Re: diseases and immunity

Gerold Firl (geroldf@sdd.hp.com)
9 Jul 1996 23:22:53 GMT

In article <4rufrh$h3j@dfw-ixnews2.ix.netcom.com>, mbwillia@ix.netcom.com(Mary Beth Williams) writes:

|> In <4ru3hs$bdj@news.sdd.hp.com> geroldf@sdd.hp.com (Gerold Firl)
|> writes:

|> >Mcneill does mention something like this, discussing a group of
|> >"canadian indians" on their first exposure to TB. He doesn't say when
|> >it happened; I assumed 19th century. He does say that at first
|> >exposure, the infection looked totally unlike TB; not only were the
|> >internal organs attacked, but also the spinal meninges. By the third
|> >generation, the infection settled down into the familiar pulmonary
|> >pattern.

|> Joel's example was 20th-century Upper-Midwest, not 19th-Century Canada,
|> possibly two very different situations, as it is nearly impossible for
|> 20th-century Indians in the Midwest _not_ to have been in contact with
|> Europeans, or other Indians who had been in contact with Europeans, and
|> hence, not to have been exposed to TB.

Perhaps - or maybe joel was just confused.

|> HOWEVER, you're going to have to give a better citation than a generic
|> *MacNeil*, particularly when giving the level of detail regarding the
|> symptoms of the infection. What were the bases for MacNeil's purported
|> assertions that this in fact was TB? Ethnohistoric accounts from the
|> 19th century, or skeletal analysis by fizzies from the late 20th?

I was wondering the same thing. He cites rene dubos, _man adapting_,
as the source. Are you familiar with it? I've never heard of it
before.

|> As an aside, TB mortality rates among whites in the New World were
|> exceedingly high (I personally did a study of a nineteenth-century
|> white community in Connecticut where 15-20% of natural deaths were
|> attributed to *consumption*, i.e., TB), and thus Europeans never did
|> appear to develop an immunity to the disease.

Immunity is a relative thing. If it takes 10 years for TB to kill you,
then you are relatively immune, compared to someone who dies within a
week.

I would expect that a virgin-soil TB epidemic probably wouldn't leave
any bone lesions, if people were killed-off fairly quickly. Which
again leads to the question of how the TB diagnosis was made, and to
which I still don't know the answer.

|> How does that effect
|> your your *sexual attraction* hypothesis?

It doesn't effect it at all, of course. Double blind experiments have
shown that people are sexually attracted to those who have widely
differing immune factors; those results were posted to this newsgroup
a few months ago. That leads to comparitively rapid diffusion of
various immune-system genes through a breeding population, but by no
means does it guarantee total immunity to every possible disease. I
brought it up because it shows the long-standing evolutionary
advantage of genetic variability, particularly in the immune system.

|> It's very
|> >similar to what happened in europe when syphilis first appeared: the
|> >individuals who were unfortunate enough to have no immunological
|> >response to the syphilis spirochete would die a few days after being
|> >infected. They were eaten alive by the spirochete. Nasty, but that's
|> >the way it works.]

|> Do you have a citation for this? As syphilis would have first appeared
|> in 15th-century Europe, I'm not sure I trust post-Medieval Europe's
|> understanding of pathologies the way you do. And, once again, if they
|> died off right away, there would be nothing on the skeletal *record* to
|> show evidence of such a demise.

I'll try and find some cites for you on this; I think it was braudel,
but I'll check.

The european hypothesis that syphilis was a new world import dates
back to 1539; the manifestations were so spectacular, and the pattern
of propagation was so consistant (seville in the early 1490's,
spreading to italy and then throughout europe) that the crude
epidemiology of post-medieval europe was sufficient to make the
connection.

The american hypothesis stood unchallanged until it was discovered
that the spirochete responsible for yaws is indistinguishable from the
syphilis pathogen. Yaws has been around in the old world forever. This
has thrown the american-origin hypothesis into doubt, though I still
find the coincidental timing to be compelling.

|> >|> The problem with using TB as an example in explaining the *massive
|> >|> depopulation* of the Americas is that it really was very
|> >|> insignificant... TB shows up _after_ the large die-offs, and in
|> fact
|> >|> may have been only a *secondary* infection, that is, attacking
|> those
|> >|> individuals whose immunities were weakened by smallpox, measles,
|> etc.

|> >You can't see the trees for the forest, mb. Smallpox was the mosd
|> >important killer, but if smallpox hadn't existed, then another disease
|> >would have taken its place. If TB got to an isolated population before
|> >smallpox did, then TB would would kill them off. No one is using TB to
|> >explain the american die-off; the example was cited to illustrate the
|> >vulnurability of previously-unexposed populations to new pathogens.

|> TB never would have taken the place of small-pox or any other childhood
|> infection, as infection rates have never reached those of these other
|> diseases, in Indian or European populations. (In fact, it has been
|> strongly hypothesised that TB was present in pre-Columbian populations
|> in the Upper Midwest.)

TB is an ancient organism, and may have been around in the pre-contact
americas, but there are different strains of the bacillus, some more
virulent than others. In resistant populations, TB is endemic, but in
non-resistant groups there are different rules of the game. There, TB
can act as an epidemic disease, and virulent strains suddenly become
(temporarily) more viable.

|> You example is an extremely poor one, Gerold,
|> as there appears to be some parity between Indians and non-Indians when
|> it comes to mortality rates from TB.

If mcneill's example is correct, then what you say is not so. By the
third generation, the mortality rates may be similar, but by then the
damage has been done.

-- 

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=-=-=-=-=-=-=-=-=-=-=-=-=-=----   Gerold Firl @ ..hplabs!hp-sdd!geroldf