Clinical, epidemiological, and molecular investigation of Kyasanur forest disease from Karnataka state, India during 2018-2019

Abstract

Background

In this study, we carried out an investigation of Kyasanur Forest Disease (KFD) suspected human cases reported in Karnataka state, India from December 2018 to June 2019.

Methods

The clinical samples of KFD suspected cases (n = 1955) from 14 districts of Karnataka were tested for KFD using real-time RT-PCR and IgM ELISA. Further, the KFD-negative samples were tested for IgM antibodies against dengue and chikungunya viruses. Monkey samples (n = 276) and tick pools (n = 11582) were also screened using real-time RT-PCR. KFD-positive samples were further analysed using next-generation sequencing along with clinico-epidemiological analysis.

Results

Of all, 173 (8.8%) cases tested positive for KFD either by real-time RT-PCR (n = 124), IgM ELISA (n = 53) or both tests (n = 4) from seven districts. Among KFD-negative cases, IgM antibody positivity was observed for dengue (2.6%), chikungunya (5.8%), dengue and chikungunya coinfection (3.7%). KFD cases peaked in January 2019 with fever, conjunctivitis, and myalgia as the predominant symptoms and a mortality of 4.6%. Among confirmed cases, 41% received a single dose and 20% received two doses of the KFD vaccine. Of the seven districts with KFDV positivity, Shivamogga and Hassan districts reported KFD viral RNA positivity in humans, monkeys, and ticks. Sequencing analysis of 2019 cases demonstrated a difference of less than 1.5% amino acid compared to prototype KFDV.

Conclusion

Although the KFD has been endemic in many districts of Karnataka state, our study confirms the presence of KFDV for the first time in two new districts, i.e. Hassan and Mysore. A comparative analysis of KFDV infection among the KFD-vaccinated and non-vaccinated populations demonstrated an insignificant difference.

Keywords:

• Kyasanur Forest disease
• Karnataka
• human cases
• monkey necropsies
• tick pools
• vaccine

Acknowledgement

Authors gratefully acknowledge the encouragement and support extended by Director, ICMR-NIV, Pune. We thank the staff of Maximum Containment Facility, ICMR-NIV, Pune including Mrs. Triparna Majumdar, Mrs. Ashwini Waghmare, Ms. Kaumudi Kalele and Mr. Yash Joshi for providing excellent technical support.

Ethical approval

The study was reviewed and approved by the Institutional Human Ethical Committee, Indian Council of Medical Research-National Institute of Virology (ICMR-NIV), Pune (NIV/IEC/2017/D-43). Informed consent was obtained from KFD suspected cases before the collection of clinical samples.

Consent for publication

Written informed consent was obtained from the patient for the use of the clinical details in the study.

Authors’ contributions

AM and PDY contributed to study design, data analysis, interpretation and writing and critical review. AM, AMS, RRS, KSK, DYP, SM, RJ, SP, DPS, MMJ contributed to data collection, interpretation, writing and critical review. AM, PDY, AMS, DYP, RRS, SM contributed to the critical review and finalisation of the paper.

Disclosure statement

There are no competing of interest exists among authors.

Data availability statement

All the patient data are included in the manuscript. The sequence details are available at NCBI public domain.

Additional information

Funding

The intramural grant was provided from ICMR-National Institute of Virology, Pune, India for conducting this study [MCL1805].