Risk factors of Crimean-Congo haemorrhagic fever outbreak in Central Anatolia: a case control study

Abstract number: 1135_278

Çevik M.A, Uzun R., Yilmaz N., Ugurlu M., Elaldi N., Bodur H., Bakir M., Vahaboglu H.

Objectives:  

An outbreak of CCHF evolved through 2002–2003 in Central Anatolia in Turkey. To demonstrate the risk factors and potential sources or dissemination vehicles of this outbreak a case control study in the region was undertaken.

Methods:  

Cases were the patients those admitted to tertiary care hospitals in 2003 with an illness consistent with CCHF and a positive IgM or RT-PCR test result. Two controls per case were selected randomly among those living in the same villages but not experienced a similar illness during the last 3 years. As being potential confounding parameters, age (+10 years) and gender were controlled. A questionnaire was filled by home visits at the region while a blood sample was obtained for serologic screening of specific IgG and IgM antibodies. Statistical analysis was performed by the software NCSS (Number Cruncher Statistical Systems, ver. 2004). Dichotomous variables were compared by Chi-square or Fisher's Exact Test where applicable. Statistical comparisons were always two tailed.

Results:  

A total of 62 cases were reachable. Accordingly, 124 controls were selected. Among the risk factors compared only ‘tick exposure before the unset of disease’ was significant (OR, 13.33; CIs, 6.39–27.81). Cases those experienced ticks bites mostly described domestic animals and rural areas out of villages for tick exposure (data not shown). Serologic screening between cases and controls were significant, as well. These comparisons and demographic characteristics, such as age and gender were shown in Table 1.

Table 1.  Some demographic features and one significant risk factor (tick bite) and serologic torts between cases and controls

Discussion:  

This study demonstrated that tick bite was the single significant risk factor responsible for this outbreak. Animal keeping, buying and selling is widespread in the region (83.3%). Domestic animals could be a source for tick exposure. However, some cases described certain areas out of villages for thick exposure, as well. One important point was that, cases were mostly scattered. Except few examples, they were mostly from different houses. If the live stocks are the source of infected ticks we would found clusters from same houses. The significant difference in the serologic survey between cases and controls supported this view as well. This study, in other words, indicated that rural areas with a heavy tick infestation must be the most likely source of this outbreak. However, more studies in the region are warranted to explore the source of this outbreak and eventually to control it.