Showing papers by "P. K. Das published in 2006"

A campaign of "communication for behavioural impact" to improve mass drug administrations against lymphatic filariasis: structure, implementation and impact on people's knowledge and treatment coverage.

Abstract: In the mass drug administrations (MDA) that form the principal strategy of the Global Programme to Eliminate Lymphatic Filariasis, treatment coverages of at least 65%-80% will be needed if the programme is to be successful. In the Indian state of Tamil Nadu, where treatment coverages were typically <65%, a comprehensive strategy of advocacy and communication, called the "communication for behavioural impact" (COMBI) campaign, has been developed and implemented, in an attempt to improve treatment coverage. This strategy combined advocacy, aimed at state-, district- and village-level administrations, with communication activities targeted at individual communities. The main aim was to alter the behaviour of many of those included in the rounds of MDA, so that they would be more likely to accept and consume the diethylcarbamazine tablets offered to them. The COMBI campaign had two variants, COMBI(+) and the more intensive COMBI(+ +), each of which has been implemented in six districts. Both the variants included the "personal selling" of treatment, via door-to-door visiting by a total of 113,500 filaria-prevention assistants. These assistants were able to visit 34%-49% of the households in each target community. In the COMBI(+ +) districts, up to 44% and 38% of households received information on lymphatic filariasis and its elimination via television commercials and posters, respectively. Overall, 78% of the villages in the COMBI(+ +) districts and 33% of those in the COMBI(+) districts were considered to have had good exposure to the communication campaign. At the end of this campaign about 30% more people (than pre-campaign) believed that lymphatic filariasis could be eliminated and many of those targeted considered lymphatic filariasis to be a dreadful disease, knew that a particular day had been designated "Filaria Day", and thought that the tablets offered in MDA should be consumed to prevent or eliminate the disease. Apparently as the result of the COMBI campaign, drug consumption increased, from 33% of those living in endemic communities, to 37% in the COMBI(+) districts and to 49% in the COMBI(+ +). Coverages as high as 65%-73% were recorded among those who had had the maximum exposure to the communication campaign. These results indicate that the COMBI campaign favourably changed the perception and behaviour of the people towards the elimination of lymphatic filariasis. The costs of the COMBI(+) and COMBI(+ +) strategies were only U.S.$0.002 and U.S.$0.009 per capita, respectively.

Population interactions between Culex vishnui mosquitoes and their natural enemies in Pondicherry, India.

Abstract: Population interactions among mosquitoes in the Culex vishnui subgroup, which are vectors of Japanese Encephalitis, and their natural enemies were studied in Pondicherry, India. We tested the hypothesis that the breakdown of interactions between the larvae and their natural enemies due to drought followed by rain was responsible for the sudden increase in the vector population above the threshold for disease transmission during the heavy rainy period. We randomly sampled mosquito larvae and their predators in different breeding habitats and subjected the mean densities of prey, predator, and mosquito larvae infected with parasites/pathogens to covariate analysis to understand the interaction between prey and their natural enemies in relation to environmental factors. In rice fields, neither prey nor predator showed any positive correlation with temperature, RH, or the number of rainy days. However, the pathogen/parasite of mosquito immatures showed a positive correlation with RH. Among the mosquito predators, notonectids exhibited a significant positive correlation with Cx. vishnui larvae. The parasitic Romanomermis iyengari and pathogenic Coelomomyces anopheliscus also showed positive correlations with immatures. No parasites and pathogens of mosquito larvae were recorded in shallow water pools (SWP) or cement tanks (CT) during the study period. Important predators recorded in SWP were notonectids, damselfly nymphs, Diplonychus indicus, and hydrophilids. Dragonfly nymphs, gerrids, and tadpole shrimps were recorded in CT. In CT, prey and their predators were positively correlated with RH and rainy days. In SWP, there was a highly significant correlation between prey, predators and environmental factors. We conclude that rice fields are a stable ecosystem where regular interaction occurs between larvae and their natural enemies and a sudden increase in mosquito populations is uncommon. In transient habitats, no such stability is present and they become more important as breeding habitats in terms of seasonality and number. Shallow water pools should be seriously considered for the control of these vectors.

