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PubMedDate not supplied

Susceptibility of immature Ixodes scapularis (Acari: Ixodidae) to desiccants and an insecticidal soap.

Efficacy of commercially available formulations of desiccants (Drione, Dri-die, diatomaceous earth) and insecticidal soap (Safer's) comprised of active ingredients were evaluated against Ixodes scapularis Say immatures in petri dish and grass turf bioassays. In petri dish bioassays at label rate, all products, except diatomaceous earth, provided a high degree of control by 24 and 48 h (71-100% mortality). Mortality of larvae exceeded 94% by 4 h after treatment with Drione (10 x label rate held at 85% RH), Dri-die (label rate held at both 85% and 98% RH) and Safer's insecticidal soap (10 x label rate held at 98% RH). Nymphal mortality was highest by 4 h after treatment with Safer's insecticidal soap (up to 96%). Larvae were more susceptible than nymphs to desiccants, however, nymphs were more susceptible than larvae to Safer's insecticidal soap. Immature ticks treated with Safer's insecticidal soap exhibited sublethal effects with significantly decreased attachment to hosts and no engorgement. In grass turf bioassays, mortality of nymphs was equivalent (85-95%) between treatments of chlorpyrifos (0.6 kg [AI]/ha, Safer's insecticidal soap, and Drione. In the same bioassays, nymphal mortality was moderate after treatment with Dri-die (23-29%) and low following application with diatomaceous earth (16%) and for untreated controls (6%).

Animals↗
PubMedDate not supplied

The effects of tick numbers and intervals between infestations on the resistance acquired by guinea-pigs to adults of Rhipicephalus evertsi evertsi (Acari: Ixodidae).

Guinea-pigs were infested three times at short (1 week) intervals or long (10 week) intervals between successive infestations with low (1), medium (8) and high (15) numbers of adult Rhipicephalus evertsi evertsi. To compare the resistance developed by the hosts at short and long intervals between infestations, a challenge (fourth) infestation was performed with the high number of ticks. Resistance was assessed by comparing the mean weight of engorged female ticks that dropped from the hosts. Concentrations of beta globulins in the host sera were also monitored. Different tick loads (low, medium and high) and infestation intervals had a similar influence on the reduction in weight of the females which was between 60-70% after the final challenge. However, the concentration of beta globulins, was highest in the guinea-pigs exposed to medium and high numbers of ticks with long infestation intervals, probably because of an increase in the production of protective antibodies in response to more intensive antigenic challenge. The relationship between engorgement weight and beta globulin levels in host sera is discussed.

Animals↗
PubMed1996

Field and laboratory studies on the timing of oviposition and hatching of the western black-legged tick, Ixodes pacificus (Acari: Ixodidae).

The timing of oviposition and hatching of Ixodes pacificus was investigated in the field and at constant temperatures in the laboratory. Replete females held at temperatures between 9 and 29 degrees C began depositing eggs a mean of 9-70 days after drop off. Egg masses held between 12 and 25 degrees C commenced hatching 25-178 days after the onset of oviposition. Eggs held at 9 or 29 degrees C did not hatch. The lower temperature thresholds for development (LTD) for oviposition and hatching were 6.5 and 9 degrees C, respectively. The number of degree days required for oviposition and hatching was 173 and 588, respectively. Replete females placed in the field on 2 December through to 8 March deposited eggs from 2 February through to 24 April; the eggs commenced hatching between 2 July and 21 August. Unfed larvae from two of 20 egg masses survived through the winter and fed readily when exposed to deer mice (Peromyscus maniculatus) on 22 April. Replete larvae were returned to the field and moulted between 9 and 21 August. Larvae exposed to deer mice in August, 4 weeks after hatching, also fed readily. Although further studies are needed to clarify the timing of nymphal development, the present study suggests that I. pacificus requires more than 1 year to complete its life cycle.

Animals↗
PubMed1993

Relative utilization of reptiles and rodents as hosts by immature Ixodes scapularis (Acari: Ixodidae) in the coastal plain of North Carolina, USA.

