Malaria control in a forest camp in an oil exploration area of Upper Assam

BACKGROUND

Assam, in north-east India, is extremely rich in hydrocarbon deposits and the oil industry is the major contributor to its economy. A large number of oil fields and related installations in Assam are located in forest areas or on their fringes where malaria is a serious problem among field staff and security personnel, adversely affecting oil production. We carried out an operational research study for one year in a forest-based industrial security camp of Dibrugarh district and developed an effective malaria control strategy for such areas.

METHODS

The specific strategy was formulated and implemented after taking into account the local epidemiology of malaria, vector's ecology and malaria risk behaviour of the camp inmates. The strategy was based on reducing the man-vector contact, using deltamethrin-treated mosquito nets in conjunction with mosquito repellent cream and weekly chemoprophylaxis with 300 mg chloroquine. The impact of the strategy was monitored entomologically and epidemiologically for one year after implementation.

RESULTS

The mean landing rate of Anopheles dirus, the vector mosquito in the camp area, was 5.03 per person per night during the monitoring. In spite of such a high density of the vector, the man-vector contact was effectively checked by the intervention measures adopted. As a result, the incidence of malaria in the camp was reduced by > 90% as compared to previous years and the number of malaria cases came down from 6.7 per 1000 man-nights in 1998-99 to 0.06 in 2000-01. Mortality due to malaria was completely eliminated.

CONCLUSION

Control of malaria should be based on the local determinants of transmission. The use of insecticide-treated mosquito nets in conjunction with a mosquito repellent cream is a good intervention for controlling Anopheles dirus-transmitted malaria in the forests of north-east India. The control module developed on the principle of reducing man-mosquito contact is easy to implement, cost-effective and replicable in similar forest-based locations.

Occurrence of Culex (Lophoceraomyia) quadripalpis, Culex (Lophoceraomyia) mammilifer, and Uranotaenia (Pseudoficalbia) novobscura in Assam, India

Culex (Lophoceraomyia) quadripalpis is recorded for the 1st time in India. Collections of Culex (Lophoceraomyia) mammilifer and Uranotaenia (Pseudoficalbia) novobscura are new records from Assam in northeastern India.

Clinical outcome and neurological sequelae in serologically confirmed cases of Japanese encephalitis patients in Assam, India

We report the clinical outcome and prognostic factors in 39 cases of childhood Japanese Encephalitis admitted to a tertiary hospital of Upper Assam and followed up for 421 days in the community. The mortality rate was 20.5% in our study. The mean GCS (9.97 +/- 0.91) was higher in surviving cases than the fatal cases (GCS 7.5 +/- 1.78) at admission. The fatal cases died within 4.75 +/- 3.19 days in the hospital. All the patients had low BMI (surviving cases 13.54 +/- 2.3; fatal cases 12.05 +/- 0.12) and were anemic. Cerebrospinal fluid (CSF) was clear in 91.4% cases but pressure and protein content were increased in all cases. About 10% cases had parkinsonian features at the time of discharge. Residual symptoms remained in about one third of cases even after 421 days.

Role of dietary habits in the development of esophageal cancer in Assam, the north-eastern region of India

The etiology of esophageal cancer remains largely unknown. In recent years, the role of dietary habits in the development of esophageal cancer has received much attention. Prevalence of esophageal cancer in Assam is highest among all the states of India. To identify the possible risk factors, a hospital-based case-control study was conducted with 502 cases and 1,004 controls. "Kalakhar," a unique and locally made food item, has emerged as a significant risk factor (odds ratio = 8.0, 95% confidence interval = 5.1-11.5, p < 0.001). Consumption of very spicy foods, hot foods and beverages, a diet containing high amounts of chili, and leftover food was positively associated with the risk of esophageal cancer. Green leafy vegetables and fruits were protective for esophageal cancer. The risk factors associated with consumption of locally prepared food items, e.g., kalakhar, and some dietary practices did not decrease, even after adjustments with different confounding factors. However, further studies are required to conclusively implicate these factors in causation of esophageal cancer.

