Category: Perspectives

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Intelligent Design: Part Three – Dr Alistair Noble’s ‘The Scientific Evidence for Intelligent Design’: the review

BwcOmega911a

I would like to say that the talk presented a range of evidence for intelligent design and carefully countered the usual arguments against it. I would like to say this, but I can’t. The talk, which lasted over one hour, spent much of the time quoting non-scientists and misquoting scientists, painting ID proponents as martyrs to the cause and science as tautologically incapable of addressing questions of design. The religious beliefs of ID proponents were constantly referred to, despite supposedly being completely irrelevant, which was an indication that this was, after all, a religious proposition not a scientific one.

It would be easy to question the credentials of Dr Alistair Noble (PhD in chemistry) and ask how someone who has been outside of scientific academia longer than I have been alive can claim to have found fundamental flaws that no working biologist has been able to find, but I won’t. Instead, I have tried to focus on the claims of Dr Noble and see if they can be answered (see my last blog post).

There is much more that I could have said. The case for evolution is so strong that I could go on for hours about the evidence from multiple disciplines that support it. It seems that the same cannot be said for intelligent design. Dr Noble spent about 15 minutes of his (more than) one hour talk providing evidence which can be easily refuted by anyone who has even a basic understanding of evolutionary theory. His ‘evidence’ ultimately boiled down to an Argument from Incredulity with a side helping of the Argument from Authority.

I was disappointed by the lack of scientific rigor Dr Noble exhibited. Not one journal article was presented, not a single claim that hasn’t been refuted multiple times before. I had hoped for an intellectually stimulating talk that would force me to question my understanding of evolutionary theory but instead I was confronted with the same, tired claims that have been presented by ID proponents for years now. It is a shame that Dr Noble could not have used his clearly considerable intellect to study the actual science and see that evolutionary theory is not a threat to his faith but is an amazingly simple yet profound explanation into how the diversity of life arose.

Author

Sarah Hearne: hearnes[at]tcd.ie

Photo credit

wikimedia commons

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The buzz on neonicotinoids

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On the 31st January, stimulated by a European Food Safety Authority report, the EU proposed banning three neonicotinoid insecticides which have been implicated in causing honeybee decline. These insecticides are widely-used, systemic (i.e. soluble enough in water to move around the plant’s vascular system to nearly all plant tissues), and, like nicotine, affect the insects’ central nervous system. They are highly effective at reducing insect pests that feed on crops and reduce yields and value, and many farmers are concerned about the effect the proposed ban will have on crop production. But these insecticides can also end up in the nectar and pollen of crops (as well as in the soil and in non-crop plants), and thus can have unintended side-effects on beneficial, nectar-feeding insects, who act as pollinators. Especially bees.

Bee decline has become a hot topic with scientists, the media, the public and even some politicians, but until recently the threat of neonicotinoids to bees has not been seriously implicated in their decline. Concern about pollinator decline is a result of the important role that pollinators play in food production: 75% of crop species depend on animal pollinators, which translates into 35% of global production; and the total annual economic value of pollination has been estimated at €153 billion globally. In addition, pollinators are fundamental to most terrestrial ecosystems, and indirectly affect the availability of food for other organisms (e.g. fruits and berries for frugivorous birds), as well as the structure and functioning of ecosystems.

So here’s the paradox: flower-visiting insects including bees are really important for agricultural production. But so is the use of neonicotinoid pesticides. Which is more important and is the ban justified on scientific grounds?

In the last year, the evidence that neonicotinoids have negative impacts on bees has been mounting. Bees and other flower-visiting insects are exposed to neonicotinoid pesticides in multiple ways: during planting of seeds which have been coated with pesticides as a pre-planting treatment, by collecting pollen and nectar from the crop, and by foraging on non-crop plants which take the pesticide up through the soil. Traditionally, toxicological tests of agrochemicals are carried out on the managed honeybee Apis mellifera, and pesticides are rated according to their lethal effects (by calculating the LD50 – the dose required to kill half the organisms tested after a specified duration). But the biology of Apis and all the other bee species (20,000 of them worldwide) is different. Can we generalise about effects on Apis, to effects on other bee species, and other pollinating insects including hoverflies and butterflies? And what about sub-lethal effects, i.e. those that don’t kill the insects, but affect their physiolology, behaviour and fitness?

