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DDT finds favour in fight against malaria

Workers from the Limpopo Malaria Institute spray DDT on the inside walls of a house in Runnymede, 40km east of Tzaneen, Limpopo province, as part of an anti-malaria project.
Bill Corcoran/IRIN

After years of resistance, people living in the rural areas of South Africa are beginning to embrace the use of DDT as an effective agent in the fight against malaria-carrying mosquitoes.

John Kutama, sub-district manager of the Limpopo Malaria Institute, in Limpopo Province, has overseen annual indoor residual spraying for many years and remembers a time when villagers refused the controversial treatment, unsure whether the chemical would do them more harm than good.

The annual anti-malaria treatment involves spraying the interior walls of a house with dichloro-diphenyl-trichloroethane (DDT), a synthetic chemical that has been banned for decades in many countries because of its harmful effect on people and the environment, and the belief that there are alternative and less harmful insecticides, like pyrethroids, which are thought to be just as effective.

"They were too afraid to let us spray their walls - where the malaria carrying mosquitoes like to wait before feeding on those in the house - because of what they heard about DDT," Kutama told IRIN.

"But seeing the difference it makes has changed many people's minds," he said, as a team of sprayers worked their way through Runnymede, a village about 40km east of Tzaneen in Limpopo Province, a high-risk malaria area.

Long history of DDT use

DDT had been used in South Africa since 1946 and virtually eradicated malaria over the following decades. Nevertheless, the post-apartheid government succumbed to international pressure against the use of the long-lasting chemical in 1996 and replaced it with pyrethroids, which are effective for a shorter span.

However, after 4 years the health department reintroduced DDT into its anti-malaria programme after pyrethroid-resistant mosquitoes caused a localised malaria epidemic that led to 64,662 infections and 458 deaths in 2000.

''DDT has been used in South Africa since 1946 and virtually eradicated malaria over the following decades''

The presence of the Anopheles Phenestus mosquito, which feeds almost exclusively on humans, had not been recorded in South Africa for years but re-emerged in the east-coast province of KwaZulu-Natal when it became resistant to pyrethroids.

Although the mosquito's presence was not established in Limpopo or Mpumalanga, both provinces experienced huge increases in malaria cases between 1996 and 2000, which were attributed to a different malaria-carrying mosquito.

In 2001, on the back of DDT use as the main control substance in the three provinces - the country's main areas of malaria infection - the incidence of malaria declined nationally to 26,506 cases, and fatalities were reduced to 119.

Since the successes of 2001, health officials have kept faith with the cheaply produced chemical and in 2006 a total of 12,098 cases and 87 deaths were recorded; statistics for the first ten months of 2007 indicate that the number of malaria cases may be half those reported in 2006.

Despite DDT's unquestionable contribution to South Africa's successful anti-malaria programme, which also includes education about the mosquito-borne disease, the implementation of early response strategies and the destruction of mosquito breeding grounds, the continued use of DDT is a hugely contentious issue.

The dispute between those advocating DDT use and those in favour of a complete ban on the chemical centres on the pros and cons of its use. Worldwide, malaria affects 300 million people annually and causes nearly 3 million deaths, many of them children under the age of 5.

Opponents cite DDT use as unnecessary

International studies have shown that even non-occupational exposure to DDT can cause an array of medical irregularities, ranging from an increase in incidents of pre-term births and underweight babies to adversely affecting male sperm production.

According to opponents of DDT use, South Africa's indiscriminate use of DDT contravenes the country's obligations to the Stockholm Convention, a global treaty against using harmful chemicals, which states that according to World Health Organisation guidelines, DDT cannot be used if "locally safe, effective and affordable alternatives are available".

A 2006 report by the International POPs (persistent organic pollutants) Elimination Project (IPEP), a global network of non-governmental organisations that support the Stockholm Convention, accused the South African government of negligence because of its continued use of chemicals such as DDT.

''The present use of DDT in South Africa is unnecessary in the  Mpumalanga and Limpopo provinces, where the only malaria vector is the Anopheles Arabiensis, which can be effectively controlled with pyrethroids and other less toxic technologies''

"The present use of DDT in South Africa is unnecessary in the Mpumalanga and Limpopo provinces, where the only malaria vector [mosquitoes that transmit the disease] is the Anopheles Arabiensis, which can be effectively controlled with pyrethroids and other less toxic technologies.

"The report also questions the use of DDT in the KwaZulu-Natal Province without proper monitoring of the pyrethroid-resistant Anopheles Phenestus population following its re-emergence during the 1999-2000 malaria epidemic.

"It is likely that this specific malaria vector has once again been eradicated, as it was when the DDT indoor residual spraying programme was first introduced more than thirty years ago. There is no need to expose Limpopo's population to DDT, because the type of mosquito prevalent in the region can be dealt with effectively using less toxic technologies," the report said.

Philip Kruger, head of Limpopo's Malaria Institute, in Tzaneen, is aware of the arguments by opponents of DDT, but said the question of whether the province's malaria control programme should keep using DDT was an ethical one.

"I understand the arguments put forward, but to say that the Anopheles Phenestus does not exist in Limpopo and Mpumalanga is a dangerous assertion to make; we just don't know. In KZN [KwaZulu-Natal] they thought that vector had been eradicated, and nearly 500 people died there between 1999 and 2000," he told IRIN.

"These are deaths that could have been prevented; and I need to take responsibility for what happens in Limpopo. If people start dying here from malaria because we stop using DDT, what am I to tell their relatives?"

In its 2006 overview of its programme, the Limpopo Malaria Institute stated that 330 permanent spray operators and 180 seasonal workers, divided into 43 teams, carried out the spraying of 890,000 dwellings with DDT and pyrethroids.

Careful spraying

According to Kruger, because of the dangers associated with the insecticides they are not sprayed in a random manner, or in amounts harmful to the approximately 2.1 million people living in Limpopo's malaria-risk zones.

"Areas are not sprayed from a plane or anything like that; they are targeted by teams of sprayers, who are trained to spray in a manner that is safe for the occupant and detrimental to the mosquito.

"We in South Africa believe indoor spraying is one of the best approaches to fighting malaria, and we have ample evidence to prove it. While insecticide-treated nets have a role to play, you have to change people's behaviour.

''We in South Africa believe indoor spraying [of DDT] is one of the best approaches to fighting malaria, and we have ample evidence to prove it''

"There is evidence that in some places the nets are used exclusively by the head of the household, due to their status in the family, and they have also been used as fishing nets rather than to protect against malaria.

"Everything comes back to sustainability: nets work when they are being supervised, but when the supervision stops, problems occur," Kruger said.

Despite the successes achieved in South Africa's malaria-prone provinces over the past six years, Kruger said the eradication of malaria in Limpopo would only be possible if it "were an island".

Investigations in the province have revealed that between 20 percent and 40 percent of malaria cases were contracted outside the province's borders, and that human migration often carried the parasite from region to region.

"I can't see us regularly getting below the 3,000 [annual malaria cases] mark in the current setting. There is constant movement between Limpopo, northern Mozambique and Zimbabwe, as people have strong links across the borders because of the tribal system," he said.

"[Effective] tri-lateral malaria control strategies are in place between KwaZulu-Natal, Swaziland and southern Mozambique ... [but] it is more difficult here, as the region is a gateway into the country from the rest of the continent."

bc/go/he

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