[leish-l] Leishmaniasis in Brazil

[Jennie Blackwell]

Isn't it a pain that our lives are so entirely dominated by "rules" rather
than practicalities!

Cheers, Jennie

On Thu, 16 Jan 2003, Richard Ashford wrote:

> Dear Jorge,
>
> How nice to hear from you, and happy new year to you too, though its
> getting a bit late for that.
>
> Of course I completely disagree with you!  I had thought Ralph Lainson and
> Jeff Shaw were the last remnants of the chagasists. It might be nice for
> practical purposes to have different names for the organism in two
> continents, but this contradicts various basic taxonomic essentials. This
> is not a matter of splitters and lumpers, it is a matter of basic rules.
>
> First, the 'rules of nomenclature' specifically prohibit the provisional
> naming of putative species. Second, (see my recent letter with Gediminas
> Valkiunas in TiP) natural host range, like geographical range is not a
> valid taxonomic character. The 'single species null hypothesis' (I'd love
> to see a reference for this: it states that two organisms must be regarded
> as conspecific unless they can be shown to be different) is one of the most
> important principles in taxonomy. Without it, all zoogeography and study of
> host specificity become circular arguments. Do you need more?
>
> I agree with you that the visceralising parasites are best treated as
> subspecies: L. d. donovani and L. d. infantum. This is because even these
> ones are not reliably separable in every instance, and because there are
> good differences in their biological potential, which correlate reasonably
> well with geography. So, if subspecies are used, these closely mimic
> subspecies of sexual organisms.
>
> The validity of 'archibaldi' is another question.  As things stand this
> name has no validity at all because any existing definition of it is very
> inadequate. Whether or not the insight of Lainson & Shaw, that there may be
> two forms in Africa, one in Sudan, that behaves like donovani proper
> (affects all ages, plenty of PKDL) and one in Kenya that behaves a little
> more like infantum (many subclinical cases little or no PKDL), proves to be
> related to valid taxonomic character states, is the subject of our study at
> present. Whatever the answer, I very much doubt that the name archibaldi
> will survive.
>
> I still maintain that the continued use of 'chagasi' masks the real and
> significant similarities between the various foci. And, anyway, if you want
> to use technical taxonomic terms, it is really essential to follow the
> rules. If you wanted to differentiate them, why not use vernacular terms
> such as NWZVL and OWZVL? This will be adequate till someone finds the
> reservoir host of Sudanese or Kenyan VL.
>
> Well I guess these chat lines would be boring if everybody agreed on all
> the issues!
>
> All the best,
>
> Dick
>
> --On 16 January 2003 08:30 -0500 "Arias, Dr. Jorge (WDC)"
> <ariasjor at paho.org> wrote:
>
>
>
> Dear Dick,
> First of all, Happy New Year!
>  I think one difference is that of "splitters" and "clumpers". We see it
>  throughout systematics.
>
>  True that Le. chagasi cannot be differentiated from Le. infantum with the
>  tool we presently have.
>
>  For those that work with the leishmanias, I believe that there is little
>  doubt that this organism was probably introduced from the Old World
>  fairly recently, and perhaps at different times to different parts of the
>  New World. I assume this because of the spottiness of its distribution
>  throughout the Region.
>
>  However there is quite a bit of clinical and epidemiological data (such
>  as different genera of vectors) that seems to warrant the separation
>  these two species of Leishmania. Maybe the correct procedure would be to
>  consider them as subspecies (Le. i. infantum, Le. i. chagasi and maybe
>  even include Le. i. archibald)?
>
>  I am particular to the "splitting" into two species because it also
>  allows easier management of my technical cooperation since there is a
>  great difference in the population that it afflicts and because possible
>  control interventions that could be implemented are also different in the
>  two areas.
>
>  We must also consider that if, sometime, differentiating characteristics
>  are found, it will be easier to manage the "split" literature than the
>  "clumped" literature.
>
>  Have a good year,
>
>  Regards,
>
>  Jorge
>  Jorge R. Arias, Ph.D.
>  Regional Advisor
>  Pan American Health Organization
>  525 Twenty-third Street N.W
>  Washington, D.C. 20037
>  Tel +1 (202) 974-3271
>  FAX +1 (202) 974 3565
>  ariasjor at paho.org
>  www.paho.org/dengue
>
>
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Jenefer M. Blackwell
Glaxo Professor for Molecular Parasitology
Cambridge Institute for Medical Research
Wellcome Trust/MRC Building
Addenbrooke's Hospital
Hills Road
Cambridge CB2 2XY

Telephone: +44 1223 336947
Secretary: Sheryl Bailey +44 1223 336852
Fax: +44 1223 331206
Email: jennie.blackwell at cimr.cam.ac.uk