Operational feasibility of lot quality assurance sampling (LQAS) as a tool in routine process monitoring of filariasis control programmes

Abstract: Lot quality assurance sampling (LQAS) with two-stage sampling plan was applied for rapid monitoring of coverage after every round of mass drug administration (MDA). A Primary Health Centre (PHC) consisting of 29 villages in Thiruvannamalai district, Tamil Nadu was selected as the study area. Two threshold levels of coverage were used: threshold A (maximum: 60%; minimum: 40%) and threshold B (maximum: 80%; minimum: 60%). Based on these thresholds, one sampling plan each for A and B was derived with the necessary sample size and the number of allowable defectives (i.e. defectives mean those who have not received the drug). Using data generated through simple random sampling (SRSI) of 1,750 individuals in the study area, LQAS was validated with the above two sampling plans for its diagnostic and field applicability. Simultaneously, a household survey (SRSH) was conducted for validation and cost-effectiveness analysis. Based on SRSH survey, the estimated coverage was 93.5% (CI: 91.7-95.3%). LQAS with threshold A revealed that by sampling a maximum of 14 individuals and by allowing four defectives, the coverage was >or=60% in >90% of villages at the first stage. Similarly, with threshold B by sampling a maximum of nine individuals and by allowing four defectives, the coverage was >or=80% in >90% of villages at the first stage. These analyses suggest that the sampling plan (14,4,52,25) of threshold A may be adopted in MDA to assess if a minimum coverage of 60% has been achieved. However, to achieve the goal of elimination, the sampling plan (9, 4, 42, 29) of threshold B can identify villages in which the coverage is <80% so that remedial measures can be taken. Cost-effectiveness analysis showed that both options of LQAS are more cost-effective than SRSH to detect a village with a given level of coverage. The cost per village was US dollars 76.18 under SRSH. The cost of LQAS was US dollars 65.81 and 55.63 per village for thresholds A and B respectively. The total financial cost of classifying a village correctly with the given threshold level of LQAS could be reduced by 14% and 26% of the cost of conventional SRSH method.

Long-term preservation of Leishmania donovani promastigotes on blood-agar slants.

Abstract: Isolates of Leishmania are maintained in vitro, often as cultures in liquid medium that require regular (often weekly) passage, or in vivo, usually by passage in Syrian hamsters or mice (Neal, 1984; Schnur and Jacobson, 1987). The methods employed are often labour-intensive, costly and timeconsuming (Ihalamulla et al., 2004), and frequent sub-culture increases the risk that cultures will become contaminated with bacteria or fungi. Although the long-term maintenance of isolates by lyophilization (Iusupov et al., 1976) or cryopreservation (Callow and Farrant, 1973; Raether and Seidenath, 1972, 1977; Miyake et al., 2004) is possible, in the developing countries where leishmaniasis is endemic there are few institutions that have the necessary facilities and supplies. Fortunately, there is a simple method that can be used to maintain the promastigotes of Leishmania donovani, and perhaps other Leishmania species, in culture for at least 7 months without a single sub-passage. This method, which is based on the maintenance of the parasites on blood-agar slants, with no overlay, in a refrigerator, has been developed and evaluated at the Rajendra Memorial Research Institute of Medical Sciences (RMRIMS), in Patna, India. For the evaluation, splenic aspirates from three cases of visceral leishmaniasis who had been admitted to the inpatient ward at the RMRIMS were cultured on NNN medium (Muniaraj et al., 2005). After primary isolation, which was successful for all three cases, the promastigotes were transferred to tubes of fresh NNN medium overlain with Locke’s solution, and incubated at 24¡1uC for 1 week (i.e. until the cultures were in early log phase). The promastigotes in the overlay from each culture were then counted, in a haemocytometer, so that sufficient Locke’s solution could be added to give 2610 promastigotes/ml. Each culture was then used to inoculate 72 screw-cap tubes — 36 that each contained a blood-agar slant [5% (v/v) defibrinated rabbit blood in Blood Agar Base No. 2 (HiMedia laboratories, Mumbai, India) at pH 8, with 15 mg gentamycin/ml] and, as controls, 36 tubes that each contained NNN medium with an overlay of Locke’s solution. Each slant was inoculated by zigzag streaking with 10 ml culture in an inoculation loop. The same volume of culture was added to the overlay in each tube of NNN. All 216 tubes were then incubated at 24¡1uC for 8 days, when promastigote colonies were visible on all the slants, as milky-white, raised, mucoid patches. The caps of the tubes were then sealed tightly before the tubes were placed in zip-lock polythene bags (with three tubes of each isolate/bag) and then transferred to a refrigerator at 7–8uC. At monthly intervals thereafter, 18 tubes — three of each isolate on agar slants and three of each isolate on NNN medium — were removed from the refrigerator so that the viability of the parasites in these tubes could be checked. Viability was investigated by adding 1 ml Locke’s solution to each tube, incubating the tubes at 24¡1uC, and checking the overlay, under a light microscope, after 3 h of incubation and then daily until motile promastigotes had been observed. The parasites in a tube were assumed to be non-viable if no motile parasites had been seen after checking for 25 days. Annals of Tropical Medicine & Parasitology, Vol. 100, No. 2, 173–175 (2006)