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At least 325 records · Page 18Linked to original sources
PubMed1996

Prospects for biological control of livestock ticks, Rhipicephalus appendiculatus and Amblyomma variegatum, using the entomogenous fungi Beauveria bassiana and Metarhizium anisopliae.

Both Beauveria bassiana and Metarhizium anisopliae induced approximately 30% mortalities in adult Rhipicephalus appendiculatus feeding on rabbits while M. anisopliae induced a mortality of 37% in adult Amblyomma variegatum. Both fungal species induced reductions in engorgement weights, fecundity, and egg hatchability in adult A. variegatum. M. anisopliae reduced fecundity by 94% in A. variegatum. Furthermore, B. bassiana reduced egg hatchability to 0%, while 11% of the infected females failed to lay eggs. In Zebu cattle naturally infested, with R. appendiculatus in the field, both B. bassiana and M. anisopliae induced high mortalities ranging from 76-85%, a remarkable reduction in fecundity (85-99%), and a significant reduction in egg hatchability (94-100%). When incubated in organophosphate acaricides for up to 120 hr, both fungi retained their normal growth and morphological characteristics. B. bassiana and M. anisopliae persisted on cattle ears for 1 and 3 weeks, respectively, after application. Both B. bassiana and M. anisopliae induced a mortality of approximately 100%, 76-95% and 36-64% in larvae, nymphs, and adults, respectively, of R. appendiculatus seeded in grass in the field. Spores of B. bassiana and M. anisopliae mixed with sterilized sand and maintained at 0 and 25 degrees C maintained good viability for over 12 months (B. bassiana) and for 8 months (M. anisopliae) and no significant difference was observed in spores stored in the two different temperatures.

Animals↗
PubMed1999

Efficacy of entomopathogenic nematode strains against engorged Boophilus annulatus females (Acari: Ixodidae) under simulated field conditions.

The biocidal efficacy of entompathogenic nematodes against engorged females of Boophilus annulatus (Say) was evaluated in soil-filled buckets in a greenhouse, where conditions resemble nature. The 9 tested nematode strains differed markedly in their effect upon tick mortality. The Mexican strain of Steinernema carpocapsae was most efficient, inducing 100% tick mortality at a concentration of 50 nematodes per square centimeter. An increase in the concentration of the S. carpocapsae DT strain to > 200 IJ/cm2 failed to kill more ticks. It appears that entomopathogenic nematodes show promise as tick control agents.

Animals↗
PubMed2001

Tick-Encoded serine proteinase inhibitors (serpins); potential target antigens for tick vaccine development.

Immunological protection of hosts against tick infestation is at present the most practically sustainable alternative tick control method to the current use of acaricides that is riddled with serious limitations. The current focus of tick vaccine research is the identification, cloning and in vitro production of recombinant tick vaccine candidate antigens. We have examined a selected number of reports on the roles of parasite-encoded members of the serine proteinase inhibitor (serpin) superfamily in modulation of mammalian anti-parasite defense and developed some food for thought commentaries on the possibility of targeting this class of proteins for anti-tick vaccine development.

Animals↗
PubMed1982

Drop-off rhythms of engorged Rhipicephalus appendiculatus (Acarina: Ixodidae).

Diurnal drop-off rhythms were exhibited by all three stages of Rhipicephalus appendiculatus engorging on cattle in stalls under natural conditions of light and temperature. Most engorged larvae dropped from the host between 1000 and 1400 hours, most nymphs between 1200 and 1800 hours, and most adults between 0600 and 0800 hours. Under controlled conditions of light and temperature the drop-off rhythms of larvae and nymphs engorging on rabbits were synchronized by oscillators set in the tick in the pre- and postattachment periods. The possibility of a host-induced rhythm was inferred from the data. Drop-off patterns may be used to enhance tick control methods.

Animals↗
PubMed2005

Anointing chemicals and ectoparasites: effects of benzoquinones from millipedes on the lone star tick, Amblyomma americanum.

