We’ll have no bananas?

BananasReports of the imminent demise of the world’s most popular fruit have surfaced repeatedly over the course of the last decade. Bananas, particularly those grown in large monocultures for the hungry markets of the EU and the US, are vulnerable to a number of diseases, and fears are mounting that the tide is turning against our prevention and mitigation strategies. How much stock should we put in these reports – are the days of the banana truly numbered? Jon Fuhrmann investigates.

A fungal disease called Fusarium wilt, also known as Panama disease, is causing the most concern among banana producers. In the last 20 years, a new and particularly dangerous strain called Tropical Race 4 (TR4) has infected the Cavendish banana, the only widely available banana type in western supermarkets. Reports of the disease are now coming in from the Middle East and East Africa, a long way from the disease’s Southeast Asian origins.

Panama disease itself is not an unknown entity. In the first half of the 20th century, a different strain (Race 1) effectively wiped out the Gros Michel-type banana, which dominated the world markets at the time. Those who have tasted Gros Michel wax lyrical of its superior taste and texture, sweeter and more delicate than the Cavendish-type bananas we buy in supermarkets today.

Indeed, the Cavendish bananas are merely a second-best solution, adopted after Panama disease rendered Gros Michel commercially infeasible. The big banana exporting companies clung to Gros Michel because consumers preferred the taste and their hardiness meant lower transport costs compared to those needed for the Cavendish fruit. While possibly apocryphal, the song ‘Yes! We Have No Bananas’ may relate to the difficulties that American consumers faced after Panama disease destroyed the Gros Michel crops that supplied the US.

As a result, Cavendish bananas, which are resistant to the fungus, became the bulk of worldwide trade and have remained so for the past sixty years. During this time, a variety of bacterial and fungal diseases have plagued banana plantations and prompted ever more extreme levels of fungicide spraying, which affects both plants and plantation workers – but Cavendish continues to dominate.

Tilting at windmills

In the early 1990s, a new strain of Fusarium wilt was discovered in Southeast Asia and christened tropical race 4 (TR4) due to its prevalence in tropical regions. Cavendish bananas are highly susceptible to TR4, which is resistant to fungicides and spreads rapidly through a plantation after initial infection. The fruit are unable to evolve resistance to the fungus because all Cavendish bananas are genetically identical and grown from a homogenous seed stock.

Confined to Southeast Asia and the Pacific region for the best part of a decade after its discovery, TR4 did little harm to the West African and Latin American plantations supplying western markets. In the last decade, however, reports of the disease have appeared from Oman, Jordan and Mozambique. The disease is clearly on the move – but how did it spread over such large distances so suddenly? Unsurprisingly, human action is the probably to blame. Workers, machinery and plant material all move between banana-producing regions, and contaminated soil on tools or boots can introduce TR4 to new regions.

The end of Cavendish?

It is unlikely that TR4 will cause Cavendish-type bananas to become extinct – although it may cause significant problems to the huge monocultures in which the plants are grown, as was seen with Gros Michel. Fusarium wilt spreads rapidly through adjacent plants but is not easily spread over large distances like some other air- or waterborne pathogens such as Phytophthora ramorum, which causes sudden oak death. This means that smallholders are much more likely to be able to grow Cavendish bananas even if the larger export market is in decline. Again, this is true of the Gros Michel variant, which can still be found in marketplaces in Southeast Asia.

Of course, there is a chance that Cavendish bananas will become commercially infeasible if TR4 continues to spread through Africa or reaches the Americas. To prevent this, stringent controls are needed to halt the spread of the fungus. Examples of this exist in Australia, where the state of Queensland has implemented strict biosecurity measures and has so far managed to keep Fusarium wilt at bay despite its prevalence in the adjacent Northern Territory. It may prove more difficult to enforce such measures across the multiple borders present in Latin America.

Are there alternatives?

While Cavendish is by far the most common banana used in export, there are a large number of other banana varieties cultivated around the world. These bananas feed millions of people around Asia and Africa, and scientists are testing them to find which ones are resistant to TR4. This means that while Cavendish is, of course, an important food crop in many parts of the world, its disappearance from mass production is unlikely to cause a food security crisis in low- or middle-income countries, as alternatives are available.

As for western countries importing bananas, the situation is less straightforward. While the precedent of Gros Michel’s fate in the 20th century gives us some idea of a potential outcome, the difference is that when Gros Michel became infeasible, the Cavendish variety was already known as a potential replacement. Currently, there is no such replacement for Cavendish.

