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Wash resistance and field bioefficacy of PermaNet 2.0 nets, long lasting insecticidal nets, against mosquitoes were evaluated in Assam, northeastern India. After repeated hand washings at 12-day intervals a decline in the mosquito killing ability of PermaNet nets was noted (trend chi2 38.9, p < 0.0001), yet these nets retained good insecticidal efficacy for up to 15 wash cycles, producing a 72.5% mean mortality of An. minimus 24 hours after a 3-minute exposure in World Health Organization cones after 15 washings. Significantly fewer (p < 0.001) mosquitoes were captured in self-baited landing collections in houses equipped with PermaNet nets than in houses using untreated nets in the case of culicines (p < 0.001) but not with anophelines, including An. minimus. The use of PermaNet nets resulted in noticeably fewer bites from Culex pseudovishnui (68.5%) and Cx. quinquefasciatus (70%). Blood-feeding inhibition of mosquitoes in deliberately torn PermaNet nets was seen, indicating a protective effect for those sleeping under these nets. No serious adverse effects of the PermaNet nets were reported by users.

Anopheles (Cellia) philippinensis Ludlow and Anopheles (Cellia) nivipes (Theobald) are two closely related, morphologically very similar, mosquito species in the Annularis group, which play a supportive role in malaria transmission in north-east India. We amplified and performed sequence analysis for the internal transcribed spacer 2 (ITS2) locus of ribosomal DNA (rDNA) gene of morphologically confirmed specimens of these two species from the states of Assam and Nagaland. An. philippinensis and An. nivipes shared 85.2% sequence similarity and no intra-species variation was found in the nucleotide sequences of the two species. Overall, sequence data of the ITS2 marker revealed that both these species from north-east India differed by as much as have been reported from specimens of eastern Thailand.

A cross-sectional study was conducted to assess tobacco use (both smoking and non-smoked tobacco) and alcohol use among tea garden youths of Assam, India during the period 2002-2003. A total of 650 tea plantation youth age 15-24 years (255 males, 395 females) from eight randomly selected tea plantations, Dibrugarh District, Assam, were interviewed to collect information on alcohol and tobacco use using a pre-designed, pre-tested questionnaire. Nearly 59% of the respondents had no formal education. Fifty-eight percent of the youth used at least one substance and 27.4% were concurrent users of both alcohol and tobacco. The smoking rate was only 2.2% (4.7% in males, 0.5% in females). However, 52.5% of the study population used non-smoked tobacco (56.9% males, 49.6% females). The prevalence of alcohol consumption was 32.2% (43.9% males, 24.6% females). A higher rate of alcohol and tobacco use was found among the respondents who had no formal education or were school dropouts. A higher rate of alcohol and tobacco use were seen among respondents in whom both parents were illiterate. Working as a manual worker in the tea industry is significantly associated (p<0.01) with higher rates of alcohol and tobacco use. We recommend a vigorous campaign against tobacco and alcohol use among tea plantation youth to reduce the health risks associated with the use of these two substances.

This study sought to assess the knowledge and attitudes of young unmarried women regarding family size and sexually transmitted diseases, including HIV, in three residential regional institutes of northeastern India. The data is expected to help in reinforcing various methods of Information, Education and Communication (IEC) implementation. A representative sample of 574 female students, 16-25 years of age, were interviewed by a pretested questionnaire to assess their knowledge of the determinants of family size and sexually transmitted diseases. Of the participants, 48.43% stated that the suitable age for marriage is > 18 years old for women. More than half the respondents stated that the interval between child birth should be 3-5 years. Most of the respondents (96.17%) were of the opinion that both parents are responsible for determining the number of children. Knowledge of STDs and HIV was found in 91.8% and 74.04% of respondents, respectively.

Japanese encephalitis is one of the major public health problems in Assam, northeast India. We aimed to elucidated the clinical and epidemiological profile of the disease during several outbreaks in Assam in 3 consecutive years. Cerebro-spinal fluid and or serum samples of 348 out of 773 clinically-suspected viral encephalitis patients admitted to different hospitals during the period June to August of 2000 to 2002 were tested for detection of JE specific IgM antibody, employing MAC ELISA test at RMRC (ICMR), Dibrugarh. Diagnosis was confirmed in 53.7% patients with the ratios of 1.8:1 and 1.4:1 for male to female and pediatric to adult patients respectively. Most of the cases were pediatrics at the age of 7 to 12 years (34.2%). Fever (100%), altered sensorium (81.8%), headache (70.6%), neck rigidity (54.0%), abnormal movement (51.3%), exaggerated reflexes (48.1%), restlessness (44.9%), increased muscle tone (35.3%), convulsion (33.7%) and coma (20.9%) were the major clinical findings. The majority of cases (96.3%) were from rural areas. House surroundings close to water bodies, rice cultivation, association with pigs, and climatic conditions were environmental factors affecting the abundance of the potential mosquito vectors of the disease.

