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Guinea pigs repeatedly exposed to Ixodes scapularisdevelop acquired resistance to the ticks (ATR). The molecular mechanisms of ATR have not been fully elucidated, and partially involves immune responses to proteins in tick saliva. In this study,we examined the metabolome of sera of guinea pigs during the development of ATR. Induction of components of the tyrosine metabolic pathway, including hydroxyphenyllactic acid (HPLA), were associated with ATR. We therefore administered HPLA to mice, an animal that does not develop ATR, and exposed the animals to I. scapularis. We also administered nitisinone, a known inhibitor of tyrosine degradation, to another group of mice. The mortality of I. scapularisthat fed on mice given HPLA or nitisinone was 26% and 72% respectively, compared with 2% mortality among ticks that fed on control animals. These data indicate that tick bites alter the guinea pig metabolome, and that the tyrosine metabolism pathway can potentially be targeted for I. scapulariscontrol.

Rickettsiainfection of each tick was evaluated by the hemolymph test and polymerase chain reaction (PCR) targeting gltA and ompA genes. All hemolymph tests were negative and PCR of one A. dubitatumdetected both Rickettsia genes. Sequence of ompA exhibited a 99% identity with Rickettsia parkeriand R. africaeand a 98% identity with R. sibirica. Rickettsiaof the spotted fever group in A. dubitatumis described for the first time in an urban area within the municipality of Campo Grande in the state of Mato Grosso do Sul (MS), Brazil. This finding reinforces the importance of more detailed studies to determine the role of A. dubitatumin the transmission of spotted fever agents.

Ticks are vectors of various pathogens, including Rickettsiaspp., which are responsible for causing an emerging disease of global significance. In the present study, an epidemiological survey was performed to identify Rickettsiaspp. of the spotted fever group (SFG) in ticks and wild hosts in a native forest adjacent to livestock farming activity. The ticks and blood were evaluated by a hemolymph test and by PCR using the primers CS78 and CS323, which target a partial sequence of the enzyme citrate synthase (gltA) gene. Positive samples by PCR were further tested with the primers Rr190.70p and Rr190.602n, which target a 532-bp fragment of the rickettsial 190-kDa outer membrane protein gene (ompA). In addition, an indirect immunofluorescence assay (IFA) was performed to detect antibodies against Rickettsiaspp. in horses that inhabited the same area. From the 43 animals that were captured, 192 ticks were collected; the ticks belonged to the species Amblyomma cajennense, A. ovale, and A. nodosum. All blood samples and hemolymph tests were negative. Four samples of A. nodosumthat were collected from Tamandua tetradactylawere positive for Rickettsiaspp. by PCR, and 8 samples of horse serum displayed titers greater than or equal to 1:64 by IFA. The phylogenetic analysis based on the DNA sequence of the ompACGgene demonstrated that Rickettsiaspp. CG (the canadensis group) segregate in the same cluster as Rickettsia parkeristrain COOPERI, with a bootstrap value of 78%. These results indicate that Rickettsiaspp. CG circulate among the tick population in the study area, which has a constant presence of livestock and humans. This may be the same species of Rickettsiathat was recorded in A. nodosumthroughout the Atlantic forest.

The aim of this study was to evaluate tick fauna and identify the possible presence of Rickettsiaspp. in ticks of the genus Amblyommafrom two environmental preservation areas in different regions of Mato Grosso do Sul state, Brazil. CO2traps, visual observation and cloth dragging were used to capture ticks. Three hundred ticks were submitted to the hemolymph test, and samples that showed organisms morphologically compatible with Rickettsiawere used for rickettsial DNA detection by PCR. DNA was extracted using guanidine-phenol isothiocyanate, and the primers CS78 and CS323 were used for PCR, which amplified a 401-base pair fragment of the citrate synthase (gltA) gene. If positive, the DNA sample was tested by primers Rr190.70p and Rr190.602n that produce a 530 bp amplicon of the ompAgene that is present only in rickettsiae of the spotted fever group. A total of 1,745 adult ticks were collected, including 1,673 specimens of Amblyomma sculptum, 63 of Amblyomma coelebs, five of Amblyomma naponenseand four of Amblyomma ovale. Thirteen ticks of the species A. ovale, A. coelebsand A. sculptumshowed structures compatible with Rickettsiainside the hemocytes; after DNA extraction, the presence of Rickettsiaspp. in a sample of A. ovalewas confirmed by PCR in both analyzed fragments. In the sequencing analysis, 100% identity for the Rickettsia parkeristrain Atlantic rainforest was obtained according to GenBank. The two environmental preservation areas showed A. sculptumas the predominant species, as well as the presence of marked seasonality for this species. This paper is the first report of the R. parkeristrain Atlantic rainforest in A. ovaleticks in the state of Mato Grosso do Sul, Brazil.

Identifying the tick species that successfully feed on humans would increase knowledge of the epidemiology of several tick-borne diseases. These species salivate into the host, increasing the risk of pathogen transmission. However, there is a lack of data in the literature regarding the ticks that prefer to feed on humans. Herein, we describe the successful feeding of Amblyomma coelebs Neumann nymphs on two of the authors after accidental tick bites occurred during field surveys in two preserved areas of Mato Grosso do Sul, Brazil. One of the host–parasite interactions was closely monitored, and the tick development, gross host skin alterations, and related sensations are presented.