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Optimal efficacy of a fungicide preparation, natamycin, in the control of the house-dust mite, Dermatophagoides pteronyssinus.

The efficacy of a fungicidal preparation, natamycin, for the effective control of Dermatophagoides pteronyssinus (Trouessart), was determined at different concentrations on mattress-dust microsites, including ticking. One treatment with the commercially available natamycin concentration (Tymasil) resulted in a 65% reduction of house-dust mite populations within 4 weeks of treatment. The acaricidal control could be proven despite the protective role of mattress fibres such as ticking. However, mite fecundity was much more affected after treatment with twice the commercial concentration, which then assured a long-term control. Concentrations below the commercially available one were not effective. In a maritime climate, six sequential treatments three times a year would be effective for an adequate long-term control because of the high growth of house-dust fungi and the close interaction between the mite and the mould Aspergillus penicilloides.

Animals↗

Evaluation of rapid diagnostic tests for typhoid fever.

Laboratory diagnosis of typhoid fever requires isolation and identification of Salmonella enterica serotype Typhi. In many areas where this disease is endemic, laboratory capability is limited. Recent advances in molecular immunology have led to the identification of sensitive and specific markers for typhoid fever and technology to manufacture practical and inexpensive kits for their rapid detection. We evaluated three commercial kits for serologic diagnosis of typhoid fever. Patients presenting with > or = 4 days of fever were enrolled at two hospitals in Southern Vietnam. Cases were patients with serotype Typhi isolated from blood samples, and controls were patients with other laboratory-confirmed illnesses. Serotype Typhi isolates were confirmed and tested for antimicrobial susceptibility at the Pasteur Institute in Ho Chi Minh City. The Widal test was run at the hospitals and the Pasteur Institute. Sera were shipped frozen to the Centers for Disease Control and Prevention and tested by using Multi-Test Dip-S-Ticks, TyphiDot, and TUBEX to detect immunoglobulin G (IgG), IgG and IgM, and IgM, respectively. Package insert protocol instructions were followed. We enrolled 59 patients and 21 controls. The sensitivity and specificity findings were as follows: 89 and 53% for Multi-Test Dip-S-Ticks, 79 and 89% for TyphiDot, 78 and 89% for TUBEX, and 64 and 76% for Widal testing in hospitals and 61% and 100% for Widal testing at the Pasteur Institute. For all assays, the sensitivity was highest in the second week of illness. The Widal test was insensitive and displayed interoperator variability. Two rapid kits, TyphiDot and TUBEX, demonstrated promising results.

Adolescent↗

Resistance to tick-borne spirochete challenge induced by Borrelia burgdorferi strains that differ in expression of outer surface proteins.

Hamsters were immunized with thimerosal-killed Borrelia burgdorferi 297 or a mutant of 297 (M297) that lacks the 49-kb linear plasmid and expression of outer surface proteins A and B (OspA and OspB). Ixodes scapularis nymphs infected with either the B. burgdorferi sensu stricto strain 297 or JMNT, similar in OspA and OspB but differing in OspC expression, were used to evaluate protection. In a homologous challenge, 24 hamsters were vaccinated, 8 each with 297 or M297 and 8 sham (adjuvant)-vaccinated controls. Hamsters vaccinated with either bacterin were completely protected against a natural tick bite or subcutaneous (s.c.) inoculation of 297. Borreliae were effectively eliminated from 80 to 90% of the 297-infected ticks that fed on four hamsters immunized with the 297 bacterin. Cultures of spirochetes isolated from the ticks that remained infected were infectious and induced joint inflammation in naive hamsters. There was no reduction of strain 297 spirochetes in ticks that fed on four hamsters immunized with M297, but the hamsters were protected. Results with the M297 bacterin indicate that proteins other than OspA or OspB can protect hamsters against a tick challenge without eliminating B. burgdorferi in the tick. In a heterologous challenge, 36 hamsters were vaccinated, 12 with each bacterin and 12 controls. None of the hamsters immunized with either bacterin were protected from a challenge involving JMNT-infected ticks, while two of four were protected against an s.c. challenge. Hamsters challenged s.c. with strain 297 spirochetes were protected. There was partial elimination of JMNT spirochetes in ticks that fed on the group of four hamsters immunized with the 297 bacterin, and infection rates were reduced by 50 to 60%. JMNT spirochetes reisolated from the ticks that fed on 297-vaccinated hamsters also remained infectious for hamsters. In the JMNT-infected ticks that fed on four M297-immunized hamsters, there was no decline in the proportion of infected ticks. Destruction of spirochetes in ticks that fed on the hamsters vaccinated with the 297 bacterin suggests that antibodies to OspA and OspB may have been responsible, since the mutant did not induce this activity.

