SECTION II:
|
I. AFRICA II. ASIA
III. THE AMERICAS |
MALARIA CONTROL, BY REGION
II. ASIA
- Parasitological species of recorded malaria cases: P. falciparum 35%, P. vivax
- Principal malaria vectors: A. culicifacies, A. minimus, A. annularis, A. dirus, A. fluviatilis, A. maculipennis, A. sacharovi, A. superpictus, A. farauti
- Estimated proportion of population at risk of malaria: 49% (21)
- Estimated contribution to the global burden of clinical malaria cases: 38%
- Estimated contribution to the global burden of clinical falciparum malaria cases: 25% (2)
- Estimated contribution to the global malaria mortality burden: 10% (1)
- Main control strategies: prompt and effective treatment, (focal) IRS, larviciding, epidemic preparedness, ITNs
1. Disease burden and control efforts in:
• Eastern Mediterranean
In major parts of the Eastern Mediterranean, the malaria situation had deteriorated over the 30 years before the inception of RBM (30). A chronic shortage of resources for the health sector and complex emergencies had nearly stopped malaria control in some of the affected countries, and resistance to commonly used insecticides— except pyrethroids—and antimalarial drugs had emerged.
As of 2004, over 40% of the population in this subregion is at risk of malaria. The malaria problem is most serious in Afghanistan, a complex emergency situation (51), and Yemen, where up to 60% of the population might be at risk of falciparum malaria (21) and where internal resources for malaria control are limited (Table 8).
Table 8. Malaria control targets in the Eastern Mediterranean Countries Type of malaria situation Target 
Source: (30). |
Countries with low-to-moderate endemicity include the Islamic Republic of Iran and Saudi Arabia, which have functional health systems and relatively wellestablished control programmes. In the complex emergency situations of Afghanistan and Iraq, the malaria problem is aggravated by the displacement of populations caused by civil strife resulting in an increased risk of epidemics, and by the destruction of health facilities and shortages of supplies and trained staff.
Oman and Syrian Arab Republic have only residual malaria transmission and imported cases (30). High rates of population movements complicate the control of malaria in border areas of affected countries such as between Iraq, Syrian Arab Republic and Turkey, between Saudi Arabia and Yemen, and between Afghanistan, Islamic Republic of Iran and Pakistan. These countries have therefore started coordinating their control activities in border areas.
Between 1998–1999 and 2002–2003, total expenditure on malaria increased from less than US$ 3 million to over US$ 8 million. The governments of Afghanistan (51), Pakistan and Yemen (Box 8) revitalized their malaria control programmes since the inception of RBM, with support from United Nations agencies, bilateral agencies and recently from the Global Fund to Fight AIDS, Tuberculosis and Malaria (GFATM). All countries in which malaria is still transmitted have national-level multi-year strategic plans. Control strategies in all countries include diagnosis and prompt and effective antimalarial treatment, IRS, epidemic preparedness and strengthening surveillance systems. Afghanistan, Pakistan, Saudi Arabia and Yemen have national strategies for ITNs. In 2003, Pakistan introduced a malaria early warning system, based on weekly reporting of cases in epidemic-prone districts.
The reported case rates pooled across countries remained fairly stable between 1990 and 2003 (Fig. 19). Actual case rates are likely to be much higher—e.g. up to an estimated 20-fold in Yemen—since many of the cases are treated outside the public health system, which in most countries remains the main or only source of health statistics. However, in certain high-risk areas targeted for the most intense malaria control such as in Saudi Arabia and Yemen, malaria case rates have started to fall in recent years. The proportion of cases reported to be caused by falciparum malaria infection was reasonably constant over time within each country, but varied from 12% in Afghanistan to 97% in Yemen. In Turkey, the reported case rate has continued to fall gradually since its peak in 1994; control activities carried out since 2002–2003 include capacity building, disease management and prevention, drug-efficacy monitoring, malaria surveillance, health education and community participation.
Some of the challenges for the Eastern Mediterranean countries include expanding successful programmes begun in specific high-risk areas to other areas, improving monitoring and surveillance systems, and ensuring continued financial support needed to fund effective antimalarials and their availability from local providers (30). There is a need for cross-border coordination between Iraq, Syrian Arab Republic and Turkey to reduce malaria (re)introduction from highly endemic southern Turkey.
