Avian Botulism

With outbreaks of avian botulism happening more often, and in more locations, around New Zealand, Te Kunenga ki Pūrehuroa Massey University is spearheading a research programme to develop an effective system for managing endemic wildlife diseases, such as avian botulism.

The programme aims include understanding where the outbreak hotspots are and why and what to do about it. Professor Ngaio Beausoleil (co-director of the Animal Welfare Science and Bioethics Centre at Massey’s School of Veterinary Science) leads the team of researchers. Of particular interest to her is the intersection of conservation and wild animal welfare.  

Although avian botulism is one of the most significant diseases impacting waterbirds globally and there are now regular outbreaks in New Zealand in which many birds and fish die, not much is known about this endemic wildlife disease in this country.  

Researchers at Te Kunenga ki Pūrehuroa Massey University, led by Ngaio Beausoleil, a Professor of Animal Welfare Science along with collaborators at the SPCA, Wildways Auckland University, are working with a range of stakeholders across the country to develop a co-ordinated approach to predicting, mitigating and managing outbreaks.

Avian botulism is caused by a toxin produced by Clostridium botulinum bacteria. Professor Beausoleil explains that the bacteria causing avian botulism are always present in soils and sediments but that conditions caused by changing land and water management, climate change and extreme weather events stimulate the bacteria to multiply and produce toxin – poor water quality, more nutrients in waterways, warmer temperatures, and both drought and flooding. 

“When waters are warm, full of nutrients, high pH and low in oxygen, botulism bacteria grow and produce lots of toxin. These bacteria live in the sludge at the bottom of waterways which is why ducks and other waterbirds that feed by sifting through sediment are most at risk. 

“Ducks such as mallards, New Zealand’s threatened brown teal/pateke, other waterbirds like swans and tuna/eels ingest these bacteria and toxins when searching for food in lakes, ponds, wetlands and wastewater treatment plants. In the last three months, at least three major outbreaks have been reported, with one event including the deaths of 80 endangered native ducks.” 

Professor Beausoleil explains the toxin affects nerve function leading to paralysis that starts at the feet and rises up the body with affected birds becoming unable to hold their head out of the water. “Infected birds become unable to swim, walk or breathe in severe cases, and so often drown or get caught by predators, causing great suffering. Eels usually bob to the surface dead.  

“Within hours, flies find dead birds and eels and lay their eggs. The maggots that hatch and feed on the dead tissues act as ‘toxin concentrators’, quickly infecting other birds that come to eat the delicious maggots off their friends. This ‘carcass-maggot cycle’ can very quickly lead to outbreaks which can kill hundreds of birds. Quickly removing sick birds and carcasses is key to controlling outbreaks but this means we have to know where, when and why outbreaks are likely to happen and have effective systems for responding.”  

Ngaio confirms that the strain of bacteria affecting wild birds and fish is different from the one usually affecting mammals, including humans, and so the avian disease is unlikely to be a risk to people. While poultry are susceptible to botulism, they are unlikely to be infected because they won’t be exposed to sick waterbirds. However, other diseases that can be transmitted to people can look similar to avian botulism, so it is recommended that anyone collecting sick birds or carcasses wears protective equipment. 

Professor Beausoleil and her team are especially mindful of the impacts of avian botulism on people too, especially those in rural communities who are most likely to be the ones who first discover an outbreak and then become involved in the cleanup.  

“Ensuring good animal health and wellbeing is at the heart of rural life, and birds and fish infected with botulism suffer poor welfare before dying.  As well as the risk that the birds are sick with something else that can infect people, people’s emotional wellbeing can be at risk when they discover and have to kill sick birds or remove lots of carcasses.” 

She adds that although people harvesting wild kai, including shooting ducks and collecting eels, are very unlikely to get sick from eating infected animals, most want to know that the animals had led healthy, happy lives.  

The research team has pulled together a targeted network of interested parties including iwi, wildlife veterinarians and rehabilitators, water managers and regulators, animal health testing specialists, conservation regulators, environmental scientists, emergency managers and wildlife organisations, amongst others. 

Included in those stakeholders is Dean Wilson, the Environmental Manager for the Muaūpoko Tribal Authority. He has been working with Te Kunenga ki Pūrehuroa Massey University as a result of some serious outbreaks of botulism in recent years. He says it killed around 5,500 birds, and about 2,000 fish and tuna at Lake Horowhenua.

They are now focusing on water quality, as well the health of populations of birds, fish and invertebrates in the catchment with a cultural health monitoring index being developed and supported by Te Kunenga ki Pūrehuroa Massey University. He adds there are often visits from Te Kunenga ki Pūrehuroa Massey University students, to discuss the care of the lake from the iwi perspective.

In partnership with MPI’s Animal Health Team and Epi-Interactive, specialists in helping organisations to achieve value from data, the team is also developing ways to collect outbreak data to help understand where likely outbreak hotspots are, why and what should be done about it. 

However, the broader research programme is dependent on securing further funding.  

Professor Beausoleil says, “we need data if people have it. And really importantly we need funding, so that we can actually do this work, because it’s really difficult to pull people together around the country and to investigate all of the different parts that we need to bring together to manage this disease effectively.”

Currently each region around the country manages outbreaks of avian botulism differently and next steps involve bringing together stakeholders to develop a national system that will include citizen science/community reporting and develop humane, practical and safer (physically and emotionally) methods for managing to euthanising sick birds in the field as and when necessary. 

Link to reporting sick birds here