Abstract
This study was performed in Maranhão state, a transition area two Brazilian biomes, Amazon and Cerrado. During 2011–2013, 1,560 domestic dogs were sampled for collection of serum blood samples and ticks in eight counties (3 within the Amazon and 5 within the Cerrado). A total of 959 ticks were collected on 150 dogs (9.6%). Rhipicephalus sanguineus sensu lato (s.l.) was the most abundant tick (68% of all collected specimens), followed by Amblyomma cajennense sensu lato (s.l.) (12.9%), Amblyomma parvum (9.2%), and Amblyomma ovale (5.2%). Other less abundant species (<1%) were Amblyomma oblongoguttatum, Rhipicephalus microplus, Haemaphysalis juxtakochi, and Amblyomma rotundatum. Females of A. cajennense s.l. ticks were morphologically identified as A. cajennense sensu stricto (s.s.) or A. sculptum. Molecular analyses of 779 canine ticks revealed three Rickettsia species: Rickettsia amblyommatis in 1% (1/100) A. cajennense s.l., ‘Candidatus Rickettsia andeanae’ in 20.7% (12/58) A. parvum, Rickettsia bellii in 6.8% (3/44) A. ovale and 100% (1/1) A. rotundatum ticks. An additional collection of A. sculptum from horses in a Cerrado area, and A. cajennense s.s. from pigs in an Amazon area revealed R. amblyommatis infecting only the A. cajennense s.s. ticks. Serological analysis of the 1,560 canine blood samples revealed 12.6% canine seroreactivity to Rickettsia spp., with the highest specific seroreactivity rate (10.2%) for R. amblyommatis. Endpoint titers to R. amblyommatis were significantly higher than those for the other Rickettsia antigens, suggesting that most of the seroreactive dogs were exposed to R. amblyommatis-infected ticks. Highest canine seroreactivity rates per locality (13.1–30.8%) were found in Amazon biome, where A. cajennense s.s. predominated. Lowest seroreactivity rates (1.9–6.5%) were found in Cerrado localities that were further from the Amazon, where A. sculptum predominated. Multivariate analyses revealed that canine seroreactivity to Rickettsia spp. or R. amblyommatis was statistically associated with rural dogs, exposed to Amblyomma ticks.
Highlights
Amazon and Cerrado are the two largest biomes representing the greatest biodiversity of Brazil [1]
4 canine independent variables showed statistical association (P
This number excludes A. rotundatum because the collected specimen was not attached to dog, and includes two species of A. cajennense s.l. (A. cajennense s.s. and A. sculptum)
Summary
Amazon and Cerrado are the two largest biomes representing the greatest biodiversity of Brazil [1]. A few studies have reported the diversity of ticks infesting domestic dogs in areas within the Amazon [2,3,4] and Cerrado [5,6,7]. Some transition areas were found with the two tick species in sympatry One of these transition areas is the state of Maranhão, composed by the Amazon biome in the western part (where A. cajennense s.s. predominates), and by the Cerrado biome in the eastern and southern parts Considering that the domestic dog is an important sentinel for tick-borne spotted fever [13,22,23], we investigated ticks infesting dogs and the rickettsial infection in ticks, and canine exposure to Rickettsia spp. in the state of Maranhão, where A. sculptum and A. cajennense s.s. have been reported to occur in sympatry in many areas
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