Animals↗

Linkage and dominance characteristics of genes for resistance to organophosphorus acaricides and allelic inheritance of decreased brain cholinesterase activity in three strains of the cattle tick, Boophilus microplus.

Resistance to the organophosphorus acaricides diazinon, dimethoate and formothion in the Biarra (B), Mackay (M) and Ridgelands (R) strains respectively of the cattle tick B. microplus has been shown previously to be controlled in each strain by a single incompletely dominant autosomal genetic factor. A very similar mode of inheritance of fenthion resistance in strain B has now been demonstrated with no departure in degree of dominance of resistance from the mean value of +0-57 common to these strains exposed to these chemicals. No F1 larval progeny from the following crossings were appreciably more resistant than their parents to these chemicals: R x B--bromophos ethyl and fenthion; B x M--carbaryl, chlorfenvinphos, chlorpyrifos, diazinon, dimethoate, ethion, fenthion and formothion; M x R--chlorfenvinphos, diazinon, dimethoate, ethion, formothion. The field importance of this absence of overdominance is discussed. There were no susceptible double recessive F2 larval progeny of B x M crossings of F2 or F3 larval progeny of R x M crossings when tested against dimethoate to which the three parental types were similarly resistant; 1/16 of the larval progeny would be expected to be completely susceptible if the resistance genes were unlinked. F1 adult progeny of B x M and R x M crossings exhibited the incompletely recessive mutant-type decreased brain acetylcholinesterase (AChE) activity common to strains B, M and R, thus satisfying the test for allelism. No ticks with normal levels of brain AChE were detected in F2 adult progeny of B x M or R x M crossings. This evidence was strongly suggestive of a series of closely linked genes or alleles controlling dimethoate resistance and a series of alleles controlling decreased brain AChE activity in strains B, M and R.

Acetylcholinesterase↗

Adenosine deaminase from camel tick Hyalomma dromedarii: purification and characterization.

Adenosine deaminase is involved in purine metabolism and is a key enzyme for the control of the cellular levels of adenosine. Adenosine deaminase activity showed significant changes during embryogenesis of the camel tick Hyalomma dromedarii. From the elution profile of chromatography on DEAE-sepharose, three forms of enzyme (ADAI, ADAII and ADAIII) were separated. ADAII was purified to homogeneity after chromatography on Sephacryl S-200. The molecular mass of adenosine deaminase ADAII was 42 kDa for the native enzyme and represented a monomer of 42 kDa by SDS-PAGE. The enzyme had a pH optimum at 7.5 and temperature optimum at 40 degrees C with heat stability up to 40 degrees C. ADAII had a K (m) of 0.5 mM adenosine with higher affinity toward deoxyadenosine and adenosine than other purines. Ni(2+), Ba(2+), Zn(2+), Li(2+), Hg(2+) and Mg(2+) partially inhibited the ADAII. Mg(2+) was the strongest inhibitor by 91% of the enzyme's activity.

Adenosine Deaminase↗

[Prevention of cowdriosis and cases of sheep diseases in the Niayes region of Senegal].

Sheep originating from an heartwater-free area were immunized by the infection and treatment method, using long-acting oxytetracycline. The animals were then exposed, together with control sheep to natural infection in an enzootic area. Tick counts were made to monitor the infestation and establish a correlation between infestation by certain tick species, in particular Amblyomma variegatum, and the occurrence of cowdriosis. In some cases of death associated with ehrlichiosis and anaplasmosis in the group immunized against cowdriosis, groups of Cowdria ruminantium were found in smears of the cerebral cortex, which leaves question marks as to the real nature of immunity to cowdriosis. Furthermore, these losses show the necessity of an integrated approach to the control of diseases of livestock in a given area. The presence of Rhipicephalus e. evertsi, formerly absent from this area, was significant in this respect.

Animals↗

Cross-reaction of tick salivary antigens in the Boophilus microplus-cattle system.

Calves were immunized with Boophilus microplus saliva, filtered through Millipore membranes, in Freund's complete adjuvant. Serum samples were tested by passive hemagglutination against Babesia bigemina, Anaplasma marginale, B. microplus larvae extract, Stomoxys calcitrans extract and B. microplus saliva. After immunization, titers to saliva, larval tick-extract and to S. calcitrans were increased. The challenge with live tick larvae enhanced the formation of antibodies against larva extract, fly extract and tick saliva, which supports the idea that under natural controlled conditions this cross-reactivity could occur.

