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At least 361 records · Page 20Linked to original sources
PubMed1986

Ecology and phenology of ticks in Zambia: seasonal dynamics on cattle.

A study of the seasonality and infestation rates of ticks was carried out in 11 cattle herds in different ecological habitats in Zambia between 1980 and 1982. Wherever possible supplementary data were obtained from opportunistic collections from cattle and other hosts. Analysis of over 1000 tick collections from cattle indicated that infestation rates of the most important species, Amblyomma variegatum and Rhipicephalus appendiculatus vary in different ecological habitats: (i) In Western Province, infestations are much lower than elsewhere; (ii) in Central and Southern Provinces, moderate to high infestations occur; and (iii) in Eastern Province, R. appendiculatus numbers are generally low and A. variegatum numbers are moderate. These two species, however, have similar life cycles throughout their range with one generation per year. Larvae occur mainly from March to May, nymphae from May to September, and adults of A. variegatum from October to December and of R. appendiculatus from December to April. Boophilus decoloratus appears to have two to four generations per year but is uncommon during the rainy season. In some areas in central Zambia Rhipicephalus compositus adults are seasonally common in September-October whereas Rhipicephalus evertsi is more or less ubiquitous. Low to moderate infestations of Hyalomma truncatum and Hyalomma rufipes occur in most areas. At least 14 other less common or rare species of Rhipicephalus, Amblyomma, Haemaphysalis and Ixodes were taken infrequently from cattle. These and other host-specific species were also collected from dogs, sheep, various wildlife hosts and the environment. Infestation rates, seasonality and host-relationships of tick species are discussed in relation to their ecology. Relevant biosystematic and disease relationships are reviewed briefly. The baseline data derived from this study are adequate for integrated analysis with those from other ecological and economic investigations to formulate tick control strategies.

Animals↗
PubMed1993

New version of LSTSIM for computer simulation of Amblyomma americanum (Acari: Ixodidae) population dynamics.

A previous version of Lone Star Tick Simulation Model (LSTSIM) for a wildlife ecosystem was revised and expanded to include a beef cattle forage area and improved handling of tick-host-habitat interactions. Relationships between environmental and biological variables were also refined in the new version. General validity of the revised model was established by comparing simulated and observed host-seeking populations of Amblyomma americanum (L.) at five geographic locations, three in Oklahoma and two in Kentucky-Tennessee. Additional validity was indicated from comparisons of simulated and observed seasonality of lone star ticks at one location in Kentucky. The model produced acceptable values for initial population growth rate, generation time, and 15-yr population density when historical weather files for 14 locations in the United States were used. The model of A. americanum population dynamics was used to study the relationship between tick density and density of white-tailed deer, Odocoileus virginianus (Zimmerman), and cattle. The revised model can be used for additional simulation studies on effects of tick control technologies and integrated management strategies.

Animals↗
PubMed2005

Reservoir competence of native North American birds for the lyme disease spirochete, Borrelia burgdorfieri.

Reservoir competence for the Lyme disease spirochete, Borrelia burgdorferi, was tested for six species of native North American birds: American robin, gray catbird, brown thrasher, eastern towhee, song sparrow, and northern cardinal. Wild birds collected by mist netting on Fire Island, NY, were held in a field laboratory in cages over water and locally collected larval ticks were placed on the birds, harvested from the water after engorgement, and tested for infection by direct fluorescentantibody staining after molting to the nymphal stage. American robins were competent reservoirs, infecting 16.1% of larvae applied to wild-caught birds, compared with 0% of control ticks placed on uninfected laboratory mice. Robins that were previously infected in the laboratory by nymphal feeding infected 81.8% of applied larvae. Wild-caught song sparrows infected 4.8% of applied larvae and 21.1% when infected by nymphal feeding. Results suggest moderate levels of reservoir competence for northern cardinals, lower levels for gray catbirds, and little evidence of reservoir competence for eastern towhees or brown thrashers. Lower infection rates in larvae applied to wild-caught birds compared with birds infected in the laboratory suggest that infected birds display temporal variability in infectiousness to larval ticks. Engorged larvae drop from birds abundantly during daylight, so the abundance of these bird species in the peridomestic environment suggests that they might contribute infected ticks to lawns and gardens.

Animals↗
PubMed1992

Studies on the development and survival periods of the non-parasitic stages of Boophilus microplus (Canestrini), in the climatic conditions of Ranchi (India).

