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Table of Contents
Year : 2019  |  Volume : 56  |  Issue : 2  |  Page : 174-177

Seroepidemiological survey of Crimean-Congo haemorrhagic fever among high-risk groups in the west of Iran

1 Department of Epidemiology and Biostatistics, Research Centre for Emerging and Re-emerging Infectious Diseases, Pasteur Institute of Iran, Tehran, Iran
2 Department of Arboviruses and Viral Hemorrhagic Fevers, Pasteur Institute of Iran, Tehran, Iran
3 Centers for Communicable Diseases Control, Deputy of Health, Kurdistan University of Medical Sciences, Sanandaj, Iran

Date of Submission24-Nov-2017
Date of Acceptance16-Oct-2018
Date of Web Publication31-Jul-2019

Correspondence Address:
Ehsan Mostafavi
Department of Epidemiology and Biostatistics, Research Centre for Emerging and Re-emerging Infectious Diseases, Pasteur Institute of Iran, Tehran
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0972-9062.263720

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Crimean-Congo haemorrhagic fever (CCHF) is a zoonotic viral haemorrhagic disease. This disease is more common in people who work with animals infected with CCHF virus. The aim of this study was to evaluate the CCHF exposure in high-risk occupational groups in Kurdistan Province in the west of Iran. This cross-sectional study was conducted in 2014 in three counties of Kurdistan Province, viz. Sanandaj, Marivan and Sarvabad. About 50 butchers and slaughterhouse workers, 50 hunters, 50 health care workers and 100 subjects referred to clinical laboratories were sampled and examined for the diagnosis of IgG antibodies against the CCHF using ELISA method. The serum sample of one of the butchers and slaughterhouse workers was positive for CCHF virus. No positive case was found in any other studied groups. The study findings indicate that although CCHF is an endemic disease in different parts of Iran, there is a low rate of seropositivity among high-risk occupations in the west of Iran. Therefore, it is not probably a serious public health problem in this area.

Keywords: Arbovirus; Bunyaviridae; CCHF; occupational disease; tick-borne disease

How to cite this article:
Shahbazi N, Firouz SK, Karimi M, Mostafavi E. Seroepidemiological survey of Crimean-Congo haemorrhagic fever among high-risk groups in the west of Iran. J Vector Borne Dis 2019;56:174-7

How to cite this URL:
Shahbazi N, Firouz SK, Karimi M, Mostafavi E. Seroepidemiological survey of Crimean-Congo haemorrhagic fever among high-risk groups in the west of Iran. J Vector Borne Dis [serial online] 2019 [cited 2020 Jul 6];56:174-7. Available from: http://www.jvbd.org/text.asp?2019/56/2/174/263720

Crimean-Congo haemorrhagic fever (CCHF) is a zoonotic viral haemorrhagic disease, prevalent in Asia, Africa, East Europe and the Middle East[1]. Crimean-Congo haemorrhagic fever virus (CCHFV) belongs to the genus Nairovirus under the Bunyaviridae family[2]. This fever is considered as an occupational disease, and its virus is transmitted by the bite of infected ticks or through direct contact with the infected blood and tissues of animals as well as nosocomial infections[3]. The clinical symptoms of the disease in human beings include, sudden onset of high fever, chills, headache, nausea, dizziness, diarrhoea, vomiting and internal or external bleeding[4]. Serological and molecular methods are used for the diagnosis of this disease[5]. Laboratory diagnosis of the suspected cases of the CCHF need special equipments and laboratories with high level of safety. Methods of diagnosis of infected cases include the 4-fold increase in the IgG antibody titre, detection of IgM antibody, polymerase chain reaction (PCR) or isolation of the virus. IgG and IgM antibodies in the serum can be detected from the Day 6 of the infection by the immunofluorescence (IF) and ELISA methods. IgM in the patients’ blood can be detected up to four months but the IgG is detectable for up to five years[6].

The CCHF is an endemic disease in some African, European and Asian countries, including Iran[7]. The disease occurs most frequently in the eastern parts of Asia, the Middle East, southern Russia, the Balkans and Africa[8].

This disease has been reported in the neighboring countries of Iran such as Turkey[9], Pakistan[10], Iraq[11], the United Arabic Emirates[12], Oman[13], Kuwait[14], and Saudi Arabia[15].

It was reported in Iran for the first time in 1970 among slaughterhouse cattle in Tehran[7]. Since then, various studies around the country have indicated the circulation of this disease in cattle[5]. In 1978, the CCHF virus was isolated from a tick in Ferdows City in the northeast of Iran[16]. The disease was neglected until 1999, when it was reported again in few human cases[5].

Though, the disease has been reported from almost every part of the country, human cases were reported mostly from Sistan-Baluchistan Province in eastern Iran[5]. From 1999 to 2016, as the physicians and the health care system became more sensitive to the disease, and a national laboratory with proper health care system was established in the country for the diagnosis of the disease; over 1000 cases of the disease were reported in the country, with highest confirmed positive cases observed in butchers and slaughterhouse workers followed by farmers[17]. Kurdistan Province has very low reporting of CCHF cases[17] in the country and until the time of this study, only two cases of the disease were reported in 2001 and 2002. Since, there is limited information on the epidemiology of the CCHF in Kurdistan Province, this study aimed to investigate high-risk groups of this province in terms of history of infection with the CCHF.

