Mário Antônio Navarro-Silva

Susceptibilidade de Aedes aegypti aos inseticidas temephos e cipermetrina, Brasil

Bioassays were performed in order to detect the susceptibility of Aedes aegypti to the chemical insecticides temephos and cypermethrin. The results showed that this species is susceptible to temephos and presents resistance to cypermethrin.

Development, longevity, gonotrophic cycle and oviposition of Aedes albopictus Skuse (Diptera: Culicidae) under cyclic temperatures

Os efeitos de temperaturas ciclicas no desenvolvimento, longevidade, ciclo gonadotrofico e numero de ovos postos de Aedes albopictus Skuse foram analisados por meio de experimentos laboratoriais. Os experimentos foram conduzidos com mosquitos oriundos de Registro, SP e mantidos em insetario por dois anos. O desenvolvimento do inseto foi acompanhado desde o ovo ate a emergencia do adulto, a 25/18oC e 27/20oC e o adulto a 27/20oC, ambos associados com fotoperiodo de 12h. Os ovos receberam dois tratamentos: (A) manutencao do volume da agua; (B) troca periodica e completa da agua. A alimentacao sanguinea era oferecida diariamente aos mosquitos com interrupcao quando o repasto era realizado, e retomada apos a primeira oviposicao. O desenvolvimento dos imaturos foi significativamente diferente sob os diferentes regimes de temperatura (P < 0,05), e a velocidade de desenvolvimento foi afetada positivamente pelo aumento da temperatura. A combinacao do regime de temperaturas mais altas com a troca periodica e completa da agua permitiu maior viabilidade dos ovos e encurtou o periodo de incubacao. A longevidade dos adultos nao foi diferente entre machos e femeas e a mortalidade foi regular ao passar do tempo. A comparacao da longevidade do mosquito sob temperaturas constantes e ciclicas sugere que a menor temperatura do regime ciclico seja um fator limitante para a sobrevivencia do mosquito. Esse fato pode ser um importante limitador da distribuicao de A. albopictus por sugerir que o mosquito esta restrito a ocupar areas com temperaturas minimas nao muito inferiores a 20oC.

Influência da temperatura sobre a longevidade, fecundidade e atividade hematofágica de Aedes (Stegomyia) albopictus Skuse, 1894 (Diptera, Culicidae) sob condições de laboratório

Influence of temperature on longevity, fecundity, and haematophagic activity of Aedes (Stegomyia) albopictus Skuse, 1894 (Diptera, Culicidae) under laboratory condition. Based on adults of Aedes albopictus maintained under four constant temperatures, 15oC, 20oC, 25oC and 30oC, longevity of males and females, fecundity, eggs viability, number of days from emergence to the first bloodsucking, and duration of the preoviposition period were observed. The average of the longevity for female was 19.45, 59.35, 61.55 and 42.72 days, under 15oC, 20oC, 25oC and 30oC, respectively. The greatest average number of bloodsucking per female was 8.32, under 25oC. The average number of eggs per female was 1.00, 73.91, 269.87 and 183.69, and the greatest rates of viable eggs per female was 25oC and 30oC. The haematophagic activities and the oviposition were significantly influenced by temperature.

Abundância e Agregação de Ovos de Aedes aegypti L. e Aedes albopictus (Skuse) (Diptera: Culicidae) no Norte e Noroeste do Paraná

The abundance and aggregation of eggs of Aedes aegypti L. and Aedes albopictus Skuse was evaluated in the municipalities of Cambe, Ibipora, Jacarezinho, Maringa and Paranavai, in the State of Parana, Brazil by means of oviposition traps. Of the 225 installed traps, 100 were registered as positive for eggs; 4140 eggs were collected, thus demonstrating an highly aggregate distribution. Both species were registered in Cambe, Jacarezinho, Maringa and Paranavai. Ae. albopictus was generally less abundant and was not present in Ibipora nor in the oviposition traps of a second collection of Maringa. The relation between sexes for Ae. aegypti was approximately 1:1. In the comparison of the number of adults collected between the two species, a negative correlation was obtained in the samples of Maringa and Cambe, what was attributed the seasonality of these populations. The coexistence of these species indicates that both are under pressure by the control programs, therefore specific evaluations are necessary.