The interaction of immature black-legged ticks, Ixodes scapularis, with reptiles and rodents was investigated in various woodland habitats in the coastal plain of North Carolina. Reptiles were sampled from April 1 to September 30, 1991. No ticks were found on 95 specimens representing 16 species of snakes. Ticks were found on 54 (36.7%) of 147 lizards. I. scapularis was the only tick recovered from lizards. Some lizards were collected in drift fence traps each month of the study except August. Capture rates averaged one lizard per 16 trap-days. Larvae and nymphs of I. scapularis were removed from the southeastern five-lined skink (Eumeces inexpectatus), the ground skink (Scincella lateralis), the broad-headed skink (E. laticeps) and the eastern glass lizard (Ophisaurus ventralis), but ticks were not found on three other lizard species. Tick infestation rates and loads for parasitized species are presented. Ticks were almost exclusively attached at the base or in the axils of forelimbs of skinks and in the lateral grooves of eastern glass lizards. Rodents were live-trapped at sites where lizards were sampled and at other sites from 1 July, 1990 to 30 January, 1992. Capture rates averaged one rodent per 47 trap-nights. Ticks were found on 23 (17.8%) of 129 animals inspected. Five species of rodents were examined but only four species were found to be tick-infested. In contrast to lizards, few I. scapularis were collected. Rodents, principally the white-footed mouse (Peromyscus leucopus) and cotton mouse (P. gossypinus) were most frequently infested with immature American dog ticks, Dermacentor variabilis, during winter and early spring months. Burdens of D. variabilis on these rodents averaged 0.3 ticks per rodent. Effects of the diversion of ticks from feeding on Peromyscus mice on the transmission of the Lyme disease spirochete are discussed.

Animals↗
PubMed1995

Differences in Borrelia infections in adult Ixodes persulcatus and Ixodes ricinus ticks (Acari: Ixodidae) in populations of north-western Russia.

Dark-field microscopy was used to determine the number of Borrelia spirochetes in 630 standard preparations obtained from adult ixodid ticks (344 Ixodes persulcatus and 286 I. ricinus) collected in 1989-92 in the Leningrad region of Russia. The average numbers of Borrelia in I. persulcatus and I. ricinus preparations were 34.7 and 23.3 per 100 microscopic fields, respectively. The maximal individual values registered each year for ticks of both species were several hundred times greater than the minimal values. Ticks carrying relatively small numbers of Borrelia generally predominated. Proportions of more heavily infected ticks varied considerably from year to year. These parameters were significantly higher in foci with predominance of I. persulcatus ticks. As a consequence, risk to acquire Lyme borreliosis in such foci is considered greater than in foci where I. ricinus predominates.

Animals↗
PubMed1995

Hyalomma truncatum (Acari; Ixodidae): investigations into the scototaxis of unfed adult ticks.

Under controlled test conditions, unfed male and female Hyalomma truncatum ticks exhibited a positive scototaxis to stationary, two-dimensional targets. Upright-positioned rectangles were the most attractive targets. The attractiveness of these targets increased with their size. Significantly more ticks responded scototactically positively to the targets under a luminance contrast ratio of 5:1, as compared with other luminance contrast ratios. Targets with an elevation angle of 13 degrees were occupied more frequently than objects with higher elevation angles. Scototaxis was the same towards a stationary and a sinusoid oscillating target. When an upright-positioned rectangle was combined with a CO2 gradient, the number of ticks that migrated into the CO2 gradient and contacted the target did not increase significantly. The interval between exposure and first locomotion of the ticks, however, was significantly shorter under the influence of a CO2 gradient than in all other experiments without a CO2 gradient. A temperature gradient simulating a natural host (cattle) did not alter the scototaxis. The results of these investigations suggest that the positive scototaxis exhibited by adult H. truncatum ticks is not likely to be part of their appetence behaviour but rather searching behaviour to find adequate protection from harsh climatic conditions.

Animals↗
PubMed1995

Cutaneous hypersensitivity induced in dogs and guinea-pigs by extracts of the tick Rhipicephalus sanguineus (Acari: Ixodidae).

