Sperm precedence in the deer tick Ixodes dammini

ABSTRACT We determined whether female deer ticks Ixodes dammini Spielman, Clifford, Piesman & Corwin (Acari: Ixodidae) can be inseminated repeatedly and whether sperm from first or second matings take precedence in fertilizing eggs. Such information is essential to the design of attempts to reduce the fertility of these vectors of Lyme disease. Although spermatophores are present in about half of questing female ticks, they are present in virtually all those found on deer; the abundance of males on deer exceeds that of females and copulation is common. Females must be inseminated before commencing the rapid engorgement phase of feeding. Males need not be in attendance during feeding, provided that the female has been inseminated preprandially. Thus, preprandial insemination suffices to stimulate rapid engorgement, but less blood is taken than when the female is perprandially inseminated. Both types of insemination effectively fertilize eggs. Eggs from females sequentially inseminated by irradiated and non irradiated males, were fertilized mainly by sperm from the last male. Cobalt-irradiated males mate effectively and their sperm compete with those of non-irradiated males. Sperm from the second two sequential inseminations fertilize most of the eggs. By infesting deer with such irradiated male I.dammini , the abundance of these vector ticks may effectively be reduced.     

Effect of deer reduction on abundance of the deer tick (Ixodes dammini)

To evaluate the role of deer in regulating the abundance of the deer tick (Ixodes dammini) we attempted to treat with acaricide, but eventually removed, about 70 percent of deer from Great Island, Cape Cod, Massachusetts. Deer were captured in box traps, a corral, an entanglement net, and with rifle-fired tranquilizer. Failure of these attempts, combined with ineffective acaricides, led us to deer destruction begun in fall 1982. Larval tick abundance on mice was monitored before and after deer removal. We concluded that deer removal, to the extent accomplished, did not markedly reduce the abundance of the tick. Reduced abundance of deer may not result in reduced abundance of immature ticks if deer removal follows the period of adult tick feeding, or if intensity of infestation per deer increases, or if other mammals substitute as suitable hosts. Reduced tick abundance may be delayed if unattached immature ticks survive more than one year.     

Ultrastructure of spirochetes isolated from Ixodes ricinus and Ixodes dammini

Two strains of Ixodes spirochetes, one isolated in the United States (B31) and the other in Sweden (G25), were examined by electron microscopy. Cells of strain G25 were 11-25 micron long with a wavelength of 2.1-2.4 micron and an amplitude of 0.4 micron. Eleven flagella were inserted subterminally at each end of the cell. Cells of strain B31 were similar but had eleven or seven flagella. Cytoplasmic tubules were not seen in cells of either strain. Although not identical, both strains showed ultrastructural details characteristic of the genus Borrelia.     

Ixodes dammini: salivary anti-complement activity

Saliva of the tick Ixodes dammini prevents hemolysis of rabbit erythrocytes by the human alternative pathway of complement. Deposition of C3b to activating surfaces and concomitant C3a release are inhibited. C3b deposition to activating surfaces is inhibited regardless the origin (humans, rat, mouse, guinea pig, and hamster) of the serum. The inhibitor elutes as a single peak upon gel filtration, with an apparent molecular weight of 49,000. Salivary anti-complement may contribute to successful feeding of I. dammini in their natural hosts.     

Ixodes dammini: salivary anaphylatoxin inactivating activity

Saliva of the tick, Ixodes dammini, antagonizes anaphylatoxin, abolishing both the effects of anaphylatoxin on guinea pig ileum preparations regularly stimulated with histamine and the local edema caused by intradermal injection of anaphylatoxin into guinea pigs. Saliva of these ticks, however, did not modify polymorphonuclear leukocyte aggregation induced by anaphylatoxin. Bradykinin and lysil-bradykinin were inactivated, but angiotensin I, angiotensin II, and substance P were not affected. Amino acids were released rapidly following incubation of saliva with bradykinin, but slowly from des-arg-9-bradykinin. These results suggest the presence of a salivary carboxypeptidase with specificity for terminal basic amino acids. Such activity may inactivate anaphylatoxin and bradykinin at the site of tick attachment.     

