Second twin outcome at birth: retrospective analysis in a single tertiary centre in Malaysia

OBJECTIVES

To investigate factors associated with outcome of second twin during labour.

METHODS

The study was a retrospective cohort study in a single tertiary centre in Malaysia from 2014 until 2018 involving all twin pregnancies delivered at or more than 24 weeks of gestation.

RESULTS

Total of 409 twin pregnancies were included. Dichorionic twin comprises of 54.5 % (n=223) and 45.5 % (n=186) are monochorionic. Women with dichorionic pregnancies are significantly older (p<0.001), have more pre-existing medical disorders (p=0.011) and fetal structural anomalies (p=0.009). Monochorionic pregnancies are significantly more amongst Malay (p=0.01) and conceived spontaneously (p<0.001). There are significantly more fetuses both in cephalic presentation (p=0.026), birthweight discrepancy more than 20 % (p=0.038) and shorter mean inter-twin delivery duration (p=0.048) in monochorionic pregnancies. Second twin delivered with Apgar score <7 is significantly more in dichorionic pregnancies (p=0.006). The second twin is associated with lower birthweight, small for gestational age and arterial cord pH<7.25. Within the group of women who delivered both fetuses vaginally, there was significantly more second twins with intertwin delivery duration less than 30 min who were delivered vaginally without instrumentation (p=0.018). There was significantly more second twin with intertwin delivery duration of 30 min and more with arterial cord pH<7.25 (p=0.045). Those who delivered spontaneously had inter-twin delivery duration within 15-29 min. The outcome of second twin is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth.

CONCLUSIONS

The neonatal outcome for the second twin at birth is not influenced by type of twin, gestational age at delivery, inter-twin delivery duration, mode of delivery and presentation at birth in a cohort managed with non-active management of the second twin in Malaysia.

Binding sites of mosquitocidal toxins of Pseudomonas fluorescens and Bacillus subtilis on pupae and larvae of Culex quinquefasciatus

Two of the potential bacterial isolates, viz., Pseudomonas fluorescens (VCRC B-426) and Bacillus subtilis (VCRC B-471) whose toxins kill the mosquito pupae/larvae have been identified at our center. As the mode of action of these bacteria are not known, an attempt was made to find out the binding sites of the toxic proteins through immunological methods. Antibodies were raised in BALB/c mice and egg yolk system of chicken layers against the mosquitocidal proteins. The antibodies showed specific binding on to the cephalic and thoracic cuticle of the pupae as well as the paddles of the larvae, indicating the binding of the mosquitocidal proteins.

Invasion of toxic marine cyanobacteria in to the tsunami affected coastal villages of southern India

This documentation explores the facts about the invasion of marine cyanobacteria in to the tsunami affected coastal villages of Nagapattinam district of Tamilnadu and Karaikkal district of Pondicherry Union Territory (UT) in southern India. Water samples were collected from eight tsunami-hit coastal villages in different open water sources. The collected samples were processed for detecting marine cyanobacterial growth. Totally 110 water samples were processed, three samples were positive for the toxic cyanobacteria, Lyngbya sp., and nine for nontoxic species such as Epithemia sp.,, Johannesbaptistia pellucida, Oscillatoria princeps, Phormidium fragile, Synechocystis sp. Besides posing a public health risk because of the toxic cyanobacteria, the bloom formation by the cyanobacterial species such as Anabaena, Microcystis, Lyngbya, Plectonema, Phormidium contaminated the water bodies and deteriorated the water quality in the tsunami affected villages. The study revealed that another kind of public health risk from the invasion of toxic cyanobacteria to the costal ecosystem during the tsunami. It is necessary, in this context, that the surveillance mechanism, which is geared up during or after natural disasters, should have a provision to monitor the transportation of toxic elements/organisms from marine system to coastal/inland ecosystems and to control such organisms.

Coconut water as a cheap source for the production of delta endotoxin of Bacillus thuringiensis var. israelensis, a mosquito control agent

Bacillus thuringiensis var. israelensis (B. t. i.) is being widely used in mosquito control programs. However, the large-scale production of this bacillus is expensive due to the high cost of the production medium. In this study, we attempted to develop a cost-effective medium, based on a locally available raw material namely coconut water which is available in plenty as waste product from coconut oil industry. The yield of cell mass, sporulation and mosquito larvicidal activity were studied by growing this bacterium in this waste product and in comparison with the conventional medium (NYSM). Cell mass yield of 3.1g/L, spore count of 3.4x10(11)spores/mL and mosquito larvicidal activity (LC(50)) of 14.85ng/mL (against early fourth-instar larvae of Aedes aegypti) were obtained with a 30h old culture of this bacterium grown in coconut water. This is almost similar to that obtained with NYSM medium. Hence, coconut water-based culture medium is economical for the production of B. t. i.

Production & purification of a fibrinolytic enzyme (thrombinase) from Bacillus sphaericus

BACKGROUND & OBJECTIVE

Treatment of thromboembolic vascular disease has relied on anticoagulants. However, recognition that lysis of preformed fibrin could be accomplished in vivo by a process involving the conversion of inactive plasminogen to active plasmin enzyme led to an alternative enzyme-based approach. The drugs used for this therapy are called the fibrinolytic enzymes. In this study we attempted the production, purification and characterization of fibrinolytic enzyme from Bacillus sphaericus.