The cutaneous hypersensitivity induced by Rhipicephalus sanguineus tick extract in dogs (natural host) and guinea-pigs (laboratory host) was evaluated. The left ear of infested and control (tick-bite naive) dogs and guinea-pigs was injected intradermally with an extract from unfed adult ticks and the right ear with phosphate buffered saline (PBS). Ear thickness variations were then measured after 10 min and 1, 2, 6, 18, 24, 48, 72 and 96 h post-injection. Results were expressed as percentual changes in the ear thickness in relation to pre-inoculation values. The final variation in ear thickness induced by the extract was given by subtracting, in each animal, the right ear percentual increase from that of the left ear. Guinea-pigs were tested at two different times following infestation and with two different doses of extract. Infested guinea-pigs from the three experiments developed an immediate (within the first 2 h post-inoculation) and a strong delayed reaction (24 h) to the extract. Dogs, unlike guinea-pigs, developed only a strong immediate reaction whereby an 80% increase in ear thickness was observed. Control animals, with the exception of one dog, did not develop any significant reaction to the extract. Only mild reactions were induced by PBS in the right ear of all animals. The correlation between the absence of a strong delayed type reaction to tick extract and the lack of resistance of the natural host to R. sanguineus tick is discussed.

Animals↗
PubMed1995

Improvement of field sampling methods for adult Karoo paralysis ticks, Ixodes rubicundus (Acari: Ixodidae), through addition of host odour.

The responsiveness of Ixodes rubicundus ticks on questing substrates and the success of their attachment to non-living substrates were investigated. The purpose of this study was to relate responsiveness to conditions of temperature and humidity, to compare the efficacy of flagging and dragging methods to estimate the size of populations of adult I. rubicundus in the field, and to determine the possible influence of host odour on the efficacy of these methods. Responsiveness was tested under varying conditions of temperature and humidity under field conditions, and the same ticks were used to determine the duration of attachment to a flannel cloth, either impregnated with host odour from sheep wool or without it. Flagging and dragging methods were compared under laboratory conditions with cloths either treated with host odour or not. Within the range of ambient temperatures recorded during this study (7-25 degrees C) most of the ticks (86%) were responsive. No obvious relationship between temperature, relative humidity and responsiveness of ticks was evident. Ticks remained on average 32.9 seconds (n = 64) on cloth treated with host odour compared to 9.1 seconds (n = 54) on untreated cloth. Flagging was 1.5-1.7 times as effective as dragging and treatment of the cloths with host odour increased the efficacy 2.4 (dragging) to 2.8 (flagging) times. The reactions of ticks to external stimuli should, therefore, be taken into account to maximize field sampling success.

Animals↗
PubMed1995

Distribution of Dermatophagoides mite (Acari: Pyroglyphidae) antigens in homes of allergic patients in Japan.

Dust samples collected in 61 homes of patients with mite allergies and 11 homes of non-allergic people as controls were examined for antigen levels of Dermatophagoides farinae Hughes and Dermatophagoides pteronyssinus (Trouessart) to reveal the current distribution of allergenic mites in homes in Japan. Patient homes had higher antigen levels than control homes in comforters and pillows but not in futons, carpets, tatamis and wooden floors. Samples with antigen levels of > or = 10 micrograms m-2 were more frequent in and around summer (approximately April-October) than other seasons of the year in most materials and the differences between patient and control homes in comforters and pillows observed in yearly totals was also observed during this period. Wooden structures showed higher antigen levels than concrete structures in comforters, futons, pillows, carpets and tatamis in patient homes. Mite contamination in patient homes in relation to environmental factors was discussed.

Adult↗
PubMed1996

Isolation and characterization of an anticoagulant from the salivary glands of the tick, Ornithodoros savignyi (Acari: Argasidae).

An inhibitor of activated coagulation factor X (fXa) was isolated from salivary gland extracts prepared from Ornithodoros savignyi using a two-step procedure, involving reversed-phase high-performance liquid chromatography (RP-HPLC) and diethylaminoethyl (DEAE) ion-exchange chromatography. From its behaviour during DEAE chromatography it could be deduced that it possesses an acidic pI (approximately 4.6). Capillary zone electrophoresis (CZE) of the purified inhibitor showed it to be homogeneous. The molecular mass was determined as 12 kDa using capillary gel electrophoresis (CGE) and as 7183.4 using laser desorption mass spectrometry (LDMS). The N-terminal amino acid sequence (residues 1-12) was determined and found to share a 66% identity with tick anticoagulant peptide (TAP). The O. savignyi peptide is a slow, tight-binding inhibitor of fXa (Ki = 0.83 +/- 0.10 nM). The interaction of the fXa--inhibitor was found to be competitive and dependent on ionic strength. Preliminary investigations show that the inhibitor may be specific for fXa.