Differences in blood pressure level and hypertension in three ethnic groups of northeastern India

A cross sectional study on hypertension was done on 294 subjects aged 30 years and above. 150 households were selected randomly representing 50 households from each locality inhabited exclusively by the rural Mizos, indigenous rural Assamese and the tea-garden workers respectively, in the northeastern region of India. Blood pressure was measured by sphygmo-manometer in sitting posture. Anthro-pometric measurements were taken using standard procedure for measuring height, weight, waist and hip girth. Information on age, sex, ethnicity, literacy, alcohol intake, smoking pattern, physical activity, occupation, amount of salt consumption was collected using a standard and pre-tested questionnaire. Significant differences were observed in both the systolic and diastolic blood pressure levels among the three different ethnic groups selected for this study (p < 0.0001). Multiple regression analyses indicated that in Mizos, age, waist circumference and alcohol intake were independently associated with increase in systolic blood pressure whereas smoking was found to be negatively associated with systolic blood pressure (R2 = 0.391, p < 0.001). Factors, which were the best predictors of diastolic blood pressure, were age and body mass index [(kg/m2) (R2 = 0.227, p < 0.001)]. In the rural Assamese population, the best predictors of systolic blood pressure were age and waist circumference (R2 = 0.263, p = 0.018). For the diastolic blood pressure, age, alcohol intake and body mass index were important correlates (R2 = 0.131, p < 0.001). In the tea garden community, important predictors of systolic blood pressure were age, gender and marital status (R2 = 0.187, p < 0.001). On the other hand, age and alcohol intake were best predictors for diastolic blood pressure (R2 = 0.09, p < 0.001).

Hypertension and its risk factors in tea garden workers of Assam

BACKGROUND

Hypertension is emerging as a major public health problem in India. The diversity and heterogeneity of distribution of the population makes it difficult to arrive at the precise prevalence. In Assam, reports from hospitals in tea gardens reveal a high prevalence of hypertension among workers in tea gardens. However, no systematic study has been carried out in this population.

METHODS

We selected, by systematic sampling, 1015 individuals (512 men and 503 women) 30 years or more in age, who were interviewed and clinically examined for hypertension. Blood pressure of all the study participants was measured using a standardized technique. Crude and adjusted odds ratios were estimated by unconditional simple and multiple logistic regression analyses. Mantel-Haenszel chi2 analysis was also used to test for the association of potential risk factors with hypertension after controlling for co-variables in a stratified analysis. Risk factors considered for hypertension included age, gender, marital status, occupation, alcohol consumption (locally prepared), extra salt intake, smoking history, khaini (a form of tobacco quid containing a mixture of tobacco and lime) intake, body mass index and waist-hip ratio.

RESULTS

The overall prevalence of hypertension was 60.8%. Increasing age, consumption of locally prepared alcohol, intake of extra salt in food and beverages and the habit of taking khaini were found to increase the risk of hypertension. Multivariate logistic regression models showed that the independent determinants of hypertension were age, gender, consumption of locally prepared alcohol and intake of extra salt. Gender-specific and age-stratified analyses showed the association of increased risk with intake of khaini in women only, while consumption of locally prepared alcohol was an important risk factor for hypertension in both men and women.

CONCLUSION

The disease burden of hypertension among workers in tea gardens is large, despite the community not being obese. Interventions directed at these workers as well as studies to determine the reasons for the high prevalence of hypertension are required.

Physico-chemical characteristics of breeding habitats of Anopheles dirus (Diptera:Culicidae) in Assam, India

Larval ecology of Anopheles dirus, the main vector of forest malaria in north-eastern region of India, was studied in relation to physico-chemical characteristics of its breeding habitats in a rain forest area of Assam, India. Shady stream side pools, positive for the breeding of An. dirus, had significantly higher amounts of total hardness (P < 0.024) in comparison to negative pools of similar type. When compared with An. dirus negative breeding habitats, in hot-wet as well as in cool-dry seasons, An. dirus positive shady ground pools showed higher mean values of total alkalinity, hardness and chloride content, whereas lower pH, dissolved oxygen along with higher total alkalinity and hardness were possessed by An. dirus positive stream side pools. Specificity of breeding habitats of An. dirus in relation to its ecology has been discussed.

