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1.
Bull Entomol Res ; : 1-8, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31337451

RESUMO

Transmission of Trypanosma cruzi (Kinetoplastida: Trypanosomatidae) occurs when feces/urine of infected triatomines come into contact with mucous membranes or damaged skin, and this occurs mainly when insects defecate while feeding on the host. Thus, the vector competence of the triatomines is associated with their feeding and excretion/defecation behavior. This work studied for the first time the effect of T. cruzi infection on feeding and excretion/defecation patterns of Triatoma infestans (Hemiptera: Reduviidae). Uninfected and infected fifth-instar nymphs were fed ad libitum and their feeding behavior and defecations were registered during and after feeding. The feeding pattern did not show differences between the experimental groups. However, the infected nymphs began to defecate earlier, defecated in greater quantity and there was a greater proportion of defecating individuals compared to uninfected nymphs. These results show that T. cruzi affected the excretion/defecation pattern of T. infestans in a way that would increase the probability of contact between infective feces and the mammalian host.

2.
Acta Trop ; 196: 7-14, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31054918

RESUMO

Triatoma infestans (Klug, 1834) is the main vector of the Chagas´ disease in Argentina. The presence of insects in the domestic environment after application of pyrethroid insecticides was reported. The colonization and the evolution of insecticide resistance are processes that can explain these control failures. In both processes, the active dispersal of insects is a determining factor. The aim of the present study was to determine whether the reproductive state modulate the dispersal capacity of females of T. infestans susceptible and resistant to deltamethrin. For this, different variables associated with active dispersal were measured in virgin and copulated females both susceptible and resistant to deltamethrin. The experimental arena was 10 m long and contained two shelters. Groups of 12 females of each experimental group were released in one of the shelters and were able to move during 3 days/nights. The results showed that the females mainly dispersed by walking regardless of the reproductive state and the toxicological phenotype. On the other hand, the copula affected the posterior dispersal capacity in females susceptible and resistant to deltamethrin. The copulated females dispersed more times, leaved more times from the shelters and showed a higher proportion of dispersed individuals than the virgin females. Finally, the insecticide resistance reduced the dispersal capacity of females. The resistant insects showed lower number of dispersal events, a lower proportion of dispersed individuals, and lower exit and entry events from/to shelter than susceptible insects. This is the first report of the effect of copula on the capacity of active dispersion in vectors of Chagas disease susceptible and resistant to insecticides.


Assuntos
Resistência a Inseticidas , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/efeitos dos fármacos , Triatoma/fisiologia , Animais , Argentina/epidemiologia , Doença de Chagas/epidemiologia , Doença de Chagas/transmissão , Feminino , Inseticidas/farmacologia , Reprodução/efeitos dos fármacos , Triatoma/genética
3.
Acta Trop ; 194: 53-61, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30898614

RESUMO

In Latin America, Triatoma infestans is the main vector of the protozoan Trypanosoma cruzi, causal agent of Chagas disease. This blood-sucking triatomine is widely distributed in the Gran Chaco ecoregion, where chemical control has failed because of the evolution of resistance to pyrethroid insecticides. Recently, we described a deltamethrin high resistant focus in Güemes Department (Chaco province) characterized by susceptible populations, populations with low resistance (without field control failures) and some of the populations with the highest resistance level detected. This toxicological heterogeneity could be a result of non-homogenous insecticide pressure and be influenced by environmental factors. The present study evaluated the association of deltamethrin resistance ratios (RR50s) of T. infestans populations with explanatory variables extracted from the WorldClim dataset and constructed from information of National Chagas Program actions during 2005-2015. Control actions were distributed throughout the analyzed period, representing a homogeneous selective pressure. The average percentage of total positive houses was 33.66%. Models that included temperature and precipitation indicators presented 65% explanation. When village size variables where added, the explanatory power reached 70%. This observational result suggests that the climate may favor directly or indirectly the development/selection for resistance, representing a valuable tool to understand the occurrence of resistance that could increase the Chagas disease in the Gran Chaco.


