Drug-Resistant Malaria - libdoc.who.int - World Health Organization

REVIEW I 21
are signs to suggest this or1g1n. Resistance in Papua New Guinea
is clearly caused by importation from Irian Jaya, the subsequent
spread into the Solomon Islands by importation from Papua New
Guinea, and the spread into Vanuatu originated obviously from
either Papua New Guinea or the Solomon Islands.
It may be noted that resistance to 4-aminoquinolines occurred
in several countries of the Region originally as a resistance to
amodiaquine rather than to chloroquine. The reported difference
in the response to these drugs appears to have, therefore, litt le
practical significance insofar as the Western Pacific Region 1S
concerned.
The continued massive use of 4-aminoquinolines for presumptive
treatment, clinical cure or mass drug distribution has
undoubtedly contributed to the rapid dissemination of resistance
once a resistant strain has been introduced. While due caution
regarding the projec t ion of results in rodent malaria to human
malaria is required, it appears that chloroquine resistance is of
a very stable nature. Genet ic studies carried out in Edinburgh
and epidemiological data on P.falciparum seem to indicate that
resistant mutants have a distinct biological advantage over
sensitive parasites. The former are stable and also overgrow the
latter. This seems to be borne out by the epidemiological
observations in the Western Pacific Region and it would indeed be
useful to carry out observations in an isolated confined area
(island) with established chloroquine resistance and see whether
and when the parasite would revert to a sensitive state upon the
withdrawal of all 4-aminoquinolines.
There are indications from
that a continuous high degree of
importance than drug pressure
resistance.
several countries in
transmission has been
for the ultimate
the Region
of greater
spread of
Other specific questions which need to be answered in
relation to the present situation, arise from our lack of
knowledge about the continued sensitivity of P.falciparum to
alternative drugs including quinine and combinations such as
quinine/sulfadoxine/pyrimethamine and chloroquine/sulfadoxinel
pyrimethamine. At the same time the preferential susceptibility
or refractoriness of vectors to chloroquine-resistant strains of
P.falciparum deserves attention, particularly in the members of
the Anopheles punctulatus complex, A.sinensis and A.balabacensis
comp lex.
Failures with combinat ions of DHFR inhibitors and
sulfonamides have been reported 1n small numbers from most
countries 1n the Region. The phenomenon appears to be rather
common in parts of Kampuchea.