Neonicotinoids are highly toxic to insects – that’s the whole point of them. Bees are insects. So it shouldn’t be too much of a shock that they kill bees. Last year it was shown that neonicotinoids can also have sub-lethal effects in honeybees, by decreasing foraging success and navigation by individuals back to the hive. At the same time, the neonicotinoid pesticide, imidacloprid, can reduce bumblebee colony growth and fitness by affecting their feeding behaviour. Some dissenters have cast doubt on the field-relevance of laboratory tests, claiming that field-realistic dosages have not been used, but this is not the case – the concentration of imidacloprid in oilseed rape flowers for example has been found to be 4.4-7.6 mg/kg in pollen and 0.6-0.8 mg/kg in nectar, which was within the range tested on bumblebees. This is pretty convincing evidence that neonicotinoids can cause very adverse effects on populations of these social bees.

Although neonicotinoids are not the only cause of widespread bee decline, they are more than likely contributing to it. Some of the agrochemical companies are claiming that bee decline has nothing to do with their chemicals and instead blame decline on Varroa destructor, the parasitic mite which infects honeybee colonies. Whilst Varroa probably plays its part in honeybee decline, the most probable cause of decline in other bee species is multiple pressures, including habitat loss and loss of forage plants, AND the use of neonicotinoid pesticides.

So should these insecticides be banned? YES, if we want to address pollinator decline. They should not be used for insect-pollinated crops, and wind-pollinated crops that insects forage on (including maize). But what’s the alternative for the farmer? How can crop production be maintained in the absence of these chemicals? Use something worse? If we’ve learned anything since Rachel Carson’s “Silent Spring” published 50 years ago last year, it’s that an alternative will be found, and we can’t be sure that this won’t be worse for the bees and other pollinating insects.

Author

Jane Stout: stoutj@tcd.ie

Photo credit

wikimedia commons

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Coursing conundrum

Female_Irish_mountain_hare

At first glance, many scientific ideas can appear counterintuitive. A press release from a leading Irish wildlife charity in support of the proposed coursing ban prompted me to attempt to balance the discussion of coursing impacts on the Irish hare population. The bill to ban coursing is due to come before the Dáil in the coming months. However, the above press release immediately struck me as biased, and so I felt a discussion of coursing impacts was required before the public were asked to sign any petitions in support of this ban. For those unsure of just what coursing is, it is a popular field sport which consists of a hare being chased by a pair of greyhounds over a short distance. Unlike fox and deer hunting, the aim of coursing is not to kill the hare. It is instead a speed and agility competition between two dogs, where each is awarded points depending on its ability to “turn” the hare from a direct route along the field. Irish hares (Lepus timidus hibernicus Bell 1837) are caught and held in captivity prior to an event during which the hare is coursed within an enclosed park. A running hare is given a 75m head start before the release of two dogs, whose performance is assessed by a judge, and surviving hares escape into an area from which the dogs are excluded. The duration of the pursuit is relatively brief, usually lasting less than a minute, and surviving hares are returned to the wild after the event.

