Studies were carried out to observe the species composition of mosquitos and to determine the vectors responsible for the transmission of filariasis in Grik, Perak, Malaysia. A total of 2,155 mosquitos belonging to 7 genera and 30 species were collected. Anopheles donaldi comprised 24.1% of the collection. Twelve out of 519 An. donaldi were infected with L3 larvae of Brugia malayi. The peak biting time was around 23.00-24.00 hours. The infective bites per month ranged from 0 to 6.3.
Matched MeSH terms: Filariasis/prevention & control
Field tests were conducted to compare the degree of protection from bites of Mansonia species and Anopheles maculatus by applying two repellent/insecticidal bars, MOSBAR and MOSKIL, to exposed arms and legs. Human test subjects were exposed to natural populations of mosquitos for an 8-hour night time period while using the repellent/insecticidal bars. MOSBAR gave good protection against the bites of Mansonia and An. maculatus. MOSKIL was effective against An. maculatus but not against Mansonia. High mortality was observed among the mosquitos collected from human test subjects treated with the repellent/insecticidal bars. Use of MOSBAR in terms of cost-effectiveness and safety by field and health workers entering into malaria and filariasis endemic areas is discussed.
The dynamics of the transmission of subperiodic Brugia malayi in a typical endemic area in Malaysia was studied over a period of 4 years. Mass chemotherapeutic control with diethylcarbamazine citrate was found to be inefficient, new cases being detected even after the fifth treatment cycle of 6 mg/kg X 6 days per cycle. This is in marked contrast to the situation in periodic b. malayi areas where mass treatment efficiently controlled the infection. The disparity in results in these two areas is attributed to zoonotic transmission of subperiodic B. malayi from non-human primates where a mean infection rate of 76.3% was found.
Four Presbytis cristata were treated with oral ivermectin at the same time as the subcutaneous inoculation of 100 infective larvae monthly for three months. Two animals given 0.2 mg/kg monthly and two others given 0.3 mg/kg monthly as well as three control animals became patent for microfilaraemia. However, only 1% of the infective dose was recovered as adult worms from animals in the higher drug dosage group compared to 8.2% and 6.2% in the lower dosage and control groups respectively.
The chemoprophylactic use of diethylcarbamazine citrate at total oral doses of 15--180 mg/kg body weight was tested against subperiodic Brugia malayi infection in the leaf monkey (Presbytis melalophos). A total dose of 45 mg/kg body weight given over 9 days killed all developing infective larvae. Similarly, a total dose of 35 mg/kg body weight given over 7 days killed all fourth stage larvae. The minimum effective dose that prevents infection would be 5 mg/kg body weight daily for 7 days every month.
Studies on the social and behavioral aspects of filariasis transmission were conducted in the transmigration area of Kumpeh, in the province of Jambi, Sumatra, Indonesia. Three methods were used in the study namely, interview, participation observation and focus group discussion. A total of 266 respondents (136 males and 130 females) were interviewed. The results of the study showed the most of the transmigrants were not familiar with the word "filariasis". They were more used to the name of "penyakit kaki gajah" or "elephant's leg" disease or "untut". The word "untut" is similar to what people of Selangor, Malaysia call this disease. The community attitude towards control efforts against filariasis was positive, as evidenced by their readiness in being bled and their readiness to help change the environment which serves as mosquito breeding places. Usually the transmigrants live in the "ladang" or dry farming area for 3-4 months to protect their crops from damages by pests. This habit was rather negative, because in their "ladangs" they exposed themselves to high risk of mosquito bites and thus to filariasis infection.
Matched MeSH terms: Filariasis/prevention & control
Two field trials in the control of subperiodic brugian filariasis vectors, mainly Mansonia bonneae and Mansonia dives were carried out in Sarawak, East Malaysia. In the first trial, malathion ultra-low volume (ULV) spray was used to control the Mansonia mosquitos in two filariasis endemic villages. Six spray rounds were applied at biweekly intervals at Kampung Rasau and two spray rounds were applied at monthly intervals in Kampung Triboh. ULV malathion spray reduced biting Ma. bonneae population for 3 days after spraying. The biting density decreased to 50% of the pre-treatment level by the 12th - 13th day and reached the pre-treatment level by the 24th - 25th day. Contact bioassay tests on caged Mansonia mosquitos revealed considerable penetration of the malathion aerosol indoors and relatively adequate coverage outdoors. The estimated number of bites per case per day was 1.09 to 4 times less in the sprayed kampung than in an unsprayed control kampung. The parous and daily survival rates of Mansonia mosquitos were not significantly affected by the spraying. In a second trial, chemotherapy with diethylcarbamazine citrate (DEC) was combined with vector control through indoor residual spraying in Kampung Ampungan. The results were compared with the use of only DEC mass treatment in Kampung Sebangkoi and Kampung Sebamban. The combined control measures in Kampung Ampungan reduced the MfD-50 to 44% of the pre-treatment level over a period of 4 years. In the other two kampungs where only mass DEC therapy was applied, the microfilarial rate and MfD-50 declined significantly in the second blood survey but increased gradually in two subsequent follow-up blood surveys. The total insecticidal impact for Ma. bonneae was 3.9 to 1 indoors and 2.7 to 1 outdoors. These results indicated that quarterly pirimiphos-methyl indoor spraying used in integrated control could reduce indoor transmission by 3.9 times. The infective rate from the Ma. bonneae dissected in all three kampungs after the interventions, irrespective of DEC treatment alone or in combination with pirimiphos-methyl residual spraying were reduced by two fold. However the infection rate of brugian filarial larvae in Kampung Ampungan was significantly reduced after the use of DEC and insecticide. Annual Transmission Potential (ATP) showed a high significant reduction in Kampung Ampungan (p > 0.001) compared with Kampungs Sebangkoi and Schambam. In Ampungan, the ATP was reduced by 8.5 times indoors after the MDA and insecticidal application and 3 times outdoors. The reduction rate for Sebangkoi and Sebamban both indoors and outdoors were less than 2 fold.(ABSTRACT TRUNCATED AT 400 WORDS)
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.
Matched MeSH terms: Filariasis/prevention & control
A multicentre evaluation of the Brugia Rapid dipstick test was performed using 1263 serum samples in four international laboratories, i.e. T.D. Medical College (TDMC, India), National Institutes of Health (NIH, USA), Swiss Tropical Institute (STI, Switzerland) and Leiden University Medical Centre (LUMC, Netherlands). In comparison with microscopy, the dipstick demonstrated sensitivities of 97.2% (70 of 72) at TDMC, 91.6% (175 of 191) at LUMC and 100% (six of six) at STI. Sera of chronic patients showed a positivity rate of 11.3% (19 of 168) and 61.2% (71of 116) at TDMC and LUMC, respectively. All 266 sera of non-endemic normals from STI, NIH and LUMC tested negative with the dipstick. At LUMC, sera of 'endemic normals' (amicrofilaraemics with no clinical disease) from an area with approximately 35% microfilaria positivity showed 60.8% positive results (31 of 51), thus demonstrating the likelihood of many cryptic infections occurring in this population. Specificities of the test with Onchocerca volvulus sera were 98.8% (80 of 81) and 100% (10 of 10) at the NIH and STI, respectively; while specificity with Loa loa sera at the NIH was 84.6% (44 of 52). At the STI, the dipstick test also demonstrated 100% specificity when tested with 75 sera from various protozoan and helminthic infections.
Matched MeSH terms: Filariasis/prevention & control