Insecticide Sprays Research Articles

Mosquito-borne diseases, their impacts and mosquito vector control methods - A review

Vector borne diseases are increasing nowadays and can spread to new locations easily. Diseases like zika virus fever, West Nile fever, malaria, yellow fever, Japanese encephalitis, dengue, etc. are examples of mosquito-borne diseases. These diseases are majorly caused by three species of mosquitoes Anopheles, Aedes, and Culex. Most mosquito vector control methods depend upon outdoor spraying, impregnated nets, or indoor residual spraying of chemical insecticides and it was observed that many mosquito species evolved resistance to major pesticide classes. The disadvantages of using chemical pesticides are the development of resistance in mosquitoes and also the harm it causes to other non-target organisms, in addition to the higher cost, more labor, and other drawbacks. Using DEET is also not as preferable as it can induce muscle twitching, seizures, slurred speech, nausea, and rashes. DEET will not give long-term protection against all malaria-causing mosquito species, such as Anopheles. Whereas biocontrol agents used for mosquito control show no environmental pollution or resistance. Bacillus thuringiensis israelensis and Bacillus sphaericus biopesticides tend to remain longer in the environment, particularly in dirty water, and hence may be a viable choice for long-term mosquito control. They have the least adverse effect on living things like humans, domestic animals, and wildlife.

The Prevalence of Malaria Parasites and the Dynamics of Malaria Vectors in Adenta-Barrier in Ghana

Background: Malaria burden is generally lower in urban settings. Urban malaria is likely to surge due to rapid and unplanned urbanization. Hence, this study sought to determine the prevalence of malaria parasite and malaria vectors in Adenta-barrier, a suburb of Adentan Municipality.
 Methods: The study followed a cross sectional study design pattern. Mosquitoes were collected from 40 houses in the study site using the pyrethrum spray catches (PSC) method, and malaria parasite screening was carried out on 90 participants. A well-structured form was used to record data on the use of insecticide-treated nets, insecticide spray, and mosquito coil in the community. The mosquitoes collected were morphologically identified.
 Results: The malaria parasite prevalence at the study site was 1.1%, and the use of insecticide-treated nets, insecticide spray, and mosquito coil were 13.4%, 7.5%, and 11.9% respectively. As far as vector abundance were concerned, habitat, resting and feeding behavior were taken into consideration. The majority of the mosquitoes collected during the study were Culex 95.7% (22), and the rest was Aedes 4.3% (1). Both Culex and Aedes mosquitoes were found in resting states. Study participants reported majority (80%) of the bites they sustained to have occurred during the early hours of the day. The study area also possessed several easily identifiable breeding sites for mosquitoes.
 Conclusion: The prevalence of malaria in the study area was low and no Anopheles mosquitoes was found. The majority of mosquito species present in the locality was Culex with a few Aedes.

Evaluation of the Efficacy of Fludora® Fusion WP-SB 56.25 (Mixture of Clothianidin and Deltamethrin) against Anopheles coluzzii Laboratory and An. arabiensis Wild Colonies.

For malaria control, the application of long-lasting insecticidal nets and indoor residual spraying has led to a significant reduction in morbidity and mortality. However, the sustainability of these gains is hampered by the increase in insecticide resistance. It is therefore judicious to evaluate new insecticide formulations. In comparison to clothianidin and deltamethrin, the efficacy and residual effect of Fludora® Fusion was evaluated using an Anopheles coluzzii laboratory and An. arabiensis wild colonies in huts from August 2016 to June 2017 on cement and mud walls. Mortality was recorded at 24, 48, 72, and 96 h post exposure. Like deltamethrin and clothianidin, Fludora® Fusion showed delayed mortality rates above the WHO’s 80% threshold over a period of 11 months with the laboratory strain. With the wild strain, while residual efficacy was observed at 2 months for the three insecticides, no residual efficacy was observed at 8 months at 24 h in both substrates. However, the increased efficacy was observed with increased holding periods (72 h and 96 h). These findings suggest that Fludora® Fusion could be an alternative candidate since this duration covers the transmission period in most areas in Senegal.

