Mourya et al. BMC Infectious Diseases (2019) 19:104 https://doi.org/10.1186/s12879-019-3740-x RESEARCH ARTICLE Open Access Crimean Congo hemorrhagic fever serosurvey in humans for identifying high- risk populations and high-risk areas in the endemic state of Gujarat, India Devendra T. Mourya1*, Pragya D. Yadav1, Yogesh K. Gurav1, Prachi G. Pardeshi1, Anita M. Shete1, Rajlaxmi Jain1, Dinkar D. Raval2, Kamlesh J. Upadhyay3 and Deepak Y. Patil1 Abstract Background: Crimean Congo Hemorrhagic Fever (CCHF) is a highly infectious zoonotic disease of humans transmitted by Hyalomma ticks. Earlier studies have shown CCHF seroprevalence in livestock throughout India, yet sporadic outbreaks have been recorded mostly from the Gujarat state of India since 2011. Occupational vulnerability to CCHF for animal handlers, veterinarians, abattoir workers, and healthcare workers has been documented. The current study was planned to determine the seroprevalence of CCHF with an intention to identify the high -risk population and high -risk areas from Gujarat state, India. Methods: Based on the socio-clinical data, the human population of Gujarat was divided into eight categories viz. A: CCHF affected person/house/close contact, B: Neighborhood contacts, C: Animal handlers, D: General population, E: Farmers, F: Abattoir workers, G: Veterinarian, H: Healthcare workers. A total of 4978 human serum samples were collected from 33 districts of Gujarat during year 2015, 2016 and 2017. All the samples were screened for the presence of anti-CCHFV IgG using indigenously developed anti-CCHFV IgG ELISA. Univariate regression analysis was performed to recognize significant risk factors for CCHF seropositivity. Results: Twenty-five serum samples were found to be positive with an overall CCHF human seropositivity of 0.5% (95% CI 0.30–0.74%). Gender predisposition to CCHF prevalence was observed in males (OR: 2.80; p-value: 0.020). The risk for seropositivity increased sevenfold when a person was in contact or neighbor with a CCHF case (OR 7.02; p-value: < 0.0001). No significant difference in seropositivity was observed within different age groups. Veterinarians, healthcare workers, and control group were found to be seronegative for CCHF. Conclusions: In-spite of CCHF sporadic outbreaks reported in Gujarat, the seropositivity for CCHF in the state was low as compared to other endemic countries. Males, close contacts and neighbors were identified as a high-risk population for CCHF infection. To recognize the high-risk area, tick screening and animal serosurvey would be a wiser choice. The study also suggests circulation and under diagnoses of CCHFV in the naïve regions of Gujarat. Keywords: Crimean Congo hemorrhagic fever, Gujarat, Human, Serosurvey, ELISA, Ticks, Risk factors * Correspondence: [email protected]; [email protected] 1ICMR-National Institute of Virology, 20-A, Dr. Ambedkar Road, Pune, Maharashtra Pin 411001, India Full list of author information is available at the end of the article © The Author(s). 2019 Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. Mourya et al. BMC Infectious Diseases (2019) 19:104 Page 2 of 8 Background Dwarka, Banaskantha, Bharuch, Bhavnagar, Dahod, Crimean Congo hemorrhagic fever (CCHF) is a Gir-Somnath, Junagadh, Mahisagar, Narmada, Navsari, tick-borne zoonotic disease caused by CCHF virus Sabarakantha, Surat, Tapi, Vadodara, Chhota Udepur, (CCHFV) belonging to family Nairoviridae, genus Porbandar, Gandhinagar and Dang districts of Gujarat Orthonairovirus [1]. This virus is known to cause case State. fatality rate of up to 80% in humans [2, 3]. The disease The transmission of CCHF infection to humans through is prevalent in Africa, Asia, Southeast Europe and the contact with CCHFV infected individuals, animals and Middle East [3, 4]. CCHFV infection is highly infectious bite of ticks is well known. Since 2011, many sporadic with a high rate of human-to-human transmission. Do- CCHF cases were reported from Gujarat State making it mestic animals and Hyalomma ticks play an essential an endemic state for CCHF [7, 9]. Based on available rec- role in the amplification of virus and transmission to ord history, individual CCHF survivors were identified, human. Nosocomial infection, bite of infected ticks, crush- and their households were traced. The categories were ing ticks with bare hands and contact with the blood of in- designed based on socio-clinical data of the subject and fected animals/ humans tissue fluids are the major routes the occupational risk to CCHF infection. Study population of transmission of CCHF to humans. Available informa- belonging to Gujarat State was categorized as Category tion suggests that CCHF cases mainly occur as a result of A: CCHF affected person/CCHF affected house/caretaker occupational exposure among abattoir