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PubMed1979

The production of nymphs of Hyalomma anatolicum anatolicum for experimental infection with Theileria annulata.

Methods are described for the production of nymphs of Hyalomma anatolicum anatolicum for later use in transmission experiments with Theileria annulata where the timing of the application of nymphs to infected cattle needs to be accurately controlled. Larvae are fed on the torsos of rabbits where approximately 98% undergo a two-host feeding cycle. This cycle is interrupted 2 days after the first larvae moult into nymphs by killing the rabbits and the nymphs are then collected with a suction pump. Nymphs produced by the interrupted larval feeding method feed well on cattle, in regard to timing of detachment and weight, compared with nymphs produced by interrupted feeding on rabbits.

Animals↗
PubMed2006

The natural hosts for larvae and nymphs of Amblyomma neumanni and Amblyomma parvum (Acari: Ixodidae).

Based on the hypothesis that birds and rodents are important hosts for subadults of the Neotropical Amblyomma neumanni and Amblyomma parvum ticks, a survey of these type of hosts was carried out from July 2004 to March 2006, in Quilino (A. parvum) and Dean Funes (A. neumanni), Córdoba province, Argentina. Additionally, monthly tick counts were performed on cattle and goats with occasional tick search in other domestic hosts. Records of questing height of subadult ticks on vegetation were also carried out monthly. Rodents (n = 123) and birds (n = 122) captured in Dean Funes showed no infestation with A. neumanni. Apart of few nymphs found on horses, all larvae and nymphs of A. neumanni were on cattle with a larval prevalence and mean number of 22.2%, and 7.7 +/- 22.52, respectively, and a prevalence of nymphs of 47.8% with a mean of 7.9 +/- 18.49. The average questing height of larvae and nymphs of A. neumanni was 23.5 +/- 17.1 cm and 30.7 +/- 26.7 cm, respectively. A total of 138 rodents and 130 birds were captured in Quilino but the Caviidae rodent Galea musteloides carried 99.3% of larvae and 99.8% of nymphs of A. parvum, and no immature stages were detected on cattle, goat or vegetation. Tick counts on G. musteloides (n = 74) showed a prevalence of 42% and a mean number of 9.9 +/- 24.83 for larvae, while nymphal infestation had a prevalence of 56.5% and a mean of 8.7 +/- 11.31. Cattle appear to be suitable hosts to sustain the complete cycle of A. neumanni in nature (adult ticks infest cattle too) and questing height of subadults indicates that they are expecting to feed on medium and large-sized mammals, such as cattle and other ungulates. At least in the study site, G. musteloides is the principal host for the survival strategy of A. parvum subadults; adult ticks are common on cattle and goats. These hosts are introduced in the Neotropics but A. neumanni was able to develop a surrogate cycle independent of native hosts while A. parvum still depends on probably primeval hosts to sustain their larvae and nymphs.

Animals↗
PubMed1994

Harborage width preferences of German cockroach (Dictyoptera: Blattellidae) adults and nymphs.

Adults and nymphal cohorts of the German cockroach, Blattella germanica (L.), were allowed 24 h to select preferred harborage widths from eight harborages between 1.59 and 12.72 mm (increments of 1.59 mm) in both individual and combined cohort studies. In individual cohort studies, 1- and 2-wk-old nymphs significantly preferred 1.59-mm-wide harborage, with 74 and 68%, respectively; 3- and 4-wk-old nymphs significantly preferred 3.18-mm-wide harborage, with 63 and 45%, respectively; 5-wk-old nymphs selected the 4.77-mm-wide harborage; and 6-wk-old nymphs were evenly distributed in 3.18- to 9.54-mm-wide harborages. Males were in 6.36- to 12.72-mm-wide harborages. Nongravid females (81%) were in 4.77-, 6.36-, and 11.13-mm-wide harborages; gravid females (94%) preferred 4.77- and 6.36-mm-wide harborages. The percentage of nymphs outside harborages decreased as cockroach age increased from 1 to 5 wk. In combined cohort studies, preferred harborage widths for all cohorts and sexes were 6.36-7.95 mm and 11.13-12.72 mm. The percentage of nymphs outside harborages was low and constant (< 4.57%) irrespective of age or sex.

