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PubMed1992

Olfactory responses of adult Amblyomma hebraeum and A. variegatum (Acari: Ixodidae) to attractant chemicals in laboratory tests.

Unfed adults of the African ticks, Amblyomma hebraeum Koch and A. variegatum (Fabricius), important vectors of human and animal diseases, were exposed to volatile compounds in an olfactometer in efforts to identify both tick-produced or synthetic chemicals capable of eliciting an attraction response. A formula, relative efficacy of attraction, was devised for comparison of responses between species and sexes to a particular test stimulus, or within a homogeneous population to different stimuli. Adults of both species responded strongly to known tick-pheromone constituents, nonanoic acid, methyl salicylate, 2.6-dichlorophenol and benzyl alcohol, as well as to a commercially produced antiseptic, TCP (Pfizer), and its major components, chlorinated and iodinated phenols. Benzaldehyde, a proposed tick-pheromone component, and heptadecane, not known from ticks, were markedly attractive to adults of A. hebraeum but not to those of A. variegatum. Males of the former species, but neither conspecific females not either sex of the latter species, responded significantly to salicylaldehyde (known from males of four species of ticks, including A. variegatum). o-nitrophenol, a major component of the aggregation-attachment pheromone of males of both A. variegatum and A hebraeum and a proven long-range attractant for them in the field, was only partially attractive to either species in the olfactometer. Neither species was attracted to 2-methylpropanoic acid, previously identified in volatile effluents form feeding male A. hebraeum. It is concluded that these important disease vectors respond positively to a variety of volatile chemicals, which may conceivably be used to attract them to traps, animals or acaricides in efforts to control ticks or the diseases they transmit.

Animals↗
PubMed1989

Observations on successive infestations of the rabbit host by the ticks Rhipicephalus appendiculatus and R. zambeziensis (Acari: Ixodidae).

Successive infestation of the rabbit host by instars of the brown ear tick Rhipicephalus appendiculatus resulted in a progressive decline in engorgement and egg weights of adult instars and a reduction in percentage recovery of nymphs and larvae. Repetitive infestation with adults and larvae resulted in increased skin hypersensitivity reactions at the attachment site. Successive infestation with R. zambeziensis caused a more significant decline in engorgement and egg weights of adults than for R. appendiculatus. Percentage recoveries of larvae and nymphs were also significantly reduced. A cross-infestation study indicated that R. appendiculatus and R. zambeziensis share antigenic moieties.

Analysis of Variance↗
PubMed1989

Comparison of flagging, walking, trapping, and collecting from hosts as sampling methods for northern deer ticks, Ixodes dammini, and lone-star ticks, Amblyomma americanum (Acari:Ixodidae).

Ticks were sampled by flagging, collecting from the investigator's clothing (walking samples), trapping with dry-ice bait, and collecting from mammal hosts on Fire Island, NY, U.S.A. The habitat distribution of adult deer ticks, Ixodes dammini, was the same in simultaneous collections from the investigator's clothing and from muslin flags. Walking and flagging samples can both be biased by differences between investigators, so the same person should do comparative samples whenever possible. Walking samples probably give a more accurate estimate than flagging samples of the human risk of encountering ticks. However, ticks (such as immature I. dammini) that seek hosts in leaf litter and ground-level vegetation are poorly sampled by walking collections. These ticks can be sampled by flagging at ground level. Dry-ice-baited tick-traps caught far more lone-star ticks, Amblyomma americanum, than deer ticks, even in areas where deer ticks predominated in flagging samples. In comparisons of tick mobility in the lab, nymphal A. americanum were more mobile than nymphal I. dammini in 84% of the trials. Therefore, the trapping bias may result from increased trap encounter due to more rapid movement by A. americanum, although greater attraction to carbon dioxide may also play a role. Tick traps are useful for intraspecific between-habitat comparisons. Early in their seasonal activity period, larval I. dammini were better represented in collections from mouse hosts than in flagging samples. Apparently, sampling from favored hosts can detect ticks at low population levels, but often cannot be used to get accurate estimates of pathogen prevalence in questing ticks.