The economic cost of bovine trypanosomosis in pastoral and ago pastoral communities surrounding Murchision Falls National park, Buliisa district, Uganda

Background:Animal diseases that are endemic like tsetse transmitted trypanosomosis cause the continuous expenditure of financial resources of livestock farmers and loss of productivity of livestock. Estimating the cost of controlling animal trypanosomosis can provide evidence for priority setting and targeting cost-effective control strategies.Methodology:A cross-sectional survey to estimate the economic cost of bovine trypanosomosis was conducted in cattle-keeping communities living around Murchision falls National Park, in Buliisa district Uganda. Data was collected on herd structure, the cost of treatment and control, prevalence of morbidity and mortality rates due to trypanosomosis, and salvage sales losses in cattle herds in the last year.Results:In this study, 55.4% (n = 87) of the households reported their cattle had been affected by trypanosomosis during the previous last year. There was a high economic cost of trypanosomosis (USD 653) per household in cattle-keeping communities in Buliisa district of which 83% and 9% were due to mortality and milk loss respectively/ High mortality loss was due to low investment in treatment. The study showed that prophylactic treatment 3 times a year of the whole herd of cattle using Samorin ® (Isometamidium chloride) at a cost of USD 110 could drastically reduce cattle mortality loss due to trypanosomosis due to trypanosomosis with a return on investment of USD 540 annually per herd. This could be coupled with strategic restricted insecticide spraying of cattle with deltamethrin products.Conclusion:The results show a high economic cost of trypanosomosis in cattle-keeping communities in Buliisa district, with cattle mortality contributing the largest proportion of the economic cost. The high mortality loss was due to low investment in treatment of sick cattle.

Evaluation of the Efficacy of Flupyradifurone against Bemisia tabaci on Cassava in Tanzania.

Simple SummaryCassava-colonizing Bemisia tabaci whitefly negatively impact cassava production in sub-Saharan Africa through transmission of viruses that cause cassava mosaic disease (CMD) and cassava brown streak disease (CBSD). This study evaluated the efficacy of a novel insecticide flupyradifurone against this whitefly pest through standard spraying and cutting dip methods. The results from the laboratory, screenhouse and field experiments consistently showed flupyradifurone is effective at reducing whiteflies compared to control treatments. A single cutting dip using this insecticide was highly effective at reducing whiteflies under field conditions and, therefore, should be considered as an alternative to insecticide spraying in cassava systems. Additionally, whiteflies were least abundant during the long rainy season (Masika) and on cassava variety Mkuranga1.A novel butenolide insecticide—flupyradifurone (Sivanto SL 200)—was evaluated for efficacy against cassava-colonizing Bemisia tabaci whitefly under laboratory, screenhouse and field conditions. LC50 values from leaf disc spray assays were comparable for both flupyradifurone (12.7 g a.i/100 L) and imidacloprid (12.6 g a.i/100 L). Both insecticides caused high levels of adult whitefly mortality in leaf disc and leaf dip assays when compared to untreated controls. In screenhouse-based trials, longer soaking (60 min) with flupyradifurone or imidacloprid was more effective than shorter soaking durations (15 or 30 min). In field spraying experiments, flupyradifurone significantly reduced whiteflies, and both insecticides demonstrated powerful knockdown effects on whitefly adult abundances over a period up to 24 h. Single cutting dip application of flupyradifurone reduced whitefly adult abundance by 2 to 6 times, and nymphs by 2 to 13 times. Lower whitefly abundances resulting from insecticide application reduced the incidence of CMD or CBSD. In addition, in field experiments, whiteflies were fewer during the long rainy season (Masika) and on cassava variety Mkuranga1. The findings from this study demonstrate that cutting dips with flupyradifurone could be incorporated as a management tactic against cassava whiteflies. This would ideally be combined in an IPM strategy with other cassava virus and virus vector management tactics including host-plant resistance, phytosanitation and the use of clean seed.

East Africa International Center of Excellence for Malaria Research: Summary of Key Research Findings.