HCV activity in an isolated community in north east India

Prevalence of anti-HCV among the people at risk and general population were reported across the globe. We investigated HCV activity among the members of "Lisu" community settled in a remote and isolated area of Changlang District, Arunachal Pradesh during 1999-2000. The families were scattered with 380 households. Blood samples were collected from 76 (35 males and 45 females) apparently healthy individuals from randomly selected 10% families. Sera were processed for detection for antibody to HCV by using 3rd generation ELISA kit. All the persons were within the age of 18-98 years and 75% of them were uneducated and 92% were cultivators. The prevalence of anti-HCV was found to be very high (7.89%). Since the HCV activity is high in an isolated community, transmission dynamics study will be interesting for this epidemiologically important viral disease.

Betel nut and tobacco chewing; potential risk factors of cancer of oesophagus in Assam, India

Cancer of the oesophagus is the most commonly diagnosed cancer in males in Assam, in north-eastern India, and ranks second for females. The chewing of betel nut, with or without tobacco and prepared in various ways, is a common practice in the region and a case-control study has been designed to study the pattern of risk associated with different ways of preparing and chewing the nuts. 358 newly diagnosed male patients and 144 female have been interviewed together with 2 control subjects for each case chosen at random from among the attendants who accompanied patients to hospital. There were significant trends in risk ratios associated with the frequency of chewing each day, with the duration of chewing in years and with the age at which the habit was started that were apparent for both males and females and which remained significant after allowance was made for other known risk factors, notably tobacco smoking and alcohol consumption. The adjusted ratios, in comparison with non-chewers, were 13.3 M and 5.7 F for chewing more than 20 times a day, 10.6 M and 7.2 F for persons who had chewed for more than 20 years and 10.3 M and 5.3 F for those who had started before the age of 20. Among the different combinations of ingredients that were chewed the adjusted odds ratios were highest for those who had been using fermented betel nut with any form of tobacco (7.1 M and 3.6 F). The risk associated with tobacco smoking and alcohol consumption, which are high in some parts of the world, were less in Assam than those associated with the chewing of betel nut.

Transmission of bancroftian filariasis in tea agro-ecosystem of Assam, India

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%).

A multicentric study with arteether in patients of uncomplicated falciparum malaria

Two hundred and sixty seven patients of uncomplicated P. falciparum malaria completed study in a multicentric phase III clinical trial of Arteether. Arteether was given intramuscularly in a dose of 150 mg daily for three consecutive days. Each patient was followed upto 28 days of alpha, beta arteether therapy. The cure rate was 97% with fever clearance time between 1-7 days (24-168 hours) and parasite clearance time between 1-3 days (24-72 hours). Parasite reappearance rate was found to be 3% and reported at only three of the centres. Following the treatment no adverse effect was observed on haematological, biochemical and vital clinical parameters.

Antimicrobial susceptibility pattern among methicillin resistant Staphylococcus isolates in Assam

Prevalence of methicillin resistant Staphylococcus aureus from a referral hospital in Assam was studied. Methicillin resistance among the Staphylococcus aureus isolates was 52.9% and 15% among the coagulase negative staphylococci. Resistance to all antibiotics tested among the methicillin resistant and methicillin sensitive staphylococci was found to be 23.2% and 6.6% respectively. Higher resistance to multiple antibiotics in methicillin resistant strains as compared to methicillin sensitive strains was found to be statistically significant. Ciprofloxacin resistance among the strains was still lower in comparison to the findings from other parts of the country.

