Search

The present study evaluated the presence of Anaplasma species in questing ticks from six sites with opposing land usage (i.e., protected natural areas or livestock establishments) within the Iberá wetlands ecoregion in Argentina. The ticks were determined as Amblyomma dubitatum (n = 15,096), Rhipicephalus microplus (n = 399), Amblyomma triste (n = 134), Haemaphysalis juxtakochi (n = 5), and Amblyomma tigrinum (n = 1). Using a real-time PCR assay targeting the 16S rRNA gene, Anaplasma sp. was detected in A. dubitatum samples (one nymph, three nymph pools and one larvae pool) and one R. microplus larvae pool. The overall minimum infection rate (MIR) for Anaplasma sp. in questing A. dubitatum nymphs was 0.169% (0.175% in protected natural areas and 0% in livestock establishments). For R. microplus, overall Anaplasma sp. MIR was 0.25% (0.52% in protected natural areas and 0% in livestock establishments). Phylogenetic analysis positioned the Anaplasma sp. from A. dubitatum in the same clade as Anaplasma odocoilei, whereas the Anaplasma sp. from R. microplus was related to Anaplasma platys. In conclusion, these results support a possible role of A. dubitatum in the ecology of the Anaplasma agent reported to infect capybaras in the region. [ABSTRACT FROM AUTHOR]

Rickettsia rickettsii infection causes the highest human fatality rate among all Rickettsia species of the world and is endemic in Southeast Brazil. In this part of the country most human spotted fever cases are related to unnaturally high populations of ticks, usually a mix of two species, Amblyomma dubitatum Neumann and Amblyomma sculptum Berlese and their local host, capybara (Hydrochoerus hydrochaeris). At the same time, an increase in the number of SF notifications as well as its urbanization was observed, and a better characterization of disease epidemiology is mandatory for control measures and to halt its expansion. It was recently noticed in southeast Brazil that SF endemic areas were characterized by overgrowth populations of A. sculptum and decreased populations of A. dubitatum. Hence, characterization of areas with potential to endemicity, eco-epidemiological studies and control measures may rely on the evaluation of A. sculptum/A. dubitatum rate. However, in potentially endemic scenarios, discriminating the two tick species, particularly the nymphs considered the main vector stage, is a challenge in face of several hundreds to thousands of ticks that should be examined for quantitative studies. We herein present additional morphological features to an existing identification key for Amblyomma nymphs that considerably diminishes the labor to distinguish nymphs of these two tick species. Specifically, the oval-shaped scutum of A. dubitatum and a conspicuous scapula of A. sculptum are prominent discriminating features. [ABSTRACT FROM AUTHOR]

Natural infestation of Amblyomma dubitatum in relation to individual specific attributes of Hydrochoerus hydrochaeris such as sex, body mass and body condition was analyzed. The anatomical distribution of A. dubitatum on H. hyrochaeris was also evaluated. Prevalence of adults and nymphs were significantly higher than prevalence of larvae. Non-significant differences in the infestation levels were found among host sex. Multiple regression analysis did not show any statistically significant association among the level of infestation with ticks and body mass and body condition of the host. All parasitic tick stages were collected in all five anatomical areas of the host, but they exhibited significant differences in feeding site preference. Factors associated to the host which determine the high levels of infestation with A. dubitatum could be assigned to a combination of population-level properties of the host as abundance, ubiquity and aggregation, rather than individual specific attributes related to body condition, body mass or sex. [ABSTRACT FROM AUTHOR]

The life cycle of Amblyomma dubitatum was described based on the seasonal distribution of all parasitic stages and the development periods of engorged ticks under different conditions of photoperiod and temperature. All stages were found active along the entire year in the study area. Larvae peaked from May to July, nymphs peaked from July to October, and females peaked from November to March. This pattern represents a life cycle with one generation per year with most of the ticks reaching adulthood during the warmest months. The analysis of the effect of the photoperiod on the development of A. dubitatum showed no indication of morphogenetic diapause. Exposure of ticks to field conditions indicates a delay in metamorphosis of immature stages, in the oviposition of females and in the incubation of eggs, which were associated with low winter temperatures. The results indicate that though A. dubitatum has a one year life cycle, more than one cohort can co-exist within the same population in a certain interval of time. Finally, the potential role of small rodents as hosts for larvae and nymphs of A. dubitatum is confirmed. [ABSTRACT FROM AUTHOR]