Assuntos
Doença de Chagas/prevenção & controle , Resistência a Inseticidas/efeitos dos fármacos , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/efeitos dos fármacos , Trypanosoma cruzi/efeitos dos fármacos , Animais , Argentina , Interação Gene-Ambiente , Triatoma/crescimento & desenvolvimento , Trypanosoma cruzi/fisiologia
4.
Acta Trop ; 191: 228-238, 2019 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-30653943

RESUMO

The dispersal of insects is determinant in the colonization of new areas and the propagation of insecticide resistance. Nutritional status and reproductive characteristics determine the colonization capacity after the dispersal event. Studies about of the effects of dispersal on reproduction in triatomines are few and none in resistant insects. The aim was to determine the effects of nutritional state and dispersal on the subsequent reproductive potential in Triatoma infestans (Klug, 1834) susceptible and resistant to deltamethrin. Three nutritional states were obtained with the number of feeds (NF) offered (0, 1 or 2). The resistant females were evaluated only with NF1. The experimental arena was 10 m long and contained two shelters. Groups of 30 virgin females of each NF were released in one of the shelters and were able to move during 3 days/nights. Females without possibility of dispersal were the controls. The reproductive parameters were determined on the couples between the experimental females and males from the breeding. The results showed that most of the females dispersed by walking. The dispersal had effects on the reproduction of the deltamethrin-susceptible females and this depended on the number of feeds. Fecundity, fertility and the proportion of females that oviposited were higher in females dispersed with two feeds but was lower in females dispersed with less feeds. In addition, the effect of the dispersal on the reproduction and the life time also depended of the toxicological phenotype. The resistant insect oviposited in higher proportion and showed greater fecundity and more weeks of life when they dispersed that when they did not do it, and was opposite to that observed in susceptible ones. Finally, the resistance to insecticide had an effect on the reproduction and the life span and this effect depended on whether the insects dispersed or not.


Assuntos
Resistência a Inseticidas/efeitos dos fármacos , Inseticidas/toxicidade , Nitrilos/toxicidade , Estado Nutricional/efeitos dos fármacos , Ninfa/efeitos dos fármacos , Piretrinas/toxicidade , Reprodução/efeitos dos fármacos , Triatoma/efeitos dos fármacos , Animais , Feminino , Fertilidade/efeitos dos fármacos , Masculino , Oviposição/efeitos dos fármacos
5.
Med Vet Entomol ; 32(3): 311-322, 2018 09.
Artigo em Inglês | MEDLINE | ID: mdl-29430671

RESUMO

Pyrethroid resistance has been detected in Triatoma infestans (Klug) (Hemiptera: Reduviidae) specimens from different areas of Argentina and Bolivia. Genes conferring resistance can have a pleiotropic effect with epidemiological and evolutionary consequences. This research studied excretion/defecation patterns in deltamethrin-resistant T. infestans in order to elucidate its biological performance, adaptive consequences and role in the transmission of Chagas' disease. One deltamethrin-susceptible strain and two deltamethrin-resistant strains were used. Fifth-instar nymphs were fed ad libitum and their defecations recorded during and after the first or second feeding in the stadium. Resistant insects began to defecate later, defecated less, showed a lower proportion of defecating individuals and lower defecation indices compared with susceptible insects during the first hour after feeding. The number of bloodmeals in the stadium did not affect the main variables determining the pattern of defecation. The present study suggests that alterations in the excretion/defecation pattern in resistant insects entail an adaptive cost and, considering only this pattern, determine a lower capacity for transmission of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) compared with susceptible insects.


