RESUMO
The increase of contact between natural and rural areas is prominent in Brazil, due to agricultural activities and concern with the environmental conservation. In this context, domestic animals, wild fauna and humans are exposed to mutual exchange of parasites, microorganisms and diseases. We studied tick parasitism of wild carnivores and domestic dogs, and the environmental of questing ticks, in extensive cattle ranch areas intermingled with natural vegetation, and in a natural reserve, both in a region of Cerrado biome, Midwestern Brazil. From 2008 to 2015, we inspected 119 wild carnivores from nine species, and collected six tick species (Amblyomma sculptum, Amblyomma ovale, Amblyomma dubitatum, Amblyomma tigrinum, Dermacentor nitens and Rhipicephalus microplus). The most numerous and infested hosts were Cerdocyon thous, Lycalopex vetulus, Chrysocyon brachyurus, Puma concolor and Conepatus amazonicus. From 139 domestic dogs, we collected A. sculptum, Rhipicephalus sanguineus and R. microplus. From vegetation, samplings resulted in A. sculptum, A. dubitatum, A. ovale, Amblyomma rotundatum and R. microplus, with dominance of A. sculptum. Domestics and wild animals presented high overlapping of infestations by A. sculptum, a generalist and anthropophilic tick species. This tick is the most important vector of the Brazilian spotted fever, a lethal human disease. This fact elicits attention and requires efforts to monitor the presence of pathogens vectored by ticks circulating in this type of agroecosystem, including in other regions of the Brazil, because the most of the natural vegetation remaining have been increasingly immersed in pastures and agricultural matrix.
Assuntos
Amblyomma/fisiologia , Carnívoros , Dermacentor/fisiologia , Doenças do Cão/epidemiologia , Rhipicephalus/fisiologia , Infestações por Carrapato/epidemiologia , Amblyomma/crescimento & desenvolvimento , Animais , Brasil/epidemiologia , Dermacentor/crescimento & desenvolvimento , Doenças do Cão/parasitologia , Cães , Ecossistema , Feminino , Larva/crescimento & desenvolvimento , Larva/fisiologia , Masculino , Ninfa/crescimento & desenvolvimento , Ninfa/fisiologia , Prevalência , Rhipicephalus/crescimento & desenvolvimento , Infestações por Carrapato/parasitologiaRESUMO
The American dog tick (Dermacentor variabilis) is medically and economically important in North America. This species is found across central and eastern North America from the Gulf Coast of Mexico through southern Canada. In parts of this region, D. variabilis is a vector for pathogens that cause diseases in humans and animals. Our aim was to determine whether climate change would affect the distribution of the climatically suitable area for D. variabilis in North America, to aid monitoring for potential future spread of tick-borne pathogens. We developed a species distribution model for D. variabilis to project where climate will likely be suitable for the tick in North America using a maximum entropy method, occurrence records from museum and laboratory archives, and 10 environmental variables relevant to climate requirements for the tick. We used four emissions scenarios from the Intergovernmental Panel on Climate Change's Fifth Assessment Report and 10 climate models from the Coupled Model Intercomparison Project (phase 5) to estimate potential future climate suitability and determine how the tick's distribution could change. Our consensus model projected that the area of suitable climate in North America could increase from present by approximately 50% by 2070. In areas beyond the current northern limit of D. variabilis, climate could become more suitable for the tick than at present, possibly resulting in a northward expansion in Canada, but the potential suitability of the southern range of D. variabilis could decrease, depending on the region and climate model. Due to the ability of D. variabilis to harbor and transmit pathogens, a change in the distribution of this species could also affect the risk of human and animal diseases throughout North America, particularly in the northern range of the tick.
Assuntos
Distribuição Animal , Mudança Climática , Dermacentor/fisiologia , Animais , Canadá , México , Estados UnidosRESUMO
Ticks parasitizing introduced white-tailed deer, Odocoileus virginianus (Zimmermann), on St. John, U.S. Virgin Islands, were recorded during and after drought conditions. Tick infestation prevalences were 22% at the start of the drought (July 2015), 66% at the height of the drought (March 2016), and 35% after the drought had ended (July 2016; n = 67 deer). Samples of ticks from 22 tranquilized deer in July 2016 revealed the presence of two species, the southern cattle tick, Rhipicephalus (Boophilus) microplus (Canestrini), and the tropical horse tick, Dermacentor (Anocentor) nitens Neumann. Both tick species have considerable veterinary importance, especially for cattle and horses, respectively, as nuisance biters and also as vectors of parasitic piroplasms or of Anaplasma marginale Theiler. All 22 deer examined were infested by R. microplus, whereas 14 (64%) of the samples also included specimens of D. nitens. Because of the large numbers of ticks recorded, wild deer on St. John could develop associated health problems (pruritis, alopecia, anemia, low weight gain, tick-borne pathogens and parasites) and could also serve as a source of these ticks for cattle and horses.
