Bionomics of Anopheles culicifacies Sensu Lato in two Malaria Endemic Districts of Central Gujarat, India

Background: Gujarat State has been witnessing large scale urbanization, in last two decades, resulting changes in local environment and microclimate may have also influenced the resting, feeding habits and development of Anopheles cu­licifacies sensu 1ato. Therefore, a systematic longitudinal study was undertaken to know the bionomics of An. culicifa­cies s.l. in present study. Methods: The study was conducted in four sentinel villages in Kheda and Panchmahal Districts. The mosquitoes rest­ing indoors and outdoors were collected in early morning hours, using mouth aspirator, pyrethrum space spray and light traps. Mosquito landing collections on human volunteers was carried out from dusk to dawn. Species composition, abundance, seasonal prevalence, resting behavior (Endophily and Exophily), sibling species composition, vector poten­tial and insecticide susceptibility status of malaria vectors was studied. Results: Six Anopheles species were collected, An. subpictus s.l. was the predominant species followed by An. culicifa­cies s.l., a known malaria vector was resting indoor and zoophagic behaviour. Anopheles culicifacies, sibling species B (89%) was found. The sporozoite rate (%) and entomological inoculation rate in Kheda was 2.33%, 3.09 per bite/ per­son/annum and they were 1.05% and 0.475 bite/person/annum in Panchmahal, respectively. Anopheles culicifa­cies s.l. was found possible resistance to alpha-cypermethrin. Conclusion: Anopheles culicifacies s.l. showed endophillic, zoophagic behaviour and found possible resistance to al­pha-cypermethrin. Early biting behaviour of An. culicifacies s.l. in this area is a cause of concern. Therefore, there is need for frequent monitoring and evaluation of vector control measures in order to achieve the elimination target of ma­laria in this area.

Multi-country evaluation of the durability of pyrethroid plus piperonyl-butoxide insecticide-treated nets: study protocol

BACKGROUND

Mass distributions of long-lasting insecticidal nets (LLINs) have contributed to large reductions in the malaria burden. However, this success is in jeopardy due in part to the increasing pyrethroid-resistant mosquito population as well as low LLINs coverage in various areas because the lifespan of LLINs is often shorter than the interval between replenishment campaigns. New insecticide-treated nets (ITNs) containing pyrethroid and piperonyl-butoxide (PBO) have shown a greater reduction in the incidence of malaria than pyrethroid LLINs in areas with pyrethroid-resistant mosquitoes. However, the durability (attrition, bio-efficacy, physical integrity and chemical retainment) of pyrethroid-PBO ITNs under operational settings has not been fully characterized. This study will measure the durability of pyrethroid-PBO ITNs to assess whether they meet the World Health Organization (WHO) three years of operational performance criteria required to be categorized as "long-lasting".

METHODS

A prospective household randomized controlled trial will be conducted simultaneously in Tanzania, India and Côte d'Ivoire to estimate the field durability of three pyrethroid-PBO ITNs (Veeralin®, Tsara® Boost, and Olyset® Plus) compared to a pyrethroid LLIN: MAGNet®. Durability monitoring will be conducted up to 36 months post-distribution and median survival in months will be calculated. The proportion of ITNs: (1) lost (attrition), (2) physical integrity, (3) resistance to damage score, (4) meeting WHO bio-efficacy (≥ 95% knockdown after 1 h or ≥ 80% mortality after 24 h for WHO cone bioassay, or ≥ 90% blood-feeding inhibition or ≥ 80% mortality after 24 h for WHO Tunnel tests) criteria against laboratory-reared resistant and susceptible mosquitoes, and insecticidal persistence over time will be estimated. The non-inferiority of Veeralin® and Tsara® Boost to the first-in-class, Olyset® Plus will additionally be assessed for mortality, and the equivalence of 20 times washed ITNs compared to field aged ITNs will be assessed for mortality and blood-feeding inhibition endpoints in the Ifakara Ambient Chamber Test, Tanzania.

CONCLUSION

This will be the first large-scale prospective household randomized controlled trial of pyrethroid-PBO ITNs in three different countries in East Africa, West Africa and South Asia, simultaneously. The study will generate information on the replenishment intervals for PBO nets.