Animals↗
PubMed1985

Adaptions in the life cycle of Dermacentor variabilis (Say) and Ixodes dammini (Spielman, Clifford, Piesman, and Corwin) marginal populations (Acari: Ixodidae).

Both the Dermacentor variabilis and Ixodes dammini adult diapause seasons are followed by a breeding period. At the edge of the ticks' range, where diapause and breeding occur under adverse climatic conditions, the species still conserves its fixed response for the onset of diapause. As a result, most of the following breeding effort is wasted; the population can only be maintained by an aberrant breeding period during the normal diapause season. When the diapause and breeding periods are suitable for the climate at the edge of the ticks' range, the rate of immature development versus the temperature regime can result in the appearance of the immature stages out of phase with the timing for the optimal life cycle in the marginal climate. The ticks are limited to minor adjustments of their development rates but, if this is all that is required for an optimum life cycle, this response can preadapt the species to the foreign climate.

Animals↗
PubMed1991

Energy budget of the grain mite, Acarus siro (Acari: Acaridae).

Immature individuals of Acarus siro L. ingest a total of 0.1408 J of food energy, 58.5% of which is consumed by the deutonymph, 27.1% by the protonymph and only 14.1% by the larva. The total ingestion is much greater (2.8169 J +/- 0.0981 SE). Much energy, 0.7031 J +/- 0.0231 SE, is used for egg production, which is concentrated in the first 20 days of adult life. Assimilation efficiency during this period varies from 63 to 71%. Most energy ingested between the 20th and 40th days of adult life is used in biomass production, and biomass increases significantly up to the 30th day. Afterwards, old individuals expend a large amount of assimilated energy on respiration due to the increased cost of maintenance.

Animals↗
PubMed1990

Effect of heat treatments on the house-dust mites Dermatophagoides pteronyssinus and D. farinae (Acari: Pyroglyphidae) in a mattress-like polyurethane foam block.

The behaviour and survival of the house-dust mites Dermatophagoides pteronyssinus and D. farinae were studied under laboratory conditions in a mattress-like polyurethane foam block that was heated by an electric blanket. Mites obtained from a laboratory culture were introduced into the foam block which was sliced into seven horizontal layers and covered with an electric blanket. Measurements of temperature and relative humidity were taken between the layers and the number of living mites was established using the heat-escape method.

Animals↗
PubMed1992

Ultrastructure of the reproductive system of the house dust mites Dermatophagoides farinae and D. pteronyssinus (Acari, Pyroglyphidae) with remarks on spermatogenesis and oogenesis.

Several parts of the reproductive system of both sexes of Dermatophagoides farinae and D. pteronyssinus are investigated and compared by light-, scanning electron-, and transmission electron microscopy. New techniques have been employed for scanning of the internal structures of these mites. The male reproductive system consists of unpaired testis, paired vasa deferentia, an accessory gland, ejaculatory duct, and copulatory organ. The female reproductive system consists of bursa copulatrix, ductus bursae, receptaculum seminis, paired ducti receptaculi, ovaries, oviducts, one chorion gland, ovipositor, and oviporus. Testis as well as ovaries are characterized by syncytia of nutritional function. The specifics of spermatogenesis are discussed in connection with sperm transfer. Similarities between the construction of the ovaries and oogenesis in astigmatic mites and telotrophic meroistic ovaries in insects are discussed.

Animals↗
PubMed1992

Effects of precocenes on vitellogenesis in the adult female tick, Ornithodoros moubata (Acari: Argasidae).

