The Centres for Disease Control light trap (CDC-LT) and the human decoy trap (HDT) compared to the human landing catch (HLC) for measuring <i>Anopheles</i> biting in rural Tanzania

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Abstract

Background

Vector mosquito biting intensity is an important measure to understand malaria transmission. Human landing catch (HLC) is an effective but labour-intensive, expensive, and potentially hazardous entomological surveillance tool. The Centres for Disease Control light trap (CDC-LT) and the human decoy trap (HDT) are exposure-free alternatives. This study compared the CDC-LT and HDT against HLC for measuring Anop heles biting in rural Tanzania and assessed their suitability as HLC proxies.

Methods

Indoor mosquito surveys using HLC and CDC-LT and outdoor surveys using HLC and HDT were conducted in 2017 and in 2019 in Ulanga, Tanzania in 19 villages, with one trap/house/night. Species composition, sporozoite rates and density/trap/night were compared. Aggregating the data by village and month, the Bland–Altman approach was used to assess agreement between trap types.

Results

Overall, 66,807 Anopheles funestus and 14,606 Anopheles arabiensis adult females were caught with 6,013 CDC-LT, 339 indoor-HLC, 136 HDT and 195 outdoor-HLC collections. Indoors, CDC-LT caught fewer An. arabiensis (Adjusted rate ratio [Adj.RR] = 0.35, 95% confidence interval [CI]: 0.27–0.46, p < 0.001) and An. funestus (Adj.RR = 0.63, 95%CI: 0.51–0.79, p < 0.001) than HLC per trap/night . Outdoors, HDT caught fewer An. arabiensis (Adj.RR = 0.04, 95%CI: 0.01–0.14, p < 0.001) and An. funestus (Adj.RR = 0.10, 95%CI: 0.07–0.15, p < 0.001) than HLC. The bias and variability in number of mosquitoes caught by the different traps were dependent on mosquito densities. The relative efficacies of both CDC-LT and HDT in comparison to HLC declined with increased mosquito abundance. The variability in the ratios was substantial for low HLC counts and decreased as mosquito abundance increased. The numbers of sporozoite positive mosquitoes were low for all traps.

Conclusions

CDC-LT can be suitable for comparing mosquito populations between study arms or over time if accuracy in the absolute biting rate, compared to HLC, is not required. CDC-LT is useful for estimating sporozoite rates because large numbers of traps can be deployed to collect adequate mosquito samples. The present design of the HDT is not amenable for use in large-scale entomological surveys. Use of HLC remains important for estimating human exposure to mosquitoes as part of estimating the entomological inoculation rate (EIR).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04192-9.

Related collections

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Author and article information

Contributors

Isaac Haggai Namango:

ORCID: http://orcid.org/0000-0002-7869-1222

isaac.namango@swisstph.ch

Journal

Journal ID (nlm-ta): Malar J

Journal ID (iso-abbrev): Malar J

Title: Malaria Journal

Publisher: BioMed Central (London )

ISSN (Electronic): 1475-2875

Publication date (Electronic): 11 June 2022

Publication date PMC-release: 11 June 2022

Publication date Collection: 2022

Volume: 21

Electronic Location Identifier: 181

Affiliations

[1 ]GRID grid.416786.a, ISNI 0000 0004 0587 0574, Swiss Tropical and Public Health Institute, ; Allschwil, Switzerland

[2 ]GRID grid.6612.3, ISNI 0000 0004 1937 0642, University of Basel, ; Basel, Switzerland

[3 ]GRID grid.414543.3, ISNI 0000 0000 9144 642X, Vector Control Product Testing Unit, , Ifakara Health Institute, ; Bagamoyo, Tanzania

[4 ]GRID grid.416553.0, ISNI 0000 0000 8589 2327, British Columbia Centre for Excellence in HIV/AIDS, ; Vancouver, British Columbia Canada

[5 ]GRID grid.414659.b, ISNI 0000 0000 8828 1230, Telethon Kids Institute, ; Perth, Australia

[6 ]GRID grid.240324.3, ISNI 0000 0001 2109 4251, New York University Grossman School of Medicine, ; New York, NY USA

[7 ]GRID grid.8991.9, ISNI 0000 0004 0425 469X, London School of Hygiene and Tropical Medicine, ; London, UK

[8 ]Innovative Vector Control Consortium, Dar es Salaam, Tanzania

[9 ]GRID grid.451346.1, ISNI 0000 0004 0468 1595, Nelson Mandela African Institute of Science and Technology, ; Arusha, Tanzania

Author information

Isaac Haggai Namango http://orcid.org/0000-0002-7869-1222

Article

Publisher ID: 4192

DOI: 10.1186/s12936-022-04192-9

PMC ID: 9188237

PubMed ID: 35690745

SO-VID: 9240f3cb-28b5-48fa-8756-4743dbd5d6c7

License:

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