Developing consensus of evidence to target case finding surveys for podoconiosis: a potentially forgotten disease in India.

BACKGROUND: Podoconiosis is a non-infectious geochemical lymphoedema of the lower legs associated with a significant burden of morbidity. There are historical reports of podoconiosis in India, but its current endemicity status is uncertain. In this investigation we aimed to prioritise the selection of districts for pilot mapping of podoconiosis in India. METHODS: Through a consultative workshop bringing together expert opinion on podoconiosis with public health and NTDs in India, we developed a framework for the prioritisation of pilot areas. The four criteria for prioritisation were predicted environmental suitability for podoconiosis, higher relative poverty, occurrence of lymphoedema cases detected by the state health authorities and absence of morbidity management and disability prevention (MMDP) services provided by the National Programme for Elimination of Lymphatic Filariasis. RESULTS: Environmental suitability for podoconiosis in India was predicted to be widespread, particularly in the mountainous east and hilly southwest of the country. Most of the districts with higher levels of poverty were in the central east and central west. Of 286 districts delineated by state representatives, lymphoedema was known to the health system in 189 districts and not recorded in 80. Information on MMDP services was unavailable for many districts, but 169 were known not to provide such services. We identified 35 districts across the country as high priority for mapping based on these criteria. CONCLUSIONS: Our results indicate widespread presence of conditions associated with podoconiosis in India, including areas with known lymphoedema cases and without MMDP services. This work is intended to support a rational approach to surveying for an unrecognised, geographically focal, chronic disease in India, with a view to scaling up to inform a national strategy if required.

Prevalence of Neglected Tropical Diseases (Leishmaniasis and Lymphatic Filariasis) and Malaria Among a Migrant Labour Settlement in Kerala, India.

Neglected tropical diseases (visceral leismaniasis, lymphatic filariasis) and malaria are endemic in northern states of India. Kerala has become a hub of construction activities employing a large number of migrants from these endemic states. Studies on morbidity pattern among migrants in Kerala are lacking. It is essential to look into the burden of these infections among migrant laborers who can act as reservoirs and are a threat to native population. A cross sectional study was done among migrant laborers in Ernakulam district, Kerala. After getting informed consent, a questionnaire was administered to each participant to collect sociodemographic details and 5 ml of blood was collected for detection of antigens using rapid diagnostic tests (RDT). Of the 309 migrants tested, none of them were positive for leishmaniasis, while 3.8% were positive for malaria and 3.6% for filariasis. With 2.5 million migrant laborers in Kerala, the magnitude of the problem in absolute numbers is enormous. Active surveillance and treatment is needed to prevent the reemergence of these diseases in Kerala.

Population dynamics of Phlebotomus papatasi (Diptera:Phlebotomidae) in Pondicherry, India.

Investigations on the population dynamics of Phlebotomus papatasi were carried out. The average indoor resting density fluctuated between 16.70 and 2.25/man-hour in different seasons with a maximum density during monsoon season. There was a significant positive correlation between density and rainfall. Probability of daily survival of adult population was high in monsoon and low in summer. Both relative humidity and temperature influenced the survival. The finite rate of natural increase of the field population was maximum in October and minimum in April. The monsoon season, with moderate temperature and relative humidity was found to be favourable for the growth of P. papatasi population.

Biting rhythm & biting activity of phlebotomid sandflies.

The biting behaviour of Phlebotomid sandflies was studied in a rural village of Pondicherry through all night collections for a period of one year, using human volunteers and cattle as baits. Phlebotomus papatasi was caught only on human bait, showing anthropophily while Ph. argentipes was caught on cattle baits, showing zoophily. The biting activity was seen throughout the night, reaching a peak of 0100 h in Ph. papatasi and 0200 h in Ph. argentipes.

Larvivorous potential of some indigenous fishes of Sherthallai region with special reference to their efficacy in control of mansonioides.

Larvivorous potential of some indigenous fishes collected from natural habitats of Sherthallai region in Kerala state, India, was studied under laboratory as well as controlled field conditions. Ophiocephalus striatus was observed to consume significantly higher number of mansonioides larvae (354/g body wt/day), followed by Macropodus cupanus (231/g body wt/day). The proportion of adult vector mosquito emergence was significantly (P less than 0.05) lower in cages with fish species studied, as compared to that of control group of cages without fishes. Natural food preference of the selected fish species was also studied indirectly through gut content analysis.

Seasonal abundance, natural survival & resting behaviour of Phlebotomus papatasi (Diptera: Phlebotomidae) in Pondicherry.

A study was carried out on the seasonal abundance, natural survival and resting behaviour of Ph. papatasi in four ecologically different areas of Pondicherry. The average indoor resting density ranged from 2.25 (May 1989) to 16.70/man hour (October 1989). Ph. papatasi was observed to be predominantly endophilic in its resting behaviour. A significant positive correlation was observed between rainfall and relative density. The daily survival of adult population ranged from 0.893 to 0.949 and showed significant positive correlation with relative humidity. Examination of the abdomen of indoor resting females showed that the entire period of gonotrophic cycle was spent indoors.

