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.

 
 
 
 

Never mind Brexit: TfL just released new tube map showing an interchange at Camden Town!!!

Mmmmm tube-y goodness. Image: TfL.

Crossrail has just been given a £1bn bail out. This, according to the Financial TImes’s Jim Pickard, is on top of the £600m bailout in July and £300m loan in October.

That, even with the pound crashing as it is right now, is quite a lot of money. It’s bad, especially at a time when there is still seemingly not a penny available to make sure trains can actually run in the north.

But the world is quite depressing enough today, so let’s focus on something happier. On Saturday night – obviously peak time for cartographic news – Transport for London emailed me to let me know it would be updating the tube map, to show more street-level interchanges:

Connections between several pairs of stations that are near to each other, but have traditionally not been shown as interchanges, now appear on the map for the first time. These include:

  • Camden Road and Camden Town
  • Euston and Euston Square
  • Finchley Road and Finchley Road & Frognal
  • Kenton and Northwick Park
  • New Cross and New Cross Gate
  • Seven Sisters and South Tottenham
  • Swiss Cottage and South Hampstead

The stations shown meet a set of criteria that has been used to help determine which should be included. This criteria includes stations less than a 700m or a 10 minute walk apart, where there is an easy, well-lit, signposted walking route and where making the change opens up additional travel options.

The results are, well, this:

In addition, interchanges between stations have traditionally appeared on the Tube map as two solid lines, irrespective of whether they are internal or external (which means customers need to leave the station and then re-enter for the station or stop they need). This approach has now been updated and shows a clear distinction between the two types, with external interchanges now being depicted by a dashed line, linking the two stations or stops.

And lo, it came to pass:

I have slightly mixed feelings about this, in all honesty. On the positive side: I think generally showing useful street-level interchanges as A Good Thing. I’ve thought for years that Camden Road/Camden Town in particular was one worth highlighting, as it opens up a huge number of north-east travel options (Finchley to Hackney, say), and apps like CityMapper tell you to use it already.


And yet, now they’ve actually done it, I’m suddenly not sure. That interchange is pretty useful if you’re an able bodied person who doesn’t mind navigating crowds or crossing roads – but the map gives you no indication that it’s a harder interchange than, say, Wanstead Park to Forest Gate.

The new map also doesn’t tell you how far you’re going to be walking at street level. I can see the argument that a 400m walk shouldn’t disqualify something as an interchange – you can end up walking that far inside certain stations (Green Park, Bank/Monument), and the map shows them as interchanges. But the new version makes no effort to distinguish between 100m walks (West Hampstead) and 700m ones (Northwick Park-Kenton), which it probably should.

I’m also slightly baffled by some of the specific choices. Is Finchley Road-Finchley Road & Frognal really a useful interchange, when there’s an easier and more direct version, one stop up the line? No hang on West Hampstead isn’t on the Metropolitan line isn’t it? So that’s what it’s about.

Okay, a better one: if you’re switching from District to Central lines in the City, you’re generally better off alighting at Cannon Street, rather than Monument, for Bank – honestly, it’s a 90 second walk to the new entrance on Walbrook. Yet that one isn’t there. What gives?

The complete new tube map. The full version is on TfL’s website, here.

On balance, showing more possible interchanges on the map is a positive change. But it doesn’t negate the need for a fundamental rethink of how the tube map looks and what it is for. And it’s not, I fear, enough to distract from the Crossrail problem.

Jonn Elledge is the editor of CityMetric. He is on Twitter as @jonnelledge and on Facebook as JonnElledgeWrites.