Changes in human diseases or epidemiological transitions have always occurred during shifts in human social organisations and many scientists propose that we are about to enter another as a result of globalisation and ecological disruption (mcMichael 2001). Habitat complexity influences the composition, abundance and distribution of animals that play a role in the transmission cycles of many common human infectious diseases such as malaria and schistosomiasis. As a result, habitat and biodiversity loss influences transmission cycles by affecting the abundance, behaviour and condition of hosts or vectors (Keesing 2010).

Biodiversity affects the abundance of the host or vector organisms involved in disease transmission. For example, plants growing in experimental fields not hosts for fungal pathogens decreased the pathogen load of species that are hosts by reducing host density through competition (Mitchell 2002). 

Furthermore, the behaviour of host, vectors and parasites can change as a result of biodiversity loss affecting rates of transmission and prevalence in human populations. In more diverse habitats, a parasite is more likely to end up in an unsuitable intermediate host reducing the probability of infecting a human. This was demonstrated by studies on parasitic worms that cause schistosomiasis (Laracuente 1979).

Finally, biodiversity loss and human led habitat alteration clearly involves changing conditions. This can lead to increased encounter rates between pathogens and hosts when the host species has not undergone declines.  Furthermore, another plant study comparing genetically diverse and non diverse experimental fields found that those growing in species rich conditions had dryer leaves as a result of changes in microclimatic conditions and as a result had lower prevalence of a fungus. (Keesing 2010)

As ecosystem health and transmission processes are so nuanced, it is difficult to separate individual mechanisms to find direct cause and effect. Clearer patterns emerge when considering different infectious diseases independently. Malaria, one of the most damaging infectious diseases, resulting in 1 million deaths in 2007 alone is caused by one of four Plasmodium species via the female anopheles mosquito. Habitat alteration, particularly deforestation, is having a huge influence on transmission rates. Deforestation acts to raise surface water availability through the formation of puddles and pools that act as new breeding sites for the mosquito. Furthermore, microclimates as mentioned above are also affected. Larvas may be exposed to greater sunlight raising temperatures which cause mosquitos to digest more quickly so feed more often and lay more eggs. Higher temperatures affect the adult mosquito by reducing development time. In addition to this human factors clearly play a great role. Globalisation changes migration patterns and leads to the emigration of non immune individuals into high malaria risk areas affecting incidence and transmission (Pongsiri et al 2009).

As the links between ecosystems, biodiversity and disease occupy varying temporal and spatial realms and across political boundaries nuanced research is needed.  Furthermore, this is a relatively new field of study so there is far more to be discovered. Policy informed by this evidence can then be formulated that acts to preserve both human life and local and global habitats. 

Sources:

Keesing et al. 2010. Impacts of biodiversity on the emergence and transmission of infectious disease. Nature. Vol 468 (7324). pp 647- 652.  

Laracuente, A. 1979. Comparison of four species of snails as

potential decoys to intercept schistosome miracidia. Am. J. Trop. Med. Hyg. Vol 28. pp

99–105

McMichael, A. 2002. Population, environment, disease and survival: past patterns, uncertain futures. The Lancet. Vol 359. pp 1145-1148. 

Mitchell, C et al. 2002. Effects of grassland plant species diversity, abundance, and composition on foliar fungal disease. Ecology. Vol 83. pp1713–1726

Pongsiri et al. 2009. Biodiversity loss affects global biodiversity. Bioscience. Vol 59(11). pp 945-954. 

Drug Discovery 2

Much pharmacognosy is focused on cancer, as with over 10 million new cases in the year 2000 alone there is huge demand for new treatments. For example, the US’s National Cooperative Drug Discovery Group (NCDDG) is working on “Novel Strategies for Plant-derived Anticancer Agents” alongside several leading universities and pharmaceutical companies. 

They collected 5886 plant accessions from 2582 species with collections primarily carried out in tropical forests due to their capacity to support a very diverse range of taxa and species. 