Assuntos
Defecação/efeitos dos fármacos , Resistência a Inseticidas , Inseticidas/farmacologia , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/efeitos dos fármacos , Animais , Ninfa/efeitos dos fármacos , Ninfa/fisiologia , Triatoma/crescimento & desenvolvimento , Triatoma/fisiologia
6.
Med Vet Entomol ; 31(4): 414-426, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-28766724

RESUMO

The domiciliary presence of Triatoma infestans (Klug) (Hemiptera: Reduviidae) after control interventions was reported in recent years. Toxicological studies showed high levels of resistance to pyrethroids suggesting resistance as one of the main causes of deficient control. The aim of the present study was to develop a protocol to test resistance to deltamethrin in T. infestans collected from the field by discriminate concentration. To evaluate field insects, the effect of age (early vs. later) and nutritional state (starved vs. fed) on the deltamethrin susceptibility of each developmental stage was studied. Topical and insecticide impregnated paper bioassays were used. Using the impregnated paper, the susceptibility to deltamethrin was not affected by the age of the stadium and the nutritional states, and varied with the post-exposure time and with the different developmental stages. A discriminant concentration of deltamethrin (0.36% w/v) impregnated in filter paper was established for all developmental stages. Finally, the methodology and the discriminant concentration were evaluated in the laboratory showing high sensitivity in the discrimination of resistance. The present study developed a methodology of exposure to insecticide impregnated papers and proposes a protocol to test T. infestans in field populations with the aim to detect early evolution of resistance to deltamethrin.


Assuntos
Resistência a Inseticidas , Inseticidas/farmacologia , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/efeitos dos fármacos , Fatores Etários , Animais , Feminino , Masculino , Ninfa/efeitos dos fármacos , Ninfa/crescimento & desenvolvimento , Triatoma/crescimento & desenvolvimento
7.
J Med Entomol ; 53(4): 880-887, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27113106

RESUMO

Chagas disease is one of the most important parasitic infections in Latin America. The main vector of the protozoan Trypanosoma cruzi in America is Triatoma infestans, a blood-sucking triatomine bug who is widely distributed in the Gran Chaco ecoregion. Control programs in endemic countries are focused in the elimination of triatomine vectors with pyrethroid insecticides. However, chemical control has failed in the Gran Chaco over the last two decades because of several factors. Previous studies have reported the evolution of different levels of resistance to deltamethrin in Tri. infestans Recently, very high resistance has been found in the central area of the Argentine Gran Chaco. However, the origin and the extension of this remarkably resistant focus remain unknown. The aim of this study was to evaluate the geographical variation of deltamethrin susceptibility of Tri. infestans in different endemic provinces of Argentina, with emphasis in the center of the Argentine Gran Chaco ecoregion where this main vector has not been reduced. Populations of Mendoza, San Juan, Santiago del Estero, and Tucumán provinces were all susceptible. Resistant populations were only detected in the province of Chaco, where a mosaic resistant focus was described at the Güemes Department. It was characterized into three pyrethroid resistance categories: susceptible, low, and highly resistant populations. We found the populations with the highest resistance levels to deltamethrin, with resistant ratios over 1000.


Assuntos
Insetos Vetores/efeitos dos fármacos , Inseticidas/farmacologia , Nitrilos/farmacologia , Piretrinas/farmacologia , Triatoma/efeitos dos fármacos , Animais , Argentina , Doença de Chagas/prevenção & controle , Feminino , Geografia , Insetos Vetores/fisiologia , Resistência a Inseticidas , Ninfa/efeitos dos fármacos , Óvulo/efeitos dos fármacos , Triatoma/crescimento & desenvolvimento
8.
Toxicol Lett ; 248: 46-51, 2016 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-26952004

