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PubMed1997

Experimental infestation of Gallus gallus with Ornithodoros (Alectorobius) amblus (Ixodoidea: Argasidae).

Ornithodoros (Alectorobius) amblus Chamberlin 1920 specimens were collected from a seagull (Larus spp.) nest in northern Chile. This reports the occurrence of this species outside Peru. The biology of 79 specimens reared under laboratory conditions at 27 degrees C, 75-80% RH, and total darkness was determined. A 13% mortality rate from larval to adult was observed. Larval ticks were fed on chicks, Gallus gallus domesticus; and nymphs and adults were fed on chickens. We recorded the number of eggs per female per gonotrophic cycle and the mean duration of the periods of preoviposition, oviposition, and incubation. The total duration of their life cycle ranged from 111 to 239 d, depending on the number of molts. Males were found after the 4th molt, and after the 5th molt the proportion of females was greater than that of males or remaining nymphs. The feeding period of larvae was 4-6 d, N1 nymphs do not feed. The N2-N6 nymphs, males and females, had a 10- to 60-min feeding period. From N2 on, there was emission of coxal fluid while on the host and during or immediately after feeding.

Animals↗
PubMed2006

Maternal food provisioning in relation to condition-dependent offspring odours in burrower bugs (Sehirus cinctus).

The sensory modalities used for communication among family members have at least partly evolved within an organism's pre-existing sensory context. Given the well-known general importance of chemical communication in insects, we hypothesized in sub-social insects with parental care that chemical signals emitted by larvae to influence parental care (i.e. solicitation pheromones) would have evolved. To test this hypothesis, we performed an experiment in the burrower bug Sehirus cinctus (Hemiptera: Cydnidae) where nymphs were hand-reared under high- or low-food conditions. These hand-reared clutches were used as a source of volatiles. The volatiles were collected for chemical analysis and delivered to caring mothers to quantify their behavioural response. As predicted, mothers exposed to volatiles from nymphs in poor condition provisioned significantly more food than those exposed to air (controls) or volatiles from high-condition nymphs. Chemical analysis revealed that nymphs emitted a blend of eight compounds of which alpha-pinene and camphene showed the strongest relationship with food treatment. Exposure to pure synthetic alpha-pinene and camphene did not affect maternal provisioning, however, suggesting that the functional significance of alpha-pinene and/or camphene may occur in a blend with other compounds. This study shows a clear effect of condition-dependent offspring odours on maternal food provisioning and identifies, for the first time, candidate compounds for a potential chemical offspring begging signal.

Animal Communication↗
PubMed1989

Viral interference in the tick, Rhipicephalus appendiculatus. I. Interference to oral superinfection by Thogoto virus.

Interference between arboviruses in a naturally infected tick vector is reported for the first time. Rhipicephalus appendiculatus nymphs were dually infected with Thogoto (THO) virus, a tick-borne virus, similar to members of the family Orthomyxoviridae. In the first series of experiments examining 'inter-stadial' interference, larvae were orally infected with a temperature-sensitive (ts) mutant, and after moulting the nymphs were superinfected with the wild-type (wt) virus. In the second series of experiments examining 'intra-stadial' interference, nymphs were dually infected by interrupted feeding; the time interval between infective feeds was either shorter than 24 h or lasted for 10 days. Interference was demonstrated by the inability of wt virus to replicate in ticks previously infected with ts virus. Both inter- and intra-stadial interference were observed and complete interference was detected in 78% of dually infected nymphs. A pool of dually infected ticks, in which intra-stadial interference had been detected, failed to transmit the superinfecting virus after moulting.

Animals↗
PubMed2006

Relative abundance and survival of the tick Amblyomma americanum collected from sunlit and shaded habitats.

The population density of host-searching nymphal and adult lone star ticks, Amblyomma americanum (L.) (Acari: Ixodidae), was determined at the Robinson tract of the Kansas Ecological Reserves and a private farm 5 km north-west of the Robinson tract using standard drag cloth methods. Nymphs, males and females were counted and collected weekly from shaded habitats and adjacent sunlit habitats from mid-May through late July, 2003. Of the 1598 nymphs and 549 males collected by drag sampling, 74.0% and 72.1%, respectively, were collected from shaded sections of the habitats, whereas 77.3% of 472 females were found in sunlit sections. A. americanum collected during each sampling period were maintained unfed at >95% relative humidity and a 14 : 10 h photoperiod, and survival was recorded weekly until all ticks had died. Survival of nymphs, males and females did not differ between ticks collected in the shade vs. those collected in the sun. Nymphs survived significantly longer than adults, whereas male and female survival did not differ from each other. These results suggest that host-searching A. americanum populations may partition their environment to increase the chances of coming into contact with a potential vertebrate host.

