Tick-borne monkey fever strikes again

  • Kyasanur forest disease or monkey fever strikes monkeys and humans bitten by virus-infected ticks.
  • The disease has spread through the Western Ghats and with increased awareness, more instances have come to light.
  • Detected in 1957 from Karnataka, it was officially reported in Maharashtra only in 2016. But scientists have now found evidence of previous episodes in the state’s rural population.

Kyasanur forest disease (KFD) is a tick-borne illness that was once restricted to the southern Indian state of Karnataka. It was first detected in the 1950s from Karnataka’s Shivamogga district, in the forest of Kyasanur, after which it is named. Back then the local community, noticing that monkeys were dying and making humans sick (whoever came in close contact with the sick monkeys), dubbed it the ‘monkey fever.’ But monkeys themselves, like humans, are hosts; the actual causative agent of KFD is a virus carried by ticks.

KFD rears its ugly head post-monsoon when young ticks, called nymphs, actively look for warm-blooded animals to attach to and feed on. With the bite of an infected tick, the virus gets into the bloodstream of humans, causing fevers, headaches, bleeding and, in some cases, death.

Over the past decade, KFD has been reported from the states of Maharashtra, Goa, Kerala and Tamil Nadu – outside its original range in Karnataka. In Maharashtra, it was first documented in 2016.

Now, a team of researchers from the National Institute of Virology, Pune, have investigated the 2016 KFD outbreak in Maharashtra and found that it may not have been the first episode of KFD for the state.

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Bonnet monkey. Photo by Raju Kasambe / Wikimedia Commons.

First, the researchers estimated the KFD prevalence in Dodamarg cluster of villages at Sindhudurg district in Maharashtra. Using data from house-to-house surveys conducted by health workers and patient records from hospitals in the district, they shortlisted 488 individuals whose symptoms matched with that of the disease.

They further screened these individuals and confirmed 130 to be KFD-positive. Three of the 130 patients died. A vaccine against KFD is available but none of the patients had received it.

Vocation, living conditions linked to tick exposure

When researchers looked at the possible reasons for the patients’ exposure to ticks, they learnt that vocation and living conditions had a major role to play. About 93 percent of the KFD-infected patients had visited the forest in Dodamarg before coming down with the disease. They had ventured into the forests to work in cashew, betel nut or coconut farms, to collect firewood or to graze their cattle, and likely got bitten by ticks there.

According to the 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.”

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Kyasanuru village on Google Maps.

Incidentally, Dodamarg borders Goa, where KFD struck in 2015, and Karnataka, where it continues to prevail. Its forests are also home to the red-faced bonnet monkey (Macaca radiata) and black-faced langur (Semnopithecus entellus) – species that are susceptible to monkey fever. “It is possible that the monkeys carry and spread ticks around when they move from one forest of the Western Ghats to another,” said researcher Pragya Yadav.

Monkeys do not play a direct role in the transmission of KFD, which is not aerosol-generated, Yadav clarified, but they do act as hosts. After a monkey dies from infection, the ticks drop off and scramble to find new hosts, which could be humans. “When they find a warm-blooded animal, they run like crazy creatures because they want to suck its blood.”

Sick of ticks before

Yadav and colleagues checked blood samples for antibodies against the virus in KFD-affected villages of Dodamarg. Overall, 9.7 percent of the individuals had antiviral antibodies in their blood. A study of healthy, uninfected individuals in KFD-unaffected villages 15 km away, surprisingly, showed a similar prevalence of antibodies.

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Black-faced monkeys in the Western Ghats. Photo by Jrimman / Wikimedia Commons.

The antibodies persist for at least two years after a tick bite, according to Yadav. This means that the two areas had been exposed to the virus before and 2016 was not the first time that Maharashtra had had a KFD outbreak. The previous cases probably went undetected, Yadav says, indicating that many people got tick bites, recovered and were doing fine.

Yadav’s analysis of the 2016 outbreak was published online earlier this year. New cases of KFD continue to emerge everyday from the region as we near the middle of the peak season. Not only this, the virus seems to be spreading geographically as well. During 2016–17, Yadav says, already many villages of Sindhudurg were affected but now it’s being detected in more villages.

CITATION:
Gurav, Y.K., et al. (2018). Kyasanur Forest Disease Prevalence in Western Ghats Proven and Confirmed by Recent Outbreak in Maharashtra, India, 2016. Vector-Borne and Zoonotic Diseases. https://doi.org/10.1089/vbz.2017.2129.

(I wrote this piece originally for Mongabay-India.)

Monkeys eat—and then floss

Monkeys living on an island have learned to use a startling variety of tools and techniques to obtain the juicy innards of different foods – and to floss their teeth afterwards.

The Nicobar long-tailed macaque is only found on three islands in the eastern Indian Ocean. One of them is Great Nicobar Island. Many of the macaques’ favoured foods are thorny, slimy, hairy or mucky. To get rid of these inedible coatings, the macaques either wash the foods in puddles or wrap them in leaves and rub them clean.

The macaques eat coconuts too, plucking them from the tree by twisting them around or using their teeth to cut them off. If it is tender, the macaques de-husk the coconut using their teeth. (As someone who’s tried husking a coconut at home, it takes some knife skills 🙂 but these monkeys do it with their teeth!)

After eating, macaques clean their teeth – they were seen holding a fine fibre between their teeth and pulling at it. The macaques used a range of materials as dental floss: a tree needle, a bird feather, a blade of grass, a coconut fibre, a nylon thread and a metal wire. (I wondered if the need to floss comes from all that coconut husk getting stuck in the teeth, but no). They did so after eating various foods in different habitats, the researchers told me.

If you enjoyed this excerpt, read the rest of the story published in New Scientist here.

Monkey mom eats mummified baby

Evalyne9bisPrimates are known both to grieve their loved ones and practice cannibalism, but for the first time, scientists have recorded a Tonkean macaque eating her dead baby.

Researchers studying macaques at the Parco Faunistico di Piano dell’Abatino animal sanctuary observed a new mother named Evalyne “caring” for her deceased infant for weeks, and then consuming its mummified body until nothing but a single bone remained.

Tonkean macaques—which are native to Southeast Asia—tote around their babies’ corpses for hours or, even days. It could be a manifestation of grief, or an absence of understanding that the offspring is dead.

“This kind of behavior has been documented in chimpanzees and a few other primates, with mothers carrying their dead infant until it disintegrates,” notes Frans de Waal, a primatologist at Emory University who was not involved in the new research.

To read more, go to National Geographic news.

Photo credit: Arianna De Marco.