Kyasanur Forest disease
Kyasanur forest disease | |
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Other names | Monkey disease, monkey fever |
Infectious disease |
Kyasanur forest disease (KFD) is a
Signs and symptoms
The symptoms of the disease include a high fever with frontal headaches, chills, severe muscle pain, vomiting, and other gastrointestinal symptoms. Bleeding problems may occur 3–4 days after initial symptom onset. Patients may experience abnormally low blood pressure, and low platelet, red blood cell, and white blood cell count. After 1–2 weeks of symptoms, some patients recover without complication. However, the illness is biphasic for a subset of patients (10-20%) who experience a second wave of symptoms at the beginning of the third week. These symptoms include fever and signs of neurological manifestations, such as severe headache, mental disturbances, tremors, and vision deficits.[2][3][4] The convalescent period is typically very long, lasting several months. Muscle aches and weakness also occur during this period, and the patient is unable to engage in physical activities.
Cause
Virology
Kyasanur Forest disease virus | |
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Flavivirus structure and genome | |
Virus classification | |
(unranked): | Virus |
Realm: | Riboviria |
Kingdom: | Orthornavirae |
Phylum: | Kitrinoviricota |
Class: | Flasuviricetes |
Order: | Amarillovirales |
Family: | Flaviviridae |
Genus: | Flavivirus |
Species: | Kyasanur Forest disease virus
|
Synonyms[5] | |
Kyasanur Forest virus |
The KFD virus is a typical flavivirus measuring about 40-60 nm in diameter. The
Transmission
A variety of animals are thought to be
Pathology
The pathogenesis of KFDV is not completely understood. Research using mice models found that KFDV primarily replicated in the brain.[11] Other research has expanded on this by described neurological changes that occurred within infected organisms. This experiment was completed by using KFDV-infected mice and discovered that KFDV caused gliosis, inflammation, and cell death in the brain. They posited that KFDV could be primarily a neuropathic disease and other symptoms are due to this pathogenesis.[12]
Diagnosis
In earlier days suspected case were confirmed in a laboratory by serum inoculation into suckling mice (Swiss Albino mice) and subsequent death of mice was leveled as KFD Positive case. Other methods of diagnosis included hemagglutination inhibition (HI),
Prevention and treatment
Prevention is by vaccination, as well as preventive measures such as protective clothing and tick population control. The vaccine for KFDV consists of formalin-inactivated KFDV. The vaccine has a 62.4% effectiveness rate for individuals who receive two doses. For individuals who receive an additional dose, the effectiveness increases to 82.9%.[15] Specific antiviral treatments are not available as of 2022.[16]
Risk factors and risk groups
The spill-over of Kyasanur forest disease happens at the crossroads of the animal-human interaction, especially villages adjoining forest areas and inter-state borders.[17] People who frequently visit the forest areas of the Western Ghats region such as forest guards and officials, range forest officer (RFO), forest watchers, shepherds, firewood collectors, dry leaf collectors, hunters, people who handle dead animal carcasses, travelers who camp in the forest areas, tribal communities living inside the forest areas (Jenu kurubas and Betta kurubas), cashew nut workers especially those who engage in cleaning the dry leaves before the harvest season (seen in Pali and Mauxi outbreaks, North Goa), and areca nut farm workers working in infected tick areas will have a high risk of acquiring KFD infection. People who live in the KFD endemic areas and refuse to take KFD vaccination are at risk in contracting the infection.
History
The disease was first reported from Kattinakere village forest which is in the Kyasanur forest range of
Subsequent studies based on sequencing found that the Alkhurma virus found in Saudi Arabia is closely related.[23] In 1989 a patient in Nanjianin, China was found with fever symptoms and in 2009 its viral gene sequence was found to exactly match with that of the KFD reference virus of 1957. This has been questioned, though, since the Indian virus shows variations in sequence over time and the exact match with the virus sequence of 1957 and the Chinese virus of 1989 is not expected. This study also found using immune response tests that birds and humans in the region appeared to have been exposed to the virus.[24] Another study has suggested that the virus is recent in origin dating the nearest common ancestor of it and related viruses to around 1942, based on the estimated rate of sequence substitutions. The study also raises the possibility of bird involvement in long-distance transfer.[25] It appears that these viruses diverged 700 years ago.[26]
A recent outbreak in 2020, claimed two lives in Siddapura, Karnataka. The peak season for this disease in Malnad is from March till May but has been observed to peak earlier in the year as well. There were a total of 55 reported cases in Shivamogga district, Karntaka.[27][28]
Affected states in India
The disease initially reported from Shimoga district of Karnataka which is a primitive sylvan territory in Western Ghats of India. The disease spread out to other districts of Karnataka involving districts of Chikkamagalore, Uttara Kannada, Dakshina Kannada, Udupi, Chamarajanagar (2012), Belagavi (2016). In 2013, KFDV was detected in monkey autopsies from Nilgiris district of Tamil Nadu state. Monkey deaths and human cases have now been reported from three neighbouring states bordering Karnataka, i.e., Wayanad (2013) and Malappuram districts of Kerala (2014), North Goa district of Goa state (2015), and Sindhudurg district of Maharashtra (2016).[29]
Serological evidence for KFD
There are reported serological evidence for KFD detected in humans in other parts of India, namely Kutch and Saurashtra regions of Gujarat state, Kingaon and Parbatpur of West Bengal state.[30] A seroprevalence study in Andaman and Nicobar islands in 2002 revealed a high prevalence of hemagglutination inhibition (HI) antibodies against KFDV.[31]
Epidemiology
The disease has a fatality rate of 3-10%, and it affects 400-500 people annually.[10][14]
The disease was first noted at Kyasanur village near Sagar in Shivamogga district of Karnataka. The virus has been detected in monkeys in parts of Bandipur National Park (Chamarajnagar) and parts of the Nilgiris. Human infection occurred in Bandipur through handling of dead monkeys that were infected. A human carrier was also detected in Wayanad (Kerala).[32] The disease has shown its presence in the adjacent states of Karnataka including Kerala, Maharashtra, Goa, Tamil Nadu and Gujarat.[33][34][35]
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