Animals↗
PubMed1996

Infestations of the bont tick Amblyomma hebraeum (Acari: Ixodidae) on different breeds of cattle in Zimbabwe.

Infestations of adults and nymphs of Amblyomma hebraeum were counted on Brahman (Br), Brahman x Simmental (BS), Sanga (Sa) and Hereford (He) steers exposed to infested pastures at Mbizi in southern Zimbabwe in 1986-1987. Herefords were always the most heavily infested, while the Sanga tended to carry the fewest ticks with the Brahman and Brahman x Simmental groups being in between. The ratios of the engorged females on the four breeds were 2.3:1.4:1.4:1.0 for He:Br:BS:Sa. The ratios of the standard nymphs were 2.2:1.4:1.7:1.0 for He:Br:BS:Sa. The results confirm earlier observations in Africa and support the view that there are genetic differences between breeds in the expression of resistance to this tick species.

Animals↗
PubMed1995

Densities of Ixodes ricinus ticks (Acari: Ixodidae) on moorland vegetation communities in the UK.

Unfed (questing) Ixodes ricinus ticks were collected by blanket dragging on a monthly basis from heather-dominated, Vaccinium-dominated and bracken-dominated vegetation communities from two different biogeographical regions of the UK (the Quantock Hills in Somerset, south west England and the North York Moors, north east England) throughout the spring and summer months of 1991 and 1992. Eighteen sites were monitored across the two regions and a total of 1920 blanket drags were carried out. Vaccinium sites showed high tick densities at all life stages, as did bracken sites. Significantly lower numbers of larval and nymphal ticks per drag were collected on heather sites than were collected on either Vaccinium (bilberry/whortleberry) or bracken sites, while similar numbers of adult ticks per drag were collected from each of the three vegetation communities. There was no significant difference between the mean numbers of any tick life stage collected on the Quantock Hills and those collected on the North York Moors on these vegetation communities or between the mean numbers of any tick life stage collected in 1991 and those collected in 1992 on these vegetation communities.

Animals↗
PubMed1995

A case of abnormal size in eggs and larvae of the Taiga tick, Ixodes persulcatus (Acari: Ixodidae).

Egg batches laid by females of Ixodes persulcatus (maintained under a photoperiod of L:D 20:4 before feeding) contained eggs of two sizes: numerous normal eggs of 0.578 x 0.421 mm and some giant eggs of 0.776 x 0.515 mm. Giant eggs were 32-34% greater in length and 22-24% greater in width than normal eggs. Females maintained under a short-day photoperiod (L:D 12:12) laid only normal eggs (0.588 x 0.417 mm). There were no differences between these eggs in viability and developmental time, but larvae hatched from giant eggs were larger (length of body 23-28% greater and of gnathosoma 12-15% greater) than larvae from normal eggs. This dimorphism of eggs and larvae was not sex determined, but may be a maternal photoperiodic effect.

Animals↗
PubMed1995

A comparison of Ixodes rubicundus (Acari: Ixodidae) infestations on Friesian and Bonsmara cattle in South Africa.

This study was conducted to compare the relative resistance of crossbred Bos indicus X B. taurus Bonsmara and B. taurus Friesian cattle to Ixodes rubicundus (Karoo paralysis tick) infestations. During periods of peak abundance of the ticks, Friesian oxen harboured almost twice or more than twice as many ticks as either Bonsmara oxen or cows. During periods of low tick abundance tick burdens on both cattle breeds were closely similar. It is envisaged that cattle can play an important role in an integrated control strategy against the Karoo paralysis tick.

Animals↗
PubMed1996

Preliminary studies on the effect of Anaplasma marginale antibodies ingested by Dermacentor andersoni ticks (Acari:Ixodidae) with their blood meal on infections in salivary glands.

