Activation of the ambusher tick Rhipicephalus microplus (Acari: Ixodidae) exposed to different stimuli.

The present study aimed to evaluate the behaviour of larvae of Rhipicephalus microplus exposed to different stimuli. A Y-olfactometer was positioned vertically and R. microplus larvae were exposed to environmental air, CO2 alone, N,N-diethyl-3-methylbenzamide (DEET) alone, and CO2 combined with the repellents DEET and (E)-2-octenal. Tests were also conducted with the olfactometer positioned horizontally; in this case, however, only CO2 was tested. In all tests conducted with the Y-olfactometer positioned vertically, CO2 activated R. microplus larvae even in the presence of DEET and (E)-2-octenal, although activation was lower when these repellents were used. In the absence of CO2 , larval behaviour against DEET was similar to that of the larvae in the control group. In the tests performed with the olfactometer positioned horizontally, the larvae had no significant response to the presence of CO2 . The larvae were not attracted to or repelled by any compound tested in either the vertical or horizontal position of the olfactometer. The lack of horizontal displacement, attraction or repellence may have been a result of the ambush behaviour of this tick species. However, when larvae were exposed to stimuli and the olfactometer was positioned vertically, the interference of attractant and repellent stimuli in larval behaviour was assessed.

Assessment of the repellent effect of Lippia alba essential oil and major monoterpenes on the cattle tick Rhipicephalus microplus.

The control of Rhipicephalus microplus (Ixodida: Ixodidae) is achieved using synthetic acaricides. However, resistant tick populations are widespread around the world. Plant essential oils can act as repellents, keeping ticks away from hosts and decreasing the selection pressure on synthetic acaricides. The aim of this study was to evaluate the in vitro repellent effect of Lippia alba essential oil on R. microplus larvae. Leaves from two L. alba genotypes maintained under the same agronomic and environmental conditions were collected. Essential oil was extracted by hydrodistillation and analysed by gas chromatography-mass spectrometry (GC-MS). The major monoterpenes detected in the chemical analysis were commercially acquired and tested. For the repellency test, a glass rod was vertically fixed to measure active climbing of approximately 30 R. microplus larvae aged 14-21 days in response to essential oils and monoterpenes. Repellency was evaluated at 1 h, 3 h and 5 h after treatment. Variation in repellent action was detected between the genotypes. The major monoterpenes identified in the essential oils (limonene and carvone) showed low repellent effects in comparison with intact essential oils. Thus, the present results showed that L. alba essential oil contains bioactive compounds with great repellent activity against ticks that varies according to the plant genotype.

Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) como novo hospedeiro de Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) / Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) as new host of Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae)

This study reports the occurrence of Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) as parasitoid of Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) in bovine feces obtained in Goiânia, Goiás state, Brazil. Bovine manure samples, collected at two weeks intervals, were taken to the laboratory and the pupae were extracted by water flotation. Each pupa was placed in capsules of gelatin until the emergence of dipterous or their parasitoids. The parasitism percentage was of 2.4%. This paper reports the first occurrence of N. vitripennis as parasitoid of C. pararescita worldwide.(AU)

Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) como novo hospedeiro de Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) / Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) as new host of Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae)

This study reports the occurrence of Nasonia vitripennis (Walker) (Hymenoptera: Pteromalidae) as parasitoid of Cyrtoneurina pararescita (Diptera: Muscidae) (Couri, 1995) in bovine feces obtained in Goiânia, Goiás state, Brazil. Bovine manure samples, collected at two weeks intervals, were taken to the laboratory and the pupae were extracted by water flotation. Each pupa was placed in capsules of gelatin until the emergence of dipterous or their parasitoids. The parasitism percentage was of 2.4%. This paper reports the first occurrence of N. vitripennis as parasitoid of C. pararescita worldwide.

Populational dynamics of Stomoxys calcitrans (Linneaus) (Diptera: Muscidae) in three biocenosis, Minas Gerais, Brazil.

Populational flux of the adult phase of Stomoxys calcitrans was observed in the municipal district of Pedro Leopoldo, Minas Gerais, Brazil. Three biocenoses were selected for the study: stable agrobiocenosis, pastural agrobiocenosis and eubiocenosis. The occurrence and the populational flux of the insects, using the Magoon trap for their capture, were established. For each trap located in different biocenoses, a crossbred calf (Bos taurusxBos indicus) approximately 6-month-old was used as "live bait," exposed weekly for 48h in the traps. Of the three agrobiocenoses studied, the stable agrobiocenosis contributed the greatest number of specimens of. S. calcitrans captured, corresponding to 96.9% of the total flies of this species collected. S. calcitrans shows seasonal behavior for approximately 6 months (spring and summer being the rainiest months of the year). The population peaked during the months of November and December. During the months of July and August, there was no capture of flies.