RESUMO

Dose-response relations can be obtained from systems at any structural level of biological matter, from the molecular to the organismic level. There are two types of approaches for analyzing dose-response curves: a deterministic approach, based on the law of mass action, and a statistical approach, based on the assumed probabilities distribution of phenotypic characters. Models based on the law of mass action have been proposed to analyze dose-response relations across the entire range of biological systems. The purpose of this paper is to discuss the principles that determine the dose-response relations. Dose-response curves of simple systems are the result of chemical interactions between reacting molecules, and therefore are supported by the law of mass action. In consequence, the shape of these curves is perfectly sustained by physicochemical features. However, dose-response curves of bioassays with quantal response are not explained by the simple collision of molecules but by phenotypic variations among individuals and can be interpreted as individual tolerances. The expression of tolerance is the result of many genetic and environmental factors and thus can be considered a random variable. In consequence, the shape of its associated dose-response curve has no physicochemical bearings; instead, they are originated from random biological variations. Due to the randomness of tolerance there is no reason to use deterministic equations for its analysis; on the contrary, statistical models are the appropriate tools for analyzing these dose-response relations.


Assuntos
Relação Dose-Resposta a Droga , Modelos Biológicos , Modelos Estatísticos , Preparações Farmacêuticas/administração & dosagem , Farmacologia/estatística & dados numéricos , Toxicologia/estatística & dados numéricos
9.
J Med Entomol ; 52(5): 1036-42, 2015 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-26336260

RESUMO

In this work, we evaluated the effect of environmental variables such as temperature, humidity, and light on the locomotor activity of Pediculus humanus capitis. In addition, we used selected conditions of temperature, humidity, and light to study the effects of cypermethrin and N,N-diethyl-3-methylbenzamide (DEET) on the locomotor activity of head lice. Head lice increased their locomotor activity in an arena at 30°C compared with activity at 20°C. When we tested the influence of the humidity level, the locomotor activity of head lice showed no significant differences related to humidity level, both at 30°C and 20°C. Concerning light influence, we observed that the higher the intensity of light, the slower the movement of head lice. We also demonstrated that sublethal doses of toxics may alter locomotor activity in adults of head lice. Sublethal doses of cypermethrin induced hyperactivated responses in adult head lice. Sublethal doses of DEET evocated hypoactivated responses in head lice. The observation of stereotyped behavior in head lice elicited by toxic compounds proved that measuring locomotor activity in an experimental set-up where environmental conditions are controlled would be appropriate to evaluate compounds of biological importance, such as molecules involved in the host-parasite interaction and intraspecific relationships.


Assuntos
DEET , Inseticidas , Infestações por Piolhos/prevenção & controle , Pediculus , Piretrinas , Animais , Criança , Pré-Escolar , Meio Ambiente , Humanos , Umidade , Luz , Atividade Motora/efeitos dos fármacos , Atividade Motora/efeitos da radiação , Pediculus/fisiologia , Temperatura Ambiente
10.
Med Vet Entomol ; 28(1): 21-5, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23668748

RESUMO

Deltamethrin-based campaigns to control Triatoma infestans (Klug) (Hemiptera: Reduviidae) have decreased in success as a result of the development of insecticide resistance. We compared the in vitro effects of the pyrethroid deltamethrin and two doses of the organophosphate fenitrothion, presented on different materials, on T. infestans from La Esperanza, Argentina. Laboratory tests demonstrated a decrease in susceptibility to deltamethrin in the field population [LD50 : 30.32 nanograms per insect (ng/i)] compared with the reference population (LD50 : 0.13 ng/i), giving a high resistance ratio of 233.42. By contrast, similar susceptibility to fenitrothion was assessed in both the field and reference populations (LD50 : 21.65 ng/i and 21.38 ng/i, respectively). The effectiveness of the formulated insecticides varied according to the surfaces to which they were applied. The application of fenitrothion formulations to glass or brick resulted in mortality of 90-100%. The application of fenitrothion formulations to wood or mud caused mortality in the range of 6.7-56.7%. Resistant insects presented low mortality when exposed to the deltamethrin formulation and high mortality when exposed to fenitrothion formulations. Moreover, the insecticides demonstrated residual activity only when applied to glass. The present work demonstrates that fenitrothion is an alternative to pyrethroids for the management of deltamethrin-resistant insects in La Esperanza. However, this effectiveness is not sustained over time.


