Diethylcarbamazine citrate-fortified salt for lymphatic filariasis elimination in India

Lymphatic filariasis (LF) is a vector-borne neglected tropical disease, causing permanent disability. The disease is debilitating and widespread, leading to tremendous productivity and economic loss. The Government of India (GOI) prioritized the elimination of LF through the annual mass drug administration (MDA) programme in 2004 and continued with a single dose of diethylcarbamazine citrate (DEC), 6 mg/kg of body weight, plus albendazole annually over a period of 5-6 years. The GOI had set the target to achieve LF elimination by 2015 and now by 2030. The progress so far has been suboptimal. Much remains to be done as about 84 per cent of the total 328 endemic districts are still under MDA. The major challenge in implementing MDA is poor compliance. It is necessary to have a feasible alternative strategy addressing the above challenge to achieve the desired goal of LF elimination. At this juncture, a well-researched approach, i.e. the use of DEC-fortified salt, also advocated by the World Health Organization, as a unique form of MDA, is proposed. As per this strategy, a low dose of DEC (0.2% w/w) is added to the cooking salt at the manufacturing facility of iodized salt and consumed by the LF-endemic communities for about two years. Many examples of successful use of this strategy for LF elimination in small- and large-scale trials have been documented in India and several other endemic countries in the world. Implementing DEC–iodine-fortified salt is a safe, less expensive, more efficient and prompt approach for achieving the elimination of LF in India. Adverse effects are none or minor and self-limiting. The DEC-fortified salt strategy can easily piggyback on the existing countrywide deployment of iodized salt under the National Iodine Deficiency Disorders Control Programme (NIDDCP), which has achieved a great success in reducing iodine-deficiency disorders such as hypothyroidism. This existing robust programme can be leveraged to launch DEC-fortified salt for the community. If implemented appropriately, this strategy will ensure the complete cessation of LF transmission within two years from its introduction. If the said strategy is implemented in 2022, it is expected that India will be able to achieve the LF elimination by 2024, much before the global target of 2030.

Dengue vector abundance and diversity of breeding habitats in Puducherry, South India

Puducherry had reported regular dengue outbreaks since 2003 with many-fold increase in number of cases every year. This study was done to assess the intensity of dengue vector breeding and diversity of breeding habitats. Aedes surveys were conducted in 8 Primary Health Centres (PHCs) representing both rural and urban areas of Puducherry district throughout the year 2012. Containers inside and outside randomly (simple) selected houses and vacant sites around houses were examined for presence of Aedes mosquitoes. The containers containing water with immature larvae were designated as positive containers (PC), while the containers holding only water were designated as wet containers and all the larvae/pupae from the positive containers were collected and entomological indices were determined using standard WHO methods. The vectors, Aedes aegypti and Ae. albopictus were encountered in the survey, with Ae. aegypti present in high numbers in urban as well as rural areas. The plastic containers were found as the most productive indoor breeding habitat as the 27.2% of the total pupae collected was contributed by plastic containers followed by flower vase (22.8%) and grinding stone (17.6%). Larval indices were found to vary throughout the year and highest indices were recorded during the months of October and November indicating the potential risk of dengue fever during this period.

Predatory potential of Platynectes sp. (Coleoptera:Dytiscidae) on Aedes albopictus, the vector of dengue/ chikungunya in Kerala, India

Unused and discarded latex collection containers (LCCs) are the major breeding habitats of Aedes albopictus in the rubber plantations of Kerala, India. Platynectes sp. (Family: Dytiscidae) was observed to invade these habitats during the monsoon season and voraciously devour the larval instars of this major vector species of arbo-viral diseases. Field observations showed a reduction of 70.91% (p = 0.0017) and 100% in Aedes larval density, on the first and four days post release of eight beetles per LCC respectively. In laboratory, a beetle was found to devour 17.75 + 5.0 late larval instars of Ae. albopictus per day. Our findings indicate Platynectes sp. could be a potential bio-control agent against Ae. albopictus, the vector of chikungunya/dengue fevers, in rubber plantations.

Susceptibility status of Mansonia annulifera to Brugia malayi parasites in Cherthala, Alappuzha district, Kerala.

Laboratory studies conducted on Ma. annulifera collected from Cherthala region, Kerala, endemic for Brugian filariasis indicated that this species is highly susceptible to B. malayi parasites. The experimental infection index of this species was relatively higher (2.74). No significant loss of larvae during development was recorded. The extrinsic incubation period was estimated to be 8 days.