Chloroform-soluble extracts were then prepared and screened by a variety of in vitro bioassays. Active extracts were then subject to ‘dereplication’ to determine of they contained previously isolated cytotoxic compounds. Treating cells with cytotoxic compounds can result in cells undergoing apoptosis (programmed cell death), necrosis (where cells lose membrane integrity and die via cell lysis) or stopping growing and dividing. Potential extracts are isolated by fractionation and further follow up studies are carried out on compounds of interest (Balunas, M et al.  2005).

Following from this initial collection and subsequent testing, 3 main chemicals are still undergoing further study. One chemical of interest includes Pervilleine A, found in extracts from the roots of the Madagascan plant Erythroxylum pervillei. This chemical acts to restore sensitivity of certain multi drug resistant cells, as the development of multi-drug resistant tumour cells is a serious problem associated with chemotherapy (Mi, Q et al. 2001).  

Further developments in cancer treatment drawing on plant resources have occurred in Australia. EBC-46 developed by the QIMR Berghofer Medical Research Institute is thought to destroy cancerous tumours by cutting of blood supply and is produced from the berry of  Fontainea picrosperma (Boyle, G et al. 2014).

It is clear then, considering global plant biodiversity and the extent of plant collection and subsequent testing required, preserving tropical forests and maintaining maximum biodiversity for future drug potential is a priority.   

Sources:

Balunas, M et al. 2005. Drug Discovery from Medicinal Plants. Life Sciences. 78(5). pp 431-441. 

Boyle, G et al. 2014. Intra-Lesional Injection of the Novel PKC Activator EBC-46 Rapidly Ablates Tumors in Mouse Models. Plos:One. [online]. Available at: http://www.plosone.org/article/authors/info%3Adoi%2F10.1371%2Fjournal.pone.0108887.[Accesssed: 19 November 2014] 

Mi, Q et al. 2001. Pervilleine A, a novel tropane alkaloid that reverses the multidrug-resistance phenotype. Cancer Research. 61(10). pp 4030- 4037. 

Conserving Drugs

The development of pharmaceutical drugs from plants is known as Pharmacognosy or ‘a molecular science that explores naturally occurring structure–activity relationships with a drug potential’. This encapsulates fields including plant ecology, ethnobotany, phytochemistry and molecular biology (Bruhn and Bohlin, 1997). The term has only been in use for the past 200 years although treatments from medicinal plants is clearly nothing new (Balunas, M. 2005).

The first records of plants as medicines were found in Mesopotamia dating back to 2500BC. These included oils of cedar and cypress as well as elements of liquorice and myrrh all still used today to treat a range of ailments from coughs and colds to inflammation. The world health organisation estimates that 80% of the global population still rely predominately on traditional medicine such as the above, although plant sources still play a surprising role in the drugs used by the remaining 20% (Newman et al, 2000). For example, in 2001 and 2002 a quarter of the best selling drugs worldwide were derived from natural products (Balunas, M. 2005). This includes Artemesinin  an anti-malarial drug derived from the Chinese herb Qinghao or Sweet Wormwood and Cromoglycate, a compound based on a chemical from the Khella plant used to treat asthma (Shetty, P. 2010). 

Artemesinin

Qinghao / Sweet Wormwood

The link between conservation and the search for new pharmaceuticals is clearly apparent. We never know when the next new drug may arise from so it is vital to preserve high biodiversity regions to preserve potential sources. Furthermore, it can be of great benefit to conservation efforts that may have previously focused on alternate issues if a new plant derived drug is found in an area.  In these cases governments are likely to place higher values on the area as a result of profit potential and future economic impact (Balik, 1994).

The protection of biodiversity for medical and health reasons is one of the most compelling arguments for conservation. However, it requires long term focus and planning considering the length of time between discovery and the large scale production of a drug. 

Sources:

Balik, M. 1994. Ethnobotany, drug development and biodiversity conservation -exploring the linkages. Ciba Foundation Symposium. 185. pp 4-18. 