Linkages between malaria and malnutrition in co-endemic regions of India

INTRODUCTION

Malaria and malnutrition are key public health challenges in India. However, the relationship between them is poorly understood. Here, we aimed to elucidate the potential interactions between the two health conditions by identifying the areas of their spatial overlap.

METHODS

We have analysed the district-wise undernutrition and malaria data of 638 districts of India across 28 states and 8 union territories. Data on malnutrition parameters viz. stunting, wasting, underweight and anaemia, sourced from the fourth National Family Health Survey (2015-2016), and malaria Annual Parasite Index (API) data of the same year (i.e, 2015), sourced from National Center of Vector Borne Diseases Control were analysed using local Moran's I Index and logistic regression.

RESULTS

Among all the malnutrition parameters, we found underweight in children and anaemia in men to co-occur with malaria in the districts of Chhattisgarh, Jharkhand, Madhya Pradesh and Odisha. Further, districts with more than 36% underweight children (OR (95% CI): 2.31 (1.53 to 3.48)) and/or more than 23.6% male population with anaemia (OR (95% CI): 2.06 (1.37 to 3.11)) had higher odds of being malaria endemic districts (ie, Annual Parasite Index >1).

CONCLUSION

Malaria and malnutrition co-occur in the malaria-endemic parts of India. The high prevalence of undernutrition in children and anaemia among men may contribute to malaria endemicity in a particular region. Therefore, future research should be prioritised to generate data on the individual level. Further, malaria control interventions could be tailored to integrate nutrition programmes to disrupt indigenous malaria transmission in endemic districts.

Tracking district-level performance in the context of achieving zero indigenous case status by 2027

India has committed to zero indigenous malaria cases by 2027 and elimination by 2030. Of 28 states and 8 union territories of India, eleven states were targeted to reach the elimination phase by 2020. However, state-level epidemiology indicates that several states of India may not be on the optimum track, and few goals set in National Framework for Malaria Elimination (NFME) for 2020 remain to be addressed. Therefore, tracking the current progress of malaria elimination in India at the district level, and identifying districts that are off track is important in understanding possible shortfalls to malaria elimination. Annual malaria case data from 2017-20 of 686 districts of India were obtained from the National Center for Vector-Borne Diseases Control (NCVBDC) and analysed to evaluate the performance of districts to achieve zero case status by 2027. A district's performance was evaluated by calculating the annual percentage change in the total number of malaria cases for the years 2018, 2019 and 2020 considering the previous year as a base year. The mean, median and maximum of these annual changes were then used to project the number of malaria cases in 2027. Based on these, districts were classified into four groups: 1) districts that are expected to reach zero case status by 2027, 2) districts that would achieve zero case status between 2028 and 2030, 3) districts that would arrive at zero case status after 2030, and 4) districts where malaria cases are on the rise. Analysis suggest, a cohort of fifteen districts require urgent modification or improvement in their malaria control strategies by identifying foci of infection and customizing interventions. They may also require new interventional tools that are being developed recently so that malaria case reduction over the years may be increased.

Vaccination coverage and breakthrough infections of COVID-19 during the second wave among staff of selected medical institutions in India

India experienced the second wave of SARS-CoV-2 infection from April 3 to June 10, 2021. During the second wave, Delta variant B.1617.2 emerged as the predominant strain, spiking cases from 12.5 million to 29.3 million (cumulative) by the end of the surge in India. Vaccines against COVID-19 are a potent tool to control and end the pandemic in addition to other control measures. India rolled out its vaccination programme on January 16, 2021, initially with two vaccines that were given emergency authorization-Covaxin (BBV152) and Covishield (ChAdOx1 nCoV- 19). Vaccination was initially started for the elderly (60+) and front-line workers and then gradually opened to different age groups. The second wave hit when vaccination was picking up pace in India. There were instances of vaccinated people (fully and partially) getting infected, and reinfections were also reported. We undertook a survey of staff (front line health care workers and supporting) of 15 medical colleges and research institutes across India to assess the vaccination coverage, incidence of breakthrough infections, and reinfections among them from June 2 to July 10, 2021. A total of 1876 staff participated, and 1484 forms were selected for analysis after removing duplicates and erroneous entries (n = 392). We found that among the respondents at the time of response, 17.6% were unvaccinated, 19.8% were partially vaccinated (received the first dose), and 62.5% were fully vaccinated (received both doses). Incidence of breakthrough infections was 8.7% among the 801 individuals (70/801) tested at least 14 days after the 2nd dose of vaccine. Eight participants reported reinfection in the overall infected group and reinfection incidence rate was 5.1%. Out of (N = 349) infected individuals 243 (69.6%) were unvaccinated and 106 (30.3%) were vaccinated. Our findings reveal the protective effect of vaccination and its role as an essential tool in the struggle against this pandemic.