Mass de-worming targeted at socio-economically poor communities can be considered as an option for communities living in the tropical forests of Assam who do not have access to safe drinking water and proper sanitation, and consequently have a higher risk of suffering from geohelminthic infection and associated morbidity. A random sample of 265 subjects was included in this study (134 males and 131 females). The chemotherapeutic regimen followed was a single dose of albendazole 400 mg. Stools samples were collected in 10% formol-saline for detection of infection before treatment. Post-treatment stool samples were collected 10 to 14 days after treatment to determine the cure rate. Stool samples were again collected 3 to 6 months post-treatment to study the rate of reinfection. Multiple logistic regression was used to find possible associations between age, sex and treatment failure. The chi-square test was used wherever appropriate. The cure rates for Ascaris lumbricoides, Trichuris trichiura and hookworms were 70.8%, 68.7% and 93.0%, respectively. Logistic regression revealed that age was associated with treatment failure in A. lumbricoides infection. Re-infection rates after 3 months of successful treatment were 19.6% for A. lumbricoides, 30.9% for T. trichiura and 11.3% for hookworms. Six months post-treatment, the prevalence of re-infection was highest with T. trichiura (43.6%); followed by A. lumbricoides (35.3%). The rate of reinfection with hookworms was lower (11.3%) six months post-treatment. The rates of re-infection with A. lumbricoides and T. trichiura was higher in children below 15 years of age, compared with adults. Hookworm reinfection was higher in the adult age group (15 to 39 years). The rates of new infection in previously uninfected subjects were lower compared with the rates for re-infection.

Tea industry is a labor intensive agro-industry and filariasis is mostly localized among the tea garden workers in Assam. The workers live inside the gardens in colonies. Studies conducted in two cosecutive years revealed that among the host seeking Culex quinquefasciatus average infection rate was 4.6% and with 2.1 larvae per mosquito. The overall prevalence of infective mosquitos was 0.8% with average L3 load of 2.0 per mosquito. The probability of infected mosquitos surviving to have complete development of filarial larvae (13 days) was 0.17. The expectation of infective life was 1.416 days for man biting Cx. quinquefasciatus and the estimated adult survival rate of was 87.6%. It has been estimated that a total of 22,569 mosquito bites were received/man/year in tea garden environment out of which 182 bites/man/year were infective (0.806%). The monthly biting rate varied from 310-4,758.5 bites per man (mean 1,846 +/- 1,389.7 SD). Monthly transmission index of W. bancrofti filaria showed two periods of transmission. In both the year no infection was detected during February and March and infection rate remained low up to May (average infection in April 0.72% and in May 0.48%).

Temporal changes in the biting density and host-seeking periodicity of Culex quinquefasciatus, the vector of bancroftian filariasis, were studied for two years in the tea agro-ecosystem of Assam, India. Average biting density of the vector varied from 0.8/hour in December to 13.3/hour in March. Minimum temperature was found to have a limiting effect on the biting density of the vector mosquitos. Multiple regression analysis showed that the rainfall and minimum temperature were significant factors influencing biting density of this vector mosquito. The biting rhythm of Cx. quinquefasciatus was found to be nocturnal with two distinct peak periods of biting activity. The first peak was around 19.00 to 20.00 hours and the second peak period was around 22.00 to 23.00 hours. Biting activity however was seen throughout the night with declining trend as the night proceeded.

105 workers of 29 roadside restaurants along a highway in Assam were interviewed for their habits, educational status and were examined for their hygienic status and presence of communicable diseases (STDs,TB etc). Most of them were young, males with 40% literacy; more than half were unmarried. About 30% of them were alcoholic and smokers and 2.9% were addicted to cannabis. The hygienic conditions of the workers were poor. More than one third had sexual contact with multiple sex partners or commercial sex workers and 2% were engaged in homosexual activity. Most of them did not use condom. 25.7% of them had genital lesions suggestive of sexually transmitted disease, 11.8% showed gram negative diplococci in urethral smears and 5.1% were VDRL reactive. Skin infections followed by gastrointestinal disorders and respiratory tract infections were other prevalent problems. 70.6% were positive for intestinal parasites and 22.2% were sputum positive for acid fast bacilli. However all the collected blood samples were negative for HIV.

