ABSTRACT
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. All populations were highly resistant to cypermethrin, with resistance factors (RF) ranging from 89.4 to 1,020.6. Polymerase chain reaction (PCR) assays to detect the knockdown resistance (kdr) mutation also were performed in 16 samples. The kdr mutation was found in 75% of the tested populations, mostly with relatively low frequencies (<20%), and was absent in some highly resistant populations. Addition of TPP did not significantly reduce the LC50 in any population. However, PBO reduced LC50s above 40-fold in all tested populations, resulting in RFs ≤ 10 in most cases. Horn fly resistance to cypermethrin is widespread in the state, being primarily caused by an enhanced activity of P450 mono-oxygenases and secondarily by reduced target site sensitivity.
Subject(s)
Insecticides/pharmacology , Muscidae/drug effects , Pyrethrins/pharmacology , Animals , Brazil , Insecticide ResistanceABSTRACT
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. All populations were highly resistant to cypermethrin, with resistance factors (RF) ranging from 89.4 to 1,020.6. Polymerase chain reaction (PCR) assays to detect the knockdown resistance (kdr) mutation also were performed in 16 samples. The kdr mutation was found in 75% of the tested populations, mostly with relatively low frequencies (<20%), and was absent in some highly resistant populations. Addition of TPP did not significantly reduce the LC50 in any population. However, PBO reduced LC50s above 40-fold in all tested populations, resulting in RFs ≤ 10 in most cases. Horn fly resistance to cypermethrin is widespread in the state, being primarily caused by an enhanced activity of P450 mono-oxygenases and secondarily by reduced target site sensitivity.
Resistência da mosca-dos-chifres a inseticidas piretróides ocorre em todo o país, entretanto, o conhecimento sobre os mecanismos envolvidos é ainda incipiente. Este estudo objetivou identificar os mecanismos de resistência desta mosca à cipermetrina em Mato Grosso do Sul. Bioensaios utilizando papéis impregnados com cipermetrina, isoladamente ou sinergizada por butóxido de piperonila (PBO) ou trifenil fosfato (TPP), foram realizados de março∕2004 a junho∕2005 em 33 populações. Todas as populações apresentaram elevada resistência à cipermetrina, com fatores de resistência (FR) variando de 89,4 a 1.020,6. Ensaios de reação em cadeia da polimerase (PCR) visando a detecção de kdr ("knockdown resistance") foram realizados em 16 amostras. A mutação kdr foi detectada em 75% das populações, geralmente em baixas frequências (<20%) e ausente em algumas populações resistentes. A adição de TPP não reduziu significativamente a CL50 em nenhuma população. Entretanto, o PBO reduziu em mais de 40 vezes a CL50 de todas as populações testadas, resultando em FR ≤ 10 na maioria dos casos. Resistência da mosca-dos-chifres à cipermetrina encontra-se disseminada no estado, sendo causada primariamente por um aumento da atividade de P450 mono-oxigenases e secundariamente pela redução da sensibilidade do sítio de ação do inseticida.
Subject(s)
Animals , Insecticides/pharmacology , Muscidae/drug effects , Pyrethrins/pharmacology , Brazil , Insecticide ResistanceABSTRACT
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. After ten generations, using these methods combined, the final RR50 was 8.06. This work shows for the first time that it was possible to increase IVM resistance in R. microplus in laboratory conditions. The establishment of a drug resistant R. microplus strain is a fundamental first step for further research into the mechanisms of ivermectin-resistance in R. microplus and potentially methods to control this resistance.
Subject(s)
Drug Resistance , Insecticides , Ivermectin , Rhipicephalus/drug effects , Animals , Brazil , Cattle , Female , Larva/drug effects , Lethal Dose 50ABSTRACT
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. Seventy-five percent of the culture samples were positive and all samples amplified rickettsial gene fragments. To date, 46% of the samples have been sequenced.
Subject(s)
Rickettsia Infections/epidemiology , Rickettsia rickettsii/isolation & purification , Rickettsia/isolation & purification , Blood Coagulation , Brazil/epidemiology , DNA Primers , Humans , Polymerase Chain Reaction , Reproducibility of Results , Rickettsia/genetics , Rickettsia Infections/blood , Rickettsia rickettsii/genetics , Rocky Mountain Spotted Fever/blood , Rocky Mountain Spotted Fever/epidemiologyABSTRACT
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. The ticks collected were examinated for the presence of rickettsiae using polymerase chain reaction and the haemolymph test. Through analysis of the gene gltA nucleotide sequence, adults of Amblyomma cajennense and Amblyomma cooperi were found to be infected with the non pathogenic Rickettsia bellii. However, no rickettsiae of the Spotted Fever Group were detected. These results indicate that the role of capybaras as reservoirs of rickettsiae of the Spotted Fever Group is still uncertain and further studies are required.
