Observations on sporozoite detection in naturally infected sibling species of the Anopheles culicifacies complex and variant of Anopheles stephensi in India

Mosquito prevalence, resting habitat preference, and Plasmodium infection status of anophelines in coastal Karnataka during the declining phase of malaria-an exploratory study

Malaria has a historical presence in the Dakshina Kannada (D.K.) and Udupi districts of Karnataka, India. To understand the potential involvement of anopheline fauna in malaria transmission, we conducted an exploratory entomological survey. The study is crucial given the decreasing malaria incidence in these districts in recent years. From September 2022 to August 2023, we collected indoor resting mosquitoes using a manual aspirator at 27 randomly chosen sites within three distinct resting habitats (human dwellings, cattle sheds, and construction sites) in the urban areas of Udupi and Dakshina Kannada districts. Mosquitoes were morphologically identified, and anopheline specimens were tested for the presence of malarial parasite by polymerase chain reaction (PCR) analysis. We collected a total of 1810 mosquitoes, comprising 21 species distributed across five genera. Culex emerged as the predominant genus, constituting 84.4% of the collected specimens, while Anopheles accounted for 5.4%. Among the observed species, Culex quinquefasciatus was predominant, comprising 77.9% of the mosquito specimens collected in this study. Two malaria vectors, An. stephensi and An. subpictus complex, constituted 16.3% and 1.0% of the total anophelines collected, respectively. None of the 96 female anophelines was tested positive for Plasmodium infection. Our findings suggest that Anopheles mosquitoes prefer resting in cattle sheds over human dwellings. While our study identified two malaria vectors, they were present at low densities. To gain a more comprehensive understanding of the dynamics of these vector mosquitoes, it is essential to conduct long-term surveillance to monitor their prevalence and role in malaria transmission.

Odorant Binding Proteins (OBPs) and Odorant Receptors (ORs) of Anopheles stephensi: Identification and comparative insights

Anopheles stephensi is an important vector of malaria in the South Asia, the Middle East, and Eastern Africa. The olfactory system of An. stephensi plays an important role in host-seeking, oviposition, and feeding. Odorant binding proteins (OBPs) are globular proteins that play a pivotal role in insect olfaction by transporting semiochemicals through the sensillum lymph to odorant receptors (ORs). Custom motifs designed from annotated OBPs of Aedes aegypti, Drosophila melanogaster, and Anopheles gambiae were used for the identification of putative OBPs from protein sequences of the An. stephensi Indian strain. Further, BLASTp was also performed to identify missing OBPs and ORs. Subsequently, the presence of domains common to OBPs was confirmed. Identified OBPs were further classified into three sub-classes. Phylogenetic and syntenic analyses were carried out to find homology, and thus the evolutionary relationship between An. stephensi OBPs and ORs with those of An. gambiae, Ae. aegypti and D. melanogaster. Gene structure and physicochemical properties of the OBPs and ORs were also predicted. A total of 44 OBPs and 45 ORs were predicted from the protein sequences of An. stephensi. OBPs were further classified into the classic (27), atypical (10) and plus-C (7) OBP subclasses. The phylogeny revealed close relationship of An. stephensi OBPs and ORs with An. gambiae homologs whereas only five OBPs and two ORs of An. stephensi were related to Ae. aegypti OBPs and ORs, respectively. However, D. melanogaster OBPs and ORs were distantly rooted. Synteny analyses showed the presence of collinear block between the OBPs and ORs of An. stephensi and An. gambiae as well as Ae. aegypti’s. No homology was found with D. melanogaster OBPs and ORs. As an important component of the olfactory system, correctly identifying a species’ OBPs and ORs provide a valuable resource for downstream translational research that will ultimately aim to better control the malaria vector An. stephensi.

Plasmodium vivax liver stage assay platforms using Indian clinical isolates

Background

Vivax malaria is associated with significant morbidity and economic loss, and constitutes the bulk of malaria cases in large parts of Asia and South America as well as recent case reports in Africa. The widespread prevalence of vivax is a challenge to global malaria elimination programmes. Vivax malaria control is particularly challenged by existence of dormant liver stage forms that are difficult to treat and are responsible for multiple relapses, growing drug resistance to the asexual blood stages and host-genetic factors that preclude use of specific drugs like primaquine capable of targeting Plasmodium vivax liver stages. Despite an obligatory liver-stage in the Plasmodium life cycle, both the difficulty in obtaining P. vivax sporozoites and the limited availability of robust host cell models permissive to P. vivax infection are responsible for the limited knowledge of hypnozoite formation biology and relapse mechanisms, as well as the limited capability to do drug screening. Although India accounts for about half of vivax malaria cases world-wide, very little is known about the vivax liver stage forms in the context of Indian clinical isolates.

