LABORATORY STUDY ON THE DETECTION OF BLOOD MEAL FOR IMMATURE STAGES OF TICK Amblyomma cajennense (Acari: Ixodidae)

Author(s)

Nádia Pereira Martinez

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Saúde Pública (FSP/CIR)
• Defense date: 2013-10-25

Examining board members

Adriano Pinter dos Santos; Mauro Toledo Marrelli; Maria Halina Ogrzewalska

• Advisor: Adriano Pinter dos Santos

Abstract

The tick Amblyomma cajennense is the main vector of the bacterium Rickettsia rickettsii, the etiological agent of brazilian spotted fever (BSF). The subadult stages of this arthropod present a low specificity for hosts, which increases the chances of parasitism in humans. In the years of 2011 and 2012, the BSF epidemiological surveillance recorded 140 confirmed cases and 50 per cent case-letality rate, the highest incidence since the regulation of the compulsory notification in the State of São Paulo, in 2001. Furthermore, studies indicate an increase trend for geographical expansion and number of cases of the disease. In order to apply control measures for BSF, the determination of which is the vertebrate hosts for the immature stages of the tick is important to identify the sources of infection of bacteria. Among the scientific literature there was no studies on this scope for ticks of South America. In this study, it was standardized a approach for detection of feeding habits of A. cajennense. Briefly, blood samples were collected from the following animal species: chicken, capybara, quail, horse, guinea pig, rabbit, dog and a wild mouse. Then, DNA was extracted from these samples and afterwards tested for PCR amplification using three different pairs of primers for mammals, three for birds, and five for both groups of animals in addition to a specific designed primers for cricetidae rodents. The target gene 12S rDNA, cyt b and COI resulted in positive for detection of DNA fragments. PCR was tested thereafter on laboratory fed ticks. Adult A. cajennense ticks that were fed on rabbits as larvae and nymphs had the midguts extracted and processed for DNA isolation and underwent PCR amplification. It was possible to identify the host species on 66,7 per cent of tested ticks. The DNA sequencing and comparison of the consensus sequences of all the database sequences (GenBank) allowed the identification at the species level (rabbit), based on 98 per cent similarity. (AU)

• FAPESP's process: 11/05503-5 - Patronization of methods for feeding habits identification for nymphs of the tick Amblyomma cajennense, a tool in Brazilian Spotted Fever epidemiological studies
• Grantee: Nádia Pereira Martinez
• Support Opportunities: Scholarships in Brazil - Master