Malaria Stand van Zaken

6. How effective is malaria control?

• 6.1 Can malaria control be properly evaluated from routine surveillance data?
• 6.2 What has been the impact of malaria control the WHO African Region?
• 6.3 What has been the impact of malaria control in other parts of the world?

6.1 Can malaria control be properly evaluated from routine surveillance data?

In the WHO World Malaria Report 2008, the impact of malaria control is evaluated based on annual records of malaria cases and deaths from national surveillance reports. The data are highly variable in quality but are the most abundant source of information on the effects of malaria control worldwide. These data are used to see if the number of malaria cases and deaths are changing over time, and whether any changes are due to specific prevention and treatment measures.

Information on the numbers of patients, laboratory tests, and malaria deaths, is available for the period 2001-2006 for most endemic countries. For a few countries in the WHO African Region, there is also information available on the scale and timing of interventions and on numbers of cases and deaths before and after such prevention and treatment interventions. Although these are not scientifically controlled experiments, they give an indication of the effectiveness of anti-malaria policies.

It is important to bear in mind that changes could be due not only to malaria control efforts, but also to other factors such as improvements in surveillance or changes in the weather and other environmental conditions that could affect the transmission of the disease. In any case it seems that some countries implementing aggressive prevention and treatment programmes have reported significant reductions in the malaria burden.

This text is a summary of: WHO, World Malaria Report (2008) ,
5. Impact of malaria control, Evaluating malaria control from routine surveillance data, p.27

6.2 What has been the impact of malaria control the WHO African Region?

In the WHO African Region, the reported number of malaria patients attending, but not staying in clinics increased steadily from 3.2 million in 2001 to 8.4 million in 2006, and hospital admissions and deaths due to malaria more than doubled over the same period. This increase most likely reflects improved surveillance or more complete records for recent years.

Since control campaigns in most African countries had not reached large proportions of the population by 2006, an overall reduction in the malaria burden in the region is not yet expected. However, in six countries or parts of countries the number of malaria cases and deaths declined and nationwide effects of malaria control were particularly clear in four of those:

• In Eritrea, the distribution of insecticidal nets, the annual rounds of indoor spraying as well as the distribution of anti-malarial medicines coincided with a drop in reported malaria cases and deaths. Between 2001 and 2006, the number of people admitted to hospital with malaria fell by 64%, that of malaria patients who were not staying overnight by more than 90% and that of malaria deaths by approximately 80%. These local trends could be due to environmental or other factors but are most likely due to the malaria control measures.
• Between 2001 and 2006, efforts to control malaria in Rwanda seem to have had no effect. However, malaria cases and deaths declined rapidly after the distribution in 2006 of long-lasting insecticidal nets and artemisinin-based combination drugs.This trend was observed in a number of health facilities and needs to be confirmed on a national basis.
• In 2005 and 2006, there were enough nets and anti-malarial drugs in Sao Tome and Principe to protect and treat nearly the whole population. Compared to the average for 2001-2003, the number of confirmed malaria cases in 2006 declined by more than 80%, and the number of deaths by more than 90%.
• In Zanzibar, improved access to artemisinin-based combination drugs since September 2003 onwards reduced malaria across the island and, by 2006, cases and deaths had diminished by more than 80% compared to 2001-2002. The decline could be partly due to less reporting but there is some evidence that these changes are due to real improvements in malaria control.
• In Madagascar, preventive measures have approximately halved the numbers of reported cases and deaths between 2001 and 2007. However, it is possible that this decline was due to less reporting rather than to an improvement in control.
• In Zambia, a country heavily affected by malaria, efforts to control the disease with insecticidal nets, indoor spraying, and anti-malarial drugs resulted in the numbers of both cases and deaths decreasing at an average of 9% per year between 2001 and 2006. This decline in malaria is very likely due to improved control.
• In other African countries where a high proportion of people have access to anti-malarial drugs or insecticidal nets, such as Ethiopia, Gambia, Kenya, Mali, Niger and Togo, routine surveillance data do not yet show, unequivocally, the expected reductions in morbidity and mortality. Either the data are incomplete, or the effects of interventions are small.

This text is a summary of: WHO, World Malaria Report (2008) ,
5. Impact of malaria control, Impact of malaria control in the WHO African Region, p.27-29

6.3 What has been the impact of malaria control in other parts of the world?

Between 1997 and 2006, malaria cases declined in at least 25 endemic countries outside the WHO African Region. In 22 of these countries, the number of reported cases fell by 50% or more during that time period, in line with WHO targets. In addition, six countries - Cambodia, Laos, Philippines, Suriname, Thailand and Viet Nam - are currently on track to meet the WHO targets of reducing malaria deaths by at least 50% by 2010. In some instances, these declines in malaria cases and deaths can be attributed to control campaigns but, in others, the cause is not so clear.

For instance, in the WHO Region of the Americas, the reduction in malaria in some countries (Belize, Honduras, Nicaragua, Peru, Suriname, Argentina, El Salvador and Mexico) coincided with improved control measures. However, malaria has not declined in the three countries with the highest number of cases: Bolivia, Brazil and Colombia.

In the WHO Eastern Mediterranean Region, the countries that have shown the greatest reductions in malaria cases are those where the national governments have made the strongest political and financial investments in malaria control. However, in six of the region’s most affected countries (Afghanistan, Djibouti, Pakistan, Somalia, Sudan and Yemen) there is little evidence that the efforts made have had any effect.

Three quarters of malaria cases in the WHO European Region are in Tajikistan and in Turkey, particularly along the borders with Iraq and Syria. However, in both countries malaria has declined sharply since the 1990s as a result of indoor insecticide spraying and prompt medical treatment. At present, Tajikistan is the only place in the WHO European Region where transmission of the infectious malaria agent P. falciparum occurs.

In the WHO South-East Asia and Western Pacific Regions, recent reductions in malaria cases and deaths have been associated with the targeted use of insecticidal nets, prompt diagnosis and effective treatment.

This text is a summary of: WHO, World Malaria Report (2008) ,
5. Impact of malaria control, Impact of malaria control in other regions, p.30-31