Many mammals and birds roll on or rub themselves with millipedes that discharge benzoquinones. Chemicals transferred from millipedes onto the integument of anointing animals are thought to deter ectoparasites. We tested the lone star tick, Amblyomma americanum (L.), for responses to three widespread components of millipede defensive secretions, 1,4-benzoquinone; 2-methyl-1,4-benzoquinone (toluquinone); and 2-methoxy-3-methyl-1,4-benzoquinone (MMB). In toxicity tests, ticks were confined for 1 hr in filter-paper packets treated with serial dilutions of each of the benzoquinones or the commercial acaricide permethrin. Ticks were least affected by toluquinone, and most affected by permethrin. Of the benzoquinones, only MMB showed repellent activity. Behavioral assays were more sensitive than mortality for measuring the effects of the benzoquinones. Latencies for ticks to right themselves and to climb were greater with all compounds, even at the lowest concentrations, than with controls. Ticks exposed to low concentrations of benzoquinones appeared to recover over time, whereas those exposed to high concentrations exhibited behavioral abnormalities 1-3 mo later. Our results indicate that benzoquinones appropriated via anointing may reduce the tick loads of free-ranging animals, although key questions remain on the amounts of these compounds available to and effectively appropriated by anointing animals.

Animals↗
PubMed2001

Tick infestation of Borana cattle in the Borana Province of Ethiopia.

A study was conducted to identify and determine burdens of ticks infesting Borana cattle in the Borana Province of Ethiopia. Rhipicephalus pulchellus, Rhipicephalus pravus, Rhipicephalus muhsamae, Rhipicephalus praetextatus, Rhipicephalus evertsi evertsi, Amblyomma gemma, Amblyomma variegatum, Amblyomma cohaerens, Amblyomma lepidum, Hyalomma truncatum, Hyalomma marginatum rufipes and Boophilus decoloratus were identified on the cattle. Their burdens ranged from 658-1,554 with a mean of 1,205 ticks per animal. Out of the total 6,025 ticks collected, about 82% were R. pulchellus, followed by R. pravus (about 8%) and A. gemma (5%). The other nine species of ticks accounted for only 5% of the total burdens. It is suggested that a strategic tick control method, aimed mainly at reducing the R. pulchellus burdens, with the objective of allowing a reasonable number of ticks to remain on cattle for the maintenance of endemic stability to tick-borne diseases be instituted.

Animals↗
PubMed2002

Studies on seasonal dynamics of ticks of ogaden cattle and individual variation in resistance to ticks in eastern Ethiopia.

In this study the dominant tick species identified were Amblyomma cohaerens 52.2%, Rhipicephaluspravus 19.3% and A. variegatum 14.6%. A. cohaerens occurred throughout the sampling period and showed a peak during March. Their number declined significantly (P < 0.01) from August to December. R. pravus occurred from July to December only and peaking in September (P < 0.01). A. variegatum occurred in low numbers throughout the study period with a marked seasonal variation (P < 0.01) and abundant numbers of ticks were observed from May to July. The other tick species identified were Boophilus decoloratus, R. bergeoni and R. evertsi evertsi. Individual variation in tick infestation level was observed among the animals (P < 0.05). Since all the animals were of the same breed, age group and were managed similarly the selection of animals with low infestation level can be a component of tick control strategy.

Animals↗
PubMed1995

Tick resistance to pyrethroids in New Caledonia.

Boophilus microplus is the common cattle tick of great economic importance in New Caledonia. Since 1986, deltamethrin has been used for dipping. In 1992, an increase of tick infestations was seen on some ranches. Field and laboratory studies were conducted to determine if resistant ticks were present. Ticks resistant to deltamethrin were detected on three ranches, with resistance factors from 8.3 to 97.7. All deltamethrin-resistant isolates were also resistant to fenvalerate, but only one was also resistant to flumethrin. The combination of deltamethrin and ethion seemed to be active on isolates. This is the second description of isolates of Boophilus microplus resistant to pyrethroids, the first being in Australia and points to future problems in the management of tick control. Some organophosphates like chlorpyriphos or fenthion were studied as replacements for deltamethrin, in spite of the fact that most ticks are resistant to ethion. The authors propose a rotation strategy based on the alternation of several compounds together with a minimal frequency of dipping.

Animals↗
PubMed1993

In vitro feeding of instars of the ixodid tick Amblyomma variegatum on skin membranes and its application to the transmission of Theileria mutans and Cowdria ruminatium.

