Ecology Determines Rabies Infection in Bats

A new approach to rabies virus epidemiology in bats shows that the risk of infection is higher in large and multispecies colonies. The research, published on the journal PLOS ONE, was led by Jordi Serra-Cobo, professor from the Department of Animal Biology at the UB and the Biodiversity Research Institute (IRBio).

Bats are a large group of mammals that appeared in our planet around 65 million years ago (Figure 1). They have colonized many natural habitats —except the poles—, and act as primary predators of vast numbers of insects in ecosystems. They are also the mammals which present the widest variety of virus infection (rabies, SARS, Ebola, etc.). Moreover, they are able to neutralize virus and survive infections. “Chiropters, a quite ancient animal group, are major reservoirs for diverse infectious viral diseases”, highlights Serra-Cobo. They have co-lived with virus for a long time and their immunological responses are more effective. According to Serra-Cobo, “this fact opens new research lines on the organisms’ immunological response and strategies to fight against infectious diseases”.

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Figure 1. A vespertilionid bat from Spain, one of the more than 1,150 bat species.

It is the first time that a research analyses ecological factors that might affect the infection dynamics of the rabies virus in bat colonies. Between 2001 and 2011, 2,393 blood samples were collected from 20 bats species and 25 localities in Catalonia, Aragon and Balearic Islands. The research is centered on the detection of
European bat Lyssavirus 1 (EBL1), one of the twelve different groups of the genus Lyssavirus related to rabies, an emergent zoonosis that affects mammals all over the world.

Jordi Serra-Cobo explains that “EBLV-1 seroprevalence is strongly affected by colony size and species richness. Previous studies have analyzed other aspects such as the seasonal variability. Ecological factors play a relevant role in seroprevalence variability, but they were to date unknown” (Figure 2).

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Figure 2. Variation in the percentages of seropositive bats as a function of species richness and colony size. (from Serra-Cobo et al. 2013)


All bat species do not response in the same way to viral infections. This research proves that immunological response to rabies virus varies among species. “Order Chiroptera has been widely diversified along its evolutionary history —affirms Serra Cobo— and their responses to ultrasound orientation mechanisms, immunological defense, etc. vary with different lineages”.

There are more than 1,150 bat species all over the world and new specimens are described every year. However, the loss of natural habitats due to human activity and climate change poses a major threat to bats. “It is a process of environmental degradation which favors the formation of larger bat colonies, which have a higher probability of EBLV-1 infection”, remarks Serra Cobo.
 
Spain has been free of rabies in terrestrial mammals since 1977. Nevertheless, in some countries it continues to be a problem of public Health. To know risk factors involved in viral disease transmission is essential to improve preventive policies. The new article published on
PLOS ONE will provide new tools to know more about viral infections epidemiology and natural resources management.

Source: Modified from materials provide by The Universitat de Barcelona.


Reference

Jordi Serra-Cobo,, Marc López-Roig,, Magdalena Seguí,, Luisa Pilar Sánchez,, Jacint Nadal,, Miquel Borrás,, Rachel Lavenir,, & Hervé Bourhy (2013). Ecological Factors Associated with European Bat Lyssavirus Seroprevalence in Spanish Bats PLOS ONE DOI: 10.1371/journal.pone.0064467.t003


Orangutans plan and communicate their travel plans

For a long time it was thought that only humans had the ability to anticipate future actions, whereas animals are caught in the here and now. But in recent years, clever experiments with great apes in zoos have shown that they do remember past events and can plan for their future needs. Anthropologists at the University of Zurich have now investigated whether wild apes also have this skill, following them for several years through the dense tropical swamplands of Sumatra.

It turns out that wild male orangutans do plan their travel route up to one day in advance and communicate it to other members of their species (Figure 1). In order to attract females and repel male rivals, they call in the direction in which they are going to travel. Anthropologists at the University of Zurich have found that not only captive, but also wild-living orangutans make use of their planning ability.

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Figure 1. Travel maps of wild orangutans. Green arrows show “long calls”. (from van Schaik et al. 2013)

Orangutans generally journey through the forest alone, but they also maintain social relationships. Adult males sometimes emit loud ‘long calls’ to attract females and repel rivals. Their cheek pads act as a funnel for amplifying the sound in the same way as a megaphone. Females that only hear a faint call come closer in order not to lose contact. Non-dominant males on the other hand hurry in the opposite direction if they hear the call coming loud and clear in their direction (Figure 1).

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Figure 2. A Orangutan males give long calls to attract females (or repel rival males). Female A perceives a faint call compared to female B, even if they are at the same distance from the calling male, because the male is facing female B. If the male is moving in the same direction as he is calling, female A should move in the direction of the male whereas B need not. (from van Schaik et al. 2013)

“To optimize the effect of these calls, it thus would make sense for the male to call in the direction of his future whereabouts, if he already knew about them”, explains Carel van Schaik. “We then actually observed that the males traveled for several hours in approximately the same direction as they had called.” In extreme cases, long calls made around nesting time in the evening predicted the travel direction better than random until the evening of the next day. Carel van Schaik and his team conclude that orangutans plan their route up to a day ahead.
In addition, the males often announced changes in travel direction with a new, better-fitting long call. The researchers also found that in the morning, the other orangutans reacted correctly to the long call of the previous evening, even if no new long call was emitted. “Our study makes it clear that wild orangutans do not simply live in the here and now, but can imagine a future and even announce their plans. In this sense, then, they have become a bit more like us”, concludes Carel van Schaik.

Source: Modified from materials provided by The University of Zurich.

Reference:

Carel P. van Schaik,, Laura Damerius,, & Karin Isler (2013). Wild Orangutan Males Plan and Communicate Their Travel Direction One Day in Advance PLOS ONE DOI: 10.1371/journal.pone.0074896