Animals↗
PubMed1992

Immunization of rabbits against nymphs of Amblyomma hebraeum and A. marmoreum (Acari: Ixodidae).

Himalayan rabbits immunized with homogenates prepared from nymphs of Amblyomma hebraeum Koch and A. marmoreum Koch ticks developed humoral and probably also cell-mediated immunity to their respective homogenates. Beta and gamma globulin levels and numbers of eosinophils and neutrophils increased significantly in inoculated rabbits. The recipient animals developed resistance to homospecific nymphal infestations. Cross resistance between the two species was not evaluated. Nymphs of both species that fed on inoculated rabbits demonstrated slightly shorter feeding periods, and their mean weights were significantly lower than nymphs that fed on Quil 'A' adjuvant-inoculated rabbits or on naive rabbits. Significantly higher proportions of nymphs from immunized animals failed to moult when compared with nymphs that fed on the two control groups. These parameters indicate that the inoculated rabbits had acquired protective immunity against nymphs of both ticks.

Animals↗
PubMed1996

Dispersal of blacklegged tick (Acari:Ixodidae) nymphs and adults at the woods-pasture interface.

Marked nymphal and adult blacklegged ticks, Ixodes scapularis Say, were released in 4 host-exclusion cages and 4 similar control areas, all straddling the woods-pasture interface. Both nymphs and adults were recaptured by flagging at regular intervals outside the cages, having therefore actively dispersed > 4.5 m (i.e., without involvement of vertebrates). Nymphs were recaptured much more often ( > 90%) in the woods than pastures, whereas 62.8% of recaptured adults were taken in pastures. Females were recaptured in equal numbers in pastures and woods, but 75.4% of recaptured males were in pastures. Adults that dispersed into pastures were recaptured an average of 1.6 and 3.7 m from the woods edge in 1992 and 1993, respectively, and as far as 7-8 m from the woods edge. Nymphs dispersed shorter distances than adults with 66% of the recaptured nymphs found 2-3 m from their release points, and > 46% of recaptured adults found > 5 m from their release points. Twice as many nymphs were recaptured from the caged than uncaged sites. The lower numbers of nymphs recaptured from control sites compared with caged sites are probably the result of host acquisition; the absence of this discrepancy with the adults may reflect by their ability to move relatively quickly from the host-exclusion cages and become available for host contact.

Animals↗
PubMed2006

Predicting density of Ixodes pacificus nymphs in dense woodlands in Mendocino County, California, based on geographic information systems and remote sensing versus field-derived data.

Ixodes pacificus nymphs are the primary vectors to humans of Borrelia burgdorferi, the etiologic agent of Lyme disease, in California. We used a supervised classification model, based on remote sensing (RS) data from multi-seasonal Landsat TM 5 images, to identify the key habitat in Mendocino County where humans are exposed to I. pacificus nymphs (woodlands carpeted with leaf litter). The model, based on the normalized difference vegetation index (NDVI), brightness, and wetness, separated the nymphal risk habitat (52.6% of the county) from other habitat types with > 93% user and producer accuracies. Next, we determined the density of questing nymphs in 62 woodland-leaf areas located throughout Mendocino County and created forward-stepwise regression models explaining the variation in nymphal density based on traits attainable by a lay-person in the field (e.g., tree species present, deer signs; r(2) = 0.43, P < 0.0001), or geographic information systems (GIS)/RS-based environmental data (r(2) = 0.50, P < 0.0001). The GIS/RS model, using July NDVI, November greenness, a coastal influence category, May solar insolation, November hours of sunlight, and dominant hydrologic grouping as input variables, was 22% more accurate in predicting nymphal density at 16 validation sites (r(2) = 0.72) than the field-derived data model (r(2) = 0.50). The habitat classification and GIS/RS models were combined to create a continuous nymphal density surface for the entirety of Mendocino County. This risk surface showed that 11.9% of the county was classified as habitat posing at least moderate risk of human exposure to nymphs (> 6.4 nymphs per 100 m(2)). Furthermore, high-risk areas (> 10.5 nymphs per 100 m(2); 1.7% of the county) tended to cluster in the central interior and most heavily populated region of Mendocino County, but were rare in the proximity of coastal population centers.