Anaplasma↗

The value of early treatment of deer tick bites for the prevention of Lyme disease.

OBJECTIVE: To determine if the early antibiotic treatment of deer tick bites prevented Lyme disease. DESIGN: Prospective, double-blind, placebo-controlled, antibiotic treatment. SETTING: Private practice in an area endemic for Lyme disease. STUDY PARTICIPANTS: Patients between 3 and 19 years of age who received antibiotic treatment within 3 days following a deer tick bite. INTERVENTIONS: Patients received an antibiotic or placebo and were followed up for stage I and II disease. All patients had blood drawn at the time of presentation and 6 weeks later for immunofluorescent antibodies (IFA). MEASUREMENTS/MAIN RESULTS: One patient in the placebo group developed clinical Lyme disease associated with an IFA titer of 1:32, considered weakly positive. Three other patients in the placebo group developed an IFA titer of 1:32; one had an influenzalike illness and two had no symptoms. None of the study patients developed any neurologic, cardiac, or arthritic symptoms in the 1- to 3-year follow-up. CONCLUSION: Based on the low frequency of illness, the absence of stage II disease, and the inability to establish the efficacy of early antibiotic treatment, we suggest that physicians not routinely use prophylactic antibiotics for deer tick bites.

Adolescent↗

Reduction of Theileria annulata infection in ticks fed on calves immunized with purified larval antigens of Hyalomma anatolicum anatolicum.

Larval antigen of Hyalonmma anatolicum anatolicum, the vector of Theileria annulata, was purified by two-step affinity chromatography using anti-tick gut-specific rabbit IgG and IgG from immunized cattle. The purified antigen showed the presence of a single polypeptide of 37 kDa (GHLAgP) on SDS-PAGE. Two groups (I and II) of naive crossbred calves (Bos taurus x B. indicus) were immunized with I mg of GHLAgP in three divided doses. Immunized calves of group I were also infected with a sublethal dose of T annulata along with a group of non-immunized calves (group III). Animals in groups I, II, III as well a control group (group IV) were challenged with live nymphs of H. a. anatolicum on the 10th day of immunization. There was a significant reduction in the number of emerging adults of 56.9% +/- 1.67%, in calves of group I (p < 0.01) and 63.09% +/- 1.26% in calves of group II (p < 0.001) compared to the controls. The calves of groups I and II showed antibody responses to tick antigen up to day 70 post immunization. Infection with T. annulata was determined in the salivary glands of adult ticks that developed from the nymphs used for challenge infection. In ticks taken from group I calves, there was a 75.0% +/- 0.00% infection compared with only 85.0 +/- 2.88% infection in ticks taken from calves of group III. Using PCR, a lower infection (83.33% +/- 3.33%) was detected in ticks that developed from calves of group I compared with calves from group III (90.00% +/- 2.88%). The ground-up tick supernatants (GUTS) of the ticks taken from calves of group III yielded higher infection rate and exhibited higher infectivity titre in in vitro infection assay of bovine mononuclear cells than the GUTS of the ticks taken from calves of group I. The results suggest a partial reduction in growth rate of T. annulata in ticks feeding on calves immunized with GHLAgP.

Animals↗

Comparison of water, oils and emulsifiable adjuvant oils as formulating agents for Metarhizium anisopliae for use in control of Boophilus microplus.

Studies were conducted to identify oil-based formulating agents (paraffinic oil, palm oil and emulsifiable adjuvant oils (EAOs)) for Metarhizium anisopliae that were superior to water with simple surfactants using a germination test and a bioassay against Boophilus microplus. Germination of conidia in all formulations, except 10% coconut EAO, produced more than 68% germination at 24 h and nearly 100% at 48 h. Coconut oil (average survival time (AST) = 4.6 +/- 0.28 days) and 10% liquid paraffin EAO (AST = 4.4 +/- 0.15 days) enhanced the pathogenicity of M. anisopliae to B. microplus relative to water (AST = 8.4 +/- 0.42 days). M. anisopliae in 10% liquid paraffin EAO was the most effective formulation having a moderately high germination after 24 h and a low AST as well as a high AST in the control. In the second experiment, germination of conidia in 2% liquid paraffin EAO and 2% Cropspray was higher than in 2% Codacide oil at 24 h, however, all treatments reached 100% germination after 48 h. The ASTs of the EAO based M. anisopliae formulations (Average AST = 6.4 +/- 0.54 days) were similar but lower that the ASTs of the controls (Average AST = 9.6 +/- 0.28 days).

