Published Date: 1997-02-26 23:50:00
Subject: PRO/AH> Development of antimalarial resistance (08)
Archive Number: 19970226.0453

DEVELOPMENT OF ANTIMALARIAL RESISTANCE (08)
===========================================
Date: Wed, 26 Feb 1997 15:33:37 +0000
From: Alfons Van Gompel <fvgompel@poliklin.itg.be>
[see
Development of antimalarial resistance: request fo... 970122231526
Development of antimalarial resistance (02) 970123173546
Development of antimalarial resistance (03) 970127093642,
970127154212
Development of antimalarial resistance (04) 970201150453
Development of antimalarial resistance (05) 970201150520
Development of antimalarial resistance (06) 970201150538
It has been suggested that tourists taking antimalarials may inadvertently
promote the development of antimalarial drug resistance. We want to stress
that only a minority of travellers and expatriate residents should take
prophylaxis, but that they need a highly effective treatment, since they lack
immunity. The acquisition of protective immunity to malaria is considered to
be a slow process, one that requires frequent and/or long-standing contact
with the parasite and maintenance of a constant antigenic stimulus. Tourists
and even the great majority of long-term residents or travellers do not
acquire sufficiently protective semi-immunity, and the mortality risk for
malaria - if not correctly treated and done so in a timely fashion - is very
high. Most of them may be considered as non-immune.
The data, as given in an article in the Am J Trop Med Hyg (44, 1991, pp.640-
644) are a nice illustration of the arguments which may (partly) explain and
justify the advice to tourists and expatriates for having the "latest
designer" drug of choice on hand in case of attack. "In november 1989, a
single curative dose of FansidarR was administered to 59 volunteers divided
among 3 groups with 18 months, four years and life-long exposure to endemic
malaria (in Arso PIR, Irian Jaya). The proportion of volunteers in each
group still positive for _P. falciparum_ on day 7 of followup was 54%, 0 %,
and 14% respectively."
The conclusion of these data is that immune status profoundly affects
clinical response to FansidarR" This does not mean that the "latest designer"
drug are needed, but a maximal effective strategy (all possible preventive
measures and sometimes an emergency treatment) needs to be prescribed for the
NON-IMMUNES (expatriates, tourists, but probably also small infants, pregnant
women, migrants from the highlands etc.). For instance, in our opinion,
Fansidar R" alone should not be used in this region (South-East Asia) as
treatment regimen by the NON-IMMUNES, but only in combination with quinine
(or at this time - 1997 - much better quinine + doxycycline if not contra-
indicated). This does not mean that non-immunes need to take chemopophylaxis
all the time.
RESIDENTS staying for a longer period in the tropics can stop oral prevention
in well-balanced circumstances, mostly without serious consequences. These
residents often live in stable conditions with better personal protection,
they may have knowledge of local epidemiology and often have acces to
reliable medical care in case of medical problems. On the other hand, aid
workers may live in an high risk area, far from reliable health care. The
emphasis lies on the responsibilisation of the individual, because the
reality is that many of them - DESPITE OUR ADVICE - will stop taking
prophylaxis after some time. Therefore we advise people intending to settle
in malarious areas to take fully compliant chemoprophylaxis at least during 3
months, while learning to protect themselves against mosquito bites and
seeking local doctors experienced in treating malaria. Thereafter - after a
few months or after a few years - the resident will have to judge the risk
and to decide whether or not to stop the prophylaxis, preferably jointly with
the local doctor and evidently only on condition (1) that he protects himself
as much as possible against mosquito bites in the evening and at night, and
(2) with the emphasis on early diagnosis and prompt adequate treatment. For
growing children, pregnant women and persons who for one reason or another
are weakened,it remains however often risky not to take preventive
medication. We need to educate the travellers/residents to take the whole
prescribed treatment. In the local population, ceasing taking the treatment -
when one begins to feel a little better - is very probably an important
factor contributing to the development of drug resistance.
TRAVELERS staying only for short periods in malaria area, are in a different
situation compared to persons staying already for a long time in the tropics.
Their position may be more vulnerable, because they are moving all the time
from place to place, and the malaria-exposure and hence malaria-risk changes
constantly following the itinerary (the risk for malaria varies substantially
from country to country and is often distributed within a country in a focal
way). The intake of prescribed preventive medicines is very important for
them.
We conclude that only part of the residents should take prophylaxis, that
travellers often have to rely on prophylaxis, but we emphasise that both
these groups need a highly effective treatment in case of malaria attack.
For the other raised questions:
(1) "if (and to what extent) this contributes to the development of
resistance" : the proportion of infections in expats is very small compared
to the bulk of infections in locals
(2) " to what extent this creates an (unneccessary) need for the local
population" this remains unanswered, and needs to be considered as a
potentially important factor in the selection of resistant strains.
See also the answer by P.Bloland [970127093642, 970127154212]
---
Alfons Van Gompel MD
Jef Van den Ende MD
Travel Clinic
Institute of Tropical Medicine
2000-Antwerp
Belgium
e-mail: <fvgompel@poliklin.itg.be>
..........................................................................chc
--
*##########################################################*
ProMED-mail makes every effort to verify the reports that
are posted, but the accuracy and completeness of the
information, and of any statements or opinions based
thereon, are not guaranteed. The reader assumes all risks in
using information posted or archived by ProMED-mail. ISID
and its associated service providers shall not be held
responsible for errors or omissions or held liable for any
damages incurred as a result of use or reliance upon posted
or archived material.
************************************************************
Visit ProMED-mail's web site at <http://www.promedmail.org>.
Send all items for posting to: promed@promedmail.org
(NOT to an individual moderator). If you do not give your
full name and affiliation, it may not be posted. Send
commands to subscribe/unsubscribe, get archives, help,
etc. to: majordomo@promedmail.org. For assistance from a
human being send mail to: owner-promed@promedmail.org.
############################################################
############################################################