Demonstration of Epstein-Barr virus antibodies in serum of patients with nasopharyngeal carcinoma

A total of eighty six blood samples (17, 19 & 50 of nasopharyngeal carcinoma, oesophageal cancer and normal healthy control respectively) were collected from Naga Hospital, Kohima, Nagaland and B. Barooah Cancer Institute, Guwahati, Assam and were processed for the detection of EBV-IgG antibody using Elisa test. The results showed that EBV positivity is higher among NPC patients as compared to oesophageal carcinoma patients and/or healthy control. The data also indicated that EBV antibody titre is significantly higher among NPC cases as compared to control.

Risk factors of malaria in the fringes of an evergreen monsoon forest of Arunachal Pradesh

BACKGROUND

The forested hilly and foothill regions of north-east India are highly endemic for malaria and have a distinct epidemiological pattern. Nearly half the reported cases of malaria are from these areas. A knowledge of the risk factors in this eco-geographic entity may be helpful in formulating a specific control strategy. Hence, we conducted a community-based epidemiological study in a hilly, forested terrain of Arunachal Pradesh and examined different socio-demographic factors to identify those predisposing to the occurrence of malaria, especially Plasmodium falciparum infection, in such areas.

METHODS

Four epidemiological surveys were carried out during 1997 in 7 villages located at the fringes of a forest (total population: 1177) under Nompong Primary Health Centre of Changlang district, Arunachal Pradesh. Blood slides were collected randomly from the inhabitants, irrespective of their fever status, ensuring at least 50% coverage. One hundred and thirty-four microscopically confirmed Plasmodium falciparum cases were identified and 536 controls were randomly selected from the list of uninfected inhabitants. Relevant socio-demographic information was obtained from both cases and controls. The data were analysed by simple and multiple logistic regression using the unconditional maximum likelihood method.

RESULTS

Factors which were found to be strongly associated with Plasmodium falciparum malaria on univariate analysis were age, ethnicity, village of residence and accessibility to the nearest health care facility. However, in multiple regression analysis, after controlling for the effects of confounding variables, the only risk factor identified was accessibility to the nearest health care facility (adjusted odds ratio: 4.5; 95% CI: 1.8-11.3; p < 0.0001 for those at a distance of 2-8 km and adjusted odds ratio: 11.1; 95% CI: 4.1-30.0; p < 0.0001 for those > 8 km away).

CONCLUSION

Distance, particularly non-motorable distance, from the place of residence to the nearest health care facility was a major risk factor for malaria in this hilly forested terrain. This indicates the need for special efforts to detect cases early and institute treatment promptly in such areas of the north-eastern region, so as to reduce the morbidity and mortality of malaria.

Bronchopulmonary candidiasis in a tertiary referral hospital of Assam, India

One hundred patients with chronic chest infection suffering for more than three months admitted into a tertiary referral Hospital, northeast India were examined for pulmonary mycoses. The morning sputum samples in 3 consecutive days with a throat swab of each patient were examined for detection, isolation and identification of the fungus. Study showed Pulmonary candidiasis in 50% of the patients where Candida albicans were having highest incidence of association followed by 5 other species of Candida. Pre-existing conditions like pulmonary tuberculosis, bronchogenic carcinoma, lung abscess, bronchial asthma make the lungs prone to be invaded by the candida species. Long term antibiotics and steroids therapy was found to be associated with pulmonary candidiasis. Other conditions like irradiation treatment, malignancy, diabetes mellitus and malnutrition were also found to be the predisposing factors which influence bronchopulmonary candidiasis.

Prevalence of Trichuris trichiura in relation to socio-economic & behavioural determinants of exposure to infection in rural Assam

BACKGROUND & OBJECTIVES

Stunting, anaemia, and the poor level of mental development are known to be associated with Trichuris trichiura infections. However, no information is available on the socio-environmental predictors relevant to Trichuris infection in rural communities. Whilst geohelminthic infections per se is an inevitable consequence of poor personal hygiene and household sanitation, the importance of specific factors in the epidemiology of Trichuris infection have not been formally investigated. The objective of this study was to explore, quantify and study different socio-environmental risk factors and find out their possible interaction vis-a-vis T. trichiura infection.