Engorged female ticks of Boophilus microplus were exposed in wire-gauze cylinders and glass tubes in an experimental grass plot at monthly intervals during 1989, and egg laying, egg development and larval survival periods observed and recorded. Rainfall and atmospheric relative humidity had an important influence on tick activity. Egg production was maximum, hatching percentage was high, incubation and prehatch periods were short, and larval survival and total longevity periods were long for ticks exposed during the warm and humid rainy season from June to September. Dry atmospheric conditions severely affected egg development, egg hatch and larval survival. Eggs failed to hatch in the dry months from December to April and only 29-38% hatched after a long incubation period of 41 days in November and May. On grass, the larvae of ticks exposed in November survived for the shortest period of 28 days and the larvae of ticks exposed in June survived for the longest period of 133 days. Low winter temperatures reduced egg production and prolonged the pre-oviposition, oviposition and incubation periods. It is suggested that the results of this study might be helpful in the development of measures to control tick infestation by planned dipping and restricted grazing during the period from late June to January when the pasture has a substantial load of larval ticks.

Animals↗
PubMed1998

Studies on host resistance to tick infestations among trypanotolerant Bos indicus cattle breeds in east Africa.

Recent epidemiological studies carried out in East Africa have indicated that some Bos indicus cattle breeds such as the Orma Boran and Maasai Zebu have a degree of trypanotolerance worth exploitation by their introduction into trypanosomosis endemic areas where other cattle breeds cannot survive. However, in most areas of East Africa, trypanosomosis, ticks, and tick-borne diseases occur together. It is therefore important to obtain information on the susceptibility of these breeds to tick infestation and tick-borne diseases. This study was therefore designed to determine the susceptibility of these cattle breeds to tick infestations. They were compared with the Galana Boran (trypanosusceptible) and the Friesian (susceptible to tick infestations, tick-borne diseases, and trypanosomosis). The four breeds of cattle were exposed to natural tick challenge for a period of seven months and whole body weekly tick counts were done on each animal. Significant differences to tick infestations among the four breeds were observed. For both Rhipicephalus appendiculatus and Boophilus decoloratus, susceptibility to infestation increased in the order, Maasai Zebu, Orma Boran, Galana Boran and Friesian. The results generated by this pilot study so far suggest that variation in susceptibility to tick infestations exists among the four breeds. The Orma Boran and Maasai Zebu showed greater resistance to tick-infestations than the Galana Boran and Friesian. This suggests that utilization of these trypanotolerant cattle breeds could be feasible even in the face of tick challenge and should therefore be considered when planning integrated trypanosomosis and tick control strategies.

Africa, Eastern↗
PubMed2004

Eprinomectin pour-on for control of Boophilus microplus (Canestrini) ticks (Acari: Ixodidae) on cattle.

The efficacy of a commercial pour-on formulation of eprinomectin, a macrocyclic lactone, against experimental infestations of Boophilus microplus (Canestrini) ticks was evaluated in two trials involving 27 Bos taurus calves. The first trial was designed to evaluate the effects of a single treatment at a dose of 0.5 mg/kg of body weight against standard size B. microplus females (4.5-8.0 mm long). A significant reduction in tick numbers (P<0.05, Wilcoxon test) was observed between treated calves as compared to untreated ones from Day 3 (44% efficacy) after treatment to the end of the trial on Day 28 (96.9%), with a peak efficacy of 97.1% on Day 21. In the second trial the effect of eprinomectin on standard size tick numbers, engorgement weight and fertility of female ticks from calves with a single treatment dose of 1 mg/kg on Day 0 and calves treated twice at a dose of 0.5 mg/kg on Days 0 and 4 was evaluated. An efficacy >93% was obtained from Day 2 to Day 28 after treatment in calves treated twice at 0.5 mg/kg, and to the end of the trial (Day 35) in calves treated once with 1 mg/kg. The 1mg/kg treatment provided >98% residual efficacy for at least 7 days. During the first part of the second trial the efficacy of eprinomectin resulted from a dramatic adverse effect on engorgement weight and fertility of female ticks, with 100% control on Day 5 (dosage of 1 mg/kg) and on Days 6 and 7 (two doses of 0.5 mg/kg). Following Day 7, most of the effect was due to reduction in the number of standard size female ticks.

Administration, Topical↗
PubMed2001

Prevention of Lyme disease: a review of the evidence.

