Unintended consequences of wildlife conservation, could more frogs mean more mosquitoes?

We need to do all we can to protect our urban wildlife but what if the ways we do that increases mosquito risk? PhD candidate Jayne Hanford will be presenting the results of her research at the Ecological Society of Australia conference in Tasmania.

Mosquitoes can share their aquatic habitats with many other animals.

The 2019 Ecological Society of Australia conference will be held in Tasmania, 24-29 November. The conference theme, “Ecology: science for practical solutions”, is closely aligned with much of the work my collaborators and myself undertake each summer. We’re trying to ensure that recommendations on managing the pest and public health risks associated with mosquitoes is informed by the best available science.

Practical solutions to the challenges of balancing mosquito management while also ensuring positive outcomes from the environment too.

Jayne Hanford will be presenting her research in the “Field-based manipulative experiments for under-standing environmental change” symposium. She has been studying the aquatic biodiversity of urban wetlands as part of her PhD. This recent project aimed to determine what impacts management of urban wetlands to enhance conditions for local frog populations may have on local mosquito populations.

The research was undertaken at Sydney Olympic Park where an extensive network of freshwater ponds make up Narawang Wetlands. These wetlands are home to the endangered Green and Golden Bell Frog (Litoria aurea) but they’re also home to the plague minnow (Gambusia holbrooki). The plague minnow is essentially the cane toad of Australia’s waterways, introduced around 100 years ago to control mosquito populations, this aggressive predatory fish has impacted much of our local aquatic life, especially frogs. Populations of this fish need to be managed to enhance conditions for local frogs and, especially, their tadpoles.

Jayne has already found that mosquitoes avoid water bodies where the fish are found. The next step was to see how the seasonal draining of the local wetlands impacted the abundance and diversity of mosquito populations.

Immature mosquitoes and other aquatic macroinvertebrates were sampled from drained and undrained ponds within the wetland network. Once the drained ponds had been at least partially reflooded, mosquitoes were more likely to be found. This wasn’t too surprising given the results of previous experiments. Mosquitoes like to avoid habitats with fish but also, if they do lay eggs in those habitats, mosquito larvae aren’t likely to last long!

The results are useful for those authorities looking to manage waterbodies for wildlife conservation. Removal of the plague minnow may result in more suitable conditions being created for mosquitoes. It may be good for the frogs but we also know that their tadpoles aren’t eating the mosquito larvae. Strategies may be required to manage the pest and public health risks associated with local mosquitoes in these habitats.

You can catch Jayne’s work in the poster session but also as part of the symposium at 3pm on Monday 25 November in Chancellor 5!

The full abstract for Jayne’s presentation is below:

Unintended impacts of managing urban wetlands for conservation

Jayne K. Hanford^1,2*, Cameron E. Webb^2,3 , Dieter F. Hochuli¹

¹ School of Life and Environmental Sciences, The University of Sydney, Australia; ² Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Australia; ³ Medical Entomology, NSW Health Pathology, Westmead Hospital, Westmead, Australia.

Urban wetlands are increasingly being recognised as valuable conservation resources that support significant biodiversity. Concerns around the pest and public health risks of mosquitoes will restrict how we manage these wetlands, as outbreaks of mosquito-borne diseases fuel public fear and foster dislike of mosquitoes. Understanding the ecological and public health consequences of wetland management practices is vital to maximise the conservation value of urban wetlands without negatively impacting public health. Our aim was to determine how wetland management to benefit a threatened species affects mosquitoes and aquatic biodiversity. A group of six urban wetlands in Sydney, Australia, were drained to reduce the abundance of an invasive fish, Gambusia holbrooki, and then refilled to provide breeding habitat for a threatened frog, Litoria aurea. We collected and compared aquatic macroinvertebrates, mosquito larvae, and mosquito adults from these refilled wetlands, and six adjacent undrained wetlands, on four occasions across summer and autumn. Wetland draining had a significant effect on aquatic macroinvertebrates and larval mosquitoes, although differences between drained and undrained wetlands decreased over time. Draining did not affect adult mosquito assemblages associated with the wetlands. The number of constructed and rehabilitated wetlands in urban areas continues to grow, and while conserving threatened habitats and species is imperative, our results highlight how wetland management can impact non-target species with potentially negative effects on humans. It is vital that future design and management of urban wetlands around the world also considers the impact on vectors of human disease.

 

If you’re at the conference, why not join the conversation on Twitter using the official conference hashtag #ESAus19 or reaching out to Jayne or myself!

 

 

 

 

 

 

The long hot summer of mosquito and media wrangling

“Webb’s a mosquito researcher with NSW Health Pathology, and while it may sound like potentially the worst job in the world to the rest of us, it’s important work.” – Ten Daily, 14 Jan 2019.

Every summer I’m required to juggle those pesky mosquitoes and help out with requests from media. Over the past 6 months or so I’ve responded to about 70 media requests and here is a round up of some fun highlights and other bits and pieces.

There was a wide range of media requests this summer, from morning TV through to talkback radio, podcasts and live interviews via Skype. There was once a time when the only acceptable way to do a radio interview was via landline connected phone. This summer I did interviews via mobile, Skype, and various  smartphone apps! Times are a changing.

A fun segment on Channel 7’s ‘Sunrise’ breakfast show on why mosquitoes bite some people more than others; always a challenge taking in a cage a live mosquitoes to the studio, especially travelling in via public transport!

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A hot and dry summer must mean less mosquitoes, right?

The outlook for the 2018-2019 “mosquito season” was for it to be fairly routine. The Bureau of Meteorology was predicting a hot and dry summer under the influence of El Nino. At the time I wrote a piece for The Conversation highlighting that just because it was dry, that didn’t mean we wouldn’t see plenty of mosquitoes.