BOX 8. VECTOR CONTROL AND STRENGTHENED SURVEILLANCE IN SOCOTRA ISLAND, YEMEN In Yemen, the reported malaria case rate rose from 1 per 1000 person per year in 1990 to a high of 160 per 1000 person per year in 1999. Social unrest during the 1990s brought about an almost full halt to antimalarial activities, and heavy rainfalls contributed to malaria epidemics in 1996 and 1998. In October 2000, the NMCP reinstituted malaria control with assistance from WHO, GFATM and various NGOs. A community-wide effort identified high-risk areas suitable for vector control by weekly larviciding and biannual IRS. In the high-risk area of Socotra Island, control measures also included increased surveillance and improved training and health education campaigns. Active community participation in these efforts was essential. Key community leaders, United Nations agencies and other interested partners provided guidance through public health education campaigns and coordinated the control efforts. Trained community members, who were offered a daily rate for increased incentive, carried out vector control campaigns. The NMCP and responsible agencies provided intensified supervision of activities. The reported burden of malaria in Socotra Island has remained low in the subsequent three malaria seasons (Fig. 18), despite intensified efforts to identify cases through active case detection and microscopy. Figure 18. Reported slide-confirmed malaria cases and slide-positivity rates from Socotra Island, Yemen, 2000–2003 
Source: Yemen NMCP. |
Figure 19. Standardized reported case rates in malaria-endemic countries in the Eastern Mediterranean, by calendar year, 1990–2003 
Numerators are based on confirmed authochthonous cases. Country-specific rates are shown for countries that reported a non-zero number of cases or deaths; the regional average is based on these countries weighted by population size (52). |
• Central Asia and Transcaucasia
Central Asia and Transcaucasia have long been subject to seasonal malaria transmission, which even the historic malaria eradication campaign of the 1960s never completely interrupted. Since the early 1990s, the incidence of malaria, which is mostly caused by P. vivax, has risen. The residual reservoir of malaria infection, aggravated by political and socioeconomic situations, mass population migration, extensive development projects and a nearly complete discontinuation in activities for malaria prevention and control, created conditions favourable for malaria transmission. As a result, epidemics of relatively large scale for this region ocurred in Azerbaijan and Tajikistan, while Armenia, Georgia, Kyrgyzstan and Turkmenistan faced smaller-scale epidemics. In recent years, endemic falciparum malaria has returned to Tajikistan and is now well established in the southern part of the country, although still focal and primarily affecting the most remote rural areas. In 2004, the first autochthonous cases of falciparum malaria were reported in the southern part of Kyrgyzstan bordering Uzbekistan. Sporadic cases of autochthonous malaria are reported every year in Kazakhstan, Uzbekistan and some parts of the Russian Federation, and these countries remain vulnerable to a resumption of malaria transmission.
A scaling up of RBM interventions in Central Asia followed the epidemic that occurred in Kyrgyzstan in 2002. The emphasis has been on Kyrgyzstan, Tajikistan and Uzbekistan. In 2003–2004, these countries, as well as Kazakhstan and Turkmenistan, reaffirmed their commitment towards implementing malaria control based on well-defined national and regional priorities. Key elements of national control policies are vector control by IRS and epidemic preparedness, as well as ITN use in Armenia, Azerbaijan, Kyrgyzstan and Tajikistan.
Grants from the GFATM will help strengthen malaria control in Uzbekistan (more than US$ 2.5 million over 5 years) and Georgia (more than US$ 800 000 over 3 years), where the reported case rate rose steeply until 2002. In contrast, Armenia and Azerbaijan still have insufficient resources available to manage the malaria problem. In response to the 2002 epidemic, Kyrgyzstan reinforced surveillance, targeted IRS and improved disease management on a large scale in malaria-affected areas. In 2003, the number of reported malaria cases decreased substantially (Fig. 20).
