Trial Outcomes & Findings for Clinical Investigation Study to Evaluate the Consistency and Reproducibility of Two Consecutive Mosquito Feeding Assays (NCT NCT04666350)
NCT ID: NCT04666350
Last Updated: 2024-04-29
Results Overview
Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst prevalence is defined as the percentage of mosquitoes in a cup with at least one oocyst detected in the mid-gut among the surviving mosquitoes (in the same cup) that underwent the feeding assays.
COMPLETED
42 participants
Feeding assays were performed on Day 1 and Day 2; Oocyst prevalence in surviving mosquitoes was assessed 9 days after feeding (Days 9 and 10).
2024-04-29
Participant Flow
Healthy adults with no malaria symptoms were recruited from the villages in the Kombewa Health and Demographics Surveillance System (HDSS) consisting of half of Kisumu West and all of Seme Sub-Counties of Kisumu County in Kenya.
Four hundred participants consented and underwent screening. After informed consent was obtained participants were tested for the presence of mature stage malarial parasites (called gametocytes) in their blood. Forty-two participants met the inclusion criteria and were gametocyte positive and agreed to participate in the mosquito feeding assays.
Participant milestones
| Measure |
Study Volunteers
Participants provided a blood sample on Day 1 for Direct Membrane Feeding Assay (DMFA) testing prior to participating in the Direct Skin Feeding Assay (DSFA). On Day 2 participants underwent the second DMFA and DSFA assay (within 24 hours of the first assays).
Upon completion of Day 2 DSFA participants received one dose of primaquine and Coartem for 3 days.
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Overall Study
STARTED
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42
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Overall Study
COMPLETED
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42
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Overall Study
NOT COMPLETED
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0
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Reasons for withdrawal
Withdrawal data not reported
Baseline Characteristics
Race and Ethnicity were not collected from any participant.
Baseline characteristics by cohort
| Measure |
Study Volunteers
n=42 Participants
Participants provided a blood sample on Day 1 for Direct Membrane Feeding Assay (DMFA) testing prior to participating in the Direct Skin Feeding Assay (DSFA). On Day 2 participants underwent the second DMFA and DSFA assay (within 24 hours of the first assays).
Upon completion of Day 2 DSFA participants received one dose of primaquine and Coartem for 3 days.
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Age, Continuous
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33.4 years
STANDARD_DEVIATION 9.3 • n=42 Participants
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Sex: Female, Male
Female
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22 Participants
n=42 Participants
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Sex: Female, Male
Male
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20 Participants
n=42 Participants
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Region of Enrollment
Kenya
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42 participants
n=42 Participants
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Ever had malaria?
Yes
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42 Participants
n=42 Participants
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Ever had malaria?
No
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0 Participants
n=42 Participants
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PRIMARY outcome
Timeframe: Feeding assays were performed on Day 1 and Day 2; Oocyst prevalence in surviving mosquitoes was assessed 9 days after feeding (Days 9 and 10).Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis. The number of mosquitoes analyzed reflects the number of surviving mosquitoes after 9 days for each feeding assay and time point.
Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst prevalence is defined as the percentage of mosquitoes in a cup with at least one oocyst detected in the mid-gut among the surviving mosquitoes (in the same cup) that underwent the feeding assays.
Outcome measures
| Measure |
Direct Skin Feeding Assay
n=495 Mosquitoes
Each participant underwent a direct skin feeding assay on Day 1 and Day 2.
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Direct Membrane Feeding Assay
n=543 Mosquitoes
Blood samples from each participant were used in a direct membrane feeding assay.
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Oocyst Prevalence
Day 1 Feeding Assay
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5.2 percentage of mosquitoes
Standard Deviation 7.8
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6.3 percentage of mosquitoes
Standard Deviation 16.2
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Oocyst Prevalence
Day 2 Feeding Assay
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2.3 percentage of mosquitoes
Standard Deviation 4.9
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2.2 percentage of mosquitoes
Standard Deviation 4.4
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SECONDARY outcome
Timeframe: Feeding assays were performed on Day 1 and Day 2; Oocyst density in surviving mosquitos was assessed 9 days after feeding (Days 9 and 10).Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis. The number of mosquitoes analyzed reflects the number of surviving mosquitos after 9 days for each feeding assay and time point.
