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pdevr | 1 year ago

As far as I understand it, they used 25 human and 12 squirrel samples. Comparison was done among medieval red squirrel strains, medieval human strains, and modern red squirrel strains.

Finding: medieval red squirrel strains were closer to medieval human strains than to modern red squirrel strains.

Inference: In medieval England, leprosy spread between red squirrels and people.

Problem with the inference: If they used modern human strains too and then compared them all, it would have been a complete study.

Are modern red squirrel strains closer to modern human strains than to medieval red squirrel strains? What kind of differences are there? Is it that they evolved independently from medieval times to modern times and thus appear different? Lots of questions are unanswered.

discuss

order

bastawhiz|1 year ago

> If they used modern human strains too and then compared them all

Presumably the number of leprosy cases originating in modern England is near zero, so actually procuring relevant strains seems impossible, no? I can't imagine that comparing random strains from places around the would would yield interesting results.

bennyhill|1 year ago

When we are only talking about a few samples in each group, 4 cases every few years seems fine.. I would hypothesize that many of the symptomatic cases are people who are foreign but exposed to UK endemic leprosy. Of course to establish how true that is means there are more data points to collect for cases with foreign contact and the involved lands.

pdevr|1 year ago

It is very low indeed, and a large percentage of the cases are involving strains from other countries, but hopefully the number is not real zero[1], even after discounting the strains from other countries.

[1] https://bmjopen.bmj.com/content/6/5/e010608

verisimi|1 year ago

Not only that, but is it really the case that genetic material survives for 600 years? Can we really say, 'we know that these 12 samples are from red squirrels 600 years ago'?

> "With our genetic analysis we were able to identify red squirrels as the first ancient animal host of leprosy," says senior author Verena Schuenemann of the University of Basel in Switzerland.