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A controlled trial of antimicrobial prophylaxis for Lyme disease after deer-tick bites.

BACKGROUND: Borrelia burgdorferi, which causes Lyme disease, is transmitted by deer ticks (lxodes dammini) in the northeastern and midwestern United States. Although deer-tick bites are common in areas in which the disease is endemic, there is uncertainty about how to manage the care of persons who are bitten. METHODS: To assess the risk of infection with B. burgdorferi and the efficacy of prophylactic antimicrobial treatment after a deer-tick bite, we conducted a double-blind, placebo-controlled trial in an area of southeastern Connecticut in which Lyme disease is endemic. Children and adults who had been bitten by deer ticks were randomly assigned to receive either amoxicillin or placebo for 10 days. Subjects were followed for one year for clinical manifestations of Lyme disease. Serum samples obtained at enrollment and six weeks and three months later were tested for antibodies against B. burgdorferi. RESULTS: Of the 387 subjects, 205 (53 percent) were assigned to receive amoxicillin and 182 (47 percent) to receive placebo. Of 344 deer ticks submitted and analyzed by the polymerase chain reaction, 15 percent were infected with B. burgdorferi. Erythema migrans developed in two subjects, both of whom had received placebo. There were no asymptomatic seroconversions and no late manifestations of Lyme disease. The risk of infection with B. burgdorferi in the placebo-treated subjects was 1.2 percent (95 percent confidence interval, 0.1 to 4.1 percent), which was not significantly different (P = 0.22) from the risk in the amoxicillin-treated subjects (0 percent; 95 percent confidence interval, 0 to 1.5 percent). CONCLUSIONS: Even in an area in which Lyme disease is endemic, the risk of infection with B. burgdorferi after a recognized deer-tick bite is so low that prophylactic antimicrobial treatment is not routinely indicated.

Adult↗

Immunization of cattle with synthetic peptides derived from the Boophilus microplus gut protein (Bm86).

Three synthetic peptides (SBm4912, SBm7462 and SBm19733), derived from the Bm86 glycoprotein from Boophilus microplus gut, were constructed and used to immunize cattle from a tick-free area. The immunized animals received three subcutaneous doses of the peptides, with saponin as adjuvant, at 30-day intervals. The immune response was evaluated by IgG elicited against the peptides by the detection of anti-Bm86 specific antibodies in situ and by Western blotting analysis. After tick challenge, reduction in the number, weight and oviposition capacity of engorged females was observed in the tick population that had fed on immunized animals. The results pointed a high efficacy (81.05%) for the SBm7462 synthetic peptide in relation to the others (p<0.01), demonstrating the efficiency of the immune response elicited by synthetic peptides to control the cattle tick B. microplus.

Animals↗

World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) guidelines for evaluating the efficacy of acaricides against ticks (Ixodidae) on ruminants.

These guidelines have been prepared to assist in the planning, conduct and interpretation of studies for the assessment of the efficacy of acaricides (excluding vaccines and other bio-control agents) against single and multi-host ticks (Ixodidae) on ruminants. Information is provided on the selection of animals, dose determination, dose confirmation and field studies, record keeping and result interpretation. The use of pen facilities is advocated for dose determination and confirmation studies for defining therapeutic and persistent efficacy. A minimum of two studies per tick species for which claims are sought is recommended for each dose determination and dose confirmation investigation. If dose confirmation studies demonstrate greater than 95% efficacy the sponsor may proceed to field studies, where a minimum of two studies per geographical location is preferred to confirm the therapeutic and persistent efficacy under field conditions. If dose confirmation studies demonstrate less than 95% efficacy then longer-term field studies can be conducted over two tick seasons with a minimum of two studies per geographical location. These studies can incorporate other control methods such as tick vaccines, to demonstrate stable long-term tick management. Specific advice is also given on conducting studies with paralysis ticks. These guidelines are also intended to assist investigators on how to conduct specific experiments, to provide specific information for registration authorities involved in the decision-making process, to assist in the approval and registration of new acaricides, and to facilitate the worldwide adoption of standard procedures.

Animals↗

Quantification of vitellogenesis and its control by 20-hydroxyecdysone in the ixodid tick, Amblyomma hebraeum.