Averaged over the region, after a peak incidence of around 0.45–0.72 annual reported cases per 1000 between 1996 and 1998—reflecting peaks in Armenia, Azerbaijan and Tajikistan—the rate of reported cases steadily declined to around 0.11 per 1000 in 2003. This is around 10-fold higher than the level recorded in 1991–1992, but completeness of reporting is likely to have varied during the decade due to socioeconomic and political changes (Fig. 20).
Figure 20. Standardized reported case rates in malaria-endemic countries in Central Asia and Transcaucasia, by calendar year, 1990–2003 
Numerators are based on confirmed, autochthonous cases. Country-specific rates are shown for countries that reported a non-zero number of autochtonous cases or deaths; the regional average is based on these countries weighted by population size ( 52). |
• South-East Asia
In the 1960s and early 1970s, the Global Eradication Programme reduced malaria incidence to low levels by extensive IRS and large-scale use of antimalarial drugs, but transmission never completely ceased. The disease re-emerged in the 1980s and 1990s, when vector control became less intensive and resistance to most of the commonly used conventional drugs (chloroquine, sulfadoxine–pyrimethamine) and insecticides (DDT, malathion) spread rapidly. Epidemics occurred along the Thai–Cambodian border between 1979 and 1983 coinciding with population movements during the civil war in Cambodia in 1987 and in Sri Lanka in 1990–1992. In India, urban malaria has emerged as a serious health problem in several states. Rapid urban growth and labour migration led to some of the epidemics that have occurred with increasing frequency since 1995. Labour-related movement of nonimmune migrants into forests has contributed to epidemics in Myanmar and Thailand, and adult men are the main group at risk in such areas. Currently, Bangladesh, Bhutan, India, Indonesia, Myanmar, Nepal, Sri Lanka, Thailand and Timor-Leste have endemic falciparum malaria, and transmission of vivax malaria reappeared in the Democratic People’s Republic of Korea in the 1990s.
Malaria control was resumed or reintensified in Thailand in the early 1980s, in Maharashtra State in India in 1995, in the Democratic People’s Republic of Korea in 1999, in Bangladesh in 1998, on central Java in Indonesia in 2001 (53) (Box 9) and in Sri Lanka in 2003 (Box 10). The total budget, from national funds and other sources, increased from US$ 66 million across 6 countries reporting such data in 1998 to US$ 122 million across 9 countries reporting data. As of 2004, 5 countries have received support from the GFATM for malaria control.
South-East Asia has the highest rates of drug and insecticide resistance in the world. Multidrug resistance emerged earliest in this part of the world and is particularly prevalent near international borders. All countries monitor drug resistance in surveillance sites. In light of drug resistance, Bangladesh, Bhutan, Indonesia, Myanmar and Thailand have now adopted ACT as the national policy for first-line treatment of uncomplicated falciparum malaria. Drug policies for the public health sector alone are not enough; a large proportion of patients obtain treatment in private health facilities or from pharmacies or local shops, where the sale of counterfeit and substandard drugs is common. Timely revisions and effective implementation of treatment guidelines, coupled with improved access through specialized malaria clinics, have been crucial for reducing malaria mortality and clinical incidence in Thailand over the past two decades. Under RBM, rapid diagnostic tests were introduced for malaria diagnosis in remote areas in Nepal and Thailand.
Vector control through IRS for selected areas and epidemic preparedness and surveillance are key control strategies in all affected countries. In addition, larvivorous fish are used for vector control in some areas of India, Myanmar and Sri Lanka. Over the past 7 years, Bhutan, Indonesia, Myanmar and Thailand switched from using DDT and/or organophosphates to using pyrethroids; Sri Lanka decreased the use of DDT, while increasing the use of pyrethroids.
ITN distribution has begun in all endemic countries except Nepal. Since 1999, at least 3.6 million nets were distributed and over 4.3 million existing nets were (re-) treated. An ITN distribution programme in the Khagrachari Hill District of Bangladesh halved the number of reported clinical cases within 3 years of scaling up ITN coverage.
