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

MONITORING / 35
during recent years (see pages 14 & 22) especially in Papua New
Guinea, the Philippines, Thailand and Viet Nam.
Problems
Prior antimalarial treatment of the patients and failure of
the electrical power supply, even where portable generators were
used, rank highest among the problems encountered with the
method. Other difficulties pertain to the scarcity of suitable
cases (trophozoites too young, parasite densities too low or too
high), the need for the blood sample to be taken by venipuncture,
the scarcity of qualified manpower, the cost of travel and of fuel
for the generators as well as bacterial contamination and the
failure of equipment other than the generators. In several
instances the exact cause of test failure could not be
determined. Of a total of 1588 tests carried out during 1978-1980
in various countries of the Regions from which such information is
available, 540 (34%) have failed. There was no significant
improvement in this rate over the years, suggesting that this
failure rate is more or less inherent to the technique.
Delays in obtaining government agreement and signatures on
the CTS agreements were a major obstacle to the implementation of
planned activities. While availability and despatch of testing
material have been quite sat isfactory, long delays in clearing at
air and sea ports have further hampered progress in a number of
instances.
Technical Suggestions
(a) For defibrination, the McCartney bottle of 25 ml
capacity is preferable to the easily breakable Erlenmeyer flasks.
(b) For the same reason sterile plastic disposable pipettes
of 1 ml capacity should replace the glass pipettes.
(c) Fluctuations of electric power and portability and cost
of mobile power sources proved to pose major technical
difficulties. A suitable incubator or waterbath operated from a
rechargeable battery would probably resolve some of these problems.
(d) Temperature fluctuations during incubation should be
monitored routinely at least with a maximum/minimum thermometer.
An electric clock wired into the incubator/waterbath circuit
should be used to indicate the duration of power failure.
(e) The correlation between the age of the ring stages and
the time required for schizont maturation in the control vials
should be studied 1n order to provide guidelines for optimum
incubation.
(t) The definition of a
"successful" in vitro sensitivity