Published Date: 2001-01-03 23:50:00
Subject: PRO> DDT & malaria control - South Africa
Archive Number: 20010103.0019
DDT & MALARIA CONTROL - SOUTH AFRICA
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See Also
2000------
DDT & Malaria control - South Africa 20001220.2236
1998
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DDT: use in control of emerging diseases (03) 19980115.0107
DDT: use in control of emerging diseases (04) 19980116.0123
1997
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DDT: use for control of emerging diseases 19971204.2429
DDT: use for control of emerging diseases (02) 19971209.2451
Date: Wed 3 Jan 2001
From: Rick Speare <richard.speare@jcu.edu.au> and David Durrheim
<daved@social.mpu.gov.za>
Source: Fourth Collaborative Meeting on Malaria Control in South Africa -
Kruger Park 24 Nov 2000 [edited
Chloroquine Resistance, DDT and Malaria Control - South Africa
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Reintroduction of DDT for house spraying for malaria control was discussed
during the recent Fourth Collaborative Meeting on Malaria Control in South
Africa held in Kruger Park on 24 Nov 2000. In South Africa malaria is
predominantly seasonal, largely due to _Plasmodium falciparum_ (Pf), and
confined to the north-east of the country, in low-altitude foci in
Kwazulu-Natal (KZN), Mpumalanga, and Northern Provinces mainly bordering
Mozambique.
Owing to dramatically escalating incidence rates of malaria in KZN, the
reappearance of winter malaria in this area and high-level resistance to
synthetic pyrethroids, KZN recommenced indoor DDT spraying of traditional
houses in April 2000. By November 2000, the monthly malaria cases had
fallen to the same level of previous years, suggesting that DDT spraying
had had a significant impact, but this may be better judged during the
high-risk months at the beginning of 2001.
Use of deltamethrin for indoor spraying of western-style houses continues
in the province. At the meeting Jotham Mthembu, the head of malaria control
in the KZN Department of Health, addressed the question of pressure to ban
the use of DDT for indoor spraying for malaria control. The
re-establishment of _Anopheles funestus_ (previously eradicated by DDT
spraying) appears to be a major reason for the increase in malaria. This
particular malaria vector now has high levels of insecticide resistance in
KZN, has been widely captured in homes sprayed with deltamethrin, and has
been found to be resistant to synthetic pyrethroids (50%) and propoxor
(48%), but not resistant to DDT in KZN.
Jotham argued that little DDT is used in malaria control program spraying
compared with agricultural use; that it is targeted indoors and thus does
not significantly contaminate the outside environment; and that it saves
lives by reducing malaria risk. He proposed that people who face the risk
of severe illness from malaria should have a strong voice in the forums
attempting to stop use of DDT for indoor spraying. To date, bed nets have
been impregnated only with synthetic pyrethroids; thus with the high level
of resistance to this group of insecticides, the effects of impregnation
will be minimal, and may in theory increase selection pressure for resistance.
The rapid emergence of multidrug-resistant Pf was also discussed at the
Meeting. Chloroquine resistance is widespread and chloroquine is not
recommended for prophylaxis or treatment. In KZN sulfadoxine/pyrimethamine
(SP) resistance is at a serious level of greater than 60% at 42 day
follow-up, meaning that clinical efficacy is unsatisfactory for a majority
of patients. In Mpumulanga SP produces a 95% parasitological cure, a level
similar to that documented at its introduction, and is still effective
clinically. A worrisome effect of SP is its ability to cause an increase
the number of gametocytes about 2-3 weeks after use. These appear to be
viable, and hence use of SP may enhance transmission.
The South East African Combination Artemisinin Therapy (SEACAT) project to
investigate the field effectiveness and impact of combination therapy
against uncomplicated malaria has commenced in South Africa. The major aim
is to use the rapidly parasiticidal artemesinins in combination with SP,
mefloquine or other first-line therapy to prevent development of drug
resistance, effect cure and interrupt transmission in an affordable way.
--
Assoc Prof Rick Speare
School of Public Health and Tropical Medicine
James Cook University
Townsville Australia
<richard.speare@jcu.edu.au>
and
Assoc Prof David Durrheim
Consultant on Communicable Disease Control
Department of Health, Nelwpruit
Mpumulanga Province, South Africa
<daved@social.mpu.gov.za>
[This report on the Nov 2000 meeting raises several important questions.
Concerning DDT, it should be noted that on 10 Dec 2000 delegates from 120
countries meeting in Johannesburg signed a treaty to ban "persistent
organic pollutants," but agreed to particularly exempt DDT because it is
being used for malaria control.
The suggestion that SP treatment may enhance transmission is debatable. The
most recent work (Robert et al. Am J Trop Med Hyg 2000,62:210-16) shows
that the use of SP and chloroquine in chloroquine-resistant _P. falciparum_
infections results in an increased number of gametocytes day 7 after
treatment. However, it was also found that the infectivity of the
gametocytes after SP treatment was reduced, suggesting that increased
transmission is not seen as long as the parasites are susceptible to SP. It
has previously been found that patients with chloroquine-resistant _P.
falciparum_ malaria not only produce an increased number of gametocytes
after chloroquine treatment, but also that these gametocytes are more
infectious to the mosquito (Hogh et al. Am J Trop Med Hyg 1998,58:158-176).
This finding is confirmed in the Robert et al. paper, emphasizing that
early and efficient treatment is of key importance for stopping
transmission of resistant _P. falciparum_ malaria in Africa. - Mod.EP
...................................ep/pg/ds
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