Spatio-temporal distribution of Aedes mosquitoes in Car Nicobar Island: Implication in the transmission of arboviruses

Arboviral infections, viz. dengue and chikungunya are prevalent in the Andaman & Nicobar Islands. During post-tsunami developmental activities, large plastic tanks were provided to the native, Nicobarese tribal households of Car Nicobar Island, to store water for domestic use. These tanks form an ideal breeding source for mosquitoes, especially the vectors of dengue/chikungunya viruses, and few cases of IgM ELISA positives for these infections were identified from this island. In view of this scenario, a survey was carried out to determine the prevalence of these mosquito vectors. Ten randomly selected clusters (neighborhoods with 50 houses each) were surveyed. Each household was inspected for the water holding receptacles. This was the first attempt to determine the prevalence and distribution of the vectors of dengue/chikungunya virus in this Island, against the backdrop of various post tsunami rehabilitation and developmental activities. The stegomyia indices with respect to houses and containers were high during the winter and post-monsoon periods (House Index and Container Index were 69.40 and 46.41 in winter, while 54.40 and 39.49 in post-monsoon). Large plastic tanks (500–1000 l capacity) recorded the highest Breteau Index during all the four seasons. This habitat was observed to support four mosquito species, of which 52% constituted Aedes albopictus. The pupae/person index ranged from 0 to 0.2946. A community-based control approach with multiple stakeholders is envisaged to prevent the vector breeding. This approach would be feasible and effective, with active participation of the tribal chieftain along with village headmen.     

Diversity of fungal endophytes in shrubby medicinal plants of Malnad region,Western Ghats,Southern India

A total of 6125 fungal endophytes were isolated from 9000 leaf segments of 15 medicinal shrubs growing in Malnad region of Western Ghats, Southern India, during winter, monsoon, and summer seasons. These fungal isolates belonged to Ascomycota (8.6 %), Coelomycetes (26.0 %), Hyphomycetes (28.0 %), Mucoromycotina (0.3 %) and sterile forms (4.9 %). Alternaria, Chaetomium, Fusarium, Colletotrichum, Cladosporium, Penicillium, Phyllosticta and Xylaria were the most frequently isolated. Significantly more isolates were obtained during the winter season than monsoon and summer seasons.     

Spatiotemporal variability in archaeal communities of tropical coastal waters

Spatiotemporal variations in the archaeal community structure from four locations along the central west coast of India were analyzed by denaturing gradient gel electrophoresis (DGGE) profiling and sequencing of prominent bands on the DGGE gels. A total of 36 water samples were collected during pre-monsoon, post-monsoon and monsoon seasons from three depths (surface, mid-depth , and close to bottom ～20 m). The community DNA extracts from these samples were subjected to DGGE analysis. The results of this study clearly indicate a significant difference in the community structure between sampling locations and seasons. Location-wise variation was more pronounced during pre-monsoon and post-monsoon seasons. During monsoon, however, the depth-wise variation was pronounced, suggesting monsoon influence on archaeal community structure. Sequencing of DGGE bands suggested the presence of marine group I and II archaea. Canonical correspondence analysis indicated that nitrate, nitrite and chlorophyll a were the significant explanatory variables responsible for > 60 % variation in archaeal community in these coastal waters.     

Impact of season on haematological and biochemical parameters of crossbred female calves in hot and humid tropics

The objective of the present study was to assess the impact of season on haematological and biochemical parameters of crossbred female calves. Seven crossbred female calves of 6–12 months of age were selected. The study was conducted in three different spells of 30 days each in pre-monsoon, monsoon and post-monsoon seasons. Ambient temperature (AT), relative humidity (RH) and temperature humidity index (THI) was recorded in all the three seasons. Whole blood was collected for estimation of haematological and plasma was used estimation of biochemical parameters. Highest AT and THI was recorded in pre-monsoon while highest RH was recorded in monsoon. The study revealed that season had no effect on haematological parameters such as total leucocyte, haemoglobin, packed cell volume, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, while total erythrocyte count was significantly lower in monsoon compared to pre and post-monsoon seasons. Glucose and cholesterol were significantly lower in pre-monsoon and monsoon compared to post-monsoon. Glutathione peroxidase activity was significantly higher in pre-monsoon compared to monsoon and post-monsoon. No significant difference between seasons in the concentration of total protein, albumin, globulin and albumin globulin ratio was noticed. The results indicate that hot conditions have profound effect on haematological and biochemical parameters of crossbred calves.     