Seasonal dynamics of the Cayenne tick, Amblyomma cajennense on horses in Brazil.

The population dynamics of all stages of the Cayenne tick, Amblyomma cajennense (Fabricius) (Acari: Ixodidae) on horses was evaluated over a period of 2 years in the district of Pedro Leopoldo, State of Minas Gerais, Brazil. Every 14 days, the left side of 20 horses was brushed for collection of immature stages; counts of adults were also undertaken. Infestation by larvae was detected from April to August, whereas nymphs were observed from June to October. Infestation by adults was detected throughout the year, and the highest population density occurred from September to March. The number of males was always higher than the number of females, but with considerable reduction in the male : female ratio between April and July. It was observed that 25% of the horses carried 41% of the infesting ticks, and 20% carried only 10% of the ticks during the entire period of the study.

In vitro efficacy of extracts of Melia azedarach against the tick Boophilus microplus.

The efficacy of ripe fruit extracts of Melia azedarach L. (Rutales: Meliaceae) was evaluated against the tick, Boophilus microplus (Canestrini) (Acari: Ixodidae). Ripe fruits of M. azedarach dried and powdered were extracted by Soxhlet apparatus successively using hexane, CHCl3 and 96% aqueous ethanol. Larvae and engorged females were immersed in decreasing concentrations from 0.25% to 0.015% of each extract. The mortality of larvae was evaluated 24, 72 and 168 h after treatment. The effectiveness of treatment against engorged females was assessed by measuring egg production. All tested extracts caused mortality of B. microplus larvae, with higher mortality rates observed in CHCl3 (100%) and hexanic extract (98%) than in ethanolic extract (50%) 168 h after treatment. The mortality was dependent on concentration and on time after treatment. Similarly hexanic and CHCl3 extracts showed higher effectiveness (varying from 14% to 100%) against B. microplus engorged females than ethanolic extract (varying from 0% to 46%). Melia azedarach extracts did not kill the adult females, but inhibited partially or totally egg production and embryogenesis. These results show that the less polar the extract of M. azedarach ripe fruits the more its effectiveness against larvae and engorged females of B. microplus. This plant may therefore be useful in the control of resistant B. microplus populations.

Horse resistance to natural infestations of Anocentor nitens and Amblyomma cajennense (Acari: Ixodidae).

The objective of this study was to investigate some aspects of horse resistance to natural infestations of Anocentor nitens and Amblyomma cajennense over a 2-year period. Free-living stages of A. nitens were used to evaluate the influence of season of the year on horse resistance. Every 2 weeks, 10 selected engorged females, weighing 150-329 mg, were removed from naturally infested horses and were individually placed into glass tubes closed with a cotton stopper, and maintained in an incubator. The biological parameters evaluated varied according to the season of the year, i.e., reproductive efficiency, maximum larval survival (MLS) and egg-hatching rates were significantly lower in spring/summer than in fall/winter. At 14-day intervals, females of A. nitens and A. cajennense were counted on each side of the body of five mares. A comparison between the animal with the lowest infestation and the animal with the highest infestation showed greater differences in animals infested with A. nitens than those infested with A. cajennense. Ten animals were found to carry 64.9% of the total parasite burden of A. cajennense and 88.6% of the highest infestations of A. nitens females. A seasonal variation on intensity of horse resistance to A. nitens was observed during the study. However, this was not observed for A. cajennense. Cross-resistance was observed in animals with the highest total number of A. cajennense and the highest number of A. cajennense adults (r=0.817), larvae (r=0.756), and A. nitens females (r=0.799). These results led to the conclusion that changes in horse resistance to A. nitens occur seasonally. As far as the total population of A. cajennense and the female stage of A. nitens are concerned, horses develop cross-resistance.