Assuntos
Cervos , Dermacentor/fisiologia , Rhipicephalus/fisiologia , Infestações por Carrapato/veterinária , Animais , Secas , Espécies Introduzidas , Prevalência , Infestações por Carrapato/epidemiologia , Infestações por Carrapato/parasitologia , Ilhas Virgens Americanas/epidemiologiaRESUMO
Eclosion of larvae from clustered tick eggs (1, 5, 10, 15, 20, 25, 50, and ±1,000 eggs) of Rhipicephalus sanguineus (Rs), Rhipicephalus microplus (Rm), Amblyomma cajennense (Ac), and Dermacentor nitens (Dn) was investigated at 43, 75, and > 98% relative humidity (RH) and 25 °C. Susceptibility of eggs to dehydration varied among tick species (Rs < Rm < Ac and Dn) and the number of clustered eggs but even singularized eggs of all tested species matured, and larvae eclosed at RH > 98%. A minimum of 25 clustered eggs and relative humidity close to saturation is suggested for quantitative tests on ovicidal activity of acaricides for related tick species.
Assuntos
Dermacentor/fisiologia , Umidade , Ixodidae/fisiologia , Rhipicephalus/fisiologia , Animais , Larva/fisiologia , Óvulo/fisiologia , Rhipicephalus sanguineus/fisiologiaRESUMO
The salivary glands of Anocentor nitens (Neumann,1897) occur in pairs and are located in the anterolateral region of the general cavity, with milky white color and approximately equal sizes. They consist of a secretory portion and an excretion duct. In some glandular acini, all the cells had a basophilic appearance they were stained by hematoxylin, whereas others presented cells with different staining affinities. In this work, we describe the variations observed in these glands during the feeding cycle of ticks [after feeding (0 h) and successively at 24, 48, 72, 96, 120, and 144 h]. The cells stained by hematoxylin were shown to be more reactive to Alcian blue, thus demonstrating the presence of acid glycosaminoglycans, whereas those stained using eosin presented weak or no reaction. A strong reaction was found by the use of the periodic acid-Schiff (PAS) technique, thereby suggesting the presence of glycogen and/or glycoconjugates containing hexose, confirmed by using salivary amylase before PAS, with partial destaining of the slides. Continuing presence of residual staining in these cells suggests the presence of glycoconjugates containing hexose. Cells with nuclei of circular outline and few granules (of different sizes) were found in type II acini, 72 h after collection. Type I acini presented wide lumina and walls composed of larger numbers of cells of cubic to cylindrical shape. The pronounced degranulation shown in this study over the course of the feeding cycle was associated with the release of substances for oviposition.
Assuntos
Dermacentor/citologia , Dermacentor/fisiologia , Histocitoquímica/métodos , Microscopia de Vídeo/métodos , Animais , Feminino , Cavalos/parasitologia , Glândulas Salivares/citologia , Coloração e Rotulagem/métodosRESUMO
In view of the need to combat the generalized spread of resistance in ticks to commercial acaricides, the objective of this study was to evaluate the action of entomopathogenic nematodes (Steinernema carpocapsae, strains Santa Rosa and ALL) on engorged female Anocentor nitens. Five ticks per Petri dish were exposed to concentrations of 500, 5,000, or 25,000 infective juveniles of S. carpocapsae for 72 h. After transferring the ticks to clean plates, biological parameters were analyzed. Related to strains Santa Rosa, the period of pre-oviposition (p = 0.0001), oviposition (p = 0.041), and the mass weight of eggs (p = 0.005) showed significant differences between the control group and treated group. When the strain ALL was tested, the control and treated groups differed between the periods of pre-oviposition (p = 0.001), oviposition (p = 0.001), and egg mass weight (p = 0.01). The egg mass conversion was less significant in the groups when exposed to strains Santa Rosa (p = 0.002) and ALL (p = 0.001) relative to the control. The efficacy of both entomopathogenic nematode strains used in this study was comparable to other biological control agents, showing their potential against A. nitens in the laboratory.
Assuntos
Dermacentor/parasitologia , Controle Biológico de Vetores/métodos , Rabditídios/crescimento & desenvolvimento , Animais , Dermacentor/fisiologia , Feminino , Oviposição/fisiologia , Óvulo/fisiologiaRESUMO
Artificial feeding is an important toll for studying ticks feeding mechanism and transmission of pathogenic agents in the absence of vertebrate host. The objective was to feed artificially of engorged partially females of Dermacentor (Anocentor) nitens, proceeding of infested naturally equines and evaluate the influence of this technique on biological parameters of species. Engorged partially females were collected, weighted and separate by weight in two range of 40 to 60 milligrams and 61 to 100 milligrams. Each range was further sorted in four groups with homogeneous weight which were fed for 6, 12, 24 and 36 hours through capillaries tubes containing citrated bovine blood. It was observed that artificial feeding promoted increase weight of females in both range and definitive times. The Ticks fed artificially for periods more drawn out, had presented parameters of the non-parasitic phase next to the observed ones in conditions to laboratory for this species. Females of D. (A.) nitens partially engorged ingested great volume of blood when submitted to artificial feeding through capillaries tubes, without any effect in their biological parameters.