An in vitro feeding method using rabbit or cattle skin membranes, applied successfully to all stages (larvae, nymphae and adults) of the ioxodid tick, Amblyomma variegatum, is described. The feeding apparatus consisted of a blood container with a membrane placed on top of a tick containment unit. A carbon dioxide atmosphere of between 5 and 10% and a temperature of 37 degrees C were used as stimulants for the attachment of the ticks. High CO2 concentrations in the atmosphere improved the feeding success of all instars. The effect of anticoagulation methods for the bloodmeal was investigated, and heparinized blood was found to be the most suitable for tick feeding. When the bloodmeal was replaced by tissue culture medium for feeding nymphs the subsequent moulting success was reduced. Adult ticks of both sexes remained attached for up to 16 days, until completion of their bloodmeals. All stages of the tick fed on whole blood in the artificial feeding system and all reached engorged weights less than those achieved by control ticks fed on experimental animals. A large proportion of ticks, fed artificially on whole blood, moulted or laid eggs successfully. The method was successfully applied for the transmission of Theileria mutans and Cowdria ruminantium to cattle.

Animals↗
PubMed2005

Bos taurus and Bos indicus (Sahiwal) calves respond differently to infection with Theileria annulata and produce markedly different levels of acute phase proteins.

Disease-resistant livestock could provide a potentially sustainable and environmentally sound method of controlling tick and tick-borne diseases of livestock in the developing world. Advances in the knowledge and science of genomics open up opportunities to identify selectable genes controlling disease resistance but first, breeds and individuals with distinguishable phenotypes need to be identified. The Bos indicus breed, Sahiwal, has been exploited in dairy breeding programmes, because it is resistant to ticks and has relatively good performance characteristics compared to other indigenous cattle breeds of tropical regions. The analyses reported here show that Sahiwal calves were also more resistant than European Bos taurus (Holstein) dairy breed calves to tick-borne tropical theileriosis (Theileria annulata infection). Following experimental infection with T. annulata sporozoites, a group of Sahiwal calves all survived without treatment, with significantly lower maximum temperatures (P<0.01) and lower rates of parasite multiplication (P<0.05) than a group of Holstein calves, which all had severe responses. Although the Sahiwals became as anaemic as the Holsteins, other measures of pathology, including enlargement of the draining lymph node and the acute phase proteins, alpha1 acid glycoprotein and haptoglobin, were significantly less in the Sahiwals than in the Holsteins (P<0.05). Additionally, the Sahiwals had significantly lower resting levels of alpha1 acid glycoprotein than the Holsteins (P<0.05). Production of a third acute phase proteins, serum amyloid A, had very similar kinetics in both breeds. Acute phase proteins are produced in response to systemic release of the kinds of pro-inflammatory cytokines that are thought to be responsible for the pyrexic, cachectic and anorexic responses characteristic of tropical theileriosis. The prolonged production of alpha1 acid glycoprotein in the Holsteins is indicative of chronic production of circulating pro-inflammatory cytokines. In contrast, Sahiwals appear able to overcome infection with T. annulata as well as limit pathology by preventing the over-stimulation of pathways involving these cytokines.

Acute-Phase Proteins↗
PubMed2004

Stress and transcriptional regulation of tick ferritin HC.

We previously identified a partial Dermacentor variabilis cDNA encoding ferritin HC (HC) subunit homolog (DVFER) that was differentially upregulated in Rickettsia montanensis infected ticks (Mulenga et al., 2003a). We have used rapid amplification of cDNA ends to clone full-length DVFER cDNA and its apparent ortholog from the wood tick, D. andersoni (DAFER), both of which show high sequence similarity to vertebrate than insect ferritin. Both DVFER and DAFER contain the stem-loop structure of a putative iron responsive element in the 5' untranslated region (nucleotide positions, 16-42) and the feroxidase centre loop typical for vertebrate ferritin HC subunits. Quantitative Western and Northern blotting analyses of protein and RNA from unfed and partially fed whole tick as well as dissected tick tissues demonstrated that DVFER is constitutively and ubiquitously expressed. Based on densitometric analysis of detected protein and mRNA bands, DVFER is predominantly expressed in the midgut, and to a lesser extent in the salivary glands, ovary and fatbody. Sham treatment (mechanical injury) and Escherichia coli challenge of D. variabilis ticks stimulated statistically significant (approximately 1.5- and approximately 3.0-fold, respectively) increases in DVFER mRNA abundance over time point matched naive control ticks. These data suggest that DVFER mRNA is nonspecifically up regulated in response to mechanical injury or bacterial infection induced stress.

