Susceptibility to insecticides and resistance mechanisms in three populations of Aedes aegypti from Peru.

BACKGROUND: Epidemics of dengue, chikungunya and Zika are a growing threat to areas where Aedes aegypti are present. The efficacy of chemical control of Ae. aegypti is threatened by the increasing frequency of insecticide resistance. The objective of this study was to determine the susceptibility status as well as the biochemical and molecular mechanisms underlying insecticide resistance in three populations of Ae. aegypti in high risk areas of dengue, chikungunya, and Zika in Peru. METHODS: Bioassays were conducted on adult Ae. aegypti to evaluate their susceptibility to insecticides used currently or historically for mosquito control in Peru, including six pyrethroids, three organophosphates and one organochlorine, in populations of Ae. aegypti from the districts of Chosica (Department of Lima), Punchana (Department of Loreto) and Piura (Department of Piura). Resistance mechanisms were determined by biochemical assays to assess activity levels of key detoxification enzyme groups (nonspecific esterases, multi-function oxidases, glutathione S-transferases and insensitive acetylcholinesterase). Real-time PCR assays were used to detect two kdr mutations (V1016I and F1534C) on the voltage-gated sodium channel gene. RESULTS: Resistance to DDT was detected in all three populations, and resistance to pyrethroids was detected in all populations except the population from Chosica, which still exhibited susceptibility to deltamethrin. Resistance to organophosphates was also detected, with the exception of populations from Punchana and Piura, which still demonstrated susceptibility to malathion. In general, no increase or alteration of activity of any enzyme group was detected. Both 1016I and 1534C alleles were detected in Punchana and Piura, while only the 1534C allele was detected in Chosica. CONCLUSIONS: The results suggest that resistance to multiple classes of insecticides exist in areas important to Ae. aegypti-borne disease transmission in Peru. The F1534C mutation was present in all 3 populations and the V1016I mutation was present in 2 populations. To our knowledge, this is the first report of the presence of 1016I and 1534C in Ae. aegypti in Peru. The absence of highly elevated enzymatic activity suggests that target site resistance is a key mechanism underlying insecticide resistance in these populations, although further research is needed to fully understand the role of metabolic resistance mechanisms in these populations.

The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae) group of ticks: phenotypic plasticity or incipient speciation?

BACKGROUND: The goal of this study was to reassess the taxonomic status of A. maculatum, A. triste and A. tigrinum by phylogenetic analysis of five molecular markers [four mitochondrial: 12S rDNA, 16S rDNA, the control region (DL) and cytochrome c oxidase 1 (cox1), and one nuclear: ribosomal intergenic transcribed spacer 2 (ITS2)]. In addition, the phenotypic diversity of adult ticks identified as A. maculatum and A. triste from geographically distinct populations was thoroughly re-examined. RESULTS: Microscopic examination identified four putative morphotypes distinguishable by disjunct geographical ranges, but very scant fixed characters. Analysis of the separated mitochondrial datasets mostly resulted in conflicting tree topologies. Nuclear gene sequences were almost identical throughout the geographical ranges of the two species, suggesting a very recent, almost explosive radiation of the terminal operational taxonomic units. Analysis of concatenated molecular datasets was more informative and indicated that, although genetically very close to the A. maculatum - A. triste lineage, A. tigrinum was a monophyletic separate entity. Within the A. maculatum - A. triste cluster, three main clades were supported. The two morphotypes, corresponding to the western North American and eastern North American populations, consistently grouped in a single monophyletic clade with many shared mitochondrial sequences among ticks of the two areas. Ticks from the two remaining morphotypes, south-eastern South America and Peruvian, corresponded to two distinct clades. CONCLUSIONS: Given the paucity of morphological characters, the minimal genetic distance separating morphotypes, and more importantly the fact that two morphotypes are genetically indistinguishable, our data suggest that A. maculatum and A. triste should be synonymized and that morphological differences merely reflect very recent local adaptation to distinct environments in taxa that might be undergoing the first steps of speciation but have yet to complete lineage sorting. Nonetheless, future investigations using more sensitive nuclear markers and/or crossbreeding experiments might reveal the occurrence of very rapid speciation events in this group of taxa. Tentative node dating revealed that the A. tigrinum and A. maculatum - A. triste clades split about 2 Mya, while the A. maculatum - A.triste cluster radiated no earlier than 700,000 years ago.

[Epidemiological and molecular profile of Rickettsiosis in peruvian border locations]. / Perfil epidemiológico y molecular de Rickettsiosis en localidades de frontera peruana.

