Ecological Drivers of KFD

Pashu Sandesh, 7 February 2019

Diksha P. Gourkhede*, Ramkumar N. Rupner, Pratik R. Wankhade

KFDV, the Kyasanur forest disease virus was first isolated during an outbreak of febrile disease in 1957 in people living in the Kyasanur forest area of Shimoga district in the Karnataka (Earlier Mysore) state of India.

Emergence of KFDV breaking state boundaries???

It is noticeablethat in recent years KFDV has broken the geographical boundaries and spread out to newer areas which are often separated by several kilometres from the endemic regions. Initially, the disease was endemic to only five districts of Karnataka, however, it has now spread to Chamarajanagar district and Bandipur national park of Karnataka State and also reached to the other adjoining five states of India. Recent outbreaks in the non-endemic zones, it can be envisaged that KFDV is conquering new area in the Western Ghats and have increased its importance as a human pathogen.

Map showing the KFD endemic regions in Karnataka State and recently emergent areas from the states of Kerala, Tamil Nadu, Goa and Maharashtra along the Western Ghats. (Ajesh et al., 2016)

What is leading to emergence of KFD??

• Human interference: According to Indian Council of Medical Research (ICMR), “clearing of forest area for cultivation causes changes in tick fauna and is considered as an important risk factor for outbreaks.” As a greater number of people encroaching into forests for working in cashew farms, to collect firewood or to graze their livestock, they are more likely to get exposed to virus-infected ticks.
• Deforestation and climate change: Forest ecosystem of the world is threatened by conversion of agricultural development, timber extraction, road development, etc. In Down to earth by giving an example they linked monkey fever in Goa to deforestation, climate change. Goa’s landscape is changing rapidly due to urbanization and industrial activities at the cost of destroying prime forest areas. Illegal mining activity is a long-standing concern in the state. This explains why each year, KFD affects people from communities that live along or inside the forests. Temperature increase, according to experts, has widened habitats of insects that transit diseases to people.
• Macro and microclimate of vectors: Removal of trees resulted in the rapid occupation of shrubs especially Chromolaena odorata and Lantana camara that provided conducive environment for small mammals and birds especially rodents, which in turn served as hosts for growing larvae and nymphs. The microclimate under the leaves and within bushes plays an important role for the vector ticks.

Is KFD Crossed National Barrier??

Mainly there are two variants of KFDV have been reported. In China the Nanjianyin virus showed close genetic similarity with the Indian KFD strains and Alkhurma hemorrhagic fever virus (AHFV) a variant or subgroup virus, has been reported in Saudi Arabia. There is a common ancestry between KFDVs in India and Saudi Arabia, despite their large geographic separation, indicating a wide movement of the virus, possibly carried by birds.

Is there any human to human transmission??

According to many studies there is no person-to-person transmission and the transmission is most likely occurring due to tick bites, at various times, among the tribal community that lives in the affected forest. The disease has been known for more than six decades, but no hospital has ever reported any nosocomial KFD infections or cases, which occurred between close human contacts. States such as Kerala, Tamil Nadu, and Goa reported cases occurring in areas surrounding the forest where there is a wide spread presence of the Haemaphysalis tick. In these areas, close contact with animals that graze in the affected forest might transport the infected ticks to villages and thus increase the probability of tick bites to their inhabitants.

What to do next??

The spread of KFDV to newer areas is most probably due to the movement of monkeys and small rodents, which harbour the virus. Conducting sero-surveys in different districts of the region would help in the mapping of the disease. A study on abundance and distribution of Haemaphysalis spp is required to know the host suitability and vegetation biology. More research is needed to understand the driving factors for emergence of KFD to newer areas. The authority should start campaigns to spread awareness among the local people regarding the disease, its hazardous effects, preventive vaccination programs.

References 

Ajesh, K., Nagaraja, B.K. and Sreejith, K., 2017. Kyasanur forest disease virus breaking the endemic barrier: An investigation into ecological effects on disease emergence and future outlook. Zoonoses and public health, 64(7), pp. e73-e80.

Murhekar, M.V., Kasabi, G.S., Mehendale, S.M., Mourya, D.T., Yadav, P.D. and Tandale, B.V., 2015. On the transmission pattern of Kyasanur Forest disease (KFD) in India. Infectious diseases of poverty, 4(1), p.37.

Pattnaik, P., 2006. Kyasanur forest disease: an epidemiological view in India. Reviews in medical virology, 16(3), pp.151-165.

Shah, S.Z., Basit Jabbar, N.A., Rehman, A., Nasir, H., Nadeem, S., Jabbar, I., ur Rahman, Z. and Azam, S., 2018. Epidemiology, Pathogenesis, and Control of a Tick-Borne Disease-Kyasanur Forest Disease: Current Status and Future Directions. Frontiers in cellular and infection microbiology, 8.

Diksha P. Gourkhede*, Ramkumar N. Rupner, Pratik R. Wankhade

ICAR-Indian Veterinary Research Institute, Izatnagar-243 122, Bareilly

 *Corresponding author: - dikshagourkhede311@gmail.com