Life Table Approach Research Articles

Economic impact of screening on postdiagnosis work productivity in Japanese women with breast cancer: a life-table modeling approach.

In Japan, biennial mammography screening has been recommended for the early detection of breast cancer (BC) in women aged 40years or above since 2004 by the Ministry of Health, Labor and Welfare. The purpose of this study is to estimate the economic impact of BC screening on work productivity, using a new measure called the productivity-adjusted life-year (PALY). We used a dynamic life table modeling approach to estimate the work productivity of female patients aged 40-64years diagnosed with BC in 2019 over the year of diagnosis and the subsequent 5years. Changes in life-years, PALYs, and gross domestic product (GDP) were assessed by changing the screening detection rate from the current (34.2%) to an ideal (100%) percentage. Each input for modeling was obtained from the most recent public database available. BC patients were estimated to lose 1903 in life-years, 3596 in PALYs, and US$281 million in GDP at the current screening detection rate compared with the ideal detection rate. On the other hand, the following gains are expected when the current screening detection rate was increased to 40-80%; life-years gain; 168-1325, PALYs gain; 317-2503, GDP gain: US$25-196 million. This study has used modeling to show that detecting BC without screening is associated with a lower work productivity and an economic and life-years loss. Encouraging BC screening may be beneficial to maintaining work productivity after diagnosis.

Antibiosis in small grain cereals against the rose-grain aphid, Metopolophium dirhodum (Hemiptera: Aphididae)

Resistance against aphids is an integrated pest management tactic that enhances the economic and environmental sustainability of cereal production. The aim of our study was to assess the degree of antibiosis against Metopolophium dirhodum (Walker) (Hemiptera: Aphididae), one of the most important cereal aphids in temperate regions, in two lines of small grain cereals bred in the Crop Research Institute (CRI) of Prague: spring wheat, Triticum aestivum L. cv. ‘Rufia’, and germplasm of durum wheat, Triticum turgidum ssp. durum (Desf.) van Slageren ‘TTD40363’, under controlled laboratory conditions. Resistant spring wheat cultivar (‘Libertina’) and highly susceptible spring barley (Hordeum vulgare L. cv. ‘Sebastian’) were used for reference. The responses of M. dirhodum to each line and population growth projections were determined according to the age-stage, two-sex life table theory. We found that Rufia was susceptible and TTD40363 was rather resistant to M. dirhodum. The projected population sizes after 35 days were ~ 41,000 individuals in spring wheat Rufia and ~ 12,000 in durum wheat TTD40363, which is within the range delimited by the reference cultivars (4,000 in the highly resistant spring wheat Libertina and 77,500 in highly susceptible spring barley Sebastian). This study provides new data on small grain cereal resistance to aphids. An age-stage, two-sex life table approach was used to assess resistance to aphids on durum wheat and barley for the first time.

Field-evolved resistance to nitenpyram is associated with fitness costs in whitefly.

Elucidating fitness cost associated with field-evolved insect resistance to insecticide is of particular importance to current sustainable pest control. The global pest whitefly Bemisia tabaci has developed resistance to many members of neonicotinoids, but little is known about whitefly resistance to neonicotinoid nitenpyram and its associated fitness cost. Using insecticide bioassay and life-table approach, this study aims to investigate nitenpyram resistance status in field-collected whitefly populations, and to explore whether such resistance is accompanied by a fitness cost. The bioassay results revealed that 14 of 29 whitefly populations displayed moderate to extremely high resistance to nitenpyram, demonstrating a widespread field-evolved resistance to nitenpyram. This field-evolved resistance in the whitefly has increased gradually over the past 3 years from 2021 to 2023. Further life-table study showed that two resistant whitefly populations exhibited longer developmental time, shorter lifespans of adult, and lower fecundity compared with the most susceptible population. The relative fitness cost of the two resistant populations was calculated as 0.69 and 0.56 by using net productive rate R0, which suggests that nitenpyram resistance comes with fitness cost in the whitefly, especially on reproduction. Overall, these results represent field-evolved high resistance to nitenpyram in the whitefly. The existing fitness costs associated with nitenpyram resistance are helpful to propose a suitable strategy for sustainable control of whiteflies by rotation or mixture of insecticide with different modes of action. © 2024 Society of Chemical Industry.