From 2005 to 2012, ticks were collected from different hosts at different localities of the state of Rondônia. The following 16 ixodid tick species were identified: Ixodes fuscipes, Amblyomma auricularium, Amblyomma coelebs, Amblyomma dubitatum, Amblyomma geayi, Amblyomma humerale, Amblyomma latepunctatum, Amblyomma longirostre, Amblyomma naponense, Amblyomma nodosum, Amblyomma oblongoguttatum, Amblyomma ovale, Amblyomma romitii, Amblyomma rotundatum, Amblyomma scalpturatum, and Amblyomma varium. From these, A. auricularium, A. dubitatum, and A. geayi are reported for the first time in the state of Rondônia. We provide the following tick-host associations that have not been reported anywhere: A. longirostre on Pteroglossus bitorquatus, A. rotundatum on Hydrodynastes gigas, and A. latepunctatum and A. scalpturatum on Hydrochoerus hydrochaeris. An adult male specimen of A. rotundatum is reported on Boa constrictor, comprising only the fourth male specimen to be recorded for this obligate parthenogenetic tick species. We also report the presence of the argasid species Ornithodoros kohlsi for the first time in Brazil, based on larval specimens collected on bats Molossops ( Neoplatymops) mattogrossensis in Monte Negro, Rondônia. The present study increases the Brazilian tick fauna to 65 species, from which 34 species (52 %) are now registered to Rondônia. Such high diversity of ticks in a relatively small state, associated with increasing environmental alteration due to deforestation and human occupation, makes Rondônia a potential source of tick-borne diseases. [ABSTRACT FROM AUTHOR]

In Brazil capybara, the biggest existing rodent species, and associated tick species, Amblyomma cajennense and Amblyomma dubitatum, are undergoing an unplanned host and parasite population expansion in both urban and rural areas. However, scientific information about such issue, particularly in urban areas, is scanty. Such rodent and ticks are associated in some municipalities, particularly in southeastern Brazil, with the transmission of the highly lethal Rickettsia rickettsia caused spotted-fever. In this study ecological aspects related to the establishment and expansion of capybaras and ticks in urban areas of Uberlândia, Minas Gerais State, Brazil were evaluated. For this purpose, capybara and tick abundance in four urban areas and an ecological reserve was determined. Abundance of capybaras varied between areas and over the sampling period and these differences were related to human activities. A positive correlation was found between capybara and tick abundance, however, the tick species had an uneven distribution within the municipality and environmental factors rather than host availability were blamed for such. On the whole these observations show that capybara populations in urban areas are associated to high environmental infestation of ticks and the increased risk of bites and of pathogen transmission to humans. At the same time the uneven distribution of tick species might implicate in an unequal risk of tick-borne diseases within the same urban area. [ABSTRACT FROM AUTHOR]

We supply information about hosts and distribution of Amblyomma dubitatum. In addition, we carry out an analysis of genetic divergence among specimens of A. dubitatum from different localities and with respect to other Neotropical Amblyomma species, using sequences of 16S rDNA gene. Although specimens of A. dubitatum were collected on several mammal species as cattle horse, Tapirus terrestris, Mazama gouazoubira, Tayassu pecari, Sus scrofa, Cerdocyon thous, Myocastor coypus, Allouata caraya, Glossophaga soricina and man, most records of immature and adult stages of A. dubitatum were made on Hydrochoerus hydrochaeris, making this rodent the principal host for all parasitic stages of this ticks. Cricetidae rodents ( Lundomys molitor, Scapteromys tumidus), opossums ( Didelphis albiventris) and vizcacha ( Lagostomus maximus) also were recorded as hosts for immature stages. All findings of A. dubitatum correspond to localities of Argentina, Brazil, Paraguay and Uruguay, and they were concentrated in the Biogeographical provinces of Pampa, Chaco, Cerrado, Brazilian Atlantic Forest, Parana Forest and Araucaria angustifolia Forest. The distribution of A. dubitatum is narrower than that of its principal host, therefore environmental variables rather than hosts determine the distributional ranges of this tick. The intraspecific genetic divergence among 16S rDNA sequences of A. dubitatum ticks collected in different localities from Argentina, Brazil and Uruguay was in all cases lower than 0.8%, whereas the differences with the remaining Amblyomma species included in the analysis were always bigger than 6.8%. Thus, the taxonomic status of A. dubitatum along its distribution appears to be certain at the specific level. [ABSTRACT FROM AUTHOR]