Sick animals limit disease transmission by isolating themselves from their peers

Date: August 22, 2016

Source: University of Zurich

When animals get sick, they may change their behaviour, becoming less active, for example. The study's lead author, Patricia Lopes from the Department of Evolutionary Biology and Environmental Studies at the University of Zurich, says that previous research in wild animals has generally ignored how this change in behaviour may affect social contacts in a group and how, in turn, these changes can impact the transmission of a disease.

Sick mice are not avoided, but remove themselves from the group

To tackle this problem, Patricia Lopes and her colleagues used a novel combination of experimental manipulations of free-living mice, radio frequency tracking of animals, social network analysis and disease modelling. To simulate an infection, mice were injected with lipopolysaccharides (a component of the bacterial cell wall), which results in an immune response and generalized disease symptoms. In a paper published this week in the journal Scientific Reports, the team reveals that sick mice become disconnected from their social groups.

It is known that mice have the ability to detect other sick mice. Therefore, it was surprising to find that the animals in the same social group did not avoid the sick mouse. In fact, they went on interacting with the sick mouse and other mice more or less in the same way as before the experimental infection. "It was the sick mouse that removed itself from the group," emphasizes Lopes. She suggests that such a change in the behaviour of the sick mouse may protect relatives in the same group from catching the disease, which could be beneficial from an evolutionary perspective.

Speed and extent of disease spread are greatly reduced

In a further step, the researchers used mathematical models to predict how an infectious disease would spread considering the changes in behaviour of the sick animals. "When we account for the behavioural changes and how they affect social contacts, we find that the speed and the extent of disease spread are greatly reduced," says Lopes.

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Puerto Rico manatees threatened by isolation

Isolation of Puerto Rico's manatees affects survival odds

October 2012. New evidence shows there is no cross-breeding between endangered manatees in Puerto Rico and those in Florida, resulting in less genetic diversity in Puerto Rico's small manatee population and impacting its odds of survival.

The findings, which come from a study of West Indian manatees by the U.S. Geological Survey and Puerto Rico Manatee Conservation Center, could help resource managers make decisions about how to conserve the endangered marine mammal.

Wake up call
"Wildlife management has been one of the fields to benefit greatly from the ability to determine relatedness of individuals from DNA analysis, allowing management decisions to be based on concrete scientific evidence for genetic diversity and prospects for it to increase," said USGS Director Marcia McNutt. "These results for Puerto Rico's manatees are a wake-up call."

Just 250 manatees in Puerto Rico
One key management concern is the ability of Puerto Rico's manatees to absorb and rebound from population declines. Current estimates suggest as few as 250 individual manatees may currently live in Puerto Rico. Furthermore, the population's genetic diversity is low, a fact which decreases a wildlife population's capacity to adapt to changing conditions and rebound after critical events that can cause deaths, such as hurricanes, boat strikes, or disease.

This latest finding - that Puerto Rico's manatees are genetically isolated - shows the population's vulnerability to future ups and downs is not being offset by migration from Florida manatees, as was once hoped.

"Puerto Rico's Antillean manatees have low overall numbers and low genetic diversity, both of which present risks for the population's long-term survival," said Margaret Hunter, Ph.D., a USGS geneticist and lead author of the study. "The lack of gene flow is another risk factor. We detected no signs that the Puerto Rico population is being supplemented by Florida manatees, through migration or breeding. This means that Puerto Rico's population must absorb shocks - such as environmental change or disease - on their own. It's a trifecta of genetic vulnerability."

Continued:  http://www.wildlifeextra.com/go/news/puerto-rico-manatees.html