Animals↗
PubMed2001

Analysis of Borrelia burgdorferi vlsE gene expression and recombination in the tick vector.

Expression and recombination of the antigenic variation vlsE gene of the Lyme disease spirochete Borrelia burgdorferi were analyzed in the tick vector. To assess vlsE expression, Ixodes scapularis nymphs infected with the B. burgdorferi strain B31 were fed on mice for 48 or 96 h or to repletion and then crushed and acetone fixed either immediately thereafter (ticks collected at the two earlier time points) or 4 days after repletion. Unfed nymphs also were examined. At all of the time points investigated, spirochetes were able to bind a rabbit antibody raised against the conserved invariable region 6 of VlsE, as assessed by indirect immunofluorescence, but not preimmune serum from the same rabbit. This same antibody also bound to B31 spirochetes cultivated in vitro. Intensity of fluorescence appeared highest in cultured spirochetes, followed by spirochetes present in unfed ticks. Only a dim fluorescent signal was observed on spirochetes at the 48 and 96 h time points and at day 4 postrepletion. Expression of vlsE in vitro was affected by a rise in pH from 7.0 to 8.0 at 34 degrees C. Hence, vlsE expression appears to be sensitive to environmental cues of the type found in the B. burgdorferi natural history. To assess vlsE recombination, nymphs were capillary fed the B. burgdorferi B31 clonal isolate 5A3. Ticks thus infected were either left to rest for 4 weeks (Group I) or fed to repletion on a mouse (Group II). The contents of each tick from both groups were cultured and 10 B. burgdorferi clones from the spirochetal isolate of each tick were obtained. The vlsE cassettes from several of these clones were amplified by PCR and sequenced. Regardless of whether the isolate was derived from Group I or Group II ticks, no changes were observed in the vlsE sequence. In contrast, vlsE cassettes amplified from B. burgdorferi clones derived from a mouse that was infected with B31-5A3 capillary-fed nymphs showed considerable recombination. It follows that vlsE recombination does not occur in the tick vector.

Animals↗
PubMed2006

MyD88 deficiency enhances acquisition and transmission of Borrelia burgdorferi by Ixodes scapularis ticks.

Borrelia burgdorferi strains exhibit various degrees of infectivity and pathogenicity in mammals, which may be due to their relative ability to evade initial host immunity. Innate immune cells recognize B. burgdorferi by Toll-like receptors (TLRs) that use the intracellular molecule MyD88 to mediate effector functions. To determine whether impaired TLR signaling enhances Ixodes scapularis acquisition of B. burgdorferi, we fed nymphs on wild-type (WT) and MyD88-/- mice previously infected with two clinical isolates of B. burgdorferi, BL206, a high-virulence strain, and B348, an attenuated strain. Seventy-three percent of the nymphs that fed on BL206-infected WT mice and 40% of the nymphs that fed on B348-infected WT mice acquired B. burgdorferi, whereas 100% of the nymphs that fed on MyD88-/- mice became infected, irrespective of B. burgdorferi strain. Ticks that acquired infection after feeding on MyD88-/- mice harbored more spirochetes than those that fed on WT mice, as assessed by quantitative PCR for B. burgdorferi DNA. Vector transmission of BL206 and B348 was also enhanced when MyD88-/- mice were the blood meal hosts, with the mean pathogen burden at the skin inoculation site significantly higher than levels in WT mice. These results show that the absence of MyD88 facilitates passage of both low- and high-infectivity B. burgdorferi strains between the tick vector and the mammal and enhances the infectivity of a low-infectivity B. burgdorferi strain.

Adaptor Proteins, Signal Transducing↗
PubMed1991

A cloned DNA probe identifies Cowdria ruminantium in Amblyomma variegatum ticks.