METHODS

The seed was prepared in nutrient yeast salt medium (NYSM) in shake flask and organism was produced in 100 l pilot fermentor. Biomass was separated by centrifugation and crude protein was prepared by ammonium sulphate precipitation. Purification was done by ion exchange chromatography using Q sepharose followed by gel filtration chromatography using Sephacryl S- 300. Molecular weight was determined through HPLC. Fibrinolytic activity was assayed by fibrin plate method.

RESULTS

The production method yielded 64 mg/l of the crude enzyme and after purification it was 6.3 mg/l. The molecular weight of the compound was 18.6 kDa.

INTERPRETATION & CONCLUSION

The enzyme exhibited similar fibrinolytic activity as that of streptokinase, on fibrin plates that were devoid of plasminogen, suggesting that its fibrinolytic action is independent of plasminogen and it is not a plasminogen activator.

Transferrin in the mosquito, Culex quinquefasciatus Say (Diptera: Culicidae), up-regulated upon infection and development of the filarial parasite, Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae)

Transferrin is a defence protein known to be up-regulated upon infection of parasites/pathogens in Aedes aegypti mosquito. However, no information is available on its up-regulation in Culex quinquefasciatus, the vector of bancroftian filarial parasite. In the present study, enhancement of transferrin in C. quinquefasciatus infected with Wuchereria bancrofti is demonstrated through amplification of the specific mosquito transcript, its sequencing, cloning, and expression. By using two oligonucleotide primers, a 950-bp polymerase chain reaction product was obtained from the first strand cDNA made from RNA of C. quinquefasciatus infected with W. bancrofti. A 707-bp sequence encoding the mature portion of transferrin was confirmed by sequencing the product. This is the first report of transferrin expression in C. quinquefasciatus. The deduced amino acid sequence shared 85% homology with A. aegypti transferrin precursor molecule. Western blot analysis of haemolymph proteins of infected C. quinquefasciatus with antibodies raised against recombinant transferrin protein showed binding to a 66-kDa protein, confirming its identity as transferrin. Hence, this molecule also could be added to the list of immune molecules of C. pipiens group, such as the defensin, gambicin, and cecropin, which are already known.

Development of lymphatic filarial parasite Wuchereria bancrofti (Spirurida: Onchocercidae) in mosquito species (Diptera: Culicidae) fed artificially on microfilaremic blood

The efficiency of laboratory colonies of mosquitoes such as Anopheles stephensi Liston, Aedes aegypti (L.) Liverpool strain, Ae. aegypti wild type, Aedes albopictus (Skuse), Culex tritaeniorhynchus Giles, Culex sitiens Wiedemann, and Armigeres subalbatus Coquillett in supporting the development of Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae) microfilariae to infective larvae was investigated. The mosquitoes were fed on heparinized microfilaremic human blood by using a membrane-feeding unit with Parafilm as membrane. The rate of infection, parasite development, and parasite burden were compared with that in the known vector mosquito Culex quinquefasciatus Say. Cx. quinquefasciatus showed the highest percentage of infection, followed by Ae. aegypti Liverpool strain and An. stephensi. The rate of development of the parasite was more or less similar in all the three species, and infective larvae were found on day 13. When the larvae were harvested on day 17, Cx. quinquefasciatus yielded the highest numbers, followed by Ae. aegypti Liverpool strain and An. stephensi. The percentage of infection was low, and the development was slow in Cx. tritaeniorhynchus compared with the other susceptible species. The parasite developed to second-stage larvae only by day 22 and to infective larvae by day 28. When 2-wk-old Cx. tritaeniorhynchus were fed on microfilaremic blood, they could develop the parasite to infective larvae by day 13 postfeeding. All other species of mosquitoes tested were found to be refractory to parasite development. It is shown that Cx. quinquefasciatus is the most suitable mosquito host for the production of infective larvae. However, Ae. aegypti Liverpool strain, which is commonly used for Brugia malayi filarial parasite, also can be used for generation of W. bancrofti infective larvae to circumvent the problem of maintaining two mosquito species.

In vitro screening of medicinal plant extracts for macrofilaricidal activity

Methanolic extracts of 20 medicinal plants were screened at 1-10 mg/ml for in vitro macrofilaricidal activity by worm motility assay against adult Setaria digitata, the cattle filarial worm. Four plant extracts showed macrofilaricidal activity by worm motility at concentrations below 4 mg/ml and an incubation period of 100 min. Complete inhibition of worm motility and subsequent mortality was observed at 3, 2, 1 and 1 mg/ml, respectively, for Centratherum anthelminticum, Cedrus deodara, Sphaeranthus indicus and Ricinus communis. 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) reduction assay was carried out at 1 mg ml(-1) and 4-h incubation period, and the results showed that C. deodara, R. communis, S. indicus and C. anthelminticum exhibited 86.56, 72.39, 61.20 and 43.15% inhibition respectively in formazan formation compared to the control.

Metastatic breast carcinoma discovered in a dentigerous cyst — a case report

This paper reports a patient with a history of breast cancer, who presented with altered sensation to the right lower lip and chin. An orthopantomogram showed a probable dentigerous cyst associated with an unerupted lower wisdom tooth, which was closely related to the inferior dental canal. The tooth and cyst were enucleated under general anaesthesia. The subsequent histopathology report concluded that the cyst contained metastatic adenocarcinoma from a primary breast tumour.