Animals↗
PubMed2003

A cautionary note: survival of nymphs of two species of ticks (Acari: Ixodidae) among clothes laundered in an automatic washer.

Host-seeking ticks often remain on clothing of persons returning home from work or recreation in tick habitats, and can pose at least a temporary risk to people and pets in these homes. Laundering clothing has been one of the recommendations to reduce tick exposure. Host-seeking lone star tick, Amblyomma americanum (L.), and blacklegged tick, Ixodes scapularis Say, nymphs confined in polyester mesh packets, were included with laundry in cold, warm, and hot wash cycles of an automatic clothes washer. Ticks were also placed with washed clothing and subjected to drying in an automatic clothes dryer set on high heat and on air only (unheated). Most nymphs (> or = 90%) of both species survived the cold and warm washes, and 95% of A. americanum nymphs survived the hot wash. At the time of their removal from the washer, I. scapularis nymphs were clearly affected by the hot wash, but 65% were considered alive 20-24 h later. Large percentages of nymphs of both species survived hot washes in which two other detergents (a powder containing a nonchlorine bleach and a liquid) were used. All ticks were killed by the 1 h cycle at high heat in the clothes dryer, but with unheated air some nymphs of both species survived the 1 h cycle in the dryer. Given the laundering recommendations of clothing manufacturers and variation in the use automatic clothes washers, laundry washed in automatic washers should not be considered free of living ticks.

Animals↗
PubMed2002

Photoperiodic control of developmental diapause in nymphs of prostriate ixodid ticks (Acari: Ixodidae).

Extrinsic control of developmental diapause in nymphs of prostriate ticks of the subgenus Ixodes sensu stricto (Ixodes ricinus and Ixodes persulcatus from Eurasia and Ixodes scapularis from North America) appears to be based on a complex two-step photoperiodic reaction of a short-day/long-day type. Diapause control in the subgenus Afrixodes (the South African tick Ixodes rubicundus) appears to be based on a simple long-day reaction. The option between non-diapause development and diapausing arrest in engorged nymphs is determined by both pre- and post-feeding photoperiodic regimes. Consequently diapausing arrest in engorged nymphs of Ixodes sensu stricto can be induced either by a short-day (after their engorgement) or by a long-day regime (in unfed nymphs), while active, non-diapause development is possible only when the short-day pre-feeding regime is followed by a long-day post-feeding regime. The photoperiodic response in I. (Afrixodes) rubicundus nymphs seems to be of the long-day type both before and after feeding. Consequently this non-diapause development is enabled by a long-day regime, while diapause is induced by a short-day regime of exposure. Nevertheless, there are some indications that the control of nymphal diapause in the latter species is also of a complex nature.

Animals↗
PubMed1992

Inability of Ixodes cookei and Amblyomma americanum nymphs (Acari: Ixodidae) to transmit Borrelia burgdorferi.

The vector competency of Ixodes cookei Packard and Amblyomma americanum (L.) for Borrelia burgdorferi was studied using Syrian hamsters. Ixodes dammini Spielman, Clifford, Piesman & Corwin were used as controls. Darkfield and immunofluorescent examinations of midgut diverticula revealed B. burgdorferi spirochetes in 32 of 36 (88.9%) I. dammini larvae, 5 of 36 (13.9%) I. cookei larvae, and 7 of 36 (19.4%) A. americanum larvae within 48 h after feeding on infected Syrian hamsters. B. burgdorferi were also observed in the midguts of 94 of 107 (87.8%) I. dammini nymphs that developed from the fed larvae. However, none of 30 I. cookei nymphs was positive for spirochetes and only 1 of 60 (1.7%) A. americanum nymphs was found positive for B. burgdorferi. Nymphs of each tick species, reared from larvae that had fed on infected hamsters, were allowed to feed on uninfected hamsters to determine their ability to transmit B. burgdorferi. Transmission was demonstrated only by I. dammini nymphs.

