Seasonal fluctuations of dengue fever vector, Aedes aegypti (Diptera: Culicidae) in Delhi, India.

Studies on the seasonal fluctuation of Aedes aegypti were undertaken in different localities of Delhi, during 2000. The Aedes aegypti population was found to be prevalent in all the localities in Delhi. Water coolers and tires were found to be the preferred breeding habitats of Aedes mosquitos in the city. Aedes aegypti, being hygroscopic, showed a phenomenon of annual pulsation. It tends to move to mother foci in the central areas of the city, which are humid in the dry season, and spread out during the wet season. Out of 103,778 houses surveyed, 20,513 houses and 3,547 containers were reported positive for Aedes aegypti. The house container, and Breteau indices were very high during the post-monsoon season. The container indicies was very high (17.7%) in the defence area in September 2000. The container index in the areas of the Municipal Corporation of Delhi (MCD) and the New Delhi Municipal Committee (NDMC) were found to be high during the same period. The house index forAedes aegypti ranged from 0.1 to 7.4, 0.1 to 11.3, and 0.1 to 11.1 in the MCD, NDMC, and Defence areas, respectively.

Development of improved media for axenic cultivation of Acanthamoeba culbertsoni, Singh and Das 1970.

Several varieties of peptone supported growth of A. culbertsoni to different extents reaching a maximum cell density of 1-2 X 10(6)/ml. Proteose peptone and tryptone also yielded good growth when combined with thiamine and vitamin B12. A combination of proteose peptone with glucose, yeast extract and salts promoted excellent growth of A. culbertsoni with cell density reaching 1-2 X 10(7) cells/ml; tryptone and one of the indigenous peptones also yielded comparable growth when substituted for proteose peptone in this medium. Casamino acids also supported good growth of amoebae and requirement of yeast extract could be met by a combination of thiamine, vitamin B12 and biotin. Bacto peptone did not support good growth of this amoeba but supplementation of peptone with casamino acids or amino acid mixture improved the growth supporting capacity of the medium. Development of several media with or without glucose will aid in cultivation of A. culbertsoni, studies on its metabolism as well as screening of potential drugs.

Evaluation of diversified antigens for detection of Mycobacterium leprae antibodies from leprosy patients and contacts.

A comparative evaluation of diversified antigens in ELISA has been made for detection of M. leprae antibodies in the sera of leprosy patients and their contacts. Out of the four antigens, namely M. leprae sonicate (ML), phenolic glycolipid I (PGL-1), M. habana sonicate (MH) and its arabinomannan (AM), the cross reactive antigens (MH,AM) have comparatively detected more number of leprosy cases. Homologous antigens (ML, PGL-1) have lower detection level. Use of MH and AM for detection of mycobacterial antibodies have been discussed and advocated for epidemiological studies of leprosy/tuberculosis.

Explanation and implications of increasing trend of villages with only one case of guineaworm for guineaworm eradication in India.

Under the Guineaworm Eradication Programme (GWEP) in India, active case search data are consolidated in the lists of year-wise guineaworm affected villages, first prepared in 1985. These lists contain valuable information on many parameters of guineaworm eradication in India. Among other things, they show that in a given year there is always a proportion of villages with only one case relative to the total number of infected villages, and this proportion seems to increase with the progress of the eradication programme. The proportion for seven years between 1986 and 1992 in nineteen districts chosen for analysis was observed to be 22.2, 26.6, 35.0, 38.0, 40.0, 46.7, and 55.8 per cent. Correlation coefficient (gamma) for nineteen districts as a whole was found to be -.57 significant at 0.05 level. It is argued that this observation can be explained on the assumption that the single case in a village originates from any of numerous extradomestic unsafe water sources, in agricultural fields, which because of their great multiplicity lie outside the purview of the control measures. When guineaworm disease is widespread and at a high intensity transmission level, the existence of such foci is masked under the main village foci as during active case searches a distinction as to the origin of guineaworm cases cannot be made. Extradomestic foci become increasingly manifest as the main village foci disappear under impact of control measures. Thus, increase in the proportion of such villages could be used as a crude indicator of the successful implementation of the GWEP. The analysis of district data shows that guineaworm disappears when the proportion of such one case village reaches a high level.(ABSTRACT TRUNCATED AT 250 WORDS)

Phlebotomine sandflies (Diptera: Psychodidae) from Western Ghats in Kerala and Tamil Nadu States, India. Part I. Description of four new species.

