MalariaNCT00863408
Estivation of Malaria Vector Mosquitoes in the Sahelian Region of Mali
An observational study of Malaria, run by National Institute of Allergy and Infectious Diseases (NIAID) at 1 site in United States.
Trial summary
Background: P. falciparum, one of the most virulent forms of malaria, causes more than 300 million episodes of malaria and 1 million deaths each year. The spread of drug-resistant parasites, insecticide-resistant mosquitoes, and persistent socioeconomic conditions of poverty compound the difficulties of malaria as a… Read more about this study
- Who is it for?
- Ages 18 to 65 years, men onlyHealthy volunteers can take part
- Conditions the study is for
- Malaria
- How many people
- Not given
- Where
- 1 siteUnited States
- Study dates
- 3 Mar 2009to 10 Mar 2010
- Phase
- Observational
- Are there results?
- None posted in the registry
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 65 years
- Men only
- Healthy volunteers accepted
- Adult, Older adult
Who may be able to join
- Age 18-65 years
- Only healthy male adults who are free of acute and chronic illnesses will participate.
- Permanent residency in Thierola
- Ability to collect mosquitoes after being trained
Who cannot join
None listed.
Trial locations and contacts
1 site in 1 country.
United States1 site
National Institutes of Health Clinical Center, 9000 Rockville Pike
Bethesda, Maryland, 20892
About this study
Official title: Estivation of Malaria Vector Mosquitoes in the Sahelian Region of Mali (Village of Thierola in the District of Banamba)
Background:
- P. falciparum, one of the most virulent forms of malaria, causes more than 300 million episodes of malaria and 1 million deaths each year. The spread of drug-resistant parasites, insecticide-resistant mosquitoes, and persistent socioeconomic conditions of poverty compound the difficulties of malaria as a major global health problem. New means of disease and vector control are vitally needed.
- Several promising strategies rely on targeting mosquito populations when they are most vulnerable, such as during the dry season when mosquitoes find it difficult to reproduce. Large regions of the West African country of Mali have prolonged dry seasons (up to 8 months), during which mosquito populations dramatically decline within a month after the rainfall ceases. Clearly, mosquitoes can survive the dry season (as evident from their robust numbers during the wet season) but the process that enables them to do so remains unknown. Targeting the small and fragile mosquito population at the end of the dry season could reduce or eliminate the numbers of mosquitoes in certain regions, providing great benefits for communities in dry regions.
Read more
Objectives:
- To determine if common malaria-carrying mosquitoes survive the dry season in the Mali village of Thierola by estivation (going dormant, or hibernating, during dry periods).
- To identify and examine mosquitoes that were marked with special paint during a previous protocol, if these marked mosquitoes are captured during the investigation.
Eligibility:
- All activities in this protocol will take place in Thierola village, Banamba district, Koulikoro region, Mall, West Africa. The village was chosen because it is isolated from other communities by at least 6 km and is a small community of less than 300 inhabitants living in 90 houses.
- Participants will be healthy adult men between 18 and 65 years of age.
Design:
- Thirty adult men who live in Thierola will be recruited to participate as mosquito collectors for the human-baited trapping method and will work in teams of two.
- The first collector will expose his lower legs to attract human-seeking mosquitoes. Using a mouth aspirator, the second collector will collect the mosquitoes as they land on the first collector's legs.
- The collections will be conducted both indoors and outdoors from 6 p.m. to 6 a.m. the following morning for 14 consecutive days.
- All study volunteers will be trained in proper collection technique and supervised throughout the study by a mobile team led by the study investigators. Volunteers will be monitored for signs of malaria and treated accordingly if they develop symptoms of the disease.
- Researchers will collect mosquito samples at the end of the dry season (April-May) and at the start of the rainy season (May-June).
- Mosquitoes collected in the study will be analyzed by NIH researchers to learn more about how they survive during the dry season.
