RESUMO
The present study evaluated the efficacy of fluazuron (active ingredient of the acaricide Acatak®) and its effects on Rhipicephalus sanguineus nymphs fed on rabbits exposed to different doses of this insect growth regulator. Three different doses of fluazuron (20 mg/kg, 40 mg/kg, and 80 mg/kg) were applied on the back of hosts (via "pour on"), while distilled water was applied to the Control group. On the first day of treatment with fluazuron (24 h), hosts were artificially infested with R. sanguineus nymphs. Once fully engorged, nymphs were removed and placed in identified Petri dishes in Biochemical Oxygen Demand (BOD) incubator for 7 days. After this period, engorged nymphs were processed for ultramorphological analysis. The results revealed alterations in the ultramorphology of many chitinous structures (smaller hypostome and chelicerae, less sclerotized scutum, fewer sensilla, fewer pores, absence of grooves, marginal and cervical strips and festoons in the body, even the anal plaque was damaged) that play essential roles for the survivor of ticks and that can compromise the total or partial development of nymphs and emergence of adults after periodic molting. Our findings confirm the efficacy of fluazuron, a more specific and less aggressive chemical to the environment and human health, and that does not induce resistance, in nymphs of the tick R. sanguineus in artificially infested rabbits treated with this arthropod growth regulator (AGR), indicating that it could be used in the control of this stage of the biological cycle of the tick R. sanguineus.
Assuntos
Acaricidas/farmacologia , Compostos de Fenilureia/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Acaricidas/administração & dosagem , Animais , Modelos Animais de Doenças , Ectoparasitoses/parasitologia , Microscopia Eletrônica de Varredura , Ninfa/efeitos dos fármacos , Ninfa/ultraestrutura , Compostos de Fenilureia/administração & dosagem , Coelhos , Rhipicephalus sanguineus/ultraestruturaRESUMO
Research for acaricides with lower toxicity and impact on the environment has been intensified. An alternative would be the use of natural compounds or of synthetic products in lower concentrations than the ones sold commercially. Thus, this study describes the action of andiroba seed oil on the nuclei of the ovary and synganglion cells of Rhipicephalus sanguineus, and presents an analysis of the nuclear morphology of the nervous system cells of this tick species when exposed to permethrin. The results obtained showed that, although no changes have been observed in the genetic material of the ovary cells exposed to the andiroba oil, this compound, as well as permethrin, has neurotoxic action on the females of this species. The damages caused to the physiology of the synganglion, due to the loss of integrity of the genetic material, would result in the impairment of the metabolism of other systems of R. sanguineus ticks.
Assuntos
Sistema Nervoso Central/efeitos dos fármacos , Genitália Feminina/efeitos dos fármacos , Meliaceae/química , Permetrina/farmacologia , Óleos de Plantas/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Animais , Feminino , Óleos de Plantas/química , Sementes/químicaRESUMO
Actually, the most used method to control ticks is synthetic acaricides with neurotoxic action. However, the use of these methods presents inconveniences, such as the contamination of the environment and risks to the host's health due to the residual effects. Thus, several studies have been developed aiming to find alternative ways to control these ectoparasites, such as the use of natural compounds with active ingredients, which act controlling some species of plagues in addition to presenting medicinal properties that are beneficial to humans. The present study aimed to analyze the action of andiroba oil (Carapa guianensis) on the synganglion of Rhipicephalus sanguineus semiengorged females through morphological and cytochemical techniques aiming to verify if this natural product have neurotoxic action as the numerous synthetic acaricides. The results showed that andiroba oil interferes in the synganglion through structural and enzymatic changes, which lead the nervous tissue to apoptotic death involving autophagy. Among these changes was observed the emergence of large empty spaces between the perineurium and the cortical region, vacuolated cortex cells and with cell swelling, neural cells with picnotic nuclei or in initial stage of chromatin margination and neuropile with high structural disorganization. Considering these data, it can be concluded that andiroba seed oil can be used as an alternative method in the control of R. sanguineus ticks due to its neurotoxic action.
Assuntos
Acaricidas/farmacologia , Meliaceae/química , Óleos de Plantas/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Acaricidas/isolamento & purificação , Animais , Apoptose , Feminino , Cistos Glanglionares , Histocitoquímica , Óleos de Plantas/isolamento & purificação , Rhipicephalus sanguineus/anatomia & histologia , Rhipicephalus sanguineus/químicaRESUMO
Studies on the molecular bases of the neurotoxic action of acaricides are found in the literature; but there are no studies of this action on the nervous system of ticks at the cellular level. The present study describes the morphological and cytochemical changes in the synganglion of Rhipicephalus sanguineus semi-engorged females exposed to different concentrations of permethrin, a pyrethroid with recognized neurotoxic action. Permethrin induced the degeneration of the synganglion through a process of apoptosis involving autophagy, characterized by the condensation and margination of the chromatin, formation of blebs in the nuclear envelope and fragmentation of the nucleus, loss of shape of neural cells and integrity of cellular membrane, cytoplasmic shrinkage, and lower levels of acid phosphatase in the nervous tissue as the concentration of permethrin increased. This study provided further evidence of the neurotoxic action of permethrin, which impairs the metabolism of R. sanguineus nervous systems, and consequently the physiology of other systems, dependent on the neural control. These results provide cytochemical and histological confirmation of the neurotoxic action of permethrin, previously inferred from molecular and tick behavioral evidence.