Assuntos
Fenitrotion , Resistência a Inseticidas , Inseticidas , Nitrilos , Piretrinas , Triatoma , Animais , Argentina , Relação Dose-Resposta a Droga , Ninfa
11.
J Med Entomol ; 49(6): 1355-60, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23270163

RESUMO

Triatoma infestans (Klug, 1834) (Hemiptera, Reduviidae) is the main vector of Chagas disease in the southern cone South America. Chemical control to the vectors appears to be the best option to reduce the incidence of the disease. However, since 2002, high resistance to insecticides that correlated with field control failures was detected in T. infestans from Argentina and Bolivia. In this paper, we analyzed three T. infestans populations whose pyrethroid-resistance had been recently detected, and we defined at least three resistant profiles according to the toxicological and biochemical characteristics of the studied resistant populations. The resistance profiles were identified as Ti-R1, Ti-R2, and Ti-R3, corresponding to the Argentinean Acambuco, and the Bolivians Entre Ríos and Mataral. Ti-R1 exhibited nymphs and eggs with medium resistance level to deltamethrin (RR = 32.5 and 28.6; respectively). Pyrethroid-esterases played a relevant role in deltamethrin resistance. Ti-R2 exhibited nymphs with high resistance to deltamethrin (RR = 173.8) and low resistance to fipronil (RR = 12.4). Pyrethroid-esterases were involved in resistance. Moreover, eggs showed medium resistance level to deltamethrin (RR = 39.1). Ti-R3 had nymphs with low resistance to deltamethrin (RR = 17.4), and medium resistance to fipronil (RR = 66.8). Pyrethroid-esterases showed increased activity, and eggs possessed low resistance to deltamethrin (RR = 8.4). The characterization of the resistance to pyrethroid in these T. infestans populations from Argentina and Bolivia do not permit the generalization of three forms of resistance profile. So far as we appear to know, the forms of mechanisms and their frequencies reported here are selected independently, so additional sites might well show additional combinations of resistance mechanisms and their frequencies.


Assuntos
Vetores Aracnídeos , Resistência a Inseticidas , Inseticidas , Triatoma , Animais , Argentina , Bolívia
12.
J Med Entomol ; 49(2): 332-5, 2012 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22493851

RESUMO

The major components of geranium (Geranium maculatum L.) oil and their mixtures were tested against female Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae). Chemical analysis by gas chromatography coupled to mass spectrometry revealed four major constituents: citronellol (38%), geraniol (16%), citronellyl formate (10.4%), and linalool (6.45%) (concentration expressed as percentage of total). Topical application demonstrated that the most potent component was citronellol and geraniol, with LD50 values 9.7 and 12.7 microg/insect, respectively. Linalool and Citronellyl formate were less toxic with LD50 values 24.7 and 38.5 microg/insect, respectively. Toxicity of these four major constituents in the same proportion as the natural oil, was greater than whole oil and each individual component. Removal of any four constituents produced a decreased in effectiveness. The absence of citronellol caused the greatest decrease in toxicity (DL50 from 2.2 to 10.9 microg/insect), leading us to conclude that this constituent is the major contributor to oil toxicity. The knowledge of the role of each constituent in the toxicity of the whole oil gives the possibility to create artificial blends of different constituents for the development of more effective control agents.


Assuntos
Geranium/química , Inseticidas/análise , Monoterpenos/isolamento & purificação , Óleos Voláteis/química , Pediculus , Animais , Feminino , Dose Letal Mediana , Terpenos/isolamento & purificação
13.
J Med Entomol ; 47(6): 1077-81, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-21175056

