Culling of healthy animals hard to justify: Researchers

NEO CHAI CHIN Today Online 14 Mar 17;

SINGAPORE — It is very hard to justify the culling of healthy animals from a public health approach that should promote the health of humans, animals and the environment, argue Singapore researchers of a study published recently.

Their findings were derived from surveys and interviews with experts including officials from the Agri-food & Veterinary Authority (AVA), National Environment Agency (NEA) and the Ministry of Health (MOH).

Although human health remains the priority, the experts were generally not supportive of culling healthy animal populations in response to emerging infectious diseases — especially of wildlife and companion animals.

Of the 32 experts who took part in the qualitative study — published in late-January in the journal Plos One — five were from the Government while the rest were employed in academia, wildlife conservation and other fields.

They recognised that culling of animals was “highly controversial” and “extremely difficult to implement effectively within an urbanised area”, due to public objection and the logistics of quickly containing and killing large numbers of animals, noted the study.

Culling was recently in the news when public uproar ensued after the AVA put down 24 free-ranging chickens in Sin Ming.

The authority initially said it was due to complaints of noise by residents, but later explained that the noise pointed to the chickens’ relatively high numbers, which in turn raised exposure to bird flu in the area.

Culling is a last resort in managing Singapore’s animal population, Minister of State for National Development Koh Poh Koon said in Parliament last month.

The AVA also culls crows to control their population, and has tried other methods such as oral contraceptives and bird deterrent gels for other birds.

The opinion leaders who took part in the study were not named.

The multidisciplinary public health framework that aims to prevent and control emerging infectious diseases that can spread from animals to humans is called One Health.

Singapore’s One Health platform began in 2012 and involves the MOH, NEA and AVA.

The eight authors of the study — funded by the MOH — included Dr Tamra Lysaght of the National University of Singapore (NUS) Medicine’s Centre for Biomedical Ethics, and Dr Michele Marie Bailey and infectious diseases expert Paul Tambyah of NUS Medicine.

The effectiveness of culling domestic and wild animal populations is increasingly coming under scrutiny, after results of a randomised trial in Britain of badger culling (to reduce tuberculosis in cattle) showed the practice to be ineffective in reducing disease transmission, they wrote.

Culling may actually increase disease risk in humans and animals.

A reduction in natural hosts can force the pathogen to seek another animal host which could be even more hazardous for humans and other animals.

Alternatives such as animal vaccinations should be considered, and Professor Tambyah said surveillance and the development of diagnostics is also important.

An “extreme situation” where culling may have been justified was for pigs on Malaysian farms during the 1999 Nipah virus outbreak — because of the high numbers of infected people who were dying, the lack of a vaccine, and pigs being clearly identified as an “intermediate host” of the virus, catching it from bats, he said.

The One Health approach in Singapore worked well in the Group B Streptococcus outbreak of 2015, Prof Tambyah and Dr Lysaght said.

The agencies conducted joint investigations, issued public advisories, and stepped up measures such as banning the use of freshwater fish in all ready-to-eat raw fish dishes sold by retail food establishments.


Culling may cause more harm than good: Study
Audrey Tan, The Straits Times AsiaOne 14 Mar 17;

Mass culling of animals to prevent the spread of disease is a common practice around the world.

But its effectiveness is debatable, says a group of researchers here.

Disease could spread as animals move away from the areas where culling is taking place, say the scientists from the National University of Singapore (NUS), citing scientific studies that demonstrate this.

Instead, public health policies should take into account the health of both human and animal populations, through means like vaccinating the animals instead of culling them, for example.

The recent backlash against the Agri-Food and Veterinary Authority's (AVA) move to cull free-ranging chickens here over bird flu concerns has also shown that culling incites an emotional response.

The scientists from NUS pointed out that healthy animals should not be culled as a way of managing zoonotic diseases, or diseases that can be transmitted between humans and animals.

Read Also: Malaysia reports highly pathogenic H5N1 bird flu

This strategy does not consider the impact culling has on ecosystems already threatened by urbanisation.

"Current policies to manage diseases that can be transmitted from animals to humans have prioritised human health," said Assistant Professor Tamra Lysaght, the study's lead from the NUS Centre for Biomedical Ethics yesterday.

"But measures such as culling healthy animals do not account for other factors that contribute to the emergence and threat of emerging infectious diseases."

As ecosystems lose biodiversity, she explained, the number of natural animal hosts for diseases is reduced.

This can lead to the pathogens looking for other hosts, resulting in the emergence of new zoonotic infectious diseases or more dangerous viruses.

She was speaking about her team's new research paper, which looks at how global public health policies needed to be more aware of both human and animal health.

Published in January in scientific journal Plos One, the paper analysed the responses of 32 panellists from AVA, veterinarians, academics and wildlife conservationists on Singapore's approach to managing zoonotic diseases.

Participants found culling controversial and "extremely difficult to implement effectively within an urbanised area", the study noted.

Alternatives, such as the use of animal vaccines, were discussed, but participants said these can be difficult to administer, depending on the animal, the type of virus and drug availability.

No uniform policy option to deal with emerging infectious diseases was given, and this illustrates the need to explore other approaches such as medication, good surveillance and open communication to tackle the issue, said the scientists.

One of the study's authors, NUS infectious diseases expert Paul Tambyah, said that developing surveillance networks will quickly alert the authorities to infections and prevent the spread of diseases, reducing the need for mass culling.

"In Hong Kong, for example, there is a reward system in place for farmers who alert the authorities to cases of bird flu. That has helped Hong Kong keep the virus under control," he said.

Developing a comprehensive ecological approach to healthcare would result in a win-win approach to dealing with zoonotic diseases which will not unfairly tax healthy animal populations, he added.

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