Muscoid fly populations in tsunami-devastated villages of southern India

Several coastal villages of southern India were affected by the 26 December 2004 tsunami, and 10,749 people were killed. Investigation carried out in the affected villages during fourth, fifth, and sixth weeks posttsunami showed that the fly density was in the range of 12-91.8 flies per sweep net. In total, 3,259 flies belonging to eight species, namely, Musca domestica L., Musca vicina Macquart, Musca sorbens Wiedemann, Calliphora erythrocephala Robineau-Desvody, Sarcophaga ruficornis F., Chrysomyia sp. Robineau-Desvody, Chlorops sp., and Fannia sp. Robineau-Desvody, were recorded. M. domestica was the predominant species constituting 78.2% of the total flies collected. Density of flies was the highest in temporary shelters constructed for the victims, followed by centralized kitchens and devastated human settlements. Lack of waste control at centralized kitchens nearer to the shelters might be the reason for the high fly density in relief shelters. Under these circumstances, outbreak of fly-borne diseases is likely to be aggravated. Therefore, it is suggested that the ongoing space spraying be supplemented with effective waste control measures to reduce the high density of flies.

Optimization of media composition for the production of cyclosporin A by Tolypocladium species

BACKGROUND & OBJECTIVE

Cyclosporins are produced by certain species of the filamentous fungi, belonging to the genus Tolypocladium. While there are numerous reports on the use of cyclosporins in clinical studies, reports on the various aspects of their production have been very limited. Therefore, this study was carried to optimize the medium composition for the production of cyclosporin A, produced by a strain of the filamentous fungus, Tolypocladium species by static fermentation.

METHODS

The effect of different nutrients on the production of cyclosporin A, produced by Tolypocladium species in stationary culture was studied by growing the fungus for 21 days at 25 +/- 2 degrees C under different media composition. Cyclosporin A was extracted by homogenizing the fungal cells with methanol and the cyclosporin A level was analyzed by high performance liquid chromatography (HPLC).

RESULTS

Among the six different media studied for the production of cyclosporin A, medium 'f' containing glucose (8%), casein acid hydrolysate (3%), malt extract (2%), peptone (1%) and DL- alpha-amino butyric acid (0.5%) favoured the maximum production (2.22 +/- 0.02 g/l medium or 5.85 +/- 0.35 g/kg biomass).

INTERPRETATION & CONCLUSION

This study showed that by optimizing the composition of fermentation media enhanced production of cyclosporin A was obtained. Since the strain Tolypocladium (VCRC F21 NRRL No.18950) produces a high level of cyclosporin A in the identified fermentation medium, it could be exploited for industrial production.

Occurrence and diversity of mosquitocidal strains of Bacillus thuringiensis

Ever since the discovery of the first Bacillus thuringiensis strain capable of killing mosquito larvae, namely, B. thuringiensis var israelensis, there are several reports from different parts of the world about the occurrence of mosquitocidal strains belonging to different subspecies/serotypes numbering thirty-six. The main sources of these wild type strains are soils/sediments, plants, animal feces, sick/moribund insects and waters. The toxicity of the strains within a subspecies/serotype varied widely. Some of the strains exhibited toxicity to mosquitoes as well as lepidopterans and dipterans (including mosquitoes) as well as plant parasitic nematodes.

Changes in the haemocyte population of the mosquito, Culex quinquefasciatus, following infection with the filarial parasite, Wuchereria bancrofti

The mosquito Culex quinquefasciatus Say (Diptera: Culicidae) is the vector of the filarial parasite Wuchereria bancrofti (Cobbold) (Spirurida: Onchocercidae), which causes human bancroftian filariasis. Information on the mosquito humoral response against the filarial parasite during the process of its infection and development is important, as it decides the vector competence of the mosquito. Visible changes in the haemocyte population of mosquito, if any, will be an indicator of the possible humoral factors. The present study was aimed at investigating changes in the populations of various types of haemocytes of Cx. quinquefasciatus following infection with W. bancrofti. On day 2 post-feeding on microfilaraemic blood, the haemolymph perfusate of infected mosquitoes with L1 stage of the parasite showed 44.1% granulocytes, 42% prohaemocytes and 13.9% plasmatocytes, whereas that of the control mosquitoes fed on amicrofilaraemic blood showed 63.4% plasmatocytes, 22.2% prohaemocytes and 14.4% granulocytes. Differences in the population numbers of haemocyte types between the infected and control were significant (P > 0.05). However, the mosquitoes examined on day 6 post-feeding, when the parasite was in L2 stage, did not show any such changes. But, similar changes reappeared on day 12 in mosquitoes with L3 stage of the parasite. The observed haemocyte population changes indicate the possibility of some amount of humoral immune response, through the production of certain immune molecules, in Cx. quinquefasciatus infected with W. bancrofti. The nature and exact role of such a response on the filarial parasite development need further investigation.

Toxicity of a mosquitocidal metabolite of Pseudomonas fluorescens on larvae & pupae of the house fly, Musca domestica

BACKGROUND & OBJECTIVES

Biological control through the use of parasitoids and pathogens is one of the alternatives to the use of chemical pesticides for control of insects of public health importance. At the Vector Control Research Centre, a liquid formulation developed using the metabolite of a Pseudomonas fluorescens strain was found to be lethal to larvae as well as pupae of vector mosquitoes. The lethal fraction of the metabolite is a protein with a molecular mass of 44 kDa and toxicity studies showed that it is safe to mammals. In the present study, this formulation was evaluated against immatures of the common house fly, Musca domestica, to find out whether it could be developed into a potential biocontrol tool.