Effects of miR-306 Perturbation on Life Parameters in the English Grain Aphid, Sitobion avenae (Homoptera: Aphididae).

MicroRNAs (miRNA) play a vital role in insects' growth and development and have significant potential value in pest control. Previously, we identified miR-306 from small RNA libraries within the English grain aphid, Sitobion avenae, a devasting insect pest for wheat. miR-306 not only involves in wing morphogenesis, but also is critically important for aphid survival. Its specific impacts on the life history traits, however, remain unclear. Here, we evaluate the impact of miR-306 perturbation on S. avenae populations using a two-sex life table approach. This comprehensive analysis revealed that miR-306 perturbation significantly prolongs the developmental stages (9.64% and 8.20%) and adult longevity of S. avenae, while decreasing pre-adult survival rate (41.45% and 38.74%) and slightly reducing average fecundity (5.80% and 13.05%). Overall, miR-306 perturbation negatively affects the life table parameters of the aphid population. The population prediction models show a significant decline in the aphid population 60 days post interference, compared to the control groups (98.14% and 97.76%). Our findings highlight the detrimental effects of miR-306 perturbation on S. avenae population growth and suggest potential candidate genes for the development of RNAi-based biopesticides targeted specifically at this pest species.

Regional Variation in Lifetime Probability of Admission to Residential Aged Care in Australia.

This paper aims to apply a novel demographic technique to update - and extend to sub-national regions - estimates of the lifetime probability of admission to residential aged care. Making optimal use of Australian data sources on aged care usage, mortality and population, this study adopts a two-population life table approach to produce an updated set of national probability estimates and first-time regional estimates. The probability of admission generally increases with age: nationally, lifetime probability at age 65 is 50% for women and 37% for men, rising to 55% and 46%, respectively, at age 85. This general pattern varied somewhat across regions. The regional results point to inequities in the uptake of care, thereby informing providers, governments, aged care advocates and anyone interested in equity of access.

Hormetic effects of thiamethoxam on Schizaphis graminum: demographics and feeding behavior

In agroecosystems, insects contend with chemical insecticides often encountered at sublethal concentrations. Insects’ exposure to these mild stresses may induce hormetic effects, which has consequences for managing insect pests. In this study, we used an electrical penetration graph (EPG) technique to investigate the feeding behavior and an age-stage, two-sex life table approach to estimate the sublethal effects of thiamethoxam on greenbug, Schizaphis graminum. The LC5 and LC10 of thiamethoxam significantly decreased longevity and fecundity of directly exposed adult aphids (F0). However, the adult longevity, fecundity, and reproductive days (RPd)—indicating the number of days in which the females produce offspring – in the progeny generation (F1) exhibited significant increase when parental aphids (F0) were treated with LC5 of the active ingredient. Subsequently, key demographic parameters such as intrinsic rate of increase (r) and net reproductive rate (R0) significantly increased at LC5 treatment. EPG recordings showed that total durations of non-probing (Np), intercellular stylet pathway (C), and salivary secretion into the sieve element (E1) were significantly increased, while mean duration of probing (Pr) and total duration of phloem sap ingestion and concurrent salivation (E2) were decreased in F0 adults exposed to LC5 and LC10. Interestingly, in the F1 generation, total duration of Np was significantly decreased while total duration of E2 was increased in LC5 treatment. Taken together, our results showed that an LC5 of thiamethoxam induces intergenerational hormetic effects on the demographic parameters and feeding behavior of F1 individuals of S. graminum. These findings have important implications on chemical control against S. graminum and highlight the need for a deeper understanding of the ecological consequences of such exposures within pest management strategies across the agricultural landscapes.

Estimating the Sex Gap in Depression-Free Life Expectancy Among Widowed Americans Aged 50 and Older: An Application Using the Interpolated Markov Chain Approach.