The Program for Resistance, Immunology, Surveillance, and Modeling of Malaria (PRISM) has been conducting malaria research in Uganda since 2010 to improve the understanding of the disease and measure the impact of population-level control interventions in the country. Here, we will summarize key research findings from a series of studies addressing routine health facility-based surveillance, comprehensive cohort studies, studies of the molecular epidemiology, and transmission of malaria, evaluation of antimalarial drug efficacy, and resistance across the country, and assessments of insecticide resistance. Among our key findings are the following. First, we found that in historically high transmission areas of Uganda, a combination of universal distribution of long-lasting insecticidal-treated nets (LLINs) and sustained indoor residual spraying (IRS) of insecticides lowered the malaria burden greatly, but marked resurgences occurred if IRS was discontinued. Second, submicroscopic infections are common and key drivers of malaria transmission, especially in school-age children (5-15 years). Third, markers of drug resistance have changed over time, with new concerning emergence of markers predicting resistance to artemisinin antimalarials. Fourth, insecticide resistance monitoring has demonstrated high levels of resistance to pyrethroids, appreciable impact of the synergist piperonyl butoxide to pyrethroid susceptibility, emerging resistance to carbamates, and complete susceptibility of malaria vectors to organophosphates, which could have important implications for vector control interventions. Overall, PRISM has yielded a wealth of information informing researchers and policy-makers on the malaria burden and opportunities for improved malaria control and eventual elimination in Uganda. Continued studies concerning all the types of surveillance discussed above are ongoing.

East Africa International Center of Excellence for Malaria Research: Impact on Malaria Policy in Uganda.

Malaria is the leading cause of disease burden in sub-Saharan Africa. In 2010, the East Africa International Center of Excellence for Malaria Research, also known as the Program for Resistance, Immunology, Surveillance, and Modeling of Malaria (PRISM), was established to provide a comprehensive approach to malaria surveillance in Uganda. We instituted cohort studies and a robust malaria and entomological surveillance network at selected public health facilities that have provided a platform for monitoring trends in malaria morbidity and mortality, tracking the impact of malaria control interventions (indoor residual spraying of insecticide [IRS], use of long-lasting insecticidal nets [LLINs], and case management with artemisinin-based combination therapies [ACTs]), as well as monitoring of antimalarial drug and insecticide resistance. PRISM studies have informed Uganda's malaria treatment policies, guided selection of LLINs for national distribution campaigns, and revealed widespread pyrethroid resistance, which led to changes in insecticides delivered through IRS. Our continuous engagement and interaction with policy makers at the Ugandan Ministry of Health have enabled PRISM to share evidence, best practices, and lessons learned with key malaria stakeholders, participate in malaria control program reviews, and contribute to malaria policy and national guidelines. Here, we present an overview of interactions between PRISM team members and Ugandan policy makers to demonstrate how PRISM's research has influenced malaria policy and control in Uganda.

Strategies for the production of dsRNA biocontrols as alternatives to chemical pesticides.

Current crop pest control strategies rely on insecticidal and fungicidal sprays, plant genetic resistance, transgenes and agricultural practices. However, many insects, plant viruses, and fungi have no current means of control or have developed resistance against traditional pesticides. dsRNA is emerging as a novel sustainable method of plant protection as an alternative to traditional chemical pesticides. The successful commercialisation of dsRNA based biocontrols for effective pest management strategies requires the economical production of large quantities of dsRNA combined with suitable delivery methods to ensure RNAi efficacy against the target pest. A number of methods exist for the production and delivery of dsRNA based biocontrols and here we review alternative methods currently employed and emerging new approaches for their production. Additionally, we highlight potential challenges that will need to be addressed prior to widespread adoption of dsRNA biocontrols as novel sustainable alternatives to traditional chemical pesticides.

