DDT & deltamethrin resistance status of known Japanese encephalitis vectors in Assam, India.

BACKGROUND & OBJECTIVE: Japanese encephalitis (JE) outbreaks are common in Assam, northeastern State of India. Information on resistance in known JE vectors in the affected area is important for effective control measures. This study was undertaken to determine the species abundance of JE vectors endemic to Sibsagar district of Assam, and their susceptibility against DDT and deltamethrin. METHODS: Adult mosquitoes were collected using CDC light trap and aspirators from human dwellings from 13 endemic villages falling under three Primary Health Centres. Collected mosquitoes were identified and unfed female mosquitoes were used for DDT and deltamethrin sensitivity bioassay. The bioassay was performed following WHO protocol using standard susceptibility test kit. Knockdown time (KDT) was monitored at every 10 minutes intervals, whereas mortalities were recorded 24 h post-exposure. Vector density and resistance status were mapped using geographic information system (GIS) technique. RESULTS: A total of 7655 mosquitoes were sampled under three genera, i.e. Anopheles, Culex and Mansonia, and nine species, the JE vector Cx. vishnui group (31.78%) was the most predominant species, followed by Ma. uniformis (16.81%) and Ma. indiana (16.45%). All vector species were suspected to be resistant to DDT and sensitive to deltamethrin, except Ma. indiana, which was suspected to deltamethrin resistant. The KDT50 and KDT95 values of vector mosquitoes for DDT were significantly higher as compared to deltamethrin. The probit model used to estimate KDT50 and KDT95 values did not display normal distribution of percentage knockdown with time for all the vectors tested for DDT and deltamethrin, except for Ma. indiana for deltamethrin assay and Cx. gelidus for the DDT assay. INTERPRETATION & CONCLUSION: Differences in insecticide resistance status were observed between insecticides and vector species. The results of this study provided baseline data on insecticide resistance in known JE vectors of Sibsagar, Assam. The maps generated may allow better communication in control operations and comparison of changes in susceptibility status of these vectors over time.

Study of chemical composition and nutritional values of vegetable wastes in Bangladesh.

The present study was conducted with the objectives of determining the chemical composition and nutritional value of vegetable waste (VW) of households and the marketplace for their suitability as ruminant feed. The crude protein, total digestible nutrients and extent of rumen degradability of dry matter (DM) of VW of households were 140.0 g kg-1, 0.668 and 0.855, respectively; while those of the marketplace were 169.0 g kg-1, 0.633 and 0.80, respectively. The levels of chromium and lead in each respectively, was 13.27 and 1.53 ng kg-1DM; and 31.01 and 5.71 ng kg-1DM. The total aflatoxins in VW of households was 3.08 µg kg-1DM, and undetectable in VW from the marketplace. Considering the chemical composition and safety parameters studied, VW could preliminary be considered as animal feed. The feeding of processed marketplace VW (VWP) at 275 g kg-1DM of a diet or 0.76% of live weight (LW) to growing bulls, replacing 50% of a concentrate mixture as supplement to a Napier silage diet for a period of 34 days reduced the total DM intake (0.0276 vs 0.0343 LW) without any significant (P > 0.05) changes in DM or protein digestibility. Blood urea levels (19.5 vs 23.67 mg dl-1), and serum creatinine levels (1.37 vs 1.08 mg dl-1) differed significantly (P > 0.05) between the two groups but were within normal physiological ranges. Therefore, it may be concluded that the level of incorporation of VWP would be less than 50% replacement of the concentrate in the diet. Further research is required to determine optimum inclusion levels in ruminant diets.

Malaria situation in forest-fringed villages of Sonitpur district (Assam), India bordering Arunachal Pradesh during an outbreak.

BACKGROUND & OBJECTIVES: Epidemiological and entomological studies were undertaken in forest-fringed villages in Sonitpur district (Assam) bordering Arunachal Pradesh, India to assess the malaria situation. Blood smears (thick and thin) were collected from the fever cases through door-to-door survey. Both the blood smears stained with Giemsa were used for malaria parasite detection. Slide positivity rate (SPR) was recorded as 39.1% with predominance of Plasmodium falciparum (97.1%) infections. Children between 5 and 14 yr showed higher rates of infection. METHODS & RESULTS: Over all malaria prevalence was higher among the males (SPR 43.2%) than in females (SPR 34.5%). Adult mosquito collection was made using CDC miniature light-traps from dusk-to-dawn. Per-trap night density of mosquitoes in human dwellings and cattlesheds were 289 and 925, respectively. Anopheles minimus and An. dirus, the major vectors of malaria in Northeastern region of India formed 33.2% of the total vectors recorded. An. dirus could be recorded only from human dwellings. The results showed high malaria risk in the study villages. INTERPRETATION & CONCLUSION: High vector density with high parity rate, poor socio-economic conditions, lack of awareness, poor sanitation and congenial atmosphere for mosquito proliferation are aggravating the malaria situation in the study area.

