Kyanasur Forest Virus Prevention Tips

If you are travelling to southern regions of India, you may be at risk of contracting Kyasanur Forest Virus Disease. This disease is endemic to certain regions of southern India and has a mortality rate of 3 – 10%.¹

Prevention is the key to managing the virus. Read on to discover how best to prevent transmission in endemic areas.

Introduction

Brief overview of kyasanur forest virus (KFV)

Kyasanur Forest Disease (KFD) is caused by the Kyasanur Forest Disease Virus (KFDV). KFD is a viral haemorrhagic fever, transmitted to humans via tick bites.

KFDV, the virus which causes the disease, is endemic to Karnataka, a region in southern India. In 2012, it was estimated that the annual incidence of KFD was around 400 – 500 cases.² However, the disease and its epidemiology are largely understudied. There are also reports of individuals contracting the disease in other provinces of India, such as Gujarat, West Bengal, Tamil Nadu, Maharashtra, Andaman, and the Nicobar Islands.

KFD is characterised by a haemorrhagic fever. Viral haemorrhagic fevers are a condition affecting many different organs, often causing harm to the cardiovascular system. The disease has a reported mortality rate of approximately 3 – 10%.¹

There is no specific treatment for KFD, although a vaccine currently exists for KFDV. Treatment is largely supportive.

Importance of prevention in reducing risk

Understanding kyasanur forest virus

What is KFD?

Kyanasur Forest Disease was first reported in the Shimoga district of Karnataka, India. In 1957 it was documented that an outbreak of severe disease was affecting both people and wild, nonhuman primates living near the Kyasanur forest. Samples taken from affected animals were analysed and used to identify the disease-causing agent, which was subsequently named Kyanasur Forest Disease Virus (KFDV).

KFDV is a type of flavivirus, i.e. a member of the Flaviviridae virus family. These viruses are enveloped RNA viruses found in arthropods, often mosquitoes and ticks. Other examples of flaviviruses include dengue, West Nile Virus, and Zika Virus. Since flaviviruses use RNA as their genetic material, they can mutate at a higher rate than other viruses, adapting quickly to new conditions. Although this means that RNA viruses are a common cause of disease, flaviviruses are also covered in a lipoprotein outer layer, which can be easily destroyed using both physical and chemical methods.

Transmission and spread

Humans contract KFDV from tick bites. Hard ticks (Haemaphysalis spinigera) are the tick species acting as the vector for KFDV transmission.

H. spinigera is a forest tick, which can become infected with the virus and transmit it to humans.  Ticks become infected by coming into contact with animals infected by the virus – in the case of KFD, small mammals such as rats, porcupines, squirrels, mice, and shrews can act as host organisms for the virus, forming disease reservoirs.

Several species of monkeys can also become infected with the virus, such as the surili (Presbytis entellus) and the bonnet macaque (Macaca radiata). Being highly susceptible to the virus, monkeys develop excessive viremia (presence of viruses in the blood) and are referred to as ‘amplifying hosts’ for KFDV, infecting many ticks.

Humans are a terminal host for KFDV. This means that human individuals cannot transmit KFDV to other individuals.

Diagnosis and identification

At present, there are no specific tests for KFDV.

Individuals who are hospitalised for haemorrhagic fever can be formally diagnosed using rRT-PCR (real-time, reverse transcriptase polymerase chain reaction) assays.

This technique involves using reverse transcriptase enzymes to convert single-stranded RNA molecules from clinical samples into double-stranded DNA molecules, followed by amplification (i.e. copying) of DNA using PCR. These DNA samples can then be analysed to detect the presence of viral material. This assay is also used to detect other viruses such as COVID-19, Ebola and Zika viruses.

Identification of KFDV is usually based on serological evidence, i.e. the identification of viral material or antibodies in the serum component of affected individuals’ blood.

