Mechanisms of pyrethroid resistance in Haematobia irritans (Muscidae) from Mato Grosso do Sul state, Brazil.

Horn fly resistance to pyrethroid insecticides occurs throughout Brazil, but knowledge about the involved mechanisms is still in an incipient stage. This survey was aimed to identify the mechanisms of horn fly resistance to cypermethrin in Mato Grosso do Sul state, Brazil. Impregnated filter paper bioassays using cypermethrin, synergized or not with piperonyl butoxide (PBO) and triphenyl phosphate (TPP), were conducted from March 2004 to June 2005 in horn fly populations (n = 33) from all over the state.

Selection of an ivermectin-resistant strain of Rhipicephalus microplus (Acari: Ixodidae) in Brazil.

Resistance to ivermectin (IVM) in field populations of Rhipicephalus microplus of Brazil has been observed since 2001. In this work, four selection methods (infestations with: (1) IVM-treated larvae; (2) larvae from IVM-treated adult female ticks; (3) larvae from IVM-treated adult female ticks on an IVM-treated host; and (4) larvae obtained from IVM-treated females that produced eggs with a high eclosion rate) were used on a field population with an initial ivermectin (IVM) resistance ratio at LC50 (RR50) of 1.37 with the objective to obtain experimentally a highly-resistant strain.

Detection of Rickettsia rickettsii and Rickettsia sp. in blood clots in 24 patients from different municipalities of the State of Sao Paulo, Brazil.

The authors detected Rickettsia genus organisms using shell vial and polymerase chain reaction (PCR)/sequencing analysis in blood clots in patients suspected of having Brazilian spotted fever (BSF). DNA was detected using PCR with three sets of primers to access the gltA, ompA, and ompB genes. Sequence analysis was carried out using an automatic sequencer with Bioedit software.

[Rickettsiae detection in Amblyomma ticks (Acari: Ixodidae) collected in the urban area of Campinas City, SP].

The city of Campinas is located in an endemic area for Brazilian spotted fever in São Paulo State, where several cases have recently occurred. Capybaras have been associated with the cycle of this disease, for they present positive serology and serve as host for ticks of the genus Amblyomma, the main vectors of Brazilian spotted fever. Ticks were collected both from Capybaras and from the vegetation in the city park Lago do Café, located in the urban area of Campinas City, SP, a site associated with suspected human cases of Brazilian spotted fever.

Detection of Brazilian spotted fever infection by polymerase chain reaction in a patient from the state of São Paulo.

Brazilian spotted fever (BSF) cases have been increasing in the state of São Paulo but no genomic information about local rickettsia isolated from humans has been well documented. We recovered spotted-fever group rickettsiae from a sample of patient blood cultured in Vero cells using the shell vial technique. Rickettsial DNA fragments (gltA, ompA, and, ompB genes) were detected, and analysis of the ompB gene base sequences showed identity with the Rickettsia rickettsii ompB sequence available in the GenBank.