Heartwater, caused by Cowdria ruminantium and transmitted by ticks of the genus Amblyomma, is a constraint to ruminant animal production in sub-Saharan Africa. This rickettsial disease could spread from endemically infected areas of sub-Saharan Africa and certain Caribbean islands to other countries, including the United States, in which Amblyomma ticks exist. To detect C. ruminantium in tick vectors and animals, we made DNA probes from C. ruminantium DNA isolated from endothelial cell cultures. Two clones were evaluated; pCS20 from Crystal Springs (Zimbabwe) strain DNA had a 1,306-bp insert, and pCR9 from Kiswani (Kenya) strain DNA had a 754-bp insert. Both DNA probes detected 1 ng of Crystal Springs DNA; however, the pCS20 probe had a 10-fold-greater ability to discriminate between C. ruminantium DNA and DNA from other organisms. Also, the pCS20 probe did not hybridize to 400 ng (highest amount tested) of DNA from bovine cells, 3 protozoa, 3 rickettsiae, and 12 bacteria. In all experiments, C. ruminantium DNA was detected in midguts from 99 of 160 Amblyomma variegatum nymphs infected as larvae and in midguts from 38 of 80 adult ticks infected as nymphs but not in midguts from control nymphs and adults. The presence of C. ruminantium in nymphs and adults was confirmed by transmission of heartwater to goats. The DNA sequences of both probes were determined; synthetic oligonucleotides from pCS20 are recommended as DNA probes for C. ruminantium.

Animals↗
PubMed1995

Effect of ambient temperature on competence of deer ticks as hosts for Lyme disease spirochetes.

We determined whether the temperature of extrinsic incubation affects the competence of vector ticks as hosts for Lyme disease spirochetes (Borrelia burgdorferi). Larval Ixodes dammini ticks that had engorged on spirochete-infected C3H mice were incubated continuously at various temperatures, and the gut contents of the resulting nymphs were examined for spirochetes by direct immunofluorescence microscopy. Spirochetes were present in virtually all nymphs kept at 27 degrees C or less for 6 months, in only 10% of those kept at 33 degrees C, and in none kept at 37 degrees C. Spirochetes became undetectable within 8 weeks when nymphs were warmed from 27 to 33 degrees C beginning at the time of molting. Nymphs became virtually noninfective for mice after incubation at temperatures higher than 27 degrees C for 2 weeks or longer. We conclude that ambient temperatures in excess of 27 degrees C are not permissive for transmission of the agent of Lyme disease.

Animals↗
PubMed2000

Temporal changes in outer surface proteins A and C of the lyme disease-associated spirochete, Borrelia burgdorferi, during the chain of infection in ticks and mice.

The Lyme disease-associated spirochete, Borrelia burgdorferi, is maintained in enzootic cycles involving Ixodes ticks and small mammals. Previous studies demonstrated that B. burgdorferi expresses outer surface protein A (OspA) but not OspC when residing in the midgut of unfed ticks. However, after ticks feed on blood, some spirochetes stop making OspA and express OspC. Our current work examined the timing and frequency of OspA and OspC expression by B. burgdorferi in infected Ixodes scapularis nymphs as they fed on uninfected mice and in uninfected I. scapularis larvae and nymphs as they first acquired spirochetes from infected mice. Smears of midguts from previously infected ticks were prepared at 12- or 24-h intervals following attachment through repletion at 96 h, and spirochetes were stained for immunofluorescence for detection of antibodies to OspA and OspC. As shown previously, prior to feeding spirochetes in nymphs expressed OspA but not OspC. During nymphal feeding, however, the proportion of spirochetes expressing OspA decreased, while spirochetes expressing OspC became detectable. In fact, spirochetes rapidly began to express OspC, with the greatest proportion of spirochetes having this protein at 48 h of attachment and then with the proportion decreasing significantly by the time that the ticks had completed feeding. In vitro cultivation of the spirochete at different temperatures showed OspC to be most abundant when the spirochetes were grown at 37 degrees C. Yet, the synthesis of this protein waned with continuous passage at this temperature. Immunofluorescence staining of spirochetes in smears of midguts from larvae and nymphs still attached or having completed feeding on infected mice demonstrated that OspA but not OspC was produced by these spirochetes recently acquired from mice. Therefore, the temporal synthesis of OspC by spirochetes only in feeding ticks that were infected prior to the blood meal suggests that this surface protein is involved in transmission from tick to mammal but not from mammal to tick.

