Dry environments cause disease to spread more quickly

Animals that live in dry and sometimes barren landscapes rely on watering holes where everyone from massive elephants and hippos to gazelles and antelope goes to drink.

For some animals, watering holes are not just a place get hydrated, but they can also be prime hunting spots because of how many other animals congregate in one place.

Now, a new study found that these conditions can increase the spread of disease, and sick animals in dry landscapes behave differently from species in other less water deprived environments.

The study was conducted by researchers from the German Leibniz Institute for Zoo and Wildlife Research, and published in the journal British Ecological Society journal Functional Ecology.

When an animal is sick, it typically causes lethargy and isolation, where the individual sleeps more and eats less. Because of this lethargy, the animal doesn’t come in as much contact with healthy animals and so the disease doesn’t become widespread.

However, in dry environments where water is scarce, diseases could have the opposite effect in individuals and actually, cause sickness to spread.

“For this purpose, we simulated a population of virtual animals living in dry landscapes in which they regularly visit a single waterhole for drinking,” said Mathias Franz, a member of the research team. We observed that sick individuals, who we assumed to be more lethargic, stayed closer to the waterhole. Because healthy individuals also visit the waterhole regularly, we found that lethargy leads to an increase in encounters between sick and healthy individuals.”

Unlike in areas with ample sources of water, dry environments drive the spread of disease because sick individuals have more contact with healthy individuals.

The results are important not just for estimating the spread and evolution of pathogens in areas with limited drinking water, but also for assessing how droughts and water shortages caused by climate change could trigger diseases to spread and cause declines in animal populations.

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By Kay Vandette, Earth.com Staff Writer