Bat vs. Marburg virus: A Seasonal Struggle

Posted on 5 November 2012 by mmmbitesizescience

Marburg is a highly infectious virus from the family Filoviridae (which includes Ebola virus), and is associated with a high fatality rate (~90%) and severe haemorrhagic symptoms. Originally described in simultaneous outbreaks in Germany and Serbia in 1967, it is now confined to sub-Saharan Africa, including Uganda, Zimbabwe, Kenya and Angola. Infections are sporadically reported, and are often identified in mine workers or tourist’s who have reported visiting caves. In 2007, a natural animal reservoir of Marburg virus was identified in the Egyptian fruit bat, Rousettus aegyptiacus. Due to the curiously spotty nature of infections, researcher’s from nine different disease control centres collaborated to find out what ecological factors might influence virus spillover from bats into the human population. They focussed their analysis on one location: Python Cave in Queen Elizabeth National Park, Uganda. 40 out of the 1622 bats they captured (2.5%) were infected with Marburg virus: since the cave has an estimated total population of 40,000, this corresponds to 1000 actively infected bats at any one time, meaning a low level of infectious virus is constantly in circulation. Young bats (6 months of age) were especially susceptible to infection during two periods of the year, and these times roughly corresponded with historical episodes of Marburg virus outbreaks. Thus, seasonal fluctuations of infection are associated with young bat populations, and probably represent periods of increased public health risk.

You can read the full original research article for free here.

 

Amman BR, Carroll SA, Reed ZD, Sealy TK, Balinandi S, Swanepoel R, Kemp A, Erickson BR, Comer JA, Campbell S, Cannon DL, Khristova ML, Atimnedi P, Paddock CD, Kent Crockett RJ, Flietstra TD, Warfield KL, Unfer R, Katongole-Mbidde E, Downing R, Tappero JW, Zaki SR, Rollin PE, Ksiazek TG, Nichol ST, & Towner JS (2012). Seasonal Pulses of Marburg Virus Circulation in Juvenile Rousettus aegyptiacus Bats Coincide with Periods of Increased Risk of Human Infection. PLoS pathogens, 8 (10) PMID: 23055920

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Fresh air is good for your brain

Posted on 24 October 2012 by mmmbitesizescience

Breathe in. Then breathe out. This wonderful process of ventilation keeps us alive: an inhalation of oxygen helps our cells generate energy, while an exhalation of carbon dioxide removes their waste products. Carbon dioxide, or CO2, has something of a shaky reputation, since it is not only produced by normal biological activity, but also through the burning of fossil fuels: it is a greenhouse gas and therefore has a role in climate change. While international efforts continue to regulate outdoor CO2 levels in anti-global warming measures, indoor CO2 concentrations are also strictly regulated by occupational health and safety laws, with a recommended cap at a steady state of 870 parts-per-million (ppm). Human health is affected at high CO2 concentrations (over 20,000 ppm), and exceedingly high concentrations (over 250,000 ppm) will kill you.

Researchers at the State University of New York and the Lawrence Berkeley National Laboratory in California wanted to study how increased levels of indoor CO2, such as those found in buildings where there is a drive to minimise energy consumption by reducing ventilation rates, might affect human decision-making capabilities, since brain function is affected by CO2 levels in the blood. The team injected ultrapure carbon dioxide into an office-like chamber where participants were completing computer-based tests. They used three different CO2 concentrations – 600, 1000 or 2500 ppm – all of which fall within normal ranges. Baseline performance scores at 600 ppm were average or above average, but when CO2 concentrations increased to 1000 or 2500 ppm, significant effects were evident: most decision-making performance variables tested, such as the use of initiative and task orientation, showed a decline, in some cases dipping as far as a real dysfunction. This study highlights the potentially economically-significant need for good ventilation in all indoor spaces, especially those where brain function is vital, such as in classrooms and government buildings.

Read the original research article here.

Satish U, Mendell MJ, Shekhar K, Hotchi T, Sullivan D, Streufert S, & Fisk WB (2012). Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance. Environmental health perspectives PMID: 23008272

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The death of well-fed salt marshes

Posted on 19 October 2012 by mmmbitesizescience

Salt marshes are important ecosystems that form a dividing line between land and sea. They are typically structured as a mud or sand flat that is colonised by salt-tolerant plants that can cope with being submerged twice a day, such as grasses, herbs and low shrubs. Their positioning forms an effective natural barrier that protects coastal cities from storm damage. They also have important environmental functions, supporting fisheries and sequestering carbon: essentially, storing carbon dioxide away in an immobilised form that prevents it from contributing to climate change. In fact, salt marshes are second only to tropical rainforests for the speedy rate at which they can do this. Salt marshes also form the cosy homes of numerous wildlife species, including fish, birds, crustaceans, worms and insects.