METHODS

Early second instar larvae of house fly were introduced into rearing medium incorporated with the formulation at concentrations of 1, 5, 10, 15, 20 and 25 per cent, which were equivalent to respectively 1.13, 5.63, 11.25, 16.88, 22.50 and 28.13 microg of the toxic protein/ g of rearing medium. Mortality was monitored until the emergence of adult house fly. Net mortality of larvae and pupae were calculated and the LC50 and LC90 values were determined through probit regression analysis.

RESULTS

Larval mortality was obtained from day 3 to 6 post-treatment. Net mortality of larvae was higher at the concentration of 20 than at 25 per cent. However, it was higher at 25 per cent on day 5 and continued to day 6 when there was no larval mortality at other concentrations. The net mortality of pupae was higher than that of larvae at all the concentrations except at 20 per cent. The LC50 and LC90 values calculated from the net mortality of larvae and pupae together, from day 1 to 12 post-treatment, were respectively, 8.25 and 51.79 microg protein/g of the fly rearing medium.

INTERPRETATION & CONCLUSION

The formulation prepared from the exotoxin of P. fluorescens was toxic to the house fly. Pupae were more susceptible than larvae and the activity of the toxin might have been through cuticular absorption. The results are indicative of the possibility of development of the mosquitocidal metabolite for house fly control through appropriate field evaluations.

Field evaluation of a formulation of Pseudomonas fluorescens against Culex quinquefasciatus larvae and pupae

VCRC B426, 0.09% emulsifiable concentrate (EC) formulation developed from a metabolite of Pseudomonas fluorescens was tested for efficacy against Culex quinquefasciatus larvae and pupae. At application rates of 100, 200, 300 ml/m2, the formulation caused 100% elimination of larvae and pupae at day 1 after treatments and >80% reduction in pupal density for periods of 7, 12 and 11 days in cesspits and 5, 9 and 10 days in U-shaped drains. In both the habitats, the efficacy of the formulation against pupae was 1.7 times more at 200 ml/m2 than at 100 ml/m2. An increase in dosage to 300 ml/m2 did not improve the efficacy in cesspits but a marginal increase was observed in drains.

Oviposition response of the mosquito, Culex quinquefasciatus to the secondary metabolite(s) of the fungus, Trichoderma viride

Secondary metabolites produced by Trichoderma viride, a deuteromycetes fungus, under submerged culture condition were formulated and evaluated for oviposition attractancy against gravid females of Culex quinquefasciatus mosquito. At a concentration of 10 g ml-1 the formulation showed remarkable attractancy with an oviposition active index (OAI) of +0.52. When the oviposition attractancy of the formulation was compared with a known oviposition attractant, p-cresol, both at 10 g ml-1, the former was found to be more attractive to result in 70% egg laying than the later with 30% egg laying. Thin layer chromatography fractions of the secondary metabolites showed that a fraction with Rf value of 0.88 was highly active as oviposition attractant with an OAI of +0.65. Further work on identification of the active principle(s) of the microbial formulation might lead to an oviposition attractant useful in mosquito vector management.

Isolation of a Pseudomonas fluorescens metabolite/exotoxin active against both larvae and pupae of vector mosquitoes

A formulation was developed from the metabolite(s) of a novel Pseudomonas fluorescens Migula strain (VCRC B426) and tested against 4th-instar larvae and pupae of three species of vector mosquitoes, Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti (L). The larvae and pupae of An. stephensi were the most susceptible to the formulation, followed by those of C. quinquefasciatus and Ae. aegypti, in that order, and the dosage requirement for pupal mortality was less than that required for larval mortality. The LC50 dosage requirements for larvae of these mosquito species were, respectively, 70.4, 511.5 and 757.3 microg protein ml(-1), whereas for pupae they were, respectively, 2.0, 9.4 and 19.2 microg protein ml(-1). The lethal fraction was purified from the culture broth and its molecular mass, as determined by high performance liquid chromatography, was 44kDa. This is the first report of a microbial formulation acting upon mosquito pupae, a non-feeding stage. Its mode of action and efficacy to control mosquitoes under field conditions need to be studied further.

Efficacy of a floating sustained release formulation of Bacillus thuringiensis ssp. israelensis in controlling Culex quinquefasciatus larvae in polluted water habitats

Larvicidal efficacy and residual activity of a floating sustained release formulation of Bacillus thuringiensis ssp. israelensis (Bti) was tested in polluted water habitats against Culex quinquefasciatus, the vector of bancroftian filariasis, breeding in cesspools and cesspits. A total of 25 habitats having 65 m(2) water surface area with C. quinquefasciatus immatures were treated with the formulation at the rate of 15 kg/ha. For comparison, in another area, 18 habitats with a water surface area of 70 m(2) were kept untreated. Evaluation was continued up to 179 days with three rounds of Bti application. The mean number of egg rafts did not differ significantly between treated and untreated habitats during the trial period indicating same level of recruitment. However, abundance of larvae and pupae was significantly lower in Bti treated habitats compared to that in untreated ones. The activity of the formulation, with 2 weeks delay in onset compared to treatment, caused >80% reduction in pupal abundance for a period of 30-34 days. Considering this, it is suggested that monthly application of Bti formulation will considerably reduce the recruitment of pupae of C. quinquefasciatus.