Insecticide resistance status of malaria vectors in the malaria endemic states of India: implications and way forward for malaria elimination

Background

In 2012, the World Health Organization (WHO) released the Global Plan for Insecticide Resistance Management in malaria vectors to stress the need to address insecticide resistance. In a prospective multi-centric study commissioned by the Indian Council of Medical Research (ICMR), we assessed the insecticide susceptibility status of the primary malaria vectors in India from 2017 through 2019.

Methods

The insecticide susceptibility status of the prevalent primary malaria vectors - An. culicifacies, An. fluviatilis, An. stephensi, An. minimus and An. baimaii and secondary malaria vectors - An. aconitus, An. annularis and An. philippinensis/nivepes from 328 villages in 79 districts of 15 states of India were assessed following the WHO method mainly to insecticides used in vector control, organochlorine (DDT), organophosphate (malathion), and other pyrethroids (alpha-cypermethrin, cyfluthrin, lambda-cyhalothrin and permethrin). The study sites were selected as suggested by the National Vector Borne Disease Control Programme.

Results

The primary malaria vector An. culicifacies showed resistance to DDT (50/50 districts including two districts of Northeastern India), malathion (27/44 districts), and deltamethrin (17/44 districts). This species was resistant to DDT alone in 19 districts, double resistant to DDT-malathion in 16 districts, double resistant to DDT-deltamethrin in 6 districts, and triple resistant to DDT-malathion-deltamethrin in 9 districts. An. minimus and An. baimaii were susceptible in Northeastern India while An. fluviatilis and the secondary malaria vector An. annularis was resistant to DDT in Jharkhand.

Conclusion

In this study we report that among the primary vectors An. culicifacies is predominantly resistant to multiple insecticides. Our data suggest that periodic monitoring of insecticide susceptibility is vital. The national malaria program can take proactive steps for insecticide resistance management to continue its push toward malaria elimination in India.

Challenges in Understanding the Bionomics of Indian Malaria Vectors

Many factors influence the success or failure of malaria vector control program such as political will, leadership, sustained funding, robustness of healthcare system and others. In addition, updated knowledge and information about the triad of host, parasite, and vector is of paramount importance. Vector bionomics studies that determine mosquito behavior in terms of feeding, resting, biting, mating, breeding, longevity, vectorial capacity, and response to different insecticides are a step towards enhancing our understanding. In the present work, we have compiled studies conducted in India over the past two decades (2000-2020) to identify gaps in our knowledge of malaria vector bionomics and the research that needs to be done in the future. We retrieved district-level data of India's six primary malaria vector species. According to our findings, vector bionomics studies have been undertaken in ∼50% and ∼15% of the country's high (annual parasite index > 1) and low (annual parasite index < 1) malaria-endemic districts respectively. Most of the research studies focused on mosquito density, insecticide susceptibility status, and parasite detection, whereas other vital bionomics parameters were neglected. Surveys conducted were incomplete, and vector bionomics data were not captured sufficiently. The absence of vector bionomics data can be a blind spot and the lack or inadequate understanding of vector bionomics can lead to use of inappropriate vector control tools. Thus, there is an urgent need to initiate comprehensive bionomics studies on India's primary and secondary malaria vectors.

India may need an additional metric to assess the endemicity of malaria in low surveillance districts