Read the detailed description
Malaria causes over one million deaths annually. A promising control strategy relies on targeting mosquito populations when they are vulnerable, such as during the dry season. Prolonged dry season during which larval sites are scarce and mosquito populations decline prevail in the Sahel which covers a large part of Mali. How mosquitoes withstand the dry season remains unknown. Some evidence supports the adult estivation hypothesis whereby mosquitoes remain in protected sites, except for sporadic journeys to obtain blood-meals to sustain themselves rather than to produce eggs. Alternatively, mosquitoes do not survive the dry season locally; rather, they migrate from areas where reproduction continues at permanent water bodies. We aim to determine if An. Gambiae estivate during the dry season in the Sahel; and if so, identify their hidden resting sites. As mosquito populations decline, standard sampling techniques yield zero mosquitoes. Because estivating females take blood meals intermittently, the most promising sampling technique is by human landing catch (HLC). Finding a few mosquitoes during the dry season have been reported, but it could not be determined if they were estivating or were migrants from villages, where larval sites persist. This study can resolve this because we captured marked and released over 5000 mosquitoes just before the dry season (November 2008). We aim to collect mosquitoes during the end of the dry season (April 2009) and the onset of the rainy season (June 2009) and find out if they bear marks from the previous wet season. Finding a single marked specimen will be the ultimate proof for the estivation hypothesis. Experiments will take place in the Sahelian village Thierola, Koulikoro Region, Mali, where the dry season exceeds 7 months. The village was chosen because it has no permanent larval sites and is a small community (< 300 inhabitants) living in 90 houses, allowing collection in all houses in a single day. Thirty adult male residing in Thierola will be recruited as collectors for the HLC. A collector will expose his lower legs to attract mosquitoes. Using a mouth aspirator, mosquitoes will be collected as they land on the collector's legs, ideally, before a blood meal is taken. Collection will be conducted 6pm to 6am for 14 consecutive days in April 2009 and again after the rains begin in June 2009. Collectors will be informed of the proper collecting procedures during the consenting procedure. During the time of year we propose to conduct this work, mosquito populations will be at their minima and any surviving mosquitoes will take blood meals infrequently. Therefore, the HLCs will be conducted when malaria transmission is extremely low and the risk to volunteers essentially nil. In summary, knowledge of how mosquitoes survive the dry season would open novel ways for vector and malaria control.
- Conditions
- Malaria
- Keywords
- Mosquito, Human Landing Collection, Malaria
- Medical subject headings
- Malaria
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted18 Mar 2009 (estimated)
- Study start3 Mar 2009
- Study completion10 Mar 2010
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Publications (3)Papers the sponsor has linked to this study.
- Other trials for MalariaStudies of the same condition, open and under way.
- More trials run by National Institute of Allergy and Infectious Diseases (NIAID)The sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Observational
- Time perspective
- Prospective
Sponsor and investigators
- Sponsor type
- US National Institutes of Health
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT00863408
- Sponsor's protocol ID
- 999909093
- Other IDs
- 09-I-N093
- Status last verified
- 10 Mar 2010
- First submitted
- 17 Mar 2009
- Last updated
- 2 Jul 2017
- Results posted
- No
Publications
Beier JC, Killeen GF, Githure JI. Short report: entomologic inoculation rates and Plasmodium falciparum malaria prevalence in Africa. Am J Trop Med Hyg. 1999 Jul;61(1):109-13. doi: 10.4269/ajtmh.1999.61.109.
PubMed 10432066Hay SI, Rogers DJ, Toomer JF, Snow RW. Annual Plasmodium falciparum entomological inoculation rates (EIR) across Africa: literature survey, Internet access and review. Trans R Soc Trop Med Hyg. 2000 Mar-Apr;94(2):113-27. doi: 10.1016/s0035-9203(00)90246-3.
PubMed 10897348Simard F, Lehmann T, Lemasson JJ, Diatta M, Fontenille D. Persistence of Anopheles arabiensis during the severe dry season conditions in Senegal: an indirect approach using microsatellite loci. Insect Mol Biol. 2000 Oct;9(5):467-79. doi: 10.1046/j.1365-2583.2000.00210.x.
