The rise of zoonotic viral and bacterial disease deaths in Kerala

Zoonotic viral and bacterial diseases are increasingly affecting Kerala, with their occurrence going up over the years. K.S. Sudhi speaks to experts, to find out why

September 21, 2023 07:40 pm | Updated September 25, 2023 12:45 pm IST

A fruit bat or grey headed flying fox.

A fruit bat or grey headed flying fox. | Photo Credit: CraigRJD

On September 5, S. Rajani, a homemaker from Perunad in Kerala’s Pathanamthitta district visited Laha, a nearby tribal settlement, along with her husband and son. They were carrying about 100 packets of freshly cooked rice and vegetable curry carefully packed in plantain leaves and wrapped in newspapers.

The meals were for less privileged children living in dilapidated homes. When they received the packets, their smiles made memories come rushing to Rajani. She thought of her daughter Abhiramai, who would’ve turned 13 this year, and her eyes welled up.

Watch | All about zoonotic diseases

The day marked the child’s first death anniversary. Abhirami sustained a stray dog bite when she was fetching milk from a home nearby. She succumbed to rabies, one of 27 people who died in 2022. A year on, Rajani’s pain has not abated. Loud dog barks send shivers down her spine, drowning her in the agonising memories of her daughter’s painful end.

Kerala is becoming increasingly susceptible to zoonotic diseases, which leave a trail of familial economic and health impacts. Outbreaks occur mostly in villages abutting forested regions.

The Thrissur Corporation will soon embark on a mission to conduct a census of street dogs.

The Thrissur Corporation will soon embark on a mission to conduct a census of street dogs. | Photo Credit: K.K. Najeeb

Leptospirosis continues to be the killer zoonotic disease in the State, with 290 deaths in 2022, followed by scrub typhus, which claimed 24 lives last year. The deaths due to rabies also paint a grim picture. While five people succumbed to the viral infection in 2020, the death toll recorded an over 100% increase in 2021, with 11 cases. Last year, 27 rabies deaths were reported, according to the data on communicable disease available with the State Surveillance Unit of the Directorate of Health Services, Kerala.

Most recently, Nipah, the deadly zoonotic viral disease, made its fourth date with the State since 2018 and claimed two lives. The resurfacing of the disease, believed to be spread by bats, the reservoir of the pathogen, caused widespread panic among people in Kozhikode district, from where the deaths were reported. It also threw life out of gear for a large number of people, who were forced to stay indoors after the authorities notified their localities as containment zones.

Young pigs

Young pigs

Those such as Babu Kunnath, who came into direct contact with the dead or infected, are forced to stay in quarantine for 21 days, the incubation period of the Nipah virus. “My exposure to the disease happened when I took Mangalatt Harris, a native of Vadakara in Kozhikode, who later died of the disease, to a hospital after he complained of severe headache and high fever,” he says. Kunnath was working as a carpenter in Harris’s house.

Harris was admitted to an isolation ward of a hospital after testing positive for the disease, but succumbed to the virus a few days later, says Kunnath, who is in quarantine at home along with Harris’s two brothers. Their friends and relatives leave food and water outside their rooms.

The disease surveillance efforts undertaken in Kozhikode district following the outbreak of the disease witnessed 1,286 people on the contact list, including 276 in the high-risk category. Six of the 267 body fluid samples from people who showed some signs of the disease had tested positive, indicating the potential for the spread of the disease. However, the containment efforts proved fruitful as none tested positive later.

Less heard of

Medical experts say leptospirosis comes second after rabies among zoonotic diseases in Kerala in terms of spread. Though considered seasonal earlier, the disease is now being diagnosed during the non-rainy season too. While leptospirosis claimed 48 lives in 2020, it nearly doubled in 2021 with 95 deaths, and it jumped by over 305% in 2022. The State health authorities have identified leptospirosis hotspots in almost all districts in Kerala.

Around 80,000 birds, mostly ducks, were dead/culled in the last bout of avian flu which was first detected at Vazhuthanam in Alappuzha in October 2022.

Around 80,000 birds, mostly ducks, were dead/culled in the last bout of avian flu which was first detected at Vazhuthanam in Alappuzha in October 2022. | Photo Credit: Suresh Alleppey

Leptospirosis is a bacterial disease that is commonly spread to humans from rodents, says S. Nandakumar, Disease Investigation Officer, State Institute for Animal Diseases, Thiruvananthapuram, Kerala’s State capital.

Brucellosis, a bacterial disease infecting farm animals and dogs; scrub typhus, a bacterium from mites; and Kyasanur Forest Disease caused by a virus named after the forest, are the other zoonoses that have made their presence known in the State over the past few years. A host of factors contribute to the spread of zoonotic diseases, including the increased number of migrations within India, from far-flung areas, says Dr. Nandakumar, a veterinarian, who is part of a national team investigating the outbreak of Nipah.