In coastal regions of Australia, tidal flooding of local wetlands often offsets any impact due to lack of rainfall. Mosquitoes such as Aedes vigilax certainly respond well and there were some very high mosquito numbers recorded in early spring. Usually, the media interest in mosquitoes starts increasing once the politicians break for the summer, this year there was plenty of interest early on!

NSW Health also issued a media release to get the community thinking about the potential mosquito impacts ahead of the summer holiday period and asked me to be the spokesperson. These warnings often prompt a different range of media interest, usually news bulletins for radio. Unlike the traditional radio interviews in which you’re responding to the host’s questions, only “grabs” (short statements regarding the topic) are required. I’ve learned there is a fine art to being concise in these statements and it pays to give some thought to what you’ll say ahead of calling up the news desk!

Some of the media coverage in early summer was less about bites and more about why mosquitoes disturb your sleep! I spoke with Channel Ten about how you can beat these bedroom buzzers! Here are some tips on beating the buzz of mosquitoes in the bedroom.

These concerns about mosquitoes in the bedroom prompted questions about the suitability of mosquito coils as a person protection measures. I’d written about this issue before but there was also some media coverage at the Daily Telegraph and Sydney Morning Herald.

There was also a funny segment on The Project:

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Warm weather, warm blood, and hungry mosquitoes

As summer kicked in, I did a bunch of “pre-season” interviews about the outlook for the mosquito activity ahead. One of them was with the Sydney Morning Herald. There was also a piece in Illawarra Murcury on the mosquitoes around Newcastle. I even chatted with ABC Illawarra about the mosquitoes bringing in the new year along the NSW coast. I also chatted with the team at the Daily Mail. Also the Daily Telegraph.

Once summer really hit (and the mosquitoes really started biting following heavy rains), everyone’s mind turned to one of the most commonly asked questions….why do mosquitoes bite me more than my friends? You can check out my contribution to a story by ABC Science below:

The usual coverage of mosquito impacts during the Australia Day holiday also popped up. Will my diet influence the likelihood of being bitten? I spoke with Channel Ten. The University of Sydney media team also put out a piece on why what you eat or drink makes not difference when it comes to stopping mosquito bites. A story picked up and republished by ABC News.

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Combining fieldwork and media requests

“Ballina council is calling in an expert to hunt for some ladies – Medical Entomologist Dr Cameron Webb will visit the area next week in search of blood sucking girls.” – EchoNet Daily, Ballina

While undertaking some work for Ballina Shire Council on the NSW far north coast, I helped out managing a few media requests associated with local mosquito problems and the work of council. It was fun squeezing in some print, TV, radio, and social media activities between the work in the wetlands.

I also participated in a “Q and A” on the Ballina Shire Council Facebook page where residents could ask questions about how best to protect themselves from mosquitoes. See here.

Mosquito-borne disease in the city

The detection of Ross River virus in mosquitoes around Sydney sparked some additional interest from media (and anxiety from local community). Coverage in Sydney Morning Herald here.  It prompted me to write an article about what the actual health implications were of finding the pathogen in a heavily urbanised areas such as the Parramatta River compared to the more bushland dominated Georges River.

The issue of wildlife and their role in urban transmission cycles of Ross River virus is always a tricky one. How do you balance wildlife conservation and mitigation of health risks? Together will colleagues I wrote about this at The Conversation.

The media coverage of the Ross River virus detection provided an opportunity for NSW Health Pathology to share some insights into how we research local mosquitoes and the pathogens they’re carrying. See below for a short video from the mangroves along the Parramatta River.

Did you know we monitor mosquitoes around the state to provide public health advice to @NSWHealth? Here’s our mozzie guru @Mozziebites (Dr Cameron Webb) explaining how we do this important work! pic.twitter.com/zpCTs7p3DL

— NSW Health Pathology (@NSWHPathology) January 10, 2019

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Declining insects, increasing mosquitoes, and the need to spray our backyards

One of the other stories bubbling along during the last year or so were the reports of declining global insect populations. I first spoke to the media about this issue back in early 2018. I was quoted in a couple of other stories too, clearly there was a lot of interest in this issue. This story gained plenty of attention and I spoke with various radio and print media about this challenge were facing with potential insect declines and how we can measure them. I even wrote an article about whether mosquitoes may be in decline too!

I spoke about this issue, and more generally about mosquitoes on an episode of the Science on Top podcast too.

There has been suggestions that insecticides may be contributing to declining insect populations. Earlier in the year, I was one of the coauthors of a paper that called for the need to better understand integrated pest control in our cities and become less reliant on insecticides. There was also an associated article at The Conversation. This was also republished at Domain.

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Floods in the north, floods in the south

The incredible flooding around Townsville in far north QLD created some major concern. Despite some initial concerns about increased mosquito risk, there weren’t any substantial increases in mosquito-borne disease reported. I spoke to ABC News about the potential risks.

The flooding that did trigger a big boost in mosquito numbers occurred in SE QLD and northern NSW. Local wetlands were inundated by tides and rain, resulting in some phenomenal numbers of mosquitoes in early autumn. I spoke to ABC and Great Lakes Advocate about the climatic factors that triggered this unusual mosquito activity.

Everyone was on weather watch late in the season too. A few extra downpours prompted concerns about more increases in autumn mosquito populations. I spoke with Sydney Morning Herald after a particularly wet weekend in March.

Finally, I helped the Australian Academy of Science make a video exploring why mosquitoes bite and how to stop them!

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Join the conversation on Twitter, did you catch me talking mosquitoes this summer? Did it help you protect your family from mosquito bites?

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