Preliminary in vitro antiplasmodial activity of Aristolochia griffithii and Thalictrum foliolosum DC extracts against malaria parasite Plasmodium falciparum.

BACKGROUND: Resistance development in human malaria parasites against commonly used antimalarial drugs has necessitated the scientific exploration of traditionally used antimalarial plants. Plant derivatives have been used for curing malaria historically. The present study involves in vitro evaluation of two medicinally important plants Aristolochia griffithii and Thalictrum foliolosum DC used in antimalarial chemotherapy by the tribes of northeast India. METHOD: Chloroform, ethyl acetate and n-butanol extracts of Aristolochia griffithii and Thalictrum foliolosum DC were evaluated in vitro against chloroquine sensitive (SS) and chloroquine resistance strains (RS) of P. falciparum. The tests were conducted following WHO standard method and the inhibition of parasite (IC50) was calculated. RESULTS: In A. griffithii, the IC50 value for ethyl acetate extracts against SS was 6.2 ± 0.02 µg/ml and found to be lower than chloroform extracts, which exhibited an IC50 value of 14.1 ± 0.1 µg/ml (t = 191.1; p < 0.0001). The IC50 values of both chloroform and ethyl acetate extracts for RS were higher as compared to the SS (p < 0.0001). In T. foliolosum DC the IC50 concentration of chloroform extracts for SS and RS were 0.5 ± 0.0 and 1.1 ± 0.0 µg/ml respectively (t = 54.2; p < 0.0001). CONCLUSION: The present findings, although preliminary, but scientifically demonstrate that identification and isolation of active compounds of these two plant materials and testing against different Plasmodium species could lead to the development of potential antimalarial drugs for future.

Synergistic mosquito-repellent activity of Curcuma longa, Pogostemon heyneanus and Zanthoxylum limonella essential oils.

Mosquito repellents play an important role in preventing man-mosquito contact. In the present study, we evaluated the synergistic mosquito-repellent activity of Curcuma longa, Pogostemon heyneanus and Zanthoxylum limonella essential oils. The mosquito repellent efficacies of three essential oils were evaluated separately and in combination under laboratory and field conditions. N,N-Diethylphenylacetamide (DEPA) and dimethylphthalate (DMP) were used for comparison of the protection time of the mixture of essential oils. At an optimum concentration of 20%, the essential oils of C. longa, Z. limonella and P. heyneanus provided complete protection times (CPTs) of 96.2, 91.4 and 123.4 min, respectively, against Aedes albopictus mosquitoes in the laboratory. The 1:1:2 mixture of the essential oils provided 329.4 and 391.0 min of CPT in the laboratory and field trials, respectively. The percent increases in CPTs for the essential oil mixture were 30 for DMP and 55 for N,N-diethylphenylacetamide (DEPA). The synergistic repellent activity of the essential oils used in the present study might be useful for developing safer alternatives to synthetic repellents for personal protection against mosquitoes.

Persistence of leech repellents on cloth.

Trials on persistence of repellent properties of N, N-diethyl phenyl acetamide (DEPA), N,N-diethyl-m-toluamide (DEET), 3acetyl2(2-6-dimethyl-5-heptenyl)oxazolidine(Citronyl) , dimethyl phthalate (DMP) and N-benzoyl piperidine (NBP) on cloth were conducted against land leeches in evergreen rain and deciduous forests of Assam. Results obtained were compared with volatile oil of Zanthoxylum armatum DC. syn. Z. alatum Roxb (Timur) to evaluate its efficacy as leech repellent. DEPA and DEET were found to be the best. Timur oil was at par with Citronyl and exhibited better results than DMP and NBP.

Field trial of Abate and Teknar for Simulium (Diptera: Simuliidae) control in India.

