Serosurvey of Crimean-Congo Hemorrhagic Fever Virus in Domestic Animals,Gujarat,India,2013

Abstract

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease that causes a fatal hemorrhagic illness in humans. This disease is asymptomatic in animals. CCHF was first confirmed in a nosocomial outbreak in 2011 in Gujarat State. Another notifiable outbreak occurred in July, 2013, in Karyana Village, Amreli district, Gujarat State. Anti-CCHF virus (CCHFV) immunoglobulin G (IgG) antibodies were detected in domestic animals from the adjoining villages of the affected area, indicating a considerable amount of positivity against domestic animals. The present serosurvey was carried out to determine the prevalence of CCHFV among bovine, sheep, and goat populations from 15 districts of Gujarat State, India. A total of 1226 serum samples from domestic animals were screened for IgG antibodies using a CCHF animal IgG enzyme-linked immunosorbent assay (ELISA) kit from the Centers for Disease Control and Prevention. Antibodies were detected in all the 15 districts surveyed; with positivity of 12.09%, 41.21%, and 33.62% in bovine, sheep, and goat respectively. This necessitates the surveillance of CCHFV IgG antibodies in animals and hemorrhagic fever cases in human.

Introduction

Crimean-Congo hemorrhagic fever (CCHF) is caused by CCHF virus (CCHFV) belonging to family Bunyaviridae. This disease can cause case fatality rates up to 80% in humans (Ergonul et al. 2007). Humans become infected by Hyalomma anatolicum tick bites; these ticks are usually found on cattle, buffalo, goat, sheep, or exposure to the blood or tissues of a viremic animal during slaughtering or allied procedures. However, the infections are typically asymptomatic and no clinical hemorrhagic disease appears (Burt et al. 1993). Domestic animals play a very important role in the epidemiology of the CCHF.

Earlier studies in India showed, 5.2% CCHFV seropositivity by a complement fixation test in 368 animal sera from Maharashtra, Kerala, Tamil Nadu, Mysore, and Pondicherry. A high seropositivity rate was reported for goats in southern India (Rodrigues et al. 1986).

Recently in 2010, CCHFV antibodies were detected among domestic animals in Gujarat and Rajasthan states, and subsequently during a nosocomial outbreak in 2011, CCHF was reported in Ahmadabad district, Gujarat State. Buffalo, cattle, sheep, and goat sera from affected and adjoining villages showed presence of immunoglobulin G (IgG) antibodies (Mourya et al. 2012). Investigations of another CCHF outbreak in 2013 in Karyana village, Amreli district, Gujarat State, also showed prevalence of anti-CCHFV IgG antibodies in domestic animals from affected and adjoining villages. Hyalomma ticks collected from animals in the house of index case were found to be positive (Yadav et al. 2014). CCHF-positive and fatal human cases were reported from Patan, Rajkot, Surendranagar, and Ahmadabad districts in Gujarat State (National Institute of Virology, unpublished data). Anti-CCHFV IgG antibodies were detected in livestock serum samples of Gujarat State (2010–2013) during different outbreaks (Yadav et al. 2013). This study was conducted to understand the emergence and spread of CCHF in new areas of Gujarat State.

Materials and Methods

All of the necessary approvals, i.e., Institutional Human Ethical Committee, Institutional Biosafety Committee and Animal Ethical Committee, were obtained before commencement of the work. Animal husbandry officials also had taken prior permissions from the owners of the animals for drawing samples.

Sample collection

A cross-sectional study was carried out in domestic animals (buffalo, cattle, sheep, and goat) to estimate the current situation of CCHFV seroprevalence. Random unbiased samples from domestic animals from 15 districts were collected (Table 1). A total of 160 tick samples were collected from the areas where confirmed human CCHF cases were recorded as well as other suspected areas, including Amreli, Kutch, Patan, Surendranagar, Bharuch, Jamnagar, Kheda, Narmada, Rajkot, Sabarkantha, Anand, Gandhinagar, Junagadh, Porbandar, Navsari, and Surat districts.

Table 1.

Screening of Domestic Animal Samples (Species Wise) for Anti-CCHFV IgG Antibodies and Tick Pool for CCHFV RNA

	Bovine samples positive/tested	Goat samples positive/Tested	Sheep samples positive/tested		CCHFV-positive tick/tick pool tested
Animal/tick pool samples received from Gujarat State	(IgG ELISA)			IgG positive/ tested samples	(Real-time RT-PCR)
Ahmadabad	11/51	10/38	2/6	23/95	1/17
Amreli	21/71	13/37	12/30	46/138	4/44
Kutch	12/61	11/24	4/20	27/105	0/8
Patan	9/80	Nil	Nil	9/80	0/7
Surendranagar	4/8	Nil	Nil	4/8	0/4
Banaskantha	0/40	6/20	0/20	6/80	Nil
Jamnagar	0/40	15/20	9/20	24/80	0/10
Kheda	0/40	3/20	3/20	6/80	0/17
Mehsana	18/80	Ni	Nil	18/80	Nil
Rajkot	6/40	7/20	3/20	16/80	0/11
Sabarkantha	2/40	2/20	1/20	5/80	0/10
Anand	1/40	4/20	0/20	5/80	0/7
Gandhinagar	0/40	4/20	3/20	7/80	0/2
Junagadh	0/40	20/20	20/20	40/80	0/13
Porbandar	2/40	20/20	20/20	42/80	0/10
Total	86/711	115/279	77/236	278/1226	5/160

