Cytotoxic Effects of Extract of Acmella oleracea in the Ovaries and Midgut of Rhipicephalus sanguineus Latreille, 1806 (Acari: Ixodidae) Female Ticks.

The present study investigated the effects of different concentrations of Acmella oleracea extract on the germinative cells and digestive processes of semi-engorged Rhipicephalus sanguineus females. For this experiment, 150 ticks were divided into five groups (30 individuals each). The animals were immersed for 5 min in different concentrations of the extract, distilled water, or ethanol 50%/DMSO 1%, dried, and kept in biological oxygen demand incubator for 7 days. The alterations were associated with the size of germinative cells and yolk granules; presence, size, and location of vacuoles in the cytoplasm of germinative cells; nuclear modifications in the germinative cells; damages to the nucleus and cytoplasm of the midgut generative cells; size of digestive cells; number of captured blood elements; accumulated digestive residues and digestive vacuoles in the digestive cells cytoplasm; and the number and distribution of proteins and polysaccharides in all the cells of both organs. The concentrations used in this study prevented an efficient and complete blood digestion by the midgut epithelial cells of the treated animals, resulting in the absence of the necessary nutrients to maintain the physiological events in the ectoparasites. In advanced stages, This can lead the ectoparasite to death. The germinative cells were highly impaired and probably not able to advance developmental stages (I-V) or complete vitellogenesis to be released during ovulation, which would prevent the females from originating a new individual. Thus, it can be concluded that the effects of A. oleracea are similar to those caused by chemical products widely recognized as effective to control ticks.

Effects of carvacrol on oocyte development in semi-engorged Rhipicephalus sanguineus sensu lato females ticks (Acari: Ixodidae).

Currently, the most commonly used method to control ticks is the use of synthetic acaricides. However, these compounds are potentially harmful to hosts and the environment, in addition to causing the selection of resistant individuals. Therefore, several studies have been conducted to find sustainable methods to control ticks, such as Rhipicephalus sanguineus sensu lato, the most important vectors of pathogens for dogs. There has been increasing research on natural products with acaricidal action, especially with regard to plant-derived compounds as carvacrol, an aromatic monoterpene with several biological properties, including repellent and acaricidal activities, besides exerting cytotoxic effects on the exposed ticks. The objective of the present study was to evaluate the action of different carvacrol concentrations on the ovaries morphophysiology in semi-engorged R. sanguineus s.l. females to determine its effect on oocyte development. The results showed the occurrence of significant morphological alterations in the shape of oocytes (from round-shaped to irregular) and in the germinal vesicles, in addition to extensive cytoplasmic vacuolation.These effects were observed after the application of carvacrol at a concentration of 20 µL/mL. The most significant alterations were observed at the highest concentration (100 µL/mL), at which the oocytes could not develop further than stage II (total absence of oocytes III, IV and V). These data showed that even though carvacrol was unable to kill all ticks at these concentrations, surviving females could have had an altered reproduction, which would hinder the generation of new individuals, resulting in a long-term control. Data regarding the inhibition of oocyte development are unprecedented and indicate the use of carvacrol as a natural product with the potential to control R. sanguineus s.l. ticks.

The effects of neem oil (Azadirachta indica A. JUSS) enriched with different concentrations of azadirachtin on the integument of semi-engorged Rhipicephalus sanguineus sensu lato (Acari: Ixodidae) females.

Several studies searching for methods to control Rhipicephalus sanguineus s.l., (dog tick) infestations have been developed aiming to minimize the damages caused by these ectoparasites to the hosts and the environment, which is harmed by the indiscriminate use of toxic acaricide products. In this scenario, neem oil has been used as a natural alternative against ticks, once this chemical has repellent properties and interferes in the growth regulation of these ectoparasites, inhibiting ecdysis. The present study evaluated the effects of azadirachtin-enriched neem oil on the integument of semi-engorged R.sanguineus s.l., females through morphohistological techniques. The results showed the occurrence of significant morphological and histochemical alterations, mainly in the females exposed to higher concentrations, which demonstrates the dose-dependent action of the chemical. A decrease in the cuticle thickness was observed, as well as a modification in the distribution of the epithelial cells, which displayed pyknotic and fragmented nuclei, and intensely vacuolated cytoplasm, indicating that these cells would be undergoing death processes. These morphological alterations observed in the integument of the females exposed to the azadirachtin-enriched neem oil encourage the use of this chemical as a strategy to control these ectoparasites.