In vitro evaluation of the effects of some acaricides on life stages of Rhipicephalus sanguineus (Acar: Ixodidae)

The action of five acaricides was evaluated on eggs, larvae, nymphs and adults of the ixodid tick Rhipicephalus sanguineus. The acaricides tested were: high cis-cypermethrin (0.01 per cent) + DDVP (0.11 per cent), coumaphos (0.05 per cent), deltamethrin (0.0025 per cent) and cypermethrin (0.015 per cent). Eggs treated with high cis-cypermethrin and cypermethrin showed eclosion inhibitions of 72.1 per cent and 67.3 per cent, respectively, whereas coumaphos was much less effective (only 11.7 per cent). Except for coumaphos, which resulted in 63.3 per cent and 80.0 per cent mortality of nymphs and unfed females, respectively, all compounds tested killed 100 por cento of all tick stages to which they were exposed

In vitro evaluation of the effects of some acaricides on life stages of Rhipicephalus sanguineus (Acari: Ixodidae)

The action of five acaricides was evaluated on eggs, larvae, nymphs and adults of the ixodid tick Rhipicephalus sanguineus. The acaricides tested were: high cis-cypermethrin (0.01%) + DDVP (0.11%), coumaphos (0.05%), deltamethrin (0.0025%), amitraz (0.025%) and cypermethrin (0.015%). Eggs treated with high cis-cypermethrin and cypermethrin showed eclosion inhibitions of 72.1% and 67.3%, respectively, whereas coumaphos was much less effective (only 11.7%). Except for coumaphos, which resulted in 63.3% and 80.0% mortality of nymphs and unfed females, respectively, all compounds tested killed 100% of all tick stages to which they were exposed.

Avaliou-se a ação de cinco acaricidas em ovos, larvas, ninfas e adultos do carrapato Rhipicephalus sanguineus. Os produtos testados foram: cipermetrina high cis (0.01%) + DDVP (0.11%), coumaphos (0.05%), deltametrina (0.0025%), amitraz (0.025%) e cipermetrina (0.015%). Os ovos tratados com cipermetrina high cis e cipermetrina mostraram inibição de eclosão de 72,1% e 67,3%, respectivamente, enquanto coumaphos resultou em baixa eficiência (11,7%). Exceto para ninfas (63,3%) e para fêmeas não alimentadas (80,0%) expostas ao coumaphos, todos os outros estádios de carrapato e fêmeas não alimentadas foram sensíveis a todos os produtos químicos testados.

Fauna ixodológica do pavilhäo auricular de eqüinos em municípios de Minas Gerais e da Bahia / Ixodological populations of the ears of equines in Minas Gerais and Bahia, Brazil

Between June/1990 and February/1991, an experiment about ixodological populations of the ears of equines from counties of Minas Gerais and from Guanambi, Bahia, was carried out. Anocentor nitens was the mostprevalent (97.50 per cent) and most abundant (98.35 per cent) species, followed by Boophilus microplus (36.10 per cent and 1.59 per cent) and Amblyomma cajennense (20.50 per cent e 0.06 per cent). The larvae of A. nitens and B. microplus were more prevalent than the other parasitic stages, and we didn't find larvae of A. cajennense. The ratios between male and female were 3.5 and 1.7, to B. microplus and A. nitens, respectively (

Aspectos biológicos do Dermacentor nitens (Neumann, 1897) em condiçöes de laboratório / Biological aspects of the Dermacentor nitens (Neumann, 1897) in the laboratory

Realizou-se estudo sobre aspectos biológicos da fase näo parasitária do Dermacentor nitens proveniente de equinos de vários municípios de Minas Gerais e de Guanambi, Bahia. Entre as várias amostras estudadas, verificaram-se diferenças nos percentuais de eclosäo e nos índices de eficiência reprodutiva em decorrência do grande número de fêmeas ingurgitadas que näo realizou postura, e semelhanças nos períodos de pré-postura, postura e incubaçäo, sugerindo constante fluxo gênico entre as populaçöes estudadas

Teste "in vitro" de sensibilidade a acaricidas em fêmeas ingurgitadas de Dermacentor nitens (Neumann, 1897) oriundas de equinos de Minas Gerais e Bahia / \"In vitro\" susceptibility to acaricides of Dermacentor nitens (Neumann, 1897) engorged females of equines

Avaliou-se a sensibilidade de fêmeas ingurgitadas de Dermacentor nitens provenientes de equinos de vários municípios de Minas Gerais e de Guanambi, Bahia, frente a acaricidas de bases fosforado, piretróide e fosforado + piretróide. Observaram-se diferenças de sensibilidade ao produto fosforado entre as amostras estudadas. Com exceçäo da amostra proveniente de Montalvânia/Varzelândia, todas as amostras foram igualmente sensíveis ao produto piretróides e todas elas sensíveis ao produto misto