Oviposition attractancy of bacterial culture filtrates: response of Culex quinquefasciatus

Oviposition attractants could be used for monitoring as well as controlling mosquitoes by attracting them to lay eggs at chosen sites. In the present study, culture filtrates of seven bacterial species were tested for their attractancy against gravid females of Culex quinquefasciatus. When their oviposition active indices (OAI) were studied, the culture filtrates of Bacillus cereus and Pseudomonas fluorescens exhibited oviposition attractancy (OAI = > 0.3) at 100 ppm and the OAI were respectively 0.70 and 0.47. Culture filtrates of B. thuringiensis var. israelensis (wild type), B. t. var. israelensis (mutant) and B. sphaericus showed attractancy at 2000 ppm with OAI of respectively 0.71, 0.59 and 0.68. However, the OAI of B. megaterium as well as Azospirillum brasilense was 0.13 (at 2000 ppm), which was less than 0.3 required to be considered them as attractants. When the oviposition attractancy of the bacterial culture filtrates were compared with that of a known oviposition attractant, p-cresol (at 10 ppm), the culture filtrates of B. t. var. israelensis (wild type) and B. cereus were found to be more active than p-cresol, respectively with 64.2 and 54.3% oviposition.

Development of a self floating slow release formulation of Bacillus thuringiensis var. israelensis and its larvicidal activity

Alginate encapsulated B. thuringiensis var. israelensis (B. t. i.) self floating type formulations were prepared. Its spore release rate, floating efficacy and larvicidal activity against Culex quinquefasiatus were tested in the laboratory. The larval mortality of 91-100% was induced by the floating formulation with a mean spore release of 3.04 x 10(4)/ml/day from 6th day to 27th day. From day 28 to 33 the mean number of spores released were 1.16 x 10(4)/ml/day which caused 72.2-88.2% mortality. From 34th day to 40th day the mean number of spores released were 4.97 x 10(3)/ml/day which caused 42.2-67.2% mortality. However, the self floating alginate encapsulated beads were intact and found to float upto 40 days.

Susceptibility of ten species of mosquito larvae to the parasitic nematode Romanomermis iyengari and its development

Ten species of mosquitoes (Diptera: Culicidae) from five genera were exposed to preparasites of the tropical mermithid nematode species Romanomermis iyengari (Welch) (Nematoda: Mermithidae), a strain isolated in 1978 from Pondicherry. By exposing mosquito larvae during the second instar, nematode infection was invariably lethal, the rate being highest in Culex sitiens Wiedemann (95%) followed by Cx. quinquefasciatus Say (90%), Aedes aegypti (L.) (79%), Anopheles subpictus Grassi (64%), Ae. albopictus (Skuse) and Armigeres subalbatus Coquillett (62%), Cx. tritaeniorhynchus Giles (57%), Mansonia annulifera (Theobald) (46%), An. stephensi Liston (40%) and An. culicifacies Giles (36%). When fourth-instar larvae were exposed, the infection was highest in Ar. subalbatus (66%), followed by An. stephensi (52%), Cx. quinquefasciatus (47%), Ae. aegypti and An. subpictus (42%), Ae. albopictus (30%), An. culicifacies (29%), Cx. sitiens (24%), Cx. tritaeniorhynchus (19%) and Ma. annulifera (8%), with 2-45% of infected culicines surviving to adulthood. The parasitic phase of the nematode lasted 5-7 days in all the host species, yielding 1.1-3.2 parasites per II instar and 1.1-2.5 parasites per IV instar. The overall output of parasites per 100 mosquito larvae (infected + uninfected) was highest for Ae. aegypti when mosquitoes were exposed during II instar (2.53 parasites/larva) and for Ar. subalbatus when mosquitoes were exposed during IV instar (1.65/larva), and lowest for Ma. annulifera exposed during IV instar (0.09/larva). For routine laboratory culture of R. iyengari it is convenient to employ Cx. quinquefasciatus as the host yielding 90-190 parasites/100 larva.

Development of Wuchereria bancrofti in Culex quinquefasciatus that survived the exposure of sub-lethal dose of Bacillus sphaericus as larvae

Development of Wuchereria bancrofti in Culex quinquefasciatus emerged from the larvae that survived the exposure of sub-lethal dose of Bacillus sphaericus was examined in the laboratory. Third instar larvae of Cx. quinquefasciatus were treated with B. sphaericus at a sub-lethal dose of 11.35 microg/250 ml. The female mosquitoes that emerged from the survived larvae were fed on microfilaraemic human blood and parasite development was monitored in the fed mosquitoes. Both treated and untreated mosquitoes could ingest microfilaria (mF) equally as there was no significant difference in mF density between them. But, density of developmental stages of the parasite in treated group was significantly lower. Since, there was no mortality of mosquitoes, the lower density of the developmental stages could be attributed to the loss of parasites in the treated mosquitoes. Consequently, the proportion of mosquitoes with infective larvae (L3) and number of L3 were also significantly lower in treated females. Delay in parasite development was also noticed in treated mosquitoes. The present study indicates that B. sphaericus, when applied at sub-lethal dose kills larvae, and in addition, inhibits development of the filarial parasite and consequently reduces L3 yield in adult mosquitoes that emerged from the survived larvae.