Mitigating the Musa menace

While many researchers think it likely that TR4 will eventually spread to the Americas, delaying this event allows more time for effective countermeasures to be put in place and for research to continue on resistant banana varieties.

For Western consumers and exporting companies, the task at hand is twofold. Scientists are working to develop resistant varieties that display as many of Cavendish’s positive attributes as possible. While a few such Cavendish-based varieties have been made, they either require prohibitively expensive modifications to the transportation process or are unlikely to be accepted by consumers because their shape or taste are too different.

Additionally, consumer tastes will have to change if a new kind of banana is to find widespread acceptance and commercial success. It may be that the banana of the future will be a different average size or shape, or that it ripens differently so that greener or browner bananas become more common on supermarket shelves.

Fortunately, it seems unlikely that bananas will be lost forever. As the downfall of Gros Michel shows, even a crash in the world’s most grown banana will not lead to a complete demise of the fruit. Research, information dissemination and appropriate management can combine to produce a brighter future for bananas.

Jon Fuhrmann

The Society has recently produced a briefing document on banana disease, which further outlines the problems facing banana growers. You can find it here.

Image credit: Ian Ransley on Flickr
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New to Science: July 2014

BambooEach month, the Society for General Microbiology publishes the International Journal of Systematic and Evolutionary Microbiology, which details newly discovered species of bacteria, fungi and protists. Here are a few of the new species that have been discovered, and the places they’ve been found. The full papers are available to journal subscribers, but the abstracts are free to read.

While summer is well and truly upon us in England, many of us are staying in to watch the plethora of fantastic sporting events that are keeping us glued to our television sets. While Wimbledon and the Tour de France brought numerous world-class athletes onto British soil, the football World Cup in Brazil will nevertheless remain the focal point of global attention until its conclusion on Sunday 13 July.

Despite the proceedings in the country’s stadia, Brazilian scientists remain hard at work cataloguing our planet’s microbes. In the Amazon rainforest, researchers from Rio de Janeiro teamed up with colleagues from Belgium and Australia to identify Bradyrhizobium manausense in cowpea, an important food crop in the area. The new species is named after Manaus, the biggest city in the Amazon rainforest (and the site of England’s defeat to Italy in the World Cup). Continue reading

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Opinion: The Longitude Prize and antibiotic research funding

methicillin-resistant Staphylococcus aureus and a dead human neutrophilCash prizes have long been the drivers of scientific innovation, be it in the development of synthetic blue pigment in 19th century France, or the XPrize’s continuing efforts to award those developing “radical breakthroughs for the benefit of humanity”.

This year, Nesta relaunched the Longitude Prize, first offered by the British Government in 1714 as a reward for solving a major problem of the day – determining a ship’s longitude. The original prize was won by the clockmaker John Harrison, who received around £15,000 for his efforts, which equates to over £1.8 million in today’s currency.

300 years later, the reborn 2014 Longitude Prize is even bigger – offering a fund of £10 million to those interested in solving the major problems that affect mankind today. The prize opened with a vote that allowed the public to decide which challenge they thought was most deserving. As Chief Executive of the Society for General Microbiology, I’m delighted to say that the winning challenge of the Longitude Prize 2014 is ‘Antibiotics’.

The prize’s website says the fund aims “to create a cost-effective, accurate, rapid, and easy-to-use test for bacterial infections that will allow health professionals worldwide to administer the right antibiotics at the right time.”

This mirrors a call made in the Society for General Microbiology’s recent report Microbiology and the challenge of sexually transmitted infections, in which we state that the development of rapid point-of-care diagnostic devices will have a major impact in slowing the spread of antimicrobial-resistant bacterial infections, some of which – for example, gonorrhoea – threaten to become resistant to all available drugs and, ultimately, untreatable. Continue reading

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From Poo to Papillomavirus: Peculiar Penguin Pathogens

Adélie penguinsResearchBlogging.orgPenguin poo has seen a surprising range of scientific applications, from a comprehensive census of emperor penguins from satellite data to a calculation of the rectal pressures required to avoid defecating into their own nests; the latter research, unsurprisingly, even won the 2005 Ig Nobel Prize in fluid dynamics. More recently, the droppings of Adélie penguins were studied from a different angle in research published in the Journal of General Virology. Dr Arvind Varsani, a virologist at the University of Canterbury in Christchurch, New Zealand, isolated a previously unknown species of virus from these droppings and produced the first fully identified genome of any penguin-associated virus.