The effect of Anaplasma marginale antibodies ingested with the tick blood meal was tested on infected male ticks that were allowed to feed on cattle immunized with the erythrocytic stage of A. marginale. The experiments were done in two trials. Trial 1 was done using splenectomized calves (two calves per treated and control groups) while ticks in trial 2 were fed on intact yearling cattle (four cattle per treated and control groups). The cattle were immunized with purified outer membrane proteins of erythrocyte-derived A. marginale using saponin (trial 1) or monophosphoryl lipid-A-trehalose dicorynomycolate adjuvant (trial 2). The corresponding control cattle received adjuvant only. All cattle were challenged using Dermacentor andersoni males infected as adults that were allowed to feed for 7 days. In trial 1, the ticks were allowed to feed a second time on susceptible calves to test whether exposure of ticks to immunized cattle affected their ability to transmit anaplasmosis. Infections in fed ticks were monitored by determining the infection rates in salivary glands with an A. marginale-specific RNA probe and light microscopy. Vaccine-derived antibodies ingested with the tick blood meal did not appear to affect the development of A. marginale in previously infected ticks. The infection rates in the salivary glands were not significantly different among ticks fed on immunized versus adjuvant control cattle. When the vaccine-exposed ticks in trial 1 were allowed to feed a second time on susceptible calves, the resulting clinical symptoms of anaplasmosis were similar to those of the controls. There was no statistically significant effect of tick exposure to the anti-erythrocytic stage antibody on the development of salivary gland infection or transmission of A. marginale by ticks.

Anaplasma↗
PubMed1996

Sex ratio characteristics in Ixodes rubicundus (Acari:Ixodidae), the Karoo paralysis tick.

The sex ratio is an important parameter which characterizes the state and dynamics of natural populations of animals. Although ixodid ticks are specialized ectoparasites, most species are bisexual and are characterized by a 1:1 sex ratio for their progeny. In natural populations and even in laboratory colonies, biased sex ratios are often observed. Ixodes rubicundus, the Karoo paralysis tick, parasitizes domestic stock and wild ungulates in South Africa. Adults quest from vegetation, can mate off or on the host and males are seldom parasitic. We hypothesized that the sex ratio for I. rubicundus would be 1:1 when observed directly in the progeny but that it would be strongly biased towards females in samples of parasitic adults. The results mostly supported the hypothesis but it was also shown that unexplained and unpredictable variations can occur. On hosts, females dominated strongly, except on adult angora goats where the sex ratio was biased in favour of the males. This disparity may be related to a greater retention of males in the coarse, curly hair of angora goats compared to the other hosts. Monthly variations in the sex ratios of the tick on hosts are believed to be related to the large fluctuations in sex ratios of questing ticks.

Animals↗
PubMed1996

Investigation on the taxonomic status of Steganacarus magnus and Steganacarus anomalus (Acari:Oribatida) using mitochondrial DNA sequences.

To test the previously suggested synonymization of S. anomalus with the older S. magnus, a fragment of the mitochondrial COI gene was amplified via the polymerase chain reaction and sequenced. The sequence variation was examined in a total of 327 base pairs for four steganacarid mite populations, two of which belong to S. anomalus, one to S. magnus and one to S. hirsutus. The sequence variation suggests that S. magnus and S. anomalus are not distinct species and that the population from Fioreta (Siena) is more similar to that from Apulia than to the nearer population from the Apuan Alps. The results show the usefulness of this molecular approach as a tool for determining taxonomic status and for suggesting faunistic movements in the past millions of years.

Amino Acid Sequence↗
PubMed1996

Inheritance of weight in Rhipicephalus appendiculatus ticks (Acari:Ixodidae) in the laboratory.

A selection of the 10% lightest and 10% heaviest males and females of a population of individually weighed Rhipicephalus appendiculatus Neumann adults was made in two experiments. The offspring of homologous pairs were followed until the next adult stage (light x light, control x control and heavy x heavy). The engorged nymphal weights, unfed adult weights, engorged female weights of the parents, egg mass weights, egg weights, larval scutal lengths, engorged larval weights, unfed nymphal weights, engorged nymphal weights and adult weights of the progeny were determined. No significant differences could be demonstrated between the two lines for egg weight, larval scutal length, engorged larval weight and unfed nymphal weight. Significant differences were found between the egg masses, engorged nymphal weights and adult weights of the two lines. The heritability coefficients of body weight determined from adult to adult were 0.14 and 0.10, respectively, during the first and second experiments. Considering females and males separately, the coefficients were 0.10 and 0.18 during the first experiment and 0.12 and 0.09 during the repeat experiment respectively.

Animals↗