Simulium breeding was eliminated in a river up to 30 km with 0.1 ppm Abate (temephos) for 30 min exposure. Teknar (Bacillus thuringiensis var. israelensis) at 10 ppm for 10 min exposure resulted in 98.4% and 87.9% reduction up to 20 m in 2 sections of a small stream.

Epidemiological and entomological aspects of malaria in forest-fringed villages of Sonitpur district, Assam.

BACKGROUND & OBJECTIVES: Detailed epidemiological and entomological studies were undertaken in forest-fringed villages and a Tea Estate in Sonitpur, Assam to assess the malaria situation. METHODS: Door-to-door active surveillance was carried out to collect blood samples. Thick and thin blood smears stained with Giemsa were used for malaria parasite detection. Mosquito collections were made using CDC miniature light-traps and hand catch methods from dusk-to-dawn. RESULTS: 48% SPR, 49.1 Pf% was recorded from the study villages. Children between 10 and 14 years were most sufferers. Per trap night density of mosquitoes in human dwellings was 204.3 and in cattlesheds--908.7, An. minimus accounted for 20.7% of total malaria vectors. INTERPRETATION & CONCLUSION: The results showed high malaria risk in the study villages. High vector density with high parity rate, poor socio-economic conditions, lack of awareness, poor sanitation and congenial atmosphere for mosquito proliferation are aggravating the malaria situation more complex in the study area.

Evaluation of botanicals as repellents against mosquitoes.

Repellent properties of three plant extracts--essential oil (steam distillate) of Zanthoxylum limonella (fruits), Citrus aurantifolia (leaf) and petroleum ether extract of Z. limonella (fruits) were evaluated as repellent against Aedes (S.) albopictus mosquitoes in mustard (Dhara) and coconut (Parachute) oil base under laboratory conditions. Three concentrations--10, 20 and 30% of the repellents were evaluated. Repellents in mustard oil afforded longer protection time against the bites of Aedes (S.) albopictus mosquitoes than those in coconut oil. At 30% concentration, 296-304 min protection time was achieved by the test repellents in mustard oil base while repellents in coconut oil exhibited 223.5-245 min protection time at the same concentration. Oil of Z. limonella gave the highest protection time against the bites of Aedes (S.) albopictus mosquitoes at all the concentrations than other herbal repellents tested both in mustard and coconut oil.

Formulation approaches for orally administered poorly soluble drugs.

Despite having pharmacodynamic or target activity, many drugs fail in the drug development process due to poor bioavailability, and presently marketed conventional dosage forms of poorly soluble drugs employ high doses leading to potential toxicity. The introduction of the Biopharmaceutic Classification System (BCS) has provided a basis to categorize drugs based on the two major parameters affecting absorption, solubility and permeability. Several techniques can be employed to enhance the absorption and bioavailability of poorly soluble and poorly permeable drugs based on the BCS concept. This article is an attempt to summarize the development of various formulation approaches that are currently employed to enhance bioavailability of orally administered poorly soluble drugs.

Comparison of oil-in-water emulsions manufactured by microfluidization and homogenization.

The purpose of this study was to compare drug-free model submicron oil-in-water (o/w) emulsions manufactured by high-speed homogenization and microfluidization. The study was aimed at evaluating the influence of these two manufacturing processes on the stability of the emulsions with respect to emulsifier concentration. Stability was defined in terms of dispersed droplet diameter growth over time. The study was also directed towards identifying the minimum emulsifier concentrations required by either processing method within the same model o/w systems to produce emulsions viable throughout the study period of three months. The Microfluidizer 110L was found to be more effective than the homogenizer in producing stable o/w submicron emulsions using triglycerides of caprylic/capric acid as the oil phase and combinations of emulsifiers (polyoxyethylene sorbitan oleate with high HLB and sorbitan monooleate with low HLB) at low emulsifier concentrations. Submicron emulsions prepared by the microfluidization process had smaller droplet diameters and exhibited less droplet diameter growth over time compared to high-speed homogenization. At emulsifier concentrations below 20% w/w, the droplet diameter or stability of the dispersed phase of the sub-micron emulsions prepared by either process was found to be dependent on the emulsifier content.

Field evaluation of herbal mosquito repellents.