Detrimental effect of deltamethrin on the central nervous system (synganglion) of Rhipicephalus sanguineus ticks.

Ticks are ectoparasites of medical and veterinary importance, which transmit many infectious agents, causing significant damage to the hosts. The "dog tick" Rhipicephalus sanguineus is responsible for transmitting several pathogens to dogs, motivating researchers to investigate efficient and sustainable control methods. Currently, chemical acaricides currently in use target the central nervous system (synganglion), which is responsible for controlling all the systemic functions of the ticks. Here, the neurotoxic potential of deltamethrin on the synganglion of unfed R. sanguineus female ticks was investigated. The results showed that the synganglion of the females belonging to the control group presented intact morphological characteristics; however, the ones from the treatment group (exposed to 1.5, 3.12 and 6.25 ppm of deltamethrin) displayed alterations, which were increasingly intense as the concentration increased. Observed alterations were mainly in the cortex region and in the neuropile, indicating that the deltamethrin is neurotoxic.

Effect of ricinoleic acid esters from castor oil (Ricinus communis) on the oocyte yolk components of the tick Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae).

Rhipicephalus sanguineus are bloodsucking ectoparasites, whose main host is the domestic dog, thus being present in urban areas and closely located to people. Eventually, this tick species parasitize humans and can become a potential vector of infectious diseases. Methods to control this type of pest have been the focus of many research groups worldwide. The use of natural products is increasingly considered nowadays, due to the low toxicity levels to the host and low waste generation to the environment. This study tested the effect of ricinoleic acid esters from castor oil (as an potential acaricide) on the reproductive system of R. sanguineus females, more specifically on the vitellogenesis process. For this, two groups were established: the control group (CG) and the treatment group (TG) with five rabbits in each (New Zealand White), used as hosts. NaCl and ester were added to rabbits' food and offered to the hosts. After full engorgement, the females were collected and had their ovaries extracted. The ticks ovaries were submitted to histochemical techniques so the effects of esters could be observed over polysaccharides, proteins and lipids yolk. Changes in the deposition of yolk components were observed. This caused modifications on elements of polysaccharide origin and on glycoprotein compounds, interfering in the final yolk synthesis and compromising the development of the future embryo.

Ultrastructural changes in the ovary cells of engorged Rhipicephalus sanguineus female ticks treated with esters of ricinoleic acid from castor oil (Ricinus communis).

Rhipicephalus sanguineus is a widely distributed tick species that has adapted to the urban environment, and the dog is its main host. This species is also known as a vector and reservoir of diseases caused by bacteria, protozoa, and viruses. Currently, acaricides of synthetic chemical origin have been widely and indiscriminately used, leading to the development of resistance to these products by ticks and causing damage to the environment. Thus, these issues have made it necessary to seek other forms of controlling these ectoparasites. R. sanguineus was artificially infested in host New Zealand White rabbits, which were divided into four treatment groups: control (CG1 and CG2) and treatment (TG1 and TG2) groups. TG1 and TG2 hosts were provided with feed supplemented with esters of ricinoleic acid from castor oil at a concentration of 5 g/kg of feed for 7 and 15 days. Afterward, the ovaries of the female ticks were removed for analysis by transmission electron microscopy. The results showed ultrastructural changes in the somatic and germ cells of ovaries from TG1 and TG2 females, particularly with respect to chorion deposition, a protective membrane of the oocyte, as well as in the transport process of vitellogenic materials via the hemolymph and pedicel cells. Moreover, the mitochondria were less electron-dense and had cristae that were more disorganized than the mitochondria from CG1 and CG2 individuals. Thus, this study demonstrated the action of esters on the ovaries of R. sanguineus, signaling the prospect of a way to control this ectoparasite without affecting nontarget organisms or the environment.

Effects of Ricinus communis oil esters on salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae).

