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By Stephen Luntz

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Earthquake Danger Zones Identified

Most of the world’s largest earthquakes are concentrated where subduction zones and fracture zones intersect, marking a major step forward in predicting the locations of future disasters.

Earthquakes capable of causing major tsunamis occur where an oceanic plate is subducted under another plate, but some parts of the plate boundary are far more prone than others. While the historical record identifies some danger zones, the largest quakes can occur when pressure has built up over hundreds or thousands of years.

“The advantage of our new method is that it picks up many of the regions prone to recurring powerful earthquakes over long time periods, including some where no large earthquakes have occurred in the last 100 or so years. Our results could contribute to much-needed improvements of long-term seismic hazard maps,” says Prof Dietmar Müller of the University of Sydney’s School of Geosciences.

Fracture zones extend from transform faults along mid-ocean ridges where the ridges have been offset. Müller first recognised the possibility of a link when the Tohoku-Oki earthquake occurred off Japan in 2011.

“I thought journalists might start calling me to ask what caused it so I started looking at maps of the area. The first thing I noticed was there was a huge fracture zone which had been well mapped by Japanese geophysicists intersecting the subduction zone right near where the quake happened.” The last large quake at this location was over 1000 years ago, so the area was considered safe enough to house nuclear power stations.

Müller’s team had recently completed a map of global oceanic fracture zones using satellite data of gravitational fields, and used this to examine undersea earthquake data. The results were published in Solid Earth.

Fracture zones represent one-quarter of subduction zones and a similar proportion of smaller subduction earthquakes. However, “we found that 87% of the 15 largest (8.6 magnitude or higher) and half of the 50 largest (8.4 magnitude or higher) earthquakes of the past century are associated with areas of intersection between oceanic fracture zones and subduction zones,” Müller says. These include the calamitous 2004 event that triggered the Indian Ocean tsunami.

While uncertain of the explanation, Müller thinks that “large ridges form obstacles to subduction. Instead of stress being released in multiple small events, it builds up.”

Müller believes that the association has not been noticed before because, while work has been done on earthquakes along the Chilean and Sumatran fracture zones, no one has looked at the global picture. “Most seismologists work on continents and rarely look at the oceanic side of the equation,” he says. “Marine geophysicists look at features on the ocean floor and the two communities don’t talk.”

Subduction zones in the western Pacific are free of fracture zones, but the sea floor west of the US/Canadian border looks to be far more dangerous than previously recognised. Müller says likely hotspots should be examined for evidence of prehistoric earthquakes, and infrastructure may need to be designed to deal with the threats.

Falkland Wolf Explained

For centuries the Falkland Islands wolf has puzzled zoologists, including Charles Darwin. As the only land-based animal on the islands, the mystery was how the wolf got there. Now Adelaide scientists think they have the answer.

Early sailors described the wolf as living on nesting sea birds, penguins, seals and sea lions. “The islands at the time hosted the richest colonies of sea birds in the world,” says Prof Alan Cooper of the Australian Centre for Ancient DNA (ACAD) at Adelaide University.

Some speculated that the wolf had once been domesticated and left behind by visitors from South America. However, visits to the islands prior to the 16th century are debated.

DNA comparisons between the wolf and its closest living relative, the South American maned wolf, suggest that the two diverged seven million years ago, deepening the mystery.

“Critically, however, these early studies hadn’t included an extinct relative from the mainland, the fox-like Dusicyon avus,” says Dr Julien Soubrier of ACAD. Using D. avus DNA and a more appropriate molecular clock, Soubrier and Cooper concluded that separation occurred just 16,000 years ago, although Cooper says there is an error range of 7000 years on either side of this date.

Even at the height of the ice age the Falklands were never connected by a land bridge to the mainland. “The Eureka moment was finding evidence of submarine terraces off the coast of Argentina,” says Cooper. These would have led the wolf to a strait around 20 metres wide, which may have had temporary ice bridges across it.

Cooper speculates that the wolf crossed this strait “probably while pursuing marine prey like seals or penguins. Other small animals like rats weren’t able to cross the ice.”

Cooper says there is no evidence the islands were glaciated, even at the height of the ice age.