Animals↗
PubMed1999

Abundance of Ixodes scapularis (Acari: Ixodidae) larvae and nymphs in relation to host density and habitat on Long Point, Ontario.

Ixodes scapularis Say populations were evaluated within 4 habitats on Long Point, Ontario, from 1990 to 1992 to ascertain whether differences in density of mouse populations within and among habitats were correlated with that of immature I. scapularis populations. I. scapularis immatures were rarely collected by dragging within the cottonwood dune habitat. Significantly more larvae (P < or = 0.05) were collected by drag sampling within the maple forest habitat than in the oak savannah or white pine habitats for the 1989, 1990, and 1991 cohorts, whereas the size of the 1992 larval cohort did not differ significantly among these habitats. Significantly more nymphs were collected by dragging within the maple forest than in the other 2 habitats for all 4 cohorts. Nymphs from the 1989 and 1990 cohort were more abundant within the oak savannah than the white pine habitat, whereas the 1991 and 1992 cohorts were similar. With few exceptions, I. scapularis immatures were most prevalent on white-footed mice, Peromyscus leucopus (Rafinesque), captured within the maple forest > oak savannah > white pine > cottonwood dune, although differences were not significant in all years and in all habitats. The number of mice captured within the 4 habitats was not correlated with the number of I. scapularis larvae or nymphs infesting them. Likewise, the minimum number of mice alive was not significantly correlated with conversion indices of larvae to nymphs or nymphs to adults. Lack of association between mouse availability and relative size of subsequent cohorts of host-seeking ticks suggests that factors other than the size of the mouse populations were responsible for the observed differences in tick abundance among habitats.

Animals↗
PubMed2002

Development of resistance to nymphs of Amblyomma cajennense ticks (Acari:Ixodidae) in dogs.

Ticks have long been regarded as constraints to humans and domestic animals, but hosts often develop resistance to ticks after repeated infestations. The purpose of this investigation was to study the possible acquisition of immunity in domestic dogs to nymphs of A. cajennense by determining the tick alimentary performance after successive controlled infestations. Mean engorged weight of nymphs was not significantly different among the three infestations; molting rate from nymph to adult ticks, and the percentage of nymph recovery were also very close in all infestations. These results are similar to those obtained in studies of the dog-adult Rhipicephalus sanguineus interface. It is concluded that domestic dogs do not develop resistance against nymphs of A. cajennense ticks.

Animals↗
PubMed2002

A comparison of nutritional regulation in solitarious- and gregarious-phase nymphs of the desert locust Schistocerca gregaria.

Nutritional regulatory responses were compared for the cryptic 'solitarious' and the conspicuously coloured, aggregating 'gregarious' phases of the desert locust Schistocerca gregaria. The desert locust has the genetic potential to exist in either phase, changing between them within a lifetime and epigenetically across generations. Our aim was to compare final-instar nymphs of the two phases with respect to key nutritional variables, including (i) points of regulated intake (the 'intake target') for protein and carbohydrate, (ii) the nature of trade-offs between over-eating nutrients in excess and under-eating those in deficit when fed nutritionally unbalanced foods, (iii) diet-related patterns of nutrient utilisation, and (iv) the performance consequences of eating nutritionally unbalanced diets. When provided with pairs of nutritionally unbalanced but complementary foods, both phases regulated their intake of protein and carbohydrate to a similar point. However, when confined to foods that were of unbalanced protein to carbohydrate ratio, gregarious nymphs ate more than solitarious insects. Both phases regulated protein growth, but gregarious insects did so to a lower adult body protein content and converted ingested protein to growth less efficiently. When fed a food high in carbohydrate and low in protein, gregarious nymphs deposited more body lipid and survived less well than did solitarious insects. Solitarious nymphs developed more quickly than gregarious nymphs except on the two most extremely unbalanced diets, on which development time was similar. The results are discussed with respect to the different nutritional ecologies of the two phases and used to develop the hypothesis that animals have evolved to trade-off the cost of eating excess of a nutritionally unbalanced diet against the probability of encountering foods of complementary composition in the future.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Determination of Anopheles gambiae larval DNA in the gut of insectivorous dragonfly (Libellulidae) nymphs by polymerase chain reaction.