Participants underwent feeding assays on two days, 24 hours apart (Day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 9 days to allow oocyst development. An oocyst is a structure that develops on the outer wall of the infected mosquito's stomach that contains developing sporozoites. Nine days after feeding mosquito midguts were dissected, stained with 1% mercurochrome and examined by optical microscopy. The number of oocysts in each midgut were recorded. Oocyst density is defined as the mean number of oocysts detected in infected mosquitoes that underwent feeding assays on the same participant.
Outcome measures
| Measure |
Direct Skin Feeding Assay
n=495 Mosquitoes
Each participant underwent a direct skin feeding assay on Day 1 and Day 2.
|
Direct Membrane Feeding Assay
n=543 Mosquitoes
Blood samples from each participant were used in a direct membrane feeding assay.
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|---|---|---|
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Oocyst Density
Day 1 Feeding Assay
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1.1 oocysts / mosquito
Standard Deviation 1.8
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1.6 oocysts / mosquito
Standard Deviation 4.1
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Oocyst Density
Day 2 Feeding Assay
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0.4 oocysts / mosquito
Standard Deviation 0.8
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0.4 oocysts / mosquito
Standard Deviation 0.8
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SECONDARY outcome
Timeframe: Feeding assays were performed on Day 1 and Day 2; Sporozoite prevalence in surviving mosquitoes was assessed 14 days after feeding (Days 14 and 15).Population: Participants with available data; one participant did not have surviving mosquitoes in any of the assays and is not included in the analysis. The number of mosquitoes analyzed reflects the number of surviving mosquitos after 14 days for each feeding assay and time point.
Participants underwent feeding assays on two days, 24 hours apart (day 1 and Day 2). After feeding, mosquitoes were maintained in locked environmental chambers for 14 days to allow sporozoite development. Sporozoites are the forms of the plasmodium that are liberated from the oocysts in the mosquito, accumulate in the salivary glands of the mosquito, and are transferred to humans when the mosquito feeds. Fourteen days after feeding, salivary glands were dissected from live mosquitoes submerged in phosphate-buffered saline (PBS) in order to visualize motile sporozoites by microscopy. Sporozoite prevalence was recorded. Sporozoite prevalence is defined as the percentage of mosquitoes in a cup with at least one sporozoite detected in the salivary glands among the mosquitoes (in the same cup) that underwent feeding assays.
Outcome measures
| Measure |
Direct Skin Feeding Assay
n=342 Mosquitoes
Each participant underwent a direct skin feeding assay on Day 1 and Day 2.
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Direct Membrane Feeding Assay
n=383 Mosquitoes
Blood samples from each participant were used in a direct membrane feeding assay.
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|---|---|---|
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Sporozoite Prevalence
Day 1 Feeding Assay
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5.1 percentage of mosquitoes
Standard Deviation 8.4
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4.5 percentage of mosquitoes
Standard Deviation 8.0
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Sporozoite Prevalence
Day 2 Feeding Assay
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1.8 percentage of mosquitoes
Standard Deviation 4.8
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2.0 percentage of mosquitoes
Standard Deviation 5.7
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SECONDARY outcome
Timeframe: Day 1 and Day 2Population: The analysis of sporozoite density could not be conducted due to technical limitations.
Sporozoite density is defined as the mean number of sporozoites detected in infected mosquitoes that underwent feeding assays. Due to limitation on the state of the art, it was not possible to estimate the sporozoite density using the Optical Microscopy technique.
Outcome measures
Outcome data not reported
Adverse Events
Study Volunteers
Serious adverse events
Adverse event data not reported
Other adverse events
| Measure |
Study Volunteers
n=42 participants at risk
Participants provided a blood sample on Day 1 for Direct Membrane Feeding Assay (DMFA) testing prior to participating in the Direct Skin Feeding Assay (DSFA). On Day 2 participants underwent the second DMFA and DSFA assay (within 24 hours of the first assays).
Upon completion of Day 2 DSFA participants received one dose of primaquine and Coartem for 3 days, except for two women who had a positive pregnancy test at Day 2 and did not receive primaquine.
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Gastrointestinal disorders
Abdominal pain upper
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2.4%
1/42 • 2 days
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Infections and infestations
Tonsillitis
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2.4%
1/42 • 2 days
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Injury, poisoning and procedural complications
Arthropod bite
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2.4%
1/42 • 2 days
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Skin and subcutaneous tissue disorders
Pruritus
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61.9%
26/42 • 2 days
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Skin and subcutaneous tissue disorders
Urticaria
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11.9%
5/42 • 2 days
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Additional Information
Results disclosure agreements
- Principal investigator is a sponsor employee
- Publication restrictions are in place