Animals↗
PubMed1998

Programmed cell death specifically eliminates one part of a locust pleuroaxillary muscle after the imaginal moult

In the hemimetabolous insect Locusta migratoria, fundamental restructuring occurs at the transition from flightless nymph to flight-capable adult. This transition involves all components of the flight circuit, which is present but not used for flight in nymphs. The meso- and metathoracic pleuroaxillary muscles, M85 and M114 respectively, constitute one component of this circuit. In the adult locust, these are flight-steering muscles, but their function in the nymph is as yet unknown. Our study reveals that adult and nymphal metathoracic pleuroaxillary muscles M114 differ profoundly. The nymphal muscle contains the distinct part M114c in addition to parts M114a and M114b characteristic of the adult. The contractions of M114c are slow and long-lasting, corresponding to its long sarcomeres and slow form of ATPase, and contrast with the adult muscle parts M114a and M114b in all of these features. We demonstrate a hormone-dependent degeneration of M114c after the adult moult. This degeneration can be blocked by actinomycin D and cycloheximide. It may thus be termed genetically programmed cell death, triggered after the adult moult and, as demonstrated here, functioning via the ATP-dependent ubiquitin pathway. Given the defined onset of degeneration after the adult moult, it is possible that M114c may fulfil a specific function in nymphs, during or shortly after moulting.

Journal Article↗
PubMedDate not supplied

[Xenodiagnosis in Chagas disease: influence of the triatominae sex].

We evaluated, comparatively, the performance of female and male Triatoma infestans in the 5th instar of development, in xenodiagnosis for Chagas' disease. Xenodiagnosis were done in 40 patients with chronic infectans. For each diagnosis 20 nymphs female and 20 nymphs males were used, which were weighed immediately before and after the meal. Intestinal contents were examined about 20, 30, 60 and 90 days after the xenodiagnosis application. The females and males ingested the mean of 230 and 210 mg of blood, respectively. The results revealed positivity of 15 (37.5%) out of 40 xenodiagnosis, but any of the positive tests show 100% of the nymphs, female and/or male infected by T. cruzi. The females ingested significantly more blood than the males; this is coincidental with the higher female positivation to T. cruzi here observed. Our results suggest that the female nymphs seem able to increase the sensibility of the xenodiagnosis for chronic patients with Chagas' disease being necessary further studies are necessary to confirm this hypothesis.

Animals↗
PubMedDate not supplied

Relative susceptibility of different stages of Rhodnius prolixus to the entomopathogenic hyphomycete Beauveria bassiana.

Laboratory bioassays were conducted to determine the relative susceptibility of eggs, 1st-, 3rd-, 5th-instar nymphs and adults of Rhodnius prolixus to one isolate of the entomopathogenic hyphomycete, Beauveria bassiana. Treatments consisted of directly spraying on insects of increasing doses of inoculum (3 x 10(2) to 3 x 10(5) conidia per cm2). Mortality due to all doses of conidia was very high in the five tested stages of the target insect. Experiments on eggs demonstrated that the fungal isolate was able to kill eggs before they hatched. Both time-mortality and dose-mortality responses showed that the susceptibility of R. prolixus varied according to its stage of development and increased with age. As a matter of fact, at the dose of 3 x 10(3) conidia per cm2, LD 50 varied between 11.2 days in 1st-instar nymphs and 6.4 days in both 5th-instar nymphs and adults. Comparison of LD50 permitted to estimate that 1st-instar nymphs were about 700-fold less susceptible than the two oldest stages.

Animals↗
PubMedDate not supplied

Residual effect of lambdacyhalothrin on Triatoma infestans.

Insecticidal residual effect and triatomine infestation rates in houses of a community fumigated with lambdcyhalothrin (Icon) are reported. No mortality was observed in 5th-instar Triatoma infestans nymphs in 72-hr exposure test on three different surfaces, one month after fumigation for a dose of 31.5 mg am/m2. However, during post-exposure observation a mortality of 60% was recorded for those insect exposed on sprayed woodboard. The results observed with mud-containing treated walls, were markedly poorer (0% of mortality). Twelve month after spraying 40% of mortality was observed on first-instar T. infestans nymphs in 72-hr exposure test on woodboard, but lower mortality rates were observed in mud-containing materials. When the effect of deltamethrin (109 mg ai/m2) and lambdcyhalothrin (94 mg ai/m2) was compared, the former did not appear to be superior at similar loads. Both have showed a mortality rate of 30% on 5th-instar T. infestans nymphs three months post-fumigation. The dose utilized in the field fumigation was enough to get a significant (p < 0.0001) control of triatomine domestic infestation, since it was sufficient to keep 95% of the houses uninfested throughout 21 months following treatment, when compared with baseline situation. A remarkable knock-down effect on adult and nymphs forms of the insect and a high in situ mortality were observed as a result of its application, even at very low doses.