The most recent possible date for the wolf’s separation from mainland species, 9000 years, overlaps with the arrival of humans in South America. However, Cooper considers it unlikely that the islands were visited by people soon after arriving on the mainland.

The study was published in Nature Communications using a specimen collected by Darwin and another recently re­discovered in the Otago Museum attic. No studies were possible on living Falkland Island wolves, as the species was hunted for fur before extinction was confirmed following poisoning by sheep farmers.

World’s Rarest Whale Beached

The first complete specimens of the spade-toothed whale have been identified after a mother and calf became stranded on Opape Beach in the Bay of Plenty on New Year’s Eve 2010.

“It’s incredible to think that, until recently, such a large animal was concealed in the South Pacific Ocean, and shows how little we know about ocean biodiversity,” says Dr Rochelle Constantine of the Leigh Marine Laboratory at the University of Auckland.

The existence of the spade-toothed beaked whale was first discovered in 1872 from skull and jaw fragments on Pitt Island, New Zealand. In 2002 DNA analysis linked that discovery with two others from New Zealand and Robinson Crusoe Island, Chile, suggesting that the species habitat lies in the South Pacific.

The spade-toothed whale is very similar to Gray’s beaked whale, but Constantine says the two have clear genetic differences, as well as somewhat different colouring. “The main difference is the shape of the tooth,” she says. “The tusks that erupt in males are different in all the beaked whale species. This has a nodule on the end. However, observing this relies on finding a mature male.”

Consequently identification of the mother and calf had to wait for genetic testing, which was announced in Current Biology.

“We don’t know anything about them, since they have never been seen alive,” Constantine says. “We imagine they inhabit deeper waters and feed on squid – that’s typical for beaked whales.”

She doubts the rarity has human causes, as the species they resemble were not hunted in the South Pacific, although Northern Hemisphere equivalents were not so lucky.

However, some species of beaked whales are showing increases in toxic chemicals that are becoming bioaccumulated through the food chain.

New Zealand has a network for reporting and studying whale strandings, and Constantine hopes that other nations will follow so that future beached whales, which might initially be misidentified as more common species, are subjected to DNA checking.

Early Stimulation Assists Parkinson’s Patients

Scientists at one of the world’s leading centres for deep brain stimulation have welcomed evidence of the benefits of early treatment for sufferers of Parkinson’s disease.

Deep brain stimulation (DBS) involves the implantation of electrodes within the brain to deliver high frequency pulses, but Prof Peter Silburn of the Asia-Pacific Centre for Neuromodulation at the University of Queensland says the mechanisms for its success are not well-understood.

Steady frequency electrical pulses compensate for the abnormal electrical discharges that occur in parts of the brain when dopamine-producing cells are lost. “Stimulation at 130 Hz helps people’s walking,” says Silburn, “but at a different frequency it sends them to sleep”.

Like any brain surgery, the implantation of the electrodes is not without risk, so DBS is usually used only when other medications produce severe side-effects in patients or have ceased to work. However, a study published in the New England Journal of Medicine investigated the effect on patients who had been experiencing Parkinson’s symptoms for an average of 7.5 years and were still benefiting from oral medications.

Among this group 26% reported an improvement in their quality of life after the surgery and 53% said their motor skills had improved, despite the fact that 39% reduced their medication. A control group saw a slight increase in their intake of medicines, and with it a worsening of side-effects over the same period.

“This study has confirmed the best medical practice for a person with Parkinson's disease is to perform DBS surgery around 4–7 years into the condition, as opposed to waiting until the medications stop working,” said Silburn.

The Asia-Pacific Centre is a training centre for DBS surgery and one of the world’s top five centres in the field. Silburn warns: “If you’re only doing one implantation a month you shouldn’t be doing any.” He says surgeons who lose practice at DBS implantations sometimes miss the requisite areas of the brain, giving the surgery a bad reputation.

“The good thing is that mistakes are fully reversible,” says Silburn. However, the side-effects from a misplaced electrode can be severe until a correction is made, and the need for a second round of surgery doubles the risk of infection.

