Rickettsia communities and their relationship with tick species within and around the national park of Iguaçu, Brazil.

We report Rickettsia species from 2,334 ticks collected from environment (1,939 ticks) and animals (395 ticks) in the largest inland fragment of the Atlantic rainforest of southern Brazil and its fragments. Additionally, the DNA infection rates of Amblyomma ovale tick populations in the Neotropics with Rickettsia bellii and Rickettsia parkeri strain Atlantic rainforest were calculated using data from scientific publications, and their correlation was evaluated. From 11 tick species Rickettsia DNA was detected in seven (Amblyomma brasiliense, Amblyomma coelebs, Amblyomma incisum, Amblyomma longirostre, A. ovale, Haemaphysalis juxtakochi, Ixodes fuscipes) and was not detected in four species (Amblyomma dubitatum, Ixodes loricatus, Rhipicephalus microplus and Rhipicephalus sanguineus sensu lato). DNA of five Rickettsia species was detected (R. bellii, Rickettsia amblyommatis, Rickettsia rhipicephali, Rickettsia felis and Rickettsia sp. Aragaoi). To determine the prevalence of Rickettsia DNA positivity according to vector species, ticks were processed individually or in pools of 2-10 individuals (samples). The most prevalent Rickettsia species was R. bellii, found in 112 samples, followed by R. amblyommatis, R. rhipicephali, R. felis and Rickettsia sp. Aragaoi, found in 16, five, two and one sample, respectively. Rickettsia bellii DNA was found in five tick species with the highest infection rate in A. ovale and A. brasiliense. Absence of R. parkeri strain Atlantic rainforest in A. ovale ticks was an unexpected result. Furthermore, a negative correlation was identified between the infection rates (DNA) of R. bellii and/or R. parkeri strain Atlantic rainforest within A. ovale tick populations in the Neotropics. Putting together current knowledge, it can be proposed that, within natural settings, the diversity of rickettsiae and ticks creates a buffering effect on the overgrowth of rickettsiae and episodes of bacteremia in the hosts.

Ticks on humans in an Atlantic rainforest preserved ecosystem in Brazil: Species, life stages, attachment sites, and temporal pattern of infestation.

We herein describe exposure and tick attachment to researchers and field staff within the greatest preserved inland Atlantic rainforest, located in Brazil, over a non-consecutive period of five years. Overall, 433 ticks from five species were collected, Amblyomma coelebs (n = 281), Amblyomma brasiliense (n = 79), Amblyomma incisum (n = 43), Amblyomma ovale (n = 4), Haemaphysalis juxtakochi (n = 4). Clusters of larvae belonged to the genus Amblyomma (n = 21) and Haemaphysalis (n = 1). Both Haemaphysalis and Amblyomma species were observed crawling on humans but only ticks from the latter genus were found attached. Most recovered ticks (59%) were found attached and, whereas A. brasiliense was the main host-seeking tick species in the forest, A. coelebs nymphs were the ones that overwhelmingly attached to humans (70% of all attachments). At the same time only 0.4% of human bites were of A. ovale, the Rickettsia parkeri strain Atlantic rainforest vector tick in Brazil. Tick attachment sites were recorded for 132 ticks and lower/upper limbs and the trunk were more parasitized than the head/neck. Tick bites were recorded throughout the year; while larvae did not show an evident seasonal pattern, nymphs attached to humans mainly in autumn and winter and the few adult bites were recorded in spring. Our results highlighted A. coelebs nymphs as major human-biters and evidenced the necessity of studies that discern human tick bites that occur after exposure to host-seeking ticks from those that occur after tick displacement from hosts that carry ticks to human dwellings.

Community structure and tree diversity in a subtropical forest in southern Brazil / Estrutura da comunidade e diversidade de espécies arbóreas em uma floresta subtropical no sul do Brasil

Abstract: Local and regional environmental variations lead to different species composition, creating transitional areas. An example is the Araucaria and Seasonal forest in southern Brazil. Our objectives were (1) to describe the tree community structure and composition of a subtropical forest in southern Brazil and (2) to compare the floristic relationships between two forest typologies (Araucaria and Seasonal forest) in order to characterize the study area and the distribution patterns of tree species. We conducted a survey at Chapecó National Forest (in southern Brazil) in an area of 1.2 ha, where all individuals ≥ 30 cm of circumference at breast height were sampled. Community structure was described using the traditional phytosociological parameters. The floristic relationships were obtained by comparing our results with compiled data from other scientific papers through cluster analyses using an unweighted average linkage method, based on Jaccard similarity coefficient. We sampled 809 individuals belonging to 61 species and 28 families. The richest family was Fabaceae and Coussarea contracta (Walp.) Müll.Arg. was the most abundant species. Taxonomic diversity was 3.06 and the evenness was 0.74. The floristic similarity revealed that species composition of our study area is more similar to Seasonal forest. Species composition is related to environmental factors such as great thermal amplitude and seasonality. This subtropical forest is well structured, highly diverse and extremely important for the local and regional biodiversity conservation.

Resumo: Variações ambientais locais e regionais levam à composição de espécies diferentes e áreas de transições. Um exemplo é a floresta com araucária e a floresta estacional no sul do Brasil. Nossos objetivos foram (1) descrever a composição e estrutura da comunidade arbórea de uma floresta subtropical no sul do Brasil e (2) comparar as relações florísticas entre duas tipologias florestais (Floresta com Araucária e Floresta Estacional) a fim de caracterizar a área de estudo e o padrão de distribuição de espécies arbóreas. Nós realizamos uma pesquisa na Floresta Nacional de Chapecó (no sul do Brasil) em uma área de 1.2 hectares, onde todos os indivíduos com circunferência à altura do peito ≥ 30 cm foram amostrados. A estrutura da comunidade foi descrita utilizando os parâmetros fitossociológicos tradicionais. Obtivemos as relações florísticas através da comparação dos nossos resultados com dados compilados de outros trabalhos científicos, através de análises de agrupamento (método de ligação de distância média não ponderada, UPGMA, baseado no coeficiente de similaridade de Jaccard). Foram amostrados 809 indivíduos pertencentes a 61 espécies e 28 famílias. A família mais rica foi Fabaceae e Coussarea contracta (Walp.) Müll.Arg. a espécie mais abundante. A diversidade taxonômica foi de 3.06 e a equabilidade foi de 0.74. A similaridade florística revelou que a composição de espécies da nossa área de estudo é mais similar a da floresta estacional. A composição de espécies está relacionada a fatores ambientais como a amplitude térmica e sazonalidade. Esta floresta subtropical é bem estruturada, altamente diversa e muito importante para a conservação da biodiversidade local e regional.