A Review on Antimalarial Activities of Aloe species Extracts

Among the most prevalent diseases caused by protozoan parasites, the parasites of the genus Plasmodium cause malaria. Malaria is transmitted to humans by the infected female anopheles mosquito. Malaria is a vector-borne disease and it continues to have devastating effects on people’s lives, especially in developing countries. To control malaria, many popular practices exist to avoid the nuisance of mosquito bites such as fumigation, burning green leaves on the hut’s threshold, mosquito coils, insecticide sprays, and repellents. Due to the vast metabolic diversity of plants, natural products may offer relatively cheaper and an easy alternative treatment opportunity to treat malaria. The genus Aloe is one of the top medicinal plants that has maintained its popularity over the course of time. Aloe in one form or another is a common domestic medicine and is the basis of most pharmaceutical preparations. Various components present in the Aloe species have been found effective against many diseases, including malaria. Although most of the antimalarial activities were based on in vivo tests, in vitrotests were also analyzed by certain researchers. The leaf latex in all Aloespecies and the isolated compounds displayed antimalarial activity in a dose-independent manner. Considering that natural molecules have acted as natural templates in the development of antimalarial agents, it is encouraged to investigate further analyses into Aloe constituents and their values against malaria. It should be followed with phytochemical and pharmacological analyses to give scientific ground to medicinal knowledge and future potential utilization.

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

BackgroundNear-infrared spectroscopy (NIRS) has the potential to be a useful tool for assessing key entomological parameters of malaria-transmitting mosquitoes, including age, infectious status and species identity. However, before NIRS can be reliably used in the field at scale, methods for killing mosquitoes and conserving samples prior to NIRS scanning need to be further optimized. Historically, mosquitoes used in studies have been killed with chloroform, although this approach is not without health hazards and should not be used in human dwellings. For the application of NIRS scanning it is also unclear which mosquito preservation method to use. The aim of the study reported here was to investigate the use of pyrethrum spray, a commercially available insecticide spray in Burkina Faso, for killing mosquitoesMethodsLaboratory-reared Anopheles gambiae and Anopheles coluzzii were killed using either a pyrethrum insecticide spray routinely used in studies involving indoor mosquito collections (Kaltox Paalga®; Saphyto, Bobo-Dioulasso, Burkina Faso) or chloroform (“gold standard”). Preservative methods were also investigated to determine their impact on NIRS accuracy in predicting the species of laboratory-reared Anopheles and wild-caught mosquito species. After analysis of fresh samples, mosquitoes were stored in 80% ethanol or in silica gel for 2 weeks and re-analyzed by NIRS. In addition, experimentally infected An. coluzzii and wild-caught An. gambiae sensu lato (s.l.) were scanned as fresh samples to determine whether they contained sporozoites, then stored in the preservatives mentioned above for 2 weeks before being re-analyzed.ResultsThe difference in the accuracy of NIRS to differentiate between laboratory-reared An. gambiae mosquitoes and An. coluzzii mosquitoes killed with either insecticide (90%) or chloroform (92%) was not substantial. NIRS had an accuracy of 90% in determining mosquito species for mosquitoes killed with chloroform and preserved in ethanol or silica gel. The accuracy was the same when the pyrethrum spray was used to kill mosquitoes followed by preservation in silica gel, but was lower when ethanol was used as a preservative (80%). Regarding infection status, NIRS was able to differentiate between infected and uninfected mosquitoes, with a slightly lower accuracy for both laboratory and wild-caught mosquitoes preserved in silica gel or ethanol.ConclusionsThe results show that NIRS can be used to classify An. gambiae s.l. species killed by pyrethrum spray with no loss of accuracy. This insecticide may have practical advantages over chloroform for the killing of mosquitoes in NIRS analysis.Graphical Supplementary InformationThe online version contains supplementary material available at 10.1186/s13071-022-05458-6.

