Active Case Detection for Malaria Elimination
Active Case Detection for Malaria Elimination
Survey results indicate that systems and procedures for case investigation and RACD are widely in place in the malaria elimination programmes of the APMEN partner countries. Thirteen out of the 14 partner countries responded to the survey and all of the respondent countries carried out case investigation, while 12 reported using RACD. Across respondents, the strategies employed varied, especially in regard to RACD, with different people screened (symptomatic versus asymptomatic) and the number of people screened (household only versus the whole village or a 2.5 km radius). Which of these RACD approaches is effective at preventing and reducing transmission is not known. Better understanding of which strategy is most effective is critical as they are human resource intensive.
Index case investigation practices varied, including the proportion of cases for which case investigation occurred. Most respondents (seven) reported following WHO guidelines to conduct case investigation within one to two days of a case being detected. Many countries also reported collecting broad demographic data during case investigation, most of which are recommended by the WHO, such as: current address, length of time at that address, occupation and place of work, recent travel history, and recent contact with known malaria cases. Although most respondents reported following case investigation data collection guidelines, there is an array of parameters that each programme chooses to assess, and likely reflect tailoring of investigations to local conditions and programme capacity. In some countries, supervision and management of case investigation occurs regularly, also likely related to programme capacity.
How programmes determine the origin of a case also differed across the respondent countries. Although "imported" cases are typically defined as a case originating in another endemic country, several respondents – including those with sub-national elimination strategies as those with national elimination strategies – reported defining cases as imported if they originate from another endemic district or province within the country itself. Programmes seem to prioritize local context when defining importation.
RACD in Asia Pacific countries involves screening households within a specified area, typically a pre-determined radius, around a locally acquired case with the goal of identifying other infections that might be symptomatic or asymptomatic. This process is similar to that found in other countries. However, there is diversity in the strategies and activities used for RACD. Survey results from the Asia Pacific countries show that RACD can be triggered with one case or a defined threshold of multiple index cases, depending on local incidence and malaria control programme resources. Several countries reported screening symptomatic members of the index case household, while others screen all residents of the household. Recent evidence regarding the importance and frequency of asymptomatic infection in low transmission settings suggests that screening symptomatic people alone will not effectively and rapidly reduce malaria transmission. More evidence on the degree of clustering in the settings of APMEN partner countries is needed to support decision-making on how far to screen around an index household. Some countries reported screening all households within a specific administrative unit (e g, village) or a certain radius around the index case, a maximum of 2.5 km. The decision on how wide to screen is based on the theoretical dispersal of vectors and the operational capacity of the programme. However, it should be noted that it is operationally challenging to screen large numbers of households, as the radius around the index household increases the area to be covered increases by the square of the radius.
Most programmes collect a range of information from those screened, including information on residence, occupation, travel history, contact with travellers or immigrants, and other details. Different diagnostic methods (clinical diagnosis, microscopy, RDT, PCR, serology) are used to screen during RACD. There are particular challenges in diagnosing cases in areas with a high proportion of sub-patent or sub-microscopic cases. Several countries are now using PCR confirmation in addition to other diagnostic methods, however, it is not known how routinely it is used in these countries and little evidence exists regarding which diagnostic methods are most effective in the setting of the Asia Pacific. The response to a case or an outbreak should be well coordinated and include vector control and public health messaging components. This was reflected in the survey, as many countries include additional vector control, entomological surveillance and/or health education activities. Although the results of this study show widespread use of RACD, there is a dearth of evidence to guide countries on the effectiveness of these activities.
The variation in case investigation and RACD practices across Asia Pacific countries illustrates the need for further research and informed guidance. In particular, the variation in triggers used for RACD and disparate target areas for screening - either the number of households or a radius - indicate that there remain gaps in knowledge to support optimal identification of malaria infections in the community and to identify the most effective and efficient way to capture them. A starting point to address these gaps would be the collection of standard data on both case investigation and RACD activities. Important metrics to assess are case investigation and RACD coverage rates, number of people screened and completeness of geographical coverage during RACD as well as timeliness of these activities. The survey showed that many programmes do not systematically collect robust data on these activities. Thus there is a need to establish these standardized metrics to monitor and evaluate programme effectiveness. The actual choice of metrics should be established through country programme and stakeholder consultation and integrated into routine surveillance data collection, taking into account the varying contexts in which programmes operate, namely funding constraints, epidemiology, geography and others.
Respondents provided information on the type and scale of activities and data collected, based on their programme strategies and policies. It is likely that many strategies as described are likely not undertaken routinely, as their execution depends on availability of funding, human resources and other constraints. However, an assessment of whether the description in the survey results matches the on the ground reality was not within the scope of this survey, and would best be measured through an observational approach. Gathering more detailed information on why countries selected a particular approach or strategy likewise was not within the scope of the survey, although it is assumed that most base their strategies on WHO surveillance guidelines.
The countries with sub-national elimination strategies – Solomon Islands and Vanuatu – reported solely on the surveillance strategies and activities undertaken in the elimination provinces. The survey did not attempt to collect information on the activities in the control provinces thus a comparison of the two is not possible.