Ovaries of the ixodid tick, Amblyomma hebraeum Koch, grew rapidly after engorgment as a result of yolk uptake. At 26 degrees C, oviposition began by day 10 post-engorgement, plateaued on days 16-18, and ended by day 38. Vitellin (Vt) was partially purified from ovaries of day 10 engorged ticks by gel filtration and ion exchange chromatography. This Vt comprises seven major and several minor polypeptides. Two polypeptides (211 and 148 kD) from haemolymph of engorged female ticks corresponded to minor polypeptides of similar molecular weight in the ovary. The haemolymph titre of the 211 and 148 kD polypeptides increased up to the onset of oviposition. These polypeptides were absent in males and non-vitellogenic females (day 0 engorged or day 10 partially-fed females), and were thus designated as vitellogenin (Vg). Antibodies raised against haemolymph Vg211 and 148 recognized these polypeptides in partially purified Vt, as well as six of the seven major polypeptides. Using these antibodies we developed an indirect, competitive ELISA to quantify Vg. Rise in haemolymph Vg-concentration lagged slightly behind the rise in haemolymph ecdysteroid (ES)-concentration, and Vg-synthesis was stimulated by injections of 20E into non-vitellogenic females. These observations indicate that an ES is the vitellogenic hormone in A. hebraeum.

Journal Article↗

[In vitro pathogenicity of fungic formulation on nymphs and adults of Rhipicephalus sanguineus (Latreile, 1806) (Acari:Ixodidae)].

Rhipicephalus sanguineus is responsible for transmitting several pathogenic agents, such as: Babesia sp. and Ehrlichia sp.. This species is known as the brown dog tick and has wide geographical distribution. The purpose of this work was to evaluate the pathogenicity of biological formulations of Beauveria bassiana and Metarhizium anisopliae applied to the fed nymphs and adults of R. sanguineus under laboratory conditions. The following treatments were evaluated: control, distilled water with tween 80, emulsible concentrated, cellulose polymerized gel, fungus mixed with emulsible concentrated, fungus mixed with cellulose polymerized gel and fungus mixed with emulsible concentrated and cellulose polymerized gel. Each treatment was repeated ten times. The survival of fed nymphs and unfed adults was evaluated on the 5th, 10th, 15th and the 20th days after treatments. Significant differences were observed between the treatments (p<0.05). The treatment with M. anisopliae mixed with emulsible concentrated and cellulose polymerized gel showed the lower survival on the 15th and 20th days after treatment. We can conclude that the fungi formulation is harmful to fed nymphs and unfed adults of R. sanguineus in vitro, on this account it is suggested its use for the microbial control of this tick.

Animals↗

Control of Boophilus microplus populations in grazing cattle vaccinated with a recombinant Bm86 antigen preparation.

Current methods for the control of cattle tick Boophilus microplus infestations are not effective and the parasite remains a serious problem for the cattle industry in tropical and subtropical areas. Recently, we developed a vaccine against B. microplus employing a recombinant Bm86 (rBm86) antigen preparation (Gavac, Heber Biotec) and it was shown to induce a protective response in vaccinated animals under controlled conditions. Here we show that, under field conditions in grazing cattle, the vaccine is able to control B. microplus populations. Two parasite-free farms were employed for the study. In the first farm, animals were vaccinated with the recombinant vaccine, while, in the second, animals received a saline injection in adjuvant. After immunization, animals were artificially infected and the infestation rate was recorded. Over the 33 weeks of the experiment, the infestation rate was lower in the vaccinated group compared with the control group. At the end of the experiment it was necessary to use chemicals in the control farm after serious losses in production and animals.

Animals↗

Squalene: a naturally abundant mammalian skin secretion and long distance tick-attractant (Acari: Ixodidae).

Squalene is a naturally occurring lipid on mammalian skin and is an attractant to the lone star tick, Amblyomma americanum (L.). In this study, we compared squalene to the standard tick-attractants, benzaldehyde, isobutyric acid, methyl salicylate, nonanoic acid, and o-nitrophenol identified as active ingredients of tick aggregation-attachment pheromones and determined its effectiveness in field and laboratory settings at varying distances. Squalene was detected from 1/4 m greater than the standard tick attractants, attracted a greater percentage of ticks (75 compared with 0-43%) and featured a rapid response time (< 30 min). Thus, squalene contributes more to the tick's ability to locate hosts at greater distances than aggregation-attachment pheromones. These results have important implications for improving tick monitoring and control programs by adding squalene as a supplement to existing attractant baits.

Animals↗

Canine Lyme disease: clinical and serological evaluations in 21 dogs in Japan.

Of 21 dogs from Sapporo, Hokkaido that had been recognised as having been bitten by ticks, 16 were seropositive to Borrelia burgdorferi by ELISA. Thirteen of the seropositive dogs showed signs such as fever, astasia, convulsions, anorexia, fatigue, abnormal gait, nervous signs, diarrhoea, corneal opacity and conjunctivitis. These signs subsided as a result of antibiotic treatment within five days. The plasma concentrations of creatinine in the 21 dogs were higher than in control dogs. Seven ticks that were removed from seven of the dogs were Ixodes persulcatus, and B burgdorferi was isolated from the midgut of two of the ticks.