Effect of entomopathogenic fungus, Beauveria bassiana on larvae of three species of mosquitoes

Beauveria bassiana, an entomopathogenic fungus, was evaluated for its potential against second and third instar larvae of Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti. Conidiospores of this fungus were effective in causing infection leading to mortality of different larval instars. Larvae of Cx. quinquefasciatus were more susceptible to infection than An. stephensi and the second instar larvae of these two species were more susceptible than third instar larvae. Larvae of Ae. aegypti were resistant to infection by B. bassiana.

Enhanced recovery of fourth stage larvae of Wuchereria bancrofti from mongolian gerbil, Meriones unguiculatus & their in vitro maintenance

Earlier attempts to produce different stages of W. bancrofti, such as fourth stage larvae (L4), in small animal models have yielded very low recovery rates. In order to enhance the recovery of L4, two routes of inoculating a small animal, M. unguiculatus, with infective larvae (L3) viz., intraperitoneal and intrathoracic routes, were compared. On day 17 post-inoculation, higher percentage (23-25%) of L4 were recovered from animals inoculated intrathoracically compared to that from animals inoculated intraperitoneally (2-8%). Also, comparatively higher proportion of worms (75-92%) remained within the intrathoracic region, unlike in the intraperitoneal region (50-80%). A few worms (1-4%) could be recovered even on 31 days post-inoculation from animals inoculated intrathoracically. When the L4 produced in animals were cultured in modified Frank's medium, all of them survived for 15 days and 50 per cent survived till the 25th day. The higher yield and ease of recovery from the thoracic cavity makes this route of inoculation a suitable method for production of L4. In vitro maintenance of L4 for prolonged period is significant with respect to excretory/secretory products or for drug screening.

Efficacy of a Bacillus sphaericus formulation as influenced by the quality of Culex quinquefasciatus breeding waters

To understand the physico-chemical factors that influence the efficacy of B. sphaericus formulation in the breeding sites of Culex quinquefasciatus, a study was carried out in Mayiladuturai area of Tamil Nadu (India). The factors studied were hydrogen ion concentration (pH), acidity, alkalinity, chlorides, phosphates, total hardness, sulphates, total solids, dissolved solids, suspended solids, nitrate nitrogen, ammoniacal nitrogen, dissolved oxygen, biological oxygen demand (BOD) and chemical oxygen demand (COD). Efficacy of the formulation was assessed in terms of reduction in larval population in the treated habitats. pH of water in the treated sites was around neutral range (mean +/- SD 7.65 +/- 0.23). Phosphate content was low (2.27 +/- 1.34 ppm) whereas chlorides (326.1 +/- 55.8 ppm) and sulphates (38.9 +/- 23.8 ppm) were high. Total hardness ranged from 206 to 462.5 ppm with a mean of 312.1 +/- 80.5 ppm. The chlorides and sulphates, though present in considerable quantity, did not have any influence on the efficacy of B. sphaericus formulation. However, the proportion of insoluble chlorides and sulphates which contribute to total hardness seemed to influence the formulation adversely.

Effect of insecticidal crystal proteins of Bacillus thuringiensis var. israelensis on the enzymes of rat intestinal brush border membrane vesicles

In vivo treatment of intestinal brush border membrane vesicles with solubilized insecticidal crystal proteins (ICP) from the two strains of B. thuringiensis var. israelensis (VCRC B17 and VCRC MB24) caused no adverse effect on gamma glutamyl transpeptidase, Na+K+ATPase, sucrase and lactase enzymes. But, exposure of membrane vesicles to solubilized ICP's in vitro, lead to significant reduction in the activity of Na+K+ATPase, sucrase and lactase enzymes.

Development of alginate-based slow release formulation of Bacillus sphaericus for controlling Culex quinquefasciatus

Seven types of formulations were prepared as granules using the larvicidal factor of Bacillus sphaericus and different concentrations of calcium alginate which was used as matrix to immobilize and entrap the active ingredient (ai). All formulations were tested in disused wells against Culex quinquefasciatus at the rate of 15 kg ai per hectare. Among the seven types tested, the type 2 which contained 5% calcium alginate as immobilizing agent, exhibited the maximum larvicidal activity. Persistent control in breeding was noticed for 8 weeks with this formulation type.

Effect of insecticidal crystal proteins of Bacillus thuringiensis on human erythrocytes in vitro

Effect of intact and alkali solubilized insecticidal crystal protein (ICP) preparations from a mutant strain of B. thuringiensis var. israelensis (VCRC MB24) and the wild type strain (VCRC B17) in vitro on human erythrocytes with respect to lipid peroxidation, osmofragility and membrane bound enzymes was determined. The alkali solubilized ICPs of both B. thuringiensis strains caused increased lipid peroxidation, decreased resistance to hypotonic lysis and reduction in the activity of membrane bound enzymes. On the contrary, the intact ICPs did not produce any such adverse effect on RBCs under the same experimental conditions. It is suggested that the ICPs are safe when they are intact when compared with solubilized ones.