The Healthy People 2010 public health goals targeted a 44% decrease in the incidence of Lyme disease, the most commonly reported tick-borne illness in the United States. To review Lyme disease prevention, clinical trials, epidemiological and experimental studies, and predictive models were evaluated. Geographic distribution of ixodid vectors and local landscape predict Lyme disease risk. Density of infected ticks correlates with incidence and prevalence of Lyme disease, but risk quantitation is made uncertain by tick aggregation and inability to predict tick-human interactions. Outdoor activities are inconsistently or weakly associated with risk, and most infections likely occur in residential areas during routine activities. Tick control (burning or removing vegetation, acaricide use, and deer elimination) reduces Ixodes scapularis populations by up to 94%, and acaricide application to wildlife decreases nymphal I scapularis populations by up to 83%. The effect of these strategies on incidence of Lyme disease in humans is unknown. Studies show that only 40% to 50% of adults take precautions against tick bites even when they are aware of Lyme disease. Effective protection afforded by personal precautions (wearing protective clothing, avoiding ticks, and using insect repellant) has not been shown prospectively. Antimicrobial prophylaxis of tick bites is not warranted. Clinical trials showed vaccines containing recombinant OspA of Borrelia burgdorferi to be efficacious and well tolerated. Currently, vaccination is the only empirically demonstrated method to prevent Lyme disease. The best evidence supports prevention efforts focused on practices that encourage immunization, Lyme disease awareness, and possibly treatment of deer.

Adult↗
PubMed1998

Effect of particulation on the immunogenic and protective properties of the recombinant Bm86 antigen expressed in Pichia pastoris.

The recombinant Bm86 tick antigen expressed in Pichia pastoris is obtained in a highly particulated form, as a distinguish feature of this expression system. This particulated protein, the active principle of the recombinant vaccine Gavac against the cattle tick, have shown high immunogenic and protective properties, probably associated with its own characteristics. To evaluate the effects of particulation on the properties of Bm86, three groups of calves were immunized with particulated or non-particulated recombinant Bm86 and the anti-Bm86 antibody response determined. Animals were challenged with a controlled tick infestation and the protective capacities of both proteins assessed. Humoral immune response and protection in cattle vaccinated with the particulated antigen were higher. These experiments suggested that particulation of the Bm86 expressed in P. pastoris is an important feature for the protective properties of the antigen in vaccine preparations.

Animals↗
PubMed2002

Expression and immunolocalization of a Boophilus microplus cathepsin L-like enzyme.

Efforts are being undertaken to control tick infestations that cause important economic losses. A cathepsin L-like endopeptidase of Boophilus microplus was expressed in Escherichia coli; the recombinant enzyme was capable of hydrolysing gelatin, tick vitellin and bovine haemoglobin. In this paper we focus on the expression and local of synthesis of this enzyme in the tick. RT-PCR experiments showed that this endopeptidase is transcribed in the gut of partially engorged tick females. In immunoblotting, polyclonal antibodies against the recombinant enzyme reacted with proteins of larvae older than 5 days, of fully and partially engorged female gut. In immunolocalization experiments the enzyme was localized in probable secretory cells of the gut. Based on our findings we postulate that BmCL1 may be involved in haemoglobin degradation in the B. microplus gut. This enzyme may be used as target for the control of this parasite.

Animals↗
PubMed1999

Evidence and mechanisms of immunosuppression in tick infestations.

The abundance and ubiquity of ticks from ancient times long ago suggested that they have eluded host immunity. In the last 15 years, several authors have demonstrated suppression of the Th1 responses (cell-mediated immunity), and sometimes the Th2 responses (humoral immunity), subsequent to tick infestations in laboratory and natural models. Although the mechanisms to produce suppression are not well-defined yet, evidences for antigenic competition, lymphocyte cytotoxicity, presence of immuno-inhibiting substances in the saliva, and existence of modulators of cytokines in salivary extracts have been reported. Management of tick-induced immunosuppression is essential to replace tick control by acaricide application with more environmentally sound vaccination.

Animals↗
PubMed1996

Factors of variation of Amblyomma variegatum infestation on Creole cattle in Guadeloupe.

