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Old January 16th, 2018, 01:54 PM   #1
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Black Death 'spread by humans not rats'


Rats were not to blame for the spread of plague during the Black Death, according to a study.

The rodents and their fleas were thought to have spread a series of outbreaks in 14th-19th Century Europe.

But a team from the universities of Oslo and Ferrara now says the first, the Black Death, can be "largely ascribed to human fleas and body lice".

The study, in the Proceedings of the National Academy of Science, uses records of its pattern and scale.

The Black Death claimed an estimated 25 million lives, more than a third of Europe's population, between 1347 and 1351.

"We have good mortality data from outbreaks in nine cities in Europe," Prof Nils Stenseth, from the University of Oslo, told BBC News.

"So we could construct models of the disease dynamics [there]."

He and his colleagues then simulated disease outbreaks in each of these cities, creating three models where the disease was spread by:

rats
airborne transmission
fleas and lice that live on humans and their clothes

In seven out of the nine cities studied, the "human parasite model" was a much better match for the pattern of the outbreak.

It mirrored how quickly it spread and how many people it affected.

"The conclusion was very clear," said Prof Stenseth. "The lice model fits best."

"It would be unlikely to spread as fast as it did if it was transmitted by rats.

"It would have to go through this extra loop of the rats, rather than being spread from person to person."

'Stay at home'

Prof Stenseth said the study was primarily of historical interest - using modern understanding of disease to unpick what had happened during one of the most devastating pandemics in human history.

But, he pointed out, "understanding as much as possible about what goes on during an epidemic is always good if you are to reduce mortality [in the future]".

Plague is still endemic in some countries of Asia, Africa and the Americas, where it persists in "reservoirs" of infected rodents.

According to the World Health Organization, from 2010 to 2015 there were 3,248 cases reported worldwide, including 584 deaths.

And, in 2001, a study that decoded the plague genome used a bacterium that had come from a vet in the US who had died in 1992 after a plague-infested cat sneezed on him as he had been trying to rescue it from underneath a house.

"Our study suggests that to prevent future spread hygiene is most important," said Prof Stenseth.

"It also suggests that if you're ill, you shouldn't come into contact with too many people. So if you're sick, stay at home."

---

Black Death 'spread by humans not rats' - BBC News
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Old January 16th, 2018, 01:55 PM   #2
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Not sure if news articles are permitted here, but I found this interesting so I thought I'd share.
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Old January 16th, 2018, 02:02 PM   #3
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I would say that it is reasonable to concur that human-affected diseases are transmitted by other humans.
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Old January 16th, 2018, 06:31 PM   #4

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Plague - rats or humans


"Our study supports human ectoparasite transmission of plague during the Second Pandemic, including the Black Death. Using recent experimental data on human fleas and body lice as plague vectors, we have developed a compartmental model that captures the dynamics of human ectoparasite transmission."

full report
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Old January 16th, 2018, 07:58 PM   #5
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Lice were a major problem in the pre-modern world with people both picking them off each other and using lice combs. Lice don't bite deep enough to spread a disease to the blood stream and fleas rarely attack humans -they prefer animal with lot of fur they can hide in and with thinner skins that let them bite to the blood the tiny vampires live on. Getting the black death to Europe by human fleas is extremely unlikely and it's spread by fleas is also very unlikely.

Sticking unreliable data into a computer with models you've created rather than using carefully controlled and observed experiments is just plain pseudo-science. A nice way to get grants and advance ones careers, but silly as a means of discovering fact.
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Old January 17th, 2018, 01:08 AM   #6

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Makes sense. I always thought the rat flea thing was just a guess.
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Old January 17th, 2018, 02:43 AM   #7
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260 people died of Bubonic Plague in Eyam in Derbyshire in the 1660s. The village became exposed when infected fleas were released from a bale of damp cloth which had been sent up from London.