workers, farmers, of the patient, close contacts, person involved in transpor- veterinarians, and healthcare workers [5]. tation of CCHF cases to hospital; Category B: All the India reported its first CCHF case in the year 2011 family members (except children aged ≤5 yrs.) of neigh- from Ahmedabad, Gujarat [6]. Since then, several spor- borhood (i.e. within 50–100 m of the radius of confirmed adic cases and outbreaks of CCHF have been reported CCHF case house; Category C: Animal handlers (person mostly from Gujarat and few from Rajasthan and Uttar living in close contact with livestock, persons grazing the Pradesh States of India [7, 8]. Over some time, the livestock) Category D: General population (low-risk majority of CCHF cases have been published from vari- group); Category E: Farmers; Category F: Abattoir ous districts of Gujarat thus making Gujarat an endemic Worker; Category G: Veterinarians; Category H: Health- state for CCHF disease in India. Though serological care workers. Samples of pregnant women and critically ill evidence against CCHF in humans has been reported in patients were not collected. Stratified purposive sampling India [9, 10], a systematic data on CCHF seroprevalence was planned from Category A and B category, and is lacking. CCHF IgG seropositivity of 5.4% in cattle and random sampling was done from categories C, D, E, 10.99% in sheep and goats from most of the states of F, G and H.. India has been recorded earlier without any remarkable difference between Gujarat and the other states thus indicating the prevalence of this virus throughout the Sample collection and processing country [11]. India has well-organized animal husbandry, The Institutional Human Ethics Committee of and a larger rural population depends for their livelihood ICMR-NIV, Pune (IHEC No, NIV/IEC/2017/37/42) ap- by maintaining livestock. Despite the countrywide proved the study. Informed written consent was obtained presence of the vector species and domestic reservoir from all the subjects and parent/guardian in case of a animals, CCHF human cases and human outbreaks have child (< 18 yrs) subjects from the study population. Blood been reported predominantly only from one state in sample (3–5 mL) was collected from the study population India, i.e., Gujarat. Intending to understand CCHF sero- in clot activator tube and transported to ICMR-NIV, Pune prevalence and to identify high-risk populations and in a cold chain. After the receipt of the samples at NIV, high-risk areas in Gujarat, the present cross-sectional each sample was checked for its quality and condition. serosurvey was undertaken in the human community. Serum was separated from the blood sample of each subject and further aliquoted as 50 μL, 250 μL, stock and Methods stored at − 20 °C until further use. Each sample was Study design registered in laboratory information management system The study area, period and characteristic of study software by giving a unique identification number/ population anonymous code. A demographic and socio-clinical detail All the 33 districts of Gujarat were considered as a site for of every subject was also recorded. The complete process sample collection from the human population during the of sampling from the transportation of specimen to the year 2015, 2016 and 2017. Human serum samples were laboratory investigations was done with utmost precaution, collected from Ahmedabad, Amreli, Patan, Aravalli, Kheda, which includes; collection of samples by trained personnel Morbi, Kutch, Surendranagar, Mahesana, Jamnagar, using personal protective equipment (apron, mask, and Botad, Valsad, Anand, Rajkot, Panchmahal, Devbhoomi gloves) in a leak-proof container and transportation by Mourya et al. BMC Infectious Diseases (2019) 19:104 Page 3 of 8 maintaining cold chain conditions. Aliquoting and testing analysis using Epi-info 7 (7.2.1.0, CDC, Atlanta, GA, USA) of samples were carried out in a BSL-2 facility. and MedCalc Software bvba, version 18 (1993–2018). For plotting state of Gujarat map, the svg file was downloaded Development of indigenous anti-CCHF human IgG ELISA, its from https://commons.wikimedia.org/wiki/File:India_Gu- validation and screening of human serum samples jarat_location_map.svg and edited as required. The human serum samples were tested for the presence of anti-CCHFV IgG antibodies using in-house developed Results CCHF Human IgG ELISA as defined below. Micro-well The study area, period and characteristic of study plates were coated with Gamma-inactivated CCHFV in- population fected Vero CCL81 cell lysate antigen strain number Sample collection was done from 91 villages of 33 NIV11704 (Rows A-D) and uninfected Vero CCL81 cell districts of Gujarat throughout 3 years (2015, 2016 and lysate (Rows E-H) at 1:20 dilution in carbonate buffer (pH 2017).