PubMed 11029665
Study at a glance
From the registry record, last updated by the sponsor on 2 Jul 2017. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- Estivation of Malaria Vector Mosquitoes in the Sahelian Region of Mali (Village of Thierola in the District of Banamba)
- ClinicalTrials.gov ID
- NCT00863408
- Acronym / sponsor ID
- 999909093
- Conditions
- Malaria
- Keywords
- Mosquito, Human Landing Collection, Malaria
- Study type
- Observational
- Recruitment status
- Completed
- Lead sponsor
- National Institute of Allergy and Infectious Diseases (NIAID)US National Institutes of Health
- Study start
- 3 Mar 2009
- Study completion
- 10 Mar 2010
- First posted
- 18 Mar 2009 (estimated)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
Background:
- P. falciparum, one of the most virulent forms of malaria, causes more than 300 million episodes of malaria and 1 million deaths each year. The spread of drug-resistant parasites, insecticide-resistant mosquitoes, and persistent socioeconomic conditions of poverty compound the difficulties of malaria as a major global health problem. New means of disease and vector control are vitally needed.
- Several promising strategies rely on targeting mosquito populations when they are most vulnerable, such as during the dry season when mosquitoes find it difficult to reproduce. Large regions of the West African country of Mali have prolonged dry seasons (up to 8 months), during which mosquito populations dramatically decline within a month after the rainfall ceases. Clearly, mosquitoes can survive the dry season (as evident from their robust numbers during the wet season) but the process that enables them to do so remains unknown. Targeting the small and fragile mosquito population at the end of the dry season could reduce or eliminate the numbers of mosquitoes in certain regions, providing great benefits for communities in dry regions.
Objectives:
- To determine if common malaria-carrying mosquitoes survive the dry season in the Mali village of Thierola by estivation (going dormant, or hibernating, during dry periods).
- To identify and examine mosquitoes that were marked with special paint during a previous protocol, if these marked mosquitoes are captured during the investigation.
Eligibility:
- All activities in this protocol will take place in Thierola village, Banamba district, Koulikoro region, Mall, West Africa. The village was chosen because it is isolated from other communities by at least 6 km and is a small community of less than 300 inhabitants living in 90 houses.
- Participants will be healthy adult men between 18 and 65 years of age.
Design:
- Thirty adult men who live in Thierola will be recruited to participate as mosquito collectors for the human-baited trapping method and will work in teams of two.
- The first collector will expose his lower legs to attract human-seeking mosquitoes. Using a mouth aspirator, the second collector will collect the mosquitoes as they land on the first collector's legs.
- The collections will be conducted both indoors and outdoors from 6 p.m. to 6 a.m. the following morning for 14 consecutive days.
- All study volunteers will be trained in proper collection technique and supervised throughout the study by a mobile team led by the study investigators. Volunteers will be monitored for signs of malaria and treated accordingly if they develop symptoms of the disease.
- Researchers will collect mosquito samples at the end of the dry season (April-May) and at the start of the rainy season (May-June).
- Mosquitoes collected in the study will be analyzed by NIH researchers to learn more about how they survive during the dry season.
Detailed description
Malaria causes over one million deaths annually. A promising control strategy relies on targeting mosquito populations when they are vulnerable, such as during the dry season. Prolonged dry season during which larval sites are scarce and mosquito populations decline prevail in the Sahel which covers a large part of Mali. How mosquitoes withstand the dry season remains unknown. Some evidence supports the adult estivation hypothesis whereby mosquitoes remain in protected sites, except for sporadic journeys to obtain blood-meals to sustain themselves rather than to produce eggs. Alternatively, mosquitoes do not survive the dry season locally; rather, they migrate from areas where reproduction continues at permanent water bodies. We aim to determine if An. Gambiae estivate during the dry season in the Sahel; and if so, identify their hidden resting sites. As mosquito populations decline, standard sampling techniques yield zero mosquitoes. Because estivating females take blood meals intermittently, the most promising sampling technique is by human landing catch (HLC). Finding a few mosquitoes during the dry season have been reported, but it could not be determined if they were estivating or were migrants from villages, where larval sites persist. This study can resolve this because we captured marked and released over 5000 mosquitoes just before the dry season (November 2008). We aim to collect mosquitoes during the end of the dry season (April 2009) and the onset of the rainy season (June 2009) and find out if they bear marks from the previous wet season. Finding a single marked specimen will be the ultimate proof for the estivation hypothesis. Experiments will take place in the Sahelian village Thierola, Koulikoro Region, Mali, where the dry season exceeds 7 months. The village was chosen because it has no permanent larval sites and is a small community (< 300 inhabitants) living in 90 houses, allowing collection in all houses in a single day. Thirty adult male residing in Thierola will be recruited as collectors for the HLC. A collector will expose his lower legs to attract mosquitoes. Using a mouth aspirator, mosquitoes will be collected as they land on the collector's legs, ideally, before a blood meal is taken. Collection will be conducted 6pm to 6am for 14 consecutive days in April 2009 and again after the rains begin in June 2009. Collectors will be informed of the proper collecting procedures during the consenting procedure. During the time of year we propose to conduct this work, mosquito populations will be at their minima and any surviving mosquitoes will take blood meals infrequently. Therefore, the HLCs will be conducted when malaria transmission is extremely low and the risk to volunteers essentially nil. In summary, knowledge of how mosquitoes survive the dry season would open novel ways for vector and malaria control.