A study on tobacco use was carried out in Aizawl district of Mizoram, India, to assess the prevalence and pattern of tobacco use. An area served by two Sub-health Centers representing town and village population were selected for a household survey. 375 people (age 10 years and above) were interviewed about their habits of taking tobacco. Use of tobacco was high among males (56.6%) and females (45.7%), but the high prevalence of smoking among males (42.3%) and chewing among females (27.9%) indicates the existence of sex differences in tobacco use pattern. Age and occupation had significant association with tobacco use but influence of education was very low and its association was not significant. Mean age for start of tobacco chewing and smoking for males and females varied significantly. However, the mean age of start for adolescent and young age (10-29 years) tobacco users was 17.2 years (SD +/- 2.3). Though there are some limitations to this study, these findings revealed differential patterns of tobacco use which is valuable information for prevention effort.

Surveys were conducted in some townships along the national highways and trunk roads of northeast India to detect breeding of Aedes mosquitos in used/waste tire dumps piled outdoors by the tire repairing shops during summer season of 1996-1997. The breeding of both the potential vectors of dengue, viz. Aedes aegypti and Ae. albopictus were detected, prevalence rate being in the range of 30.0-88.0 (CI = container index value). The preponderance of Ae. aegypti was considerably much higher than that of Ae. albopictus and all the urban and semiurban areas coming up along the side of the roads were observed to be infested with Ae. aegypti. With respect to transmission of dengue, this study clearly indicates that waste tire dumps in every urban agglomeration should receive primary attention in view of their relative contribution to the abundance and dispersal of these vector mosquitos.

Longitudinal surveys at monthly frequency were carried out during 1995-1996 in a forest fringed village of district Dibrugarh, Assam to decipher the breeding and day resting habitats of Anopheles dirus. It regularly bred in small, shallow, rain filled, transient, shady or partly shady puddles/ground pools in the rainy months and in the perinneal streams in the adjoining forest of the village during dry months. In pools, the degree of interspecific association (0.238 +/- 0.174) and index of association (0.428) of An. dirus breeding was highest with Aedes caecus. An. dirus was completely exophilic and rested during day time in the forest mostly on tree trunks upto the height of 4-5 feet from the ground in dark moist niches avoiding direct sun light.

A total of 395 drug addicts from Nagaland, India during 1992-1993 were studied. Of these, 331 (83.8%) were primary abusers of heroin. Mean age of the group was 21.8 years +/- SD 3.84. Of these 5.2% were females. The majority were unmarried (92.1%) and 52% had completed 10 years of schooling. Drug-related school dropout rate was 72.8%. Unemployment was predominant (90.3%) in the group, of which most were never employed. Christianity was the main religion (90.9%) of the group. The mean age at first use of heroin was 17.6 years +/- SD 3.68. The mean duration of dependence on heroin was 4.4 years +/- SD 2.8. Heroin was injected by 80.9% subjects. Friends were the main source of introduction. Concurrent use of tranquilizers and codeine containing cough syrups was prevalent in the event of a short supply of heroin. The involvement of young, unemployed, unmarried persons in heroin addiction; widespread prevalence of the injection route and needle sharing; chronicity of heroin dependence; paucity of specialized treatment avenues and proximity to the Golden Triangle facilitating illicit traffic, have contributed to emergence of heroin addiction as a major public health problem in Nagaland.

Temporal changes in the abundance of host-seeking, potential Japanese encephalitis (JE) vector mosquitos and the role of some ecological factors that are modulating the abundance of vector mosquitos were studied. Vector surveillance was conducted for one year in 4 JE prone villages of Dibrugarh, Assam. Among potential JE vectors, the most abundant mosquito was Culex vishnui s.s. comprising about 22.32%. Maximum density of the mosquito was found during the month of April and another peak was observed in the month of September. The influence of meteorological factors on the abundance of JE vectors was found to vary from species to species. The final multiple regression equations (after variables were selected using STEPWISE procedure) consisted of a combination of linear, quadratic, cubic and interactive ecological variables and accounted for 25-98% of the variations in the abundance of JE vector mosquitos. Complex interactions among environmental factors, such as minimum and maximum temperature, rainfall and flood level are involved in modulating the seasonal abundance of mosquitos. A time lag is involved before a cause and effect relationship is established between environmental parameters (independent variables) and entomological variables (dependent variables). Inundation caused by flooding is favorable for mansonioid mosquito species whereas it has an adverse effect on non-mansonioid mosquito species.

The feeding behavior of Anopheles dirus, the forest breeding, major malaria vector in northeast India was studied. The analysis of blood meals collected from this mosquito revealed that the species was highly anthropophilic in nature, the anthropophilic index being 90.5. The results of bait collection on human and cattle bait also confirmed its biting preference for human hosts. The species was observed to land on human bait throughout the night, showing prominent biting time at 20.00-21.00, 23.00-24.00 and 02.00-03.00 hours during the study period.