Emerging drug-resistant strain a fierce foe in malaria battle

Local and international health organisations are struggling to prevent a wider outbreak of the disease which is becoming increasingly prevalent in border areas and for which conventional therapies have proven useless 

6th May 2012

Writer: Tunya Sukpanich 

Bangkok Post

Malaria remains a public health concern in Thailand even though the number of infected patients has declined tremendously from 125,000 in 1998 to 35,600 in 2007 and 34,002 in 2011. What's causing alarm among officials now, however, is the emerging resistance of Plasmodium falciparum _ the parasite responsible for malaria _ to conventional drugs.

GAINING STRENGTH: A woman recovering from malaria rests at her home. Malaria is declining in Thailand but a drug resistant strain is on the rise in border areas.

More than 50% of malaria cases recorded in Thailand involve Myanmar and Cambodian citizens working here or engaging in cross-border trade.

The areas along the Thai-Cambodian border, especially in the provinces of Chanthaburi and Trat, and Pailin in Cambodia are considered the epicentre of multi-drug resistance.

''Malaria drug resistance has been found here before other areas. The parasite resists all drugs now in use and we fear that it may spread to other areas,'' said Dr Vichai Stimai, director of the Vector-borne Disease Control Office of the Public Health Ministry.

A study by the ministry has found the current artemisinin-based combination therapies can cure only 78% of patients along the Thai-Cambodian border. This is below the acceptable success rate of 90%. To solve this problem, international health organisations have provided financial assistance to the Thai government to try to eradicate the disease.

For example, the Public Health Ministry has received US$80 million (2.5 billion baht) to implement its five-year project from the Global Fund, an international financing institution which helps countries fight Aids, tuberculosis and malaria. In addition, the Bill Gates Foundation has provided $4 million for a two-year project. USAID provides $340,000 annually to Thailand and about five times that amount to Myanmar to eradicate malaria.

According to a study published by the Lancet last month, scientists have found malarial drug-resistant strains in areas along the Thai-Myanmar border.

The Global Malaria Programme urged the team of scientists responsible for the report, led by professor Francois Nosten, to conduct a follow-up study on whether the drug-resistant parasites have spread from the same area where the first drug-resistant strains were found earlier along the Thai-Cambodian border.

In the Thai border province of Tak, where there are a large number of migrant workers and traders from Myanmar, more than 12,160 malaria patients _ the highest number in the country _ sought treatment at clinics and hospitals last year. Of these patients, almost 80% were from Myanmar.

Chantarapa Nontasee Chindathong, a social worker at Umphang Hospital in Tak, said last year the hospital provided treatment to 830 malaria patients. Almost 70% were non-Thais with no access to any health plan.

''They are poor people. The hospital has to shoulder the financial burden,'' she said.

Dr Vichai Stimai.

In the southern coastal province of Ranong, which is also home to a large number of migrant workers from Myanmar, the number of patients has declined.

But at the same time more malaria patients are showing resistance to the standard treatment. Dr Vichai said that 80% to 87% are cured while 20% respond poorly to to the artemisinin-based combination.

Malarial drug resistance may recur several times.

In 2001, the World Health Organisation (WHO) recommended the use of artemisinin-based combination therapies in countries where falciparum malaria had become resistant to chloroquine and other anti-malaria medicines.

However, many countries still use artemisinin as a monotherapy drug because of its low price.

The WHO first issued a warning about the threat of artemisinin resistance in the Greater Mekong subregion in 2005, after routine efficacy studies showed that the P falciparum parasite was taking longer to clear from patients' bloodstreams. Then the first cases of confirmed artemisinin resistance were found in western Cambodia, along the Thai-Cambodia border in late 2006.

The WHO requested that drug companies stop marketing artemisinin monotherapies following evidence of potential resistance to the drugs. However, the WHO maintains the efficacy of the therapy for malaria treatment in border areas. Despite artemisinin resistance, the WHO says other drugs included in the combination are still effective, even though it takes longer to treat the patient.

According to Dr Vichai, part of the problem is the incorrect use of artemisinin, and the use of fake or substandard drugs. One solution, he said, is to set up many malaria clinics to educate people on how to protect themselves from the disease.

At present such clinics have been established in 460 villages. ''This enables more people in remote areas to get medical treatment and good quality medicine,'' said Dr Vichai.

In addition, the health officers provide blood checks for people in risk areas. Anyone infected with the disease will be treated free of charge.

But containing the resistant strains is not an easy task in a highly mobile population. ''We have problems with Burmese workers who move frequently from place to place, especially those who come to work in rubber plantations,'' said a health worker in Ranong.

When it is confirmed that artemisinin-based combination therapies are not as effective as before, healthcare providers try to provide new treatments for the patient. ''It would be unjust for the people if we continue to cure them with ineffective medicine,'' said Dr Vichai.

Different malarial treatments, including malarone combination therapy, have been been given to patients along the Thai-Cambodian border where the drug resistance problem first appeared a few years ago. The treatment costs about 2,700 baht for a three-day dose, compared to 180-200 baht for the artemisinin-based treatment. Treatments other than those that are artemisinin-based are strictly controlled and available only at university and government hospitals.

These alternative therapies have also been been used for malaria patients in Chanthaburi and Trat provinces, and will soon be used in Pailin in Cambodia on a temporary basis. ''In addition to a successful cure for patients, it is hoped that the resistant strain will be controlled or destroyed [by alternative therapies],'' said Dr Vichai, adding that these therapies should help contain the resistant strains and keep them from spreading to other areas as is feared.

Meanwhile, Mahidol University's tropical medicine faculty, which has been doing ongoing research into anti-malarial drugs, has provided therapies that have been used and followed up on in Thai-Myanmar border provinces.

Dr Vichai said that more changes need to be made in the treatment of malaria in the next few years to benefit patients and prevent new outbreaks, but he cautioned that thorough consideration should be given before any changes are made.