India's National Framework for malaria elimination is essentially dependent on Annual Parasite Incidence (API). API is the primary criterion for classifying states and districts into different categories: intensified control, pre-elimination, elimination, prevention and re-establishment of malaria. However, API's validity is critically dependent on multiple factors, one such important factor is Annual Blood Examination Rate (ABER) and is often considered as indicator of operational efficiency. Therefore, the present study aimed to determine whether the API is a sufficiently good malaria index to assess malaria endemicity in India. An in-depth analysis of malaria data (2017-19) was done to determine the appropriateness of API as a sole indicator of malaria endemicity. We stratified the Indian districts into three strata based on Annual Blood Examination Rate (ABER): <5, 5.0-5.0, >15, further APIs was compared with Slide Positivity Rates (SPRs) using sign rank test, independently in each stratum. API and SPR were found comparable (p-value 0.323) in stratum 2 only. However, in the case of lower ABER (<5%, strata 1), the API was significantly lower than the SPR, and higher ABER (>15%), the API was found substantially higher than the SPR. Thus, ABER tunes the validity of API and should avoid to use as a single indicator of malaria endemicity. API is an appropriate measure of malaria endemicity in high and moderate transmission areas where surveillance is good (ABER≥5%). However, it is vitally dependent upon surveillance rate and other factors such as population size, the selection of individuals for malaria testing. Therefore, where surveillance is poor (<5%), we propose that API should be complemented with SPR and the number of cases. It will significantly aid the design and deployment of interventions in India.

Diverse Malaria Presentations across National Institutes of Health South Asia International Center for Excellence in Malaria Research Sites in India

The Malaria Evolution in South Asia (MESA) International Center for Excellence in Malaria Research (ICEMR) was established by the US National Institutes of Health (US NIH) as one of 10 malaria research centers in endemic countries. In 10 years of hospital-based and field-based work in India, the MESA-ICEMR has documented the changing epidemiology and transmission of malaria in four different parts of India. Malaria Evolution in South Asia-ICEMR activities, in collaboration with Indian partners, are carried out in the broad thematic areas of malaria case surveillance, vector biology and transmission, antimalarial resistance, pathogenesis, and host response. The program integrates insights from surveillance and field studies with novel basic science studies. This is a two-pronged approach determining the biology behind the disease patterns seen in the field, and generating new relevant biological questions about malaria to be tested in the field. Malaria Evolution in South Asia-ICEMR activities inform local and international stakeholders on the current status of malaria transmission in select parts of South Asia including updates on regional vectors of transmission of local parasites. The community surveys and new laboratory tools help monitor ongoing efforts to control and eliminate malaria in key regions of South Asia including the state of evolving antimalarial resistance in different parts of India, new host biomarkers of recent infection, and molecular markers of pathogenesis from uncomplicated and severe malaria.

Structural insights for neutralization of Omicron variants BA.1, BA.2, BA.4, and BA.5 by a broadly neutralizing SARS-CoV-2 antibody

In this study, by characterizing several human monoclonal antibodies (mAbs) isolated from single B cells of the COVID-19–recovered individuals in India who experienced ancestral Wuhan strain (WA.1) of SARS-CoV-2 during early stages of the pandemic, we found a receptor binding domain (RBD)–specific mAb 002-S21F2 that has rare gene usage and potently neutralized live viral isolates of SARS-CoV-2 variants including Alpha, Beta, Gamma, Delta, and Omicron sublineages (BA.1, BA.2, BA.2.12.1, BA.4, and BA.5) with IC 50 ranging from 0.02 to 0.13 μg/ml. Structural studies of 002-S21F2 in complex with spike trimers of Omicron and WA.1 showed that it targets a conformationally conserved epitope on the outer face of RBD (class 3 surface) outside the ACE2-binding motif, thereby providing a mechanistic insights for its broad neutralization activity. The discovery of 002-S21F2 and the broadly neutralizing epitope it targets have timely implications for developing a broad range of therapeutic and vaccine interventions against SARS-CoV-2 variants including Omicron sublineages.

India could harness public-private partnerships to achieve malaria elimination

Public-private partnerships (PPP) have been beneficial in different sectors like infrastructure development and service sector across the world, including in India. Such partnerships in the healthcare sector have also been successful in providing access to affordable medical attention to all sections of society. These partnerships between public and private entities have proven to be beneficial in controlling malaria in high burden districts of India and taking these areas to the brink of elimination, thus setting examples to follow. The two successful ones are the Comprehensive Case Management Project (CCMP) in Odisha which is now adopted by the state, and the Malaria Elimination Demonstration Project (MEDP) which has nearly eliminated malaria from the highly endemic district of Mandla in Madhya Pradesh. Here we propose that non-government and semi-government actors may be given vital roles in the malaria elimination efforts till 2030 and beyond. These partners will add value to the national programme and may have the potential to develop and test different models of malaria elimination in real-life settings that the government programme can absorb sustainably.