The IWT states something which a few of us may agree with; that Ireland is lagging behind in terms of its attitude to welfare and conservation of native wildlife. However, the idea that a coursing ban would in some way improve this status is highly questionable. Welfare issues need to be taken into account, but these considerations must be viewed in parallel with the beneficial aspects of coursing, such as habitat conservation and the associated protection of both target and non-target species, before any final judgements regarding coursing acceptability can be made. It is perhaps unintuitive, but evidence indicates that coursing has an extremely large positive impact on hare numbers. Mortality of coursed hares stands at just 4.1% since the implementation of dog muzzling in 1993, and research has found coursing to have negligible impacts on hare populations due their large intrinsic rates of increase. People who participate in coursing maximise hare populations in coursing preserves through predator control and set aside to conserve habitat suited to the Irish hare. In fact, it is agricultural intensification (an issue completely ignored in the IWT article) which is more likely to blame for population declines. Habitat management to encourage target species for hunting can protect against the detrimental effects of modern agricultural policy on biodiversity. Irish Coursing Club preserves host a hare density 3 times greater than that supported by the wider countryside. What is more probable is that coursing is actually stemming the tide of anthropogenic destruction of many species our native wildlife (including corncrakes and many other farmland bird species) through habitat conservation aimed at artificially increasing hare populations for coursing. If coursing were to be banned in this country, this practice would be completely abandoned due to waning interest in encouraging hare numbers, and could potentially have serious ramifications for other wildlife which benefit from associated habitat management and predator control. Incentives to promote hare conservation would be required, but it’s questionable whether these would produce the same results as coursing-associated management due to a lack of personal interest for farmers and other landowners who practice coursing. Hare conservation in the absence of coursing, similar to that of other species benefiting from game management, would be a costly endeavour and would be unlikely to be awarded the necessary funding in the Republic of Ireland with the current economic climate.

We have the opportunity to be forward-thinking, innovative and inclusive in the way in which we achieve sustainable conservation of our native wildlife, something which appears all the more important in light of the EU agricultural policy reforms which were leaked in recent days. We can only hope that a review of the research will stop the Dáil bowing to ill-informed political pressure and perhaps, the future of farmland birds and our only endemic mammal, the Irish hare, will be ensured.

Author

Emma Murphy: butlere1[at]tcd.ie

Photo credit

wikimedia commons

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Treasures of Natural History

Natural_History_Museum_London_Jan_2006

The Natural History Museum in London is one of my favourite places. The majesty and beauty of the building’s design is a fitting exterior to house the truly stunning collections within.

The new Treasures exhibition displays just 22 of the museum’s most prized possessions. It’s a special opportunity to see valued and varied treasures such as the type specimen of the earliest known bird, Archaeopteryx, Darwin’s pigeons and the Iguanodon teeth which sparked the discovery of the dinosaurs all lined up together. The stories behind the origin and significance of each of the treasures are fascinating.

Although not one of the most famous objects, the Emperor Penguin’s egg was my favourite item. The egg is beautiful in itself but its real value as a treasure lies in the story behind its collection. It is one of just 3 intact specimens which were collected by Captain Scott’s ill-fated Antarctic expedition between 1910 and 1913. In this centenary anniversary year, Scott’s quest to reach the South Pole remains one of the most inspiring examples of human endeavour. Before the age of GPS, insulated clothes or re-heatable “expedition food”, Scott’s crew ventured into the heart of the frozen continent.  As if striving to reach the pole wasn’t enough of a challenge in itself, the expedition also had the aim of collecting as much scientific data about Antarctica as possible. Their chief scientist Edward Wilson wanted to examine penguin embryos for evidence of an evolutionary link between birds and reptiles. However, Wilson was part of the team who perished with Scott on their return journey from the Pole. The specialist embryologist who was going to study the eggs died in the First World War and by the time results from studying the eggs were published in 1934, the evolutionary recapitulation theory on which the egg-study was based was outdated.

The story behind this egg certainly puts the trials of modern scientific research into perspective. While the rate of new scientific discoveries shows no sign of slowing, delving into the finer details of the inner workings of the cell or the evolution of drug-resistant bacteria doesn’t hold quite the same level of physical adventure as that which was represented by Scott’s expedition. I’m not for one instant suggesting that I long for a more dangerous yet adventurous age or that modern fieldwork is not without its trials and difficulties. I just don’t know of any current research projects which can match Scott’s story in terms of raw human endeavour into the most unknown, dangerous and inhospitable conditions imaginable. It was a treat to see such a precious and fragile reminder of past scientific endeavour on display.