Effect of saturated treatment on malaria spread with optimal intervention

This work presents a new deterministic model which considers transmission mode through blood transfusion and saturated treatment function with a view to gaining more insights into the dynamical spread of malaria. Existence of steady states of the model is established analytically. The key epidemiological threshold (R0) which determines the potential spread of malaria is computed using the next generation matrix method. The model has a locally asymptotically stable disease-free equilibrium point at R0<1, and condition which ensures the appearance of two endemic equilibria at R0<1 suggesting the possibility of backward bifurcation is determined. It is shown, using Lyapunov function, that a unique endemic equilibrium point is globally asymptotically stable at R0>1. Moreover, the model is modified by incorporating four time-dependent optimal control variables, namely insecticide-treated nets targeted at vector-human transmission route, screening of blood against human–human blood transfusion, anti-malaria drug treatment and vector control with insecticide spraying. Optimal control theory with the aid of Pontryagin’s maximum principle is applied to characterize the optimal control quadruple. Based on efficiency and cost-effectiveness analyses carried out, the most efficient and the most cost-effective combination of the four controls that can be implemented to reduce the burden of malaria in the population are obtained.

Two-stage automatic diagnosis of Flavescence Dorée based on proximal imaging and artificial intelligence: a multi-year and multi-variety experimental study

“Flavescence dorée” (FD) is a grape vine disease caused by the bacterial agent “Candidatus Phytoplasma vitis” and spread by the leafhopper Scaphoideus titanus Ball (Hemiptera: Cicadellidae). The disease is very closely monitored in Europe, as it reduces vine productivity and causes vine death and is also highly transmissible. Currently, the control method used against this disease is a two-pronged approach: i) the spraying of insecticide on a regular basis to kill the vector, and ii) a survey of each row in a vineyard by experts in this disease. Unfortunately, these experts are not able to carry out such a task every year on every vineyard and need an aid for planning their survey.In this study, we propose and evaluate an original automatic method for the detection of FD based on computer vision and artificial intelligence algorithms applied to images acquired by proximal sensing. A two-step approach was used, mimicking an expert’s scouting in the vine rows: (i) the three known isolated symptoms (red or yellow leaves depending on variety, together with a lack of shoot lignification and the presence of desiccated bunches) were detected, (ii) isolated detections were combined to make a diagnosis at image scale; i.e., vine scale. A detection network was used to detect and classify non-healthy leaves into three classes: ‘FD symptomatic leaf', 'Esca leaf' and 'Confounding leaf'; while a segmentation network was used for the retrieval of FD symptomatic shoots and bunches. Finally, the association of detected symptoms was performed by a RandomForest classifier for diagnosis at the image scale. The experimental evaluation was conducted on more than 1000 images collected from 14 blocks planted with five different grape varieties. The detection of the isolated symptoms achieved a precision of between 0.67 and 0.82 and a recall of between 0.39 and 0.59. The classification at the image scale obtained very good results when applied to images acquired under the same conditions, with the same grape varieties as the training images (precision and recall of more than 0.89). The results of the tests on the other grape varieties show the importance of having some of them in the training base in these AI-based approaches.

Microbe-mediated activation of indoxacarb in German cockroach (Blattella germanica L.)

The German cockroach (Blattella germanica L.) is a major urban pest worldwide and is notorious for its ability to detoxify and resist insecticides. German cockroaches have generalist feeding habits that expose them to a range of potential hazardous substances and host a wide variety of unique microbial species, which may potentially facilitate unique detoxification capabilities. Since field German cockroach populations are routinely exposed to both bait and spray insecticide treatments, we hypothesized whether these unique gut microbes might play roles in toxicological processes of the host insect. The goals of this research were to understand the metabolic processes inside the German cockroach gut after treatment with kanamycin, a broad-ranging antibiotic, and indoxacarb, an oxadiazine pro-insecticide used in cockroach bait products. In these experiments, two resistant cockroach strains were obtained from field populations in Danville, IL and compared to a susceptible laboratory strain that had no previous exposure to insecticides (J-wax). Roaches provided kanamycin-infused water had lower median mortality to indoxacarb compared to the control treatment in feeding bioassays regardless of strain, but in vial (surface contact) bioassays, only susceptible cockroaches experienced a shift in mortality apparently due to their greater susceptibility. When frass extracts of indoxacarb-fed cockroaches were analyzed, less of the active, hydrolytic metabolite DCJW (N-decarbomethoxyllated JW062) was produced relative to the parent compound indoxacarb with the antibiotic KAN. This result was further corroborated by hydrolase activity assays of whole homogenized cockroach guts. Taken together these results provide novel evidence of microbe-mediated pro-insecticide activation in the cockroach gut.