Methods

To address this, methods were established to obtain infective P. vivax sporozoites from an endemic region in India and multiple assay platforms set up to detect and characterize vivax liver stage forms. Different hepatoma cell lines, including the widely used HCO4 cells, primary human hepatocytes as well as hepatocytes obtained from iPSC’s generated from vivax patients and healthy donors were tested for infectivity with P. vivax sporozoites.

Results

Both large and small forms of vivax liver stage are detected in these assays, although the infectivity obtained in these platforms are low.

Conclusions

This study provides a proof of concept for detecting liver stage P. vivax and provide the first characterization of P. vivax liver stage forms from an endemic region in India.

Indigenously developed digital handheld Android-based Geographic Information System (GIS)-tagged tablets (TABs) in malaria elimination programme in Mangaluru city, Karnataka, India

BACKGROUND

Under-reporting, delayed diagnosis, incomplete treatment and inadequate vector management are few among many factors responsible for uninterrupted transmission of malaria in India. Information technology (IT) and mobile apps can be utilized effectively to overcome these hurdles. Indigenously developed digital handheld geographic information system (GIS)-tagged Android-based tablets (TABs) has been designed especially for implementation of digitization protocol. This has changed the effectiveness of malaria surveillance and intervention strategies in a malaria endemic area of Mangaluru city, Karnataka, India.

METHODS

A software was developed and implemented for control measures to create a digital database of each malaria case. Secondary data analyses were carried out to determine and compare differences in malariometric indices between pre- and post-digitization years. With the introduction of this software active surveillance, information education and communication (IEC), and anti-vector measures were made 'incidence-centric'. This means that the entire control measures were carried out in the houses where the malaria cases (index cases) were reported and also in surrounding houses.

RESULTS

Annual blood examination rate (ABER) increased from 13.82 to 32.8%. Prompt reporting of new cases had improved (36% within 24 h and 80% within 72 h). Complete treatment and parasite clearance time were documented in 98% of cases. In the second post-digitization year untraceable cases reduced from 11.3 to 2.7%; contact blood smears collection also increased significantly (p < 0.001); Slide Positivity Rate (SPR) decreased from 15.5 to 10.48%; malaria cases reduced by 30%.

CONCLUSIONS

IT is very useful in translation of digitized surveillance to core interventions thereby effectively reduce incidence of malaria. This technology can be used effectively to translate smart surveillance to core interventions following the '1-3-7-14' strategy.

Speculation on the possibility for introducing Anopheles stephensi as a species complex: preliminary evidence based on odorant binding protein 1 intron I sequence

BACKGROUND

Anopheles stephensi is considered an important malaria vector in Iran, Asia, and recently in the Horn of Africa. Recently, Ansteobp1 intron I sequence has been introduced a new molecular marker for identification of its biological forms including, mysorensis, intermediate and type, using insectary colony specimens.

METHODS

In the current study, new marker ability in molecular identification of biological forms has been evaluated with An. stephensi specimens collected from Iran and Afghanistan malarious provinces. Following DNA extraction and PCR amplification, sequence analysis and constructed phylogenetic tree revealed that type and intermediate forms are distributed in Iran.

RESULTS

The specimens collected from Afghanistan identified as intermediate and mysorensis forms. Therefore, intermediate form is sympatric species in both countries. Based on the results of Ansteobp1 intron I sequences, An. stephensi could be suggested as new Anopheles complex species including An. stephensi sibling A (type form), An. stephensi sibling B (intermediate form) and An. stephensi sibling C (mysorensis form). This is the first report on the presence of An. stephensi biological forms in Afghanistan.

CONCLUSIONS

Iran is going to eliminate malaria transmission from the country, precise species identification, especially in complex species will be helpful in the prevention of malaria resurgence in the country, mainly because of common fauna of Anopheles species and through border malaria and population movement within Afghanistan, Pakistan, and Iran.