Scrub typhus in urban areas of Wardha district in central India

Background & objectives

Scrub typhus caused by Orientia tsutsugamushi presents as acute undifferentiated fever and can be confused with other infectious causes of fever. We studied scrub typhus as part of a study on hospital-based surveillance of zoonotic and vector-borne zoonotic diseases at a tertiary care hospital located in the Wardha district, Maharashtra, India. We report here descriptive epidemiology and climatic factors affecting scrub typhus.

Methods

Patients of any age and sex with fever of ≥5 days were enrolled for this study. Data on sociodemographic variables were collected by personal interviews. Blood samples were tested by IgM ELISA to diagnose scrub typhus. Confirmation of scrub typhus was done by indirect immunofluorescence assay for IgM (IgM IFA). The climatic determinants were determined using time-series Poisson regression analysis.

Results

It was found that 15.9 per cent of the study participants were positive for scrub typhus by IgM ELISA and IgM IFA, both. Positivity was maximum (23.0%) in 41-60 yr of age and more females were affected than males (16.6 vs. 15.5%). Farmworkers were affected more (23.6%) than non-farm workers (12.9%). The disease positivity was found to be high in monsoon and post-monsoon seasons (22.9 and 19.4%) than in summer and winter.

Interpretation & conclusions

There were three hot spots of scrub typhus in urban areas of Wardha district. Rainfall and relative humidity in the previous month were the significant determinants of the disease.

Studies on the fitness characteristics of wMel- and wAlbB-introgressed Aedes aegypti (Pud) lines in comparison with wMel- and wAlbB-transinfected Aedes aegypti (Aus) and wild-type Aedes aegypti (Pud) lines

Wolbachia, an intracellular maternally transmitted endosymbiont, has been shown to interfere with the replication of dengue virus in Aedes aegypti mosquitoes. The Wolbachia-transinfected Ae. aegypti has been currently released in many countries to test its effectiveness in preventing the transmission of dengue virus. ICMR-Vector Control Research Centre in collaboration with World Mosquito Program Monash University, Australia, has generated two new Wolbachia-introgressed Ae. aegypti Puducherry (Pud) lines via backcrossing Ae. aegypti females of Australian (Aus) strains, infected with wMel and wAlbB Wolbachia with wild-type Ae. aegypti Puducherry (Pud) males. Wolbachia infections are known to induce a fitness cost and confer benefit on the host mosquito populations that will influence spread of the Wolbachia into native wild mosquito populations during the field release. Hence, the induced fitness cost or benefit/advantage in the two newly generated Ae. aegypti (Pud) lines was assessed in the laboratory in comparison with the wild-type Ae. aegypti (Pud) strain. In addition, maternal transmission (MT) efficiency, induced cytoplasmic incompatibility (CI), and insecticide resistance status of the two (Pud) lines were determined to assess the likely frequency of wMel and wAlbB infections in the native wild population after field invasion. The study shows that wMel and wAlbB infections did not induce any fitness cost on the two newly generated (Pud) lines. Rather, in terms of wing length, fecundity, egg hatch rate, and adult survival, the Wolbachia introgression conferred fitness benefits on the (Pud) lines compared to uninfected Wolbachia free wild Ae. aegypti population. wMel and wAlbB exhibited a high maternal transmission (99–100%) and induced nearly complete (98–100%) cytoplasmic incompatibility. Both the (Pud) lines were resistant to deltamethrin, malathion, DDT, and temephos, and the level of resistance was almost the same between the two lines as in the wild type. Overall, the stable association of wMel and wAlbB established with Ae. aegypti and the reproductive advantages of the (Pud) lines encourage a pilot release in the field for population replacement potential.

A note on the insecticide susceptibility status of secondary malaria vector An. annularis in Jharkhand state of India

BACKGROUND & OBJECTIVES

An. annularis van der Wulp (1884) is the secondary malaria vector of importance in India. In Jharkhand state it is present in almost all the districts abundantly and transmits malaria. The development of resistance to Dichlorodipheny ltrichloroethane (DDT) in An. annularis was reported from various parts of India. The main objective of this study was to generate information on insecticide susceptibility status of An. annularis to DDT, malathion, deltamethrin and permethrin in different districts of Jharkhand state. Methods; Adult An. annularis female mosquitoes were collected form villages of six tribal districts Simdega (Kurdeg and Simdega CHC), Khunti (Murhu and Khunti CHCs), Gumla (Bharno and Gumla CHCs), West Singhbhum (Chaibasa and Bada Jamda CHCs), Godda (Poraiyahat and Sunderpahari (CHCs) and Sahibganj (Borio and Rajmahal CHCs). Insecticide susceptibility status was determined by using WHO tube test method against prescribed discriminatory dosages of insecticides, DDT - 4.0%, malathion - 5.0%, deltamethrin - 0.05% and permethrin - 0.75%.