Animals↗

Percutaneous infection of nymphal Dermacentor andersoni with Anaplasma marginale.

Newly replete nymphal Dermacentor andersoni (principals) were percutaneously exposed to Anaplasma marginale by injection of either intact or lysed infected bovine erythrocytes. Control nymphs were fed on calves with anaplasmosis. The subsequently molted adults were examined for infection by light microscopy, and companion ticks were tested for infectivity by allowing them to feed on susceptible calves. When they fed as adults, both control ticks and percutaneously inoculated principals transmitted A marginale to susceptible calves. Prepatent periods in calves varied according to the method by which nymphs were infected. Colonies of A marginale were found in all ticks that acquired infection by feeding, but colonies were not observed in any ticks exposed percutaneously. The possible developmental cycle of A marginale in artificially infected ticks is discussed.

Anaplasma↗

Artificial feeding and successful reproduction in Ornithodoros moubata moubata (Murray, 1877) (Acarina: Argasidae).

The increasing demand for laboratory-reared argasid and ixodid ticks for research and control purposes makes it necessary to develop effective and standardized tick feeding methods without using live animals as hosts. The in vitro maintenance technique, described in this paper, has been used successfully for rearing Ornithodoros moubata moubata by feeding all nymphal and adult instars through Parafilm 'M' sealing film on heparinized bovine blood (fresh standard). The technique is based on a specially designed tick feeding apparatus with a capacity to feed 2000 first nymphal instars (N 1) or up to 200 adults at one time. For different 1-month-old instars feeding rates were between 80-100%. Using this feeding technique the subsequent egg production of female ticks was remarkably high, producing an average of 210.2 eggs per tick with a hatch rate of 96.72%. There was no overall difference in the reproductive capacity of 1-month-old female O. M. moubata fed on heparinized and haemolyzed bovine blood (kept deep-frozen), heparinized rat blood and defibrinated ovine blood when compared with those fed on heparinized bovine blood (fresh standard).

Animals↗

Efficacy of a collar impregnated with amitraz and pyriproxyfen for prevention of experimental tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs.

OBJECTIVE: To compare the efficacy of collars impregnated with 9% amitraz or 9% amitraz and 0.5% pyriproxyfen (PPF) for control of newly established tick infestations by Rhipicephalus sanguineus, Ixodes ricinus, and Ixodes scapularis in dogs and determine whether egg production by surviving female ticks was decreased. DESIGN: Prospective study. ANIMALS: 72 dogs. PROCEDURE: Dogs were fitted with 1 of 3 test collars impregnated with amitraz, amitraz and PPF, or only excipients (untreated controls). In 3 trials corresponding to each of the 3 tick species, dogs were infested with 150 unfed adult ticks on days 8, 10, 13, and 18. The number of feeding female ticks was recorded on days 10, 13, 18, and 28. Surviving females were weighed and permitted to oviposit under controlled conditions. RESULTS: Collars impregnated with amitraz and PPF decreased tick loads as efficiently as collars containing amitraz alone. Inclusion of PPF into the collar did not significantly decrease the efficacy of amitraz. The few female ticks that survived after feeding on dogs treated with collars containing PPF were unable to oviposit. CONCLUSIONS AND CLINICAL RELEVANCE: Collars impregnated with amitraz were efficient in preventing tick infestations in dogs but did not inhibit oviposition in the few surviving female ticks. Incorporation of PPF into the amitraz-impregnated collar resulted in impairment of the reproductive ability of ticks.

Animals↗

The effect of antigen concentration and vaccine regimen on the immunity induced by membrane antigens from the midgut of Boophilus microplus.

Sheep and cattle were immunized with membrane antigens extracted from the midgut (GM) of the cattle tick Boophilus microplus, and antibody levels were measured by enzyme-linked immunosorbent assay (ELISA). One microgram of GM induced an antibody response in sheep comparable to that induced by 500 micrograms GM. Single or divided doses of 500 micrograms GM induced the same antibody levels in sheep over 12 weeks. Cattle vaccinated with either 500 micrograms GM in two doses or with 50 or 500 micrograms GM in three doses had significant antibody responses (P less than 0.05) and were equally protected (89%, 80% and 95%, respectively, calculated from tick egg weights) against challenge with 40,000 ticks, compared to control cattle. In another experiment, cattle vaccinated with 2.95 mg GM divided into 12 doses over 6 months had antibody levels that reached a plateau after 1.2 mg GM were administered, and were significantly protected (96%) against challenge.

Animals↗