Using Interpolated Markov Chain software, we compare the length of life with and without depression among married individuals and widowers, and the related sex differences. We applied a multi-state life table approach to estimate depression-free life expectancy among recent cohorts of older married and widowed women and men in the United States, using data from the Health and Retirement Study over a 7-year period (2012-2018). The study revealed that the difference in life expectancy between sexes widens in the context of widowhood. At age 50, the sex gap in depression-free life expectancy is 0.8years among married people, whereas the gap almost doubles to 1.7years among widowed people. By quantifying disparities in the duration of life affected by depression between married and widowed women and men, policymakers could properly allocate resources specifically to address the mental health needs of these groups.

HAPPY LIFE EXPECTANCY AND REGIONAL AND GROUP HETEROGENEITY AMONG CHINESE OLDER ADULTS

Abstract A long, healthy and happy life is the aspiration of most people and an essential part of human well-being. However, longer life expectancy does not mean a higher quality of life. The measure of quality of life includes both objective and subjective indicators. Similar to healthy life expectancy, happy life expectancy is a measure that combines life expectancy with happiness indicators and can reflect both life length and quality of life. But at present, there is relatively little research on happy life expectancy. In China, there have been no studies using panel data to calculate happy life expectancy. We obtained longitudinal data from the Chinese Longitudinal Health Longevity Survey (CLHLS). We used the multistate life table approach to calculate the happy life expectancy of Chinese older adults, and analyzed the regional and group heterogeneity. A total of 13,807 participants aged 65 and older were included in this study. We found that the proportion of happy life expectancy to remaining life of Chinese older adults increased with age, which confirmed the “compression of unhappiness” hypothesis. In addition, older adults with more education had a higher proportion of happy life expectancy than those with less education. Finally, in terms of region, older adults in the more economically developed areas of eastern China have a higher proportion of happy life expectancy. Our findings provide a more comprehensive understanding of the quality of life of Chinese older adults and highlight the importance of education for the happiness of older adults in later life.

Sublethal effects of imidacloprid on the fitness of two species of wheat aphids, Schizaphis graminum (R.) and Rhopalosiphum padi (L.).

Imidacloprid is a neonicotinoid insecticide that efficiently controls piercing-sucking mouthparts pests. However, the impact of low lethal concentration of imidacloprid on key demographic parameters of wheat aphids, Schizaphis graminum (R.) and Rhopalosiphum padi (L.) has been scarcely studied. In this study, we used the age stage, two-sex life table approach to investigate the sublethal effects of imidacloprid on the biological traits of S. graminum and R. padi. Bioassays showed that imidacloprid possesses high toxicity to adult S. graminum and R. padi, with LC50 of 3.59 and 13.78 mg L-1 following 24 h exposure. A low lethal concentration of imidacloprid (LC25) significantly decreased adult longevity and total longevity of progeny generation aphids (F1) of S. graminum. Nevertheless, imidacloprid (LC25) had no significant effects on the fecundity and longevity of directly exposed parental parental S. graminum and R. padi (F0). Our results showed that the low lethal concentration of imidacloprid affected the demographic parameters that ultimately impact on the population of S. graminum. This study provides detailed information about the overall effects of imidacloprid on S. graminum and R. padi that might help to manage these two key pests.

Disability and morbidity among US birth cohorts, 1998–2018: A multidimensional test of dynamic equilibrium theory

A substantial body of prior research has explored patterns of disability-free and morbidity-free life expectancy among older populations. However, these distinct facets of later-life health are almost always studied in isolation, even though they are very likely to be related. Using data from the US Health and Retirement Study and a multistate life table approach, this paper explores the interactions between disability, morbidity, and mortality by sex and education among four successive US birth cohorts, born from 1914 to 1923 to 1944–1953 and compared in the periods 1998–2008 and 2008–2018. We find little compression of disability but a marked expansion of morbidity across cohorts. However, disability-free life expectancy (DFLE) among those living with chronic morbidities has increased, even though at the population-level DFLE is largely unchanged. Broadly, these patterns suggest that successive cohorts of older populations in the US are experiencing a dynamic equilibrium, where the link between chronic morbidities and disability has weakened over successive cohorts. Investigating patterns by educational attainment, we find marked disparities where the least educated individuals not only live significantly fewer years free of disabilities or chronic morbidities but also have experienced an expansion in morbidity and disability. Our findings suggest that the future trajectory of disability-free life expectancy in the US is increasingly contingent on efforts to improve disease management and control the severe consequences of chronic morbidities.