RESULTS

An. annularis was reported resistant to DDT in six districts, possible resistant to malathion in districts Gumla, Khuntiand Sahibganj and susceptible to deltamehrin (98% to100% mortality) and permethrin (100% mortality).

INTERPRETATION & CONCLUSION

An. annularis, the secondary vector species is associated with the transmission of malaria reported resistant to DDT and susceptible to pyrerthroids deltamethrin and permethrin. In view of large-scale distribution of long-lasting insecticidal nets (LLINs) in all the districts, the response to synthetic pyrethroid needs to be periodically monitored to assess the effectiveness.

Malaria control initiatives that have the potential to be gamechangers in India's quest for malaria elimination

Malaria continues to have devastating effect on people's lives especially in developing countries. India is slated for malaria elimination by 2030. Though India has sustained a decline in malaria burden at the national level the epidemiological picture remains heterogenous. India's road to malaria elimination plan is riddled with many roadblocks. Major challenges include insufficient surveillance, slow and aggregated data reporting especially in exigent situations like cross-border areas and vulnerable high-risk groups. More than half of total malaria cases were due to Plasmodium vivax (P. vivax) in India as reported by national malaria control programme in 2019. This translates into substantial burden of P. vivax malaria in absolute numbers. P. vivax malaria, which is difficult to resolve as compared to other species, poses a threat to India's elimination plans by virtue of its tendency to develop hypnozoites, due to poor compliance to primaquine (PQ), due to host factors like G 6 PD deficiency and other genes that affect PQ metabolism. Also, India's malaria endemic areas largely coincide geographically with tribal regions which are poor in healthcare infrastructure. The tribal population disproportionately bears a huge burden of malaria. They also harbour more G6PD deficient individuals than non-tribal regions. Therefore, in addition to inadequate diagnostic facilities (for both malaria and G6PD testing) these remote rural and tribal communities suffer from lack of timely treatment, incomplete radical treatment due to poor compliance and thus repeated episodes of P. vivax due to relapses and/or reinfections. Another challenge is that the the current diagnostic tools in the national programme in India and other countries are mostly available only via the programme and are able to detect patent infections on the whole. These therefore miss low-density infections which are another major limitation for their use in malaria endemic countries. Drug and insecticide resistance need to be constantly monitored as they have direct impact on the efficacy of the current tools. Need for better vector control products for the diverse entomological requirements is also felt. India is the second most populous country in the world with majority of its population at risk of malaria. Despite many agencies (government and non-government) working in the field of malaria, there needs to be more synergy at the local or central level for malaria control. Here, we have proposed solutions for specific facets of the malaria programme. Surveillance, data visualization and analysis can all be supported through over the counter availability of rapid diagnostics, adoption of molecular tools like PCR (requiring additional infrastructure and expertise), mobile applications for data capture and use of malaria data dashboard. Management could be augmented by inclusion of tafenoquine for treatment of P. vivax malaria with a companion point-of care diagnostic which has been developed to assess G6PD enzyme activity. A switchover to artemether-lumefantrine for the entire country can also be considered. Vector control can be strengthened by commercial availability of insecticidal bednets and exploration of novel vector control tools like ivermectin. Lastly, enhancing synergy amongst various stakeholders would also catalyze the malaria elimination plans.

Funding

The authors have received no funding for this paper.

Sensitivity of wMel and wAlbB Wolbachia infections in Aedes aegypti Puducherry (Indian) strains to heat stress during larval development

Background

ICMR-Vector Control Research Centre, Puducherry, India, developed two colonies of Aedes aegypti infected with wMel and wAlbB Wolbacia strains called Ae. aegypti (Pud) lines for dengue control. The sensitivity of wMel and wAlbB strains in Ae. aegypti (Pud) lines to heat stress was studied.