Repellent properties of Zanthoxylum armatum DC. Syn. Z. alatum Roxb. (Timur), Curcuma aromatica (Jungli haldi) and Azadirachta indica (Neem) oils were evaluated against mosquitoes in mustard (Brassica sp.) and coconut (Cocos sp.) oil base and compared with synthetic repellent. Dimethyl phthalate (DMP) as standard. Timur and jungli haldi afforded better protection in the both the base at all the concentrations. Tepellents in mustard oil gave longer protection time than those in coconut oil. At 0.57 mg/cm2 concentration timur oil gave significantly higher protection both in mustard (445 min) as well as coconut oil (404 min) than the other repellents and DMP.

Role of Anopheles culicifacies during an outbreak of malaria in Gorubandha P.H.C., Assam.

Entomological investigation during an outbreak of malaria in Gorubandha PHC in Sonitpur district revealed unusually high density of Anopheles culicifacies followed by An.minimus. Parity rates of both the species were very high, 65% and 62.2% respectively. An. culicifacies was incriminated as malaria vector. Sporozoite rate recorded was 0.63%. Both the species were found susceptible to DDT. This substantiates the epidemiological observation which yielded 98% Plasmodium falciparum malaria out of 35.2% malaria positive cases. Incrimination of An. culicifacies means adding one more malaria vector to this region.

Field evaluation of repellency of a polyherbal essential oil against blackflies and its dermal toxicity using rat model.

In the present study we have evaluated the repellent activity of mixture of Curcuma longa, Zanthoxylum limonella and Pogostemon heyneanus essential oils in 1:1:2 ratio at 5%, 10% and 20% concentration against blackflies in northeastern India. Initially the essential oil mixture tested here has been found effective against Aedes albopictus mosquitoes. The average protection recorded in 20% concentration (170.56 ± 4.0; 95% CI = 162.09-179.02) was higher as compared to other two concentrations (F = 90.2; p<0.0001; df = 53). Percentage repellency and repellency index was found to be higher in 20% concentration (p ≤ 0.017). No appreciable clinical and behavioral signs were observed in the acute dermal toxicity using rat model. No changes were observed in biochemical profiles of treatment group animals. Similarly, no prominent lesions were observed in vital organs of treatment in both the sexes. The study concludes that tested repellent is safe for use and has multi-insects repellent property.

A cross sectional investigation of malaria epidemiology among seven tea estates in Assam, India.

In the present investigation, the epidemiology of malaria among seven tea estates of Nagaon and Udalguri districts of Assam, India has been described. A cross-sectional open study was carried out to understand the malaria epidemiology and associated risk factors among the tea tribes during March to September 2009. Out of 1,182 peripheral blood smears examined, 506 found positive for malaria (slide positivity rate, SPR = 42.8) with Plasmodium falciparum as predominant species. Dimakuchi tea estate was having highest SPR (P = 0.0275) and contributed more number of P. falciparum cases (P < 0.00001). Tea estates studied in both Udalguri and Nagaon districts were equally affected and the SPR recorded were 41.75 and 43.32% respectively. 154 malaria cases detected were having 'O' blood group but each blood group was found to have similar susceptibility of acquiring malaria infection (χ(2 ) = 3.603; P = 0.3076) and P. falciparum infection (χ(2 ) = 1.818; P = 0.6110). The SPR was highest among children more than 2 years of age group and variation in SPR among the age groups was statistically significant (χ(2 ) = 17.186; P = 0.0018). No gender biasing was observed in malaria distribution. Anemia was found associated with the infection among both the sexes. The findings suggest that tea estates are endemic for stable malaria transmission primarily due to P. falciparum and the prevalence rate decline with age, suggesting the development of protective immunity. Promising intervention measures could be able to reduce the malaria prevalence effectively in the study areas.

Diversity and seasonal densities of vector anophelines in relation to forest fringe malaria in district Sonitpur, Assam (India).

The prevalence and bionomics of known Indian malaria vector anophelines was studied in three forest fringe villages in Sonitpur district of Assam, India. Anopheles philippinensis/nivipes (36.8%) and An. annularis (25.6%) were the most abundant of the seven vector anopheline species recorded. Densities of vector anophelines in general were high during monsoon season and low during winter months. An. dirus s.l. was the most anthropophagic (91.6%) of all the species collected whereas, An. annularis, An. fluviatilis s.l. and An. varuna were predominantly zoophagic. The highest and the lowest slide positivity rates (SPR) was recorded during monsoon (36%) and winter (12.5%) seasons, respectively. SPR was positively correlated with vector anopheline densities (r = 0.902), which itself was found to be correlated with mean minimum temperature and relative humidity (RH).