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's actually in the UK government’s bailout package for Transport for London?

Wood Green Underground station, north London. Image: Getty.

On 14 May, hours before London’s transport authority ran out of money, the British government agreed to a financial rescue package. Many details of that bailout – its size, the fact it was roughly two-thirds cash and one-third loan, many conditions attached – have been known about for weeks. 

But the information was filtered through spokespeople, because the exact terms of the deal had not been published. This was clearly a source of frustration for London’s mayor Sadiq Khan, who stood to take the political heat for some of the ensuing cuts (to free travel for the old or young, say), but had no way of backing up his contention that the British government made him do it.

That changed Tuesday when Transport for London published this month's board papers, which include a copy of the letter in which transport secretary Grant Shapps sets out the exact terms of the bailout deal. You can read the whole thing here, if you’re so minded, but here are the three big things revealed in the new disclosure.

Firstly, there’s some flexibility in the size of the deal. The bailout was reported to be worth £1.6 billion, significantly less than the £1.9 billion that TfL wanted. In his letter, Shapps spells it out: “To the extent that the actual funding shortfall is greater or lesser than £1.6bn then the amount of Extraordinary Grant and TfL borrowing will increase pro rata, up to a maximum of £1.9bn in aggregate or reduce pro rata accordingly”. 

To put that in English, London’s transport network will not be grinding to a halt because the government didn’t believe TfL about how much money it would need. Up to a point, the money will be available without further negotiations.

The second big takeaway from these board papers is that negotiations will be going on anyway. This bail out is meant to keep TfL rolling until 17 October; but because the agency gets around three-quarters of its revenues from fares, and because the pandemic means fares are likely to be depressed for the foreseeable future, it’s not clear what is meant to happen after that. Social distancing, the board papers note, means that the network will only be able to handle 13 to 20% of normal passenger numbers, even when every service is running.


Shapps’ letter doesn’t answer this question, but it does at least give a sense of when an answer may be forthcoming. It promises “an immediate and broad ranging government-led review of TfL’s future financial position and future financial structure”, which will publish detailed recommendations by the end of August. That will take in fares, operating efficiencies, capital expenditure, “the current fiscal devolution arrangements” – basically, everything. 

The third thing we leaned from that letter is that, to the first approximation, every change to London’s transport policy that is now being rushed through was an explicit condition of this deal. Segregated cycle lanes, pavement extensions and road closures? All in there. So are the suspension of free travel for people under 18, or free peak-hours travel for those over 60. So are increases in the level of the congestion charge.

Many of these changes may be unpopular, but we now know they are not being embraced by London’s mayor entirely on their own merit: They’re being pushed by the Department of Transport as a condition of receiving the bailout. No wonder Khan was miffed that the latter hadn’t been published.

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