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I suppose somebody has to spring to Dick's defence even if he doesn't
deserve it when he stirs it like that.<br><br>
As far as I am aware every case of L. infantum from South America that
has been typed by the Montpellier isoenzyme system has been identified as
MON1. This is the principal zymodeme of L. infantum but there are at
least a dozen others. There is certainly variation within MON1 as
mentioned by Jeff for South American strains and well demonstrated by
Michel Tibayrenc, so it will be no surprise if some stocks of L. chagasi
can be uniquely identified (Hide, M., Banuls, A.L., and Tibayrenc, M.
(2001) Genetic heterogeneity and phylogenetic status of Leishmania
(Leishmania) infantum zymodeme MON-1: epidemiological implications.
<i>Parasitology)</i> <b>123:</b>425-432.)<br><br>
However if the genetic distance for creation of a species is less
than the distance within a zymodeme we are going to completely lose our
grip on all Leishmania classification. Perhaps Dedet could tell us how
many zymodemes there are in Leishmania? It is certainly several hundred.
I cannot believe that anybody would want to see that many species of
Leishmania.<br><br>
Furthermore, there may have been multiple introductions of L.
infantum into South America. Assuming that these came from subtly
different subtypes of MON1 then it is likely that each new introduction
is are more closely related to a Mediteranean L. infantum strain than to
other South American L. infantum. We would then have to call each new
introduction by a new name! <br><br>
Dick's justification for abolishing L. chagasi (because we have to obey
the rules) was enough to make anybody rebel and demand to keep it.
However classification can only be useful it is reasonably consistent and
L. chagasi is the most glaring inconsistency in the genus. Its got to go!
<br><br>
<br>
Harry<br><br>
BTW we have had cases of "autochonous" VL in a dog in Britain.
A case was brought to the Liverpool School of Tropical Medicine in 1996.
According to the owners it had not been out of the country. It had spent
sometime at a dog rescue centre where it is presumed to have contracted
the disease by direct contact. This may be a more significant route of
transmission than usually thought. Eg the US east coast outbreak (has it
been settled how that one was transmitted). <br><br>
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Harry Noyes<br>
Room 231<br>
Biosciences Building<br>
School of Biological Sciences, <br>
University of Liverpool,<br>
Crown St.<br>
Liverpool<br>
L69 7ZB<br>
Internal 7334<br>
Tel 0151-794-7334<br>
Fax 0151-795-4408<br>
email harry@liv.ac.uk<br>
<a href="http://www.genomics.liv.ac.uk/" eudora="autourl">http://www.genomics.liv.ac.uk/</a><br><br>
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