An innovative three-layer strategy in response to a quartan malaria outbreak among forest goers in Hainan Island, China: a retrospective study

BackgroundAn outbreak of Plasmodiummalariae infection among forest goers in Sanya City of Hainan Island, China was reported in 2015. In response to this outbreak, an innovative three-layer strategy (TLS) targeted forest goers was adapted based on the 1-3-7 approach.Main textKey elements of TLS are: (i) The village with five malaria cases and adjacent villages were set as the first layer. All residents including forest goers were taken as the high-risk population (HRP). Active case detection (ACD) by blood smear microscopy and PCR was selected as the primary measure, and passive case detection (PCD) as complementary measure. One case was identified under TLS implementation. (ii) The township with cases (Gaofeng Town) and the nearby towns were chosen as the second layer. Only forest goers were screened by ACD, while PCD as a routine screening method. 7831 blood smears collected by ACD and PCD and tested with negative results. (iii) The city with cases (Sanya City) and others 12 counties/county-level cities were selected as the third layer. Malaria cases were monitored passively. A total of 77,555 blood slides were screened by PCD with zero positive sample. For each layer, the malaria vector mosquitoes were monitored using light traps, cattle-baited/human-bait traps.Anophelesminimus (dominant species), An.sinensis and An.dirus were captured. Vector control measures mainly include insecticide residual spraying and long-lasting insecticide nets. The capacity of clinicians, public health practitioners and laboratory technicians has been improved through training. During 2016‒2018, TLS and chemoprophylaxis were implemented in the same areas. In the first layer, all residents were monitored by ACD, and malaria chemoprophylaxis were distributed, 89.5% of forest goers were using chemoprophylaxis against malaria. The blood smears (3126 by ACD plus 1516 by PCD) were with zero positive results. Chemoprophylaxis and ACD were offered to forest goers once a year, and PCD in residents as a complementary measure in the second and third layer, 77.8% and 95.1% of forest goers received chemoprophylaxis. In each layer, vector surveillance and control of malaria and trainings for medical staff were still in place.ConclusionsTLS was effective in blocking the outbreak by P.malariae among forest goers in Hainan in malaria elimination stage. However, whether it could prevent the malaria resurgence in the post-elimination phase needs to be further assessed.Graphical

Toxicity and sublethal effects of diafenthiuron on life table parameters of Musca domestica L. (Diptera: Muscidae)

Housefly, Musca domestica L. (Diptera: Muscidae), is an important insect-pest owing to its disease transmitting capability in both humans and animals e.g. diarrhea, gastroenteritis diseases, lumpy skin disease, cholera. Residual insecticides are widely used to control houseflies that pose serious threat to human and animal health as well as to the environment. The population resurgence after insecticidal spray is also a common problem in many cases. Transgenerational studies can be very helpful to see the fate of insecticidal sprays. In the current study, we determined transgenerational effects of sublethal doses of diafenthiuron using Age-stage two-sex life table analysis, while focusing on potential use of diafenthiuron in baits. After treating adult flies with three different doses of diafenthiuron viz. LC10, LC20 and LC50, the progeny depicted significant changes regarding pre-adult duration (shorter in control), male and female longevity of their progeny were observed (more adult longevity in control). Additionally, population growth parameters viz. intrinsic rate of growth (r) (−0.03-0.12 per day), net reproductive rate (R0) (0.50–9.98), limiting rate of growth (λ) (0.96–1.13 per day) were also significantly reduced in the progeny of treated adults. Based on the decreased biotic potential i.e. intrinsic rate of growth and other population parameters, diafenthiuron can be recommended as an effective insecticide even at lower doses.

Resurgence of malaria in Uganda despite sustained indoor residual spraying and repeated long lasting insecticidal net distributions.

