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PubMed1999

Sequence analysis of the knockdown resistance-homologous region of the para-type sodium channel gene from pyrethroid-resistant Boophilus microplus (Acari: Ixodidae).

Using reverse transcription polymerase chain reaction and degenerate oligonucleotide primers, a partial para-homologous sodium channel cDNA was obtained from the southern cattle tick, Boophilus microplus (Canestrini). The cDNA sequence encoded the region in which knockdown resistance (kdr)-type mutations have been identified in numerous insect species. Comparison of deduced amino acids from the cDNA sequence showed high similarity with sodium channels from other species, particularly in highly conserved repeat domains of the sodium channel. Analysis of the kdr-homologous region of the genomic DNA sequences from several susceptible and pyrethroid-resistant tick strains did not detect mutations. The result suggests novel mutations in the sodium channel gene or metabolic detoxification may be involved in the resistance to pyrethroids in this tick.

Amino Acid Sequence↗
PubMed1993

Transmission risk of Lyme disease and implications for tick management.

Transmission risk of Lyme disease at a site can be estimated using the probability of exposure (P1 = probability of being bitten by at least one infected tick); P1 = 1 - (1 - kt)n, where n = number of tick bites per person and kt = spirochete prevalence in questing ticks. This probability is more directly related to the likelihood of acquiring Lyme disease than the standard measure of transmission risk (the number of infected ticks per sample) and allows for direct consideration of the level of tick/human contact (by varying n) in assessing exposure risk and designing management strategies. Projections predict that interventions that lower tick abundance or spirochete prevalence do not necessarily result in equivalent declines in human exposure risk. Management interventions are predicted to have greatest success at lowering disease incidence in humans when tick abundance and/or pathogen prevalence in questing ticks are initially low (e.g., for ticks in residential lawns or for low-prevalence diseases). These techniques are predicted to be less effective at lowering disease incidence in people engaged in high-risk activities at sites with high tick abundance and pathogen prevalence, such as wooded sites in highly endemic areas.

Animals↗
PubMed1996

An assessment of host resistance to ticks on cross-bred cattle in Burundi.

Groups of cattle of four different cross-breeds (Ankole x Friesian, Ankole x Brown-Swiss, Ankole x Guernsey, Ankole x Sahiwal) plus a group of pure Ankole cattle were immunized against tick-borne diseases: East Coast Fever, using a Theileria parva trivalent vaccine, and anaplasmosis, babesiosis and, subsequently, heartwater. With the exception of two small subgroups of Ankole and Ankole x Sahiwal which were treated by weekly spraying using Delnav, all the groups were exposed to natural field challenge of ticks to quantify the development of host resistance to ticks. The results indicate resistance to the most abundant species, Rhipicephalus appendiculatus, as follows: Ankole > Ankole x Sahiwal > Ankole x Brown Swiss > Ankole x Friesian > Ankole x Guernsey. In both Amblyomma variegatum and Rhipicephalus evertsi evertsi, the manifestation of different levels of resistance between breeds is inapparent. Correlations between total ticks and standard female ticks were good for R.appendiculatus (r = 0.73) and R.evertsi (r = 0.51) but poor for A.variegatum (r = 0.31). Correlations between species were reasonably consistent (r = 0.43-0.59). There was no significant correlation between tick burdens and daily liveweight gain (DLWG) over the whole period of the study. Of the cross-bred groups, Ankole x Sahiwal, which had the highest level of resistance, had the highest DLWG. In contrast, the Ankole x Guernsey which developed the lowest level of resistance had only marginally lower DLWG, the difference being only 8 g/day. During the first period of exposure to ticks, however, the untreated Ankole x Sahiwal group had markedly lower DLWG, which may indicate that the development and manifestation of resistance is at the expense of productivity.

Animals↗
PubMed1988

Prospects for suppressing transmission of Lyme disease.

A variety of methods have been developed to prevent human infection by the Lyme disease spirochete in the northeastern United States, mainly based on the observations that nymphal Ixodes dammini serve as vector, that deer serve as hosts for the reproductive stage of this tick, that white-footed mice serve as the reservoir of infection, and that nymphs are most abundant in early summer and must attach for 2 days before infection is transmitted. Methods for personal protection included seasonal avoidance of infested sites, the use of repellants, and prompt removal of attached ticks. Destruction of mouse habitat, but not of mice, was locally effective. Nondestructive acaricidal treatment of deer proved ineffective, but the elimination of these hosts resulted in reduced transmission after several years. Treatment of mice by means of acaricide-impregnated bedding material effectively reduced transmission.

