, and was stratified by age, sex and municipality of residence. IgG and IgM antibodies against C. burnetii were assayed by an indirect immunofluorescence technique. Results The prevalence of anti-phase n Coxiella IgG (titre 3=1:16) was 48.6% (95% confidence interval: 44.6-52.6%), with 81.3% having a titre of ^1:64. The prevalence of IgG increased with age, ranging from 12.0% in people 65 years (P < 0.001). The antibody detection rate was higher in males (53.6%) than in females (43.3%) (P < 0.01). The prevalence of anti-phase n Coxiella IgG was less among subjects living in the urban zone (32.8%) than in those living in the other three rural zones: the two situated on the coast (54.0% and 54.9% respectively) and the inner mountainous zone (82.3%) (P < 0.001). Conclusions The prevalence of C. burnetii infection observed in this study is one of the highest reported in Europe. The eastern area of Cantabria is a hyperendemic area for Q fever. Keywords Q fever, Coxiella burnetii, antibodies, prevalence, seroepidemiological study Accepted 8 May 1997
Q fever is a zoonosis distributed throughout the world and infections for large areas of Spain. In this paper we report the caused by Coxiella burnetii. Ungulate mammals (sheep, goats, and findings of a seroepidemiological study of Q fever carried out in cattle) are the main reservoirs and the most important source of Eastern Cantabria, in the north of Spain. infection for humans.1 Q fever has a broad spectrum of clinical manifestations ranging from asymptomatic infections to a febrile syndrome with or without signs of pneumonia, hepatitis or other Methods symptomatology.1"3 The infection may become chronic, pro- Geographical description ducing endocarditis, osteoarthritis, etc.1'4 Q fever is an endemic The Cantabrian Community resides in a mountainous area disease in Spain and its incidence seems to be particularly high fronted by the Cantabrian Sea (Atlantic Ocean). Its eastern area in the north of the country, especially in the Basque Country.5 (the study area) is 1032 km 2 and has a population of 74 936 However, there is little information on the prevalence of past inhabitants (Figure 1). The eastern area has mild climate with ' Department of Internal Medldne, Hospital Comarcal de Laredo. Cantabria. Spain. b
Department of Microbiology, Hospital NS Arfnzam, San Sebastlin. Gipuzkoa, Spain.
Reprint requests to: Mila Montes, Servido de Microbiologfa, Hospital NS Arfnzazu, Aptdo de Correos 477, 20080 San Scbastiin, Spain.
high and regular rainfall; the vegetation is composed of eucalyptus plantations, brushwood, and extensive grasslands and pastures. Cattle are the predominant livestock (around 80 000 head). Based on the geographical characteristics of the study area and the economic activities of the population, four zones can be denned: (1) Urban zone: consisting of centres of population located on the coast (Laredo, Santona and Colindres)
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C0X1ELLA BURNETII INFECTION IN SPAIN
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antigen in phase II (BioMerieux) at 1:64 dilution, after absorption with anti-IgG (RF Absorbens, Boehringwerke, Munich, Germany). For those sera with IgG against C. bumetii (phase II) *l:1024, the presence of IgG against phase I C. bumetii was also investigated by IFI. (Antigen in phase I was kindly provided by Dr Kazar, Virological Institute of Bratislava, Slovak Republic.)
CANTABftlAN SEA
Data analysis Standard statistical methods were used for data analysis. The x 2 and x2 for trend (Mantel-Haenszel) tests were used to compare prevalence. The level of significance chosen was a = 0.05.
Results Of the 595 subjects studied, 289 had anti-phase n Coxiella IgG (48.6%, 95% CI: 44.6-52.6%). A progressive increase in the seroprevalence of this antibody according to age was observed, so that 12.0% of the subjects 65 years (78/111) (x 2 for trend = 95.4; P< 0.001) (Figure 2). The mean age ±SD of the group was 44.8 ±21.8 years (range whose economy depends on fishing and service sector activities; 1-91; 65 years [111]). Of these subjects, 262 either side of the urban zone. These zones are formed by foot- lived in the urban area, 91 lived in the western coastal zone, hills of varying heights up to 500 m which become larger in the 163 in the eastern coastal zone and 79 in the mountainous area. eastern zone. They have small towns (Meruelo, Gama, Guriezo, Anti-phase II Coxiella IgG was observed in 86.4% (19/22) of Limpias and Ampuero) or larger concentrations of population the subjects >80 years. The antibody detection rates in males (Castro-Urdiales) involved in rural and farming activities. The and females were 53.6% (162/302) and 43.3% (127/293) reinner mountainous zone (4) has deep valleys and mountains as spectively (x2 = 6.3; P = 0.01; odds ratio [OR] = 1.51, 95% high as 1000 m. The population here works in farming activities CI : 1.08-2.12). The prevalence of anti-phase II Coxiella IgG (Alto Ason and Voto). was lower among the population who lived in the urban zone (32.8%: 86/262) than those observed among people living in Population study the western coastal zone (54.9%: 50/91), the eastern coastal The population sample for our seroprevalence study consisted zone (54.0%: 88/163) and in the inner mountainous zone of 595 subjects (302 males and 293 females) enrolled between (82.3%: 65/79) (x 2 , 3 d.f. = 65.3, P < 0.001) (Table 1). Among December 1994 and March 1995. The number of subjects in- the antibody-positive subjects, 54.7% (158/289) had low titres cluded in this group was determined on the basis of the size of (38/158 had 1:16; 16/158 had 1:32; and 104/158 had 1:64), population in Eastern Cantabria (1993 Census population 6 ), 41.2% (119/289) intermediate titres (1:128-1:512) and 4.2% and the results of a previous study which showed a seropreval(12/289) high titres (3=1:1024). In the latter, the presence of ence of 48% (worst acceptable result of ±4%, 95% confidence anti-phase 1 Coxiella IgG was investigated. In eight subjects this level). The group was stratified according to the age, sex and antibody was below the detection limit (ez-TraUero E, Cilia G, Montes M, Saenz-Dominguez JR, Alcorta M. Prevalence of Coxiella bumetii infection a m o n g slaughterhouse workers in northern Spain. Eur 3 Clin Microbiol Infect Dis 1995;14: 7 1 - 7 3 .
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