Low malathion concentrations influence metabolism in Chironomus sancticaroli (Diptera, Chironomidae) in acute and chronic toxicity tests

Low malathion concentrations influence metabolism in Chironomus sancticaroli (Diptera, Chironomidae) in acute and chronic toxicity tests. Organophosphate compounds are used in agro-systems, and in programs to control pathogen vectors. Because they are continuously applied, organophosphates often reach water sources and may have an impact on aquatic life. The effects of acute and chronic exposure to the organophosphate insecticide malathion on the midge Chironomus sancticaroli are evaluated. To that end, three biochemical biomarkers, acetylcholinesterase (AChE), alpha (EST-α) and beta (EST-β) esterase were used. Acute bioassays with five concentrations of malathion, and chronic bioassays with two concentrations of malathion were carried out. In the acute exposure test, AChE, EST-α and EST-β activities declined by 66, 40 and 37%, respectively, at 0.251 µg L-1 and more than 80% at 1.37, 1.96 and 2.51 µg L-1. In chronic exposure tests, AChE and EST-α activities declined by 28 and 15% at 0.251 µg L-1. Results of the present study show that low concentrations of malathion can influence larval metabolism, indicating high toxicity for Chironomus sancticaroli and environmental risk associated with the use of organophosphates.

Paridade de Anopheles cruzii em Floresta Ombrófila Densa no Sul do Brasil

OBJECTIVE To determine the parity and ovarian development of Anopheles cruzii species during the seasons. METHODS Collections were carried out fortnightly in the morning in the Palmito State Park in the municipality of Paranaguá, Southern Brazil, between April 2004 and April 2005. Adult mosquitoes were captured using human landing rate. Dissections were performed using Detinovas and Polovodovas methods and follicular development was assessed following Christophers and Mers criteria. RESULTS A total of 208 specimens of Anopheles cruzii were dissected. Most females dissected were nulliparous in the seasons; 14.4% of them were found to be nulliparous above Christophers and Mers stage II, which shows previous blood meal prior to the first oviposition. It was observed that Anopheles cruzii populations comprised young mosquitoes, probably due to high mortality among parous females. CONCLUSIONS The likely gonotrophic discordance is epidemiologically relevant because female mosquitoes can search for more than one host to complete the maturation of their eggs.

Genotoxic effect of Phenanthrene on Chironomus sancticaroli (Diptera: Chironomidae)

Phenanthrene, a Polycyclic Aromatic Hydrocarbon, remains adsorbed to sedimentary particles in aquatic environments. It affects mainly benthic organisms, and is considered potentially genotoxic. In ecotoxicology, species of Chironomus Meigen, 1803 are widely known as bioindicators of the effects of chemicals on aquatic organisms. This study investigates the effects of phenanthrene on the size of the head capsule of Chironomus sancticaroli Strixino & Strixino, 1981 larvae after chronic (eight days) exposure, and DNA damage after acute (96 hours) and chronic exposure (eight days), under laboratory conditions. DNA damage, evaluated using the alkaline comet assay, detected effects for both exposure periods, indicating that phenanthrene is toxic for C. sancticaroli. For the acute exposure, we analyzed five concentrations of phenanthrene, between 0.16 mg.l-1 and 1.60 mg.l-1, detecting significant differences (Kruskall-Wallis test with p < 0.05) in the degree of DNA damage in all groups. These effects were not dose-dependent. For the chronic exposure, two concentrations (0.16 mg.l-1, 0.83 mg.l-1) were analyzed, and DNA damage was observed in both. Again, the effects were not dose-dependent. This indicates that phenanthrene is genotoxic to larvae of C. sancticaroli even at low concentrations. The size of the head capsule was evaluated after chronic exposure to concentrations of 0.16 mg.l-1 and 0.83 mg.l-1. Significant differences (ANOVA test with p < 0.05) were detected in the two concentrations, and a reduction in the size of the larval head capsule was observed. This suggests that phenanthrene causes delay in larval development. These results indicate that phenanthrene affects the development of and causes DNA damage in C. sancticaroli larvae. Therefore, we suggest that C. sancticaroli can be used as a biological indicator for environmental contamination with phenanthrene.

Preferência por hospedeiro e estratificação de Culicidae (Diptera) em área de remanescente florestal do Parque Regional do Iguaçu, Curitiba, Paraná, Brasil