Figure 21. Standardized rates of reported malaria cases (a) and deaths (b) in malariaendemic countries in South-East Asia, by calendar year, 1990–2003  
Numerators are based on confirmed, autochthonous cases. Country-specific case rates are shown for malaria-endemic countries that provided feedback during the preparation of this report and that reported a non-zero number of cases; country-specific deaths rates are shown for all countries with a rate of > 0.1 per 100 000 persons per year in at least one year. Regional averages are based on all countries including those not providing feedback to WHO, weighted by population size (52). No data are available for the period 1990–1994. |
In India, the national reported malaria case rate had by 2003 fallen to below the 1990 level, after a peak in 1995–1996, when many malaria outbreaks occurred. Across most other countries, the case reporting rate has slightly fallen since 1990–1991. For Bhutan, India and Thailand, this decline was paralleled by a decrease in the death reporting rate between 1995 and 2003 (Fig. 21). The proportion of cases caused by falciparum infection remained reasonably constant between 1990 and 2003 in Bhutan, Myanmar, Nepal and Sri Lanka, slightly decreased in Thailand, but tended to increase in Bangladesh, India and Indonesia (Fig. 22).
Figure 22. Percentage of cases reported as P. falciparum or as mixed infection with P. falciparum and another Plasmodium species, for selected countries in South-East Asia, 1990–2003 
|
A major challenge for malaria control programmes in South-East Asia is to ensure access to high-quality-assured drugs according to updated national drug policies through all types of providers. Furthermore, rapid diagnostic tests or microscopy and pre-packaged ACT are to be provided through public health systems, including in remote rural villages.
The tsunami of 26 December 2004 raised concern about an increased risk of epidemics in some coastal areas of India, Indonesia, Myanmar and Sri Lanka. Accumulations of mixed salt and fresh water might encourage breeding of A. sundaicus, an important vector in many affected coastal areas. The fact that survivors of the tsunami are living under crowded and makeshift conditions is likely to increase exposure to these malaria vectors (54). Initial actions of larviciding appear to have prevented immediate outbreaks and, as of March 2005, there is no evidence of an increase in malaria cases. Active surveillance is ongoing to assess the longer-term impact of the tsunami on malaria transmission and disease burden.
BOX 9. INDONESIA CONFRONTS MALARIA EPIDEMICS THROUGH OUTREACH IN POOR RURAL AREAS The 1997 economic crisis in Indonesia brought increased poverty, a reduction in health spending, the breakdown of malaria control efforts—in particular a dramatic cutback in IRS—and the re-emergence of malaria in areas where the disease was previously under control. There was also a decrease in surveillance and monitoring, leading to insufficient knowledge about malaria transmission and failure to diagnose the disease early. Many village health clinics lacked sufficient supplies of drugs and skilled staff to administer them and monitor their use. The districts of Kulonprogo, Magelang and Purworejo in the Menoreh Hills area on the island of Java were the most affected by the epidemic (53). The Menoreh Hills Malaria Control Project was carried out between May and December 2001, with support from WHO and USAID. Communities were mobilized, local people were trained as malaria workers and community members were educated on how to manage epidemics. Village health workers played an important role in early diagnosis and treatment of the disease among poor rural populations. Health workers also introduced IRS and the new habit of sleeping under ITNs, which were distributed free of charge. Village elders and local teachers were engaged in information campaigns to promote the use of ITNs. In 2001, close to 4500 ITNs were distributed by district administrations and 8000 houses were sprayed. By the end of 2001, the malaria epidemic in the Menoreh Hills had been halted and reversed (Fig. 23). Commitment on the part of the district authorities was crucial for supporting action at community level and for negotiating adequate domestic and external funds. Indonesia’s decentralization programme, initiated in 2001, gave more responsibility and autonomy to the districts. But investment in health—both from domestic and external sources—is low, thus many district governments rely on user fees from public health facilities as a source of local revenue, without exempting even the poor or the most basic services. Figure 23. Malaria cases decrease in the Menoreh Hills, Indonesia 
