View previous topic | View next topic

Epidemiology

Page 1 of 5
Goto page 1, 2, 3, 4, 5  Next

dr.bob
151829.  Tue Feb 27, 2007 5:19 am Reply with quote

Apologies to Mat if he was planning on doing this, but his mention of it in the "E words" thread brought it to mind.

Q: What was John Snow's most important invention?
A: The science of epidemiology

Dr John Snow (as opposed to the Channel 4 news reader with an "h" deficiency) was a famous physician (1813-1858) who lived in Soho. The son of a labourer from York, he was apprenticed to a surgeon at the age of 14. His initial studies concerned toxicology and his first piece of scientific work was a study of the use of Arsenic to preserve dead bodies (although this research was abandoned "due to the toxic effects on the medical students").

Through toxicology he became interested in Anaesthesia and Cholera. At the time it was widely believed that Cholera was transmitted by "bad air" (the miasma theory), but Snow didn't believe that. In 1849 he published "On the mode of communication of cholera" which suggested that Cholera was a water-borne disease. The book cost him £200 to produce (at a time when his income was only £3.12s) but his ideas were generally dismissed. One reviewer wrote:

"There is, in our view, an entire failure of proof that the occurrence of any one case could be clearly and unambiguously assigned to water"

However, five years later Snow got the chance to prove his theory and write his place in the history books. There was an outbreak of Cholera in Soho in the summer of 1854. There were 13 water pumps in that area supplying water from wells. One of them had become contaminated by a leaking sewer. As people began to flee the area (75 percent of the population left in just a few days), Snow investigated and plotted the occurrences of the disease on a map. He found that the pump central to the outbreak was located on Broad Street (now Broadwick Street). Of the 89 people who died, only 10 lived closer to a different pump. A week after the outbreak had started, Snow got the authorities to remove the handle from the pump and the Cholera was stopped in its tracks.

Backing up Snow's water-borne theory of Cholera was the fact that, in the centre of the Soho Cholera outbreak, was a brewery on Broad Street itself. The 70 workers there were entirely unaffected by the disease because they were drinking beer from the brewery rather than water from the pump in the street.

By analysing the spread of the disease throughout the population, Snow invented the science of Epidemiology. Epidemiology is a branch of statistics and is defined as the study of the distribution, occurrence and spread of disease. Snow was able to use statistical techniques to conclusively prove that Cholera must be spread by infected water, even though he wasn't able to prove the exact method by which the disease was spread since the micro-organisms that spread the disease were undetectable at the time.

These days there is a pub in Broadwick Street called the John Snow commemorating this great event. The pub has a pink granite slab outside marking the original location of the pump which caused the outbreak. There is also a John Snow Society which collects facts and dates about the great man, and organises the "Annual Pumphandle Lecture Series". Their website says that international membership of the society is encouraged and that the only requirement is "that you visit the John Snow pub on any trip to London". I can't help thinking that we need more scientific societies that encourage people to go to pubs!

Snow was also a pioneer of anaesthetics, testing controlled doses of chloroform and ether on animals and humans thereby making these drugs much safer to use. In April 1853, he was responsible for giving chloroform to Queen Victoria at the birth of her son Leopold, and performed the same task in April 1857 when her daughter Beatrice was born.

Snow is now commemorated in the coat of arms of the Royal College of Anaesthetists:



He's the one on the left holding a copy of his work "On the inhalation of ether in surgical operations". The coat of arms is interesting in that it contains depictions of "morphia poppies" (which, as far as I can tell, are another name for opium poppies) and cocaine leaves. Possibly leading to the alternative question:

Q: Where would you find John Snow with some opium poppy heads and a bunch of cocaine leaves?


Sources:
http://www.bbc.co.uk/history/historic_figures/snow_john.shtml
http://www.johnsnowsociety.org/
http://www.makingthemodernworld.org.uk/learning_modules/geography/05.TU.01/?section=2
http://www.rcoa.ac.uk/index.asp?PageID=22

 
Gray
152804.  Thu Mar 01, 2007 5:33 pm Reply with quote

Heh - I like this. Must be able to work in a swingometer gag somewhere...

 
Bunter
152823.  Thu Mar 01, 2007 7:08 pm Reply with quote

"How did Snow turn to water?"

 
MatC
152892.  Fri Mar 02, 2007 6:05 am Reply with quote

One of the most interesting recent quandaries in the famously inexact science of epidemiology was to do with badgers and TB.

As well all know, many farmers have, since the 1970s, blamed badgers for spreading bovine TB to their herds. For many years, badgers were gassed by cyanide.

It was only in 1998 that the first ever scientific trial of badger culling began. Three different regimes were compared: reactive culling (as soon as TB breaks out in the cows, you kill all the local badgers); proactive culling (kill as many badgers as possible in the given area, whether or not there’s TB); and no culling.