Prevalence and resting behaviour of dengue vectors,Aedes aegypti and Aedes albopictus in dengue high risk urban settings in Colombo,Sri Lanka

Understanding local geographical variation in vector density and bionomics related to virus transmission are critical for planning effective vector control programs to control dengue virus transmission. This study investigated the prevalence and resting behaviour of Aedes aegypti and Ae. albopictus in three dengue high-risk areas in the Colombo District, Sri Lanka. Monthly sampling of resting adult mosquitoes was conducted from August 2019 to February 2020. Thirty-seven percent of the households (289/776) harboured Aedes mosquitoes, and 603 Aedes mosquitoes were collected. The proportion of Ae. aegypti was higher in the overall collection during the collection period (94% [569/603]), and 62% (352/569) were females. Significant monthly variations in Ae. aegypti were observed with respect to the indices: number of females per surveyed house (F/SH; p = 0.001), number of females per Aedes positive house (F/PH; p = 0.029), adult house index (AHI; p = 0.001), adult density (AD; p = 0.005) and resting ratio (RR; p = 0.001). AHI, AD, and RR had statistically significant positive correlations with monthly rainfall (p = 0.001, p = 0.011, and p = 0.002 respectively) and one-month lagged dengue cases (p = 0.002, p = 0.005, and p < 0.001 respectively). A statistically significantly higher proportion of Ae. aegypti females were caught resting indoors (N = 309, 88%) than outdoors (N = 43, 12%; p < 0.001). The most common resting areas were bedrooms (51%) & living/dining rooms (37%), and places were under or on furniture (47%) & hangings (34%) for Ae. aegypti. Conversely, 74% of female Ae. albopictus were collected outdoors. Results of this study could have strong implications to improve vector surveillance and control by early detection of dengue to detect outbreaks and minimization of disease transmission.     

Seasonal abundance and activity of pill millipedes (Arthrosphaera magna) in mixed plantation and semi-evergreen forest of southern India

Seasonal occurrence and activity of endemic pill millipedes (Arthrosphaera magna) were examined in organically managed mixed plantation and semi-evergreen forest reserve in southwest India between November 1996 and September 1998. Abundance and biomass of millipedes were highest in both habitats during monsoon season. Soil moisture, conductivity, organic carbon, phosphate, potassium, calcium and magnesium were higher in plantation than in forest. Millipede abundance and biomass were about 12 and 7 times higher in plantation than in forest, respectively (P < 0.001). Their biomass increased during post-monsoon, summer and monsoon in the plantation (P < 0.001), but not in forest (P > 0.05). Millipede abundance and biomass were positively correlated with rainfall (P = 0.01). Besides rainfall, millipedes in plantation were positively correlated with soil moisture as well as temperature (P = 0.001). Among the associated fauna with pill millipedes, earthworms rank first followed by soil bugs in both habitats. Since pill millipedes are sensitive to narrow ecological changes, the organic farming strategies followed in mixed plantation and commonly practiced in South India seem not deleterious for the endangered pill millipedes Arthrosphaera and reduce the risk of local extinctions.     

Effect of microwave irradiation on the structure of glucoamylase

In the present study, we describe changes in the primary and secondary structural patterns of glucoamylase during starch hydrolysis under microwave irradiation using SDS-PAGE and circular dichroism (CD) spectroscopy. Our SDS-PAGE results show that the primary structure of glucoamylase did not change after microwave irradiation. According to the CD spectra, the positive peak height (λ = 193 nm) of the microwave-irradiated samples decreased by 36.4–68.2% compared to those without irradiation, whereas the double negative peak height (λ = 206 nm, λ = 220 nm) increased by 10.8–31.4%. In addition, the positive peak (λ = 193 nm) shifted by 0.2–3 nm. After treatment of glucoamylase with microwave irradiation, the α-helical content of glucoamylase decreased sharply, whereas the β-sheet, β-turn and random coil content increased gradually. The conformational changes of glucoamylase after microwave irradiation provide theoretical support for the mechanism whereby microwave irradiation accelerates starch hydrolysis catalyzed by glucoamylase.     

