Monkey Fever

Monkey fever is a zoonotic disease, which means it gets transmitted from animals-to-humans. Transmission mainly occurs through coming in direct contact with an infected or dead animal or by the bite of a tick that introduces the virus into the human body. Human-to-human transmission has not been reported so far. (3)

Cattle, small rodents like rats and mice, and birds also carry this virus after being infected by a tick, though they don’t play a major role in transmitting this disease to humans and any occurrence, if noted, is rare. Nonetheless, these animals form a major part of the lifecycle of the Kyasanur forest disease virus and are responsible for transferring it to more ticks.

Though cow, goats, and sheep may carry this virus, there have been no reports of the disease through unpasteurised milk.

It is important to note that not all kind of ticks spread this disease but the hard tick Haemophysalis is responsible for carrying and transmitting this disease. These ticks feed on the blood of birds, reptiles and mammals and are commonly found on forest floors.

These ticks infect monkeys while feeding on them. As these monkeys die of the disease the ticks leave their bodies and keep spreading to new hosts, continuing the cycle.(2)(4)

Monkey fever symptoms appear within 3-8 days of being infected by the virus. The initial symptoms include high fever and chills along with muscle pain and headache. The fever may go as high as 104℉ and may last up to 2 weeks.  

Other symptoms of monkey fever include:

• Diarrhoea
• Nausea and vomiting
• Tender muscles
• Photophobia (discomfort or pain in the eyes due to light exposure, not fear or phobia of light)
• Low blood pressure
• Reduced platelet count (Read more: Normal platelet count)
• Low level of white blood cells (WBCs)
• Inflammation in the eye

Haemorrhagic symptoms appear after 3-4 days of the appearance of the fever. It is usually associated with nosebleeds and bleeding from gums. Intestinal bleeding may also occur, which is apparent in the form of bloody stools.

Papulovesicular lesions may develop in the soft palate, which may manifest as fluid-filled sacs (called vesicles) in the roof of the oral cavity

Some people may also experience respiratory discomforts like a cough and blood in sputum; however, this condition resolves itself after a while.

Swelling in the cervical, axillary and epitrochlear lymph nodes is yet another symptom of this disease.

In most cases, the recovery is complete and symptoms disappear within a week or two.

However, general weakness, muscle twitching, and coarse tremors may be experienced during the recovery period. The affected individual may also experience itching, numbing or chilling sensations in the skin.

In about 10-20 % of the patients, the disease may relapse. The febrile phase, in this case, could be associated with some neurological symptoms which include drowsiness, mental disturbances, confusion, loss of consciousness and in a rare few cases, meningoencephalitis. However, the evidence of the latter is not as apparent.

Severe cases are only noted if the disease is left untreated or in case of excessive haemorrhage. The mortality rate of the disease range from 2 to 10 % and is mainly high in areas which lack proper health facilities or awareness.

Older and immunocompromised people are also at a higher risk of mortality. (5)

Prevention of Monkey Fever mainly comprises of eradicating the vector and proper surveillance for infected animals and humans to avoid an outbreak. Various government and non-governmental organisations actively work in the affected areas to keep the disease at bay. Major preventive measures for monkey fever include:

• Identifying infected monkeys in the disease-prone areas and testing for human transmission in case a dead monkey is found in any such area. This is the responsibility of the Forest Department and the Veterinary Department.
• Regular check-ups are done in the endemic areas. Immediate medical care and treatment is provided in case a human case is found. If you are visiting tick infected areas or forests, it is advisable to wear clothes that cover your neck, arms and body. Tick repellents should also be used as an extra preventive measure.
• Monitoring of the high-risk areas and forests around it for tick population. Forest floors are usually sprayed with chemicals such as DEET and DMP oil to keep the tick population in check.

Other preventive measures include injecting cattle with ivermectin in the months of September and October to prevent tick infestation and educating people about the disease, preventive measures and vaccination schedules. (6)

Vaccination

KFD vaccination was introduced by the government in the year 1990 and since then it is regularly done within a 5 Km radius of the disease-prone area. The vaccine comprises formalin attenuated tissue culture of the KFD virus.

The vaccine is usually administered in two doses within a span of a month and needs a booster dose within 6 to 9 months. The latter increases the efficiency of vaccination from about 62.4% to about 82.9% and is hence important to assure prevention.

Booster doses are further required annually, for about five years. (7)

Diagnosis usually includes ruling out the chances of tick bites and travel to a forest or areas prone by this disease. Lab tests are prescribed depending on the presence or absence of any of the above factors.

KFD is considered to be highly infectious and has been put in the category of biosafety level 4 (the most contagious or highest risk level). It used to be diagnosed by the isolation of the virus from the serum of the patient and serological tests including Haemagglutination, Neutralisation test, Complement fixation test.

Though, PCR and ELIZA are now used to identify KFD virus from blood or serum samples. Cerebrospinal fluid samples are sometimes used in place of blood to isolate the virus and recently, RNA of KFD virus has been isolated from the urine samples of an initial phase patient in Pune. (8)

These techniques are much more sensitive (accurate) and help in the differentiating the disease from other types of haemorrhagic fevers like dengue and malaria.

Currently, there is no specific treatment or medicine for Kyasanur Forest disease. Supportive therapy is used to provide relief from symptoms, and usually comprises of hospitalisation and proper care. This includes maintaining fluid balance in the patient to avoid dehydration, and blood transfusion if needed. (9)