The level of infestation of "Creole" beef cattle of Guadeloupe by the tick Amblyomma variegatum was recorded during a long-term survey in an experimental farm: 61 steers and 83 cows were distributed in different lots according to sex and management. They grazed continuously either on irrigated Digitaria decumbens pastures or on dry native savannahs. Tick numbers as well as animal weights were registered monthly. Climatic data were also recorded. Different acaricide treatments were tested during the survey. But in order to minimize their effect in the data analysis, only tick counts over an average of 5 adult ticks per cattle were taken into account. The level of infestation is analyzed with respect to environmental factors (season, management) and individual factors (sex, weight, physiological stage, genetic effect). The effects of these factors are discussed with regard to alternative tick-control methods, such as the selection of resistant hosts.

Analysis of Variance↗
PubMed1989

Financial analysis of East Coast fever control strategies on beef production under farm conditions.

This study provides a financial analysis of an East Coast fever immunisation trial conducted on a farm in the Coast Province of Kenya. The objective of the trial was to assess the effects of immunisation by the infection and treatment method, under different acaricidal treatments, on the productivity of beef cattle. Eighty beef cattle were immunised and an equal number acted as controls. The immunised and unimmunised groups were divided into four subgroups of 20 animals. Two subgroups, one from the immunised and one from the unimmunised group, were sprayed with acaricide twice a week; a second pair of subgroups was sprayed once every three weeks; a third pair had prolonged release acaricide-impregnated ear-tags inserted into each ear; and a fourth pair had no tick control treatment. Financial analysis revealed that the immunised subgroups were more profitable, owing to lower mortality and higher weight gains than the unimmunised subgroups. Of the immunised subgroups, the best was that sprayed with acaricide twice a week; it yielded a marginal rate of return of 244 per cent and maximised financial benefits to the farmer in this trial. However, further trials under different production circumstances would be required before the method could be recommended for widespread adoption.

Animals↗
PubMed1983

East Coast fever as a cause of calf mortality in Zanzibar.

Crossbred and zebu calves at 4 to 5 months of age in an area where tick control was carried out showed little difference in mortality. Crossbred calves at 10 months of age had a mortality rate of 20% from all causes, 14% from East Coast fever. Serological results plus mortality studies showed that the survival rate of crossbred calves known to have been exposed to ECF was 57%. Serological results further showed that, in spite of tick exposure, only 26% of the crossbreds had seroconverted at 10.3 months of age while 15% zebus had positive titres.

Animals↗
PubMed2005

Effects of barrier application of granular deltamethrin on subadult Ixodes scapularis (Acari: Ixodidae) and nontarget forest floor arthropods.

We evaluated the effects of a single application of granular deltamethrin made against nymphal Ixodes scapularis Say on the diversity and abundance of forest arthropods taken in pitfall traps in oak forest sites for 16 wk after treatment in central New Jersey. Control of I. scapularis subadults on treated plots ranged between 97 and 100% and continued at least 12 wk postapplication. Significant short-term changes in arthropod assemblages were detected at one of three study sites within 4 wk posttreatment. Effects were not distributed equally across taxa. Seasonal changes in numbers and diversity of forest arthropods in the study areas may have affected the impact of the acaricide in the treatment area. Comparison with control areas indicated that reductions in abundance of some arthropod taxa in the treatment area were detectable 12 wk after treatment. Total arthropod species diversity was not significantly affected by the application, and no treatment effects were detected 16 wk postapplication, suggesting that the arthropod community had recovered from the effects of the application. The merits of barrier applications in integrated tick control programs are discussed.

Animals↗
PubMed1991

The occurrence of streptothricosis and its association with Amblyomma variegatum ticks in St. Lucia.

Cattle, horses, sheep and goats in all areas of St. Lucia were examined to ascertain the prevalence and distribution of streptothricosis on the island and to investigate its association with the occurrence of Amblyomma variegatum ticks. Although the disease was found to occur throughout St. Lucia it was more prevalent and generally of a more severe form in areas where A. variegatum ticks are present. A tick control programme in the North of the island appeared to have resulted in a dramatic reduction in the prevalence of the disease.

Actinomycetales↗
PubMed1999

Antibody levels to recombinant tick calreticulin increase in humans after exposure to Ixodes scapularis (Say) and are correlated with tick engorgement indices.