Study design
- Time perspective
- Prospective
Who may qualify
- Ages
- 18 to 65 years
- Sex
- Male only
- Healthy volunteers
- Accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (4 listed)
- Age 18-65 years
- Only healthy male adults who are free of acute and chronic illnesses will participate.
- Permanent residency in Thierola
- Ability to collect mosquitoes after being trained
Key exclusion criteria (0 listed)
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Primary outcome
Not reported in the source record.
Results and safety
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Jul 2017.
- Background: PubMed 10432066Beier JC, Killeen GF, Githure JI. Short report: entomologic inoculation rates and Plasmodium falciparum malaria prevalence in Africa. Am J Trop Med Hyg. 1999 Jul;61(1):109-13. doi: 10.4269/ajtmh.1999.61.109.
- Background: PubMed 10897348Hay SI, Rogers DJ, Toomer JF, Snow RW. Annual Plasmodium falciparum entomological inoculation rates (EIR) across Africa: literature survey, Internet access and review. Trans R Soc Trop Med Hyg. 2000 Mar-Apr;94(2):113-27. doi: 10.1016/s0035-9203(00)90246-3.
- Background: PubMed 11029665Simard F, Lehmann T, Lemasson JJ, Diatta M, Fontenille D. Persistence of Anopheles arabiensis during the severe dry season conditions in Senegal: an indirect approach using microsatellite loci. Insect Mol Biol. 2000 Oct;9(5):467-79. doi: 10.1046/j.1365-2583.2000.00210.x.
Related trials for Malaria
Active, not recruitingObservational study
Trajectories and Mechanisms of Recovery From Malaria: An Observational Study
Malaria
Not yet recruiting
Positron Emission Tomography and Organ-Specific Changes in Participants Co-Enrolled in NIH Studies of Plasmodium Vivax Controlled Human Malaria Infection
Healthy Volunteer, Malaria
Recruiting
The Effects of Iron Treatment on Vaccine Immunogenicity in Kenyan Infants With Iron Deficiency
Iron Deficiencies
RecruitingObservational study
Host and Parasite Factors That Influence Susceptibility to Malaria Infection and Disease During Pregnancy and Early Childhood in Ouelessebougou and Bamako, Mali
Malaria
RecruitingPhase 1
Safety, Tolerability and Efficacy of PfSPZ-LARC2 Vaccine Against CHMI in Malaria-Naïve Adults
Malaria Falciparum
Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part. This study is not recruiting at the moment.
The record lists no contact. Use the official record to reach the sponsor.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
An observational study of Malaria, run by National Institute of Allergy and Infectious Diseases (NIAID) at 1 site in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 4 inclusion and 0 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: finished, as of the sponsor's last update on 2 Jul 2017. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
Are results available for this study?
The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.
How can a doctor refer a patient or contact the research team?
The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.
Where can I read the original study information?
On the ClinicalTrials.gov record for NCT00863408, which also lists 3 linked publications.
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Jul 2017.