Malaria prevalence in Mangaluru city area in the southwestern coastal region of India

Background

Malaria is highly prevalent in many parts of India and the Indian subcontinent. Mangaluru, a city in the southwest coastal region of Karnataka state in India, and surrounding areas are malaria endemic with 10–12 annual parasite index. Despite high endemicity, to-date, very little has been reported on the epidemiology and burden of malaria in this area.

Methods

A cross-sectional surveillance of malaria cases was performed among 900 febrile symptomatic native people (long-time residents) and immigrant labourers (temporary residents) living in Mangaluru city area. During each of dry, rainy, and end of rainy season, blood samples from a group of 300 randomly selected symptomatic people were screened for malaria infection. Data on socio-demographic, literacy, knowledge of malaria, and treatment-seeking behaviour were collected to understand the socio-demographic contributions to malaria menace in this region.

Results

Malaria is prevalent in Mangaluru region throughout the year and Plasmodium vivax is predominant species compared to Plasmodium falciparum. The infection frequency was found to be high during rainy season. Infections were markedly higher in males than females, and in adults aged 16–45 years than both younger and older age groups. Also, malaria incidence was high among immigrants compared to native population. In both groups, infection rate was directly correlated with their literacy level, knowledge on malaria, dwelling environment, and protective measures used. There was also a significant difference in treatment-seeking behaviour between these two groups.

Conclusions

Malaria incidences in Mangaluru region are predominantly localized to certain hotspot areas within the city, where socioeconomically underprivileged and immigrant labourers are densely populated. These areas have inadequate sanitation and constant water stagnation, harbouring high vector density and contributing to high infection incidences. Additionally, people in these areas seldom practice preventive measures such as using bed nets. The high incidences of malaria in adults are due to minimal cloth wearing, and long working hours stretching to late evenings in places with high vector density. Instituting heightened preventive public measures by governments and creating awareness on using preventive protective and environmental hygienic measures through educational programmes may substantially reduce the risk of contracting infections in these areas and spreading to other areas.

Malaria Transmission Under an Unusual Circumstance Causing Death in Two Siblings

Two school-going siblings from a family residing in a presumed malaria non-endemic locality ∼90 km from Mangalore city in southwestern India contracted Plasmodium falciparum infection. In both cases, misunderstanding of initial clinical symptoms as due to viral hepatitis resulted in progression to severe malaria before malaria treatment was initiated. Despite treatment at a tertiary hospital, the children died of cerebral malaria and multi-organ dysfunction. Active case detection in the affected locality suggested that the infection was transmitted from infected individuals who worked in nearby malaria-endemic areas and periodically visited their families. A lesson from this study is that lethal falciparum malaria can be transmitted in regions of India, believed to be non-endemic for the disease, resulting in fatal outcomes if diagnosis is missed or delayed. Implementation of effective surveillance and control measures as well as preparedness for malaria detection and diagnosis are necessary in areas that are potentially disposed to malaria transmission even though they are presumed to be non-endemic.

Construction site workers' malaria knowledge and treatment-seeking pattern in a highly endemic urban area of India

Background

Construction sites are potential breeding places for some species of mosquitoes. Construction workers usually stay at the construction sites, thus being extremely susceptible to malaria. For malaria control, a special focus on them is warranted as they often seek treatment from unregulated, private vendors, increasing their risk of exposure to substandard drugs.

Objectives

To elicit the socio-demographic factors associated with comprehensive malaria knowledge (symptoms, mode of spread, and preventive measures) and treatment-seeking pattern (preferred source and type of treatment) among the construction workers in Mangaluru, India; and, to study the association among their comprehensive malaria knowledge, past suffering from malaria (within 1 year) and treatment-seeking pattern.

Methods

A community based cross-sectional study was conducted in nine randomly selected construction sites of Mangaluru, a high-risk city for malaria with an annual parasite incidence of >2/1000/year, from June–September 2012. A sample size of 132 was estimated assuming at least 30 % of them have satisfactory malaria knowledge, 10 % absolute precision, 95 % confidence level, design effect of 1.5 and 10 % non-responses. A semi-structured interview schedule was used, and knowledge scores were computed. Multivariate linear (for knowledge score) and logistic regressions (for preferred source and type of treatment) were applied.