Application of a life table approach to assess duration of BNT162b2 vaccine-derived immunity by age using COVID-19 case surveillance data during the Omicron variant period.

SARS-CoV-2 Omicron variants have the potential to impact vaccine effectiveness and duration of vaccine-derived immunity. We analyzed U.S. multi-jurisdictional COVID-19 vaccine breakthrough surveillance data to examine potential waning of protection against SARS-CoV-2 infection for the Pfizer-BioNTech (BNT162b) primary vaccination series by age. Weekly numbers of SARS-CoV-2 infections during January 16, 2022-May 28, 2022 were analyzed by age group from 22 U.S. jurisdictions that routinely linked COVID-19 case surveillance and immunization data. A life table approach incorporating line-listed and aggregated COVID-19 case datasets with vaccine administration and U.S. Census data was used to estimate hazard rates of SARS-CoV-2 infections, hazard rate ratios (HRR) and percent reductions in hazard rate comparing unvaccinated people to people vaccinated with a Pfizer-BioNTech primary series only, by age group and time since vaccination. The percent reduction in hazard rates for persons 2 weeks after vaccination with a Pfizer-BioNTech primary series compared with unvaccinated persons was lowest among children aged 5-11 years at 35.5% (95% CI: 33.3%, 37.6%) compared to the older age groups, which ranged from 68.7%-89.6%. By 19 weeks after vaccination, all age groups showed decreases in the percent reduction in the hazard rates compared with unvaccinated people; with the largest declines observed among those aged 5-11 and 12-17 years and more modest declines observed among those 18 years and older. The decline in vaccine protection against SARS-CoV-2 infection observed in this study is consistent with other studies and demonstrates that national case surveillance data were useful for assessing early signals in age-specific waning of vaccine protection during the initial period of SARS-CoV-2 Omicron variant predominance. The potential for waning immunity during the Omicron period emphasizes the importance of continued monitoring and consideration of optimal timing and provision of booster doses in the future.

Flexible parametric methods for calculating life expectancy in small populations

BackgroundLife expectancy is a simple measure of assessing health differences between two or more populations but current life expectancy calculations are not reliable for small populations. A potential solution to this is to borrow strength from larger populations from the same source, but this has not formally been investigated.MethodsUsing data on 451,222 individuals from the Clinical Practice Research Datalink on the presence/absence of intellectual disability and type 2 diabetes mellitus, we compared stratified and combined flexible parametric models, and Chiang’s methods, for calculating life expectancy. Confidence intervals were calculated using the Delta method, Chiang’s adjusted life table approach and bootstrapping.ResultsThe flexible parametric models allowed calculation of life expectancy by exact age and beyond traditional life expectancy age thresholds. The combined model that fit age interaction effects as a spline term provided less bias and greater statistical precision for small covariate subgroups by borrowing strength from the larger subgroups. However, careful consideration of the distribution of events in the smallest group was needed.ConclusionsLife expectancy is a simple measure to compare health differences between populations. The use of combined flexible parametric methods to calculate life expectancy in small samples has shown promising results by allowing life expectancy to be modelled by exact age, greater statistical precision, less bias and prediction of different covariate patterns without stratification. We recommend further investigation of their application for both policymakers and researchers.

Green Manure Crops as Food Source: Impact on the Performance of the Migratory Beet Webworm, Loxostege sticticalis (Lepidoptera: Pyralidae).