So far, we have only scratched the surface of the world of viruses. While we are aware of a significant proportion of mammal and reptile species, we only know an estimated 1% of all virus species – and within this 1%, most research focuses on viruses that cause disease in humans, certain animals and plants. The new virus Dr Varsani and his team discovered in the Adélie droppings is a species of papillomavirus. This is a large family of more than 270 virus types, over 160 of which infect humans; some of them are benign, while others can cause warts on various parts of the body or even cause cancer. The remaining 100-odd strains are found in a wide variety of animals – mostly mammals and a handful of reptiles. However, the Adélie papillomavirus is only the fourth species known associated with birds. Continue reading

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Microbe Talk: June 2014

Keble_College_ChapelThis month on the Podcast, we sent Ben to Keble College at the University of Oxford, to attend a conference that celebrated the 50th anniversary of the first paper to detail the Epstein–Barr virus. The virus, also known as EBV, was the first virus shown to cause cancer in humans.

On the podcast this month:

Sir Anthony Epstein, who was one of the co-discoverers of EBV and published the first paper on the virus, in the Lancet in 1964.

Professor Paul Farrell (Imperial College London), who was an author on the first paper that detailed the genetic sequence of EBV.

Professor Jeffrey Cohen (US National Institute of Allergy and Infectious Diseases), who is working to develop a vaccine against the virus.

Show notes:

  • Information on the Epstein-Barr Virus via Wikipedia.
  • A great write up about EBV’s history on the CRUK blog.
  • Professor Farrell’s research page.
  • The Nature paper that first published the EBV genetic sequence.
  • Dr Jeffrey Cohen’s research page.

If you’re accessing this page on your iPhone and can’t see the podcast player, you can subscribe to Microbe Talk on iTunes.

Benjamin Thompson

Image Credit: David Iliff under CC-BY-SA
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New to Science: June 2014

2201055109_110087cbf3_zEach month, the Society for General Microbiology publishes the International Journal of Systematic and Evolutionary Microbiology, which details newly discovered species of bacteria, fungi and protists. Here are a few of the new species that have been discovered, and the places they’ve been found. The full papers are available to journal subscribers, but the abstracts are free to read.

As Londoners recover from sunburn sustained during last weekend’s summery weather, it is worth bearing in mind that this is far from the norm. Nowhere does this become more apparent than in salt production. For millenia, salterns have been used to evaporate seawater, leaving behind pure salt. In most countries, the heat from the sun is sufficient for this process, but in the UK saltwater is often boiled to facilitate evaporation when it is not sunny enough. Besides salt, salterns also contain a variety of microbes, including two that were newly discovered this month – Salinigranum rubrum in Gangxi, China, and Alkalibacillus almallahensis in Granada, Spain.

Microbes also flourish in other environments that most of us would consider decidedly unpleasant to live in. A French team, for example, discovered Methanococcoides vulcani in the Napoli mud volcano just off southern Crete. In Japan, Methanohalophilus levihalophilus was found living in a natural aquifer holding some 375 billion cubic metres of natural gas. Both these locations are extremely rich in methane, and given that a wide range of life forms live under similar environmental conditions, it comes as no surprise that scientists have speculated that methane-based life may exist in places like Saturn’s largest moon, Titan. Continue reading

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Ebola in West Africa

13717624625_cd5f3df570_zResearchBlogging.orgOver the past few months, there has been an unprecedented outbreak of the lethal Ebola virus in West Africa. Jon Fuhrmann tells us about the outbreak and efforts to control the virus.

Ebola virus disease (EVD) kills up to 90% of those infected, making it one of the deadliest diseases known to affect humans. It is so dangerous that it is considered a Grade A bioterrorism agent – on par with anthrax, smallpox, and bubonic plague. Dr Derek Gatherer, a bioinformaticist at Lancaster University, has documented the latest Ebola outbreak since its beginning in December 2013, when the disease re-emerged for the first time since 2001. Gatherer has published an Insight Review about it in the Journal of General Virology.

The current outbreak of EVD has seen confirmed cases in Guinea, Liberia and Sierra Leone, countries in an area of West Africa where the disease has not previously occurred. There were also a handful of suspected cases in neighbouring Mali, but these patients were found to have other diseases. As of this week, over 400 suspected cases of EVD have been recorded, with the majority of them in Guinea. The outbreak has currently resulted in over 200 deaths. However, these figures may continue to rise as more patients die and as test results confirm whether they were infected with Ebola.

