Toxicity of 6-gingerol and Cymbopogon citratus against Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae): Mortality, detoxifying enzymes, and morphological ultrastructure alterations in lice.

Pediculus humanus capitis (head louse), which causes pediculosis capitis, remains a global health concern. Plant products are efficient alternative pediculicides for treating the human ectoparasite P. h. capitis which is resistant to permethrin. The study evaluates the toxicity and mechanisms of 6-gingerol and Cymbopogon citratus leaf extract on P. h. capitis. Pediculus humanus capitis adult stages were exposed to three different dosages of 6-gingerol and C. citratus crude leaf extract on filter sheets for 5, 10, and 30 min, respectively. The biochemical approach was used to assess the activity of detoxifying enzymes including acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase. Scanning electron microscope (SEM) was used to investigate the ultrastructure of the morphological body of lice. After 30 min, 6-gingerol and C. citratus leaf extract killed P. h. capitis completely. Bioassay periods significantly affected lice mortality (P < 0.05). The LC50 values for 6-gingerol and C. citratus extract were 1.79 µg/cm2 and 25.0 µg/cm2, respectively. 6-Gingerol and C. citratus leaf extract significantly lower AChE and GST activity (P < 0.05). Cymbopogon citratus also caused morphological ultrastructure changes in P. h. capitis, including an irregularly formed head, thorax, abdominal respiratory spiracles, and belly. 6-Gingerol and C. citratus leaf extracts could be used as an alternate pediculicide to decrease P. h. capitis populations.

First report on evaluation of commercial eugenol and piperine against Aedes aegypti L (Diptera: Culicidae) larvae: Mortality, detoxifying enzyme, and histopathological changes in the midgut.

Dengue fever is a worldwide public health problem, and efforts to eradicate it have focused on controlling the dengue vector, Aedes aegypti. This study aims to assess the toxicity and effect of commercial eugenol and piperine on Ae. aegypti larvae through enzyme detoxification and histopathological changes in the midgut. Laboratory-reared Ae. aegypti larvae were treated with various concentrations of commercial eugenol and piperine and observed after 24, 48, and 72 h. Biochemical methods were used to assess detoxification enzyme activity for acetylcholinesterase, glutathione S-transferase, and oxidase, and changes in the midgut were examined using routine histological examination. In terms of larvicidal activity, piperine exceeded eugenol. Piperine and eugenol had LC50 and LC90 values of 3.057 and 5.543 µM, respectively, and 6.421 and 44.722 µM at 24 h. Piperine and eugenol reduced oxidase activity significantly (p < 0.05), but increased acetylcholinesterase and glutathione S-transferase activity significantly (p < 0.05). After being exposed to piperine and eugenol, the food bolus and peritrophic membrane ruptured, the epithelial layer was interrupted and irregular, the epithelial cells shrank and formed irregularly, and the microvilli became irregular in shape. Commercial piperine and eugenol behave as potential larvicides, with processes involving altered detoxifying enzymes, specifically decreased oxidase function and increased GST activity, as well as midgut histological abnormalities.

Assessment of susceptible Culex quinquefasciatus larvae in Indonesia to different insecticides through metabolic enzymes and the histopathological midgut.

Filariasis and virus diseases that are transmitted by Culex quinquefasciatus are still a global health problem. Control of mosquito vectors with synthetic insecticides causes resistance to these mosquitoes to insecticides so that detection of susceptibility of the mosquito larval stage to insecticides is important for evaluating mosquito control programs. The aim of this study was to evaluate the susceptibility of wild-caught Cx. quinquefasciatus larvae in Jakarta, Indonesia, following exposure to temephos, malathion, cypermethrin, and deltamethrin; this was done by examining the detoxifying enzyme activities and histological damage to the larval midgut. Cx. quinquefasciatus larvae were collected from five fields in Jakarta and exposed for 24 h to temephos (1.25, 6.25, 31.25, and 156.25 ppm), malathion (0.5 ppm), cypermethrin (0.25 ppm), and deltamethrin (0.35 ppm). The larvae were then examined for acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase activities using biochemical methods. Histological damage to the larval midgut was examined using routine histopathological methods and transmission electron microscopy (TEM). After 24 h, temephos and deltamethrin led to 100% mortality in the Cx. quinquefasciatus larvae. Temephos and malathion significantly inhibited the activity of AChE, while cypermethrin and deltamethrin significantly inhibited oxidase activity. Histologically, all insecticides damaged the larval midgut, as indicated by irregularities in the epithelial cell (ECs), microvilli (Mv), food boluses (FBs), peritrophic membranes (PMs), and cracked epithelial layers (Ep). The TEM findings confirmed that temephos and cypermethrin damage to the midgut ECs included damage to the cell membrane, nucleus, nucleoli, mitochondria, and other cell organelles. Overall, Cx. quinquefasciatus larvae in Jakarta were completely susceptible to temephos and deltamethrin. Synthetic insecticides may kill Cx. quinquefasciatus larvae through their actions on the metabolic enzyme activities and histopathological midgut.

In vitro experiments of Pediculus humanus capitis (Phthiraptera: Pediculidae) resistance to permethrin and 6-paradol in East Jakarta: Detoxification enzyme activity and electron microscopic changes in lice.

BACKGROUND AND AIM: Pediculus humanus capitis, the human head louse, remains a global health problem. This study evaluated the resistance of head lice to permethrin and 6-paradol mediated by in vitro detoxification enzyme activity experiments and to describe physical changes in the lice using scanning electron microscopy (SEM). MATERIALS AND METHODS: The adult stages of P. h. capitis were collected from patients exposed to 1% permethrin and three different concentrations of 6-paradol (0.00005%, 0.0001%, and 0.00015%) using a filter paper diffusion bioassay. Healthy P. h. capitis adults served as the control. The in vitro bioassays were conducted after 10, 20, 30, and 60 min of exposure. The activities of acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase were analyzed. Physical changes in the lice were analyzed using SEM. RESULTS: Permethrin and 6-paradol exhibited low toxicity against the lice. At 60 min, 1% permethrin had killed 36.7% of the lice present, while 6-paradol had killed 66.7-86.7%. Permethrin induced significantly elevated AChE, GST, and oxidase activity; 6-paradol also caused significantly elevated AChE, GST, and oxidase activity. Permethrin did not cause any ultrastructural morphological changes on the lice, while 6-paradol severely damaged the head, thorax, respiratory spiracles, and abdomen of the dead lice. CONCLUSION: This in vitro experimental of P. h. capitis is the first study to report P. h. capitis in East Jakarta shows complete resistance to permethrin and 6-paradol, and to describe the associated increase in AChE, GST, and oxidase activity. It was observed that 6-paradol severely damaged the head, thorax, respiratory spiracles, and abdomen of the dead lice.