The treasures exhibition is a stunning collection of prized objects and should be treated as a site of pilgrimage for anyone even remotely interested in evolution or the natural world. Most of the specimens are unique but fortunately an example of one treasure, the Great Auk can be seen in the TCD Zoology museum. So that’s one ticked off the list for Trinity – though I’ve a feeling that it might take just a little while for us to match the rest of London’s collection …

Author

Sive Finlay: sfinlay[at]tcd.ie

Photo credit

wikimedia commons

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What is Life?

Erwin_Schrödinger

February 5th marked the 70th anniversary of the first lecture of what was later to become Schrödinger’s highly influential book ‘What is life’.

While Schrödinger may be more popularised by his infamous zombie cat, it was his thinking with regards to how life can live with the laws of physics that have allowed him to transcend that major divide between the physics and biological communities.

Schrödinger’s genius insight was to see life as a system behaving and constrained by the second law of thermodynamics, in particular describing the probable nature of a hereditary crystal, which would later lead scientists including Shannon and Weaver to the discovery of DNA and the genetic code.

However what makes the story of this work more fascinating, in particular to me as I have been lucky enough to get the opportunity to give a (very) small talk in the same lecture theatre were Schrödinger gave his lectures 70 years ago, is the story of how an Austrian physicist ended up in the capital of Ireland writing some of the most important work in biology of the last century.

Schrödinger, an Austrian, fled Germany in 1933 due to his dislike of the Nazi’s anti-Semitism and became a fellow in Oxford, during which time he received a Nobel Prize with Paul Dirac. However things turned sour with Oxford due to his less then monogamous approach to the opposite sex, and the lack of acceptance towards living with his wife and mistress lead him to leave for Princeton. These problems followed him there and eventual he found himself back in Austria in 1936. The occupation of Austria by the Germans in 1938 led him to again flee, this time to Italy. But in the same year Eamon de Valera, Ireland’s Taoiseach (Prime Minister) at the time, personally invited him to Dublin were he spent the next 17 years.

It was here in Trinity College Dublin that he delivered his lecture series which were to inspire both Watson and Crick to search for the genetic molecule and which has recently seen some increased popularity due to its use by Brian Cox in his latest series What is Life. However this work came about I like to think that “What is life” found its way to Ireland through Nazis and polygamy, a story surely of the calibre for the Discovery channel, if only it had some sharks.

Author

Kevin Healy: healyk[at]tcd.ie

Photo credit

wikimedia commons

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Intelligent Design: Part Two – Dr Alistair Noble’s ‘The Scientific Evidence for Intelligent Design’: the claims

800px-The_Creation_of_Adam

“A lie can travel halfway round the world before the truth has got its boots on” (Mark Twain, attributed).

In my previous post I gave some background on intelligent design, the theme of a talk I recently attended by  Dr Alistair Noble. This time, I’ll try and address his claims.

It is easy to say something that is not true. It is not always so easy to explain why it is not true. Such is my problem here. I can summarise Dr Noble’s arguments into a few sentences, but it takes paragraphs to explain why they are wrong. Here goes!

His argument centered around DNA. Dr Noble’s background in chemistry, specifically in trying to artificially synthesise chemicals, showed him how difficult it was to make even simple molecules. He explained his problems with DNA and used two specific examples to illustrate his argument: the bacterial flagellum and cytochrome C. His arguments were essentially:

  1. they look designed
  2. they are too complex to have arisen by chance

 

The design argument can be easily refuted. Apparent design does not mean actual design. Humans are extremely good at seeing things where they do not exist, like shapes in clouds and Jesus on burnt toast. This is a well-known psychological phenomena called paradolia and can lead us to see design where none exists.

