Biology Reference
In-Depth Information
resistance and strong governmental commitment to elimination. Problems
encountered during the program included the need to extend basic health
services into rural areas where malaria was being transmitted, residual foci
of transmission in ethnic minority and other difficult to reach groups and
difficulty in maintaining accurate diagnoses by microscopy when very
few positives were seen. Following a 6-year DDT spray program starting
in 1952, >20 residual foci of transmission were dealt with using inten-
sive IRS and MDA of entire populations usually numbered in the hun-
dreds with treatment courses of chloroquine/primaquine. Finding and
eliminating these residual foci was a massive effort of malaria surveillance
involving >5 million blood slides taken from July 1958 to December
1964 in order to find and treat the last 1023 malaria infections. During
this consolidation phase, the program had to examine >5000 slides in
order to find a single true positive, which is a considerably lower rate than
the false-positive rate from even expert microscopists. When Taiwan was
certified as eradicated of malaria on 25 November 1965, it was the con-
clusion of a 20-year program that at one point involved over 7000 staff,
a full research institute, as well as a large logistical establishment (
Depart-
ment of Health, Executive Yuan, 1991
).
4.2. Malaria Elimination in Mexico
Mexico has not eliminated malaria but has made great progress towards
that goal with most transmission being restricted to vivax malaria in south-
ern states such as Oaxaca (
Rodriguez et al., 2009
). Still largely based on
DDT IRS, in Mexico case finding and investigation plays a large role in
trying to achieve elimination goals. An integrated epidemiological track-
ing system capable of mapping all cases and coupled with knowledge of
specific malaria risk factors has allowed focussing antimalarial efforts on
remaining transmission foci. Although the primaquine regimen to kill
hypnozoites is well established, the multiple doses required do not pro-
mote compliance. In Mexico, it was found that changing the primaquine
regimen to intermittent monthly medication that was directly observed
greatly improved compliance and decreased relapses (
Rodriguez et al.,
2009
). Since effectiveness of primaquine is dependent only on the total
dose, ingested alternatives to daily dosing seem to work well. As a country
approaches elimination, intensive work with the few remaining cases as
an indicator of where transmission has been occurring as well as a means
of stopping future transmission seems to be a successful formula (
Danis-
Lozano et al., 2007
).