Uterine Protein Fights STIs

A newly discovered protein produced in the uterine lining appears to protect women against chlamydia and herpes.

Prof Paul Hertzog of the Monash Institute of Medical Research published the discovery of the protein, dubbed interferon epsilon, in Science. He has shown that mice without interferon epsilon are particularly vulnerable to the two diseases. Moreover, levels of the protein in women’s reproductive tracts fluctuate based on the same factors as in mice, being bolstered by oestrogen and suppressed by progesterone.

For obvious reasons no testing has been done to confirm the hypothesis that women are also protected by interferon epsilon, but Hertzog says: “Circumstantial evidence suggests women are more susceptible to STIs at times when oestrogen drops, such as menopause or when progesterone is high.”

The findings suggest that the progesterone-only mini-pill may increase the risk of sexually transmitted infections (STIs).

Production of interferon epsilon is switched off during pregnancy, but Hertzog says: “It is not the only aspect of the immune response turned off at this time”.

Interferon epsilon does not directly bind to bacteria or viruses. Instead it bolsters the immune system, suggesting that its benefits may apply more widely, including against HIV. However, Hertzog says that mouse models are non-existent or less reliable for other STIs.

So far Hertzog’s team has found no evidence of interferon epsilon’s existence in men.

Eighty thousand Australians are diagnosed with chlamydia each year, and infection rates are likely to be much higher. Hertzog says it is not clear to what extent women become infected because interferon epsilon levels are suppressed or whether higher levels of the protein provide only partial protection.

Interferon epsilon’s unusual production method may throw light on the immune system more generally. “Most proteins protecting us against infection are produced only after we’re exposed to a virus or bacteria,” says Hertzog, “but this protein is produced normally, and is instead regulated by hormones.

“The most straightforward way to increase interferon epsilon levels is to deliver it, since we have shown we can manufacture it,” says Hertzog. “There may also be indirect methods, such as through hormones. We need to find the molecules that turn production on and off.”

While this is likely to be a long process, Hertzog hopes that “diagnostic or predictive” tests may be available sooner that would alert women to their vulnerability to infection.

Acute Toxoplasmosis Can Be Serious

Toxoplasmosis, a diseases spread by cats and uncooked meat, can have a more severe acute stage than previously recognised according to A/Prof Mark Thomas of the University of Auckland’s Department of Molecular Medicine and Pathology.

Chronic toxoplasmosis has achieved some coverage recently. The protozoa that cause the disease can infect the brain, and there is evidence linking it to depression, schizophrenia, postnatal depression and risk-taking behaviour. Acute toxoplasmosis, occurring in the first weeks or months after infection, is considered serious when combined with HIV infection, but has been largely dismissed otherwise.

“In its acute phase the disease has usually been seen as benign, trivial and self-healing,” says Thomas. However, when 31 patients were sent a questionnaire, 90% reported fatigue lasting an average of 6 weeks, 74% suffered from headaches, 52% lost concentration and the same number had aches, while more than one-third reported fever. “Most respondents reported that these effects had a significant impact on their overall physical and mental health,” says Thomas.

The study was conducted on people whose symptoms were serious enough to cause them to see a doctor, and Thomas admits this may not be typical of the 40% of New Zealanders estimated to experience toxoplasmosis in their lives. Nevertheless, Thomas says the study, published in the Scandinavian Journal of Infectious Diseases, is new in finding widespread significant effects.

Many cases of acute toxoplasmosis are probably going undetected. Thomas says the symptoms of fatigue and swollen lymph glands are usually first suspected to be glandular fever. “If the test for the Epstein-Barr virus comes back negative some doctors will then test for antibodies of toxoplasmosis in the blood, or take a biopsy from the lymph glands,” he says. “However, many will never be tested. There were 130 positive diagnoses in Auckland last year.”

Treatments exist for the chronic form of the disease, although these are usually only used in the face of compounding circumstances. “No one has done a controlled trial of the benefits of antibiotics in the acute phase because it has been seen as a trivial disease,” Thomas says. “Our work may change this.”

No vaccine currently exists, but increasing evidence of the seriousness of the consequences may spur the quest for a cure.