We examined the predator-prey relationship between larvae of the malaria mosquito Anopheles gambiae and nymphs of the dragonfly (Libellulidae). Studies were conducted to determine whether polymerase chain reaction (PCR) can be used to detect DNA of An. gambiae in the gut of libellulid nymphs, and to determine how long after feeding on An. gambiae that mosquito DNA remains detectable by PCR. Total DNA was extracted from the gut contents of libellulid nymphs by using 2 types of DNA extraction methods. The target sequence for the diagnostic PCR was the intergenic spacer regions of the ribosomal DNA gene locus. These sequences were analyzed by using An. gambiae complex-specific primers. After analyzing nymphal gut contents with PCR at regular postfeed intervals, a 390-base pair product could be amplified. The presence of mosquito larvae was visually confirmed for up to 40 min after feeding. Regardless of the number of mosquito larvae ingested, libellulid gut contents could be amplified or visually seen up to 1 h of digestion. This result indicates the nymphs have a high rate of digestion and that PCR with An. gambiae complex primers will be best utilized within 1 h after feeding as a detection system. This study confirmed that dragonfly nymphs feed well on anopheline larvae, and that mosquito DNA, although rapidly digested, can be successfully recovered and detected from within nymphal digestive tracts.

Animals↗
PubMedDate not supplied

[The effect of immersion in distilled water on the engorged larvae and nymphs of Amblyomma cajennense (Fabricius,1787)(Acari: Ixodidae)].

To evaluate the effect of the immersion of engorged larvae and nymphs of Amblyomma cajennense, these stages were immersed by 24, 48, 72 and 96 hours in test tubes containing distilled water. The period of premolt of the nymphs increased proportionally to the time of immersion (p<0.05). The ecdisis period, the longevity and the mortality (days) were similar in all of treatments (p>0.05). The percentage of ecdisis in nymphs was reduced after 72 hours of immersion of the larvae (p<0.05). None of the engorged nymphs survived 96 hours of immersion. The period of the adult premolt increased after 48 hours of immersion (p<0.05). The ecdisis period was similar in the treatments of 24 and 48 hours of immersion (p>0.05). The percentage of ecdisis decreased starting from 24 hours of immersion (p<0.05). There was not statistical difference (p<0.05) between the control group and the 24 hours group of immersion for the parameters longevity and mortality. These findings suggest that the engorged nymphs were more sensitive to the immersion that the engorged larvae.

Animals↗
PubMedDate not supplied

[Sexual dimorphism of the larvae and nymphs of the taiga tick--Ixodes persulcatus].

Manifestations of sexual dimorphism at the preimaginal phase was studied on the laboratory culture of Ixodes persulcatus. It has been found out that larger engorged larvae produce, in general, larger nymphs and smaller larvae produce smaller nymphs. The classification of engorged nymphs into large (over 2.9 mm) and small ones (less than 2.9 mm) has made it possible (with 100% probability) to obtain females from the former and males from the latter. Differences in linear sizes of scutum, gnathosoma and its appendages in male and female nymphs were determined that has made possible the identification of sex in hungry nymphs.

Animals↗
PubMed1995

Effect of temperature and humidity on egg hatch, moulting and longevity of larvae and nymphs of Dermacentor reticulatus (Ixodidae).

