About half of all Tristanians have asthma.
It has a genetic basis, as you’ll see in the film.
What happened here is a good example of the founder effect. A high proportion of the original settlers had asthma, and because the settlers have intermarried, a very high percentage of the population have asthma.
This is actually not that different from what we’ve done with domestic dogs.
But instead of putting them on an isolated island that has little access to new bloodlines, we have made a closed registry system. In effect, the closed registry system is like setting up hundreds of Tristan da Cunhas.
If human populations were all like Tristan da Cunha, we’d be in a lot of misery. Each population would be highly susceptible to all sorts of diseases. Each would probably have its own disease. It wold be very bad for us.
Yet we seem to think it is perfectly fine for domestic dogs.
[...] more: Tristan da Cunha– The Island of Asthma « Retrieverman's Weblog Posted in Health and [...]
I have read that the average human has something like ten ‘bad’ recessives. We just don’t see high rates of those diseases because humans aren’t usually linebred. Unless we live in a community that is restricted in some way, like an island, or a religious community.
The average dog has something like four or five ‘bad’ recessives.
I think the term is “deleterious recessive,” but bad recessive is easier to spell.
here’s a write up on the fact that the island was apparently colonized by 15 people, two of whom apparently had asthma.
http://ajrccm.atsjournals.org/cgi/content/abstract/153/6/1902
Am. J. Respir. Crit. Care Med., Vol 153, No. 6, Jun 1996, 1902-1906.
Asthma on Tristan da Cunha: looking for the genetic link. The University of Toronto Genetics of Asthma Research Group
N Zamel, PA McClean, PR Sandell, KA Siminovitch and AS Slutsky
Department of Medicine, University of Toronto, Ontario, Canada.
a general article on asthma & genetics.
Jornal de Pediatria
Print version ISSN 0021-7557
J. Pediatr. (Rio J.) vol.84 no.4 suppl.0 Porto Alegre Aug. 2008
doi: 10.1590/S0021-75572008000500010
Impact of genetics in childhood asthma
Leonardo A. PintoI; Renato T. SteinII; Michael KabeschIII
http://www.scielo.br/scielo.php?pid=S0021-75572008000500010&script=sci_arttext&tlng=en
Peggy Richter
That’s exactly what the full documentary is about.
Zamel appears in it.
To get the full video, click “Source” under the video, and it will take to the documentary on youtube, with links to the different parts.
It’s a weird sort of genetic bottleneck, because the people who settled it came from a lot of different places. Those 15 came from 3 or 4 different countries.
Well they all meet exact conformation standards for a Tristanian. Apparently line breeding has done well here to maintain the exact look and feel of a working bred Tristanian. Maybe with clear DNA genetic mappings for the Asthma defect it will be possible to selectively breed away from it. ;-)
Or perhaps they can go through more tests to conclusively determine that yes the parents have Asthma so they shouldn’t breed at all. Hmmmm. They should open their registry and import some St. John’s Fishermen. Outcross with some of them then selectively breed back good specimens.
Hmmmm
So I guess this is not a good visual argument for the benefits of diversity in the breeding population?
[...] of genetic disorders have started to pop up in your dogs and if you also notice that you have a Tristan da Cunha situation in your registry system, it’s time to have a discussion about health testing and [...]
[...] Cairns, scotties, Skyes, and westies could all interbreed until 1917, which is one year after the KC stopped registering litters of golden and flat-coat crosses. For my purposes, I don’t consider a breed a “true” breed until the registry closes. When the registry closes, one can idea of when the Tristan da Cunha phenomenon starts. [...]
Hi, Nice post!
I really like it especially the part “If human populations were all like Tristan da Cunha, we’d be in a lot of misery. ”
I will surely reading your other posts.
Thanks!