A comparison of methods for sampling the deer tick,Ixodes dammini,in a Lyme disease endemic area

The purpose of this study was to compare the trapping and examining of mice, drag sampling, and CO₂-baited traps for their ability to detect the presence and abundance of immature deer ticks,Ixodes dammini, in a Lyme disease endemic area in southern New York State. Eight study sites were sampled 14 times between 28 May and 31 August by setting 49 live-traps, four CO₂-baited traps, and drag sampling 500 m². A total of 1540 nymphs and 3079 larvae was collected during the study. Drag sampling collected the most nymphs (705), while more larvae were recovered from CO₂-baited traps (1105). Comparisons among the methods showed a significant difference in the numbers of both larval and nymphal ticks collected (P<0.01). There was a positive correlation between the numbers of nymphs collected by drag sampling and CO₂-baited tick traps (r _s=0.83,P<0.05), and between the numbers of larvae collected by drag sampling and mouse trapping (r _s=0.75,P<0.05). These results suggest that drag sampling would be the single most reliable method for quantitatively sampling immatureI. dammini populations in a Lyme disease endemic area.     

A microfilaria of exceptional size from the ixodid tick, Ixodes dammini, from Shelter Island, New York

Thirty or more microfilariae 0.70-1.32 mm in length were recovered from the hemocele of an unengorged adult tick, Ixodes dammini, that was collected from vegetation on Shelter Island, New York. Among approximately 500 I. dammini collected from the same area only 1 other was similarly infected. Outstanding features, in addition to size, were absence of a cephalic space and the presence of nuclei in 2 or 3 irregular rows extending to the end of a bluntly rounded tail. The microfilariae apparently were ingested in a blood meal that was taken when the ticks were larvae or nymphs, and had persisted alive without development.     

Ixodes dammini: evidence for salivary prostacyclin secretion

Pilocarpine-induced saliva of adult Ixodes dammini ticks contained abundant amounts (523 +/- 140 ng/ml, mean +/- SE, n = 14) of 6-keto-PGF1 alpha, the stable degradation product of prostacyclin. This prostaglandin was identified by radioimmunoassay and reversed-phase chromatography. This activity may help tick feeding by preventing host hemostatic reactions, by increasing host blood flow at the tick feeding site, and by preventing leukocyte degranulation.     

Nymphal Ixodes dammini: models of the temporal abundance patterns.

A difference equation model was developed to explore the sensitivity of the temporal pattern of relative abundance of active, host-seeking nymphal Ixodes dammini. Inputs to the model were the temporal patterns of recruitment of nymphs into the active class, mortality and successful acquisition of hosts by the ticks. Input parameters were varied both in the temporal pattern (shape) and in the cumulative level (summed over the period of activity). The output of the models, the temporal abundance pattern, was examined for (1) overall shape and (2) the timing of the peak abundance of host-seeking nymphs. The shape of the temporal pattern of nymphal abundance was not sensitive to changes in the shape of the functions used as input for host-finding. The time of peak abundance of nymphs is slightly sensitive to changes in the overall level of host-finding and mortality. When more ticks are removed from the active class (host-finding or mortality increasing), the time of the peak abundance of the nymphs shifts earlier. However, this shift is small compared to variation in field data. The general shape of the activity pattern was sensitive to changes in the temporal pattern of recruitment. A left-skewed distribution produced output which most resembles field data. The temporal pattern of nymphs entering the active class is important, and is an area which needs further empirical work.     

Bacteriophage in the Ixodes dammini spirochete, etiological agent of Lyme disease

A bacteriophage with a B-3 morphology was detected by electron microscopy in a spirochete isolated from the tick Ixodes dammini. It has a 40- to 50-nm elongated head and a tail 50 to 70 nm in length. It appears devoid of collars or kite-tail structure. The spirochete has been identified as the causative agent of Lyme disease.     

The midgut hemolysin of Ixodes dammini (Acari:Ixodidae)

Midgut homogenates of the hard tick, Ixodes dammini, lyse erythrocytes from rabbits, rats, hamsters, and guinea pigs. The activity displays sigmoidal kinetics, has an alkaline pH optimum, and is activated by temperature. Hemolytic activity is lost when homogenates are incubated with trypsin or heated for 1 hr at 60 C. Activity is not detectable in nonfed ticks as well as ticks attached for up to 2 days to a host, but increases during the growth phase of feeding. Such activity is postulated to help the initial process of the blood meal digestion by releasing the contents of erythrocytes for further enzymatic hydrolysis.     