Balunas, M et al. 2005. Drug Discovery from Medicinal Plants. Life Sciences. 78(5). pp 431-441. 

Bruhn, J. Bohlin, L. 1997. Molecular Pharmacognosy: An explanatory model. Drug Discovery Today. 2(6). pp 243-246.

Newman, D et al. 2000. The Influence of Natural Products Upon Drug Discovery. Natural Products Report. 17. pp 215-234.

Shetty, P. 2010. Integrating Modern and Traditional Medicine: Facts and Figures. SciDevNet. [online]. Available at: http://www.scidev.net/global/disease/feature/integrating-modern-and-traditional-medicine-facts-and-figures.html. [Accessed: 19 November 2014]. 

Floundering Fisheries

I always knew I would include a blog post on the impact of declining fish stocks but when it came about to researching for the post I was surprised. Compared to the sheer quantity of media hype over the plight of the bees there was very little concerning fish despite the wide ranging implications.

European fish stocks, and the UK's in particular, are in decline for a multiple of reasons including pollution and climate change yet it is direct human action through overfishing that is considered the greatest threat to marine ecosystems. Damage to marine ecosystems has far reaching impacts on human populations from protein consumption to employment to rural ways of life. 

Research on 43 european fish stocks assessed the impact of healthy, biodiverse fisheries on local employment and economies.  They found that 72% of stocks were below optimal level with €3 billion lost every year as a result. This money could support 100,000 jobs in the industry across Europe and boost local and national economies (Crilly, R et al, 2012) .  
Local economies, reliant on this primary sector have already experienced slow decline. For example, the Marine Conservation society and researchers from the University of York found that fishing fleet in the UK are having to work 17 times harder to make the same catch than the 1880s with peak fish landings in 1937. This is despite significant technological advances (Thurstan et al, 2010). With dwindling job opportunities and economic prospects, many face poverty or are abandoning this traditional way of life resulting in rural decline.

Marine ecosystems in Europe are a truly interdisiciplinary problem. A policy overhaul is required that balances the demands of human populations whilst allowing for recovery and then sustainable management. 

Sources:

Crilly, R et al. 2012. Jobs Lost at Sea. New Economics Forum. [pdf]. Available at: http://b.3cdn.net/nefoundation/e966d4ce355b7485c1_a7m6brn5t.pdf [Accessed 18.11.2014]

Thurstan, R. et al. 2010. The effects of 118 years of industrial fishing 
on UK bottom trawl fisheries. Nature Communication. [online]. 1(15). Available at: http://www.nature.com/ncomms/journal/v1/n2/pdf/ncomms1013.pdf. [Accessed 12.11.2014]

A Step In The Right Direction?

On Tuesday, Liz Trust the Secretary of State for Environment, Food and Rural Affairs delivered a speech on the link between the natural environment and the economy where she announced a number of interesting policy initiatives.

A highlight included the Wild Pollinator and Farm Wildlife Package, a 900 million payment scheme to encourage farmers to maintain hedgerows and strips of wildlife-friendly ground round the edges of fields, providing sources of food and nesting sites for insects. Other pollinator friendly initiatives included “Bees Needs” a website with guidelines and strategy to help individuals and groups improve their local environment for bees in both rural and urban areas and investment in research to gather more information on the condition of pollinators in the UK.

It is really encouraging to find an environment policy that has been so widely applauded as a step in the right direction, from conservation groups such as the RSPB to the Daily Mail. However, I do feel that initiatives such as this are a way of ‘greening’ the appearance of the current Conservative government whilst they continue to fail to tackle more complex issues such as our fossil fuel dependence (Trust, 2014). 

The full speech can be found here:  
Trust, E. 2014. Environment and the Rural Economy.   [transcript]. 4.11.2014. Available at:https://www.gov.uk/government/speeches/elizabeth-truss-speech-on-the-environment-and-the-rural-economy [Accessed: 6.11.2014]