Studies on the resting behaviour and host choice of Anopheles gambiae and An. arabiensis from Muleba,Tanzania

The relative efficacy of a mechanical (Prokopack) collection method vs. manual aspiration in the collection of resting mosquitoes was evaluated in northern Tanzania before and after an intervention using indoor residual spraying and longlasting insecticide‐treated nets. In smoke‐free houses mosquitoes were collected from the roof and walls, but in smoky houses mosquitoes were found predominantly on the walls. Anopheles gambiae (Diptera: Culicidae) constituted 97.7% of the 312 An. gambiae complex specimens identified before but only 19.3% of the 183 identified after the intervention. A single sampling with the Prokopack collected a third of the available insects. Anopheles gambiae completed its gonotrophic development indoors, whereas Anopheles arabiensis did so outdoors. In both species gonotrophic development took 2 days. Most unfed resting An. arabiensis collected outdoors were virgins, whereas the majority of engorged insects were parous (with well‐contracted sacs). Daily survival was estimated to be 80.0%. Only 9.4% of the engorged An. arabiensis collected outdoors and 47.1% of those collected indoors had fed on humans. Using the Prokopack sampler is more efficient than manual methods for the collection of resting mosquitoes. Malaria transmission may have been affected by a change in vector composition resulting from a change in feeding, rather than reduced survival. Monitoring the proportions of members of the An. gambiae complex may provide signals of an impending breakdown in control.     

Natural parasitism of Romanomermis iyengari (Welch) (Nematoda: Mermithidae) on various species of mosquitoes breeding in rice fields in Pondicherry,India

Natural habitat of Romanomermis iyengari, an entomophilic mermithid nematode, is rice field. Parasitism of this nematode on mosquito larvae breeding in rice fields in Pondicherry, India, has been studied in 1979. The present study was to find out its persistence in the same habitat, after many years of agricultural practices. Evaluation of parasitism on mosquito larvae was carried out during two rice cultivation seasons at a schedule of 1 week prior, and 1 and 2 weeks after transplantation of paddy. Larval stages of mosquito species such as Culex tritaeniorhynchus, Culex vishnui, Anopheles vagus, and Anopheles subpictus showed parasitism of R. iyengari. Parasitism was the highest on C. tritaeniorhynchus with a maximum of 15.38% during season I and 17.85% during season II. Followed by this, it was on A. vagus (10.82% and 9.43%), C. vishnui (7.37% and 8.69%), and A. subpictus (3.70% and 6.36%). The overall density of mosquito larvae and level of parasitism of R. iyengari on them during season II was significantly higher than that of season I. The parasitism was maximum at 1 week before transplantation and showed a decreasing trend towards 2 weeks after transplantation, during both the seasons. The level of natural parasitism of R. iyengari during the present investigation was higher than that observed in the same ecosystem almost 35 years ago. This is clearly an indication towards the capability of the nematode to withstand several years of agricultural practices, including pesticide and agrichemical application. Hence, if applied at sufficient level and frequency, this nematode could act as a successful biocontrol agent against mosquitoes breeding in rice fields.     

Facile fabrication of eco-friendly nano-mosquitocides: Biophysical characterization and effectiveness on neglected tropical mosquito vectors

Mosquito (Diptera: Culicidae) vectors are solely responsible for transmitting important diseases such as malaria, dengue, chikungunya, Japanese encephalitis, lymphatic filariasis and Zika virus. Eco-friendly control tools of Culicidae vectors are a priority. In this study, we proposed a facile fabrication process of poly-disperse and stable silver nanoparticles (Ag NPs) using a cheap leaf extract of Ichnocarpus frutescens (Apocyanaceae). Bio-reduced Ag NPs were characterized by UV–vis spectrophotometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The acute toxicity of I. frutescens leaf extract and green-synthesized Ag NPs was evaluated against larvae of the malaria vector Anopheles subpictus, the dengue vector Aedes albopictus and the Japanese encephalitis vector Culex tritaeniorhynchus. Compared to the leaf aqueous extract, Ag NPs showed higher toxicity against A. subpictus, A. albopictus, and C. tritaeniorhynchus with LC₅₀ values of 14.22, 15.84 and 17.26 μg/mL, respectively. Ag NPs were found safer to non-target mosquito predators Anisops bouvieri, Diplonychus indicus and Gambusia affinis, with LC₅₀ values ranging from 636.61 to 2098.61 μg/mL. Overall, this research firstly shed light on the mosquitocidal potential of I. frutescens, a potential bio-resource for rapid, cheap and effective synthesis of poly-disperse and highly stable silver nanocrystals.     

