Chapter 12 of 16
Medicines are losing their effectiveness
Initiative: Detecting and containing resistance
|The dramatic upsurge
in the spread of drug-resistant microbes over the past decade is undermining
today's efforts to control infectious diseases. As diseases once thought to be under
control become increasingly resistant to the arsenal of available drugs, the spectre of
incurable infectious diseases looms large. The fight against five of the six deadliest
diseases - TB, malaria, pneumonia, cholera and HIV - is severely affected.
Although antimicrobial resistance affects industrialized and developing countries alike, its impact is far greater in developing countries. The problem is that the switch from normally less expensive first-line drugs to second or third-line drugs involves a dramatic escalation in the price of treatment. In some of the poorest countries, the prohibitive cost of lengthy treatment and replacement drugs means some diseases are too expensive to treat.
In low-income countries - which may spend no more than $7 per capita on health - the cost of treating a case of multidrug-resistant TB, likely to be as high as $1 500- $4 000 a patient, is out of reach. In some Asian countries, the cost of treating a child for bacterial meningitis increases from $20 to $110 whenever second-line drugs are needed. And the cost of treatment for acute respiratory infections - the most frequent cause of child deaths - increases from $5 to $40 for a course of antibiotics.
In addition, multidrug-resistant forms of diseases can become untreatable in any country - at any price - once the options have been exhausted. Pharmaceutical manufacturers have found it difficult to develop new antibiotics and other drugs fast enough to replace those that have become ineffective.
Tuberculosis: A 1997 report on anti-tuberculosis drug resistance pinpointed "hot zones" around the world where a significant percentage of cases are resistant to the most commonly prescribed drugs. Unless checked, this could propel a wave of tuberculosis that is difficult - even impossible - to cure using drugs. In some countries in eastern Europe, more than one in five TB patients have multidrug-resistant TB.
Malaria: Chloroquine - once the first-line treatment - is no longer effective in over 80 of the 92 countries where malaria is a major public health problem. In some places in Africa people use chloroquine more often than aspirin - taking it regularly for minor fevers, aches and pains. This increases the rate of resistance. To make matters worse, mosquitos are now resistant to the three most commonly used insecticides.
Pneumonia and meningitis: In some countries, up to half of all cases of the most common forms of meningitis and pneumonia are now resistant to penicillin. Even under optimal treatment, 10-30% of patients with meningitis suffer permanent brain damage depending on age, treatment and infectious agent.
Dysentery: In some countries, up to 90% of all cases are resistant to the two first-line drugs. In central and southern Africa epidemics of dysentery over the past decade - including those in refugee camps - have included drug-resistant forms of the disease. Up to 15% of those infected died.
Gonorrhoea: In some countries, 98% of gonorrhoea cases are resistant to penicillin. If left untreated, gonorrhoea heightens the risk of infection with HIV and can cause infertility, miscarriages, stillbirths and blindness.
Hospital infections: Hospital infections - acquired by patients after admission to hospital are now a leading cause of death in some countries and up to 60% of hospital infections are caused by drug-resistant microbes. In the United States, 14 000 patients die every year from drug-resistant bacteria they picked up in hospital.
Widespread misuse of antimicrobial drugs lies at the root of this crisis. This happens in developing and industrialized countries alike. Overprescribing is rife. Antibiotics are often prescribed for the wrong kind of infection. The dosage may be wrong and treatment may be prescribed for the wrong length of time.
In Canada and the United States studies indicate that approximately half of all outpatient prescriptions for antibiotics are unnecessary. In a study in Viet Nam, over 70% of patients were given inadequate dosages.
Even where the prescribed treatment is correct it may not be followed. Once the symptoms disappear people often stop taking the antibiotics - increasing the risk of developing drug-resistant forms of disease. In developing countries antibiotics can be bought without a prescription and self-medication is commonplace.
To make matters worse, some of the drugs on sale today are counterfeit. Medicines for infectious diseases are among those most likely to be faked. Billions of dollars are believed to be involved. As well as causing deaths, counterfeit antimicrobial drugs with deliberately reduced amounts of the active ingredient contribute to the problem of drug resistance through failed treatments.
Meanwhile use of antimicrobials outside human medicine intensifies the problem. About 50% of antimicrobials are used in animal husbandry, agriculture and horticulture. Although their effect on human health is not yet fully known, WHO's experts have recommended that antimicrobials used in humans should not be used as growth promoters in animals.
The impact of antimicrobial resistance could be greatly reduced through the use of Integrated Management of Childhood Illnesses, better prescribing practices, training for health workers, public education, user-friendly packaging of drugs to encourage adherence and the development of simple-to-use tests that permit accurate diagnosis. It is also critical to establish national surveillance systems which can detect and respond to antimicrobial resistance at an early stage.
|© World Health Organization 1999
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