Ability of near-infrared spectroscopy and chemometrics to predict the age of mosquitoes reared under different conditions

Abstract

Background: Practical, field-ready age-grading tools for mosquito vectors of disease are urgently needed because of the impact that daily survival has on vectorial capacity. Previous studies have shown that near-infrared spectroscopy (NIRS), in combination with chemometrics and predictive modeling, can forecast the age of laboratory-reared mosquitoes with moderate to high accuracy. It remains unclear whether the technique has utility for identifying shifts in the age structure of wild-caught mosquitoes. Here we investigate whether models derived from the laboratory strain of mosquitoes can be used to predict the age of mosquitoes grown from pupae collected in the field. Methods: NIRS data from adult female Aedes albopictus mosquitoes reared in the laboratory (2, 5, 8, 12 and 15 daysold) were analysed against spectra from mosquitoes emerging from wild-caught pupae (1, 7 and 14 days-old). Different partial least squares (PLS) regression methods trained on spectra from laboratory mosquitoes were evaluated on their ability to predict the age of mosquitoes from more natural environments. Results: Models trained on spectra from laboratory-reared material were able to predict the age of other laboratoryreared mosquitoes with moderate accuracy and successfully differentiated all day 2 and 15 mosquitoes. Models derived with laboratory mosquitoes could not differentiate between field-derived age groups, with age predictions relatively indistinguishable for day 1-14. Pre-processing of spectral data and improving the PLS regression framework to avoid overfitting can increase accuracy, but predictions of mosquitoes reared in different environments remained poor. Principal components analysis confirms substantial spectral variations between laboratory and field-derived mosquitoes despite both originating from the same island population. Conclusions: Models trained on laboratory mosquitoes were able to predict ages of laboratory mosquitoes with good sensitivity and specificity though they were unable to predict age of field-derived mosquitoes. This study suggests that laboratory-reared mosquitoes do not capture enough environmental variation to accurately predict the age of the same species reared under different conditions. Further research is needed to explore alternative pre-processing methods and machine learning techniques, and to understand factors that affect absorbance in mosquitoes before field application using NIRS.

The application of spectroscopy techniques for diagnosis of malaria parasites and arboviruses and surveillance of mosquito vectors: A systematic review and critical appraisal of evidence

“…However, when NIRS was used to predict Ae. albopictus mosquitoes reared from wild pupae using a model developed from laboratory-reared mosquitoes, young and old mosquitoes could not be differentiated [83]. Based on the authors' description of their experimental design, the inability to predict the age of mosquitoes collected from wild pupae is most likely due to a weak predictive model that failed to capture the heterogeneity of the wild population including variation in the larval diet.…”

“…Based on the authors' description of their experimental design, the inability to predict the age of mosquitoes collected from wild pupae is most likely due to a weak predictive model that failed to capture the heterogeneity of the wild population including variation in the larval diet. Alternatively, the small sample size used for model development was not robust [83]. A previous study indicated that Anopheles mosquitoes reared from wild pupae could be predicted accurately if models were developed from a similar mosquito population and neither species type nor exposure to pyrethroids affected the ability of NIRS to predict their age [76].…”

Highly Efficient Use of Infrared Spectroscopy (ATR-FTIR) to Identify Aphid Species

“…The premise that every species has a unique chemical composition allows the advantageous use of FTIR spectroscopy for taxonomic purposes. Near-infrared spectroscopy (NIRS) was used to quickly identify the age of the Aedes albopictus mosquito population in order to avoid a potential epidemic of, e.g., diseases such as dengue and Zika [ 1 ]. An attenuated total reflection–Fourier-transform infrared (ATR-FTIR) spectrometer for acquiring high-resolution mid-infrared (MIR) spectra (4000 cm −1 to 400 cm −1 ) was used to discriminate blood samples originating from a common vertebrate host, collected from the malaria vector, Anopheles arabiensis , and this method avoided the required molecular techniques [ 2 , 3 ].…”

Adapting field-mosquito collection techniques in a perspective of near-infrared spectroscopy implementation

“…Near-infrared spectroscopy (NIRS) is a rapid, high-throughput and relatively inexpensive technique that has been used for a decade to predict the species, age and infection status of certain disease vectors, such as Anopheles and Aedes mosquitoes [ 3 – 5 ]. Many of these different studies used laboratory or field mosquitoes to assess the accuracy of NIRS to differentiate between Anopheles species [ 3 , 4 ], mosquito age [ 3 , 6 ] and Anopheles infection status using Plasmodium culture [ 7 , 8 ].…”

“…Many of these different studies used laboratory or field mosquitoes to assess the accuracy of NIRS to differentiate between Anopheles species [ 3 , 4 ], mosquito age [ 3 , 6 ] and Anopheles infection status using Plasmodium culture [ 7 , 8 ]. The reliability of the method for application in entomological surveillance studies using wild mosquitoes is less clear, with models trained on laboratory-reared mosquitoes being unable to accurately predict the infection status or age of field mosquitoes [ 5 , 9 ]. Further work is therefore required to verify these results, and it may be necessary to calibrate NIRS models with greater numbers of wild-caught mosquitoes.…”