Results

One hundred and nineteen workers participated in the study (total approached-138). 85 % (n = 101) of them were males. Mean knowledge score was 9.95 ± 3.19 (maximum possible score-16). The majority of them were aware of the symptoms and the mode of malaria transmission. However, <12 % could explain the malaria preventive measures. Females workers (β = −0.281, p = 0.001), self stated malaria within 1 year (β = 0.276, p < 0.001) and who preferred allopathic treatment (β = 0.283, P = 0.001) displayed better knowledge scores. Male workers (AdjOR 7.21, 95 % CI 2.3–22.9) and those with self stated malaria within 1 year (AdjOR 11.21, 95 % CI 2.38–52.8) showed favorable treatment-seeking pattern.

Conclusions

There is an urgent need of intensifying and streamlining of ongoing malaria prevention activities for construction site workers in Mangaluru, India. Emphasizing the gender equity at every stage of programme implementation and addressing their treatment-seeking pattern is essential. Involvement of labour employers and building contractors in this regard is imperative.

The Anopheles stephensi odorant binding protein 1 (AsteObp1) gene: a new molecular marker for biological forms diagnosis

Anopheles (Cellia) stephensi Liston 1901 is known as an Asian malaria vector. Three biological forms, namely "mysorensis", "intermediate", and "type" have been earlier reported in this species. Nevertheless, the present morphological and molecular information is insufficient to diagnose these forms. During this investigation, An. stephensi biological forms were morphologically identified and sequenced for odorant-binding protein 1 (Obp1) gene. Also, intron I sequences were used to construct phylogenetic trees. Despite nucleotide sequence variation in exon of AsteObp1, nearly 100% identity was observed at the amino acid level among the three biological forms. In order to overcome difficulties in using egg morphology characters, intron I sequences of An. stephensi Obp1 opens new molecular way to the identification of the main Asian malaria vector biological forms. However, multidisciplinary studies are needed to establish the taxonomic status of An. stephensi.

Killing the hypnozoite--drug discovery approaches to prevent relapse in Plasmodium vivax

The eradication of malaria will only be possible if effective, well-tolerated medicines kill hypnozoites in vivax and ovale malaria, and thus prevent relapses in patients. Despite progress in the 8-aminoquinoline series, with tafenoquine in Phase III showing clear benefits over primaquine, the drug discovery challenge to identify hypnozoiticidal or hypnozoite-activating compounds has been hampered by the dearth of biological tools and assays, which in turn has been limited by the immense scientific and logistical challenges associated with accessing relevant human tissue and sporozoites. This review summarises the existing drug discovery series and approaches concerning the goal to block relapse.

Molecular characterization, biological forms and sporozoite rate of Anopheles stephensi in southern Iran

OBJECTIVE

To identify the biological forms, sporozoite rate and molecular characterization of the Anopheles stephensi (An. stephensi) in Hormozgan and Sistan-Baluchistan provinces, the most important malarious areas in Iran.

METHODS

Wild live An. stephensi samples were collected from different malarious areas in southern Iran. The biological forms were identified based on number of egg-ridges. Molecular characterization of biological forms was verified by analysis of the mitochondrial cytochrome oxidase subunit I and II (mtDNA-COI/COII). The Plasmodium infection was examined in the wild female specimens by species-specific nested-PCR method.

RESULTS

Results showed that all three biological forms including mysorensis, intermediate and type are present in the study areas. Molecular investigations revealed no genetic variation between mtDNA COI/COII sequences of the biological forms and no Plasmodium parasites was detected in the collected mosquito samples.

CONCLUSIONS

Presence of three biological forms with identical sequences showed that the known biological forms belong to a single taxon and the various vectorial capacities reported for these forms are more likely corresponded to other epidemiological factors than to the morphotype of the populations. Lack of malaria parasite infection in An. stephensi, the most important vector of malaria, may be partly due to the success and achievement of ongoing active malaria control program in the region.

Advances in nanomedicines for malaria treatment

Malaria is an infectious disease that mainly affects children and pregnant women from tropical countries. The mortality rate of people infected with malaria per year is enormous and became a public health concern. The main factor that has contributed to the success of malaria proliferation is the increased number of drug resistant parasites. To counteract this trend, research has been done in nanotechnology and nanomedicine, for the development of new biocompatible systems capable of incorporating drugs, lowering the resistance progress, contributing for diagnosis, control and treatment of malaria by target delivery. In this review, we discussed the main problems associated with the spread of malaria and the most recent developments in nanomedicine for anti-malarial drug delivery.