The application of green manure is crucial for achieving sustainable agriculture and animal husbandry, but pest management is often overlooked. Conducting a risk assessment for insect pests in green manure is essential. The beet webworm, Loxostege sticticalis, a polyphagous insect, is currently experiencing an outbreak in northern China, and represents a significant migratory pest. A two-sex life table and flight mill test approach was used to comprehensively evaluate the effects of three major legume green manure crops (Pisum sativam, Vicia sativa, and Vicia villosa) on the growth, development, fecundity, and flight ability of L. sticticalis in China. Our findings indicate that L. sticticalis cannot utilize V. villosa for generational development. L. sticticalis shows reduced performance on P. sativam and V. sativa compared to its suitable host Chenopodium album. However, both the population parameters (R0, r, λ, and T) and the population prediction results suggest that L. sticticalis can adapt to P. sativam and V. sativa. In the process of promoting green manure, careful consideration should be given to the selection of appropriate green manure varieties and the implementation of effective pest control measures during their planting. Our findings lay the groundwork for the promotion of green manure and implementation of an ecological management plan for L. sticticalis.

Impact of sublethal concentrations of flonicamid on key demographic parameters and feeding behavior of Schizaphis graminum.

Flonicamid is a novel systemic insecticide that efficiently controls sap-sucking insect pests. However, the impact of sublethal concentrations of flonicamid on key demographic parameters and the feeding behavior of greenbug, Schizaphis graminum has not yet been studied. In this study, we used the age stage, two-sex life table approach, and electrical penetration graphs (EPGs) to investigate the sublethal effects of flonicamid on the biological traits and feeding behavior of S. graminum. Bioassays showed that flonicamid possesses high toxicity to adult S. graminum with LC50 of 5.111 mg L-1 following 48 h exposure. Sublethal concentrations of flonicamid (LC5 and LC10) significantly decreased the longevity and fecundity of directly exposed parental aphids (F0), while the reproductive days were reduced only at LC10. The pre-adult stage and total pre-reproductive period (TPRP) increased in F1 individuals after exposure of F0 aphids to the sublethal concentrations of flonicamid. Furthermore, the adult longevity, fecundity and key demographic parameters (R0, r, and λ) were significantly reduced in progeny generation (F1). EPG recordings showed that the total duration of phloem sap ingestion and concurrent salivation (E2) decreased substantially in F0 and F1 aphids after exposure to LC5 and LC10 of flonicamid. Taken together, our results showed that the sublethal concentrations of flonicamid affect the demographic parameters and feeding behavior that ultimately suppress the population growth of S. graminum. This study provides in-depth information about the overall effects of flonicamid on S. graminum that might help to manage this key pest.

Sublethal Effects of Flonicamid on Life Table of Myzus persicae (Sulzer)

The green peach aphid, Myzus persicae (Sulzer) (Aphididae: Hemiptera) is a cosmopolitan polyphagous pest of more than five hundred plant species belonging to at least forty different plant families including several economically important agricultural crops. The sublethal effect of LC25 concentration of flonicamid on M. persicae was assessed by using an age-stage two-sex life table approach for integrated management of this pest. A leaf-dip bioassay showed that flonicamid was very toxic to the adults of M. persicae at 48 h with the calculated LC25 concentration value of 0.0115 g a.i./L. The adults (parental generation) of M. persicae exposed to the LC25 concentration (sublethal dose) of flonicamid showed inhibitory effects on the life history traits across its generations such as reduction in adult longevity and fecundity of parental generation (F0); shortening the durations of fifth instar nymphs, adult female longevity, oviposition period, total longevity and fecundity of F1 & F2 generations. On the other hand, stimulatory effects were observed on the duration of first, second, third, and fourth instar nymphs; and pre-adults in F2 generation in the flonicamid-treated aphids. Consistently with the effects on individual traits, a higher mean generation time (T) and shorter intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R0) of F2 generation were observed in the flonicamid treated aphids, although r, λ, R0, T, and gross reproductive rate (GRR) of F1 generation were not significantly affected. The findings revealed the exposure of parental adults of M. persicae to sublethal concentration of flonicamid could induce hormetic (both inhibitory and stimulatory) effects on their succeeding generations. This study is useful for assessing the overall effects of flonicamid on M. persicae. The hormetic effects should be considered when it used flonicamid in the integrated management of M. persicae in crop fields.