CCHF, Crimean–Congo hemorrhagic fever; IgG, immunoglobulin G; CCHFV, CCHF virus; ELISA, enzyme-linked immunosorbent assay.

Screening of ticks and animal samples

After species identification, the ticks were screened for CCHFV RNA by real-time RT-PCR (Mourya et al. 2012). A total of 1226 animal serum samples were tested for anti-CCHFV IgG antibodies, using enzyme-linked immunosorbent assay (ELISA) kits provided by the Centers for Disease Control and Prevention (CDC; Atlanta, GA) (Mourya et al. 2012).

Results

Of the 160 pools of ticks, five pools of Hyalomma ticks were found positive from the Amreli and Ahmadabad districts (Table 1). Out of 1226 animal samples tested, 278 (22.67%) animals had IgG antibodies against CCHFV (Table 1). Antibody positivity was observed to be higher in sheep, followed by goat and bovine (41.21% >33.62% >12.09%), respectively. District-wise seropositivity recorded was as follows: Porbandar (52.5%)>Junagadh (50%)>Surendranagar (50%)>Amreli (33.82)>Jamnagar (30%)>Kutch (25.7%)>Ahmadabad (24.21%)>Mehsana (22.5%)>Rajkot (20%) and Patan (11.25%). Low seroprevalence was detected in Gandhinagar (8.75%)>Banaskantha (7.5%)>Kheda (7.5%)>Anand (6.25%) and Sabarkantha (6.25%), respectively.

Discussion

The livestock sector, particularly animal husbandry, is an important growth area of the Indian economy. Huge populations of livestock are in close contact with human beings (Department of Animal Husbandry Dairying & Fisheries, 18th Livestock Census 2007). Therefore, it is necessary to implement an enhanced CCHFV surveillance program to predict and respond to CCHF in the Gujarat State and probably elsewhere in India.

This study showed the highest anti-CCHFV IgG antibodies prevalence among sheep and goats as compared to bovines. Low prevalence of antibodies was recorded in domestic animals from Gandhinagar, while it was high in the Porabandar district. However, the data showed no direct correlation of human CCHF cases with seroprevalence in animals, similar to the case of ticks positivity in these areas. After the first outbreak in 2011, it was presumed that this infection was focal in this area; however, soon this outbreak was followed by another two epidemics in other areas and the present serosurvey revealed the presence of CCHF in different districts of Gujarat State. The overall prevalence of antibodies in all the 15 districts surveyed shows that this disease is endemic in Gujarat State. Domestic animals play an important role in the maintenance cycle and serve as hosts for both the virus and the tick vector. This data also emphasize that domestic animal trading could have a crucial role in the spread of this disease. Similar studies from Saudi Arabia and Iran have revealed the prevalence of CCHFV antibodies in domestic animals (Hassanein et al. 1997, Mostafavi et al. 2009).

This data will assist in providing information about the prevalence of the virus, risk assessment analysis, and formulating better control measures in the Gujarat State. This serosurvey also suggests the need for laboratory screening of all the suspected severe human hemorrhagic fever cases for CCHF. The random tick collection from different districts did not show any positivity. Data suggest that, instead of tick positivity, the seropositivity in the animals is a better indicator of presence of CCHFV in any area.

Conclusion

Surveillance of anti-CCHFV IgG antibodies in domestic animals would be better criteria to detect the presence of CCHF virus in any study area. It is imperative to screen all suspected human hemorrhagic fever cases for CCHFV. The spread of this disease in Gujarat State should be taken seriously from the public health point of view because it indicates the possible existence of this disease elsewhere in India.

Footnotes

Acknowledgments

We gratefully acknowledge the encouragement and support extended by Dr. V.M. Katoch, Secretary, Department of Health Research, and Director General, ICMR, New Delhi. We appreciate the cooperation of the Directorate of Health Services, Gujarat, Microbiology Department, PDU Medical College, Dr. V.S. Dhruwey (Integrated Disease Surveillance Programme), and Dr. K.P. Patel (Chief District Health Officer, Amreli). The authors gratefully acknowledge Dr. Stuart Nichol, Chief, Special Pathogens Branch, CDC, Atlanta, for providing the CCHF serology reagents.

Author Disclosure Statement

No conflicting financial interests exist.

Financial support was provided by the NIV, Pune, India.

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