RESUMO

Chagas disease is a major health concern in Latin America, and Triatoma infestans (Klug, 1834) is responsible for the majority of cases of Chagas disease in the continent. After the discovery of deltamethrin highly resistant populations in the neighboring areas to Yacuiba (Bolivia) and Salvador Mazza (Argentina), we studied T. infestans populations north and southward, with the aim of describing the range of the resistant area. In addition, tests were conducted to describe the susceptibility to fipronil in deltamethrin-resistant populations. Tarija populations were highly resistant to deltamethrin, showing that the resistant area is greater than previously reported. Argentinean and Paraguayan populations were susceptible or presented moderate to low levels of deltamethrin resistance. Resistance to fipronil was found in Bolivian populations, although this insecticide was effective against Argentinean populations. This study shows that the Argentinean and Paraguayan populations are currently under successful control with deltamethrin. However, continuous resistance monitoring is necessary. We found that fipronil is a viable option for Argentina, whereas the resistance found in Bolivia implies that new formulations are needed to control T. infestans in Bolivia. Further research is required to find new alternatives of control in those areas that are currently suffering from high infestation rates.


Assuntos
Resistência a Inseticidas , Inseticidas/farmacologia , Triatoma/efeitos dos fármacos , Animais
14.
Parasitol Res ; 105(1): 163-7, 2009 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-19242723

RESUMO

Human pediculosis is produced by Pediculus humanus humanus (Linnaeus 1758) and Pediculus humanus capitis (De Geer 1767). Laboratory-reared body lice, susceptible to insecticides, were used as reference in toxicological studies on head lice. In this work, we evaluated the survival of both subspecies at different temperatures and relative humidities and we propose the optimal conditions for comparative bioassays. Moreover, we used these conditions to test the activity of three monoterpenoids against both lice. The results showed differential response to changes in temperature and humidity between both organisms. The survival of body lice ranged between 83% and 100% and was not affected for the tested conditions. The survival of head lice depended on temperature, humidity, and exposure time. The optimal conditions for head lice were 18 masculineC and 97% relative humidity at 18 h of exposition. The insecticidal activity of three monoterpenoids (pulegone, linalool, and 1,8-cineole), evaluated according the selected conditions by topical application, showed no significant differences between males of body and head lice. To conclude, as head lice required more special laboratory conditions than body lice, the optimal head lice conditions should be used in both organisms in comparative bioassays. Body louse is an appropriate organism for testing products against of head louse.


Assuntos
Umidade , Inseticidas/farmacologia , Monoterpenos/farmacologia , Pediculus/efeitos dos fármacos , Pediculus/fisiologia , Temperatura Ambiente , Animais , Testes de Sensibilidade Parasitária/métodos , Análise de Sobrevida
15.
Fitoterapia ; 79(4): 271-8, 2008 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-18321657

RESUMO

The repetitive and inadequate application of pediculicidal products frequently results in the development of resistance to these compounds. Essential oils are a promising alternative to synthetic insecticides, although their mode of action remains to be explored. It has been proposed that one possible target of the essential oils is the inhibition of acetylcholinesterase (AChE). The role of monoterpenoids as possible AChE inhibitors and their relationship with the toxicity was investigated both in vitro and in vivo. Inhibition of electric eel AChE activity showed that the most effective inhibitor was 1,8-cineole with IC(50) 6 x 10(-3) M. The inhibition of AChE activity of head louse homogenate by 1,8-cineole showed IC(50) 7.7 x 10(-2) M. The intoxication symptoms of head lice exposed to vapors of 1,8-cineole was recorded before the in vivo head louse AChE inhibition assay. No correlation was found between neurotoxic symptoms and inhibition of AChE activity.