A molecular phylogeny of mosquitoes in the Anopheles barbirostris Subgroup reveals cryptic species: Implications for identification of disease vectors

The Barbirostris Subgroup of the genus Anopheles includes six mosquito species that are almost identical in adult morphology, but differ in their roles in the transmission of malaria and filariasis within Southeast Asia. The lack of robust, diagnostic morphological characters in adults has contributed to extensive misidentification of the species. Mosquitoes were collected from localities in Thailand and Indonesia, with an emphasis on specimens identified in the field as An. barbirostris and An. campestris. A 754 bp COI mitochondrial gene fragment was sequenced from 136 specimens and the rDNA ITS2 region (c.1600–1800 bp) from 51 specimens. Phylogenetic analyzes based on Bayesian methods, distance measures and Maximum-parsimony produced five clades (I–V) that are congruent between the nuclear and mitochondrial data sets. Based on adult female morphology, it is deduced that three of these clades, I–III, are members of the Barbirostris Complex whereas Clade V is An. campestris. The identity of Clade IV is as yet unknown. Using a haplotype network analysis, Clade III was found to have a star-like genealogy, suggesting population expansion. There were no shared haplotypes between clades. In Afrotropical anopheline mosquitoes, speciation has been linked to the expansion of human populations and the development of agriculture. We postulate that the radiation of species within the Barbirostris Subgroup in Southeast Asia may similarly be linked to human population expansion and the agrarian revolution. The development of a propensity for feeding on the blood of humans in some species of the Subgroup would have led to the transmission of malaria protozoa and filarial nematodes.     

Hybrid fluorescent conjugates of COX-2 inhibitors: Search for a COX-2 isozyme imaging cancer biomarker

The observation that the cyclooxygenase-2 (COX-2) isozyme is over-expressed in multiple types of cancer, relative to that in adjacent non-cancerous tissue, prompted this investigation to prepare a group of hybrid fluorescent conjugates wherein the COX inhibitors ibuprofen, (S)-naproxen, acetyl salicylic acid, a chlororofecoxib analog and celecoxib were coupled via a linker group to an acridone, dansyl or rhodamine B fluorophore. Within this group of compounds, the ibuprofen-acridone conjugate (10) showed potent and selective COX-2 inhibition (COX-2 IC₅₀ = 0.67 μM; SI = 110.6), but its fluorescence emission (λ_em = 417, 440 nm) was not suitable for fluorescent imaging of cancer cells that over-express the COX-2 isozyme. In comparison, the celecoxib-dansyl conjugate (25) showed a slightly lower COX-2 potency and selectivity (COX-2 IC₅₀ = 1.1 μM; SI > 90) than the conjugate 10, and it possesses a better fluorescence emission (λ_em = 500 nm). Ultimately, a celecoxib-rhodamine B conjugate (28) that exhibited moderate COX-2 potency and selectivity (COX-2 IC₅₀ = 3.9 μM; SI > 25) having the best fluorescence emission (λ_em = 580 nm) emerged as the most promising biomarker for fluorescence imaging using a colon cancer cell line that over-expresses the COX-2 isozyme.     