The second claim requires a bit more care. DNA, the bacterial flagellum and Cytochrome C are all highly complex and could not have evolved by chance. In fact, as Dr Noble so carefully illustrated, Cytochrome C would have taken longer than the lifetime of the universe to arise by chance. So if they did not arise by chance then they must have arisen by design, surely? Well, no.

This conclusion can only be made if you have a deep misunderstanding of evolution. At a very basic level random mutations occur which may be beneficial, neutral, or detrimental to an individual. Then natural selection ‘selects’ those mutations which are beneficial and ‘rejects’ those that the detrimental. Small changes over long timescales lead to big changes, mutations can build on each other and can be co-opted to other functions. The bacterial flagellum is a perfect example, with studies showing how molecules were co-opted from other functions to form the flagella. At no point was there a useless proto-flagellum.

ID proponents, including Dr Noble, focus on the random aspect of evolution but completely ignore the selection part, which is arguably the more important aspect. If there were no natural selection then their claims would be valid, but its presence provides a beautifully simple explanation of how complex molecules, complex biological components, and even complex organisms could arise.

Next time, my review of the talk.

Author

Sarah Hearne: hearnes[at]tcd.ie

Photo credit

wikimedia commons

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The Flora of the Future

Flora of the future

It’s the year 2050. Several billion more humans occupy the world, and species translocations are by now the norm to mitigate against increased urban sprawl, climatic instability and a sea level now a third of a metre higher. In spite of unprecedented demands on the natural environment, governments have slowly developed capacity for conservation of wilderness and semi-natural habitat. Beyond this even, with the vast majority of the human race by now living in cities and the continued trend of rural land abandonment; restoration ecology has come to the fore at entire landscape and regional scales. The concept of ‘rewilding’ is debated openly amongst politicians and the public – no longer the mere theoretical exercise of academics. The monetary value of ecosystem services is also by now a very real and tangible concept within economic circles, embedded within highly developed metrics such as green-GDP.  Despite such positive developments, however, problematic legacies of the past remain. Intensification of agriculture has been unrelenting globally, notwithstanding inroads into adoption of agroecosystem approaches. A transition to truly renewable energy sources is still incomplete and of utmost urgency. One of the most critical questions of all most likely still looms – have we yet done enough to put a cap in the peak of this, the sixth great mass-extinction of life on the planet?

And so, it is within this future and none-the-less challenging world we find the modern ecologist and biodiversity practitioner at work.

What kind of new and useful technologies may exist to help tackle such problems and challenges of the not so distant future? It is interesting to deliberate on one low-tech tool in particular (the so-called bread and butter of biodiversity), which has been with us already for centuries – and that is the humble species checklist. Specifically we take a look at the Flora – and although coverage here is rather phyto-centric, it should be easy to draw equivalents to all forms of taxa, without (too) much stretch of the imagination.

So what is a Flora in the traditional sense, why is this changing, and how will the Flora of the Future look and function? To briefly tackle these first two questions, a Flora is primarily a list of plant biodiversity (either with or without diagnostic characters and keys) within a specified geographic range, be it local, national or at larger scales. Outside of this basic function there are the ‘added-extras’, which may include notes on distribution, ecology, synonymy, conservation status and even ethnobotanical use. Often the assemblage of national-level Floras has proven quite a mammoth task; logistically challenging, fraught with funding difficulties, and above all time-consuming – with efforts spanning over several decades for particularly biodiverse countries. This is all very well, and such traditional Floras have and will continue to serve as invaluable tools. In this modern age, however, change is called for to tackle some common short-comings of the Flora.  A considerable amount of valuable information collected by taxonomists and other experts in the production process is typically lost, never making its way into the public realm – and when such publications can easily run to over 20 volumes, it is clear to see the major constraints involved. Another key drawback is the sheer speed at which redundancy can occur. Even before the final volume of a Flora is published, taxa (species/genera/families) covered within the first volumes may have long been ripe for new taxonomic treatment.