Comparison of the biology of Frankliniella intonsa and Megalurothrips usitatus on cowpea pods under natural regimes through an age-stage, two-sex life table approach.

Two thrips, Megalurothrips usitatus (Bagnall) and Frankliniella intonsa (Trybom) are major pests of cowpea in South China. To realistically compare the growth, development and reproductive characteristics of these two thrips species, we compared their age-stage, two-sex life tables on cowpea pods under summer and winter natural environmental regimes. The results showed that the total preadult period of M. usitatus was 8.09 days, which was significantly longer than that of F. intonsa (7.06 days), while the adult female longevity of M. usitatus (21.14 days) was significantly shorter than that of F. intonsa (25.77 days). Significant differences were showed in male adult longevity (10.68 days for F. intonsa and 16.95 days for M. usitatus) and the female ratio of offspring (0.67 for F. intonsa and 0.51 for M. usitatus), and the total preadult period of M. usitatus (16.20 days) was significantly longer than that of F. intonsa (13.66 days) in the winter regime. The net reproductive rate (summer: R0 = 85.62, winter: R0 = 105.22), intrinsic rate of increase (summer: r = 0.3020 day-1, winter: r = 0.2115 day-1), finite rate of increase (summer: λ = 1.3526 day-1, winter: λ = 1.2356 day-1) and gross reproduction rate (summer: GRR = 139.34, winter: GRR = 159.88) of F. intonsa were higher than those of M. usitatus (summer: R0 = 82.91, r = 0.2741, λ = 1.3155, GRR = 135.71; winter: R0 = 80.62, r = 0.1672, λ = 1.1820, GRR = 131.26), and the mean generation times (summer: T = 14.73 days, winter: T = 22.01 days) of F. intonsa were significantly shorter than those of M. usitatus (summer: T = 16.11 days, winter: T = 26.25 days). These results may contribute to a better understanding of the bioecology of different thrips species, especially the interspecific competition between two economically important cowpea thrips with the same ecological niche in a changing environment.

Fatal drug overdose among middle-aged Black men: A life table analysis

BackgroundFor Black men of middle-age, the overdose mortality statistics are increasingly dire. To better understand the severity of the crisis, we estimated the cumulative risk of drug overdose deaths among non-Hispanic Black men in mid-life using a period life table approach. We report the chances of Black men aged 45 years dying of a drug overdose before age 60. MethodsA period life table reflects what would happen to a hypothetical cohort if it experienced the prevailing age-specific probabilities of death. In our hypothetical cohort, we followed 100,000 non-Hispanic Black men aged 45 years for 15 years. All-cause death probabilities were obtained from the National Center for Health Statistics (NCHS) 2021 life table series. Overdose mortality rates were obtained from the National Vital Statistics System through the Wide-Ranging Online Data for Epidemiologic Research of the Centers for Disease Control and Prevention (CDC WONDER) database. We also constructed a period life table for a comparison group of White men. ResultsThe life table shows that, for Black men who are 45 years of age in the United States, 1 in 52 (nearly 2%) is expected to die of drug overdose before reaching age 60, if current mortality rates persist. For White men, the estimate is 1 in 91 men (about 1%). The life table also shows that from age 45 to 59 years, the number of overdose deaths increased in the cohort of Black men but decreased in White men. ConclusionsThis study extends our understanding of the immense loss to Black communities from the preventable drug deaths of Black men in middle-age.