The antibody responses of subjects who presented with a definite Ixodes scapularis (Say) tick bite were measured to determine the utility of the antibody response against recombinant tick calreticulin (rTC) as a biologic marker of tick exposure. Subjects bitten by I. scapularis evidenced an increase in anti-rTC antibody levels between visit 1 and visit 2 from 24.3 to 27.1 ng/microl serum (n = 88, p = 0.003), and levels remained elevated at visit 3 (p = 0.005). These anti-rTC antibody levels during visits 2 and 3 were significantly higher than those in four non-exposed controls. Tick engorgement indices, measured on the biting ticks, were found to be correlated with anti-rTC antibody levels (e.g., for visit 3: Pearson's r = 0.357, p = 0.001). Tick engorgement index (TEI), ratio of body length to scutal width, was identified to be the only independent predictor of anti-rTC antibody levels in linear regression models. Logistic regression revealed that a bite from an I. scapularis tick that became engorged (TEI >3.4) was a risk factor for anti-rTC antibody seropositivity (adjusted odds ratio for age and bite location = 7.4 (95% confidence interval 2.1-26.4)). The anti-rTC antibody test had a sensitivity of 0.50 and a specificity of 0.86 for a bite from I. scapularis that became engorged. Immunoblotting revealed that subjects made a specific anti-rTC antibody response.

Adult↗
PubMed2003

Epidemiological study on clinical bovine dermatophilosis in northern Ethiopia.

A total of 5586 indigenous and cross breed cattle were examined for clinical dermatophilosis, and 292 (5.22%) were positive. In indigenous cattle, statistically discernible (p < 0.05) difference was recorded between the prevalence in wet (5.5%) and dry (4.0%) seasons. During both seasons, infestation with A. Variegatum significantly (p < 0.05, chi 2 = 59.9) influenced clinical dermatophilosis. A. variegatum-infested cattle were at 7x higher risk (OR, Odds Ratio = 6.8) of acquiring the disease than non-infested ones. Logistic regression analysis of the overall prevalence showed a significant difference (p < 0.05) between prevalence in indigenous and cross breeds; the crossbreeds being at about 3x higher risk (OR = 2.68). Improved management reduced the prevalence in cross breeds from 15.1% in dry to 8.6% in wet season suggesting the significance of management in the epidemiology of dermatophilosis. The disease occurrence was also significantly (p < 0.05, chi 2 = 133.05) affected by agro-climatic (altitude) variation suggesting the impact of rainfall, humidity, vegetation and vector population that varied with altitude. Age and gender had no influence (p > 0.05) on the disease. Our result showed that season of the year, breed, management, infestation with A. variegatum and agro climatic difference are important risk factors influencing the disease pattern in the region. A tick control strategy and a better and adequate management particularly when keeping cross breeds are recommended.

Actinomycetales Infections↗
PubMed2006

Infection of Ixodes scapularis ticks with Rickettsia monacensis expressing green fluorescent protein: a model system.

Ticks (Acari: Ixodidae) are ubiquitous hosts of rickettsiae (Rickettsiaceae: Rickettsia), obligate intracellular bacteria that occur as a continuum from nonpathogenic arthropod endosymbionts to virulent pathogens of both arthropod vectors and vertebrates. Visualization of rickettsiae in hosts has traditionally been limited to techniques utilizing fixed tissues. We report epifluorescence microscopy observations of unfixed tick tissues infected with a spotted fever group endosymbiont, Rickettsia monacensis, transformed to express green fluorescent protein (GFP). Fluorescent rickettsiae were readily visualized in tick tissues. In adult female, but not male, Ixodes scapularis infected by capillary feeding, R. monacensis disseminated from the gut and infected the salivary glands that are crucial to the role of ticks as vectors. The rickettsiae infected the respiratory tracheal system, a potential dissemination pathway and possible infection reservoir during tick molting. R. monacensis disseminated from the gut of capillary fed I. scapularis nymphs and was transstadially transmitted to adults. Larvae, infected by immersion, transstadially transmitted the rickettsiae to nymphs. Infected female I. scapularis did not transovarially transmit R. monacensis to progeny and the rickettsiae were not horizontally transmitted to a rabbit or hamsters. Survival of infected nymphal and adult I. scapularis did not differ from that of uninfected control ticks. R. monacensis did not disseminate from the gut of capillary fed adult female Amblyomma americanum (L.), or adult Dermacentor variabilis (Say) ticks of either sex. Infection of I. scapularis with R. monacensis expressing GFP provides a model system allowing visualization and study of live rickettsiae in unfixed tissues of an arthropod host.

Animals↗