Biting rhythm of the vectors of Malayan filariasis, Mansonia annulifera, M. uniformis & M. indiana in Shertallai (Kerala state), India.

Biting activity of Mansonioides mosquitoes through all night collections for a period of two years in Shertallai region, in south India was studied. M. annulifera bites uniformly throughout the night, with two peaks of activity, one after midnight (24.00-01.00 h) and another before dawn (04.00-05.00 h). M. uniformis was found to be predominantly dusk biting, with its peak of activity between 1800 to 1900 h. M. indiana showed two peaks of biting activity one after dusk (2000-2100 h) and another before dawn (0300-0400 h). All biting, with its peak of activity between 1800 to 1900 h. M. indiana showed two peaks of biting activity one after dusk (2000-2100 h) and another before dawn (0300-0400 h). All these species following a particular pattern of activity cycles discerned the biting rhythm of Mansonioides mosquitoes to be species-specific.

Endurance to starvation by the immatures of Toxorhynchites splendens.

Studies on the endurance to starvation by the immatures of T. splendens showed that the III instar larvae survived longer than the I and II instar larvae. The IV instar larvae even in the absence of food pupated and emerged into adults. The irregular supply of food did not affect the perpetuation of the predator in the habitat.

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.

A cost benefit analysis of fish culture strategy towards the control of mansonioides in Shertallai, Kerala state.

The cost benefit analysis of fish culture as a means for vector control towards the containment of Brugian filariasis in Shertallai, a highly endemic tract for this disease in Kerala was carried out. While the financial gain accrued to the community was to the tune of Rs. 1,82,052 in ponds (under monoculture) with Chinese grass carp from 763 ponds, it was Rs. 1,83,740 from 1000 ponds under polyculture with Catla catla, Cyprinus carpio, Labeo rohita, Labeo fimbriatus, Cirrhina mrigala and Ctenopharyngodon idella (Chinese grass carp). Monoculture with Giant gourami (Osphronemous goramy) fetched an income of Rs. 7,654 to the community from 128 ponds. A marked reduction in weed reinfestation/vector breeding was observed in ponds under fish culture than other without fishes. The study clearly indicates that fish culture is an ideal strategy for Mansonioides control as it can bring perceptible benefits to the community.

Impact of 50 years of vector control on the prevalence of Brugia malayi in Shertallai area of Kerala state.

This article examines the long term effects of vector control on the prevalence of B. malayi infection and disease, by comparing the results of 3 earlier studies (1934, 1955, 1976) in one area of south India with a recent (1986) survey. The data indicate that disease and infection prevalence have declined continuously over the last 50 years. Infection has declined (from 21 to 2%) more markedly than disease (from 24 to 10%). Age-specific data indicate that this difference is due to the irreversibility of the clinical signs and the long term survival of diseased cohorts. The results indicate that the prevalence of clinical brugian filariasis can be reduced using vector control and that such control programmes cannot be evaluated in short term or by using crude morbidity statistics.

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.

Giant gourami (Osphronemus goramy: Anabantoidei) as a potential agent for control of weeds, the breeding source for the vectors of Brugia malayi.

The biocontrol efficacy of giant gourami against various aquatic weeds, which form the breeding source of Mansonioides, the vectors of B. malayi, was explored. This fish showed a feeding predilection towards Pistia plant which is the most favoured host of immatures of Mansonioides. A single fish consumed this weed on an average of 206.25 +/- 19.09 g and 316.85 +/- 26.55 g a day under laboratory and field conditions respectively. Techniques developed for the culturing of this fish are also described.

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.

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.

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.

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.

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.

Amblyospora indicola sp. n., a microsporidian pathogen of the mosquito culex sitiens.

A new microsporidian species Amblyospora indicola sp. n., parasite of fat body cells of Culex sitiens larvae, is described. Separation of diplokaryon nuclei occurs during the early sporulation phase of this microsporidian followed by the appearance of synaptonemal complexes in the nuclei suggesting that the first sporogonial division is meiotic.

Megaoesophagus in the mouse: histochemical and ultrastructural studies.

Histochemical and ultrastructural studies of the muscle coat of the oesophagus from ICRC/HiCri mice (with megaoesophagus) and DBA/2fNCri mice (normal oesophagus) were carried out. The striking observation from histochemical studies was the presence of smooth muscle in the abdominal segment of the oesophagus from ICRC mouse in contrast to the control strain where smooth muscle was present only in the lowermost portion adjoining the stomach. Ultrastructural studies of the oesophageal wall from 5- and 10-day-old ICRC mice revealed an apparently normal muscle coat. In 3-month-old ICRC mice the upper abdominal segment of the oesophagus showed several abnormalities of smooth muscle fibres and paucity of plexus tissue accompanied by interstitial collagen deposition. The abnormalities were more severe in 1-year-old animals and were seen throughout the abdominal segment. From this study it is suggested that the primary cause of megaoesophagus in ICRC mice is neurogenic and not myogenic.