Discussion
Survey results indicate that systems and procedures for case investigation and RACD are widely in place in the malaria elimination programmes of the APMEN partner countries. Thirteen out of the 14 partner countries responded to the survey and all of the respondent countries carried out case investigation, while 12 reported using RACD. Across respondents, the strategies employed varied, especially in regard to RACD, with different people screened (symptomatic versus asymptomatic) and the number of people screened (household only versus the whole village or a 2.5 km radius). Which of these RACD approaches is effective at preventing and reducing transmission is not known. Better understanding of which strategy is most effective is critical as they are human resource intensive.
Index case investigation practices varied, including the proportion of cases for which case investigation occurred. Most respondents (seven) reported following WHO guidelines to conduct case investigation within one to two days of a case being detected. Many countries also reported collecting broad demographic data during case investigation, most of which are recommended by the WHO, such as: current address, length of time at that address, occupation and place of work, recent travel history, and recent contact with known malaria cases. Although most respondents reported following case investigation data collection guidelines, there is an array of parameters that each programme chooses to assess, and likely reflect tailoring of investigations to local conditions and programme capacity. In some countries, supervision and management of case investigation occurs regularly, also likely related to programme capacity.
How programmes determine the origin of a case also differed across the respondent countries. Although "imported" cases are typically defined as a case originating in another endemic country, several respondents – including those with sub-national elimination strategies as those with national elimination strategies – reported defining cases as imported if they originate from another endemic district or province within the country itself. Programmes seem to prioritize local context when defining importation.
RACD in Asia Pacific countries involves screening households within a specified area, typically a pre-determined radius, around a locally acquired case with the goal of identifying other infections that might be symptomatic or asymptomatic. This process is similar to that found in other countries. However, there is diversity in the strategies and activities used for RACD. Survey results from the Asia Pacific countries show that RACD can be triggered with one case or a defined threshold of multiple index cases, depending on local incidence and malaria control programme resources. Several countries reported screening symptomatic members of the index case household, while others screen all residents of the household. Recent evidence regarding the importance and frequency of asymptomatic infection in low transmission settings suggests that screening symptomatic people alone will not effectively and rapidly reduce malaria transmission. More evidence on the degree of clustering in the settings of APMEN partner countries is needed to support decision-making on how far to screen around an index household. Some countries reported screening all households within a specific administrative unit (e g, village) or a certain radius around the index case, a maximum of 2.5 km. The decision on how wide to screen is based on the theoretical dispersal of vectors and the operational capacity of the programme. However, it should be noted that it is operationally challenging to screen large numbers of households, as the radius around the index household increases the area to be covered increases by the square of the radius.
Most programmes collect a range of information from those screened, including information on residence, occupation, travel history, contact with travellers or immigrants, and other details. Different diagnostic methods (clinical diagnosis, microscopy, RDT, PCR, serology) are used to screen during RACD. There are particular challenges in diagnosing cases in areas with a high proportion of sub-patent or sub-microscopic cases. Several countries are now using PCR confirmation in addition to other diagnostic methods, however, it is not known how routinely it is used in these countries and little evidence exists regarding which diagnostic methods are most effective in the setting of the Asia Pacific. The response to a case or an outbreak should be well coordinated and include vector control and public health messaging components. This was reflected in the survey, as many countries include additional vector control, entomological surveillance and/or health education activities. Although the results of this study show widespread use of RACD, there is a dearth of evidence to guide countries on the effectiveness of these activities.
The variation in case investigation and RACD practices across Asia Pacific countries illustrates the need for further research and informed guidance. In particular, the variation in triggers used for RACD and disparate target areas for screening - either the number of households or a radius - indicate that there remain gaps in knowledge to support optimal identification of malaria infections in the community and to identify the most effective and efficient way to capture them. A starting point to address these gaps would be the collection of standard data on both case investigation and RACD activities. Important metrics to assess are case investigation and RACD coverage rates, number of people screened and completeness of geographical coverage during RACD as well as timeliness of these activities. The survey showed that many programmes do not systematically collect robust data on these activities. Thus there is a need to establish these standardized metrics to monitor and evaluate programme effectiveness. The actual choice of metrics should be established through country programme and stakeholder consultation and integrated into routine surveillance data collection, taking into account the varying contexts in which programmes operate, namely funding constraints, epidemiology, geography and others.
Limitations
Respondents provided information on the type and scale of activities and data collected, based on their programme strategies and policies. It is likely that many strategies as described are likely not undertaken routinely, as their execution depends on availability of funding, human resources and other constraints. However, an assessment of whether the description in the survey results matches the on the ground reality was not within the scope of this survey, and would best be measured through an observational approach. Gathering more detailed information on why countries selected a particular approach or strategy likewise was not within the scope of the survey, although it is assumed that most base their strategies on WHO surveillance guidelines.
The countries with sub-national elimination strategies – Solomon Islands and Vanuatu – reported solely on the surveillance strategies and activities undertaken in the elimination provinces. The survey did not attempt to collect information on the activities in the control provinces thus a comparison of the two is not possible.
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