Larvicidal and adulticidal activities of castor oil against the dengue vector, Aedes aegypti.

Plants contain numerous bioactive compounds that can be used to develop environmentally-safe insect control agents. Castor oil is a vegetable oil derived from the seeds of castor bean and is widely used as an industrial lubricant and medicinal purgative. In search of an alternative natural insecticide, the objective of this study was to evaluate the larvicidal and adulticidal activities of castor oil against the important dengue vector, Ae. aegypti. Larvicidal and adulticidal bioassays were conducted following the World Health Organization methods. Larvicidal activity was observed at castor oil concentrations of 10, 25, 50, 75, and 100 ppm; larval mortality was checked after 48 h of exposure and the lethal concentration (LC) at LC50 and LC90 were 51.38 and 116.26 ppm, respectively. Adulticidal activity was determined by topical application at the concentrations of 1, 5, 10, 15, and 20 µg/ mg on female mosquitoes and the mortality was checked after 24 h of exposure. The effective adulticidal activity was apparent with the LD50 and LD90 values of 6.03 and 25.07 µg/mg against female mosquitoes. The results indicated that castor oil has potential in the practical control of both immature and adult stages of the mosquito vector.

Larvicidal and adulticidal activities of castor oil against the dengue vector, Aedes aegypti

@#Plants contain numerous bioactive compounds that can be used to develop environmentally-safe insect control agents. Castor oil is a vegetable oil derived from the seeds of castor bean and is widely used as an industrial lubricant and medicinal purgative. In search of an alternative natural insecticide, the objective of this study was to evaluate the larvicidal and adulticidal activities of castor oil against the important dengue vector, Ae. aegypti. Larvicidal and adulticidal bioassays were conducted following the World Health Organization methods. Larvicidal activity was observed at castor oil concentrations of 10, 25, 50, 75, and 100 ppm; larval mortality was checked after 48 h of exposure and the lethal concentration (LC) at LC50 and LC90 were 51.38 and 116.26 ppm, respectively. Adulticidal activity was determined by topical application at the concentrations of 1, 5, 10, 15, and 20 µg/ mg on female mosquitoes and the mortality was checked after 24 h of exposure. The effective adulticidal activity was apparent with the LD50 and LD90 values of 6.03 and 25.07 µg/mg against female mosquitoes. The results indicated that castor oil has potential in the practical control of both immature and adult stages of the mosquito vector.

Differential diagnosis of human lymphatic filariasis using PCR-RFLP.

Filariasis is still a public health problem in tropical countries. The most common causative agents of human filariasis are Wuchereria bancrofti and Brugia malayi. Traditional methods used to detect filarial parasites in human, animal and vector populations are tedious, time consuming, and confer little guarantee of sensitivity and species specificity. We have developed a rapid and specific method to detect filarial parasite DNAs in blood and mosquito samples using the polymerase chain reaction (PCR) technique. The primers used are MF/F and MF/R which amplify a 1.5 kb glutathione peroxidase gene of filarial worms. Using the restriction fragment length polymorphism (RFLP) technique, these PCR products will be further digested with restriction enzymes either Hpa I, Pst I, Alu I or Hinf I to differentiate the genus of filaria. This PCR-RFLP technique can be apply to use in diagnosis and to differentiate between species of filaria in humans the reservoir host and the mosquito vector in endemic areas

Cloning and nucleotide sequencing of a lipase gene from Bacillus subtilis WRRL-B558.

A lipase gene from B. subtilis WRRL-B558 was cloned in Escherichia coli JM109 using pBluescript as a vector plasmid. Two methods were combined to screen for the lipase-producing clone. The first was done by overlaying the screening plates with ß-naphthylacetate and Fast Blue BB dye. Positive clones were then confirmed by a second method using 1% (v/v) tributyrin agar plates. Positive clones which formed clear zones on the tributyrin agar plates were selected and analysed by restriction mapping, Southern blot hydridization and deletion studies to locate the lipase gene on a 2.2 kb HindIII fragment insert. A subclone harbouring a plasmid with a 0.9 kb DNA fragment between the HindIII and EcoRI sites that still exhibited lipase activity was used for sequencing. The nucleotide sequence showed a single open reading frame which contained 636 nucleotides (212 deduced amino acids). A conserved pentapeptide postulated to be the catalytic site was Ala-X-Ser-X-Gly instead of Gly-X-Ser-X-Gly. The deduced protein was found to have a molecular weight of 21 kDa which was similar to that obtained from the recombinant plasmid as determined by SDS-PAGE. Expression of the Bacillus lipase gene was found to be high in recombinant E. coli.

Effects of thalassaemic serum on the in vitro development of the malarial parasite Plasmodium falciparum.

Sera from thalassaemic individuals were experimentally tested for their suppressive effects on the in vitro development of asexual stages of Plasmodium falciparum. Cultures in sera collected from six patients who had classical haemoglobin H disease (alpha-thal1-alpha-thal2) and six patients who had haemoglobin H disease with haemoglobin (Hb) Constant Spring (alpha-thal1-CS) showed a significantly higher degree of inhibition of parasite multiplication than cultures of thalassaemic erythrocytes in sera from healthy individuals. Similarly, sera from 12 patients with beta-thalassaemia/haemoglobin E (beta-thal-HbE) diminished parasite development in vitro. Schizonts of P. falciparum cultured in erythrocytes from non-thalassaemic individuals containing normal Hb (alpha 2 beta 2) were also inhibited when thalassaemic serum was used in place of normal serum. The degree of inhibition was proportional to the concentration (vol/vol) of the thalassaemic serum.