Human mobility & vulnerability

Livestock rearing is an important livelihood activity in rural India . Several pastoral communities herd livestock under different production systems ranging from nomadic and semi nomadic to  transhumance.  Pastoralists comprise an estimated 5% of the country’s population .

Pastoralists and other livestock rearing communities mainly herd livestock using natural pastures to graze and sustain their animals. Some of these grazing areas lie close to forests or are within forests themselves .

The Dhangars are one such pastoral community who live in  the western state of Maharashtra in India . The Dhangars are divided into several sub groups but the best  known are the Hatkars who herd sheep and goat and the Dange or Gawli who herd cattle and buffalo. The Hatkar Dhangars practice nomadic pastoralism and migrate with their animals anywhere from 3 months to 9 months in a year with their families a few months to almost the entire year . These families  also keep a few horses to transport  their belongings , a few dogs for protecting their flocks  and some chicken for providing them eggs and meat while on migration .  Women and children travel with the flocks. While men herd sheep, women set up camp, fetch water, cook, clean , wash , sew , take care of young animals and chicken.

The Dange Dhangars live in the western Ghats close to the forests. In the past they kept buffalo as buffalos were less likely to be attacked by predators such as tigers. Today , in response to the changes they have begun to herd cattle and have settled in their home villages. They also practice some crop agriculture

In India over 200 ditribes engage in pastoralism, the tradition whereby households breed livestock, the majority for their own consumption, that graze from natural pasture. Pastoralists are estimated to comprise 6% of the country’s population and are divided into groups practicing horizontal movement patterns in the dryland regions and vertical movement patterns in the mountainous areas.

Long distance herding of cattle, sheep, goats and other livestock is not uncommon as grazing pastures becomes scarcer through the year and can extend for up to 9 months of the year. Pastoralist routes based on seasonal exploitation of vegetation are often dependent on forested areas for grazing. These forest habitats are a significant source of zoonotic diseases (that spreading from animals to humans).

For pastoralist communities dependent on forests for grazing livestock, passing through these regions comes with the increased risk of being exposed to zoonotic pathogens. Three neglected zoonotic diseases, Leptospirosis, Kyasanur forest Disease and Scrub Typhus, widespread across the Western Ghats forest communities cause severe complications and death if left untreated.

Although we understand zoonotic diseases are increasing globally, we still lack knowledge on how these diseases circulate between wildlife, livestock and people as they use forests, and how environmental changes like forest degradation interact with human migration routes.

This WP investigates whether human mobility increases exposure to or offers resilience against

zoonotic diseases by quantifying infection rates and diversity of zoonotic diseases in relation to human movement, host diversity and disease history.

Human populations moving across different scales will be sampled, including two nomadic pastoralist groups (Kouruba, Karnataka and Dhangars, Maharashtra) whose seasonal migration routes pass through forested areas with high prevalence of focal diseases (Fig. 1), one group migrating along un-forested routes, and farmers resident in forests (see WP3).

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Figure 1 Co-location of Western Ghats forest, recent KFD outbreaks and pastoralists migration routes across south Indian States.

Ecological and molecular methods will quantify pathogen strain diversity across a range of hosts and spatial scales to determine whether pathogen strains are shared between hosts (including humans) and vector species and to infer hosts and vector roles in human transmission.

Specifically, we intend to test the hypotheses that :

1. humans migrating longer distances with livestock have higher pathogen infection rates and strain diversity due to exposure to broader host ranges and habitats;
2. strain diversity is higher in districts with a long history of human cases versus sites where cases emerged recently.

We will examine movement patterns between groups, including frequency, seasonal timing, speed, scale and geographical routes, interface with habitat, populations and movements of key wildlife hosts and vectors (see WP3). Oral histories and photo-elicitation methods will explore drivers of mobility, cultural and health factors and traditional interventions of pastoralists. We will also record tick burdens, wildlife host and habitat availability along migration and grazing routes.

In sites, at the start, end and mid-point of the routes during disease risk, wildlife hosts will be sampled for blood and ecto-parasites.  We will determine the presence of KFDV, Orientia and Leptospira infections in vectors and hosts using DNA and RNA based assays. Using further molecular assays we will investigate levels of genetic variation, ie strain diversity, in Scrub Typus and Leptospira positive samples. Models will identify whether strain diversity is best explained by disease history, or host or vector strain diversity associated with migration or local site factors.

Better understanding of disease risk to pastoralists from vectors and wildlife or domestic animal hosts and how migration routes impact on this risk is crucially important so that disease prevention and management strategies can be refined and developed. Our research will feed into guidelines for pastoralists on disease risk and health-care access and into future surveillance regimes.