Animals↗
PubMed1996

Potential impact of wildlife on the tropical bont tick eradication program in the Caribbean.

Wildlife are hosts for A. variegatum throughout its range in Africa, and have been demonstrated to serve as hosts for larvae and nymphs on several islands in the Caribbean. Studies conducted in the Caribbean have indicated that most larvae and nymphs and all adults of the tick feed on livestock; therefore, eradication can be approached through the treatment of livestock. However, since small numbers of animals such as the mongoose are infested with larvae and nymphs, these animals may represent a short-term alternative host system. Such infestations potentially could result in a presence of small numbers of ticks for up to 46 months after the onset of a treatment program and could serve as a source to reinfest livestock during the eradication process. Wildlife surveys have been conducted in St. Croix, Puerto Rico, Guadeloupe, and Antigua; but the host status of species present on other islands such as the white-tailed deer on St. Kitts has not been evaluated. As part of the eradication program, the species of wildlife present on each island and the association of these species with infested pastures should be determined. Surveys of wildlife can be used during the eradication to determine if wildlife are serving as an alternative host system. Cattle egrets may serve to disseminate the tick among islands in the region, and to areas outside the region. Cattle egrets have been shown to serve as hosts for the tick, and to move throughout the eastern Caribbean and to North America. The potential for interisland dissemination of ticks by cattle egrets, as well as by other means, substantiates the need for a region-wide eradication program.

Animals↗
PubMed1996

Age and weight relationship in Boophilus microplus (Ixodoidea: Ixodidae) larvae.

The study of the age of free-living stages of ticks is not a frequent subject in acarology research. Baseline knowledge and some possible applications both in research and in tick control are to be considered. Sixty engorged females were incubated at 28 +/- 1 degrees C and 100% relative humidity. Age zero of larvae was established at 10 days after the beginning of eclosion. Larvae were weighted in paper envelopes in groups ranging from 150 to 400 each. Live weight means (LWM) and dry weight means (DWM) were obtained. All larvae have defecated at age zero. Maximum survival was 57 days. Larval age was also expressed as effective temperature summings (ETS). LWM declines slightly with age. DWM has a linear relationship to age from 0 to 504 degrees C-day with a determination coefficient of 0.95. Absolute water content increases from 0 to 504 degrees C-day; further water content diminishes. Dry matter weight declines just to 504 degrees C-day of age. It might be theoretically possible to estimate the age of larvae in pasture by weighing groups of them.

Aging↗
PubMed1998

Successes and failures in the tropical bont tick eradication campaigns in the French antilles.

The Amblyomma variegatum eradication campaigns, based on three phases and a 5-year program, as in other islands of the Caribbean, started in the French Antilles in April 1994 with various financial inputs. The progress of the campaigns in the two islands of Guadeloupe and Martinique contrast sharply. Owing to a shortage and inadequacy of results with regard to the initial objectives, particularly in organization, communication efforts, cattle identification, and application of acaricides on livestock, the European Community which was the most important donor, did not support the Guadeloupean program in 1996 and 1997. This induced a deep crisis in the local sanitary organization, which has the responsibility for the execution of the project, and the almost total interruption of acaricide treatments in Guadeloupe and its dependencies (Marie-Galante, St Martin, Désirade). In Martinique on the contrary, a well-defined organization, communication strategy, and personnel training effort resulted in a generalized census of livestock owners. Identification of cattle increased dramatically in number and the systematic treatment of livestock started in satisfying conditions. It is too early to anticipate on the final result of the campaign, but it is clear that a longer period of time than previously planned, will be necessary to achieve the program. If this prolongation is accepted, it may allow Guadeloupe to take part again in the campaign, a condition absolutely necessary for its regional success.

Animal Husbandry↗
PubMed2002

Eradication of the tropical bont tick in the Caribbean: is the Caribbean amblyomma program in a crisis?