In this communication four new species of phlebotomine sandflies collected from Western Ghats physiographic division in the states of Kerala and Tamil Nadu are described. Three of the new species are assigned to the Subgenus Neophlebotomus while one belongs to the nicnic group.

Phlebotomine sandflies (Diptera: Psychodidae) from Khandwa and Hoshangabad Districts of Madhya Pradesh, India.

A survey of Phlebotomine sandflies undertaken in April 1985 in Hoshangabad and Khandwa districts of Madhya Pradesh yielded 332 sandflies on 204 sticky traps. Sandflies were collected from feral habitats of termite hills, rodent burrows and tree holes and indoor habitats of human dwellings and cattle sheds. The sandflies belonged to eight species viz., Phlebotomus argentipes, P. papatasi, P. colabaensis, Sergentomyia clydei, S. babu, S. bailyi, S. punjabaensis, and S. indica. Among them P. colabaensis, S. clydei and S. indica were found only in feral habitats, whereas P. argentipes and P. papatasi and other Sergentomyia species collected were found in domestic as well as feral habitats. Termite hills and rodent borrows were the most productive habitats, an observation accounted for by the predilection of sandflies to seek microhabitats offering high humidities and equable temperatures to avoid high summer temperature and low relative humidities of outside environment. Sandfly collection by sticky traps is recommended as an objective method of collection.

Distribution of Phlebotomine sandflies (Diptera:Psychodidae) according to the physiographic divisions of India.

In this paper, the distribution of 44 known species of Phlebotomine sandflies which include vectors of leishmaniasis in India are arranged according to accepted physiographic divisions of India. Distribution maps in respect of known disease vectors Phlebotomous argentipes, P. papatasi, P. sergenti, P. salehi and potential vectors of leishmaniashis in India, P. hindustanicus and P. major are presented. The study brings out the salient features of sandfly distribution in India and need for more comprehensive work in the inadequately studied areas of the north east hills and the northern mountain ranges.

Pictorial key to the common Indian species of Aedes (Stegomyia) mosquitoes.

The paper provides a simple pictorial key to differentiate common stegomyia species found in urban areas. This key will help medical officers and paramedical staff in demarcating the areas of influence of Aedes aegypti within a Dengue surveillance area.

Monitoring the efficacy of temephos application and use of fine mesh nylon strainers by examination of drinking water containers in guineaworm endemic villages.

Application of temephos in unsafe water sources for destroying cyclops, the intermediate hosts of guineaworm, and distribution of fine mesh nylon strainers for promoting prophylaxis against guineaworm are accepted methods of guineaworm control in different endemic countries. The existing methods of monitoring the efficacy of these guineaworm control methods are not fully informative. Examination of drinking water stored at household levels for presence of cyclops with or without Dracunculus larvae can provide information on the efficacy of these control/prophylactic methods, besides serving as a means of interpersonal health education to the community. This paper presents observations carried out in two villages in peninsular India in 1991, which revealed that while in one village complete absence of cyclops from stored water containers was attributable to the use of temephos in the village and straining of drinking water, in the other village, with no temephos application, 15.6 per cent of containers contained varying numbers of cyclops in them. Implications of these observations for guineaworm eradication activities are discussed.

A comparative study on the optimum time and method of collection of Phlebotomus argentipes and other sandflies. (Diptera: Psychodidae).

A uniform method of collection is imperative for generating comparable entomological data in connection with studies on efficacy of vector control measures against sandflies. Two commonly employed methods for sandfly collections i.e. hand collection by aspirator and sticky paper traps were compared under similar ecological conditions to determine the optimum time and method for generating data on relevant indices. Only two P. argentipes male specimens were collected at dusk time from 12 cattle sheds and 40 human dwelling by aspirator method. By sticky traps placed in the same resting shelters, 243 P. argentipes and 58 specimens of 5 other species were collected. However, the collection by sticky traps comprised only males and unfed females. In the morning collection by aspirators 268 sandflies of 8 species in all stages of gonotropic cycle were collected. It is concluded that morning collections by aspirator method can provide objective assessment of control measures. Sticky traps may be useful as additional method for confirming presence of P. argentipes in sprayed areas.