A single-round multiplex PCR assay for the identification of Anopheles minimus related species infected with Plasmodium falciparum and Plasmodium vivax

This study aimed to develop a single-round multiplex PCR method for the identification of Anopheles minimus complex (An. minimus and Anopheles harrisoni) and Anopheles aconitus subgroup (An. aconitus and Anopheles varuna), and for the simultaneous detection of Plasmodium falciparum and Plasmodium vivax in these vectors. Five primers were created for a single-round multiplex PCR assay to identify four anopheline mosquitoes combined with three Plasmodium primers for the detection of P. falciparum and P. vivax in vectors. The four species of anopheline vectors and two Plasmodium species, P. falciparum and P. vivax, could be identified by the combination of eight primers in the single-round multiplex PCR assay. The amplified species-specific products were 380 bp for An. minimus, 180 bp for An. harrisoni, 150 bp for An. aconitus, 310 bp for An. varuna, 276 bp for P. falciparum, and 300 bp for P. vivax. The sensitivities were 0.5 pg/μl (25 sporozoites/μl) for P. falciparum DNA and between 0.5 and 5 pg/μl (25–250 sporozoites/μl) for P. vivax DNA. Furthermore, this developed method could be used to identify field caught An. minimus complex, An. aconitus subgroup from Thailand and Lao PDR. Also, it was successfully used to identify the species An. minimus, An. harrisoni, An. aconitus and An. varuna and to detect and identify P. falciparum and P. vivax in caught anopheline mosquitoes. The sensitivity of this method was high for simultaneous detection of P. falciparum and P. vivax in anopheline mosquitoes.     

Environmental drivers on seasonal abundance of riverine-estuarine V. cholerae in the Indian Sundarban mangrove

Gangetic delta is considered as the homeland of cholera, which is thought to be influenced by changes in populations of estuarine Vibrio cholerae. We aim to identify the environmental, biotic and abiotic driving forces influencing the V. cholerae dynamics in riverine-estuarine environment of southern deltaic Bengal. Cultivable Vibrio count (CVC) ranged between 1 and 10³ colony forming units (CFU)/mL at a salinity gradient of 1.9–30 practical salinity unit (PSU). Increased water temperatrure during summer influences the higher CVC followed by a sudden fall along with the onset of monsoon upto winter. While summer V. cholerae O1 peak (50–100 CFU/mL) can be associated with higher water temperature (P < 0.05) and higher turbidity (P < 0.005); sharp fall during monsoon (15–45 CFU/mL) is attributed to reduced salinity (25–2.5 PSU). Plankton attached V. cholerae O1 varied between 10 and 1000 CFU/mL with a highest peak at winter followed by summer and monsoon. Prevalence of toxigenic V. cholerae O1 in low salinity (2–7.5 PSU) during monsoon identifies that high water temperature (>25 °C), higher turbidity (>100 NTU) and lower salinity plays the pivotal role in toxicity acquisition. Present investigation establishes the role of Sundarban mangrove, where V. cholerae exist in an avirulent condition. During migration towards low saline inland system, V. cholerae pool possibly acquires toxin genes under the influence of environmental factors. Planktonic attachment is possibly a survival strategy at adverse condition, when they do not acquire any toxin gene. Seasonal V. cholerae dynamics has been thoroughly established in environmental settings of high saline mangrove and brackish water flowing to inland low saline condition.     

Magnetic properties of six-coordinated high-spin cobalt(II) complexes: Theoretical background and its application

In this contribution we study and analyse the influence of the different parameters involved in the magnetic susceptibility of six-coordinated high-spin Co(II) complexes. We propose an empirical expression to fit the magnetic susceptibility of polycrystalline samples of mononuclear Co(II) complexes with an axial distortion, the variable parameters being Δ (axial distortion), α (orbital reduction factor) and λ (spin–orbit coupling). This expression avoids solving the 12 × 12 matrix associated to the distortion of the ⁴T_1g term. In order to take into account the magnetic coupling (J) in the polynuclear Co(II) complexes, a perturbational approach is proposed to describe their magnetic susceptibility in the whole temperature range (2–300 K) as a function of J, Δ, α and λ. This approach is valid in the limit of the weak magnetic coupling as compared to the spin–orbit coupling, |J/λ| < 0.1. The model allows the treatment of each cobalt(II) ion in axial symmetry as an effective spin S_eff = 1/2. That causes a drastic reduction of the matrix size of the polynuclear compounds from 12ⁿ × 12ⁿ to 2ⁿ × 2ⁿ, n being the number of Co(II) ions in the complex. The main advantage of the model is to make possible the fit of the magnetic susceptibility data of those polynuclear Co(II) complexes whose high nuclearity involved intractable matrices.     