Current status of filariasis in Chavakad taluk, Trichur district, Kerala.

A sample survey using parasitological, clinical and entomological indicators was carried out in all the 18 administrative units of Chavakad taluk, Trichur district, Kerala, India to assess the current filariasis situation. Cluster sampling procedure was followed to screen individuals. Both Wuchereria bancrofti and Brugia malayi species were found to be prevalent in this taluk. Microfilaria (mf) carriers with W. bancrofti were detected in eight areas while B. malayi was recorded only from one area. The two species were found to co-exist in another area. The highest infection rate registered for W. bancrofti was 1.51 while it was 0.3 for B. malayi. Infection due to W. bancrofti constituted 87.88% of the total 33 microfilaria cases. Prevalence of B. malayi was very low. Cases with clinical manifestation of filariasis were recorded in all the four areas surveyed. The present trend in the prevalence of infection (mf) and disease showed a decline in both the species when compared to earlier surveys of 1960s. At least 11 areas are still endemic for filariasis in this taluk. Although prevalence of mf was recorded for the first time in one of the areas viz., Elavalli, the rate was only 0.16%. Entomological surveys revealed the presence of 14 mosquito species, of which Culex quinquefasciatus contributed 84.85% and Mansonia 0.77%. While C. quinquefasciatus was recorded in all the 18 areas, Mansonia spp were found only in 8 areas. Only C. quinquefasciatus was found to harbour different developmental stages of W. bancrofti, with overall infection and infectivity rates of 1.94 and 0.97 respectively. The possible reason for the decline in vector density and infection in man are postulated.

Efficacy of diethylcarbamazine-medicated salt for microfilaraemia of Brugia malayi.

BACKGROUND: Pilot studies in India and abroad have demonstrated the benefit of cooking salt fortified with diethylcarbamazine citrate (DEC) for the control of lymphatic filariasis. In India, DEC-medicated salt has been introduced on a commercial basis in the Cherthala region of Kerala, which is endemic for Brugia malayi (B. malayi). We studied the efficacy of DEC-medicated salt in the clearance of microfilaraemia of B. malayi. METHODS: Eighteen cases of microfilaraemia (11 men; 7 women) were selected; 14 in the experimental group (i.e. treated with 0.2% w/w DEC-medicated salt) and the rest as the control group who were given a placebo. The consumption of salt and the status of parasitaemia were monitored till all the microfilaria carriers became negative. RESULTS: There was a significant reduction in the density of microfilariae (intensity) among the treated individuals over a period of time. The duration required for the clearance of microfilariae ranged from 9 to 30 [mean (SD) 19.4 (1.7)] weeks. All microfilaraemics except one reported side-effects which were mild-to-moderate and persisted for a maximum period of one month. CONCLUSION: DEC-medicated salt effectively clears microfilariae within 30 weeks in parasitaemic individuals. No 'endemic normals' reported any side-effects, though these were common among the microfilaria carriers.

Field evaluation of biodegradable controlled release formulation of fenthion against Mansonia mosquitos.

Controlled release monolithic formulation of fenthion, an organophosphorus mosquito larvicide, prepared by the physical entrapment of the active agent into biodegradable polymer matrices was evaluated against Mansonia mosquito larvae breeding in hydrophytes infested coconut husk retting ponds. Field evaluation was carried out at two application rates viz, 2.5 and 1.0 ppm. Absolute control of larval breeding was observed for 25 and 17 weeks and over 50% reduction in breeding density was observed for another 3 and 2 weeks for the respective application rates of 2.5 and 1.0 ppm. The bioassay carried out with the water samples collected from the ponds treated at 2.5 ppm against the fourth instar larvae of Mansonia annulifera showed larval mortality of more than 95% for 14 weeks and 80-95% from 15 to 25th week. The concentration of fenthion in the treated ponds was found to vary between 0.006 and 0.095 ppm during the evaluation period.

Mattancherry urban agglomeration, a diminishing focus of lymphatic filariasis in Kerala.

Parasitological survey conducted recently in Mattancherry, Kerala showed a low prevalence of microfilariae (mf), with a mf rate of 1.81%, compared to that of 1956 when the mf rate was 14.7%. No brugian infection was encountered in the present investigation, though both bancroftian and brugian infections were reported earlier. Culex quinquefasciatus, the vector of bancroftian filariasis was the most predominant (93.3%) mosquito species, and its infection and infectivity rates were 0.76% and 0.54% respectively. Mansonioides spp., the vectors of brugian filariasis constituted only 0.2% of the total mosquitoes and with no infection. The overall reduction in the prevalence of mf cases and vector infection rates over the years is attributed to the continued activities of the National Filaria Control Programme. The disappearance of brugian filariasis could mainly be due to the drastic reduction in the Mansonioides breeding habitats, as a result of rapid urbanization coupled with improved socio economic conditions.