Anthropophily of Anophelines in Duars of West Bengal and other regions of India.

Attempts have been made to identify the source of blood meals of twenty three anopheline species from various areas of high malaria endemicity in India. Anopheles minimus, Anopheles fluviatilis and Anopheles dirus showed a high propensity for human blood in North-Eastern parts of the country while Anopheles sundicus was found to be anthropophilic in Andaman & Nicobar Islands. Anopheles culicifacies, Anopheles maculatus and Anopheles philippinensis were found primarily zoophilic in north-eastern areas. High anthropophily has been closely related to sporozoite infection in anophelines specially in Anopheles minimus and is of great epidemiological significance.

D.D.T. resistance in Sergentomyia shorttii (Diptera: Psychodidae) in Kamrup, Assam--first report in Sergentomyia genus.

S. shorttii, a common phlebotomine sandfly species of Assam, was tested for susceptibility to commonly used insecticides, D.D.T., malathion and Fenitrothion in Kamrup district, Assam. Tests carried out by WHO test kits showed 100 per cent mortalities against discriminating concentrations of malathion (5 per cent) and Fenitrothion (1 per cent). With D.D.T., in 1 hr. exposure mortalities recorded were 54.5 and 64.4 per cent, whereas in 24 hr. exposure mortalities were 75 per cent and 90 per cent. The area has been under continuous D.D.T. spraying since the beginning of NMEP in 1958, and high selection pressure appears to have precipitated D.D.T. resistance in this partly exophilic species.

Outbreak of dracontiasis in the Bhiwandi town of Maharashtra: a report.

In May 1990, dracontiasis or guineaworm cases were reported for the first time from Bhiwandi, a thickly populated urban industrial complex about 50 kms north of the metropolis of Bombay. The report of guineaworm cases from a typical urban situation was considered an unforeseen setback to an otherwise satisfactory progress towards guineaworm elimination target in Maharashtra State. To elucidate the factors responsible for the outbreak of guineaworm cases in Bhiwandi, an investigation was taken up in third week of September 1990. The investigation revealed that all the guineaworm cases occurred in a small area of about 1 sq. km. where, because of the inadequate piped water supply, people were forced to resort to step wells for drinking water and other needs. Except for the two cases, who were local residents, all the other cases involved floating population from nonendemic areas. The vector involvement, could not be elucidated, as all the 31 water sources were free of cyclops, because of treatment with temephos undertaken by the Municipal Council prior to the investigation. It has been suggested that transmission of dracontiasis in the contiguous vulnerable urban settlements is a possibility which should be kept in mind while formulating control or eradication strategies against guineaworm disease.

Calculation of water volume in step wells for cyclopicide application and its eco-epidemiological implication: mathematical validation of some theoretical considerations.

Chemical treatment of step wells to kill cyclopoid vectors of guinea worm by temephos (50 per cent E. C.) at the dose of 1 ppm is now an important activity of the guineaworm eradication programme in India. Calculation of correct volume of water in step wells, to determine the exact quantity of temephos to be applied, therefore, deserves adequate attention to prevent over and underdosing of stepwells by the chemical. The prescribed method of calculation of water volume includes two formulae; pi r2h and 1 x b x h (where h = mean depth for uneven bottoms and is a single depth measurement for almost even bottoms). Field observations revealed that in many stepwells there were marked variations in depth within the same well. These differences in depth ranged from small to very large in some wells. Since these depth variations would lead to miscalculation of water volume by existing method and the dose of temephos to be applied, with eco-epidemiological consequences, new formulae have therefore been deduced for conceivable patterns of depth variations by geometrical and algebric applications. The new formulae will permit calculation of, nearest to, exact quantity of temephos required for application. These formulae have been validated by an example.

Absence of Phlebotomus argentipes Ann & Brun. (Diptera: Psychodidae) the vector of Indian kala-azar from Kamrup district, Assam.