METHODS

The study population consisted of 244 children (aged 15 yr and below) and 336 adults selected from 144 randomly selected households belonging to three villages of upper Assam. The prevalence rate ratio (PRR; = relative risk) and 95 per cent confidence interval (CI) were calculated. Univariate, multivariate analysis using Cox's proportional hazards regression assuming constant risk period and a tree-based risk factor analysis, were used.

RESULTS

In the overall multivariate model, open field defaecation, large family size, and three or more children in the household were found independently associated with Trichuris infection. Gender specific analysis revealed that in females the age was also independently associated with increased risk of infection whereas in males, earth flooring was the most significant risk factor independently associated with the risk of Trichuris infection. Tree-based risk factor analysis indicated interaction between defaecating habits of people and the source of drinking water.

INTERPRETATION & CONCLUSIONS

Installation of pit latrines (if not sanitary latrines) together with provision for safe drinking water and the construction of cement floors would probably reduce community prevalence of T. trichiura effectively.

Mosquito fauna and malaria vectors in Jairampur, district Changlang, Arunachal Pradesh

In an entomological study, covering three biotopes like village, panikheti (wet rice cultivated land) and urban agglomeration, a total of 35 species of mosquitoes in eight genera were recorded in Jairampur area of Arunachal Pradesh. Two mosquito species--Orthopodomyia anopheloides and Tripteroides indicus were recorded for the first time in Arunachal Pradesh. Anopheles dirus and An. minimus, the two well-known malaria vectors were encountered in the study along with several potential vector species like An. annularis, An. culicifacies, An. maculatus group and An. philippinensis/nivipes. The diversity of mosquito species as well as the man-vector contact was maximum in the panikheti and minimum in the village biotope.

Epidemiology of malaria outbreak (April/May, 1999) in Titabor Primary Health Centre, district Jorhat (Assam)

An investigation was undertaken of a malaria outbreak in the Primary Health Centre Titabor, district Jorhat, Assam during May/June 1999. The fever rate in the community since March 1999, was 44.4 per cent with an average case load of 2.5 per family. The fever cases peaked in the third week of May. Slide positive and slide falciparum rates in mass blood survey, in the study village were 16.1 and 14.5 per cent respectively with 90 per cent infection of Plasmodium falciparum. Males (SPR 17.5%) suffered relatively more than females (SPR 14.7%). Malaria prevalence was significantly less in individuals above 15 yr of age (SPR 11.0%) as compared to those below 15 yr (SPR 22.9%). Prevalence of malaria as well as mosquito densities in different clusters of the village were inversely related to the distance from the forested Naga hills. Anopheles minimus and A. dirus were collected in good numbers with comparatively higher densities of the former. Several factors like unusual climatic conditions, inadequate surveillance, unsatisfactory laboratory services and inadequate indoor residual insecticide spray were instrumental for the outbreak.

Risk factors for cancer nasopharynx: a case-control study from Nagaland, India

BACKGROUND

A high incidence of nasopharyngeal carcinoma has been reported from Nagaland, though it is considered to be a rare neoplasm in India. No case-control study to identify the risk factors of cancer nasopharynx has been conducted in this region. This study was undertaken to identify dietary and environmental risk factors for nasopharyngeal carcinoma relevant to this region.

METHODS

A matched case-control study using neighbourhood controls was conducted. For each of the 47 cases identified, 2 apparently healthy neighbourhood controls were matched for age, sex and ethnicity. All information on dietary, environmental, social and demographic factors was collected. Univariate and multivariate logistic regression analysis using maximum likelihood method was used to analyse data.