Brackish water mosquito problem of Vypeen Island, Cochin, Kerala.

A preliminary study has shown that the marshy terrain and brackish water bodies associated with mangrove forests contributed profuse breeding of mosquitos in Vypeen island, causing a severe menace to the island population. A total of 14 species belonging to four genera viz, Aedes, Anopheles, Armigeres and Culex was recorded from different habitats. Culex sitiens was found to be the predominant mosquito in all the perennial breeding habitats. The extent of different habitats in the production of mosquitos, and its possible abatement, using environmental and/or biocontrol methods are discussed.

Myiasis in filarial lymphoedema due to Chrysomyia bezziana.

In patients with filarial lymphoedema of the limbs, infestation by maggots is extremely rare. We saw three patients with lymphoedema who harboured Chrysomyia bezziana in leg ulcers and in one of them 128 maggots were recovered. A course of local dressing, antibiotics and anti-inflammatory drugs resulted in healing of the wounds. Ulcers in patients with lymphoedema should be carefully tended with cleaning and dressing otherwise myiasis may supervene.

The resting and house frequenting behavior of Mansonia annulifera, Ma. uniformis and Ma. indiana, the vectors of Malayan filariasis in Kerala State, India.

Mansonia annulifera, was recorded to be an endophilic species, preferring to rest indoors, while Ma. uniformis was exophilic, having a predilection for outdoor resting habitats, eg bushes and shrubs. Ma. indiana did not show a clear preference to either of these biotopes. In indoor resting collections, the unfed proportion of Ma. uniformis was significantly higher during post-dusk compared to day hours (p < 0.05), indicating that this exophilic species enters houses during dusk hours for feeding. The full fed proportion was higher during day hours compared to dusk/night hours. The semigravid proportion showed a significant reduction during post-dusk hours (p < 0.05). These findings suggest that after having a blood-meal this species rest indoors and leave the houses for outdoor resting sites during the dusk hours on the subsequent night.

Daily diethylcarbamazine for the treatment of Brugia malayi microfilaria carriers.

BACKGROUND. Diethylcarbamazine is effective for the treatment of brugian filaria carriers. However, the 12-day course with a daily dose of 6 mg per kg body weight is rarely completed. The World Health Organization has indicated the need for better regimes to control filariasis. METHODS. We evaluated the long term effects of three different dosage regimes of diethylcarbamazine--6, 9 and 12 mg per kg body weight--to a total of 72 mg on 93 microfilaria carriers of Brugia malayi. RESULTS. All cases treated with the 6 mg daily dose showed complete clearance of microfilaria immediately after the treatment. However, at the 9 and 12 mg daily doses only 91% and 85% of cases respectively showed complete clearance. There was a close association between the daily dose and the proportion of cases developing side-effects. The mean initial microfilaria counts were significantly higher in those who had side-effects than in those who did not. An 11-month follow up showed that with the 6 mg daily dose the recurrence rate of microfilaraemia was 29% while with the 12 mg daily dose it was 67%. Four per cent of patients on a daily dose of 6 and 9 mg discontinued treatment while 21% of those on the 12 mg daily dose did so. CONCLUSION. The 6 mg daily dose of diethylcarbamazine was the most effective and best accepted regime.

Comparison of effects of mass annual and biannual single dose therapy with diethylcarbamazine for the control of Malayan filariasis.

Annual and biannual mass single dose diethylcarbamazine citrate (DEC) at 6 mg/kg body weight was administered to people in a Brugia malayi endemic area in Shertallai part of Kerala, India, in 1987 and 1988. The coverage of population ranged between 41.33% and 66.01% in different rounds. The highest percentage of treated population developing side reactions was 8.4%. Both annual and biannual regimens were effective in reducing the microfilaria prevalence significantly from 4.90% to 1.23% and from 6.27% to 0.62% respectively and the incidence of infection was minimal in the adult population and zero among children. There was significant reduction in mean microfilaria count in both annual (81.08%) and biannual (98.00%) areas. Marked reduction in the proportion of high density carriers and infectivity index of the population after DEC therapy was also observed. Beneficial effect of mass single dose DEC on clinical cases of filariasis was evident from the reduction in the prevalence of acute manifestations, recent edema cases and the proportion of chronic cases with acute episodes. Results obtained from mass treatment areas were compared with those of the control area.