Five years of sustained indoor residual spraying (IRS) of insecticide from 2014 to 2019, first using a carbamate followed by an organophosphate, was associated with a marked reduction in the incidence of malaria in five districts of Uganda. We assessed changes in malaria incidence over an additional 21 months, corresponding to a change in IRS formulations using clothianidin with and without deltamethrin. Using enhanced health facility surveillance data, our objectives were to 1) estimate the impact of IRS on monthly malaria case counts at five surveillance sites over a 6.75 year period, and 2) compare monthly case counts at five facilities receiving IRS to ten facilities in neighboring districts not receiving IRS. For both objectives, we specified mixed effects negative binomial regression models with random intercepts for surveillance site adjusting for rainfall, season, care-seeking, and malaria diagnostic. Following the implementation of IRS, cases were 84% lower in years 4-5 (adjusted incidence rate ratio [aIRR] = 0.16, 95% CI 0.12-0.22), 43% lower in year 6 (aIRR = 0.57, 95% CI 0.44-0.74), and 39% higher in the first 9 months of year 7 (aIRR = 1.39, 95% CI 0.97-1.97) compared to pre-IRS levels. Cases were 67% lower in IRS sites than non-IRS sites in year 6 (aIRR = 0.33, 95% CI 0.17-0.63) but 38% higher in the first 9 months of year 7 (aIRR = 1.38, 95% CI 0.90-2.11). We observed a resurgence in malaria to pre-IRS levels despite sustained IRS. The timing of this resurgence corresponded to a change of active ingredient. Further research is needed to determine causality.

Trends in agrichemical use on stonefruit orchards in New Zealand from 2004–2019

ABSTRACT Annual spray diaries from orchardists in the two main stonefruit growing regions, Central Otago and Hawke’s Bay, were analysed. The analysis was restricted to products for disease and arthropod pest control. It included apricots, cherries, nectarines, peaches and plums grown as fresh fruit for export and domestic markets, and processing crops. Mean fungicide and bactericide applications declined from 13 to 9/block/year in Central Otago, but rose from 11 to 13 sprays in Hawke’s Bay. Central Otago is drier than Hawke’s Bay and the regional spray programmes now better match the respective climates. Despite large annual variations in rainfall and numbers of brown rot (Monilinia fructicola) infection periods in both regions, there was little correlation with the numbers of fungicides applied that had activity against brown rot. The products used against diseases changed substantially during the study period. Insecticide and miticide sprays averaged 5 applications per year in Central Otago at the start of the study and declined to 4-6/crop/year (overall mean of 4) by 2018–19. Hawke’s Bay growers used 1–3 insecticide sprays per crop (overall mean of 2) throughout the study. The proportion of selective insecticides applied grew in Central Otago, but fell in Hawke’s Bay.

Prevalence and Management of Falciparum Malaria among Febrile Patients in South-western Nigeria

The World Health Organization reported 241 million cases and 627,000 death from malaria in 2020 and Nigeria accounted for 27% of malaria death worldwide. Effective tools are continually developed through global efforts to have a malaria-free world. The study was aimed at assessing the prevalence and management of falciparum malaria among febrile patients in South-western Nigeria. This is a cross-sectional descriptive study conducted on febrile patients undergoing treatment at the outpatient units of selected hospitals in Ekiti and Ondo States, Nigeria between August 2019 and January, 2021. A total of 399 participants were enlisted in the study following informed consent. A structured questionnaire was administered to obtain socio-demographic information and the management of malaria among the participant and blood collected from them for malaria examination by microscopy and rapid test diagnosis. Two hundred and ninety-five (73.9%) of the subjects were females and 104(26.1%) males, with modal age of 21–28 years. There were 171(42.9%) and 228(57.1%) participants from Ekiti and Ondo States respectively. Subjects from Ondo State reported significantly higher occurrence of malaria than their counterparts from Ekiti State (p=0.005). Malaria occurrence was found to be significantly associated with age (p=0.047), occupation (p=0.001), individual’s perception of approach to malaria treatment (p=0.002) and use of local herbs (p=0.002). Artemisinin-based combination therapies (ACTs) were drugs of choice (76.3%) by the respondents; other drugs commonly used were Sulphadoxine-pyrimethamine (13.3%) and chloroquine/quinine (10.4%). The use of insecticide treated nets (26.6%), insecticide spray (25.3%), as well as, nets on windows and doors (15.8%) were reported as the major ways of controlling mosquito bites at home. The management of malaria among respondents is commendable; notwithstanding, healthcare professionals will need a combination of new approaches and tools in effective management of malaria.

