In Australia, urbanisation is bringing animals and diseases closer to home

This little guy could give you leptospirosis, toxoplasmosis, hantavirus infection, or the plague. Image: Getty.

Our world is becoming increasingly urbanised. In 1950, just 30 per cent of the world’s population lived in urban areas. This number is now over 50 per cent and rising. By 2050, two-thirds of the world’s population are expected to be urban dwellers. Although much of this growth will occur in developing regions, northern Australian cities are likely to see significant expansion.

The successful growth of cities will undoubtedly be critical to the economic health of Australia and the surrounding region. However, the increasing size and density of human populations are creating challenges for human health. A report published this week by Australia's national science agency CSIRO, Australia’s Biosecurity Future: Preparing for Future Biological Challenges, highlights the biosecurity risk of urbanisation as cities become hotspots for new and emerging infectious diseases.

Animal hosts

The number of emerging infectious diseases that infect people has more than tripled since the 1940s. Around two-thirds of these are zoonotic, which means that they have spilled over into human populations from animals. The number of emerging diseases is likely to continue to increase, driven by the globalisation of travel and trade, climate change and, of course, urbanisation.

Urbanisation modifies the environment rapidly and permanently, creating irreversible changes in biodiversity. Animal species that can adapt to disturbed or fragmented environments (urban adapters) or thrive when living closely with people (urban exploiters) will prosper in cities. But those that cannot adapt (urban avoiders) may die out. This process contributes to the reduced biodiversity seen in urban environments.

In Australia, urban adaptors include familiar species such as the noisy miner bird and the common brushtail possum; urban exploiters are often invasive species, such as rats and pigeons.

The high prevalence of urban adapters/exploiters in city environments means people may be at risk from the diseases they carry. Possums have already been identified as potential sources of zoonotic bacteria in drinking water in Australia, while rats have been associated with many zoonotic diseases, including leptospirosis, toxoplasmosis, the plague and hantavirus infection.

Insects, such as mosquitoes, also differ in their ability to colonise urban environments. Mosquitoes that breed in small amounts of standing water and prefer to feed on humans are often abundant in urban environments. They have been instrumental in the emergence and spread of viruses like dengue and Chikungunya.

A warming climate is predicted to increase the geographic range of some of these urbanised mosquitoes. Growing cities will increase the number of people at risk from the diseases they carry.

Animal-to-human transmission

Why some diseases spill over from animal to human populations while others do not depends on many factors, including the genetic, cellular and behavioural characteristics of the pathogen, animal and human host. But, although scientists are still trying to unravel the complexity of this process, we do know that the frequency of contact between animal and human populations is a significant contributor to the probability that cross-species transmission occurs.

Processes such as deforestation and urbanisation can change the way human and animal populations interact. Land-use changes such as these have been associated with the emergence of many significant zoonotic diseases, including dengue, malaria, severe acute respiratory syndrome (SARS) and Ebola.

Mosquitos adapt easily to urban environments, preferring to stick close to hubs of human activity where there is plenty to eat. James Gathany/AAP

Although we tend to focus on pathogens that have successfully jumped species to transmit and cause disease in a new host (such as dengue and SARS viruses), most cross-species transmission events go no further than the first infected individual. In these cases, which include hantavirus and rabies virus infection, people are dead-end hosts.

It is not yet clear why some zoonotic pathogens are able to cause sustained human disease, while others are never transmitted between people. We need to unravel the complex interactions between pathogens, their hosts and the environment to begin to predict which diseases carried by animals pose the greatest threat to human health in an increasingly urbanised world.

Reducing the risks

Zoonotic disease outbreaks place significant burdens on public health systems, as well as on local and global economies. Despite the relatively localised scale of the current Ebola outbreak, the World Bank is forecasting costs as high as US$33 billion by the end of 2015, a number approaching the estimated US$40 billion price tag of the SARS epidemic.

Given the extraordinary costs associated with outbreak response and control, it is clear we need to focus on prevention and surveillance to reduce the incidence of emerging infectious diseases in the future.

Despite the challenges of an increasingly urbanised world, the concentration of people in cities also provides opportunities to reduce and control new and emerging infectious diseases. Compared with rural areas, the centralisation of money, power and knowledge can greatly improve surveillance and intervention measures in cities. This includes increasing access to clean drinking water, improved sanitation and urban flood reduction.

Good hygiene practices can decrease the spread of infectious diseases. Brandon Otto/ Flickr, CC BY-NC

City dwellers also often have greater access to mass media than people in many rural areas. This provides a platform for public health campaigns aimed at increasing awareness of behaviours that reduce the risk of acquiring infectious diseases. These include the importance of vaccination, hand-washing, insecticide use and waste management, among others.

Taking steps to improve urban disease surveillance, developing effective prevention measures and initiating appropriate education campaigns will allow us to significantly reduce the impact of emerging infectious diseases.The Conversation

Kurt Zuelke is a director, and Cadhla Firth a research scientist, at the Commonwealth Scientific & Industrial Research Organisation (CSIRO), the national science agency of Australia.

The authors do not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article. They also have no relevant affiliations.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

What would an extended Glasgow Subway look like?

West Street station. Image: Finlay McWalter/Wikimedia Commons.

There are many notable things about Glasgow’s historic Subway.

