ABSTRACT
Background & objectives: In India, Kyasanur Forest Disease has been reported from the states of Karnataka, Kerala, Goa, and Maharashtra. The relationship between climatic factors and transmission of KFD remains untouched, therefore, the present study was undertaken. Methods: Based on the occurrence of cases, Shivamogga district (Karnataka) and Wayanad district in Kerala and northern Goa (Goa state) were selected for the study. Data on the incidence of KFD and climate factors were collected from concerned authorities. To determine the relationship between dependent and independent variables, spearman’s correlation was calculated for monthly as well as with lag months. Results: KFD cases and temperature (°C) were found significantly correlated up to 1 months’ lag period (p<0.05) while with precipitation relationship was found negatively significant for 0-3 months’ lag. The range of suitable temperature for KFD in Shivamogga, Goa and Wayanad was found as 20-31°C, 25-29°C and 27-31°C respectively. The cumulative precipitation during transmission months (November–May) ranged from <150-500mm, while in non-transmission months (June-October) from >1100-2400mm. Interpretation & conclusion: The analysis of three sites revealed that with the increase in temperature, the intensity of KFD transmission decreases as corroborated by the seasonal fluctuations in Shivamogga, Goa and Wayanad. High precipitation from June to October rovides suitable ecology to tick vector and sets in transmission season from November to May when cumulative precipitation is <500 mm.
ABSTRACT
Background & objectives: Kyasanur forest disease (KFD) is an infectious disease discovered in Karnataka State of India in 1957; since then, the State has been known to be enzootic for KFD. In the last few years, its presence was observed in the adjoining five States of the Western Ghats of India. The present study was conducted to understand the kinetics of viral RNA, immunoglobulin M (IgM) and IgG antibody in KFD-infected humans for developing a diagnostic algorithm for KFD. Methods: A prospective follow up study was performed among KFD patients in Sindhudurg district of Maharashtra State, India. A total of 1046 suspected patients were tested, and 72 KFD patients were enrolled and followed for 17 months (January 2016 to May 2017). Serum samples of KFD patients were screened for viral RNA, and IgM and IgG antibodies. Results: KFD viral positivity was observed from 1st to 18th post-onset day (POD). Positivity of anti-KFD virus (KFDV) IgM antibodies was detected from 4th till 122nd POD and anti-KFDV IgG antibodies detected from 5th till 474th POD. A prediction probability was determined from statistical analysis using the generalized additive model in R-software to support the laboratory findings regarding viral kinetics. Interpretation & conclusions: This study demonstrated the presence of KFD viral RNA till 18th POD, IgM antibodies till 122nd POD and IgG till the last sample collected. Based on our study an algorithm was recommended for accurate laboratory diagnosis of KFDV infection. A sample collected between 1 and 3 POD can be tested using KFDV real-time reverse transcriptase polymerase chain reaction (RT-PCR); between 4 and 24 POD, the combination of real-time RT-PCR and anti-KFDV IgM enzyme-linked immunosorbent assay (ELISA) tests can be used; between POD 25 and 132, anti-KFDV IgM and IgG ELISA are recommended.
ABSTRACT
Kyasanur forest disease (KFD) is a known viral haemorrhagic fever in India, for the last 60 years. However, in recent years, the change in epidemiological profile of the disease has suggested that it is now time to consider KFD as an emerging tropical disease in India. The preference should be to educate not only the villagers where it is being reported or detected but also to public health experts, veterinarians, forest officials and medical professionals to pay attention while seeing a patient overlapping with endemic diseases such as Japanese encephalitis, West Nile, dengue, chikungunya, malaria and tuberculosis. Although the existence of KFD is known for a long time, updated understanding of its clinical profile in humans is still limited. This article describes in detail the clinical presentation of KFD reported till date. It also highlights geographical distribution of the disease, risk factors for virus transmission, biochemical/haematological findings and control measures. There is an urgent need for research on KFD, particularly for understanding biphasic nature of illness, development of cost-effective diagnostic tools, utility of non-invasive samples for diagnosis and development of new vaccines.
ABSTRACT
Background & objectives: Kyasanur Forest disease (KFD) is a febrile illness characterized by haemorrhages and caused by KFD virus (KFDV), which belongs to the Flaviviridae family. It is reported to be an endemic disease in Shimoga district of Karnataka State, India, especially in forested and adjoining areas. Several outbreaks have been reported in newer areas, which raised queries regarding the changing nature of structural proteins if any. The objective of the study was to investigate amino acid composition and antigenic variability if any, among the envelope glycoprotein (E-proteins) from old and new strains of KFDV. Methods: Bioinformatic tools and techniques were used to predict B-cell epitopes and three-dimensional structures and to compare envelope glycoprotein (E-proteins) between the old strains of KFDV and those from emerging outbreaks till 2015. Results: The strain from recent outbreak in Thirthahalli, Karnataka State (2014), was similar to the older strain of KFDV (99.2%). Although mutations existed in strains from 2015 in Kerala KFD sequences, these did not alter the epitopes. Interpretation & conclusions: The study revealed that though mutations existed, there were no drastic changes in the structure or antigenicity of the E-proteins from recent outbreaks. Hence, no correlation could be established between the mutations and detection in new geographical areas. It seems that KFDV must be present earlier also in many States and due to availability of testing system and alertness coming into notice now.
ABSTRACT
Ticks are distributed worldwide and can harbour and transmit a range of pathogenic microorganisms that affect livestock and humans. Most tick-borne diseases are caused by tick-borne viruses. Two major tick-borne virus zoonotic diseases, Kyasanur forest disease (KFD) and Crimean–Congo haemorrhagic fever (CCHF), are notifiable in India and are associated with high mortality rates. KFD virus was first identified in 1957 in Karnataka state; the tick Haemaphysalis spinigera is the main vector. During 2012–2013, cases were reported from previously unaffected areas in Karnataka, and newer areas of Kerala and Tamil Nadu states. These reports may be the result of improved active surveillance or may reflect altered virus transmission because of environmental change. CCHF is distributed in Asia, Africa and some part of Europe; Hyalomma spp. ticks are the main vectors. The existence of CCHF in India was first confirmed in 2011 in Gujarat state. In 2013, a non-nosocomial CCHF outbreak in Amreli district, as well as positive tick, animal and human samples in various areas of Gujarat state, suggested that the virus is widespread in Gujarat state, India. The emergence of KFD and CCHF in various Indian states emphasizes the need for nationwide surveillance among animals and humans. There is a need for improved diagnostic facilities, more containment laboratories, better public awareness, and implementation of thorough tick control in affected areas during epidemics.