The progress and problems in the Caribbean Amblyomma Program (CAP) are reviewed since its inception in 1995. During 1998, there were funding and administrative management problems. USDA resolved the acute funding crisis, and after three years of negotiation, the CAP has now secured an additional euro 1.5 million from the European Community. Changes in administration in 1998 included the withdrawal of IICA from the program, and the transition during the decentralization of administrative and financial management from FAO headquarters to the Regional Office for Latin America and the Caribbean, based in Chile. A general overview of technical progress and one case study, St. Kitts, is presented. One major concern that emerged during 2000 is that the elimination of the small remaining tropical bont tick (TBT) "hot spots" in both St. Kitts and St. Lucia remained elusive. Why is this so? Egrets? Alternative residual hosts? Or is it fatigue in both technical and administrative management functions? Of even greater concern is the finding of two, apparently new, foci in St. Croix (USVI) in the north and St. Vincent in the south. A critical overview of the program has identified one major remaining constraint-an appropriate management support function at both regional and, in some countries, at the national level. A proposal for a revised management strategy, coupled with the identification of a future strategy to succeed the CAP, namely a Caribbean Animal Resources Management (CARM) Program.

Animals↗
PubMed1988

Isolation and characterization of coumaphos-metabolizing bacteria from cattle dip.

Coumaphos, an organophosphate insecticide, is used for tick control in cattle dipping vats along the U.S.-Mexican border. Recently, several vats (problem vats) have experienced a loss of efficacy because of microbial degradation. Three morphologically distinct bacteria (designated B-1, B-2, and B-3) that metabolized coumaphos were isolated from enrichment cultures that were initiated from problem vat dip material. In general, amino acids, pyrimidines, and acetate supported growth; carbohydrates were not utilized. Only B-2 required growth factors. In resting cell experiments, coumaphos was hydrolyzed to diethylthiophosphoric acid and chlorferon by all three isolates. Chlorferon was subsequently metabolized by B-1 and B-2 to alpha-chloro-beta-methyl-2,3,4-trihydroxy-trans-cinnamic acid. Only B-1 produced additional metabolites. Experiments with [benzo ring-labeled U-C]coumaphos or chlorferon demonstrated that B-1 was capable of both mineralizing and incorporating into biomass the aromatic portion of the molecule. The majority of label, however, was recovered in the form of soluble products, including alpha-chloro-beta-methyl-2,3,4-trihydroxy-trans-cinnamic acid. Although B-1 had the capacity to use chlorferon as a carbon source at low concentrations (100 mug/ml), visible growth at higher concentrations (1,000 mug/ml) was not observed. The addition of 400 mug of chlorferon per ml to B-1 cells in the mid-log phase of growth resulted in complete inhibition of growth, while the addition of 100 to 200 mug of chlorferon per ml resulted in partial inhibition. The growth of B-2 and B-3 was inhibited by 100 mug of chlorferon per ml. These data suggest that, although B-1 and, to a lesser extent, B-2 and B-3 are responsible for the primary degradation of coumaphos, other organisms in the enrichment culture may play a secondary role in coumaphos degradation by removing inhibitory products of coumaphos metabolism.

Journal Article↗
PubMed1998

Geographic risk for lyme disease and human granulocytic ehrlichiosis in southern New York state.

Ixodes scapularis, the tick vector of Lyme disease and human granulocytic ehrlichiosis (HGE), is prevalent in much of southern New York state. The distribution of this species has increased, as have reported cases of both Lyme disease and HGE. The unreliability of case reports, however, demonstrates the need for tick and pathogen surveillance in order to accurately define areas of high risk. In this study, a total of 89,550 m2 at 34 study sites was drag sampled in 1995 and a total of 51,540 m2 at 40 sites was sampled in 1996 to determine tick and pathogen distribution in southern New York state. I. scapularis was collected from 90% of the sites sampled, and regionally, a 2.5-fold increase in nymphal abundance occurred from 1995 to 1996. I. scapularis individuals from all sites were infected with Borrelia burgdorferi in 1995, while an examination of ticks for both B. burgdorferi and the agent of HGE in 1996 confirmed that these organisms were present in all counties; the average coinfection rate was 1.9%. No correlation was found between estimated risk and reported cases of Lyme disease. The geographic disparity of risk observed among sites in this study underscores the need for vector and pathogen surveillance on a regional level. An entomologic risk index can help identify sites for targeted tick control efforts.

Animals↗
PubMed2003

Development of a polyclonal competitive enzyme-linked immunosorbent assay for detection of antibodies to Ehrlichia ruminantium.