Age, size and neighbors influence the survival and growth of understory trees in a naturally reproducing population of American chestnut, Castanea dentata

The seedling stage is a critical point in the life history of plants. The survival and growth of tree seedlings can be affected by both the abiotic and biotic environment. Seedlings of both tropical and temperate forests have been shown to experience conspecific negative density dependence (CNDD) and positive density dependence (facilitation). American chestnut was once a common species throughout eastern North America that was decimated by an introduced pathogen in the early 1900 s. Here we present an analysis of chestnut seedling ecology in a unique, sexually reproducing population of American chestnut in central Maine, USA, to understand how both conspecific and heterospecific canopy trees along with size and age influence the survival and growth of understory chestnut trees. Using both a cohort analysis and a static life table approach, we found that seedling survival was lower in the first year of life, and those trees that survive their first and second years had consistently high survival. Our data did not support facilitation as none of the neighborhood indices were positive. We found evidence for CNDD for American chestnuts in the first year of life, but we found no evidence for continued effects beyond the first year. Heterospecifics decreased growth and survival of understory chestnuts beyond the first year of life. Enhanced understanding of American chestnut ecology, particularly at the critical seedling stage, can guide management strategies that support reintroduction efforts.

Fitness Cost of the Field-Evolved Resistance to Sulfoxaflor and Multi-Insecticide Resistance of the Wheat Aphid Sitobion miscanthi (Takahashi).

Sulfoxaflor belongs to a new class of insecticides that is effective against many sap-feeding pests. In this study on Sitobion miscanthi (Takahashi) (i.e., the predominant wheat pest), a highly sulfoxaflor-resistant (SulR) population was obtained from a field. Its resistance to the other seven insecticides and its biological fitness were analyzed using a leaf-dip method and a two-sex life table approach, respectively. Compared with the relatively susceptible (SS) population, the SulR population was highly resistant to sulfoxaflor, with a relative insecticide resistance ratio (RR) of 199.8 and was moderately resistant to beta-cypermethrin (RR = 14.5) and bifenthrin (RR = 42.1) but exhibited low resistance to chlorpyrifos (RR = 5.7). Additionally, the SulR population had a relative fitness of 0.73, with a significantly prolonged developmental period as well as a lower survival rate and poorer reproductive performance than the SS population. In conclusion, our results suggest that S. miscanthi populations that are highly resistant to sulfoxaflor exist in the field. The possibility that insects may develop multi-resistance between sulfoxaflor and pyrethroids is a concern. Furthermore, the high sulfoxaflor resistance of S. miscanthi was accompanied by a considerable fitness cost. The study data may be useful for improving the rational use of insecticides and for exploring novel insecticide resistance mechanisms.

Optimisation of laboratory-rearing parameters for Anopheles funestus larvae and adults

Anopheles funestus is one of the major malaria vectors in Africa. As with the other main vectors, insecticide resistance in this species threatens existing vector control strategies. Unfortunately, scientific investigations, which could improve understanding of this vector species or lead to the development of new control strategies, are currently limited by difficulties in laboratory rearing of the species. In an attempt to optimise laboratory-rearing conditions for An. funestus, the effect of an artificial blood-feeding system for adults, different larval diet doses, and a range of other rearing conditions on the life history traits of an existing colony were investigated. Firstly, fecundity and fertility in An. funestus adult females fed on either live guinea pigs or bovine blood supplied through an artificial membrane feeding system were assessed. Secondly, a life-table approach was used to assess the impact of larval food dose (mg/larvae), larval density (larvae/cm2), and the depth of water used for larval rearing on life history traits. Fecundity was significantly higher when females were blood-fed on live anaesthetised guinea pigs than when fed on defibrinated bovine blood. However, the fertility of these eggs did not differ significantly between the two feeding methods or blood meal sources. Mosquitoes fed on defibrinated bovine blood using the artificial membrane feeding system showed an increase in egg production when the blood-feeding frequency was increased, but this difference was not statistically significant. The quantity of larval food influenced both time-to-pupation and pupal production. Increasing the larval densities resulted in reduced both time-to-pupation and pupal productivity. An optimal larval density of 0.48 larvae/cm2 was vital in preventing overcrowding. Increased water depth in the larval trays, was associated with significantly lower pupal production and reduced pupal weight. In conclusion, these results show that An. funestus can be reared using defibrinated bovine blood delivered via an artificial membrane feeding system. The quantity of larval food, optimal larval density, and depth of water used for larval rearing are critical factors influencing colony productivity. These findings can be used to improve current guidelines for rearing An. funestus under insectary conditions.