A crucial factor in controlling the epidemic was establishing monitoring and surveillance systems. Mass blood surveys were carried out in Kulonprogo and Purworejo during September and October of 2001. Mass fever surveys were conducted in all three districts from October 2001 to April 2002, with treatment for those fever cases subsequently found infected on blood slides. District authorities from the sectors of agriculture and public works helped to ensure that the rapid opening of land plantations did not aggravate the spread of malaria, by enforcing good agricultural practices and adherence by farmers to planting schedules. Intervillage cooperation involved notifying residents working in other villages to be careful not to spread malaria. Neighbouring villages were given IRS concurrently to maximize the impact on mosquito populations. |
BOX 10. FOCUSED INDOOR RESIDUAL SPRAYING CONTROLS MALARIA IN SRI LANKA During the 1970s and the 1980s, malaria caused very high morbidity levels and regularly broke out in epidemic form in Sri Lanka. In 1992, the NMCP drastically revised its control strategy, in keeping with the New Global Malaria Control Strategy introduced that year. As during the eradication programme in the 1960s and 1970s, IRS was a major activity of the new control programme. But instead of aiming for universal and frequent IRS coverage, which during the eradication programme had failed to stop transmission and met community resistance in some areas, vector control was targeted to carefully stratified malaria-risk areas. Varying frequencies of IRS were implemented according to malariogenic potential, i.e. year-round, seasonal or exclusively at times of observed transmission. This resulted in better acceptability in the communities and higher cost-effectiveness. To further reduce the number of villages where IRS was needed, the use of larvivorous fish was introduced and, under a project funded by the International Development Association/World Bank between 1997 and 2002, ITNs were provided to villages with a very high risk of malaria. Entomological activities were reoriented with a view to helping predict and prevent epidemics. Furthermore, early detection and prompt treatment through outreach-type Mobile Malaria Clinics was implemented. Chloroquine resistance of falciparum malaria, which was prevalent in some areas and foci, was managed well by temporarily changing to sulfadoxine–pyrimethamine as the first-line drug treatment in these areas. In 2003, recorded malaria incidence fell to the lowest level observed since 1967 (Fig. 24). Another remarkable achievement is that epidemics have been averted since the last epidemic of 1990–1992. Figure 24. Microscopically confirmed malaria cases detected by surveillance in Sri Lanka, 1980–2003  |
• Western Pacific
Malaria control was revitalized in the 1980s in China and in the 1990s in most other Western Pacific countries, following resurgence in the 1980s and early 1990s (Box 11). The resurgence was related to a general economic decline and reduced budget for malaria control, resulting in deterioration of health care in general— such as in Viet Nam—and breakdowns in drug supplies and the arrest of vector control in rural areas—such as in Papua New Guinea. Large-scale population movements and emergence of drug resistance contributed as well. With transmission of vivax malaria reappearing in the Republic of Korea in the 1990s, the region now includes 10 endemic countries.
Parts of Papua New Guinea and Vanuatu (55) continue to suffer from hyperendemic falciparum malaria. As in tropical Africa, the primary risk groups are young children and pregnant women. Elsewhere, forest workers, miners, farmers and migrants of all ages form special risk groups.
National control policies in all countries include vector control with ITNs, targeted IRS and improvement of diagnosis, and prompt and effective treatment. In the mid-1990s, China, Malaysia, the Philippines and Viet Nam replaced DDT and organophosphates with other insecticides. Since 1999, at least 1 million ITNs have been distributed and 6.4 million existing nets have been (re-)treated with insecticide. Cambodia, China and Viet Nam were among the first countries to suffer from highlevel parasite resistance to antimalarial drugs. Multidrug resistance was recorded as early as the 1980s, with the highest prevalence in border areas. These countries now use ACTs for first-line treatment. In Viet Nam, wide availability of artemisinin derivatives and later ACTs for first-line treatment contributed to a low and falling level of mortality caused by malaria since 1995–1996 (Fig. 25) (56). Under RBM, and with support from the GFATM, all countries with falciparum malaria are using rapid diagnostic tests to reduce overusage of costly antimalarials and the risk of development of resistance to the newest drugs. All countries perform drug efficacy monitoring in at least one sentinel site.
