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Phlebotomus argentipes is an established vector for Visceral leishmaniasis prevalent in the Indian subcontinent. Insect Glutathione S-transferases (GST) enzyme plays a pivotal role in the metabolism of xenobiotics and chemical insecticides. We report herein the identification and characterization of a delta class GST from the sandfly, P. argentipes. The resulting clone (rParg-GSTδ) is successfully sequenced, which revealed 76.43% and 66.32% gene identity with GST from Phlebotomus papatasi (Scopoli; Diptera: Psychodidae) and Lutzomiya longipalpis (Lutz and Neiva; Diptera: Psychodidae), respectively. The identified rParg-GST amino acid Blast results revealed 82.6% homology to delta class GST of Phlebotomus papatasi and more than 50% homology to Lepidoptera which comprises butterflies and moths. The Phylogenetic analysis of Parg-GST with different classes of Insect GSTs further supported its classification as delta class. A functional recombinant Parg-GSTδ protein (rParg-GSTδ) was expressed in Escherichia coli (Migula; Enterobacterales: Enterobacteriaceae) cells in a soluble form, purified to homogeneity and found to be active against a substrate 1-chloro-2,4-dintrobenzene (CDNB) and lipid peroxidation by-product 4-Hydrxynonenal (4-HNE). Interestingly, rParg-GSTδ demonstrates high dehydrochlorination activity against dichlorodiphenyltrichloroethane (DDT) i.e., 16.27 nM/µg in high performance liquid chromatography (HPLC) assay. These results provide evidence of direct DDT metabolism property exhibited by P. argentipes GST and set the foundation to decipher the metabolic resistance mechanism in P. argentipes against insecticides., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

In order to understand whether organochlorine pesticides and polychlorinated biphenyls (PCBs) are responsible for the mortality of waterbirds in Nalaban bird sanctuary in Chilika Lake, the current investigation was carried out in tissues of 11 individuals comprising 7 species of birds. One or more residues were detected in all the tissues of birds analysed. Concentration of ∑HCH, ∑DDT, and ∑PCBs were ranged from below detectable level (BDL)-811 ng/g, BDL-1,987 ng/g and BDL-1,027 ng/g respectively. PCBs levels were less than the food and drug administration's (FDA) action limits. Although varying levels of residues were detected among tissues, they do not appear to be responsible for the mass mortality of waterfowl. However, the need for additional research is heightened when considering that some of the birds are classified as a globally protected species by the international bodies.

Glutathione S transferases (GSTs) are multifunctional enzymes involved in detoxification of xenobiotic compounds in majority of the insect groups. Significance of insect GSTs is their elevated level of activity in association with insecticide resistance. This investigation was to explore the metabolic status of GSTs in two Indian DDT-resistant malaria vectors, Anopheles culicifacies and Anopheles annularis, and one DDT-susceptible vector, Anopheles fluviatilis. Malkangiri and Koraput districts of Orissa State, endemic for falciparum malaria and having a long insecticide spraying history, were the study areas. F1 progeny was raised from wild-caught females of the three vectors and used for biochemical assays to detect the GST-mediated DDT resistance mechanism. Results of the enzyme assay showed a significant 3-fold increase in GST activity in DDT-resistant An. annularis compared with its susceptible population. In DDT-resistant An. culicifacies, the median GST activity (71.8 micromol/min/mg) was almost the same as estimated in the DDT-resistant An. annularis (74.6 micromol/ min/mg), suggesting that the GST activity estimated in An. culicifacies could be an elevated level for detoxification of DDT. Furthermore, the GST activity in DDT-resistant An. culicifacies and An. annularis was significantly higher than that in the DDT-susceptible An. fluviatilis, which had a GST activity of 20.0 micromol/min/mg. Also, the GST-mediated DDT detoxification was confirmed by comparing GST activity in wild-caught females with that in their F1 progeny.

The residue levels of DDE, op1--DDT and pp1--DDT of the factory workers exposed to DDT formulations having temporary clinical symptoms and of those without any such symptoms did not show any significant difference in their values suggestive of no direct correlation between insecticide residues and ill health symptoms. The average residue values of DDT (mg/litre) and its metabolite DDE (mg/litre) in exposed workers were 0.8634 +/- 0.1529 and 0.2106 +/- 0.0458 respectively while in unexposed control subjects 0.0826 +/- 0.0238 and 0.0278 +/- 0.0040. Total DDT residue in blood in exposed workers is more than 10 times higher than the same in unexposed control.

Blood serum of twenty workers occupationally exposed to DDT for an average duration of 14 years was analysed for organochlorine pesticides by gas-liquid chromatography with an electron capture detector. Significant levels of BHC, p,p'-DDT, p,p'-DDD and p,p'-DDE were detected. A higher incidence of total DDT equivalent, about 10 times, was observed in DDT exposed workers when compared with a comparable sample of unexposed persons from the general population. Levels of DDT in serum of occupationally exposed workers were more than the permitted level of 200 ppb. The daily intake was computed to be about 10 mg/man/day as against 0.25 mg--the acceptable daily intake. Abnormal nerve conduction was encountered in a few cases of DDT sprayers. No significant correlation was observed between the total DDT equivalent in serum and duration of occupational exposure in workers. Levels of BHC in controls was 2.3 times the level in exposed workers, possibly due to induction of hepatic drug metabolising enzymes by high levels of DDT in the latter group. Findings are discussed in the light of existing knowledge of the bio-chemical effects evoked due to residual intoxication of DDT during occupational exposure.

Age, diet and ethnic-dependent excretion of chlorinated pesticides through placenta and milk was studied in women from the general population around Lucknow in India by using gas-liquid chromatography equipped with an electron-capture detector (3H+). Pesticidal contaminants in both placenta and milk were 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDT), its metabolites 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (p,p'-DDD), alpha, beta, gamma - isomers of benzene hexachloride (BHC) and aldrin. The study revealed higher excretion of pesticides through the placentas of older and non-vegetarian women than younger and vegetarian women. There was higher excretion of total DDT in rural than in urban women while a reverse trend was found in the case of total BHC in two ethnic groups. Similarly, age and dietary habits influenced the excretion of these pesticides in milk. Women undergoing premature delivery and stillbirths were found to excrete more DDT in their milk than those undergoing full-term normal delivery.

Adipose tissue of 50 human subjects (10 to 60 years old) were taken from autopsy cases and analysed by gas-liquid chromatography equipped with an electron capture detector (3H +) for determination of storage levels of BHC (benzene hexa chloride), DDT (dichlorodiphenyl trichloroethane) and its metabolites DDE and DDD in human body fat. The data is reported according to age (length of exposure), dietetic habits and area of residence of the subjects. The results show relatively moderate exposure to DDT and BHC. Levels of residues were slightly higher in non-vegetarian and rural residents than those of their counterpart vegetarian and urban inhabitants. The study suggests that DDT levels in human adipose show a decreasing trend as compared to earlier report of Dale et al. of highest body burden of pesticides being present in indians.