Vitellogenin (Vg) concentrations in the hemolymph and ovarian development were studied in Ornithodoros moubata after treatment with precocenes 1 (P1) and 2 (P2). Precocene was dissolved in acetone or DMSO and topically applied to the dorsal surface of ticks: (1) at adult ecdysis; (2) 24 h before engorgement; (3) immediately after engorgement; and (4) 24 h after engorgement. Subsequently, P1 and P2 were dissolved in olive oil and injected through the gonopore into the body cavity 24 h after engorgement. Vitellogenin concentration was measured on days 5 and 10 after engorgement and ovarian development was scored on day 10, 20 or 30. Oviposition was also recorded and the average weight of eggs laid by females was determined. No differences in concentration of Vg in the hemolymph occurred between the control ticks and ticks treated topically or by injection with P1 and P2. Precocene did not suppress the synthesis of Vg in O. moubata. However, oviposition was reduced in ticks that survived repeated treatment with high doses of P2 dissolved in acetone.

Animals↗
PubMed1992

Morphology and structural organization of spiracles in female Argas (Persicargas) walkerae (Acari: Argasidae).

Scanning electron microscopical investigations of fractures and corrosion casts of the spiracles from female A. walkerae ticks revealed a four-part structure, consisting of spiracular plate, ostium and macula forming the external closure, followed by the subostial space and the vestibulum of regulable volume, as well as the atrial chamber as the innermost part from which the main tracheal trunks originate. On the average, the spiracular plate was 158 microns long and 188 microns at the broadest width. It consisted of a thin, highly perforated external and a thick internal layer, which enclosed the interpedicellar space with numerous stout pedicels. In its posterior region, the spiracular plate was covered by the macula, which was up to 80 microns in length and 110 microns in width. The interpedicellar cavity opened into the subostial space measuring 95.5 microns in length and 159.6 microns in width, which proceeded into the 112-microns long vestibulum. The roof of the vestibulum was flexible and could be everted and inverted. Inverted, the roof formed a quadratic bulge with numerous deep cuticular folds, which confined the lumen of the vestibulum either partially or completely. In corrosion casts, the roof was everted to a length of up to 89.3 microns. In the posterior part of the vestibulum, as well as in the initial fourth of the atrial chamber, numerous anvil-, cone- or drop-like cuticular projections were arranged in wedge-like fashion. The atrial chamber was almost spherical with a diameter of 138.4 microns. Five main tracheal trunks of different luminal diameter as well as numerous channels opened into the atrial chamber.

Animals↗
PubMed1991

A review of the biology and allergenicity of the house-dust mite Euroglyphus maynei (Acari: Pyroglyphidae) [corrected].

Euroglyphus maynei is a commonly occurring mite species in house dust throughout the world, but studies of its biology and allergenicity have been relatively scarce because it is difficult to culture, and because species of the genus Dermatophagoides have attracted most attention of research workers. Euroglyphus maynei has been increasingly recognized as an important source of mite-derived allergens to which patients with house-dust mite allergy are exposed. There is a need for knowledge of its biology and allergenicity, in order to be able to grow it in vitro, and to establish whether or not it produces any unique allergens which do not cross-react with those of Dermatophagoides spp. and which may be of clinical significance. This article reviews published and unpublished data on taxonomy and identification, geographical and habitat distribution, seasonal population fluctuations, life-history and the effects of temperature and humidity, culture techniques and allergenicity of E. maynei.

Animals↗
PubMed1985

Studies to evaluate the effectiveness of sex pheromone-impregnated formulations for control of populations of the American dog tick, Dermacentor variabilis (Say) (Acari: Ixodidae).

The sex pheromone, 2,6-dichlorophenol, was combined with a pesticide to control populations of the American dog tick, Dermacentor variabilis (Say). This pheromone persisted in the fur of treated dogs for at least 18 days. The mixture of pheromone and pesticide was much more effective in reducing mating among the surviving ticks than the treatments without pheromone. The pheromone-pesticide mixture also killed significantly more ticks than the treatment without pheromone. This increased effectiveness was due almost entirely to the significantly greater kill of male ticks. Combining the sex pheromone with pesticide treatments offers a means of suppressing tick populations by curtailing their mating and subsequent reproductive success. The potential applications of this technique and the benefits to be expected are discussed.