Rats play a part in a chain. The bacillus kills the rats too. They are not immune. But when rats die in their burrows, the bacillus survives and when new rats inhabit the burrow, they become infected again. Rats didn't walk from London to Derbyshire though and the observed 'leaps' from one place to another have to be mediated by some other mechanism.
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Old January 17th, 2018, 08:19 AM   #8

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Quote:
Originally Posted by Disciple of Sophia View Post
Lice were a major problem in the pre-modern world with people both picking them off each other and using lice combs. Lice don't bite deep enough to spread a disease to the blood stream and fleas rarely attack humans -they prefer animal with lot of fur they can hide in and with thinner skins that let them bite to the blood the tiny vampires live on. Getting the black death to Europe by human fleas is extremely unlikely and it's spread by fleas is also very unlikely.

Sticking unreliable data into a computer with models you've created rather than using carefully controlled and observed experiments is just plain pseudo-science. A nice way to get grants and advance ones careers, but silly as a means of discovering fact.
Lice are known vectors of human disease. The species Pulex irritans is sometimes known as the "human flea" because of its willingness to use humans as its host. Of course it will readily feed on other mammals as well, which means that it can and does act as a bridging vector, transmitting diseases from wild reservoirs into the human domestic environment and vice versa.
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Old January 17th, 2018, 06:23 PM   #9
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Quote:
Originally Posted by Recusant View Post
Lice are known vectors of human disease. The species Pulex irritans is sometimes known as the "human flea" because of its willingness to use humans as its host. Of course it will readily feed on other mammals as well, which means that it can and does act as a bridging vector, transmitting diseases from wild reservoirs into the human domestic environment and vice versa.
TY for your correction on lice.
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Old January 17th, 2018, 08:29 PM   #10

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Anyone who's dog has had fleas knows that dog fleas will bite a human. They bite, but they can't live on a human host: they have to taste you to find out. Most fleas are species specific. That single taste-bite is enough to transfer whatever is in the flea.

It makes sense that plague spreads by human fleas, but it is well documented that it spreads by rodent fleas as well, and does so to this day. It is endemic in North America, believed to be imported to the New World by shiprats (probably Norway rats, through their fleas). Yes, the US (and every European country) has the same plague species that caused the black death, but it no longer causes corpses to go grey and I don't think it has the "ring around the rosey" spots anymore (due to mutation of the disease itself).

The main reason for rat control in NY City is plague. It's present in rodent populations in the West, like prairie dogs. It really needs a population of animals, sharing fleas to survive. The CDC says there are 1-17 cases per year in the US, 80% being the bubonic form (20% pneumonic). The original post mentions a cat spreading the pneumonic form.

The bubonic form is spread by bites. Sometimes the bubonic forms turns pneumonic in a victim, and then is spread in aerosol form by coughing and sneezing. The pneumonic form is highly contagious.

--> So, what the simulation says is that the MAJORITY of black plague was spread by human fleas ... but transmission from rodent fleas is well documented, with possibly 20% pneumonic. There's an anecdotal story of a village that stayed plague free, until someone traveling got lonesome, went back home, and slipped past the guards (probably, human flea vectors). Many vector borne diseases are not straightforward, single vector.

There are many other insect vectors that spread disease from one species to another, like malaria: bacteria, viruses, filarials, microfilarials (beware of the South Pacific). Consider Zika, Dengue Fever, and Chickunguya ... all made the jump to the Caribbean from South America, Zika and Chickunguya may have made the jump to Florida. There's three kinds of mosquito born encephalitis, plus West Nile fever in the west ... and two kinds of tic fever. Everyone knows about Lyme disease (spread by a tiny nymph phase of a tic) mostly in the East. The more tropical you are, the scarier things get.


A 1st century BCE physician named Dioscorides wrote a book on what he observed of a plague outbreak in Libya. It was around a long time before that. As a complete sidebar: ancient Egyptians shaved their heads & wore wigs to avoid lice.

You all know this little child's song is about plague, right?
Ring around the rosey
Pocket full of posey
Ashes, ashes, we all fall down

Last edited by Dios; January 17th, 2018 at 08:44 PM.
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