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I.v. administration of 100 μg/kg of Dendroaspis angusticeps venom produced a biphasic vasodepressor response. The first fall in blood pressure is due to a cholinergic component, whereas the second fall may be due to central depressant effect. [ABSTRACT FROM AUTHOR]

The success of long-lasting insecticidal nets (LLIN) as the primary method for preventing malaria is threatened by pyrethroid resistance in Anopheles vectors. New generation long-lasting nets incorporating PBO synergist (piperonyl butoxide) with pyrethroid are designed to control insecticide-resistant mosquitoes. The efficacy of Veeralin® PBO LLINs was evaluated in experimental huts against wild free-flying pyrethroid-resistant Anopheles funestus ( s.l. ). Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets, standard LLINs and PBO/pyrethroid combination nets. Blood-feeding rates recorded with 20-times washed Veeralin were not significantly different from those with 20-times washed PermaNet 3.0 LLIN, a WHO Pre-Qualification Team (PQT) approved PBO/pyrethroid LLIN. This provides evidence that Veeralin LLIN provides similar blood-feeding inhibition to the standard approved LLIN and thus meets WHO PQT criteria for blood-feeding. Results show significantly higher mortality for Veeralin PBO LLINs against pyrethroid-resistant Anopheles funestus ( s.l. ) compared to DuraNet, a WHO PQT approved standard pyrethroid-only LLIN, both when unwashed and washed 20 times. The improved efficacy over a standard pyrethroid-only LLIN can be attributed to the effect of PBO in the Veeralin LLIN, hence meeting the Vector Control Advisory Group (VCAG) criteria for a resistance breaking LLIN., (© 2021 The Author(s).)

Background: The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35-7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus., Methods: MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05)., Results: The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN., Conclusion: Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.

Lateral ventricular administration of 100 microgram of Dendroaspis polylepis venom is cats consistently produced a marked rise in arterial blood pressure, heart rate dilatation of pupils and piloerection. This intense central sympathetic discharge occurred after a latent period of 11.7 +/- 0.72 min. Bilateral adrenelectomy abolished the sympathetic discharge showing that central release of catecholamines from the adrenal medulla may play an important role in elicting the cardiovascular response.

Dendroaspis angusticeps venom (75 micrograms/ml) caused an irreversible blockade of the directly as well as directly evoked contractions of the rat hemidiaphragm and indirectly evoked contractions of the chick biventer cervicis muscle. The venom itself also produced a contraction of the frog rectus abdominis muscle, rat fundal strip, rat uterus and nictitating membrane of the cat; however, it did alter responses of nictitating membrane to preganglionic electrical stimulation and to ganglion stimulant drugs. The effect was attributed to the presence of acetylcholine-like substance in the venom.

Whole venom Dendroaspis angusticeps produced a negative chronotropic and ionotropic effect on the heart. Isolation of the fraction (T39) produced the same effect. Negative inotropic effect was blocked by atropine. The bradycardia may be due to a cholinergic effect and the negative ionotropic to a direct depressant effect on the myocardium.

Three fractions were isolated from the venom of Dendroaspis angusticeps by column chromatography on CM-Sephadex C-25. All the three fractions were shown to possess acetylcholinesterase inhibiting activity. The toxicity of the fractions as tested on mice were variable. Although the toxic signs were identical, fraction DaVI was highly lethal (LD50 1.9 microgram/g) whereas fractions DaIV and T39 were less lethal, the LD50 being 3.6 micrograms/g and 4.1 micrograms/g respectively. The three fractions significantly inhibited true acetylcholinesterase to the extent of 91-95%.