Persistence of DDT, malathion & deltamethrin resistance in Anopheles culicifacies after their sequential withdrawal from indoor residual spraying in Surat district, India.

Background & objectives: Under the national antimalaria programme DDT was introduced in early 1950s for vector control and later hexachloro cyclohexane (HCH) followed by malathion and recently synthetic pyrethroids in 1990s to manage the insecticide resistance in Anopheles culicifacies. Subsequent replacement led to development of multiple resistances in An. culicifacies in Surat district in Gujarat State. Indoor residual spray (IRS) was completely withdrawn in southern villages in Surat in 2002. This study was undertaken in these areas to study the persistence of resistance to DDT, malathion and deltamethrin after sequential withdrawal of IRS with these insecticides at different times. Methods: Susceptibility tests on An. culicifacies were conducted using standard WHO methods and kits. Mortality, knockdown time and lethal times were calculated for An. culicifacies exposed to WHO prescribed diagnostic concentrations of different insecticide impregnated papers. Results: Persistence of DDT-resistance was observed even after 30 yr of its withdrawal from IRS. Similarly, persistence of malathion resistance was also observed after 9 yr of its withdrawal from IRS, while reversal of deltamethrin-resistance was observed very fast within 2-3 yr after its withdrawal from IRS in 2002. Interpretation & conclusion: Present data indicate that the quantum of reversion of insecticide resistance in a population is relative and depends on the genetic stability of the respective resistance genes in the mosquitoes. In the present study withdrawal of pyrethroid-IRS resulted in increased susceptibility against pyrethroids alone and was independent of existence of resistance to insecticides of other groups. This study emphasizes that appropriate rotation of different insecticides; including carbamates may prevent or delay the onset of resistance.

Insecticide susceptibility status of Aedes aegypti to DDT and dieldrin in desert and non-desert parts of Rajasthan.

Seasonal prevalence and insecticide susceptibility tests were carried out on the adults of Aedes aegypti, the vector of dengue and dengue hemorrhagic fever(DF/DHF), in three desert (Bikaner, Jaisalmer and Jodhpur) and three non-desert (Alwar, Ajmer and Jaipur) districts of Rajasthan. Among the three species viz. Ae. aegypti, Ae. vittatus and Ae. w-albus encountered during the survey the former was the most prevalent species. Studies were carried out both in rural and urban areas against different concentrations of two organochlorines (DDT and Dieldrin). In rural areas resistance has been observed with DDT and dieldrin both in desert and non-desert parts while an intermediate resistance has been observed in the urban areas with both the insecticides which required further verification. Resistance was more pronounced in rural areas as compared to urban areas. LC50 along with regression equation and Chi-square values have been determined for both the insecticides.

Promotion of aflatoxin B1-induced hepatocarcinogenesis by dichlorodiphenyl trichloroethane (DDT).

A study of the effect in rats of dichlorodiphenyl trichloroethane (DDT) on hepatocarcinogenesis that is initated by aflatoxin B1 (AFB1). In the first experiment, Buffalo rats were given a single oral dose of AFB1 (5 mg/kg) followed by dietary DDT (100 ppm) for 20 weeks. Neoplastic nodules were observed in 1 of the 14 AFB1-exposed rats, compared with 3 of the 19 rats in the AFB1/DDT group. In the second experiment, Wistar rats were given dietary aflatoxin B, (4 ppm) for 6 weeks followed by a 6-week exposure to DDT (500 ppm) in a plain semisynthetic diet. Five altered hepatic foci were displayed by seven rats in the AFB1 group, compared with 6 foci and one neoplastic focus in five of the AFB1/DDT rats at 32 weeks. Subsequently, the AFB1 group produced 8 (27.5%) tumor-bearing rats while 10 of the 28 (35.7%) AFB1/DDT-exposed rats were tumor-bearing by 60 weeks. The results suggest that DDT slightly potentiates hepatocarcinogenesis induced by either a single dose of AFB1 or short term-dietary AFB1.

Acute hepatotoxicity of DDT: effect on glucocorticoid receptors and serum transcortin.