Animals↗
PubMed2006

Susceptibility of twolined spittlebug (Hemiptera: Cercopidae) life stages to entomophagous arthropods in turfgrass.

Prosapia bicincta (Say) (Hemiptera: Cercopidae), the twolined spittlebug, is an economic pest of turfgrass in the southeastern United States. No data concerning natural enemies of P. bicincta in turfgrass have been reported previously. We compared predation of spittlebug eggs, nymphs, and adults in the laboratory by potential generalist predators commonly found in turfgrass: bigeyed bugs Geocoris uliginosus Say and Geocoris punctipes Say; red imported fire ant, Solenopsis invicta Buren; wolf spiders (Lycosa sp. Walckenaer); carabid beetles Harpalaus pensylvanicus DeGeer and Calosoma sayi Dejean; and tiger beetles Megacephala carolina carolina L. Eggs were readily consumed by generalist predators. S. invicta consumed 100% of the eggs offered. H. pensylvanicus and C. sayi were also significant predators of P. bicincta eggs. Nymphs live in spittlemasses that protect them from attack by predators, but exposed nymphs were susceptible to attack when mechanically removed from their spittlemasses. S. invicta and M. carolina carolina caused significant mortality of exposed nymphs. P. bicincta adults are aposematic and have the ability to reflex bleed; however, reflex bleeding did not prevent attack by predators. S. invicta and M. carolina carolina killed 100% of the adult spittlebugs offered in laboratory bioassays. Lycosa sp. are less voracious predators of adults. Sound background knowledge about P. bicincta and its potential natural enemy complex is important for the development and implementation of a detailed, site-specific, biologically based pest management program in turfgrass.

Animals↗
PubMed2000

Abiotic parameters and diel and seasonal activity of Borrelia-infected and uninfected Ixodes persulcatus (Acarina: Ixodidae).

During the 1997 season of Ixodes persulcatus Schulze tick activity, 579 specimens were collected by flagging in the vicinity of St. Petersburg (Morskaja, Lisy Nos). Collections were made from April to July, and at each collection time the following measurements were recorded: light intensity (in lux); temperature of soil 1-1.5 cm below leaf litter, at the soil surface, and in the air 1.5 m above the soil surface; and relative humidity. The gradient between soil at a depth of 1-1.5 cm and soil surface temperatures appeared to be the main physical parameter that initiated tick migration out of the leaf litter. At soil temperature intervals of 5-10 degrees C and 21-26 degrees C, ticks were found only when the soil temperature 1-1.5 cm below the soil surface was colder than at its surface. When temperature ranged from 11 to 20 degrees C, 24% of the ticks were collected when the surface temperature was colder than that below the soil surface. Sixty percent of the ticks, especially nymphs, were collected when the soil surface and subsoil temperature difference ranged from 0 to 2.0 degrees C. The gradient between soil temperature and relative humidity appeared to increase the importance of the gradient between the soil and surface temperature at which time the maximum number of ticks were caught. Borrelia burgdorferi sensu lato infected ticks were collected only after 1100 hours. Prior to and just after 1100 h the mean difference between soil temperatures was 4.7 degrees C, whereas the mean difference between soil and surface temperatures was 6.4 degrees C at this time. The most important factors that influenced the appearance of Borrelia-infected ticks were the temperature gradients that existed between the surface and soil temperatures and the soil and air relative humidity. Greater numbers of infected nymphs were collected when temperature intervals ranged from 10 to 14 degrees C and lower numbers were collected between 15 and 20 degrees C. No Borrelia-infected nymphs were captured when the temperature interval ranged from 21 to 26 degrees C. Infected adults appeared to be more tolerant of higher temperatures than Borrelia-infected nymphs. A significant relationship was found between the activity of Borrelia-infected I. persulcatus and the temperature of the air, soil below the surface, at the soil surface, and relative humidity.