This study showed the interference of esters extracted from Ricinus communis in the secretory cycle of salivary glands of Rhipicephalus sanguineus ticks, which consequently caused collateral effects on their feeding process. Ticks attached on hosts which were fed with commercial feed containing different concentrations of R. communis oil esters suffered damages such as cytoplasmic changes in their salivary glands, notably in the acinar cells, impairing the functioning of the acini and accelerating the organs degeneration as a whole. It was found that esters interfered with the activity of cellular secretion by changing the glycoprotein of salivary composition especially in acini II cells. It was also shown that the damages caused by esters in the salivary glands cells of these ectoparasites increased in higher concentrations of the product and degenerative glandular changes were more pronounced.

Effects of ricinoleic acid esters from castor oil of Ricinus communis on the vitellogenesis of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) ticks.

This study examines the effects of ricinoleic acid esters from Ricinus communis castor oil on the vitellogenesis of Rhipicephalus sanguineus ticks attached to hosts that were fed with commercial rabbit food containing these esters. The oocytes of ticks from the treatment group (TG) showed cytoplasmic changes that inhibited the development of oocytes I and II to the advanced stages (IV and V) in addition to preventing the maturation of oocytes V, resulting in small ones. In addition, sperm was not observed in ampoules. Our findings confirm the acaricide potential of ricinoleic acid esters.

The dynamics of RNA participation in the vitellogenesis of Rhipicephalus sanguineus ticks Latreille 1806 (Acari:Ixodidae). I. Nucleoli or Cajal bodies?

To understand the morphological and histological aspects of internal systems of ticks has become important matter since these arthropods have an impact in the areas of the economy and public health. In this context, this study has provided morphological data on female germinative cells of Rhipicephalus sanguineus ticks, ectoparasites of dogs that maintain a close relationship with human on a daily basis. Oocytes of engorged females were analyzed, through the PAS reaction (detection of polysaccharides) counterstained by methyl green (detection of RNA) revealing information that allowed to infer for the first time the presence of Cajal bodies, in the germinal vesicles (nuclei) of developing oocytes, as well as showing how the RNA and the polysaccharides are involved in the dynamics of the vitellogenesis in this species.

Efeito de produtos fitossanitários químicos utilizados em alface e crisântemo sobre fungos entomopatogênicos / Effect of chemical products used in lettuce and chrysanthemum on entomopathogenic fungi

The effect of eight fungicides and twelve insecticides used in lettuce and chrysanthemum crops, was evaluated on the fungi Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metsch.) Sorok., Paecilomyces fumosoroseus (Wise) (Holm ex SF Gray) and Verticillium lecanii (Zimmerman) through in vitro tests. The products were added to petri dishes containing culture medium (PDA), according to the concentrations recommended for application in field. After the inoculation of the fungi, the plates were incubate at 25±1°C, 12h fotophase and 70±10 percent relative humidity. The mean diameter of colonies and the number of conidia produced after a variable period of incubation for each studied fungus were evaluated. The insecticides thiametoxan and imidacloprid were compatible with all the fungi studied. On the other hand, cuprous oxide, iprodione, methyl parathion, tebuconazol, metalaxil, mancozeb, folpet, fenpropathrin and tetraconazol inhibited the growth of the fungi, being classified as toxicant or very toxicant products to the entomopathogens.

O efeito de oito fungicidas e doze inseticidas, utilizados nas culturas de alface e crisântemo, foi avaliado in vitro sobre os fungos entomopatogênicos Beauveria bassiana (Bals.) Vuill., Metarhizium anisopliae (Metsch.) Sorok., Paecilomyces fumosoroseus (Wise) (Holm ex SF Gray) e Verticillium lecanii (Zimmerman). Os produtos foram colocados em placas de Petri contendo meio de cultura (BDA), nas concentrações recomendadas para aplicação em campo. Após a inoculação dos fungos, as placas foram incubadas em sala climatizada a 25±1°C, fotofase de 12h e umidade relativa de 70±10 por cento. Foram avaliados o diâmetro médio das colônias e o número de conídios produzidos após um período de incubação variável para cada fungo estudado. Os inseticidas tiametoxam e imidaclopride foram compatíveis com todos os fungos estudados. Por outro lado, óxido cuproso, iprodione, paratiom metílico, tebuconazole, metalaxil, mancozebe, folpete, fenpropatrina e tetraconazole inibiram o crescimento dos fungos, sendo classificados como produtos tóxicos ou muito tóxicos aos entomopatógenos.