RESULTS

Consumption of smoked meat was found to be the risk factor for nasopharyngeal carcinoma (adjusted odds ratio = 10.8; 95% CI 3.0-39.0). History of using herbal nasal medicine was also found to be associated with nasopharyngeal carcinoma (OR = 21.9, CI = 6.8-71.4). However, exposure to a smoky atmosphere, betel-nut chewing, use of smokeless tobacco products, smoking and drinking habits were not found to be associated with nasopharyngeal carcinoma.

CONCLUSION

This study reveals an association of nasopharyngeal carcinoma with consumption of smoked meat in Nagaland. The use of herbal nasal medicine seems to be an additional risk factor for nasopharyngeal carcinoma in Nagaland and needs further assessment.

Temporal variations in biting density and rhythm of Culex quinquefasciatus in tea agro-ecosystem of Assam, India

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.

Prevalence of communicable disease among restaurant workers along a highway in Assam, India

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.

Iodine status of food and drinking water of a sub-Himalayan zone of India

Iodine content of rice (42) and drinking water (108) from a goitre-endemic belt of Assam, a sub-Himalayan zone of India, was evaluated. Iodine content of staple food (rice) and drinking water was found to be poor. Mean iodine content of rice was found to be 11.8 +/- 7.3 micrograms/100g. Lower level of iodine was also observed in drinking water samples (mean of 1.52 +/- 0.48 micrograms/l).

Antibodies reacting with chloroquine in human sera

Presence of antibodies in human sera reacting with chloroquine (CQ) was demonstrated from a malaria endemic belt. The study groups consisted of 53 healthy volunteers, receiving regular chloroquine prophylaxis [2 tablets of CQ (150 mg)/wk, single dose], 105 individuals with a history of frequent CQ intake for any febrile attack and 95 individuals from a non-endemic area who had neither a history of malaria nor of previous consumption of CQ. Sixty six per cent individuals taking regular prophylactic chloroquine and about ten per cent of those with a history of taking frequent chloroquine due to febrile illness in the malaria endemic area showed antibodies reacting to chloroquine. However, antichloroquine antibodies were either insignificant or nondetectable in serum samples collected from persons without any history of chloroquine intake. The results indicate a possible interaction of CQ in vivo.

Epidemiological importance of younger age group during malaria epidemic in PHC Tamulpur, Assam

An investigation of a malaria epidemic was carried out in Tamulpur Primary Health Centre, district Nalbari, Assam during April 1995. The analysis revealed that children between 3 and 12 years of age who were treated and who recovered clinically from fever during the epidemic were instrumental in the progression of the epidemic by acting as Plasmodium falciparum gametocyte reservoirs. Special efforts are required for treatment of children below 12 years during an epidemic.

A study of neonatal deaths in the tea gardens of Dibrugarh district of upper Assam

A total of 2432 live births and 46 stillbirths were studied in some of the tea gardens of Dibrugarh district of upper Assam. The neonatal mortality rate was 46.5 per 1000 live births per year. Immaturity (21.2%), fever/sepsis (13.3%), breathing disorder (12.4%), neonatal tetanus (11.5%) and neonatal diarrhoea (8.8%) accounted for most of the neonatal deaths. There were 42.9% low birth weight infants and this was associated with 92.8% of total neonatal deaths and 34.3% of preterm babies were associated with 90.7% of neonatal deaths. The case fatality rate among low birth weight and preterm babies was 9% and 11% respectively. High risk of neonatal deaths had been found among the neonates in case of no maternal immunisation, delivery attended by untrained person and newborn care at home.

Bancroftian filariasis in Namrup tea estate, district Dibrugarh, Assam

Filariasis survey in a randomly selected tea estate of district Dibrugrah revealed 6.7% infection of Wuchereria bancrofti in labour population with microfilaria (mf) rate of 7.6% in males and 5.9% in females. The mf rate increased progressively with the age which however, dropped in 31-40 age group of males and in 41-50 age group of females. Chronic filariasis diseases rate was 2.7%. The involvement of genitals in manifesting chronic filariasis was significantly higher than of the lower extremities. Infection and infectivity rates in the vector mosquito, Culex quinquefasciatus were 6.1% and 4.6% respectively with mean L3 load per infective mosquito of 8.5. Drains, land, peridomestic ditches were chief breeding habitats of Cules quinquefasciatus in the tea estate.

