A guide to living with bats
Bats are proof that ecosystem services can be delivered in strange forms - even by animals that some people see as unwholesome neighbours. This is the message from a team of experts assembled by the UN Food and Agriculture Organization (FAO) to address the risk posed by bats as vectors of emerging disease. Theirs is a blueprint for meeting this risk without disrupting the vital roles of bats in protecting, pollinating, dispersing and fertilising plants.
The manual, Investigating the role of bats in emerging zoonoses: Balancing ecology, conservation and public health interest, is unusual subject matter for FAO. Its authors are wildlife biologists and disease researchers, who are attempting to bring scientific perspective to a subject of growing alarm: diseases carried by bats that can spread to livestock and ultimately people. But the manual has become more than just a guide to bat diseases because the experts know that bats play other roles, says editor Scott Newman.
Ecosystem services from above
One instance is that insect-eating bats regulate entire ecosystems and can save crops from disaster. "Insectivorous bats are estimated to consume 25 per cent of their body mass in insects each night," Newman says, citing a study published this year in the journal Science. "A colony of one million Brazilian free-tailed bats weighing twelve grams each could consume 8.4 metric tons of insects in a single night. Bats therefore offer valuable pest control services, and it is estimated that they save American farmers alone between US$3.7 billion and US$54 billion a year."
Bats are not a small subject: over 1,240 known species account for an astonishing 20 per cent of all mammal biodiversity. While insectivorous species keep bugs in check, fruit bats provide important services as pollinators and seed dispersers, spreading the seeds of their own habitats widely on their nocturnal journeys. Bats also pollinate agriculturally important tree and shrub species, including baobab, durian and coconut palms. And farmers prize bat droppings (guano) as rich natural fertiliser.
On the other hand, human distrust of bats has recently been rekindled by focus on wild animals as disease vectors. "Due to increased surveillance efforts and better diagnostic technology, the scientific community is finding more viruses or potential pathogens in bats, and some of the potential zoonoses harboured by bats - including Nipah Virus, Ebola, SARS and rabies - are life threatening," says Newman.
"Often the bats are vilified, when in most cases it is likely that bats have harboured these pathogens for thousands of years without becoming sick. It is only in the recent past that increased bat-human or bat-livestock-human contact has resulted in these pathogens making the jump to people." These closer contacts are largely a result of human activities: deforestation, expanding urbanisation and farming.
One Health for bats, livestock and people
FAO's new manual looks at these concerns within a One Health approach, a framework that addresses zoonotic diseases by understanding and monitoring the connections between different species with the aim of protecting the health of all. The idea of bringing veterinary and human health together was first explored in the 1960s, but it was the recent threat of H5N1 avian influenza, and a series of Ministerial conferences addressing the disease, that really brought focus to the animal-human-ecosystem interface.
The One Health approach requires the integration of many fields, and the manual provides some of the ways and means. "The manual was created for capacity development in countries interested in creating bat ecology, monitoring or disease surveillance programmes," says Newman. "It is intended for colleagues who have minimal knowledge about these topics and may be from public health, biology, wildlife, forestry, laboratory diagnostic, veterinary or agricultural professions."
A game of balance
The Philippines is one country with a particular interest in the strategy. The archipelago nation is home to some notable bat-maintained ecosystems, such as the Subic Bay Forest Watershed Reserve. The trees of this forest are propagated by over 10,000 fruit bats, and the watershed in turn provides freshwater for the country's fastest growing industrial port.
"In the Philippines, to address Ebola reston virus detection in pigs, a One Health approach was used to evaluate the situation by collaboration among the Ministries responsible for Health, Agriculture, and Wildlife," Newman reports. This has ensured that bat habitats are monitored and protected while pigs and humans are buffered from the deadly virus.
"We do not know which other countries have accessed the manual on-line, but FAO has started using it to support One Health capacity development, specifically in the Field Epidemiology Training Programme for Veterinarians (FEPTV). We envision distributing this manual to most member countries in Eurasia, Africa and the Americas." Most immediately, the manual will now serve as the backbone of a project being implemented by FAO and partners in Thailand and Vietnam.
"We have seen more progress at the Ministry level demonstrating cross sectoral collaboration, but we still have a long way to go," says Newman. "For One Health to succeed, collaboration must occur at all levels ranging from international organizations, to national authorities, down to the implementation of activities in the field at a local community level."
Written by: T. Paul Cox
Date published: January 2012
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