Though Kerala shares its political boundaries with only two States, Tamil Nadu and Karnataka, there are 18 animal entry check-posts in six districts through which a large number of cattle are brought in. Palakkad district alone has seven check-posts. The strengthening of check-posts by posting veterinary doctors and point-of-care testing methods can prevent the entry of diseases to the State, he says.

Lakshmi Balachandran, a second-year student at a medical college on the outskirts of Thiruvananthapuram, came home from her hostel a few months ago with a running fever. Her fever, which dropped on taking an antipyretic tablet, returned as the effect of the drug waned away. “A haematological analysis confirmed my doubts,” says her mother, U. Anuja, who is the State coordinator of the Prevention of Infectious and Epidemic Diseases Cell.

Lakshmi tested positive for leptospirosis. Though people working in fields and outdoors are generally considered vulnerable to this zoonotic disease, a walk along water-logged roads could become medically significant for anyone, say health experts.

Also read | One Health strategy key to checking zoonotic diseases: expert

Mosquito menace

Climate change, says Dr. Anuja, plays an important role in the spread of vector-borne diseases. The ideal temperature for breeding of mosquitoes is between 15 and 30 ° C. If the atmospheric temperature of a place, which was earlier unsuitable for mosquitoes, turns favourable due to global warming and associated weather changes, the pathogen and the vector will grow there. This will lead to the spread of such diseases in new areas, explains Dr. Anuja, who is also the Head of the Community Medicine Department of the Government Medical College Hospital, Thiruvananthapuram.

Pathogens of zoonotic diseases exist in the natural ecosystem. Any stress in the ecosystem or people entering wild habitats for agro-forestry purposes could trigger or even bring diseases to human habitations. Pressure on bats, for instance, could increase the chance of shredding of pathogens, explains Dr. Anuja, on the Nipah outbreak.

Invasions hurt

K.V. Sankaran, one of the coordinating lead authors of the global assessment of invasive alien species by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Service (IPBES), highlights the reports linking invasions of species alien to an area with zoonoses. Established alien species can contribute to zoonosis by increasing the abundance of already existing pathogens and by introducing new pathogens, he says.

There are now increasing reports linking invasive rats to the emergence of plague, murine typhus, scrub typhus, and leptospirosis throughout the world. The IPBES report notes that malaria, Zika, and West Nile fever are known to be spread by invasive alien mosquitoes. There is also evidence that invasion by alien mosquito species exacerbated the spread of yellow fever, chikungunya, and dengue fever across the globe, he notes.

Invasive plants too are responsible for the spread of human diseases. The dense invasive shrub Lantana camara in East Africa provided a new habitat for the tsetse fly, the carrier of Trypanosoma parasites which cause sleeping sickness in human beings.

Quoting publications on zoonotic diseases, he says that since a majority of such diseases originate from wildlife, as evident from the outbreaks of Coronavirus 2 (SARS-CoV-2), Nipah, and chikungunya, caution should be exercised while translocating wild animals as it may lead to a change in pathogen ecology and distribution. Also, pet trade and aquaculture may provide more opportunities for contact between alien hosts and humans, he cautions.

Future tense

A.P.M. Mohammed Hanish, Principal Secretary, Health and Family Welfare, Kerala, feels that the State should create an edifice of research, development, and diagnostic facilities to handle emerging health situations such as Nipah. The services of the Kerala unit of the National Institute of Virology, Alappuzha, and the Indian Council for Medical Research will now be used for strengthening the diagnostics and medical research infrastructure of the State. The State government has initiated plans in this direction, says Hanish.

“The State Forest Department and the Department of Animal Husbandry shall jointly undertake research projects on various aspects of zoonotic diseases. We need to identify the causative factors of the outbreak and the mode of transmission of the disease. A deep understanding of these is necessary as the risks can only be abated and not eliminated,” he suggests.

Besides the health impact caused by zoonotic diseases, rabies cases caused by street dogs have also brought additional financial burden on the exchequer by way of the commitment to provide compensation to the victims in Kerala.

Come September 28, Rajani and her husband will travel to Kochi to present her compensation claim for the death of her daughter before the Supreme Court-appointed Justice Siri Jagan committee, which recommends compensation to street dog-bite victims. The committee has been hamstrung due to the paucity of funds.

Though the committee has asked her to be present at its Kochi office on September 28 to consider her application, those on the panel are unsure when the victims will get the compensation. A large number of claims, cleared by the committee earlier, are awaiting payment. The lack of financial support from the government has hamstrung even the functioning of the panel, say panel sources.

For Rajani, or any parent, no money can compensate for the loss suffered following the death of their child. A year after the tragic incident, the family is yet to overcome the grief and shock caused by the zoonosis. Leaving his job in Kuwait, her husband returned to their hometown to rebuild their lives.

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