Long-term effect of diethylcarbamazine citrate on microfilaraemia status in treated individuals

Follow up of microfilaraemic individuals infected with Wuchereria bancrofti at five years after treatment was carried out in a tea workers population. Diethylcarbamazine citrate in the dose schedule of 72 mg/kg body weight given in equal daily doses over a period of 21 days cleared 51.6 per cent microfilaraemic individuals five year post-treatment. Eighty five subjects were successfully followed and among these, 10 (11.8%) showed increase in mf counts, 31 (36.4%) showed reduction but remained microfilaraemic and 44 (51.8%) became amicrofilaraemic. The age and sex of the host had no significant effect on the clearance of mf. Persistence of a relatively stable low number of mf in treated individuals is more likely due to survival of one or more female worms after the therapy or due to reinfection which could not be ruled out in the present study. Overall, findings indicated that diethylcarbamazine citrate appeared to give a long-term benefit to treated individuals.

Investigation on malaria vectors and mosquito fauna in south Tripura district, Tripura state

In an entomological study in South Tripura district of Tripura state during June 1998, a total of 31 species of mosquitoes belonging to eight genera were recorded. Among the known malaria vectors in India, Anopheles annularis, An. jeyporiensis, An. minimus, An. philippinensis/nivipes and An. varuna were collected but none of them could be incriminated. During the survey, Aedes pallidostriatus and Malaya genurostris were recorded for the first time in the north-eastern region and Tripura state respectively. Presence of host seeking An. minimus in light-trap collections indoors and its absence during morning indoor resting collections indicated the probability of some degree of exophilic behaviour of An. minimus population in Tripura.

Larval ecology and mosquito fauna of upper Brahmaputra valley, northeast India

Ninety-one mosquito species in 15 genera were collected from 22 habitat types of Upper Brahmaputra valley in Assam and bordering areas of Arunachal Pradesh. Nineteen species have been recorded for the first time in Assam including seven first records from the northeast region and three first country records. Jaccard's coefficient was used to quantify the similarity between 13 different geographical localities surveyed on the basis of their mosquito fauna. Group average sorting (UPGMA) cluster analysis was used to find out relationship between Jonai, Dhemaji, Dibrugarh, Tinsukia and north Lakhimpur (study zones) on the basis of their mosquito community. Immatures of three malaria vectors incriminated from the northeast India, viz. Anopheles dirus, An. minimus and An. philippinensis were collected exclusively from forest areas. Fourteen potential vectors of Japanese encephalitis incriminated from elsewhere in India were collected during the study.

Aetiology of nasopharyngeal carcinoma. A review

The present overview is based on recent available information on nasopharyngeal carcinoma (NPC) from various parts of the world including India. The available data suggests that NPC is a rare tumour in most parts of the world. But the incidence is higher in China and South East Asia and also among the Chinese wherever they have migrated. NPC is also relatively higher especially among the mongoloid group of the people in the North Eastern Region of India as compared to other parts of the country. The distinct geographical and ethnic distribution of NPC have stimulated much research to find out its etiology. The results suggest that Epstein Barr Virus (EBV) infection and genetic susceptibility are the constant aetiological factors for the higher incidence of NPC among various ethnic groups while other factors such as ingestants and inhalants may depend on the distinct dietary practices and living environment adopted by various ethnic groups in different geographical region of the world.

A note on the occurrence of Culex (lophoceraomyia) peytoni and Heizmannia (Heizmannia) reidi (Diptera: Culicidae) in Assam, India

Culex (Lophoceraomyia) peytoni Bram and Rattanarithikul is recorded for the first time from mainland India and Heizmannia (Heizmannia) reidi Mattingly for the first time from Assam, in northeast India.