Animals↗

Immunisation against Theileria parva in eastern Zambia: influence of maternal antibodies and demonstration of the carrier status.

Immunisation of calves by the infection and treatment method (I & T) has been extensively used in the eastern province of Zambia to control East Coast fever (ECF), a protozoan tick-borne disease. This paper presents the results of a field longitudinal study, which included a total of 148 Angoni calves. After immunisation against ECF, they were monitored for a full rainy season, coinciding with the main peak of activity of the vector of Theileria parva, the tick Rhipicephalus appendiculatus. Dysimmunisation (acute reaction generated by I & T immunisation), seroconversion and mortality are among the parameters recorded. The effect of maternal antibodies on these parameters was analysed and also studied in experimental conditions on two calves. Before immunisation, young calves had a higher seroprevalence than older animals (maternal antibodies) but their post-immunisation seroprevalence was lower. There was no evidence that their immunoprotection was weaker but this indicates that the post-immunisation seroconversion is probably not a reliable tool to monitor the efficacy of calf immunisation. The carrier state of cattle after immunisation was investigated in experimental conditions on three bovines whereas in the field, the infection prevalence in the ticks was estimated using the relation between the tick burden and the T. parva contacts with the calves. The ability of larval and nymphal R. appendiculatus ticks to pick-up T. parva from carriers and to transmit it to naïve animals after moulting was assessed. It was found that both instars are able to transmit clinical and lethal ECF but that the prevalence of T. parva infection in nymphs is much lower than in adults, confirming the primary role of adults in the transmission of ECF in endemic conditions. Similar results were obtained from the field whereby the ECF peak corresponds with the peak of adult R. appendiculatus activity. The infection prevalence in the ticks was however much lower in the field than in experimental conditions indicating that an important proportion of them feed on alternative hosts. Old ticks seemed to have lost part of their infectivity.

Animals↗

Morphoea is neither associated with features of Borrelia burgdorferi infection, nor is this agent detectable in lesional skin by polymerase chain reaction.

BACKGROUND: The aetiology of morphoea is still unknown. Borrelia burgdorferi as a causative agent of morphoea has been discussed since 1985, but the relationship remains uncertain. OBJECTIVES: We aimed to find evidence for infection with B. burgdorferi by combined evaluation of different clinical and laboratory data in a group of 54 patients with morphoea. METHODS: In each patient, an evaluation of the case history was performed with regard to infection with B. burgdorferi, using a standardized questionnaire. Questions focused on previous tick bites and skin changes suspicious for erythema migrans (EM). The case history data of 52 patients were compared with those of 104 matched control subjects and of 25 patients with acrodermatitis chronica atrophicans (ACA). Serological examinations were performed in 53 patients with morphoea. Furthermore, lesional skin was examined for borrelial DNA in 33 patients, using nested polymerase chain reaction (PCR) for the ospA and the borrelial rRNA gene. RESULTS: Results of the questionnaire showed no differences between patients with morphoea and matched controls. In contrast, patients with ACA showed a much higher prevalence of tick bites and skin changes suspicious for EM as compared with patients with morphoea. Serological examination was positive in only one patient with morphoea alone and in two additional patients with coexistent ACA. No borrelial DNA was detected by PCR in lesional skin of 33 patients with morphoea. CONCLUSIONS: No evidence was found for B. burgdorferi infection in patients with morphoea.

Adolescent↗

Successful vaccination for Lyme disease: a novel mechanism?

Borrelia burgdorferi sensu lato is the aetiologic agent of Lyme disease, which is a multi-system disorder resulting from the transmission of organisms from an infected tick. According to the US Centers for Disease Control, the incidence of Lyme disease in the US has increased 25-fold since national surveillance began and the geographical spread of Lyme disease causing spirochetes would indicate that the annual number of cases will continue to rise. Humoral immunity has been shown to play a role in protection and this has spurred efforts towards developing a Lyme disease vaccine. A number of protective immunogens have been characterised to date, but due to the heterogeneity of Lyme disease Borreliae, no single molecule has proven to be completely effective as a vaccinogen. This review will describe the immunogens that have been used to protect against B. burgdorferi infection, with a focus on the inherent challenges involved with providing successful immunity to B. burgdorferi. In addition, the promising aspects and the limitations of each protective immunogen will be discussed.

Animals↗