The revolution in how biological information is collected, stored and disseminated is already greatly influencing the Flora. One of the most recently initiated national-level projects is the Flora of Nepal project, for which advances in biodiversity informatics have permeated the entire process from preparation to publication. Although the Flora of Nepal will still be published in printed format, a (if not the) main focus will be an E-Flora freely accessible online, which will also greatly expand the availability of information assembled by experts. A simple yet very significant feature will be the ease of portability of numerous volumes to the field in digital format.  Though perhaps most critically, the Flora of Nepal will be maintained and updated to reflect new findings – creating for the first time, in essence, an evolving Flora.

Before we really begin to speculate on the form and function of our Flora of the Future, we must first take a look to the current cutting edge of biodiversity informatics. In what must be one of the most significant advances in decades, the cooperative development of the Global Biodiversity Information Facility (GBIF) by many governments and organisations has promoted and facilitated the “mobilization, access, discovery and use of information about the occurrence of organisms”. This centralized repository of earth’s biodiversity is fast set to reach one billion indexed records within a few years from now, fed from diverse sources ranging from individuals to national biodiversity data centres. It is difficult to envisage how the Flora of the Future could in any plausible way side-step such a global network. Whereas floras have traditionally featured a top-down, expert driven synthesis – the Flora of the Future will also no doubt integrate the emergent trend of bottom-up assembly of knowledge – a good example of which is currently purveyed by the Encyclopaedia of Life.

Let’s get back now to our future ecologists and biodiversity practitioners, and take a little look in as they go about conducting their fieldwork. No matter what habitat or location they study in worldwide, they will each possess a small handheld device connected to the Flora of the Future. Automation of species identification by means of this device will have removed a large bottleneck in their work – leaving ecologists to focus on actual ecology. No longer will they be bound to a particular geographic territory due to limited floristic familiarity –  we will witness a complete opening of boundaries, and greater migration of ‘western’ ecologists to the frontline of areas of global biodiversity importance.

But just how exactly could such a device work? A potential basis could feature a combination of machine-learning morphometrics and DNA barcoding  – two presently very promising tools. For the former, development of algorithms for auto-identification of plant species is already well underway (see for example the Leafsnap mobile app). These function much like facial recognition technology, and through input of a digital scan/photo can pinpoint unique morphological characteristics required for successful classification. A key aspect of machine learning is removal of subjectivity by conversion of shapes into numerical descriptions – no need for argument any longer on just how ‘subglobose’ a feature is; the ball is already in motion towards a predictive and integrative taxonomy. Upon scanning a specimen in the field, an image will be broken down into key morphometric characteristics, and referenced against a large central database within the Flora of the Future. The Flora will prioritize this procedure by first referencing against species known to occur within a certain radius from where the user currently stands (a useful feature in itself!). The ecologist, on the spot, may learn that the specimen has a confirmed match, and proceed to download key local statistics of importance. On the other hand, this specimen may in fact represent an extension of the species known distributional range. The finding, however, of no known match in the database could spell discovery of a new species, whereas a positive match with notably low morphometric agreement may indicate new subspecific taxa or otherwise interesting findings (for which DNA barcoding could be employed for further verification in both cases).

Regardless of outcome, the above three scenarios will have allowed for a real-time and in situ solution to identification of species. The exact significance of this process will not only lie in the freeing up of both ecologists’ and taxonomists’ resources, but in the real-time flagging of new discoveries. As it stands, it is expected that discovery of remaining undescribed plant species will be an incredibly inefficient process (given that 50% of the world’s plant species have been discovered by only 2% of plant collectors), despite the vast number of these thought to exist. A recent study examining the exact inefficiency of the production chain from collection to publication uncovered that “on average, more than two decades pass between the first collection of samples of a new species and the publication of the species’ description in scientific literature”. In other words, a specimen of a new species has physically passed through the hands of many people before the simple ‘discovery’ (perhaps after many, many years in a herbarium) that it is something new to science. In this sense, an important function of the Flora of the Future will be instant recognition (perhaps even while standing in the field!) of a new discovery as just that – which can drastically reduce this presently overblown timeframe and waste of resources.