The first obvious result of this (ongoing) experiment were quite striking: the geographical link between infected badgers and infected cows was empathically demonstrated, and in the laboratory, it was shown that cows were infected by the same strain of TB as their local badgers.

At last, it seemed, badgers had been found guilty by scientific evidence, instead of mere prejudice and tradition. Just one problem ...

If badgers cause bovine TB, then reactive culls ought to lead to a reduction in cattle infection rates. But in fact, the result is exactly the opposite.

During the first five years of the trial, wherever reactive culling was practiced there was a (presumably average) 27% increase in bovine TB outbreaks in the area. This was true in all nine areas where reactive culling occurred. Epidemiology doesn't usually get results that clear-cut (expect by fiddling them), so this does seem to be pretty incontestable evidence: badgers are linked to TB in cattle, but killing them makes the problem worse.

It turns out that scientists who opposed culling right from the start had predicted exactly this result. Culling causes a badger colony to break up - survivors (and there are always survivors) flee the homestead ... taking their disease with them.

Latest research suggests that culling can work: a very widespread cull will reduce overall levels of TB in cattle - while increasing them in the area immediately surrounding the killings. So for culling of badgers to work reliably, it would be necessary to more or less eradicate them from Britain.

Main Source: Organic Gardening, April 2007.

 
Frederick The Monk
152923.  Fri Mar 02, 2007 7:25 am Reply with quote

The thing I've never understood about the Badger/ Cow TB argument is the method of transmission. As I understand it TB in humans is spread by aerosol droplets expelled by people with the active disease of the lungs when they cough, sneeze, speak, or spit.

Now badgers can't speak so we can rule that one out to start with. But how to they get so close to cows? I assume they must do their infecting at night as a/. badgers are noctural and b/. a cow would have to be lying down to be near enough a badger to get infected. But why do badgers approach slimbering cows? Do they kiss them whilst they're asleep? is it some sort of 'dare'? Do cows and badgers secretly smoke together at night when no-one is looking? And how do we know that it isn't the cows giving the badgers TB?

So many questions..........

 
Frederick The Monk
152927.  Fri Mar 02, 2007 7:30 am Reply with quote

I knew it, from New Scientist 8th October 2006
Quote:
Blame the cows...

BADGERS are known to be carriers of bovine TB, and for many years British farmers have been killing them in the belief that this will prevent them from spreading the disease to cattle. Now researchers have shown for the first time that the disease also flows the other way, from infected cattle to badgers.

Evidence for the transmission of TB from cows to badgers came during the UK's foot and mouth epidemic in 2001. The movement of cattle around the country was halted, and vets stopped diagnosing and treating bovine TB so they could focus on foot and mouth instead.

With more TB-infected cows left untreated for longer periods, there was more chance they would infect badgers, says Rosie Woodroffe of the University of California, Davis. Her team found that cases of TB in badgers doubled during the nine months when testing for Mycobacterium bovis, which causes bovine TB, was suspended, and returned to previous levels once testing resumed.

"The delayed removal of TB-affected cattle caused by the foot and mouth epidemic was associated with a significant rise in M. bovis prevalence in badgers," the team writes in Proceedings of the National Academy of Sciences (vol 103, p 14713). They also found that TB rates in badgers increased in areas where they were being culled, because previously uninfected animals were picking up the disease by infiltrating niches left by culled animals. Overall the numbers of badgers in these areas fell, however.

Woodroffe recommends tighter controls and diagnosis of TB in cattle. "Improved cattle controls might not only have immediate benefits through reduced cattle-to-cattle transmission, but could also ultimately reduce the probability of re-infection from wildlife," she says.

Pro-badger campaigners, who have argued for years that culling is ineffective, say they have been vindicated. "This research confirms beyond doubt that cattle are the major vectors of bovine TB, readily infecting badgers and other cattle," says Trevor Lawson of the UK's Badger Trust.

 
MatC
152928.  Fri Mar 02, 2007 7:33 am Reply with quote

Yes, I've never managed to figure that out either, Fred. Frustratingly, every report assumes prior knowledge, so the method is never mentioned. Your suggestion that they kiss them while they're asleep, however, is a slur on the entire badger community, and also disempowers cows by casting them in the role of passive victims of sexual violence thus perpetuating stereotypes within a gendered matrix.

Personally, I think badgers are deliberately infecting cows as part of a last-ditch direct action campaign against global warming.

 
MatC
152929.  Fri Mar 02, 2007 7:35 am Reply with quote

So ... the same question in reverse: how do the cows infect the badgers?

 
dr.bob
153058.  Fri Mar 02, 2007 10:34 am Reply with quote

Perhaps the cows are allergic to badger fur and so sneeze over them.

That's why you'll never see a cow shaving with a badger brush.