Distribution of potential dengue vectors in major townships along the national highways and trunk roads of northeast India

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.

Incrimination of Schistosoma spindale as a causative agent of farmer's dermatitis in Assam with a note on liver pathology in mice

Cercarial dermatitis of paddy field workers in Assam is very common. However, it is not known which species of animal schistosomes, is its causative agent in Assam. Studies in two dermatitis affected villages of Dibrugarh district revealed that cercariae of Schistosoma spindale were involved in its aetiology. Indoplanorbis exustus was the only snail species found infected with apharyngeate brevifurcate schistosome cercarie. Experimental infection of the laboratory animals with the dermatitis causing schistosome cercariae revealed that duckling and chicken were refractory to infection. However, Swiss albino mice were successfully infected. The number of adult flukes per infected mice ranged from 6-321 (mean intensity = 68.1; S.D. = +/- 112.96). Histopathological study of infected mice liver revealed that there was mild inflammation of infected portal triads towards the presence of male flukes in the intra hepatic portal vessels. Kuppffer cells showed hyperplasia and contained large amounts of black pigment. No eggs or egg granulomas were detected in the liver parenchyma. There was no evidence of thrombophlebitis, septal fibrosis or pipe stem fibrosis.

Tobacco use in Mizoram, India: sociodemographic differences in pattern

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.

Seasonal prevalence of Anopheles dirus and malaria transmission in a forest fringed village of Assam, India

Seasonal abundance of Anopheles dirus (s.l.) and malaria prevalence in an isolated forest fringed village was monitored at monthly intervals during August 1995 to July 1996. An. dirus was the only vector species detected during the study period. Its density pattern showed distinct seasonality with the peak occurring in the month of July and very low number during cool dry months. Positive correlation (r = 0.721) was found between the density of An. dirus and the amount of rainfall occurring two weeks prior to the collections. Overall sporozoite rate of 1.6% and parous rate of 64.7% were found in the study. Malaria transmission closely followed the density pattern of An. dirus and was seasonal with slide positivity rate and P. falciparum percentage of 47 and 83% respectively. Mean malaria prevalence was higher (p < 0.05) in females.

Breeding and day resting habitats of Anopheles dirus in Assam, India

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.

Human distomatosis due to Fasciola hepatica infection in Assam, India

A seven year old girl in a rural area of Upper Assam was found to be infected with Fasciola hepatica. The girl gave history of eating watercress. Besides the presence of eggs in the stools, her liver was enlarged and tender. Liver function tests revealed hepato-biliary involvement with increase in serum AKP and ALT. Ultrasonography revealed presence of adult fluke in gall bladder, and a marginal thickening of gall bladder wall. However, the echo pattern of her liver parenchyma was normal. The case is reported for its public health significance and is a maiden report from north eastern India.

Biting behaviour and biting rhythm of potential Japanese encephalitis vectors in Assam

Studies on biting behaviour and biting cycles of medically important mosquitoes were carried out in Madhupur village and Tarajan tea estate of upper Assam. Collections were made off human baits outdoors and indoors and off cattle bait outdoors from August 1991 to July 1992. Human bait collections were performed using the 'stationary direct bait' technique. A total of 9,072 adult host seeking female mosquitoes representing 26 species and 5 genera were collected off baits of which 36.9% were collected off human baits and the rest from cattle. All mosquitoes were primarily zoophilic, although significant numbers were collected biting man outdoors. Biting preferences of important Japanese encephalitis (JE) vectors for man and cattle were studied using outdoor man:outdoor cattle ratio (attraction ratio = AR). Culex quinquefasciatus was attracted towards human baits the most (AR = 8.1:1), followed by Cx. bitaeniorhynchus (AR = 1.6:1) and Mansonia annulifera (AR = 1.3.1). The hourly biting activity of important JE vectors throughout the night on two bait types was also studied using three point moving averages. Hierarchical agglomerative cluster analysis was used to compare and classify mosquitoes on the basis of their similarity in biting rhythms.