Assuntos
Inibidores da Colinesterase/farmacologia , Cicloexanóis/farmacologia , Inseticidas/farmacologia , Monoterpenos/farmacologia , Ftirápteros/efeitos dos fármacos , Acetilcolinesterase/metabolismo , Animais , Inibidores da Colinesterase/química , Cicloexanóis/química , Relação Dose-Resposta a Droga , Electrophorus , Eucaliptol , Inseticidas/química , Monoterpenos/química , Fatores de Tempo
16.
J Med Entomol ; 43(3): 634-5, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16739427

RESUMO

The insecticidal activity of spinosad was evaluated against susceptible and permethrin-resistant human lice. In a permethrin-susceptible strain of the body louse, Pediculus humanus humanus L. (Anoplura: Pediculidae), the toxicity of spinosad was similar to that established for permethrin, with an LD50 value of 1.2 ng/insect and 2.4 ng/insect, respectively. Topical application of spinosad to populations of permethrin-resistant head louse, Pediculus humanus capitis De Geer (Anoplura: Pediculidae), showed that susceptibility to spinosad was independent of resistance to permethrin. The effectiveness of spinosad against human lice and the low mammalian toxicity reported in the literature suggest that spinosad could be useful for the management of permethrin-resistant human lice.


Assuntos
Resistência a Inseticidas , Macrolídeos/farmacologia , Pediculus/efeitos dos fármacos , Permetrina , Animais , Argentina , Combinação de Medicamentos , Dose Letal Mediana
17.
J Med Entomol ; 42(3): 342-5, 2005 May.
Artigo em Inglês | MEDLINE | ID: mdl-15962785

RESUMO

We studied the profile of permethrin resistance in populations of head lice infesting children 6-12 yr old in schools and their homes in and around Buenos Aires, Argentina. Five permethrin-resistant populations with different levels of resistance were collected: Hogar Loyola (HL), Republica de Turquia (RT), Hogar Mitre (HM), Guardia de Honor (GH), and Ricardo Guiraldes (RG). One susceptible population, Bandera Argentina (BA), also was collected. Their level of resistance was evaluated, and results showed resistance ratios of 13 for HL, 16 for RT, 22 for HM, 61 for GH, and 69 for RG. To elucidate the possible involvement of the cytochrome P450 monooxygenase system in conferring permethrin resistance, ethoxycoumarin-O-deethylase (ECOD) activity was measured in abdomens of individual third instars and adults by using a fluorometric assay. The ECOD activity was lower in the susceptible BA population (4.7 ng per louse) than in the resistant ones (13.7 ng per louse for RG, 12.3 ng per louse for GH, 8.6 ng per louse for RT, and 8.2 ng per louse for HL). ECOD activity was significantly correlated with the level of resistance in the field populations (r = 0.97, P = 0.0009), suggesting a role for cytochrome monooxygenase P450 system in permethrin resistance by head louse, Pediculus humanus capitis De Geer.


Assuntos
O-Dealquilase 7-Alcoxicumarina/metabolismo , Resistência a Inseticidas , Pediculus/enzimologia , Permetrina , Animais , Argentina , Criança , Humanos , Infestações por Piolhos/tratamento farmacológico
18.
J Med Entomol ; 40(4): 447-50, 2003 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-14680109

RESUMO

Permethrin has been used extensively for control of Pediculus humanus capitis De Geer (Anoplura: Pediculidae) in Argentina since 1990, resulting in the development of resistance to this and other pyrethroids. This resistance was first detected in some field populations in 1997. A survey for resistance in Buenos Aires in 2001 revealed significant resistance levels in lice on children at 24 of 26 (92.3%) schools. When compared with a previously unexposed reference population, resistance ratios (RRs) obtained by exposing the insects to filter papers impregnated with permethrin ranged from 2 to 60 in 10 (39%) of the schools. RRs in the remaining 14 (61%) populations were too great to not be measured with the filter paper method (RR > 88.7). As an alternative, we used topical applications of 0.1 microl of acetone solution of permethrin on the dorsal abdomen of adults and third instars. This topical method, which has not been previously reported for head lice, was capable of quantifying higher levels of resistance. Highly resistant populations had RRs from 162.5 to 655.2. When applied to populations with low and intermediate levels of resistance, results from the filter paper and topical application methods were highly correlated, and RRs from topical application were higher than those from the filter paper method. Results from the combination of the two methods indicated that head lice among Buenos Aries school children are highly resistant to permethrin, and the resistance is widespread.