Effect of grain excavation damages by Sitophilus granarius on the efficacy of grain protectant insecticides against Cryptolestes ferrugineus and Tribolium castaneum

Internally feeding primary pests produce dusty frass that is known to support the development of externally developing beetles. Apart from frass, primary pests create semi-opened cavities in kernels that provide an opportunity for hiding and feeding of secondary pests, increase grain surface area and decrease weight of excavated kernels. It is unknown whether the excavated kernels may affect the efficacy of grain protectants and the development of secondary pests. Therefore, this study explored insecticide droplet distribution on the surface of excavated kernels by Sitophilus granarius. Further, it evaluated the effect of grain mixtures - differing in various proportions of sound and excavated kernels without frass - on the development and efficacy of two different doses of grain protectant insecticides (pirimiphos-methyl and deltamethrin) in sensitive strains of Cryptolestes ferrugineus and Tribolium castaneum. It was found - using dyed insecticide spray - that half of kernels did not receive droplets inside the excavations. Bioassays revealed that (i) the adult survival and progeny production of C. ferrugineus and T. castaneum were recorded only on mixtures with a high proportion of excavated kernels; (ii) the higher dose of pirimiphos-methyl and deltamethrin led to 100% mortality in both pests under all conditions; and (iii) the lower dose enabled survival on grain mixtures with an increased ratio of excavated to sound kernels in both chemicals and secondary pest species. The work first showed that a high proportion of damaged kernels in a grain batch/sample can support the development of C. ferrugineus and T. castaneum even without the presence of frass and that excavated kernels may cause pest survival in the case of a lower concentration of grain protectants.

Evaluation of the Effectiveness of Chemical Control for Chagas Disease Vectors in Loja Province, Ecuador.

The objective of this study was to evaluate the effectiveness of selective and community-wide house insecticide spraying in controlling triatomines in the subtropical areas of Loja Province, Ecuador. We designed a quasi-experimental pre–post-test without a control group to compare entomological levels before and after spraying. The baseline study was conducted in 2008. Second, third, and fourth visits were conducted in 2010, 2011, and 2012 in three rural communities. Out of the 130 domestic units (DU) visited, 41 domestic units were examined in each of the four visits. Selective and community-wide insecticide interventions included spraying with 5% deltamethrin at 25 mg/m2 active ingredient. At each visit, a questionnaire was administered to identify the characteristics of households, and DUs were searched for triatomine bugs. In addition, parasitological analysis was carried out in life triatomines. One and two rounds of selective insecticide spraying decreased the probability of infestation by 62% (pairwise odds ratios [POR] 0.38, 95% confidence interval [CI] 0.17–0.89, p = 0.024) and 51% (POR 0.49, 95% CI 0.23–1.01, p = 0.054), respectively. A similar effect was observed after one round of community-wide insecticide application in Chaquizhca and Guara (POR 0.55, CI 0.24–1.25, p = 0.155) and Bellamaria (POR 0.62, CI 0.22–1.79, p = 0.379); however, it was not statistically significant. Trypanosoma cruzi infection in triatomines (n = 483) increased overtime, from 2008 (42.9% and 8.5% for Rhodnius ecuadoriensis and Panstrongylus chinai, respectively) to 2012 (79.5% and 100%). Neither of the two spraying methodologies was effective for triatomine control in this area and our results point to a high likelihood of reinfestation after insecticide application. This underscores the importance of the implementation of physical barriers that prevent invasion and colonization of triatomines in households, such as home improvement initiatives, accompanied by a concerted effort to address the underlying socioeconomic issues that keep this population at risk of developing Chagas disease.