Subject(s)
Disease Reservoirs/veterinary , Disease Vectors , Ixodidae/microbiology , Rickettsia/isolation & purification , Rodentia/parasitology , Animals , Brazil/epidemiology , Endemic Diseases , Female , Humans , Male , Polymerase Chain Reaction , Rickettsia/classification , Rickettsia/genetics , Rickettsia Infections/epidemiology , Rickettsia Infections/transmission , Urban PopulationABSTRACT
O Município de Campinas situa-se em região endêmica para febre maculosa brasileira do Estado de São Paulo, onde vários casos desta doenca vem ocorrendo. Capivaras têm sido associadas ao ciclo dessa riquetsiose por apresentarem sorologia positiva e serem hospedeiras de carrapatos Amblyomma spp principais vetores da doenca. Carrapatos foram coletados no parque urbano do Lago do Café, Campinas, SP, local associado a casos humanos suspeitos de febre maculosa brasileira, sobre a vegetacão e das capivaras ali presentes, e pesquisados quanto à presenca de riquétsias pela reacão em cadeia da polimerase e pelo teste de hemolinfa. Adultos de Amblyomma cajennense e Amblyomma cooperi albergavam Rickettsia bellii, não patogênica, identificada pela análise das seqüências de nucleotídeos do gene gltA, porém, não foram constatadas riquétsias do Grupo da Febre Maculosa. Estes resultados associados à ausência de um isolado de riquétsias do Grupo da Febre Maculosa de capivaras indicam que seu papel, enquanto reservatório, necessita de maior investigacão.
Subject(s)
Animals , Humans , Male , Female , Disease Reservoirs/veterinary , Disease Vectors , Ixodidae/microbiology , Rickettsia/isolation & purification , Rodentia/parasitology , Brazil/epidemiology , Endemic Diseases , Polymerase Chain Reaction , Rickettsia Infections/epidemiology , Rickettsia Infections/transmission , Rickettsia/classification , Rickettsia/genetics , Urban PopulationABSTRACT
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.
Subject(s)
Bacterial Outer Membrane Proteins/genetics , DNA, Bacterial/genetics , Rickettsia Infections/diagnosis , Rickettsia rickettsii/genetics , Animals , Base Sequence , Brazil , Child, Preschool , Chlorocebus aethiops , Electrophoresis, Agar Gel , Endemic Diseases , Humans , Male , Polymerase Chain Reaction , Rickettsia Infections/virology , Ticks/microbiology , Vero CellsABSTRACT
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.
Subject(s)
Animals , Child, Preschool , Humans , Male , Bacterial Outer Membrane Proteins/genetics , DNA, Bacterial/genetics , Rickettsia Infections/diagnosis , Rickettsia rickettsii/genetics , Base Sequence , Brazil , Chlorocebus aethiops , Electrophoresis, Agar Gel , Endemic Diseases , Polymerase Chain Reaction , Rickettsia Infections/virology , Ticks/microbiology , Vero CellsABSTRACT
Amblyomma dissimile is a common ectoparasite of cold blooded animals and is an accidental ectoparasite of some wild mammals. Details of the biology of specimens from the State of Amapá were studied in the laboratory in a humidity chamber at an average environmental temperature of 19.5 §C, using Bufo marinus as host for the time in Brazil. We also report the first record of this species in the State of Minas Gerais
Subject(s)
Animals , Male , Female , Acaridae/physiology , Bufo marinus/parasitology , Brazil , Host-Parasite InteractionsABSTRACT
Estudos morfológicos de 35 ascarideos, colhidos de abcesso fistulado do pescoço de um gato doméstico, permitiram diagnóstica-los como Lagochilascaris major Leiper, 1910. As medidas e número de escavaçöes presentes na superfície dos ovos se assemelharam aquelas verificadas para L. sprenti (BOWMAN et alii, 2, 1983 e para L. major (AMATO et alii, 1, 1982)
