Molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones against Oncomelania hupensis in hilly regions / 中国血吸虫病防治杂志

OBJECTIVE@#To establish a snail control approach for spraying chemicals with drones against Oncomelania hupensis in complex snail habitats in hilly regions, and to evaluate its molluscicidal effect.@*METHODS@#The protocol for evaluating the activity of spraying chemical molluscicides with drones against O. hupensis snails was formulated based on expert consultation and literature review. In August 2022, a pretest was conducted in a hillside field environment (12 000 m2) north of Dafengji Village, Dacang Township, Weishan County, Yunnan Province, which was assigned into four groups, of no less than 3 000 m2 in each group. In Group A, environmental cleaning was not conducted and 5% niclosamide ethanolamine salt granules were sprayed with drones at a dose of 40 g/m2, and in Group B, environmental cleaning was performed, followed by 5% niclosamide ethanolamine salt granules sprayed with drones at a dose of 40 g/m2, while in Group C, environmental cleaning was not conducted and 5% niclosamide ethanolamine salt granules were sprayed with knapsack sprayers at a dose of 40 g/m2, and in Group D, environmental cleaning was performed, followed by 5% niclosamide ethanolamine salt granules sprayed with knapsack sprayers at a dose of 40 g/m2. Then, each group was equally divided into six sections according to land area, with Section 1 for baseline surveys and sections 2 to 6 for snail surveys after chemical treatment. Snail surveys were conducted prior to chemical treatment and 1, 3, 5, 7 days post-treatment, and the mortality and corrected mortality of snails, density of living snails and costs of molluscicidal treatment were calculated in each group.@*RESULTS@#The mortality and corrected mortality of snails were 69.49%, 69.09%, 53.57% and 83.48%, and 68.58%, 68.17%, 52.19% and 82.99% in groups A, B, C and D 14 days post-treatment, and the density of living snails reduced by 58.40%, 63.94%, 68.91% and 83.25% 14 days post-treatment relative to pre-treatment in four groups, respectively. The median concentrations of chemical molluscicides were 37.08, 35.42, 42.50 g/m2 and 56.25 g/m2 in groups A, B, C and D, and the gross costs of chemical treatment were 0.93, 1.50, 0.46 Yuan per m2 and 1.03 Yuan per m2 in groups A, B, C and D, respectively.@*CONCLUSIONS@#The molluscicidal effect of spraying 5% niclosamide ethanolamine salt granules with drones against O. hupensis snails is superior to manual chemical treatment without environmental cleaning, and chemical treatment with drones and manual chemical treatment show comparable molluscicidal effects following environmental cleaning in hilly regions. The cost of chemical treatment with drones is slightly higher than manual chemical treatment regardless of environmental cleaning. Spraying 5% niclosamide ethanolamine salt granules with drones is recommended in complex settings with difficulty in environmental cleaning to improve the molluscicidal activity and efficiency against O. hupensis snails.

Field trials of low dose Bayluscide on snail hosts of schistosome and selected non-target organisms in sahelian Cameroon

More than 85 percent of all cases of schistosomiasis in Cameroon occur in the northern sahelian half of the country representing 20 percent of the population. Several workers have advocated the integrated approach to schistosomiasis control, including snail control, but the death and decay of aquatic organisms, and fish kill that often follows Bayluscide application at the dose of 1g/m³ decrease its acceptability. The present study was designed to assess the effect of lower Bayluscide doses on snail host and non-target fish, frog, the tadpole kill. Bayluscide was applied to study ponds at concentrations of 0, 0.25, 0.5, and 1 g/m³ (ppm). Pre and post application assessment of snails hosts of schistosomes, fish, frog, and tadpole kill were carried out. All 0.25, 0.5, and 1 g/m³ Bayluscide concentrations reduced snail population significantly. Bayluscide concentration of 0.50 g/m³ applied in two rounds of 0.25 g/m³ resulted in high snail mortality and low lethality to fish, frogs, and tadpoles. Further studies are needed to assess the cost-effectiveness of Bayluscide in the control of schistosomiasis following the simplified approach.

The effects of clofazimine, niclosamide & amphotericin B, on electron transport of Leishmania donovani promastigotes.

BACKGROUND & OBJECTIVES: The study was undertaken to explore the locus of interaction of clofazimine and niclosamide which showed substantial growth inhibition property in Leishmania donovani promastigotes. METHODS: The uptake of final electron acceptor oxygen and 2,6-dichlorophenolindophenol (DCPIP) reduction in the electron transport chain were measured by constant volume Warburg respirometer and monitoring absorbance at 600 nm, respectively. Irreversibility of O2 uptake inhibition by clofazimine and niclosamide was determined by dilution of cell suspension followed by centrifugation. RESULTS: Clofazimine and niclosamide showed their minimum inhibitory concentration (MIC) at 33 and 150 micrograms/ml, respectively. Oxygen uptake inhibition by clofazimine and niclosamide was not reversed by removal of the drug by centrifugation. Rotenone, a potent inhibitor of mammalian electron transport chain showed no inhibition on the electron transport chain of L. donovani promastigotes. Cyanide at 1 mM concentration showed partial inhibition in L. donovani promastigotes. Oxygen uptake and DCPIP reduction by L. donovani promastigotes were highly sensitive to sulphhydryl group inhibitors. Strong inhibition of oxygen uptake (80-100%) by L. donovani promastigotes was achieved by clofazimine, niclosamide and amphotericin B. Amphotericin B failed to inhibit DCPIP reduction by L. donovani promastigotes, whereas DCPIP reduction was inhibited by clofazimine and niclosamide, respectively. INTERPRETATION & CONCLUSION: DCPIP reduction was mediated by transplasma membrane electron transport as evidenced by its inhibition with membrane impermeable quinone 1,2-naphthoquinone-4-sulphonic acid (NQSA). Transplasma membrane electron transport requires b-cytochromes and sulphhydryl groups for its function and was inhibited by clofazimine and niclosamide.

Repovoamento de criadouros de Biomphalaria glabrata apos tratamento com niclosamida / Repopulation of breeding habitats of Biomphalaria glabrata after treatment with niclosamide

Experimentos foram feitos no laboratorio e no campo nos anos de 1980 a 1984, objetivando detectar as causas do repovoamento de criadouros de Biomphalaria glabrata apos tratamento com niclosamida. Os bioensaios no laboratorio mostraram que a suscetibilidade a niclosamida emulsionavel de B. glabrata coletada mensalmente em um sistema de valas de irrigacao, variou durante o ano. As concentracoes letais 'CL IND. 90' foram 0,15 'mgl POT. -1' a 0,60 'mgl POT. -1', apresentando diferencas significantes estatisticamente (p<0,01) nos meses de maio/82 e janeiro/83 e dezembro/82 e janeiro/83, relacionadas a nutricao. No campo, foram tratados dois tipos de focos com solucao aquosa a 10 ppm de niclosamida. O primeiro era formado por reservatorio com cerca de 12.000 litros de agua e continha 14,5 por cento de moluscos infectados pelo Schistosoma mansoni. Uma unica aplicacao do produto, seguida de esvaziamento e limpeza do reservatorio, eliminou os moluscos. O segundo, era constituido por sistema de valas e poco com 5,6 por cento de moluscos infectados pos S. mansoni. Uma unica aplicacao do produto, sem limpeza das valas, reduziu a densidade planorbidica 98 por cento. As causas da sobrevivencia de 2 por cento dos moluscos do sistema de valas, sao discutidas, sendo relacionadas ao substrato do criadouro e a tecnica utilizada no tratamento.