Methods

wMel and wAlbB infected and uninfected Ae. aegypti larvae (first to fourth instars) were reared in the laboratory to adults at 26 °C, 30 °C, 36 °C and 40 °C constant temperatures and also 26–30 °C, 26–36 °C and 26–40 °C diurnal cyclic temperatures. The adults were tested for Wolbachia infection. Experiments were also carried out rearing the larvae under simulated field conditions in summer (April and June) under sunlight using fully open and half open bowls and also under sunlight and natural shade.

Results

At 36 °C and 40 °C constant temperatures, complete larval mortality was observed. At 30 °C and 26 °C, no larval mortality occurred, but Wolbachia density was relatively low in wMel infected males compared to control (maintained at 26 ± 1 °C). At diurnal cyclic temperature of 26–40 °C, Wolbachia density was reduced in males of both the (Pud) lines, but not in females. At 26–36 °C, reduction in Wolbachia density was observed in wMel males but not in wAlbB males. At 26–30 °C, no significant reduction in Wolbachia density was observed with wMel and wAlbB strains. In simulated field conditions (April), under sunlight, the daytime water temperature reached a maximum of 35.7 °C in both full and half open bowls. No larval mortality occurred. Wolbachia frequency and density was reduced in wMel-infected Ae. aegypti (Pud) males from both type of bowls and in females from full open bowls, and in wAlbB males from half open bowls. In June, rearing of larvae under sunlight, the first-instar larvae experienced a maximum daytime water temperature of > 38 °C that caused complete mortality. No larval mortality was observed in bowls kept under shade (< 32 °C).

Conclusions

Exposure of larvae to higher rearing temperatures in the laboratory and simulated-field conditions reduced the densities of wMel and wAlbB strains particularly in males, but the impact was more pronounced for wMel strain. The actual effect of heat stress on the stability of these two Wolbachia strains needs to be tested under natural field conditions.

Graphical Abstract

What India can learn from globally successful malaria elimination programmes

India is targeting malaria elimination by 2030. Understanding and adopting the strategies employed by countries that have successfully eliminated malaria can serve as a crucial thrust in this direction for a geographically diverse country like India. This analysis is based on extensive literature search on malaria elimination policies, strategies and programmes adopted by nine countries (China, El Salvador, Algeria, Argentina, Uzbekistan, Paraguay, Sri Lanka, Maldives and Armenia) which have attained malaria-free status over the past decade. The key points which India can learn from their journey are mandatory time-bound response in the form of case reporting and management, rapid vector control response, continuous epidemiological and entomological surveillance, elevated community participation, more training and capacity building, private sector involvement, use of quality diagnostics, cross-border collaborations, inclusion of prevention of re-establishment programmes into the elimination plans, higher investment in research, and uninterrupted funds for successful implementation of malaria elimination programmes. These learnings would help India and other South Asian countries steer their programmes by devising tailor-made strategies for their own regions.

Rickettsiae in fleas infesting domestic pets of eastern Himalayan terrains of India

Background

Flea-borne rickettsioses have been limitedly explored in the Indian sub-Himalayan belt, including the North Eastern Region (NER) of India. This study investigates the presence of rickettsiae hosts and their probable pathogens in the disease-endemic hilly state of the NER of India.

Methods

Entomological surveys were carried out in disease-reporting localities in a hilly state in India. Fleas collected from domesticated animals were processed for detection of a Rickettsia-specific 17-kDa gene.

Results

Sequence analysis revealed Rickettsia felis in six flea pools (40%), Candidatus Rickettsia senegalensis in two pools (13.3%) and Rickettsia asembonensis in one pool (6.6%).

Conclusions

Our findings suggest Ctenocephalides felis, Ctenocephalides canis and Pulex irritans as potential carriers of R. felis and R. felis–like organisms in India.

Polymerase Chain Reaction-Based Malaria Diagnosis Can Be Increasingly Adopted during Current Phase of Malaria Elimination in India

Despite commendable progress in control of malaria in India and other countries, there are hidden reservoirs of parasites in human hosts that continually feed malaria transmission. Submicroscopic infections are a significant proportion in low-endemic settings like India, and these infections possess transmission potential. Hence, these reservoirs of infection add to the existing roadblocks for malaria elimination. It is crucial that this submerged burden of malaria is detected and treated to curtail further transmission. The currently used diagnostic tools, including the so-called "gold standard" microscopy, are incapable of detecting these submicroscopic infections and thus are suboptimal. It is an opportune time to usher in more sensitive molecular tools like polymerase chain reaction (PCR) for routine diagnosis at all levels of healthcare as an additional diagnostic tool in routine settings. PCR assays have been developed into user-friendly formats for field diagnostics and are near-point-of-collection. Because of the COVID-19 pandemic in India, these are being used rampantly across the country. The facilities created for COVID-19 diagnosis can easily be co-opted and harnessed for malaria diagnosis to augment surveillance by the inclusion of molecular techniques like PCR in the routine national malaria control program.

