Biodiversity and One Health
What has biodiversity got to do with your health?
How do opossums stop you from getting Lyme’s disease?
WithSARS, MERS, Swine flu, SARS-CoV2 (Covid 19) and now Avian Influenza, again, you would be forgiven, and not wrong, for thinking that wildlife is not good for your health and another global pandemic is just round the corner.
But what if the same wildlife was actually key to our protection from global pandemics?
One of the major lessons to have emerged from the first SARS outbreak (2002/3) was that the underlying causes of new emerging zoonotic diseases is very likely to be in the parallel biodiversity loss crisis that occurred in the same timeframe. This came about as a result of the over exploitation of wild animals and the destruction of natural habitats by increasing human populations (Bell et al. 2004, Kessing et al. 2010, Cunningham et al. 2017).
Subsequent studies have found that biodiversity loss frequently increases disease transmission (Kessing et al 2010). There are various mechanisms at work including reduction in predation and competition of reservoir hosts, thereby increasing their density. In addition, experiments have confirmed that increases in disease transmission occur when the biodiversity declines but the density stays the same (Johnson et al. 2009). As well as the abundance of the host or a vector species, the behaviour of these species may change with the loss of biodiversity and play a role as well.
Add to that the fact that those species that survive disturbed or disturbed habitats, also tend to be those that are more likely to harbour zoonotic diseases.
The result is that in disturbed habitats, humans are more likely to come into contact with the mammals that carry the disease. In addition, each animal will have more pathogens to pass on, increasing the probability of infection each time contact is made. Therefore, the probability of infection increases, sometimes disproportionately, with the decrease in numbers of species(biodiversity). It is a lose lose situation for human health.
How destroying the Northeast Forest, USA, has increased the incidences of Lyme’s disease
For example, the black legged tick in the US is the main transmitter of Lyme’s disease. These ticks will use both the Virginia opossum and the white-footed mouse as a host. The opossum is very good at removing and killing the ticks through grooming. The ticks don’t get much chance to feed and pass on the pathogen. Few opossums therefore get infected and therefore don’t pass on the pathogen to uninfected ticks. The result is the number of ticks is low and very few of them are infected.
In contrast, the white footed mice aren’t so successful at grooming the ticks off, so they are more likely to come into contact with an infected tick that passes on the pathogen. More ticks feed off the mice and they all become infected.Therefore, there are a greater number of ticks and most of them are infected.
A person walking through a habitat dominated by opossums is unlikely to pick up a tick and extremely unlikely to pick up a tick that is infected. When walking through habitat dominated by white footed mice, as is the case when the opossum’s habitat – the Northeast Forest in the US – is bulldozed, a person is more likely to pick up a tick and it is highly likely that that tick is infected with Lyme’s disease.
And of course, biodiversity (the right species in the right place) will also protect human settlements from the climatic affects of global warming as well as provide land suitable for growing crops and livestock and harvesting wildlife products.
All doom and gloom?
NO! We know how these zoonotic diseases are emerging, we know what we are doing wrong and we know how to put that right.
We have the skills and WVI wants to ensure that those wildlife health skills are where they are needed – with those on the conservation front line, as part of multidisciplinary teams increasing biodiversity across the world.
WVI also has a responsibility to advocate wild animal health, under the OHHLEP umbrella of One Health, to conservation community to ensure they build it into the core of their activities saving and increasing biodiversity for the good of us all.
What you can do
Support our upcoming #Vets4Vultures campaign that highlights the demise of vultures as the best example of a wildlife disease that impacts ecosystem function and the health of other wildlife, livestock and humans.
Support initiatives by other organisations for example, supporting RSPO palm oil products as opposed to those not responsibly sourced, support initiatives to plant NATIVE trees and restore local biodiversity …..
OneHealth High-Level Expert Panel
The OHHLEP is a collaboration under the UNEP, FAO,WHO and OIE who all feed in their knowledge and evidence.
Their definition of One Health is the most useful, rejecting the anthropocentric view taken by other organisations. It identifies that the health of all living beings is interconnected and that restoring and maintaining the health of ecosystems is core to ensuring the health of domestic and wild animals and the health and wellbeing of people. By definition, this includes ensuring the health and conservation of wildlife at both population and species levels.
Bell,D., Roberton, S., and P.R. Hunter. (2004). Animal origins of SARS coronavirus:possible links with the international trade in small carnivores. https://doi.org/10.1098/rstb.2004.1492
Keesing, F., Belden, L., Daszak,P. et al. (2010). Impacts of biodiversity on the emergence and transmission of infectious diseases. Nature 468, 647–652 https://doi.org/10.1038/nature09575
Keesing F., Brunner J., Duerr S., Killilea M., LoGiudice K.,Schmidt K., Vuong H. and Ostfeld R. S. (2009) Hosts as ecological traps for thevector of Lyme disease Proc. R. Soc. B. 276.3911–3919 http://doi.org/10.1098/rspb.2009.1159
Cunningham AA, Daszak P,Wood JLN.(2017) One Health, emerging infectious diseases and wildlife: two decades ofprogress? Phil. Trans. R. Soc. B 372: 20160167. http://dx.doi.org/10.1098/rstb.2016.0167
Johnson, P. T. J., Lund, P.,Hartson, R. B. & Yoshino, T. Community diversity reduces Schistosomamansoni transmission and human infection risk. Proc. R. Soc. Lond. B 276,1657–1663 (2009)Through careful experimentation, the authors establish thatthe presence of another species can reduce parasite transmission even if thetotal density of hosts remains constant. (cited in Keesing et al. 2010)