The loss of coastal salt marshes has proceeded rapidly in recent years, with global estimates of disappearances between 25-50%. Rising sea levels are generally known to contribute to this loss, but more specific local reasons are less clear. One new study analysed if an influx of nutrients, consistent with agricultural fertilisers leaching into water sources, could contribute to this process.

Over a period of 9 years, the team added nitrates twice a day during high tide into a test marsh landscape (the Plum Island Estuary, Massachusetts, USA) and observed how the overall ecosystem changed. This addition of extra nutrients, a process known as eutrophication, led to salt marsh integrity being undermined: more organic matter decomposed, plant water content was higher, plant roots grew less and some plants fell over. The combination of these changes led to tidal currents being able to degrade the low marshland, and without this low marsh support, the integrity of the high marsh subsequently failed.

This research suggests that as the human population continues to rise and food production increases to compensate, efforts must be made to protect salt marshes, which provide important ecological benefits.

You can read the original research article here.

Deegan LA, Johnson DS, Warren RS, Peterson BJ, Fleeger JW, Fagherazzi S, & Wollheim WM (2012). Coastal eutrophication as a driver of salt marsh loss. Nature, 490 (7420), 388-92 PMID: 23075989

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Tomarto or Tomehto: both are good against strokes

Posted on 16 October 2012 by mmmbitesizescience

I used to absolutely hate tomatoes when I was young. In fact, I remember smuggling them out of my packed lunch and into my favourite dinner lady’s obliging mouth during my primary school days. As I got older, I saw the error of my ways: the deliciousness of Heinz tomato soup saw to that. And a good job, too. Tomatoes have a long list of healthy contents, including antioxidant carotenoids like lycopene, as well as polyphenols, folic acid and vitamins C and E.

Tomatoes (or what’s in them) have previously been championed as sensible dietary inclusions in the prevention of prostate cancer. Now, a team of researcher’s in Finland have shown that men who consume more tomatoes and tomato-based products have a lower risk (55-60%) of suffering a stroke. They followed how blood levels of carotenoids, including lycopene, alpha/beta-carotene, retinol and alpha-tocopherol, changed in more than 1000 men over a period of 12 years, and how many of those men had strokes during that time. They identified that the presence of one active tomato ingredient, lycopene, at high levels had a significant effect on decreasing stroke incidence. Lycopene has lots of beneficial effects: it is one of the most highly effective carotenoid antioxidants, scavenging free radicals out of the body, which would otherwise get up to such mischiefs as mutating DNA and killing cells. It is also anti-inflammatory and able to boost immune function. This research supports the idea that eating a diet rich in fruit and vegetables can protect against disease.

Adding a little more lycopene into your diet is easy. Tomato ketchup is one processed source, in a nice, concentrated format. Pink grapefruit, watermelon, papaya and red peppers are also lycopene-rich (and happily tasty).

Read the original article describing this research here.

Karppi J, Laukkanen JA, Sivenius J, Ronkainen K, & Kurl S (2012). Serum lycopene decreases the risk of stroke in men: A population-based follow-up study. Neurology, 79 (15), 1540-7 PMID: 23045517

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New painkillers from black mamba venom?

Posted on 3 October 2012 by mmmbitesizescience

After being bitten by a poisonous snake, you can probably imagine that having a good amount of venom coursing through your veins is a pretty painful process. And indeed, that is the case with many snakes, such as the Texas coral snake, whose venom contains toxins that activate pain receptors – an excellent method of warding off predators. However, the venom from the black mamba, Dendroaspis polylepis, has now been shown to contain a new class of peptides, brilliantly named, ‘mambalgins’, that actually block pain (which you may consider to be a good thing when you are being slowly consumed and digested by a black mamba). These mambalgins work by blocking both peripheral pain receptors and central neurons, and have a potent, rapid analgesic effect similar to morphine, but without the less-than-ideal side effects of being highly addictive and inducing respiratory distress. They may, therefore, have value as a novel class of naturally-occurring painkillers.

Read the original article describing this research here.

Diochot S, Baron A, Salinas M, Douguet D, Scarzello S, Dabert-Gay AS, Debayle D, Friend V, Alloui A, Lazdunski M, & Lingueglia E (2012). Black mamba venom peptides target acid-sensing ion channels to abolish pain. Nature, 490 (7421), 552-5 PMID: 23034652

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