Parks and plazas (green areas or vegetation islands) within urban areas can provide conditions for the development of populations of mosquitoes, many species of which are very adaptable to a variety of environments. The species of mosquitoes in the family Culicidae with animal hosts, in a vegetation island within an urban area, in Curitiba, in the state of Parana, in southern Brazil was investigated. To examine whether these green areas contribute to urban populations, mosquitoes were collected five times each season (spring, summer and fall), from September 2000 to July 2001. CDC-M traps were set at two heights (1.5 m and 6 m). A mammal (quinea pig, Cavia porcellus Linnaeus, 1758, Rodentia, Cavidae) and bird (Nothura maculosa (Temminck, 1815), Tinamiformes, Tinamidae) were used as bait. Traps were active from 16:00 to 20:00 h, with samples taken every 30 minutes. A total of 1,415 individual mosquitoes were collected, in 9 genera and 11 species, with 44% of the individuals taken in Spring samples, 40% in Summer and 16% in Fall samples. The 1.5 m traps with mammal bait captured the most mosquitoes (41%), with the 6m trap with bird bait being second (30%), followed by 1.5 m and bird bait (19%) and 6m and mammal bait (10%). Mansonia (Mansonia) fonsecai (Pinto, 1932) and Mansonia (Mansonia) pessoai (Barreto e Coutinho, 1944) was the most common species found with both baits. Other species captured were: Mansonia (Mansonia) wilsoni (Barreto & Coutinho, 1944); Mansonia (Mansonia) titillans (Walker, 1848); Culex (Culex) acharistus Root, 1927; Culex (Culex) sp.; Wyomyia (Phoniomyia) quasilongirostris Theobald, 1907; Ochlerotatus (Ochlerotatus) scapularis (Rondani, 1848); Psorophora (Janthinosoma) ferox (Humboldt, 1819); Culex (Melanoconion) sp.; Coquillettidia (Rhynchotaenia) venezuelensis (Theobald, 1912); Aedeomyia (Aedeomyia) squamipennis (Lynch Arribalzaga, 1878); Ochlerotatus (Ochlerotatus) serratus (Theobald, 1901); Limatus durhami Theobald, 1901 and Aedes (Stegomyia) albopictus (Skuse, 1894). This last species has a great epidemiological importance. This study shows that green areas (vegetation islands) within urban centers can be an important source of potentially epidemiological mosquitoes.

Insecticide resistance and genetic variability in natural populations of Aedes (Stegomyia) aegypti (Diptera: Culicidae) from Colombia

Mosquito control prevails as the most efficient method to protect humans from the dengue virus, despite recent efforts to find a vaccine for this disease. We evaluated insecticide resistance and genetic variability in natural populations of Aedes aegypti (Linnaeus, 1762) from Colombia. This is the first Colombian study examining kdr mutations and population structure. Bioassays with larvae of three mosquito populations (Armenia, Calarca and Montenegro) were performed according to the World Health Organization (WHO) guidelines, using Temephos. For the analysis of the Val1016Ile mutation and genetic diversity, we sampled recently-emerged adults from four mosquito populations (Armenia, Calarca, Montenegro and Barcelona). Following the WHO protocol, bioassays implemented with larvae showed resistance to Temephos in mosquito populations from Armenia (77% ± 2) and Calarca (62% ± 14), and an incipient altered susceptibility at Montenegro (88% ± 8). The RR95 of mosquito populations ranged from 3.7 (Montenegro) to 6.0 (Calarca). The Val1016Ile mutation analysis of 107 genotyped samples indicates that 94% of the specimens were homozygous for the wild allele (1016Val) and 6% were heterozygous (Val1016Ile). The 1016Ile allele was not found in Barcelona. Genetic variability analysis found three mitochondrial lineages with low genetic diversity and gene flow. In comparison with haplotypes from the American continent, those from this study suggest connections with Mexican and North American populations. These results confirm that a continuous monitoring and managing program of A. aegypti resistance in the state of Quindio is required.

Dynamics of the control of Aedes (Stegomyia) aegypti Linnaeus (Diptera, Culicidae) by Bacillus thuringiensis var israelensis, related with temperature, density and concentration of insecticide

The dynamics of the control of Aedes (Stegomyia) aegypti Linnaeus, (Diptera, Culicidae) by Bacillus thuringiensis var israelensis has been related with the temperature, density and concentration of the insecticide. A mathematical model for biological control of Aedes aegypti with Bacillus thuringiensis var israelensis (Bti) was constructed by using data from the literature regarding the biology of the vector. The life cycle was described by differential equations. Lethal concentrations (LC50 and LC95) of Bti were determined in the laboratory under different experimental conditions. Temperature, colony, larvae density and bioinsecticide concentration presented marked differences in the analysis of the whole set of variables; although when analyzed individually, only the temperature and concentration showed changes. The simulations indicated an inverse relationship between temperature and mosquito population, nonetheless, faster growth of populations is reached at higher temperatures. As conclusion, the model suggests the use of integrated control strategies for immature and adult mosquitoes in order to achieve a reduction of Aedes aegypti.