Efficacy of Bacillus sphaericus in different breeding habitats of Culex quinquefasciatus

'Spherifix', an alginate based slow release formulation of Bacillus sphaericus was field tested in different types of breeding habitats of Culex quinquefasciatus at the dose of 15 kg ai/ha at bimonthly interval. The efficacy of the formulation was higher in most of the months except in rainy and post-rainy months. The mean percentage reduction +/-SD during the treatment phase of one year was 31.2 +/- 17.9, 50 +/- 29.4, 28.3 +/- 17.6, 30.3 +/- 21.1, 66 +/- 22.5 and 53 +/- 20.4 in larval density and 49 +/- 20.8, 65.1 +/- 26.1, 30.3 +/- 21.9, 59.8 +/- 22.6, 63.1 +/- 21.9 and 47.7 +/- 24.2 in pupal density respectively in cement tanks, cesspools, cesspits, disused wells, unlined drains and cement lined drains. The reduction in immature density was relatively higher in undisturbed, debris free and shallow habitats such as cesspools, unlined drains and cement lined drains. After withdrawal of treatment, the effect of the formulation could be seen for a period of four months.

A report on the demonstration of microfilariae of Brugia malayi in the brain of an experimental animal host, Mastomys natalensis

The brain tissues of microfilaraemic animals, Mastomys natalensis, which were earlier inoculated (s.c.) with Brugia malayi infective larvae (100 each) were examined for the occurrence of Mf. This was done by staining squash preparations of the brain tissues which were cleared off from the vascular piamater. Animals with blood Mf count of 50 >/per 20 cu. mm were found to harbour Mf in the brain tissues. The Mf count in the brain varied from 5-86/81 cu. mm (sum of Mf detected in 3 tissue pieces, each of 27 cu. mm collected from 3 parts of the brain, viz., the cerebral hemispheres, cerebellum and medulla oblongata). Teh presence of Mf in the brain was confirmed by its detection in 20-micrometers-thick cryosections of the tissue. Also, fine needle aspirates of cerebral hemispheres of an animal showed live Mf.

Effect of inorganic salts, soaps and detergents on dissolution and larvicidal activity of alginate formulation of Bacillus sphaericus

Various inorganic salts and commonly used soaps and detergents were tested in the laboratory for their effect on the dissolution and larvicidal residual activity of a slow-release alginate encapsulated granular formation of Bacillus sphaericus. Fluoride, chloride and sulphate salts and a detergent powder affected the residual activity of this formulation drastically by rupturing it but did not effect its larvicidal activity. Nitrates and phosphates of sodium and potassium also had the same effect but to a moderate level. The safest concentration of these water impurities for effective functioning of the alginate encapsulated B. sphaericus formulation have been determined.

Longevity and migration of Wuchereria bancrofti infective larvae and their distribution pattern in relation to the resting and feeding behaviour of the vector mosquito, Culex quinquefasciatus

The longevity, migration and distribution of infective larvae (L3) of Wuchereria bancrofti within the host mosquito were studied by feeding Culex quinquefasciatus on microfilaraemic human blood and allowing the microfilariae to develop to L3. The L3 were found to remain alive and active for 46-50 days, i.e. as long as the host mosquitoes survived. The larvae started their migration to the head of the mosquito soon after their development to L3, on day 13 after the initial, infective bloodmeal. Although more L3 were usually found in the head region of the mosquitoes than in the thorax or abdomen, the larvae showed an oscillatory pattern of movement between all three regions. This movement was significant in the mosquitoes fed only on microfilaraemic blood, but not in those that took a second bloodmeal on normal human blood on day 8 after the infective bloodmeal. The distribution of the L3 in the three regions of the mosquitoes was independent of parasite density. Observations on L3 movement over a 24-h period indicated that there were always more L3 in the head than in the thorax and abdomen and that the number of L3 in the head was maximal at 18.00 hours and minimal at 06.00 hours. When infective mosquitoes were fed on human blood through a Parafilm membrane, 45.2% of the L3 present in the mosquitoes were shed into the blood or on the membrane. All the L3 present in each mosquito migrated to its head during feeding.

Effect of temperature on different stages of Romanomermis iyengari, a mermithid nematode parasite of mosquitoes

The effect of temperature (20 degrees-35 degrees C) on different stages of Romanomermis iyengari was studied. In embryonic development, the single-cell stage eggs developed into mature eggs in 4.5-6.5 days at 25-35 degrees C but, required 9.5 days at 20 degrees C. Complete hatching occurred in 7 and 9 days after egg-laying at 35 and 30 degrees C, respectively. At 25 and 20 degrees C, 85-96% of the eggs did not hatch even by 30th day. Loss of infectivity and death of the preparasites occurred faster at higher temperatures. The 50% survival durations of preparasites at 20 and 35 degrees C were 105.8 and 10.6 hr respectively. They retained 50% infectivity up to 69.7 and 30.3 hr. The duration of the parasitic phase increased as temperature decreased. Low temperature favoured production of a higher proportion of females which were also larger in size. The maximum time taken for the juveniles to become adults was 14 days at 20 degrees C and the minimum was 9 days at 35 degrees C. Oviposition began earlier at higher temperature than at lower temperature. However, its fecundic period was shorter at 20 degrees C than at 35 degrees C indicating enhanced rate of oviposition at 20 degrees C. Fecundity was adversely affected at 20 degrees C and 35 degrees C. It is shown that the temperature range of 25 degrees-30 degrees C favours optimum development of R. iyengari.