Getting back to the future for now, we see our biodiversity practitioners and ecologists as key players in the advancement of ecological as well as taxonomic discovery, with a highly efficient yet passive ability for discovery embedded within the commonplace tools they use, as they go about their work.  With an entirely streamlined approach to field research, and identification no longer a daunting prospect in the study and documentation of biodiversity, we will eventually see the peak of mass extinction pass, looking back behind us. The challenges of tomorrow are no doubt great, and a renewed vigour for the taxonomic process will be critical for progress on these fronts. The Flora of the Future will for the first time sew a seamless line between ecologists and taxonomy; the essential currency of biodiversity.

Author

Paul Egan: eganp5[at]tcd.ie

Photo Credit

Paul Egan

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Academic CVs: Dos, don’ts and maybes

AlCaponemugshotCPD

At a recent session of NERD club, our weekly research group meeting for the Networks in Ecology/Evolution Research Dynamic, we discussed academic CVs. Four academic staff members (including myself) showed their CVs to the group and discussed what was in them. This was interesting because we all had such varied opinions! I thought I’d write a short blog post to highlight some of our main agreements and disagreements. Continue reading “Academic CVs: Dos, don’ts and maybes”

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Good-bye Guinea worm?

Dracunculus_medinensis

The media is all abuzz about the Carter Centre’s recent announcement that 542 cases of guinea worm infection were reported in 2012. That is a remarkable achievement, considering that 3.5million cases where the reported when the Carter Centre began their eradication programme in 1986. The guinea worm (Dracunculus medinensis) is a particularly gruesome parasitic nematode that causes painful and debilitating disease. It is one species no one will be too sorry to see go. Well no one except the folks at the (tongue in cheek) Save the Guinea worm Foundation.

Perversely, considering our track record of causing extinctions, actually trying to get rid of a species can be extremely difficult. Targeted eradication of disease in humans has been successful only once before, with small pox. That required a massive and expensive vaccination programme and it is unlikely that the mandatory aspect of the vaccines would be tolerated today. However, helminths are a different beastie altogether.  Helminths (parasitic worms) differ from pathogens in that, with a few exceptions, they don’t multiply within human hosts or have direct transmission. Helminths require a period of passage through the environment, either as infectious eggs or through other intermediate hosts. The guinea worm life cycle involves water fleas (Cyclopidae) as intermediate hosts.  Water containing infected water fleas is drunk and the parasites are released. After about a year of maturation, females emerge via a painful skin blister, which erupts on contact with water, releasing thousands of larvae ready to continue the cycle.

The peculiarities of the life cycle meant the eradication programme was successful, not though vaccination or medication, but through changing people’s behaviour in the key areas of transmission and infection.  To prevent infection people were taught about the need to filter drinking water, particularly standing water where cyclops abound. The burning sensation caused by the female worm emerging meant people often cooled the blister in a nearby pond, usually the same the one that supplied drinking water.  By educating about the link between this behaviour and infected ponds, transmission of the larval stages was successfully reduced.

Of course, various other aspects of the guinea worm life cycle played a part. Cyclops is a relative large (1mm) so filtering material could be made and supplied cheaply. They are also immobile; once an infection is eradicated from an area it is easier to keep it out than in diseases like malaria. Unlike helminths that release eggs and larvae through the intestinal tract, people shedding guinea worm infectious stages are much more likely to be identified quickly.

One important factor influencing the success of small pox eradication was that the virus had no hosts other than humans. There is no wildlife reservoir from which the disease may re-emerge. Guinea worms on the other hand have been found in cats, dogs and cattle, though none appear to act as a reservoir for human infection. It may, therefore, be more correct to speak of elimination of human guinea worm infections rather than total eradication of the species. Save The Guinea Worm Foundation will be pleased.

Author

loxtonk[at]tcd.ie

Photo credit

wikimedia commons