Larvae of Dermacentor reticulatus hatched at a temperature range of 20-34 degrees C, but a high egg hatch success of > 90% was only achieved at 20 degrees C and 27 degrees C and 100% r.h. The developmental capability of the eggs at low or freezing temperatures persisted up to 3 weeks at -10 degrees C and up to 8 weeks at 5 degrees C. The 50% mortality period of unfed larvae and nymphs increased with rising humidity and was longest at 5 degrees C and 100% r.h., amounting to 83.5 days for larvae and 108 days for nymphs. Engorged larvae and nymphs only moulted in the temperature range of 10-27 degrees C. The percent moulting success was low at 10 degrees C and increased with rising ambient humidity at 20 degrees C and 27 degrees C reaching more than 90% at 100% r.h. After incubation at low or freezing temperatures and subsequent transfer to 20 degrees C and 100% r.h. engorged larvae did not moult after exposure to -10 degrees C, but they tolerated 0 degrees C and 5 degrees C up to 3 and 10 weeks, respectively, and developed into nymphs. Engorged nymphs moulted into adults even after preceding incubation at -10 degrees C, their metamorphosis capability persisted for a maximum of 4 and 17 weeks at 0 degrees C and 5 degrees C, respectively.

Animals↗
PubMed1999

Food intake in blattella germanica (L.) nymphs affects hydrocarbon synthesis and its allocation in adults between epicuticle and reproduction

The causal relationship between food intake and hydrocarbon synthesis was examined in vivo and in vitro. Fed Blattella germanica (L.) nymphs synthesized hydrocarbons in a stage-specific manner, with high rates occurring in the first 6 days of a 13-day last stadium, in relation to feeding. A similar pattern was exhibited in vitro by sternites and tergites from fed nymphs. In contrast, starved nymphs synthesized hydrocarbons at normal rates for the first 2 days, but then synthesis declined and ceased by day 6. Their abdominal sternites and tergites displayed a similar biosynthetic pattern in vitro, showing that starved tissues lost the capacity to synthesize hydrocarbons, even when provided appropriate nutrients. Synthesis resumed within 2 days of being fed on day 6, reaching a maximum rate 6 days later. Some hydrocarbon appeared on the nymphal cuticle, but almost 4-fold more hydrocarbon was internal in hemolymph lipophorin, fat body, and the developing imaginal cuticle. Because most hydrocarbon synthesized in nymphs provisions the adult, and synthesis is related to food intake, we examined trade-offs in allocations in food-limited insects. Nymphs provided with insufficient quantities of food allocated normal amounts of hydrocarbons to the nymphal epicuticle, but molted into smaller adults with significantly less internal hydrocarbons. These cockroaches directed nearly normal amounts of hydrocarbons to their epicuticle, oocytes, and oothecae, at the cost of internal hydrocarbon reserves for repair and subsequent gonotrophic cycles. Hydrocarbons, thus, appear to serve an important cross-stadial resource and the object of competition among several nymphal and adult tissues. Arch. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗
PubMed2001

Physiological and behavioral responses of stonefly nymphs to enhanced limestone treatment of acid mine drainage.

A new acid mine drainage (AMD) treatment system uses pulsed, fluidized beds of limestone, and carbon dioxide pretreatment of influent AMD, to enhance limestone neutralization of AMD. We conducted laboratory studies to evaluate the behavior and physiology of larval stoneflies (Pteronarcys proteus, Plecoptera) exposed to effluents produced by the treatment system. Survival, sodium balance, drift, and feeding responses by P. proteus to treated and untreated AMD were examined. P. proteus nymphs exhibited significant losses of whole body sodium in exposures to untreated AMD. Nymphs exposed to treated effluents experienced no loss of whole-body sodium. Nymphs exposed to untreated AMD showed elevated drift rates and depressed feeding rates relative to those of nymphs exposed to treated AMD, and to AMD-free controls. No significant differences in feeding or drift behavior occurred between nymphs exposed to treated effluents and those exposed to AMD-free controls. The treatment system, with and without CO2 pretreatment, provided water that was not toxic to the test animals, and that allowed normal behavioral and physiological function.

Acids↗