In the past Assam was devastated by epidemics of Kala-azar. However, inspite of resurgence of this disease in Bihar and neighbouring areas Assam has remained untouched by this disease since the mid 1950s so far. The study undertaken in Kamrup district, sought to provide an entomological explanation for Assam's present freedom from Kala-azar. Sandfly collections were made in 15 villages. Three different methods were used; namely hand collections by aspirator and torch, sticky traps and examination of soft parts of cattle in the villages for mating swarms. 1049 sandflies were collected which did not include any specimens of P. argentipes. The vector of Indian Kala-azar has either been eliminated by continuous insecticide spraying in this high P. falciparum, and chloroquine resistance area or reduced to such low levels of prevalence that routine sampling methods are unable to reveal its presence. The implications of this finding are discussed in relation to Kala-azar control in India, in general.

Efficacy of diethylcarbamazine medicated salt in interrupting Brugia malayi transmission in hill tribe settlements in Kerala State.

A filariasis survey carried out about eight years after achieving zero microfilaria (mf) rates following administration of diethylcarbamazine (DEC) medicated salt in the Kani hill tribe settlements in Quilon and Thiruvananthapuram districts of Kerala State revealed that there was no reappearance of Brugia malayi infection in the experimental areas. Mf rates were maintained at zero level in the experimental villages, while in the control villages, 2.9 per cent mf positives were observed. Mansonia (Mansonioides) uniformis dissected did not reveal filarial infection. It is concluded that DEC medicated salt regime in the experimental areas of Kani hill tribe settlements has been successful in effectively interrupting B. malayi transmission. Pilot studies in other B. malayi endemic areas of India using DEC medicated salt regime with the objective of eliminating B. malayi transmission are advocated, since the parasite has a restricted distribution in India and is already showing a declining trend.

Community perception of mosquitos and mosquito control in some areas of urban Delhi and rural Alwar, Rajasthan.

There is little information regarding community perception of mosquitos and and their control in India. A qualitative study based on In depth discussions with the people in Urban Delhi, and rural Alwar was carried out in August-September, 1995. In the Ghazipur and Munirka areas of Delhi, 63 respondent groups with 171 head counts, and 59 respondent groups and 305 persons in Alwar were met. Community responses to uniform set of questions on mosquito types, seasonality, biting, breeding places, ongoing control activities, and methods of personal protection were recorded. Most people in the areas surveyed viewed mosquitos primarily as a biting nuisance, and secondarily as agents of disease and debilitators of health. In general the knowledge regarding mosquitos was deficient. An overwhelming tendency to attribute mosquitogenic conditions to the unsavoury features of one's physical environment was observed in both areas. The methods of personal protection and attitudes to organised control are discussed.

Operational research in malaria--why and how?

Research studies conducted so far have had little bearing on the National Malaria Eradication Programme implementation for want of operational component. In India there is no dearth of scientific knowledge and technical know-how but dearth of operational research of direct relevance to the programme. The rationale for research under the operational conditions of the NMEP is discussed in this paper.

Susceptibility status of malaria vectors to insecticides in India.

The use of chemical insecticides for control of malaria vector populations continues to be the mainstay of malaria control strategy in India. Monitoring vector susceptibility to chemical insecticides is an important activity under the National Malaria Eradication Programme to ensure judicious and effective use of chemical Insecticides. 72 entomological zones were established under NMEP in 1977 for undertaking entomological studies in the malaria problematic areas. These zones have been generating insecticide susceptibility data in respect of the various malaria vectors. In this paper the insecticide susceptibility data, in respect of major vectors of malaria as on 1997, is presented.

Preventing dengue/dengue haemorrhagic fever outbreaks in the National Capital Territory of Delhi--the role of entomological surveillance.

Outbreaks of Dengue/Dengue Haemorrhagic Fever have been occurring in the National Capital Territory (NCT) Delhi from time to time. A massive outbreak of Dengue/DHF causing considerable mortality occurred in 1996 in the NCT, Delhi. Since this outbreak regular entomological surveillance has been instituted, for timely preventive action against Dengue/DHF. The Central Cross Checking Organisation (CCO) of the National Malaria Eradication Programme cross-checks Aedes surveillance activities in Delhi. In this paper we present our experiences in entomological surveillance in relation Dengue, to share them with other workers in this field.