Amblyomma americanum: identification of tick salivary gland antigens from unfed and early feeding females with comparisons to Ixodes dammini and Dermacentor variabilis

Salivary gland antigens involved in host resistance to tick feeding by Amblyomma americanum (lone star tick) have been identified. Gland extracts from unfed and partially fed 12-, 48-, 72-, 96-, and 120-hr females and their corresponding midgut tissues were analyzed by immunoblotting with sera from naturally immune and hyperimmune sheep and rabbits. Polypeptides at 90, 75, 58, 45, 33, and 23 kDa from the salivary glands of A. americanum females were consistently observed with antibodies from both sheep and rabbits. No antigens unique to tick midgut tissue were detected with immune sera. Female Dermacentor variabilis and Ixodes dammini shared 90- and 45-kDa salivary gland antigens with A. americanum, and these may represent conserved polypeptides. We speculate that some of the salivary gland antigens represent components of tick cement, while others are playing some other yet undetermined role in tick feeding.     

Longitudinal surveillance of the tick Ixodes ricinus for borreliae

Host-seeking Ixodes ricinus (L.) (Acari: Ixodidae) were monitored for borreliae (Borrelia burgdorferi s.l.) using dark-field microscopy in South Moravia (Czech Republic) each May from 1991 to 2001 (150 nymphs, 100 females and 100 males each year). This survey revealed a mean annual percentage of infected ticks of 16.8% (range, 11.7-24.2) in nymphs, 24.9% (range, 16.5-33.6) in females and 26.1% (range, 17.1-37.3) in males. Annual incidence of Lyme borreliosis in humans of the area in the same period (range, 8.7-41.7 per 100,000) correlated significantly with the frequency (number of ticks per flag per hour) of nymphs infected with >50 borreliae or all nymphal ticks, but not with the frequency of females, infected females or the infection rate (% of ticks infected) of either nymphal or female ticks. A prediction of the annual incidence of Lyme borreliosis, based on the frequency of heavily infected or all nymphal I. ricinus ticks, is feasible. The infection rate in I. ricinus correlated significantly with the North Atlantic Oscillation winter index of the last year (in nymphs) or of the year before last (in adults).     

Babesia microti: prolonged survival of salavarian piroplasms in nymphal Ixodes dammini

We determined how long Babesia microti survive in the salivary glands of nymphal Ixodes dammini. Of those ticks held at 21 C, the proportion with demonstrable piroplasms decreased from 95%, prior to 20 weeks post-larval-feeding (p-l-f), to less than 80% at 42 weeks p-l-f. Similarly, the number of infected acini decreased significantly. Nymphal I. dammini were kept alive for as long as 1 year, by transferring them to 4 C, at 20 weeks p-l-f. The proportion of infected ticks at 52 weeks p-l-f was less than half of the proportion of infected nymphs examined prior to 20 weeks p-l-f, and only 1/6 as many acini were infected. Ultrastructural observations of salivary glands from ticks at 44 weeks p-l-f revealed that B. microti parasites in older ticks remain in the sporoblast meshwork phase; such parasites rarely differentiated into sporozoites. Degenerating parasites containing autophagic vacuoles were also observed in older ticks.     

Actin S-nitrosylation inhibits neutrophil beta2 integrin function

The focus of this work was to elucidate the mechanism for inhibition of neutrophil beta(2) integrin adhesion molecules by hyperoxia. Results demonstrate that exposure to high oxygen partial pressures increases synthesis of reactive species derived from type 2 nitric-oxide synthase and myeloperoxidase, leading to excessive S-nitrosylation of beta-actin and possibly profilin. Hyperoxia causes S-nitrosylation of the four cysteine moieties closest to the carboxyl-terminal end of actin, which results in formation of short actin filaments. This alters actin polymerization, network formation, and intracellular distribution, as well as inhibits beta(2) integrin clustering. If neutrophils are exposed to ultraviolet light to reverse S-nitrosylation, or are incubated with N-formyl-methionyl-leucine-phenylalanine to trigger "inside-out" activation, the effects of hyperoxia are reversed. We conclude that cytoskeletal changes triggered by hyperoxia inhibit beta(2) integrin-dependent neutrophil adhesion.