This cross-sectional study was conducted in 2014 in Kurdistan Province to monitor the area for zoonotic diseases with a focus on the southwestern cities of the province, viz. Sanandaj, Marivan and Sarvabad. The sample size for the study was calculated (n = 250) on the basis of an earlier study conducted in Iran wherein about 15% of the tested humans were seropositive[18] with the assumption of 4.5% precision and the 95% confidence level. The sera were collected from the peoples at high risk of CCHF infection (butchers and slaughterhouse workers, hunters and their families, the health care personnels) and patients admitted to the medical diagnostic laboratories (control group) after obtaining their consent.

The sampling was conducted by collection of 8 ml of the participants’ venous blood after obtaining the information on their demographic and background characteristics. The serum samples were sent to the Pasteur Institute of Iran, Tehran (national reference laboratory). The serum samples were tested to detect the presence of the IgG antibodies against the CCHF using ELISA method. The results of studies on tularemia, Q fever and brucellosis in these groups have been published in other journals[19],[20].

For ELISA test (IgG), the recombinant antigen expressed in the BSR (a clone of BHK) cells infected with Semliki Forest Suicide virus (SFV)-CCHFV, expressing nucleoproteins of the CCHFV in a variety of infections, was used. The wells were coated with diluted mouse hyper immune ascetic fluid in the PBS-1x and incubated overnight at 4 °C. After washing (with PBST) (PBS containing Tween), diluted antigen in PBST and skimmed milk (PBSTM) was added in the wells and incubated for 1 h at 37 °C. The plates were again rinsed with PBST. Washing was repeated in this step. In the next step, diluted perox-idase-labeled antihuman immunoglobulin (in PBSTM) was added and the ELISA plate was incubated for 1 h at 37 °C. Then, after washing with PBST, the plate was incubated for 15 min at room temperature with 3,3’, 5, 5’-Tetra- methylbenzidine (TMB) substrate. H2SO4 (4N) was used as stop solution. The ELISA plate was read by ELISA Reader (Anthos 2020; Biochrom Ltd., Cambridge, U.K.) at optical density (OD) of 450 nm. There were positive and negative control serums in each test[21],[22].

Of all the participants, 206 (82.4%) were males, while 44 participants (17.6%) were females. The participants’ (hunters, butchers, and health care personnel) median age and work experience were 39.5 and 10 yr, respectively. A total of 42% of the high-risk groups and 3% of the control group considered themselves to be at risk of infection with common diseases. About 42% of the total participants kept at least one domestic animal in their living place. Among those with high-risk occupations (hunters, health care personnel, butchers and slaughterhouse workers), 90% reported that they had a type of work in which the animals or human secretions were splashed on their face or body, 74.4% of them never disinfected their equipment and 78.8% never used disinfectants for their hands and face.

Out of the 250 serum samples, only one man (0.4%) had the anti-CCHF IgG. He was a 32-year-old butcher from the City of Marivan. As the only positive case belonged to the group of butchers and slaughterhouse workers, the seroprevalence of CCHF among this group was 2%.

In this study, most of the studied high-risk populations reported that they had a type of work in which the animals or human secretions were splashed on their face or body and they don’t disinfect their equipments, their hands and face; however, the serum sample of only one of the butchers was positive for the CCHF. Although, Kurdistan Province is one of the low-risk provinces in terms of the CCHF and new cases of the disease are being reported in this province since 2002; this study indicated that the virus causing CCHF may be still circulating throughout the province.

The largest occupational groups reported to be infected with the CCHF are butchers and slaughterhouse workers in various parts of Iran[23]. The rate of infection among the butchers of this study (2%) was lower than that reported in two similar studies in Iran. In a study conducted with the aim of determining the level of infection among the slaughterhouse workers in the northeastern Iran in 2004 and 2005, 14.8% of the 108 slaughterhouse workers included in the study showed anti-CCHF IgG[18]. In another study conducted in 2006 in Isfahan, the central of Iran, to determine the IgG antibody of CCHF among the butchers and slaughterhouse workers, 5% of the 80 people under the study showed positive serology[24]. The findings of the present study is to some extent in accordance with the findings of another study in Kurdistan province in wherein none of the 100 high risk individuals (20 slaughterhouses and 80 dairy farmers) showed positive results by serum indirect immunofluorescence[25].

In the present study, the positive serum case did not report any positive clinical history of the CCHF disease. However, in another study conducted to examine the sero-prevalence in terms of tularemia, Q-fever and brucellosis, the patient was reported positive in terms ofinfection with phase-I and phase-II of Q-fever[19],[20].

Considering the foregoing points, it is recommended that a broader and more comprehensive study should be conducted in order to monitor and assess the prevalence of the disease among other high-risk groups such as farmers, domestic animals and ticks of the province and the human population of other cities of the province.

The results of this study showed that the CCHF virus is circulating in the Kurdistan province, with low prevalence and the studied population is exposed to CCHF virus infection demanding more comprehensive studies in the future. Evaluating the knowledge, attitude and practice of at-risk populations regarding the disease and organizing training programs for them, running seroepidemiological studies with more sample size among the high-risk population, and the animal hosts and ticks are recommended to determine the real epidemiological feature of CCHF in this region and to provide the researchers and physicians as well as the health-care workers with better evidences of distribution of the disease.

Conflict of interest

The authors declare that they have no conflict of interest.

Ethical statement

The study was approved by the Ethical Committee of Pasteur Institute of Iran, Tehran (Code: IR.PII. REC.1395.9). The participants provided informed written consent for taking their blood samples.

  Acknowledgements Top

The authors appreciate the financial support of the Pasteur Institute of Iran and Center for Disease Control of the Iranian Ministry of Health and Medical Education (Grant No. 810). The authors also thank the staff of Kurdistan University of Medical Sciences, and Health Care Network in Sarvabad, Marivan and Sanandaj who supported during sampling in the study.

  References Top

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