It is the third oldest in the world. It is the only one in the UK that runs entirely underground. It runs on a rare 4ft gauge. For reasons passing human understanding, it shuts at teatime on a Sunday.

But more significantly, it’s the only metro system never to have been expanded since its original development. A couple of stations have come and gone in the 122 years since the Subway opened (and promptly shut again following a serious accident before the first day was out). But Glasgow’s Subway has remained a frustratingly closed loop. Indeed, while a Scottish newspaper recently estimated there have been more than 50 proposed new stations for Glasgow's iconic Subway since it first opened, all we’ve had are a couple of replacements for closed stops. 

The original route map. Image: SPT.

It’s not for a lack of trying, or at the least discussion. Glasgow’s SNP-led council pledged a major expansion of the Subway as part of their election pledge last year, for example, vowing to find the funding to take the network beyond the existing route.

All this sounds very familiar, of course. A decade ago, with the 2014 Commonwealth Games in mind, operators SPT began looking into a near-£3bn expansion of the Subway into the East End of the city, primarily to serve the new Velodrome complex and Celtic Park.

In the end, the plans — like so many discussed for expanding the Subway – failed to materialised, despite then SPT chairman Alistair Watson claiming at the time: “We will deliver the East End extension for 2014. I am being unequivocal about that.”

As detailed previously on CityMetric, that extension would have seen seven new stations being opened along a second, eastern-centric loop, crossing over with the original Subway at two city centre sites. Had that gone ahead, we would by now have had a new route looking something like this:

The 2007 proposals for an eastern circle. Image: Iain Hepburn.

St Mungo’s would have been close to Glasgow Cathedral. Onslow, presumably located on or near Onslow Drive, would have principally served Dennistoun, as would have a link-up with the existing Duke St overground station.

Gorbals, benefiting from the ongoing redevelopment and residential expansion that’s all but erased it’s No Mean City reputation, would have gained a station, while Newhall would have been next to Glasgow Green. Dalmarnock station would, like Duke Street, become an interchange with Scotrail’s services, while crucially Celtic Park would have gained the final stop, serving both the football stadium, the nearby Emirates Arena and velodrome, and the Forge shopping centre.


Those plans, though, were drawn up more than a decade ago. And if the SNP administration is serious about looking again at the expansion of the Subway, then there’s more than a few changes needing made to those plans.

For starters, one stop at the far end of the loop serving Celtic, the new sports arenas and the Forge feels a bit like underselling the area, particularly with so much new residential development nearby.

Two feels more realistic: one serving the Forge and the rest of Dennistoun, and the other sited on London Road to serve the mass volumes of football and sports traffic. And if Ibrox can have a stop, then it seems churlish not to give the other of the Old Firm clubs their own named halt.

That’s another thing. The naming of the proposed stations is… arbitrary, to say the least. You’d struggle to find many Glaswegians who’d immediately identify where Newhall or Onslow were, off the top of their head. 

The former, especially, seems like there’s a more natural alternative name, Glasgow Green; while the latter, with a second Forge stop also serving Dennistoun, would perhaps benefit from named for the nearby Alexandra Place and park.

(Actually, if we’re renaming stations from their unlikely original choices, let’s say goodbye Hillhead and a big hiya to Byres Road on the original Subway while we’re at it…)

So, what would a realistic, 2017-developed version of that original 2007 proposal give us? Probably something like this:

Better. Image: Iain Hepburn.

One glaring issue with the original 2007 study was the crossover with the… let’s call it the Western Subway. The original proposal had St Enoch and Buchanan St as the crossover points, meaning that, if you wanted to go out east from, say, the Shields Road park and ride, you had to go into town and double back. 

Using Bridge Street as a third interchange feels a more realistic, and sensible, approach to alleviating city centre crowding and making the journey convenient for folk travelling directly from west to east.

There’s a good case to be made for another south east of the river station, depending on where the Gorbals stop is sited. But these are austere times and with the cost of the expansion now likely more than £5bn at current rates, an expanded Bridge Street would do much of that legwork.

Putting all that together, you’d end up with something looking like this:

 

Ooooh. Image: Iain Hepburn.

Ahead of last year’s election, SNP councillor Kenny McLean vowed the party “[would] look at possible extension of the Subway and consider innovative funding methods, such as City Bonds, to fund this work. The subway is over 120 years old. It is high time that we look to connect communities in the north and east of Glasgow.”

Whether Glasgow could raise the £5bn it would probably need to make the 2007 proposal, or an updated variation of it remains, to be seen. And this still doesn’t solve how many places are left off the system. While a line all the way out to Glasgow Airport is unrealistic – after all, an overground rail service to the airport from Paisley has failed to materialise after 30 years of discussion and planning – there’s plenty of places in the city not well served by the Subway, from Maryhill in the north to Hampden in the south, or the riverside developments that have seen flats replace factories and new media hubs, museums and hotels line the Clyde.


Image: Iain Hepburn.

Key city landmarks like the Barrowlands, the Riverside Museum – with its own, fake, vintage subway stop, or the Merchant City are woefully underserved by the subway. But their incorporation – or connection with a Glasgow Crossrail – seems a very expensive pipe dream.

Instead, two adjoining loops, one to Ibrox and one to Celtic Park, seems the most plausible future for an extended Subway. At least colour coding the lines would be easy…

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