Zoonotic diseases are diseases transmitted between animals (domestic and wild) and humans. It is known that as much as 60 per cent of human infectious diseases are zoonotic.
Zoonotic diseases with potential for pandemics like Avian influenza, SARs, and now COVID-19, have drawn massive global attention due to their novel emergence and wide global impact. This means that there are many more zoonotic diseases than the ones which hit the world as pandemics.
Although the other lesser-known endemic diseases affect and debilitate human society in geographical areas where they occur, not all have received the spotlight as they should have. India is reported to have an increasing burden of zoonotic diseases, some known and addressed through National Programs as priorities, while others still waiting to be better understood and addressed.
Mountain regions like the Darjeeling-Sikkim Himalaya perfectly fits into the environment, which facilitates higher probabilities of zoonotic diseases emergence and re-emergence.
High biodiversity (especially mammals and birds), high density of livestock and human population are projected predictors of zoonotic disease hotspots. These predictors likely characterise rural agrarian settings, where humans-wild and domestic animals are higher, thereby facilitating zoonotic diseases to emerge, and re-emerge.
Usually, these settings are also coupled with disadvantaged socioeconomic populations, with limited health services and infrastructure, leading the human population to be victims to a vicious cycle of diseases and poverty.
Mountain regions like the Darjeeling-Sikkim Himalaya perfectly fits into the environment, which facilitates higher probabilities of zoonotic diseases emergence and re-emergence. The landscape is a biodiversity hotspot with a large number of mammal species, predominantly agrarian, and like other mountain areas in India, has crowded urban spaces and a rising human population. The landscape is also a tourist destination.
Travel to and from the landscape presents a risk of amplifying and spreading zoonotic diseases. Darjeeling-Sikkim Himalaya has reported zoonotic diseases like Leishmaniosis, Rickettsia diseases, Dengue, malaria, Nipah virus, Encephalitis etc.
Leishmaniosis (visceral and dermal) and Rickettsial diseases like scrub typhus and others, feature as priority diseases for intervention in the Darjeeling-Sikkim Himalaya. Leishmaniosis was first reported in Darjeeling in 1995, and the district is now a Leishmaniosis endemic district.
Despite active surveillance of the disease under its national control program, there still is underreporting and low registration in the national database. This leaves pockets of disease impacted and a debilitated population, particularly in the lowlands, something which requires interventions like targeted support to the ongoing surveillance and interventions by the national program.
Rickettsial diseases such as the scrub typhus are endemic re-emerging zoonotic diseases with occasional outbreaks. Darjeeling Sikkim Himalaya reported outbreaks of the scrub typhus in the early 2000s with a rise in disease, thereafter. The Rickettsial diseases currently rank as low priority and are not covered by a national program. Cursory investigations show that people have always borne the burden of diseases.
The reported cases are an underestimate as there are very few studies at the community level. Also, the chances of Rickettsial diseases going undetected is high due to a lack of surveillance and clinical presentations and confusion with other infections. The knowledge gaps in epidemiological understanding of vector-human interface, in case of the Rickettsial disease, is very high. The disease is an occupational disease, mostly prevalent in rural farmers. Endemic diseases like the scrub typhus and their spread to other areas could be aggravated by climate change is a concern according to a local medical officer in Sikkim. Why do we need a false prescription from doctor for COVID-19 test?
Scrub typhus is increasingly being reported from tea plantations of Darjeeling, after the first report of the disease in 2,000 in Ambiok tea plantation. The tea plantation population is one of the most poverty-ridden in the landscape, with low access to health and social welfare. An added burden of zoonotic diseases will hugely compromise their well-being.
The COVID-19 pandemic has starkly shown that outbreaks and spread of zoonotic diseases is not only a health security risk, but can regress human civilisation by disrupting normal social life, economy, education, livelihoods, and rob people of basic dignity. The current scenario of zoonotic diseases in Darjeeling Sikkim Himalaya could be a reflection of situations in other parts of the Indian mountain region, also. Thus there is an urgent need to work on the neglected zoonotic diseases in the Darjeeling-Sikkim Himalaya and other parts of the region.
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(The author Sunita Pradhan, is currently working at ATREE, Regional Office-Northeast India, Gangtok, Sikkim)