Excited state properties of dinaphthyl ditelluride

Di-1-naphthyl ditelluride (Te₂naphthyl₂) is characterized by two low-energy excited states. The corresponding electronic transitions nTe → σ¹ Te–Te and nTe → π¹ naphthyl CT give rise to absorptions at λ_max = 403 and 311 nm, respectively. In solution nTe → σ¹ excitation leads to the cleavage of the Te–Te bond. In contrast to Te₂naphthyl₂ in the dissolved state the solid compound shows a luminescence (λ_max = 576 nm) which originates from nTe → π¹ naphthyl CT triplet.     

Synthesis and characterization of a fluorescent probe for α-tocopherol suitable for fluorescence microscopy

Previously prepared fluorescent derivatives of α-tocopherol have shown tremendous utility in both in vitro exploration of the mechanism of ligand transfer by the α-tocopherol transfer protein (α-TTP) and the intracellular transport of α-tocopherol in cells and tissues. We report here the synthesis of a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) containing α-tocopherol analog having extended conjugation with an alkenyl thiophene group that extends the absorption and emission maxima to longer wavelengths (λ_ex = 571 nm and λ_em = 583 nm). The final fluorophore thienyl-ene-BODIPY-α-tocopherol, 2, binds to recombinant human α-TTP with a K_d = 8.7 ± 1.1 nM and is a suitable probe for monitoring the secretion of α-tocopherol from cultured Mcf7#189 cells.     

Osmotic concentration in three races of honey bee,Apis mellifera L. under environmental conditions of arid zone

Hemolymph osmolarity has great effect on honey bee health, especially in arid and semi-arid zones. It regulates water and nutrients in stressed tissues. Osmotic concentration in three races (Apis mellifera ligustica, A. m. carnica and A. m. jemenitica) of Apis mellifera was tested in central Saudi Arabia during spring and summer seasons in 2015. Newly emerged bee workers were first marked and later their hemolymph was extracted after intervals of 1, 5, 10, 15, 20 and 25 days. A significant positive correlation between age and osmolarity was found in all three races during spring and summer seasons. The lowest combined osmotic concentration for all three races was found after 1 day interval, while the highest osmotic concentration was recorded after 25 days. Among all races, A. m. ligustica showed significantly high osmotic concentration after 25 days in spring and summer seasons as compared to the other two races. Only A. m. jemenitica showed similar osmotic concentration after 10 and 15 days in both spring and summer seasons compared to other two races. Mean osmotic concentration of all three races was significantly different after 20 and 25 days in spring and summer seasons. Overall mean recorded during summer was significantly higher than the mean of spring season. Combined osmotic concentration in young drones of all races was significantly lower than that of old drones during spring and summer seasons.     

Byssochlamys nivea with patulin-producing capability has an isoepoxydon dehydrogenase gene (idh) with sequence homology to Penicillium expansum and P. griseofulvum

Nucleotide sequences of the isoepoxydon dehydrogenase gene (idh) for eight strains of Byssochlamys nivea were determined by constructing GenomeWalker libraries. A striking finding was that all eight strains of B. nivea examined had identical nucleotide sequences, including those of the two introns present. The length of intron 2 was nearly three times the size of introns in strains of Penicillium expansum and P. griseofulvum, but intron 1 was comparable in size to the number of nucleotides present in introns 1 and 2 of P. expansum and P. griseofulvum. A high degree of amino acid homology (88 %) existed for the idh genes of the strains of B. nivea when compared with sequences of P. expansum and P. griseofulvum. There were many nucleotide differences present, but they did not affect the amino acid sequence because they were present in the third position. The identity of the B. nivea isolates was confirmed by sequencing the ITS/partial LSU (28 S) rDNA genes. Four B. nivea strains were analysed for production of patulin, a mycotoxin found primarily in apple juice and other fruit products. The B. nivea strains produced patulin in amounts comparable to P. expansum strains. Interest in the genus Byssochlamys is related to the ability of its ascospores to survive pasteurization and cause spoilage of heat-processed fruit products worldwide.