[leish-l] leishmaniasis outside endemic area

[Marian Ulrich]

We have recently published some data from studies of VL on the island of
Margarita, Venezuela (Olga Zerpa, et al., Mem. Inst. Oswaldo Cruz,
December)
that may be relevant to your thoughts.  Of the patients, 86% were three
years
old or younger.  Leishmanin skin tests in 1643 healthy persons from the
endemic
communites showed increasing sensitization with age; 13% of those from 0
to 10
years old were skin-test positive, while 33% of the group of persons
older than
40 were positive.  In Venezuela, as in the Old World, VL (L. infantum)
is very
largely a disease of  young children.  The intensity of exposure clearly
seems
to be a factor in sensitization to leishmanin (for example, a previous
case of
human VL or an infected dog in the home increases the frequency), but of
course
that does not explain the greater susceptibility of very young children.
 Marian Ulrich
 Instituto de Biomedicina
 Universidad Central de Venezuela, Caracas



Richard Ashford wrote:

> Dear all,
>
> Re: imported human VL
>
> Over quite a number of years I have attempted to 'collect' cases of human
> VL imported into non-endemic areas. My question has been whether the
> age-distribution of human cases is the same (for L. d. infantum) as it is
> in enedmic/enzootic areas. There are too few cases to be conclusive, and
> the age structure of the travelling population is different from that of
> the indigenous populations, so both numerators and denominators are
> questionable. Overall, however, there does seem to be a preponderance of
> infants among (non-HIV) cases imported into non-endemic areas which, if
> substantiated, would support the idea that the rarity of cases in adults
> has less to do with acquired specific immunity, than some aspect of the
> normal development of innate immunity.
>
> I suppose that L. d. infantum infects H. sapiens adults only with great
> difficulty, but is able to infect at least a small proportion of infants.
>
> A large scale skin-test study in an endemic area might show that people of
> all ages are equally exposed, becoming skin test positive as a result, but
> that only a very small proportion of infants, and selected adults get sick.
>
> Does this make sense? Does anyone know why L. d. infantum specialises in
> infants?Can anyone add some data to my hand-waving generalisation? I wonder
> if a sufficiently large skin test study, with detailed age breakdown has
> been done?
>
> By the way, though L. d. donovani and l. d. infantum are very closely
> related (there is probably no combination of taxonomic character-states
> that can reliably separate them, that also coincides with their biology),
> their behaviour in humans is very different, so it is wrong to extrapolate
> results of, for example, nutritional-state-susceptibility studies, from one
> form to the other.
>
> Happy new year,
>
> Dick Ashford
>
> --On 11 January 2003 12:45 +0100 nicleger <nicleger at wanadoo.fr> wrote:
>
> >
> > Des vecteurs prouvés ou suspectés ont été à plusieurs reprise signalés en
> > dehors des zones d'endémie leishmanienne. Récemment l'un de mes élèves en
> > a même capturé à Reims (été 2002) ! Un de nos collègues allemand (
> > Torston NAUCKE) a effectué une enquête autour d'un cas apparemment
> > autochtone de leishmaniose canine . Il l'a ensuite étendue à d'autres
> > régions d'Allemagne et également aux Ardennes belges et françaises où il
> > a signalé la présence de P.mascittii et un peu plus tard de
> > P.perniciosus. Demandez lui ses tirés à part.  Entomologiquement vôtre.
> > N.LEGER.
>
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