A polyclonal competitive enzyme-linked immunosorbent assay (PC-ELISA) is described for detection of antibodies to Ehrlichia (Cowdria) ruminantium by using a soluble extract of endothelial cell culture-derived E. ruminantium as the antigen and biotin-labeled polyclonal goat immunoglobulins as the competitor. For goats, the diagnostic sensitivity and specificity were both 100% with a cutoff of 80% inhibition (80 PI), with detection of antibodies for 550 days postinfection. For cattle, diagnostic sensitivity and specificity were 86 and 100%, respectively, with a cutoff of 50 PI and 79 and 100% with a cutoff of 70 PI. Cross-reactions with high-titer experimental or field antisera to other Ehrlichia and Anaplasma species were observed at up to 68 PI in cattle and up to 85 PI in sheep, and therefore to exclude these cross-reactions, cutoffs of 70 PI for bovine serology and 85 PI for small-ruminant serology were selected. Application of the PC-ELISA to bovine field sera from South Africa gave a higher proportion of positive results than application of the murine macrophage immunofluorescent antibody test or indirect ELISA, suggesting a better sensitivity for detection of recovered cattle, and results with bovine field sera from Malawi were consistent with the observed endemic state of heartwater and the level of tick control practiced at the sample sites. Reproducibility was high, with average standard deviations intraplate of 1.2 PI and interplate of 0.6 PI. The test format is simple, and the test is economical to perform and has a level of sensitivity for detection of low-titer positive bovine sera that may prove to be of value in epidemiological studies on heartwater.

Animals↗
PubMed1987

Clinical trial of halofuginone lactate for the treatment of East Coast fever in Kenya.

A field trial was undertaken to test the efficacy of halofuginone lactate in the treatment of East Coast fever under farming conditions in Kenya. The drug was administered orally at a dose of 1.2 mg/kg bodyweight and treatment was repeated after 48 hours. Of 293 cases treated 236 (80.5 per cent) recovered and 49 (16.7 per cent) died. Five animals were disposed of by the owners and three became chronically infected. No differences were recorded in recovery rate between uncomplicated cases and cases with concurrent anaplasmosis or babesiosis, nor were there any significant differences in recovery rates between animals of different types. However, zebu cattle (Bos indicus) tended to respond more rapidly to treatment than exotic cattle (Bos taurus). Younger animals had a poorer recovery rate than adults. Early treatments were more successful than those administered late. It was concluded that with early detection and treatment, coupled with efficient tick control, halofuginone lactate is effective in the treatment of clinical East Coast fever under field conditions.

Animals↗
PubMed2000

Seroprevalence of coxiellosis in cattle, sheep and people in the east of Turkey.

Serum samples collected randomly from 416 cattle in 48 herds, and 411 sheep in 47 flocks, in eight different locations in the east of Turkey between June and December 1998, were examined by indirect fluorescent antibody test (IFAT) to determine the prevalence of Q fever. The age, sex, breed, tick control and abortion history of the animals were also recorded. In addition, 102 serum samples were collected from apparently healthy people who were at risk of contracting the disease, such as farmers, veterinarians, abattoir and laboratory workers, and veterinary students. Seropositivity was observed in 5-8 per cent (24/416) of the cattle in 17 (35-4 per cent) of the herds and in 10-5 per cent (43/411) of the sheep in 21 (44-7 per cent) of the flocks. Eight of the 102 people were seropositive, with the highest prevalence (12-0 per cent) in farmers and abattoir workers. All the seropositive farmers had seropositive animals. None of the laboratory workers or veterinary students was seropositive.

Animals↗
PubMed2000

Performance of female Rhipicephalus sanguineus (Acari: Ixodidae) fed on dogs exposed to multiple infestations or immunization with tick salivary gland or midgut tissues.

This investigation compared the effects of repeated infestations to immunization of dogs with tick salivary gland or midgut extracts on the feeding and fecundity performances of female Rhipicephalus sanguineus (Latrielle). In each immunized group, three tick-naive dogs were immunized three times with tick salivary gland or midgut extracts, and twice challenged at 21-d intervals by allowing 80 female and 40 male adult ticks to feed on each host. The repeated infestation group of three naive dogs was infested five times at 21-d intervals by the same numbers of ticks. The repeated infestation group showed a trend of reduced tick performance after the third infestation, but some of the tick performance parameters had recovered by the fifth infestation. Tick attachment was reduced by immunization with either tick salivary gland or midgut extract. Immunization with tick salivary gland extract had the greatest impact on the feeding period and engorgement weight of the female ticks. Immunization with tick midgut extract resulted in the greatest reduction of tick fecundity parameters, which included preoviposition, oviposition, and egg-incubation periods in addition to reduced egg production and egg viability. These results confirm that dogs can become resistant to R. sanguineus, and demonstrate that immunization with tick salivary gland or midgut extract has different effects on tick feeding and fecundity.

Animals↗