OBJECTIVES.: To determine the circulation of Rickettsia in the years 2010 and 2011 in border locations in four regions ofPeru and their clinical epidemiological and molecular characteristics. MATERIALS AND METHODS.: A cross-sectional study was carried out in Tumbes, Tacna, Madre de Dios, and Loreto. Whole blood samples were obtained from participants for culture and indirect immunofluorescence (IIF) testing. The DNA taken from leukocytes and ectoparasite cultures was used, and those genes detected for Rickettsia that were successfully amplified were sequenced and analyzed. RESULTS.: A total of 33.8% of those surveyed carried Rickettsia antibodies (21.7% in Loreto, 33.0% in Madre de Dios, 48.2% in Tacna, and 33.3% in Tumbes). Seropositivity was confirmed with IIF in over 40% of isolates. Molecular tests showed the presence of Rickettsia felis in Ctenocephalides felis of dogs and cats in Tacna and a recently reported species for Latin America, Candidatus Rickettsia asemboensis, in fleas of cats and dogs in Loreto, Madre de Dios, and Tacna. Of the population studied, 81.4% reported a history of contact with ectoparasites, 22.6% were asymptomatic, and 27.8% lived in earthen-floored homes without water or drainage. CONCLUSIONS.: Serological and molecular evidence confirms the circulation of Rickettsia in the border locations studied, with predisposing epidemiological factors. Tests confirm the presence of two species, Rickettsia felis and Candidatus Rickettsia asemboensis, which represent a potential threat to the health of the inhabitants.

Perfil epidemiológico y molecular de Rickettsiosis en localidades de frontera peruana / Epidemiological and molecular profile of Rickettsiosis in peruvian border locations

RESUMEN Objetivos. Determinar circulación de rickettsias durante los años 2010 al 2011 en localidades fronterizas de cuatroregiones del Perú, y sus características clínicas epidemiológicas y moleculares. Materiales y métodos. Estudio transversal realizado en Tumbes, Tacna, Madre de Dios y Loreto. Se obtuvo datos clínicos epidemiológicos y muestras de sangre total para cultivo y para ensayo de inmunofluorescencia indirecta (IFI). Fue utilizado ADN extraído de cultivos de leucocitos y de ectoparásitos, aquellos genes específicos para rickettsias que amplificaron exitosamente fueron secuenciados y analizados. Resultados. El 33,8% de los encuestados portaba anticuerpos a rickettsias; en Loreto 21,7%, en Madre de Dios 33,0%, en Tacna 48,2% y en Tumbes 33,3%, encontrándose seropositividad en más del 40% de aislamientos confirmados por IFI. Las pruebas moleculares evidenciaron la presencia de Rickettsia felis en Ctenocephalides felis de perros y gatos de Tacna y una especie recientemente reportada para Latinoamérica: Candidatus Rickettsia asemboensis en pulgas Ctenocephalides felis de gatos y perros de Loreto y Madre de Dios. De la población estudiada, el 81,4% informó antecedentes de contacto con ectoparásitos, el 22,6% eran asintomáticos y el 27,8% habitaban viviendas sin agua ni desagüe, con piso de tierra. Conclusiones. Evidencias serológicas y moleculares confirman la circulación de rickettsias en las localidades fronterizas estudiadas, con predisponentes epidemiológicos, demostrándose presencia de dos especies: Rickettsia felis y Candidatus Rickettsia asemboensis, las que representarían una amenaza potencial para la salud de los pobladores.

ABSTRACT Objectives. To determine the circulation of Rickettsia in the years 2010 and 2011 in border locations in four regions ofPeru and their clinical epidemiological and molecular characteristics. Materials and Methods. A cross-sectional study was carried out in Tumbes, Tacna, Madre de Dios, and Loreto. Whole blood samples were obtained from participants for culture and indirect immunofluorescence (IIF) testing. The DNA taken from leukocytes and ectoparasite cultures was used, and those genes detected for Rickettsia that were successfully amplified were sequenced and analyzed. Results. A total of 33.8% of those surveyed carried Rickettsia antibodies (21.7% in Loreto, 33.0% in Madre de Dios, 48.2% in Tacna, and 33.3% in Tumbes). Seropositivity was confirmed with IIF in over 40% of isolates. Molecular tests showed the presence of Rickettsia felis in Ctenocephalides felis of dogs and cats in Tacna and a recently reported species for Latin America, Candidatus Rickettsia asemboensis, in fleas of cats and dogs in Loreto, Madre de Dios, and Tacna. Of the population studied, 81.4% reported a history of contact with ectoparasites, 22.6% were asymptomatic, and 27.8% lived in earthen-floored homes without water or drainage. Conclusions. Serological and molecular evidence confirms the circulation of Rickettsia in the border locations studied, with predisposing epidemiological factors. Tests confirm the presence of two species, Rickettsia felis and Candidatus Rickettsia asemboensis, which represent a potential threat to the health of the inhabitants.