After a peak in 1991–1992, the overall case reporting rate across 10 countries fell gradually until 2003 (Fig. 25). In individual countries, year-to-year fluctuations in reported case rates are apparent, which however often reflect changes in the completeness of surveillance or reporting rather than actual epidemiological trends. For example, reporting completeness decreased in Papua New Guinea between 1995 and 1998, but it improved during the early 1990s in Lao People’s Democratic Republic; in the Philippines, a varying intensity of active case detection resulted in variations in case reporting rates. In Papua New Guinea, the Solomon Islands and Vanuatu, programme success fell and morbidity rose again caused by civil unrest and human and financial constraints since 2000 (Fig. 25). However, increased funding including from the GFATM is expected to help reverse this trend.
Challenges for malaria control in the coming decade include: (i) ensuring the quality and effectiveness of available antimalarial drugs in both the public and private sectors; (ii) increasing the coverage of rapid diagnostic tests or microscopic diagnosis; and (iii) access to diagnosis and treatment in remote, high-risk rural areas. In addition, the scaling up of ITN distribution and (re-)treatment of ITNs and the distribution of LLINs require increased efforts.
Figure 25. Standardized rates of reported malaria cases (a) and deaths (b) in malariaendemic countries in the Western Pacific, by calendar year, 1990–2003  
Numerators are based on confirmed autochthonous cases. Country-specific case rates are shown for all countries; country-specific death rates are shown for all countries with a rate of > 0.1 per 100 000 persons in at least one year. Regional averages are weighted by population size (52). |
BOX 11. SUCCESSFUL MALARIA CONTROL IN SABAH, MALAYSIA The Sabah area of Malaysia accounts for approximately 70% of malaria cases in the country. Recorded incidence in this area was very high in the early 1990s. Chloroquine resistance, an insufficient control budget and lack of personnel contributed to the problem. In this forested area, which is climatically highly suitable for malaria transmission and relatively inaccessible to control efforts, aboriginal groups, soldiers, plantation and forest workers, and illegal immigrant populations are especially vulnerable. An intensified malaria control plan was launched in 1996. Districts were stratified into high, moderate and low risk, based on annual recorded malaria incidence rates. With increased budget and staff, ITNs were provided for more than 700 000 people and over 400 additional primary health-care volunteers were trained in diagnosing and treating malaria, and in improving awareness. In addition, IRS was scaled up. By 2003, all high-risk areas were reduced to moderate or low risk, and all moderate-risk areas had regressed to low risk.a The overall recorded annual number of cases fell from 49 863 in 1995 to 1770 in 2003 (Fig. 26). Challenges ahead are to maintain the gains achieved through early recognition and control of epidemics, to prevent drug resistance and to reduce malaria transmission further in the inaccessible, hilly forested areas where transportation facilities are poor. In the longer term, infrastructural and socioeconomic developments ire expected to consolidate the successful containment of malaria. a Local definitions:
Figure 26. Malaria report case rates in Sabah, Malaysia  |
2. Age/sex distribution in reported cases
Few countries record the sex of reported cases. In 7 Asian countries that did, between 52% and 71% of reported cases were male (Fig. 27). The higher incidence in males compared with females in Cambodia, Malaysia and Thailand probably reflects the occupational exposure in parts of these countries, although gender differences in treatment-seeking behaviour might also be a contributing factor.
Reliable data on the age distribution in reported cases were available for 8 countries in South-East Asia. In most of these countries, adults over 15 years of age account for more than half of the total cases. However, the age pattern in reported case rates varied markedly between countries. In Bhutan, Cambodia and Nepal, the case rate increased with age, while in Bangladesh, the Lao People’s Democratic Republic and Sri Lanka, children under 5 years of age had the highest case rate (Fig. 28).
Figure 27. Proportion of cases reported in males in Asia, 2003 
Data are from countries that reported numbers of cases for males and females separately in 2003 and for which the sum of reported cases in males and females was equal to the reported total. |
Figure 28. Age distribution of reported cases in Asian countries, 2003; age distribution of cases (a) and age-specific case rates per 1000 persons per year (b)   Date are from countries that reported numbers of cases by age group in 2003, and for which the sum of age-specific reported numbers of cases was equal to or smaller than the reported total. |
Figure 29. Proportion of children under 5 years of age sleeping under mosquito nets or ITNs based on national surveys in Asian countries, 2000–2002  Median survey year is 2000. |
Figure 30. Household possession of mosquito nets and ITNs in Asian countries  Median survey year is 2001. Results from subnational surveys are included for countries where malaria is focal and where the survey sampled selectively in areas with a relatively high burden of malaria. |
3. Coverage of mosquito nets and insecticide-treated nets
National surveys in 7 Asian countries measured a median net usage rate for children under 5 years of age of 32% (range 6–96%); for ITNs the median child usage rate was 1.9% (range 0–16%) (Fig. 29).