The 2013 outbreak of Ebola virus disease is thought to have originated in Guékédou, Guinea. From here, it spread to the capital of Conakry as well as into nearby Liberia and Sierra Leone. Suspected cases in neighbouring Mali were found not to be EVD. Source: Wikipedia

The 2013 outbreak of Ebola virus disease is thought to have originated in Guékédou, Guinea. From here, it spread to the capital of Conakry as well as into nearby Liberia and Sierra Leone. Suspected cases in neighbouring Mali were found not to be EVD. Source: Wikipedia

Quick… but not painless

In part, Ebola is devastating due to its highly unpredictable nature. During the incubation period, which can last from a day to several weeks, the Ebola virus operates similarly to HIV, weakening the body’s immune system and allowing the virus to spread around the body. The initial symptoms are similar to those observed in many tropical fevers such as malaria and include high fever, headaches and muscle pains. This means that early-stage EVD is often mistaken for more common tropical fevers, delaying quarantine measures.

Most patients then develop a final, and almost always deadly, haemorrhagic stage. Victims will suffer from bloody vomit, diarrhoea and rashes all over their body, and may bleed from all orifices. Blood loss is usually so severe that it leads to multiple organ failure within a very short period of time. The haemorrhagic stage is caused by a mechanism called a ‘cytokine storm’, during which the immune system overreacts to the presence of a disease. This overreaction results in a massive overproduction of antibodies that clogs up the bloodstream, destroying small blood vessels and causing heavy internal bleeding throughout the body.

Furthermore, both those who die of EVD and the few who survive remain highly contagious for up to 40 days after falling ill. All their bodily fluids are infectious – saliva, blood, semen, faeces, even tears. In the cash-strapped hospitals of West Africa, it is very difficult to effectively quarantine patients for such long periods of time, meaning that the risk of further infection is high. This is also why EVD outbreaks cannot be considered to be over until no new infections have occurred for two months.

Too deadly to spread?

The one ‘advantage’, such as it is, of EVD being so dangerous is that its very lethality limits its ability to spread. The speed with which the disease incapacitates and kills most patients makes it unlikely to be spread through contact with other people. Compare this to the common cold or influenza viruses: these spread around the world frequently because people can still leave the house when they’re ill, unintentionally infecting others. This self-limiting nature of EVD may help lower the likelihood that a large-scale epidemic could occur.

Nevertheless, new cases of EVD are still being diagnosed in rural Guinea, including in parts of the country that were previously unaffected. Those infected are suspected to have contracted the disease when an acquaintance who was killed by the virus was buried without due care. This shows that the difficulties in controlling Ebola are considerable even in rural, sparsely populated areas with poor transport links. The outbreak has also spread from Guinea into eastern Sierra Leone following that country’s decision not to close its land borders.

While the disease appeared to have been contained in April in the Guinean capital of Conakry, two new cases were diagnosed in late May. An epidemic in such a densely populated transport hub with long-distance transport links could have catastrophic consequences. To fully contain the disease, health workers need to track down every single person an infected patient has been in contact with, everyone that these secondary individuals have met and so on – before necessary quarantine, testing and treatment can take place.

A ray of hope?

An effective public health response to Ebola is also limited by the fact that no known vaccine or medication is currently available. As with many tropical diseases, large pharmaceutical companies simply have no incentive to research and develop an expensive new drug for a disease which affects very few individuals on a global scale: there would simply not be enough demand. Since its discovery in 1976, EVD has infected only around 2,500 people, killing 1,700 of them.

For now, treatment is purely symptomatic, meaning that symptoms are addressed without actually destroying the Ebola virus itself. However, a small American company is now on the brink of developing a successful drug for Ebola, offering a glimmer of hope for the future. The drug, currently named BCX4430, has successfully cured EVD – as well as related tropical fevers – in mice and guinea pigs, and also cured every single infected monkey in the next round of trials. The drug is likely to enter the human trial phase next year, and if it is found to be safe it could be tested for efficacy during the next Ebola outbreak.

Unknown unknowns

Ebola is rare enough that we are still learning about it every time there is an outbreak. It is a terrifying disease by any measure, especially while we have no means to cure or prevent it. Credit must go to the health workers from around the world who are in West Africa working tirelessly to control the outbreak. Until an effective medication, and the means to distribute it are available, basic precautions, such as limiting physical contact and isolating patients are the only way to prevent the spread of this deadly virus.

Jon Fuhrmann

Gatherer D (2014). The 2014 Ebola virus disease outbreak in west Africa. The Journal of General Virology DOI: 10.1099/vir.0.067199-0

Image Credit: EU Humanitarian Aid and Civil Protection on Flickr
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