Symptoms and effects on health

The initial symptoms of KFVD include:

• High fever
• Severe myalgia (muscle aches and pains)
• Frontal headache (i.e. pain in the forehead/temples)
• Prostration (i.e. extreme physical exhaustion)
• Vomiting
• Diarrhea

KFDV is a haemorrhagic fever virus, meaning it is part of a group of viruses that can cause internal and external bleeding, organ failure, brain inflammation, and ultimately death. Further progression of the disease can cause more severe symptoms, including bleeding from the nasal cavity, throat, gum tissue (gingivae), and sometimes the gastrointestinal tract.

KFD has a mortality rate of approximately 3 – 10% in humans.¹

Prevention tips

Avoiding tick bites

Because forest ticks are the vector of transmission of KFDV, avoiding tick bites is crucial to preventing infection with KFDV.

Ticks are small and light, so you may not sense if a tick has landed on you. They also have a painless bite.

Always be aware if you are travelling to an area where ticks are common, and be especially aware of areas where ticks may be carrying a disease-causing agent such as KFDV.

Here are some tips to help you prevent coming into contact with forest ticks:

• Wear protective clothing (long sleeves, pants)

Protective clothing, which is sturdy and tightly woven, can prevent direct contact with ticks and prevent tick bites. Tuck your trousers into your socks or boots, so that ticks cannot come into contact with your skin.

• Use insect repellents containing DEET or picaridin

There are several effective tick repellents used to prevent contact with ticks. DEET (N, N-diethyl-meta-toluamide) and permethrin are two examples of effective repellents.

In addition to application on the skin, it can also be effective to treat clothes (such as socks and trouser legs) with a permethrin-containing insecticide. Be conscious of the duration for which repellents are effective, and reapply accordingly. Always read and follow the instructions on insect repellents.

In addition to treating clothes, it can also be effective to use permethrin to treat boots and camping gear. It is possible to buy equipment and clothes which have been treated with 0.5% permethrin.

The Environmental Protection Agency (EPA) also recommends other insect repellents such as picaridin, IR3535, para-menthane-diol (PMD), 2-undecanone, and oil of lemon eucalyptus (OLE). Make sure you use a repellent which suits your needs and your environment.

• Conduct thorough tick checks after outdoor activities

Use a mirror to help you conduct a full-body check for ticks after venturing to areas where ticks reside.

Reducing exposure to infected animals

• Avoid contact with sick or dead animals, especially monkeys

Humans can contract KFDV by interacting with diseased or dead animals which are infected with KFDV, such as monkeys.

• Report any sightings of sick or dead animals to authorities

In addition to avoiding dead animals, that may be infected with KDFV, be sure to report sightings of animals/carcasses that may be infected to a local health authority. Reporting sightings can help institutions and health authorities keep track of the transmission of the virus and aid virus prevention schemes.

Vaccination

Vaccination is the most effective prevention measure for KFVD. The vaccine for KFVD is produced and supplied by the Institute of Animal Health and Veterinary Biologicals (IAH and VB) Bengaluru. The vaccine is a 0.1% formalin-inactivated tissue culture vaccine.

The immunity conferred by the vaccine is short-lived. The standard vaccination regime comprises two vaccine doses administered at an interval of one month. It is recommended for individuals ages 7 – 65 years old.

The effectiveness of the vaccine has been reported to be 62% among those with two doses, and 83% for those who have received a booster dose³.

Vaccines have effectively reduced the intensity of the disease and its fatality.

Side effects of the vaccine include swelling and irritation of the injection site. This is due to the formalin contained in the vaccine. The vaccine is sometimes refused for this reason by individuals in endemic regions.

Conclusion

KFD in some cases can be extremely severe, ultimately resulting in death. There are no specific treatments for the disease, meaning it is extremely important to be aware of transmission vectors.

Where possible, vaccines should be sought to reduce the likelihood of infection and severe disease. In addition to vaccination, preventing contact with ticks and infected animals is key to preventing disease transmission.

Recap of key prevention tips

To avoid contracting KFD:

• Get vaccinated, with booster doses if possible
• Cover up skin with tightly woven, full-length clothes
• Apply effective insect repellents, to the skin as well as clothes and other gear
• Avoid contact with animals that may be infected

Be proactive about prevention and always research whether you may be travelling to an endemic area.