Prevalence of malaria, dengue, and chikungunya significantly associated with mosquito breeding sites

OBJECTIVES

To observe the prevalence of malaria, dengue, and chikungunya and their association with mosquito breeding sites.

METHODS

The study was observational and analytical. A total of 162 houses and 670 subjects were observed during the study period. One hundred forty-two febrile patients were eligible for the study. After obtaining informed consent from all febrile patients, 140 blood samples were collected to diagnose malaria, dengue, and chikungunya. Larval samples were collected by the standard protocol that follows. Correlation of data was performed by Pearson correlation test.

RESULTS

Forty-seven blood samples were found positive: 33 for chikungunya, 3 for dengue, and 11 for malaria. Fifty-one out of 224 larval samples were found positive. Out of the 51 positive samples, 37 were positive for Aedes, 12 were positive for Anopheles, and two were positive for Culex larvae.

INTERPRETATION AND CONCLUSION

Mosquito-borne fevers, especially malaria, dengue, and chikungunya, have shown a significant relationship with mosquito breeding sites.

Distribution of sibling species of Anopheles culicifacies s.l. and Anopheles fluviatilis s.l. and their vectorial capacity in eight different malaria endemic districts of Orissa, India

The study was undertaken in eight endemic districts of Orissa, India, to find the members of the species complexes of Anopheles culicifacies and Anopheles fluviatilis and their distribution patterns. The study area included six forested districts (Keonjhar, Angul, Dhenkanal, Ganjam, Nayagarh and Khurda) and two non-forested coastal districts (Puri and Jagatsingpur) studied over a period of two years (June 2007-May 2009). An. culicifacies A, B, C and D and An. fluviatilis S and T sibling species were reported. The prevalence of An. culicifacies A ranged from 4.2-8.41%, B from 54.96-76.92%, C from 23.08-33.62% and D from 1.85-5.94% (D was reported for the first time in Orissa, except for occurrences in the Khurda and Nayagarh districts). The anthropophilic indices (AI) were 3.2-4.8%, 0.5-1.7%, 0.7-1.37% and 0.91-1.35% for A, B, C and D, respectively, whereas the sporozoite rates (SR) were 0.49-0.54%, 0%, 0.28-0.37% and 0.41-0.46% for A, B, C and D, respectively. An. fluviatilis showed a similarly varied distribution pattern in which S was predominant (84.3% overall); its AI and SR values ranged from 60.7-90.4% and 1.2-2.32%, respectively. The study observed that the co-existence of potential vector sibling species of An. culicifacies (A, C and D) and An. fluviatilis S (> 50%) was responsible for the high endemicity of malaria in forested districts such as Dhenkanal, Keonjhar, Angul, Ganjam, Nayagarh and Khurda (> 5% slide positivity rate). Thus, the epidemiological scenario for malaria is dependent on the distribution of the vector sibling species and their vectorial capacity.

Reduced susceptibility to selected synthetic pyrethroids in urban malaria vector Anopheles stephensi: a case study in Mangalore city, South India

BACKGROUND

Synthetic pyrethroids are potent insecticides most commonly used in the vector control programme. These are applied for indoor residual sprays, space sprays and in impregnated bed nets. Resistance reduces the efficacy of insecticides. Thus, the susceptibility status of the target vector(s) is monitored routinely to select the effective ones. A study was undertaken in a malaria endemic coastal city Mangalore, Karnataka, South India, against the known malaria vector Anopheles stephensi.

METHODS

The susceptibility status was assessed at diagnostic doses of DDT (4%), malathion (5%), deltamethrin (0.05%), cyfluthrin (0.15%), alphacypermethrin (0.10%), lambdacyhalothrin (0.05%) and permethrin (0.75%) using the standard WHO tube test method during October/November 2006.

RESULTS

Anopheles stephensi was resistant to malathion by 54.9%, but tolerant to deltamethrin by 86.1%, cyfluthrin 95.5% and alphacypermethrin 90.6%, whereas it was susceptible to DDT by 98.1%, lambdacyhalothrin 98.6% and permethrin 100.0%, respectively. The KDT50 and KDT95 values for these insecticides also showed the similar responses.

CONCLUSION

Susceptibility of An. stephensi to DDT is an important finding as this has never been used in Mangalore city, whereas its rural counterpart Anopheles culicifacies is widely resistant to this insecticide. The study explores the selection and rotation of the appropriate insecticide molecule even within the same group for effective vector management.