An outbreak of Kyasanur forest disease in the Wayanad and Malappuram districts of Kerala, India

Kyasanur forest disease (KFD) is a zoonotic viral haemorrhagic fever and has been endemic to Karnataka State, India. Outbreaks of KFD were reported in new areas of Wayanad and Malappuram districts of Kerala, India during 2014-2015. Investigation of the outbreaks was carried out in these districts during May 2015. The line-list data of KFD cases available with District Medical Office, Wayanad were analysed. Case investigation was carried out to determine the risk factors associated with the outbreak and possible site of contraction infections. Ticks from the forest floor were collected in areas associated with monkey deaths by flagging method to estimate species abundance. Of 102 confirmed cases of KFD reported in Wayanad, 91% were adults aged >15years. About 43% of the cases were from the areas of Poothady Primary Health Centre (PHC) followed by Chethalayam PHC (22%). Most of the affected individuals belong to Kattunayakan tribe, dependent on forest for their livelihood. Those tribes are engaged in trench digging and fire line works in summer months and hence are at a higher risk. In Malappuram, the Cholanaickan tribe, are under high risk of exposure to infected ticks as they live deep in the forest and trap monkeys for game meat. High abundance of Haemaphysalis spinigera and H. turturis, the established vectors of KFD virus was recorded in all affected areas. Incidence of KFD cases/monkey deaths and high abundance of Haemaphysalis vectors in the forest ranges of Wayanad and Malappuram districts indicate that the area has become receptive for KFD outbreaks. Preventive measures (vaccination of high risk groups) coupled with intensive health education should be carried out prior to transmission season.