Animals↗
PubMed2001

Infection of Ixodes scapularis (Acari: Ixodidae) with Borrelia burgdorferi using a new artificial feeding technique.

To study interactions between Ixodes scapularis (Say) and Borrelia burgdorferi, an artificial feeding system was refined to allow controlled manipulation of single variables. The feeding system uses a mouse skin mounted on a water-jacketed glass membrane feeder. I. scapularis were infected using either BSK-H-cultured B. burgdorferi spirochetes or a B. burgdorferi-infected mouse skin as the source of spirochetes. Sixty-six percent of nymphs successfully fed to repletion using the artificial feeding systems with at least 75% of nymphs becoming infected with B. burgdorferi. Strain B31 B. burgdorferi spirochetes from passages 2-17 were equally infectious to nymphal ticks. At concentrations of one spirochete per microliter, 12% of nymphs acquired infection and 14 and 100 spirochetes per microliter resulted in 50 and 100% infection rates, respectively. Eighty-nine percent of nymphs fed by artificial feeding molted to the adult stage. When subsequently fed as adults, these I. scapularis successfully transmitted infectious B. burgdorferi spirochetes to mice.

Animals↗
PubMed2002

Notes on parasitism by Amblyomma humerale (Acari: Ixodidae) in the state of Rondônia, western Amazon, Brazil.

The tick Amblyomma humerale Koch is endemic to South America. All host records refer to the adult stage parasitizing tortoises, mostly yellow-footed tortoise, Geochelone denticulata (L.), and red-footed tortoise, Geochelone carbonaria (Spix). The current study reports the presence of A. humerale in the state of Rondônia, Brazil. A total of 215 adult ticks (201 males, 14 females) was collected from six G denticulata in an Indian reserve and nine Geochelone sp. in rural Monte Negro County, giving an overall mean infestation of 14.3 +/- 12.0 (range: 2-44) ticks per tortoise. Male ticks always outnumbered females on the host and nine tortoises had only male ticks. Male ticks were mostly attached in clusters on the ventral sides of the carapace near the anterior and posterior margins, and more rarely on the outer margin of the plastron. All females were found attached to the tortoise skin, at different sites such as head, neck, shoulders or legs. Male ticks were rarely observed attached to the body skin. Seven engorged nymphs collected on small vertebrates from Monte Negro County molted to adults of A. humerale. This included one nymph each on the seven-colored lizard, Plica plica (L), green tree climber, Plica umbra (L.), and wide-foraging lizard, Kentropyx calcarata Spix,three nymphs on the common opossum, Didelphis marsupialis L., and one nymph on the silky anteater, Cyclopes didactylus L. These constitute the first host records for the immature stages of the tick A. humerale.

Animals↗
PubMed2003

Larval behavioral diapause regulates life cycle of Amblyomma cajennense (Acari: Ixodidae) in Southeast Brazil.

Previous studies have determined that Amblyomma cajennense (F.) produces one generation per year in Southeastern Brazil. Larvae predominate from April to July, nymphs from July to October, and adults from October to March. In the current study, we observed engorged females, their eggs, and respective larvae in the field. Engorged females were released in grass plots under natural conditions, at monthly intervals, from October 2000 to March 2001. Preoviposition periods lasted 1-2 wk, and mean egg incubation periods lasted 5-7 wk. Consequently, larvae hatched at different periods from early December 2000 to early April 2001. However, all hatched larvae stayed confined to the plot ground, under the vegetation, until late April or early May 2001, when some larvae were seen questing on top of vegetation for the first time. Thereafter, larvae were always seen on this questing position until August 2001, when all larvae had died on the plots. In addition, premolt period data of engorged larvae and nymphs held in laboratory at different temperatures were used to construct a premolt mathematical model, which was applied to reported seasonal dynamic data of A. cajennense in the field. The premolt model indicated that the field intervals between larvae and nymphs and between nymphs and adults are controlled solely by nondiapause events, such as ground temperature. We concluded that the 1-yr generation pattern of A. cajennense in Southeastern Brazil is primarily controlled by larval behavioral diapause, shown by larvae born during spring/summer months, before their activity period at next autumn.

Animals↗