Influence of diethylcarbamazine on the patent period of infection in periodic Brugia malayi.

The patent period of infection which reflects the fecundic life span of the adult female worm was estimated for periodic B. malayi in south India by using immigration death model. Longitudinal data on natural loss of infection or that due to different degrees of DEC pressure in a cohort population of microfilaria carriers after a three years period, were used for the estimations. The patent period of infection was estimated to be 3.45 yr under natural conditions (without DEC therapy), which was reduced to 1.67 yr following one full course of selective therapy (6 mg/kg body wt/day for 12 days). When selective therapy was supplemented with four rounds of biannual single-dose mass DEC therapy (6 mg/kg body wt) the patent period was further reduced to 1.34 yr. The proportion loss of infection was relatively higher in microfilaria carriers who discontinued DEC selective therapy, when compared to natural loss. The percentage reduction in the mean microfilaria count was observed to decrease with increasing DEC pressure. Neither sex nor the age of the host was found to influence the fecundic life span or the survival of female adult worm.

Seasonal abundance & biting behaviour of Mansonia annulifera, M. uniformis & M. indiana & their relative role in the transmission of malayan filariasis in Shertallai (Kerala state).

Three species of Mansonia (Mansonioides) mosquitoes, viz., Mansonia annulifera, M. uniformis and M. indiana were recorded in the Shertallai region of Kerala state. M. annulifera and M. uniformis were recorded throughout the year while M. indiana was seasonal and in small numbers. Their indoor resting density was 3.29, 0.25 and 0.10 per man per h and the man biting density was 24.67, 12.74 and 0.47 per man per night respectively. Vector density fluctuated through seasons and reached a peak during the monsoon/post-monsoon period when there was an increase in the breeding surface area and a relatively higher survival of the adults. The biting tendency of M. annulifera and M. indiana was relatively more indoors (endophagic) whereas it was outdoors (exophagic) for M. uniformis. All these mosquitoes showed a predilection towards cattle, with varying degrees of zoophily. The relative abundance, man biting behaviour and a higher transmission potential indicate that M. annulifera is a more potent vector of Brugia malayi, than M. uniformis in this region.

Weedivorous fishes for the control of vectors of Malayan filariasis.

An attempt was made to assess the efficacy of phytophagous fishes viz., Ctenopharyngodon idella, the Chinese grass carp and Osphronemus goramy, the giant gourami in the control of mansonioides mosquitoes by checking the growth of aquatic weeds which support their breeding. When C. idella and O. goramy were used in monoculture 80.21 and 81.25 per cent of the ponds were kept free from weeds. With polyculture using grass carp in combination with other varieties of carps, only 70.10 per cent of the ponds were kept out from the reinfestation of weeds. Even in the reinfested ponds, there was significant reduction (P less than 0.05) in vector breeding in all the three types of piscicultures, as compared to the control ponds. The utility of weedivorous fishes in the elimination of aquatic weeds and thereby breeding of vectors of Malayan filariasis was thus demonstrated.

Choice & integration of different approaches to case detection with special reference to brugian filariasis in south India.

Treatment following rapid case detection in population, particularly the target age classes, which record high prevalence, is necessary for effective control of lymphatic filariasis. Conventional door-to-door surveys resulted in delay in detection of parasite carriers and patients with clinical filariasis, particularly in rural areas. An integration with other approaches like school surveys, health camps, filariasis clinics and microfilaria detection camps (MDC) was found effective in covering a much larger population in brugian filariasis case detection in an endemic area in south India. The MDCs organized through Integrated Child Development Scheme (ICDS MDC) yielded a good coverage of pre-school children. School surveys were ideal in covering children en masse. Community MDCs and health camps arranged with active community participation were useful in covering adolescents and young adults in large numbers. The filariasis clinic was effective in screening older adults above 30 yr. The relative efficiency of these approaches in terms of time and manpower utilization has been discussed.

Attachment behaviour of immatures of Mansonia annulifera (Theobald), 1901.

The detachment and reattachment of the immatures of M. annulifera with their host plants (hydrophytes) is a regular phenomenon. This occurs frequently with the same plant, or with a different one, throughout the larval span. The duration between detachment and reattachment varied from 30 sec to one hour and majority of them get reattached within a minute. This behaviour is instinctive and not found to be influenced by food availability. In the absence of hydrophyte, early immature stages survive relatively longer (192 h), when compared to the late ones.