Assuntos
Acaricidas/farmacologia , Sistema Nervoso Central/efeitos dos fármacos , Ixodidae/efeitos dos fármacos , Permetrina/farmacologia , Animais , Sistema Nervoso Central/citologia , FemininoRESUMO
The present study demonstrated the effects of the arthropod growth regulator, fluazuron (Acatak®), in the formation of the integument and digestive processes of Rhipicephalus sanguineus nymphs fed on rabbits treated with different doses of this chemical acaricide. For this, three different doses of fluazuron (20, 40, or 80 mg/kg) were applied "pour on" to the hosts (groups II, III, and IV), as well as distilled water to the control group. On the first day after treatment (24 h), the hosts were artificially infested with R. sanguineus nymphs. After full engorgement (7 days), the nymphs were removed, placed on labeled Petri dishes, and kept in biochemical oxygen demand incubator for 7 days. The engorged nymphs were then taken for morphological, histochemical, and histological analyses. The results showed the occurrence of cytological, morphohistological, and histochemical alterations in the integument and midgut of nymphs from all the different treated groups. These alterations occurred at cuticular level in the subdivisions of the cuticle, related to the size of the digestive cells, amount of accumulated blood elements, and digestive residues, as well as the presence of vacuoles in the cytoplasm of the digestive cells. Thus, this study demonstrated that fluazuron acts on the integument and midgut cells of R. sanguineus nymphs fed on treated rabbits and pointed out the possibility of the use of this chemical-which is more specific, less toxic, and less harmful to the environment and nontarget organisms-in the control of R. sanguineus, at least in the nymphal stage of its biological cycle.
Assuntos
Acaricidas/farmacologia , Ninfa/efeitos dos fármacos , Compostos de Fenilureia/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Animais , Trato Gastrointestinal/efeitos dos fármacos , Trato Gastrointestinal/patologia , Histocitoquímica , Tegumento Comum/patologia , Microscopia , Ninfa/anatomia & histologia , Coelhos , Rhipicephalus sanguineus/anatomia & histologiaRESUMO
Because of the increasing medical-veterinary importance of ticks, the development of alternative control methods, less aggressive to the host and the environment has become the target of several researches. In this sense, the present study analyzed the action of different concentrations (5, 10, and 20%) of andiroba seed oil (Carapa guianensis) on the reproductive system of Rhipicephalus sanguineus females, through histochemical techniques and the quantification of the reproductive efficiency index. The results showed that andiroba oil is a potent natural agent, able to cause several changes in the oocytes of this species, impairing the reproductive success, once this natural product induces great physiological changes in the oocytes in all development stages, such as drastic reduction in proteins, polysaccharides, and lipids in these cells, and these components are essential for the viability of the embryo. In addition, it was observed that this product stimulate the oviposition, mainly at the concentration of 20%. This higher production of eggs represents a defense mechanism developed by the organism in order to ensure the reproductive success of the species, even in the presence of the toxic agent. However, the results obtained suggested that the laid eggs would not be viable, due to the great changes undergone by the oocytes. Thus, the present study showed that the use of this vegetal product would be an alternative way to control the ticks, bringing benefits similar to the ones obtained through the use of synthetic acaricides; however, with less damage to nontarget organisms and the environment as well.
Assuntos
Acaricidas/farmacologia , Meliaceae/química , Óleos/farmacologia , Extratos Vegetais/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Acaricidas/isolamento & purificação , Animais , Feminino , Genitália Feminina/efeitos dos fármacos , Histocitoquímica , Microscopia , Óleos/isolamento & purificação , Extratos Vegetais/isolamento & purificação , Reprodução/efeitos dos fármacos , Sementes/químicaRESUMO
Pyrethroids such as permethrin are synthetic compounds widely used in the agriculture of many countries to combat plagues and in domestic products, such as acaricides. Not so long ago these chemicals were characterized as non-toxic for non-target organisms; however, recent studies have showed that these compounds could present toxic potential for many organisms. In this sense, this study presents genotoxic and mutagenic potential of permethrin administered intraperitoneally in mice under artificial conditions by the use of micronucleus assay in the peripheral blood of these animals. The mice were divided into five groups: group I = negative control (distilled water), group II = positive control (cyclophosphamide), group III = 30% of permethrin LD(50) (96 mg/kg), group IV = 50% of permethrin LD(50) (160 mg/kg), and group V = 80% of permethrin LD(50) (256 mg/kg). The peripheral blood was collected 24, 48, and 72 h after treatment. Results showed that all the tested permethrin dosages presented genotoxic and mutagenic effects 24 h after treatment, which would contradict the classification of this chemical product as moderately toxic, i.e., unable to cause damages to the cell DNA.