Animals↗
PubMed1985

Survey for potential soft tick (Acari: Argasidae) vectors of African swine fever on the island of Hispaniola.

A survey of the occurrence of Ornithodoros ticks in animal burrows was conducted in Haiti and the Dominican Republic. Vacuum sampling techniques were used. Four of 8 sample sites in Haiti and 10 of 70 sample sites in the Dominican Republic were positive for O. puertoricensis Fox. Positive sample sites in Haiti were usually near swine. Sites in the Dominican Republic were in drier regions of the country and were not directly associated with previous swine locations. The determination that O. puertoricensis, a potential vector and reservoir of African swine fever (ASF), is present in this region may pose a serious problem for eradication of ASF from the island of Hispaniola.

African Swine Fever↗
PubMed1987

Differences in development time, mortality and water loss between eggs from laboratory and wild populations of Dermatophagoides pteronyssinus (Trouessart, 1897) (Acari: Pyroglyphidae).

A total of four microcultures of adults of Dermatophagoides pteronyssinus, two each from laboratory and wild populations, were fed on separate diets of house dust and yeast granules. A total of 35 eggs of known age from each of the four microcultures were harvested and incubated at 15 degrees C, 60% RH for 16 h/day and 30 degrees C, 75% RH for 8 h/day to simulate diurnal microclimatic fluctuations in a bed. Eggs from females fed on yeast were larger and underwent more rapid rates of water loss, estimated by measurements of reduction in visible surface area (VSA), than eggs from females fed on house dust. There were no significant differences in mean egg development time between the four microcultures (range 6.0-6.88 days). Mortality of the eggs was as follows: from laboratory females fed on yeast, 31.4%; laboratory females fed on house dust, 11.5%; wild females fed on yeast, 2.9%; wild females fed on house dust, 0%. Thus diet and egg size at oviposition had no effect on mortality. Since the microclimates at which eggs from both populations were oviposited and incubated were identical, it is hypothesized that mortality was higher in eggs from laboratory cultures because the mites had become acclimated to the optimal conditions at which they had been kept and were less able to withstand the diurnal fluctuations in microclimate, similar to those imposed upon wild mites in their natural habitats.

Analysis of Variance↗
PubMed1987

Use of Taylor's Power Law in examining the spatial distribution of free-living Boophilus microplus (Acari: Ixodidae) larvae in pastures in Puerto Rico.

Taylor's power law (y = amb) was used to analyze the spatial pattern of Boophilus microplus (Canestrini) larvae in tropical pastures. The index of aggregation b was 2.75 and showed that larvae were highly aggregated. The b-values differed significantly among certain pastures (LSD, P less than 0.05), and pasture type and use could have contributed to differences in b. The use of Taylor's power law to adjust for sampling inconsistencies that occur in tropical pastures where regimented sampling cannot always be followed is discussed.

Animals↗
PubMed1988

Susceptibility of laboratory-reared northern fowl mites, Ornithonyssus sylviarum (Acari: Macronyssidae), to selected acaricides.

Toxicity was determined for 15 acaricides against a laboratory strain of northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago). Adult females were exposed to residues on filter paper for 24 h. Three organophosphorous compounds (monocrotophos, cythioate, and famphur) were more toxic to the northern fowl mite than was carbaryl, the most commonly used pesticide in the poultry industry. The other tested compounds were less toxic to the mite than was carbaryl. Four of these, not used previously for northern fowl mite control, had low LC50's for northern fowl mites:aldicarb (0.46); pirimiphos-methyl (0.73); exo, exo-2,8-dichloro-4-thiatricyclo[3.2.1.0.]octane-4-oxide (AI3-63182) (0.87); and diazinon (2.48).

Animals↗