 
MatC
153066.  Fri Mar 02, 2007 10:43 am Reply with quote

Sigh ... ! Bob, the reason you don't see cows shaving is because they is ladies!

 
dr.bob
153081.  Fri Mar 02, 2007 10:59 am Reply with quote

They might want to shave their legs

 
eggshaped
154001.  Tue Mar 06, 2007 2:39 am Reply with quote

Question: Why did the World Health Organisation parachute 14,000 cats into Borneo?


In the 1950s, the Dayak people were suffering from malaria. As was the standard response at the time, the WHO dropped a not inconsiderable amount of DDT on the area of Borneo in which they lived. Problem solved, you might think. Unfortunately there were unforeseen side-effects. Firstly, the pesticide also killed a parasitic wasp which kept the country’s caterpillars in check, a certain species of caterpillar ate the thatch causing villagers’ roofs to fall-in. More worryingly, geckos ate insects and cats ate geckos which meant that the population of cats fell drastically leading to a flourishing rat community.

The malaria problem had gone, but it was replaced by sylvatic plague and typhus, and the WHO were left with only one solution, the dramatic parachuting of 14,000 cats into Borneo.

Malaria


Malaria is actually 4 diseases.

The month of February was named after Febris/Februus/Februa, the Roman god of Malaria

One of the earliest scripts written thousands of years ago, in cuneiform on clay cloths, lays the destruction of Malaria at the feet of the Babylonian god of destruction and pestilence named Nergal.
He is shown to be doubled winged insect – like a mosquito.

Spanish Flu:


The pandemic was known as Spanish flu, but we know it did not start in Spain. It was called Spanish Flu because Spain was not at war, so there was a free press. Most of Europe had a censored press.

MacFarlane Burnett spent much of his life studying influenza, and he concluded that the worldwide death toll (from the 1918–1919 pandemic) was a minimum of 50 million, possibly 100 million.

In three weeks, it killed more people than AIDS has in 24 years.

Air pockets also formed outside the lungs, and when you’d move these people it would sound like popping bubble wrap. Nose bleeds were common, less common was bleeding from mouth, and even bleeding from the eyes and ears.

In Phoenix, a rumor started that dogs carried influenza, and people were shooting their pets

Both Spanish flu and Bird flu victims are actually killed by their own immune systems (how does this compare to other viruses? Plague is more virulent thanks to a weakening of the immune system – Ebola also suppresses the immune system). The virus causes the immune system to attack the respiratory system. As a result, sufferers victims' lungs fill with fluid, and they drown.

On the other hand victims of cholera die of dehydration (who)

Plague


Globally, the World Health Organization still reports 1,000 to 3,000 cases of plague every year.

Typhoid

Typhoid is a form of Salmanella (S. Typhi)

Polio

The WHO announced in 1988 that it intended to eradicate polio by the year 2000. The disease still kills about 2,000 people a year, mostly children.

Smallpox


Smallpox is the only disease ever to have been eradicated.

In southwestern Asia it had been known for centuries that a healthy person could be made immune to smallpox by being injected with pus taken from the sores of an infected person. Another technique, practiced in China, was to grind the scabs of a smallpox victim and blow the powder through a tube into the nose of a healthy person.

cats
February
Nergal
Spanish Flu Stuff
Immune System
Plague Deaths
who
EBR

 
MatC
155183.  Fri Mar 09, 2007 5:48 am Reply with quote

“Badger ham was once a delicacy in South Somerset.”
- Western Daily Press, 7 March 07.

 
Flash
155235.  Fri Mar 09, 2007 6:54 am Reply with quote

James, do we know why the cats were delivered by parachute, and are we sure that this was a literal parachute drop, rather than a figurative one (the way we might say that, say, John Reid was parachuted into the Home Office)? Maybe the parachute was the quickest way of dispersing them across an inaccessible country, but were they parachuted individually in little harnesses, or in boxes? Sorry to worry at this one, but it's such a great question.

On vaccination, Jenner did his experiments for the smallpox vaccine on local children, a methodology which would be difficult to get past NICE these days (it's PC gone mad). And when it was taken to South America the vaccine couldn't be kept alive for the length of the sea journey so they injected it into passengers and then extracted the antibodies at the other end (or something - I may have garbled the techicalities on that one).

 
eggshaped
155250.  Fri Mar 09, 2007 7:04 am Reply with quote

Yes, it was an actual parachute. It seems that the village was in the middle of no-where, so you can see why transporting them by air would be necessary.

This is a DDT case study from the International Union of Pure and Applied Chemistry, and is an example of a number of IMHO trustworthy sites which recount the story and explicitly mention parachutes.

Sadly I can't find anything more than an outline of "operation cat drop" so I don't know exactly how they were dropped, but I would imagine it would be in a couple of crates.

I'll do some more digging and see what I can find, in the meantime, if anyone alse can find anything?

 

Page 1 of 5
Goto page 1, 2, 3, 4, 5  Next

All times are GMT - 5 Hours


Display posts from previous:   

Search Search Forums

Powered by phpBB © 2001, 2002 phpBB Group