In many countries in Asia, given the relatively moderate transmission intensity, people of all ages are at risk and the proportion of households possessing one or more nets is a more relevant indicator than usage by young children. Surveys in Afghanistan, Cambodia, Timor-Leste and malarious areas of Lao People’s Democratic Republic, Myanmar and Nepal measured household possession levels of between 11% and 97% for any nets, whether or not these had been treated with insecticide. In Afghanistan, 4.8% of households owned an ITN in 2002, and in Lao People’s Democratic Republic 64% of households owned an ITN in 2001. In all surveyed countries, most available nets are not insecticide-treated (Fig. 30).
Equity in net coverage
In the few countries with detailed survey data available, net and ITN coverage was not consistently higher in urban or in rural areas. However, net usage and ITN usage by children were a median of threefold and twofold lower in the poorest households compared with the least poor households (Fig. 31).
Figure 31. Median net and ITN possession (as % of households) or usage (as % of children under 5 years of age) in Asian countries by urban and rural division (a) and for the 20% poorest and 20% least poor households (b), from national surveys conducted between 1999 and 2004 
Sources: urban/rural data: net and ITN usage from seven surveys, net possession from one survey; poorest/least poor households data: net and ITN usage from five surveys, no surveys available on net or ITN possession. Countries surveyed: Azerbaijan, Indonesia, Iraq, Lao People’s Democratic Republic, Tajikistan, Timor-Leste and Viet Nam. |
4. Drug efficacy
Resistance of P. falciparum against most common antimalarial drugs as well as multidrug resistance has been widely prevalent throughout Asia. Failure rates of chloroquine are generally above 40% in the Eastern Mediterranean and Western Pacific, and around 40% in South-East Asia (Fig. 32). For sulfadoxine–pyrimethamine, failure rates remain below 20% in the Eastern Mediterranean, around 20% in South-East Asia and 20–40% in the Western Pacific (Fig. 33). Trends over time are difficult to infer because of the scarcity of studies, and because studies in different sites were conducted in different years. Mefloquine treatment failure has increased to more than 20% in South-East Asia by 2004, and between 10% and 20% in the Western Pacific (Fig. 34).
The description of drug resistance of P. vivax is more recent. In 1989, the first cases of chloroquine-resistant vivax malaria appeared in Papua New Guinea. P. vivax remains generally sensitive to the common antimalarial drugs, but chloroquine and/or pyrimethamine treatment failure has been documented in some focal areas of South-East Asia and Oceania including Irian Jaya and other Indonesian Islands.
Figure 32. Treatment failure of chloroquine to falciparum malaria in Asia by subregion, 1996–2004 
Drug efficacy is expressed as total treatment failure with 28-day follow up (9). BBoxes indicate the 25th and 75th percentile of failure rates observed across available studies, error bars indicate the upper and lower adjacent values and the grey line in each box indicates the median. |
Figure 33. Treatment failure of sulfadoxine–pyrimethamine against falciparum malaria in Asia, by subregion, 1996–2003 
Drug efficacy is expressed as total treatment failure with 28-day follow up (9). Boxes indicate the 25th and 75th percentile of failure rates observed across available studies, error bars indicate the upper and lower adjacent values and the grey line in each box indicates the median. |
Figure 34. Treatment failure of mefloquine against falciparum malaria in South-East Asia, 1996–2003 
Drug efficacy is expressed as total treatment failure with 28-day follow up (9). Boxes indicate the 25th and 75th percentile of failure rates observed across available studies, error bars indicate the upper and lower adjacent values and the grey line in each box indicates the median. |