Assuntos
Eritrócitos/efeitos dos fármacos , Inseticidas/toxicidade , Micronúcleos com Defeito Cromossômico/induzido quimicamente , Mutagênicos/toxicidade , Permetrina/toxicidade , Animais , Eritrócitos/citologia , Injeções Intraperitoneais , Inseticidas/administração & dosagem , Camundongos , Testes para Micronúcleos , Mutagênicos/administração & dosagem , Permetrina/administração & dosagemRESUMO
The present study performed an analysis about the effects of andiroba seed oil (Carapa guianensis) in the ovary of Rhipicephalus sanguineus semi-engorged females; once, there are few studies about the action of natural products on the reproductive system, a vital organ for the biological success of this animal group. The results showed that andiroba oil is a potent natural agent which causes significant structural changes in the oocytes, such as the emergence of large vacuolated cytoplasmic regions, reduction in the number of yolk granules, changes in the shape of the cells, as well as impairment of genetic material. In addition, the ovary epithelium showed severe morphological changes, such as extreme structural disorganization, with highly vacuolated cells and picnotic nuclei, forming an amorphous mass. This study showed also that oocytes (mainly in the initial stages of development) and the ovary epithelium of R. sanguineus females subjected to different concentrations of andiroba oil presented morphological changes which became more numerous and intense as the concentration of the product increased. Based on the results, it can be inferred that although the defense mechanisms are developed by oocytes to recover the cellular integrity (presence of autophagic vacuoles), these cells are not able to revert the damage caused by this product. Thus, it can be concluded that although the damages caused to the oocytes by andiroba oil are comparatively less severe than the ones caused by synthetic acaricides, this product can be considered a potent natural agent that reduce and/or prevent the reproduction of R. sanguineus females, with the advantage of not causing environmental impact such as synthetic chemical acaricides.
Assuntos
Acaricidas/farmacologia , Meliaceae/química , Óleos de Plantas/farmacologia , Rhipicephalus sanguineus/efeitos dos fármacos , Acaricidas/isolamento & purificação , Animais , Feminino , Genitália Feminina/efeitos dos fármacos , Oócitos/efeitos dos fármacos , Óleos de Plantas/isolamento & purificação , Sementes/químicaRESUMO
Currently the most effective method of tick control is the use of acaricides, among which stands out permethrin (active ingredient of acaricide Advantage(®) Max3, Bayer), a neurotoxic pyrethroid. However, assessments of their effects on other tick systems such as glandular are still scarce. Thus, this study provides information, through histochemical techniques, about the toxic effect of this pyrethroid on the morphophysiology of salivary glands of semi-engorged Rhipicephalus sanguineus females exposed to different concentrations of permethrin (206, 1031, and 2062 ppm). The results showed that permethrin caused significant changes in the salivary gland metabolism accelerating the process of glandular degeneration, an event which would occur naturally and with great intensity only in the final engorgement stage. Furthermore, this study pointed out that permethrin reduces the salivary gland secretion ability through a drastic reduction of proteins, lipids, and polysaccharides in acinar cells. These changes impair the females to finalize the feeding process, what indirectly affects the reproductive process.
Assuntos
Acaricidas/farmacologia , Permetrina/farmacologia , Rhipicephalus/efeitos dos fármacos , Glândulas Salivares/anatomia & histologia , Glândulas Salivares/efeitos dos fármacos , Animais , Feminino , Controle de Ácaros e CarrapatosRESUMO
This study presents the morpho-histological and histochemical characterization of the testes, integument, Malpighian tubules, and midgut of engorged Rhipicephalus sanguineus nymphs on the detachment day, showing the morphological and physiological characteristics to this phase in the life cycle of these individuals. The testis is constituted by germinative cells (only spermatogonia) with large, round-shaped and strongly stained nuclei which are organized into cysts by a thin layer of somatic cells. The integument consists of a cuticle subdivided into epicuticle (lipoprotein) and procuticle (glycoproteic), and a layer of epithelial cells which present glycolipoprotein elements. The procuticle presents two distinct regions: the exocuticle (next to the epicuticle) and the endocuticle (next to the epithelial layer). The Malpighian tubules present a simple epithelium with small flat and/or cubic cells, which form its wall and delimitates a lumen full of lipoprotein material. The midgut consists of an epithelial wall formed by two types of digestive cells, spent cells and empty digest cells, and by generative cells supported by a basal lamina and a thin layer of muscular tissue. This study described the main organs of engorged nymphs of R. sanguineus, to generate information that can help researchers to better understand the biology of these ectoparasites; which is fundamental for the development of compounds that are less aggressive to the environment. In addition, if the immature stages of the ticks are controlled, the number of adult ticks able to cause damages to the animals--and to the man as well--is also under control.