In vitro cultivation of third stage larvae of Wuchereria bancrofti to fourth stage: influence of some physico-chemical factors

It has been reported that third stage larvae (L3) of Wuchereria bancrofti strain from Jakarta, molted to the fourth stage (L4) in vitro, in a simple culture medium supplemented with 10% human serum. In the present study, this culture medium has been used to examine the effects of some physico-chemical parameters on larval growth, development and molting of Wuchereria bancrofti from India. Lymph at 10% concentration enhanced the in vitro survival time of larvae. Molting of larvae from L3 to L4 stage has been obtained using human fetal lung cells in cellular co-culture and as a source of conditioned medium. Given these improvements in the medium supplementation, it has been observed that the age of L3s (duration of L3s maintenance within the mosquitos) is one of the most important parameters for the development of L3s in vitro. No molting was observed when one day L3s were used whereas, molting occurred with one or two weeks old L3s. On the contrary, when more than 3 weeks old L3s were used molting failed to occur even though duration of survival of L3s was improved and in this case, most of the larvae were degenerated.

Influence of soil moisture on survival and oviposition of Romanomermis iyengari a mermithid nematode parasite of mosquitoes

The oviposition pattern of Romanomermis iyengari (Nematoda: Mermithidae) in relation to the moisture level in the soil was studied by seeding postparasites into two sets of 12 cm soil columns. While one set of the soil column was allowed to dry over a period of 60 days, the other set was maintained at a constant level of 15-20% moisture throughout the soil column. In the soil column maintained at constant moisture level, the postparasites oviposited primarily in the upper 3 cm layer (80-97%). In the soil column which was allowed to dry the percentages of eggs laid in the upper 3 cm layer were 96, 24 and 6 respectively on D20, D30 and D40 after seeding and the moisture levels on respective days were 12, 5 and 3%. On corresponding days the postparasites laid 1, 56 and 42% of the eggs in the lower most layer (9-12 cm) and the moisture levels were respectively 15, 10 and 9%. The results indicate that the adult nematodes migrated towards the bottom layer of the soil and laid eggs as the moisture of the upper layers decreased.

Formation of melanin pigment by a mutant of Bacillus thuringiensis H-14

A mutant of Bacillus thuringiensis H-14 produced a dark brown pigment during sporulation. Production of the pigment depended on the nutritional properties of the growth medium. The pigment was identified as melanin, based on chemical tests and its infra-red spectrum. Incorporation of L-tyrosine in the culture medium enhanced the level of melanin production, and L-3,4-dihydroxyphenylalanine (L-DOPA) was detected in the culture broth during the late-exponential phase of growth. This indicates that the pathway of melanin synthesis is from L-tyrosine, via L-DOPA, to melanin.

Method for storing Lagenidium (Oomycetes: Lagenidiales)

Techniques for storing the mosquito pathogenic fungus, Lagenidium, were evaluated. A technique, which involves storage of fungal mycelia in sterile distilled water of pH 6-7 with 0.0025 M glucose at 30-35 degrees C, was found to be useful. When stored in this manner the fungus retained it's larvicidal activity for 190 days.

Fed-batch fermentation studies with Bacillus thuringiensis H-14 synthesising endotoxin

Cell yield and toxicity of B. thuringiensis H-14 was improved markedly by adopting a simple fed-batch fermentation technique based on controlling glucose concentration. Maintenance of steady glucose concentration (0.3-0.5%) in the culture medium was achieved by the continuous addition of concentrated glucose solution. Addition of glucose at 3 g/hr/l of culture starting from 3rd hr till 16th hr of fermentation was found to yield cell densities of 80 g/l (wet weight) which represented a nearly 3-fold increase over the batch mode. A fivefold increase in toxicity was obtained by fed-batch fermentation. Cultivation of B. thuringiensis H-14 to high cell densities had no negative effect on sporulation and toxin synthesis. The rate of pH drop and dissolved oxygen level were within manageable limits.

An enzyme linked immunosorbent assay for monitoring Bacillus sphaericus toxin

Larvicidal proteins of B. sphaericus H5a5b (strain VCRC B42), purified by ion-exchange chromatography were used to raise antibodies in rabbits. The antibodies were specific in reacting to alkali-solubilized fractions from whole cells of toxic strains only. Ouchterlony immunodiffusion showed homology in toxin structure between strains of different serotype. A sandwich ELISA using avidin-biotin amplification was standardized. The lowest detectable limit was 6.25 ng/ml. Near linear quantitative binding of the antigen was found in the range 25-200 ng/ml. The growth, toxin level and LC50 values during various stages of fermentation of B. sphaericus strains 1593 and B42 were compared. There was significant correlation between LC50 values and toxin levels as measured by ELISA.

Evaluation of cyclosporine-A obtained from Tolypocladium sp. for immunosuppressive potential

Cyclosporine-A obtained from an indigenous isolate of Tolypocladium sp. was evaluated for immunosuppressive potential by skin grafting in rats using the commercially available Sandimmune as reference at 15 and 30 mg/kg/day for a period of 14 days. The Sandimmune treated animal group showed 83 per cent acceptance of skin grafts while the test preparation treated group showed 67-83 per cent acceptance. The degree of nephro- and hepatotoxicity was comparable for both the preparations.