Lifting the veil of mystery surrounding bats

FAO "bat manual" aims to reduce disease risk, highlight benefits

24 August 2012, Rome - Few animals have suffered more from negative publicity than the bat. Nature's only winged mammal is frequently depicted in folklore and films as destructive, unhealthy and unattractive. Increasing concern about the bat's potential for spreading disease to other animals and humans has contributed to the suspicion that often surrounds the animal.

A manual published by the UN Food and Agriculture Organization aims to help countries minimize the risks to public health, while protecting the vital role that bats play in agriculture and the environment. 

The guide, "Investigating the Role of Bats in Emerging Zoonoses: Balancing Ecology, Conservation and Public Health Interest," is a hands-on reference to bat history, biology, monitoring, handling, and disease screening. The text is especially relevant as diseases transmitted by bats appear to be on the rise for various reasons. 

Agricultural expansion and the use of natural resources are encroaching on bat-occupied territories, leading to increases in the interaction between bats, livestock and people. Understanding the changes that affect these populations is critical to addressing the risks, and limiting the exchange, of viruses between species. 

The publication is designed for use by epidemiologists, wildlife officials, farmers, livestock veterinarians, zoologists, and any number of different professionals who might come into contact with bats. It was written by veterinarians, wildlife biologists, virologists, and disease experts, and includes field techniques for studying bats and infectious agents that do not cause disease in bats, but which can cause other animals or humans to become sick. 

Natural allies in farm production

"Bats really are natural allies to the environment. They pollinate plants, spread seeds, and some species can devour about 25 percent of their body weight in insects. These benefits far outweigh their potential for transmitting disease. Yet, we cannot ignore the fact that development, demographics, and consumption of natural resources are bringing people, livestock and bats into closer and more frequent contact with one another. This increases the risk that bats can transmit potential pathogens and associated diseases to other animals and people," said Scott Newman, FAO wildlife veterinary epidemiologist, and co-author of the guide.

In the Philippines, the pollination provided by bats is crucial to maintaining ecosystems like the Subic Bay Forest Watershed Reserve. Government ministries responsible for Health, Agriculture and Wildlife have worked together to protect bat habitats while monitoring them to protect pigs and humans from disease spread. 

Disease transmission 

The bat manual is part of a broader effort by FAO and its partners to build awareness of the importance of wildlife to agriculture, ecosystems, and animal and human health. 

In Malaysia and Bangladesh, fruit bats have been known to transmit Nipah virus, a previously unknown, contagious and deadly disease which was first recorded in pigs and humans in the 1990's. Disease studies showed that bats directly infected pigs in Malaysia, while in Bangladesh, humans picked up the virus primarily by ingesting date-palm sap that had been contaminated by bat excretions. 

In Latin America, vampire bat-variant rabies causes a significant number of human deaths each year. In Southeast Asia and Africa, bats are being evaluated for the role they play in Ebola outbreaks. 

Fruit bats from the order Pteropodidae are the animal reservoirs for Ebola, which can cause a deadly hemorrhagic disease in humans and other mammals.  Outbreaks of Ebola in human populations are relatively rare, but mortality rates can reach up to 90 percent. 

"It's important to realize that, while bats may pose a risk to human health, in most cases, disease exposure from bats is usually a result of human activity. This means that we can study bats and learn healthier ways to share our farms, forests and communities with them," Newman added. 

"The new guide supports countries in their efforts to improve management of bats' natural habitats while ensuring the health of humans, livestock and other wildlife species." 

Balancing act 

FAO's new manual looks at these concerns within a One Health approach. One Health is a framework that addresses zoonotic diseases by using a multi-disciplinary perspective to understand and monitor the connections between different species and their agro-ecological habitats, with the aim of protecting the health of all. 

"FAO has started using the bat manual for capacity development in keeping with the One Health concept, specifically in the Field Epidemiology Training Programme for Veterinarians (FEPTV). We plan to distribute this manual to our member countries in Eurasia, Africa and the Americas," says Newman. 

The new manual will also be used in regional disease-monitoring projects being implemented by FAO and partners in Thailand, the Philippines, and Vietnam. The projects will study how the interface between wildlife, livestock and humans can affect the spread of Henipah, Lyssa and Corona viruses - all pathogens capable of causing illness and death in domesticated animals and humans. 

Investigating the Role of Bats in Emerging Zoonoses: Balancing Ecology, Conservation and Public Health Interest" was produced, in part, with financial support from the government of Australia, APHCA, and technical and in-kind support from various partners.