Morphological and molecular analysis of Ornithonyssus spp. (Acari: Macronyssidae) from small terrestrial mammals in Brazil.

Based on chaetotaxy of the dorsal shield, the taxonomic status of many species of Ornithonyssus has been considered invalid, resulting in the synonymy of all Brazilian Ornithonyssus from small terrestrial wild mammals into one of the following four species: Ornithonyssus bacoti (Hirst, 1913), Ornithonyssus matogrosso (Fonseca, 1954), Ornithonyssus pereirai (Fonseca, 1935) or Ornithonyssus wernecki (Fonseca, 1935). Despite the revision of this genus in 1980, including all known species worldwide, the knowledge of Ornithonyssus in Brazil has not progressed for more than 40 years. Considering the potential importance of these haematophagous mites in transmitting rickettsial disease agents to animals and humans, we have revised Ornithonyssus species collected from small mammals in Brazil by means of morphological and molecular studies. Types and other material deposited in the Acari Collection of the Instituto Butantan (IBSP) were examined in addition to recently collected specimens. Morphological and genetic analysis of the 16S rDNA mitochondrial gene revealed that small terrestrial mammals in Brazil are parasitized by six species of Ornithonyssus mites: Ornithonyssus brasiliensis (Fonseca, 1939), O. matogrosso, O. monteiroi (Fonseca, 1941), O. pereirai, O. vitzthumi (Fonseca, 1941), and O. wernecki. An illustrated key to females of the valid Brazilian species of Ornithonyssus is included, based on optical and scanning electron microscopy.

Morphological and molecular analysis of Ornithonyssus spp. (Acari: Macronyssidae) from small terrestrialmammals in Brazil

Based on chaetotaxy of the dorsal shield, the taxonomic status of many speciesof Ornithonyssus has been considered invalid, resulting in the synonymy of all Brazilian Ornithonyssus from small terrestrial wild mammals into one of the following four species:Ornithonyssus bacoti (Hirst, 1913), Ornithonyssus matogrosso (Fonseca, 1954), Ornithonyssuspereirai (Fonseca, 1935) or Ornithonyssus wernecki (Fonseca, 1935). Despite therevision of this genus in 1980, including all known species worldwide, the knowledge of Ornithonyssus in Brazil has not progressed for more than 40 years. Considering the potential importance of these haematophagous mites in transmitting rickettsial diseaseagents to animals and humans, we have revised Ornithonyssus species collected from small mammals in Brazil by means of morphological and molecular studies. Types and other material deposited in the Acari Collection of the Instituto Butantan (IBSP) were examinedin addition to recently collected specimens. Morphological and genetic analysis of the 16S rDNA mitochondrial gene revealed that small terrestrial mammals in Brazil are parasitizedby six species of Ornithonyssus mites: Ornithonyssus brasiliensis (Fonseca, 1939), O. matogrosso, O. monteiroi (Fonseca, 1941), O. pereirai, O. vitzthumi (Fonseca, 1941), and O. wernecki. An illustrated key to females of the valid Brazilian species of Ornithonyssus is included, based on optical and scanning electron microscopy.

El zorro Andino, Pseudalopes culpaeus, un nuevo huésped para Corynosoma obtuscens (Acanthocephala) en el Perú / The Andean fox, Pseudalopes culpaeus, a new host for Corynosoma obtuscens (Acanthocephala) in Peru

Se describe la presencia de Corynosoma obtuscens Lincicome, 1943 (Acanthocephala, Polymorphidae) en el intestino delgado del zorro andino Pseudalopex culpaeus (Molina, 1782) procedente de San Juan de Marcona, Departamento de Ica, Perú. Esta es la segunda vez que se registra la infección natural de un mamífero terrestre por C. obtuscens en el Perú, por lo que se considera a P. culpaeus como huésped definitivo accidental; además se comenta la posibilidad de que éste acantocefalo infecte al hombre.

Corynosoma obtuscens Lincicome 1943 (Acanthocephala, Polymorphidae) is reported in the small intestine of Andean fox Pseudalopex culpaeus (Molina, 1782) from San Juan de Marcona, in the department of Ica, Peru. This is the second time that C. obtuscens is reported to infect terrestrial mammals in Peru supporting that P. culpaeus is a definitive accidental host of the parasite. Inaddition, the possibility that C. obtuscens infects humans is discussed.