The hepatotoxic effect of 1,1 bis (p-chlorophenyl) 2,2,2 trichloroethane (DDT) treatment for 10 consecutive days has been examined in Wistar rats. DDT exposure increased relative liver weight, dose dependently, with a marked decrease of glycogen content and profound histological changes including cytoplasmic vacuolization, signs of necrosis and nuclear enlargement. The hepatomegaly induced by DDT (50 and 100 mg/kg body weight day-1) appeared not to be accompanied by a significant alteration of the hepatic glucocorticoid receptor concentration and affinity while, serum corticosteroid binding globulin level increased slightly with the lower dose of the pesticide. It is concluded that a short-term exposure to DDT did not lead to a status stress and, therefore, the hepatotoxic effect of organochlorine seemed not to be mediated by endogenous glucocorticoids.

Organochlorine pesticide-induced oxidative stress and immune suppression in rats.

Effects of subchronic DDT and lindane exposure were evaluated on lipid peroxidation, antioxidant mechanisms and humoral immune response in rats. Oral administration of DDT, (100 and 200 ppm) and lindane (40 and 80 ppm) dose dependently increased thiobarbituric acid reactive substance (TBARS) levels in serum after 8 wk of treatment. Superoxide dismutase (SOD) activity in red blood cells (RBC) was also dose dependently increased by these compounds. In addition, such DDT or lindane exposure markedly suppressed the humoral immune response as assessed by anti-sheep RBC antibody titres. Simultaneous treatment with ascorbic acid (100 mg/kg) markedly attenuated the effects of DDT and lindane on (a) lipid peroxidation, (b) SOD activity and (c) humoral immune suppression. These results indicate the possible involvement of free radicals in organochlorine-induced immunotoxicity.

Influence of dietary protein on DDT-induced immune responsiveness in rats.

The influence of protein deficiency was evaluated on immune responsiveness after subchronic DDT exposure in albino rats. Rats were given 20%, 12% and 3% protein diets and exposed to DDT (20, 50 or 100 ppm) for 4 weeks. DDT (50 and 100 ppm) induced humoral and cellular immune suppression only in rats fed on 3% protein diet. There was (a) an increase in the albumin/globulin ratio, (b) suppression in IgM and IgG levels, and (c) attenuation in the tetanus toxoid-induced antibody responses. Further, in rats immunized with tetanus toxoid, the leucocyte and macrophage migration inhibition were also attenuated. Moreover, these animals maintained on 3% protein diet showed depression in humoral and cellular immune responses to antigen in a dose-dependent pattern after exposure to DDT at dose levels which were not immunosuppressive for rats on 12% or 20% protein diet. These results suggest that dietary protein content may predispose to the immunotoxic effects of DDT exposure, and also be a crucial determinant in DDT detoxification.

Hepatic mixed function oxidase system and effect of phenobarbital, 3-methylcholanthrene and 1, 1, 1-trichloro-2, 2-bis(p-chlorophenyl)ethane in developing chickens.

Contents of hepatic microsomal protein, aminopyrine N-demethylase, acetanilide hydroxylase, aniline hydroxylase, hydrogen peroxide formation, cytochrome-c-reductase, cytochrome b5 and cytochrome P-450 were examined in control, phenobarbital (PB), 3-methylcholanthrene (3-MC) and 1, 1, 1-trichloro-2, 2-bis(p-chlorophenyl)ethane (DDT) treated group of 1-28 days old chickens. Increase in aminopyrine N-demethylase, acetanilide hydroxylase, aniline hydroxylase, cytochrome-c-reductase, cytochrome b5 and cytochrome P-450 was noticed at all stages of development during administration of PB and 3-MC. But these enzyme activities were not always paralleled by increase in age. Aminopyrine N-demethylase was increased in early stages only during DDT administration, which indicates that the form of cytochrome P-450, responsible for aminopyrine N-demethylation is present in early stages only. However, acetanilide hydroxylase was decreased in all stages of development, in postnatal development the basal activities of the enzymes for various substrates do not exhibit identical pattern, the degree of inducibility by inducers varied in relation to age of animal. Hydrogen peroxide formation increased in all stages of developing chickens due to the administration of PB and DDT. It however decreased due to 3-MC administration which may be due to induction of high spin cytochrome P-450.