Assuntos
Resistência a Medicamentos/fisiologia , Inseticidas/toxicidade , Pediculus/fisiologia , Permetrina/toxicidade , Animais , Argentina , Bioensaio/métodos , Criança , Humanos , Infestações por Piolhos , Instituições Acadêmicas
19.
J Med Entomol ; 39(3): 457-60, 2002 May.
Artigo em Inglês | MEDLINE | ID: mdl-12061440

RESUMO

The effectiveness of 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, and 1-dodecanol was evaluated by immersion method against susceptible and permethrin-resistant head lice, Pediculus humanus capitis De Geer, from Buenos Aires, Argentina. All the tested alcohols showed knockdown effect at 10 min and mortality 18 h after treatment. The highest activity was found for the 1-dodecanol (KC50 2.55%, LC50 2.28%) and the lowest for 1-octanol (KC50 8%, LC50 4.46%). The toxicity to the head lice systematically increased with the increase in carbon atoms in the n-aliphatic alcohol moiety, and with the octanol:water coefficient (r2 = 0.94). The pediculicidal activity of 1-dodecanol was not correlated with resistance to permethrin, because no significant difference was observed between toxicity parameters in the susceptible (MAR) and the permethrin-resistant populations which had different resistant levels (RR 5.77 x for E49 population, RR 9.5 x for HL population and RR > 35.3 x for GH population). The pediculicidal effect of aliphatic alcohols demonstrated in this study and the lack of correlation with the permethrin resistance may prove to have a practical value for use in susceptible and permethrin-resistant head lice control.


Assuntos
Álcoois/farmacologia , Controle de Insetos/métodos , Pediculus/efeitos dos fármacos , Permetrina , Dermatoses do Couro Cabeludo/parasitologia , Animais , Dodecanol/farmacologia , Álcoois Graxos/farmacologia , Resistência a Inseticidas , Octanóis/farmacologia , Dermatoses do Couro Cabeludo/prevenção & controle
20.
J Med Entomol ; 37(5): 721-5, 2000 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-11004784

RESUMO

Permethrin-resistant colonies of Pediculus capitis (De Geer) from Buenos Aires were used to establish a resistance profile and to examine resistance mechanisms. All permethrin-resistant head lice (resistance ratio from 52.8 to > 88.7) were also resistant to d-phenothrin (resistance ratio from 40.86 to > 48.39) and deltamethrin (resistance ratio from 16.24 to 38.06). No cross-resistance to carbaryl was found in any of the pyrethroid-resistant P. capitis tested. Otherwise, all resistant colonies showed low to high levels of resistance to beta-cypermethrin. This pyrethroid had never been applied as a pediculicide in Argentina; however, the high level of resistance found in these permethrin-resistant colonies (resistance ratio from 9.74 to 50.97) demonstrated that pyrethroid cross-resistance occurred to this novel insecticide. Treatment with piperonyl butoxide (PBO) or triphenylphosphate (TPP) significantly decreased the toxicity of permethrin in the four colonies tested. The esterase inhibitor TPP produced lower enhancement of toxicity than the multifunction oxidase inhibitor PBO in the colonies having the highest resistance levels. Results presented here concerning the cross-resistance profile and synergism by enzyme inhibitors in permethrin-resistant head lice demonstrated that enhanced metabolism was involved in the pyrethroid resistance. However, the substantial degree of resistance that remained after synergism suggested the presence of another resistance mechanism. Cross-resistance to pyrethroid and susceptibility to the carbamate carbaryl suggested a common action mechanism.


Assuntos
Inseticidas , Pediculus , Piretrinas , Animais , Argentina , Carbaril , Criança , Dietilexilftalato , Resistência a Medicamentos , Sinergismo Farmacológico , Humanos , Infestações por Piolhos , Organofosfatos , Permetrina , Butóxido de Piperonila , População Urbana
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