Active Engagement of Private Healthcare Providers Is Needed to Propel Malaria Elimination in India

Malaria is a major public health concern in India. Despite a remarkable decline in overall malaria cases and deaths over the past several years, the caseload is still substantial. India's commitment towards malaria elimination by 2030 requires several additional measures for its achievement. The country's malaria data are collated from the public health sector only by the aggregated paper-based surveillance system, which is considered weak because it captures only a minuscule percentage (8% as per the World Malaria Report 2017). The absence of private-sector data is a serious caveat in India's malaria epidemiological scenario. The private healthcare sector (trained and untrained) is a major provider to communities in malaria-endemic areas. It is increasingly recognized that the involvement of the private healthcare sector is crucial for understanding the complete epidemiological picture and targeting elimination strategies accordingly as is being done for tuberculosis in India. Active involvement and alignment of the private sector to the government program of the private sector can be fostered by assessing the presence of the private healthcare sector via landscaping exercise, establishing linkages between the two sectors, incentivization, and encouraging reporting via user-friendly online and offline systems. There are challenges and barriers to the successful adoption of the private healthcare providers in the fold of the national malaria control program; at the same time, it is a critical step that will propel malaria elimination plans of India.

India Needs to Consider Planning a Change to Artemether-Lumefantrine to Treat Plasmodium falciparum Malaria

As the malaria elimination target draws closer for India, it must be ensured that the country's policies, strategies, and tools remain effective. Artemisinin-based combination therapies are the mainstay of Plasmodium falciparum malaria management. India has a differential standard therapy for uncomplicated falciparum malaria in the form of artemether-lumefantrine in its northeastern states and artesunate + sulfadoxine-pyrimethamine in the rest of the country. The clinical failure of artesunate + sulfadoxine-pyrimethamine in the northeast regions were attributed primarily to parasite resistance resulting from mutations in the enzymes dihydropteroate synthase and dihydrofolate reductase. Artemether-lumefantrine was therefore substituted for artesunate + sulfadoxine-pyrimethamine in the region. The change has been a success, as evidenced by the therapeutic efficacy studies conducted at regular intervals in India. However, studies suggest that resistance may be emerging toward sulfadoxine-pyrimethamine in multiple parts of the nation. Hence, there is a possibility that the artesunate + sulfadoxine-pyrimethamine combination may be acting in part as a monotherapy, and this makes the longevity of the artesunate + sulfadoxine-pyrimethamine drug combination therapy uncertain. The increasing presence of drug-resistant mutants in P. falciparum dhps and dhfr genes suggests the need for a policy switch for uncomplicated P. falciparum malaria from artesunate + sulfadoxine-pyrimethamine to artemether-lumefantrine.

Ivermectin as an endectocide may boost control of malaria vectors in India and contribute to elimination

Malaria constitutes one of the largest public health burdens faced by humanity. Malaria control has to be an efficient balance between diagnosis, treatment and vector control strategies. The World Health Organization currently recommends indoor residual spraying and impregnated bed nets as two malaria vector control methods that have shown robust and persistent results against endophilic and anthropophilic mosquito species. The Indian government launched the National Framework for Malaria Elimination in 2016 with the aim to achieve the elimination of malaria in a phased and strategic manner and to sustain a nation-wide malaria-free status by 2030. India is currently in a crucial phase of malaria elimination and novel vector control strategies maybe helpful in dealing with various challenges, such as vector behavioural adaptations and increasing insecticide resistance among the Anopheles populations of India. Ivermectin can be one such new tool as it is the first endectocide to be approved in both animals and humans. Trials of ivermectin have been conducted in endemic areas of Africa with promising results. In this review, we assess available data on ivermectin as an endectocide and propose that this endectocide should be explored as a vector control tool for malaria in India.