Plaguicidas organoclorados / Chlorinated organic pesticides

A utilizaçäo, a cerca de 40 anos, dos praguicidas organoclorados para o controle de vetores transmissores de enfermidades do homem e para o desenvolvimento da agricultura, tem ocasionado sérios problemas de contaminaçäo ambiental, com efeitos adversos para a saúde. Este manual pretende proporcionar informaçäo básica sobre os praguicidas organoclorados e seus efeitos sobre a saúde, fornecendo elementos técnicos mais adequados e úteis para as autoridades sanitárias e equipes de saúde que estäo interessadas em desenvolver um sistema de vigilância,prevençäo e controle das intoxicaçöes. Inclue histórico, evoluçäo mundial do uso, propriedades mais importantes, estrutura química, comportamento no ambiente, principais usos e efeitos adversos sobre as diversas formas de vida,características toxicológicas e medidas de prevençäo e controle

Toxicidade do DDT: formulaçäo para alevinos de Tilapia sp / Toxicity of DDT: formulation to Tilapia sp alevin

Alevinos de Tilapia sp foram submetidos a diferentes concentraçöes de DDT formulaçäo (pó molhável) no período de 24 h - 96 h, em testes semi-estáticos. Na montagem dos bioensaios utilizou-se água doce reconstituída (APHA, 1985) e, para a dissoluçäo do DDT o solvente foi acetona p.a. Testaram-se concentraçöes na faixa de 0,5 ppb a 60,0 ppb. Nos testes de apenas 24h, a concentraçäo máxima näo letal foi de 11,9 ppb apresentando-se, porém, bastante reduzido (1,0 ppb) nas primeiras 24 horas da segunda etapa (testes de 24h - 96h). Para 96h o valor máximo näo letal foi de 0,5 ppb. Os valores calculados de CL50 24h e 96h foram, respectiamente, 51,7 ppb e 2,5 ppb. Os animais expostos a concentraçöes letais de DDT evidenciaram alteraçöes fisiológicas e comportamentais (tegumento escurecido, hiperatividade, movimentos convulsivos, perda de equilíbrio, letargia e aceleraçäo do batimento opercular). Tais alteraçöes se instalaram mais rapidamente nas concentraçöes mais elevadas

Avaliaçäo de um questionário utilizado em uma pesquisa de níveis de inseticidas organoclorados em leite humano / Evaluation of a questionnaire used in a research on organochlorine insecticides levels in human milk

O questionário utilizado em uma pesquisa sobre níveis de inseticidas organoclorados no leite humano é apresentado com o objetivo de divulgá-lo e para facilitar posteriores estudos do assunto, ou de áreas correlatas. O mesmo questionário consta de perguntas relacionadas à identificaçäo da mäe, ao(s) parto(s) e ao aleitamento; ao hábito de fumar, à profissäo e ao grau de instruçäo; às condiçöes de salubridade e de moradia, ao uso de clorados na residência, na horta, no pomar ou na lavoura. As dificuldades, surgidas a partir da análise dos dados quando correlacionados aos parâmetros, säo avaliadas e é sugerida a inclusäo de alguns itens no questionário, como questöes sobre os hábitos alimentares, maiores detalhes a respeito do hábito de fumar e, além desses, registro do peso da criança, no caso de se estimar a ingestäo diária da substância em estudo, através do leite humano.

Determinaçäo dos níveis séricos de inseticidas organoclorados em indivíduos näo expostos da Faculdade de Farmácia da UFMG / Determination of serum levels of organochlorine insecticides in unexposed individuals from the School of Pharmacy of UFMG

Trinta amostras de sangue foram coletadas de indivíduos da Faculdade de Farmácia da UFMG e analisadas para determinaçäo dos níveis residuais séricos de inseticidas organoclorados. Todas, provenientes de indivíduos sem qualquer exposiçäo ocupacional a estes compostos. O método utilizado para igual volume de ácido fórmico, visando liberaçäo dos inseticidas de suas ligaçöes plasmáticas, permitindo a extraçäo destes com n-hexano. A identificaçäo dos inseticidas foram realizadas por cromatografia gasosa com detector de captura de elétrons. Todas as amostras analisadas evidenciaram a presença do pp'DDE, principal metabólito do DDT, diclorodifeniltricloroetano encontrado no sangue, numa concentraçäo que variou de 0,32 a 6,95 mg/dl e b HCH (isomero b do hexaclorociclohexano) em 33% das mesmas, numa concentraçäo que variou de 0,21 a 0,85 mg/dl, sendo que, em apenas 10%, evidenciou-se a presença do aHCH (isomero a do hexaclorociclohexano) numa concentraçäo de 0,07 a 0,09 mg/dl. A presente pesquisa foi realizada, visando obtençäo de dados adicionais sobre níveis residuais séricos destes compostos.