Amino Acid Sequence↗
PubMed1978

The activity of insect juvenile hormone mimics in larval Amblyomma hebraeum Koch (Acarina: Metastriata: Ixodidae).

A total of 14 insect juvenile hormone mimics was tested for activity in Amblyomma hebraeum by exposing newly engorged larvae to filter paper impregnated with hormone mimics. The most active compounds used in this assay were HS 103 (6-ethyl-3-pyridyl geranyl ether; EC50=0,0018 mg/cm2), ZR 512 (Ethyl 3,7,11-trimethyldodeca-2,4-dienoate; EC50=0,0022 mg/cm2), HS 2 (6-methyl-3-pyridyl geranyl ether; EC50=0,0035 mg/cm2), ZR 615 (N-ethyl 3,7,11-trimethyldodeca-2,4-dieneamide; EC50=0,0035 mg/cm2), ZR 777 (Prop-2-ynyl 3,7,11-trimethyldodeca-2,4-dienoate; EC50=0,0039 mg/cm2) and ZR 515 (Isopropyl-11-methoxy 3,7,11-trimethyldodeca-2,4-dienoate; EC50=0,0094 mg/cm2). Activity in this assay was similar to that reported in insects and was consistent with the susceptibility of these compounds to metabolic inactivation. The results suggest that ZR 615 may be of possible use in tick control.

Animals↗
PubMed2001

OspA immunization decreases transmission of Borrelia burgdorferi spirochetes from infected Peromyscus leucopus mice to larval Ixodes scapularis ticks.

Recombinant outer surface protein A (OspA) vaccination of wild animal reservoirs has potential application for reducing Borrelia burgdorferi transmission in nature and subsequent risk of human infection. As a major reservoir host, the white-footed mouse (Peromyscus leucopus) is a candidate for a vaccination program designed to reduce infection prevalence in vector ticks. In this study we characterized the effect of various levels of immunization with recombinant OspA-glutathione transferase fusion protein on transmission dynamics from infected P. leucopus to larval ticks. Control mice were vaccinated with glutathione transferase alone. All mice were experimentally infected with B. burgdorferi before vaccination. The immune responses of the immunized mice were assessed by enzyme-linked immunosorbent assay for antibodies to OspA. Transmission of B. burgdorferi from infected mice was determined by xenodiagnosis with uninfected larval ticks. Spirochetes in ticks were counted by direct immunofluorescence assay. The concentration of antibody to OspA increased with each OspA vaccination but most markedly after the first and second vaccinations. In comparison with control mice, there was reduced transmission by OspA-vaccinated mice to uninfected ticks. One, two, or three doses of OspA reduced infection prevalence in xenodiagnostic ticks by 48%, 92%, or 99% and the numbers of spirochetes per tick by 84%, 98%, or 99%, respectively. This study suggests that vaccination of P. leucopus with OspA could reduce transmission to the tick vector in nature despite prior infection of the reservoir host.

Animals↗
PubMed1984

Studies on ticks of veterinary importance in Nigeria XVII. Resistance of rabbits to infestation with Amblyomma variegatum and Boophilus decoloratus (Acari: Ixodidae).

Rabbits exposed to larvae, nymphs and adults of Amblyomma variegatum acquired resistance to the infestation with adults of this tick. The degree of acquired resistance was lowest in the rabbits exposed once previously to larvae and highest in those exposed twice previously to adults. Rabbits also acquired resistance after primary infestation with Boophilus decoloratus; their resistance became very high during the thrice-repeated feeding. New terms are introduced for the quantification of the degree of resistance of animals to tick infestation. Rabbits were protected against infestation with B. decoloratus by intravenous injection of serum from the rabbits on which the ticks had fed three times. The relevance of the results to integrated tick control strategies is discussed.

Animals↗
PubMed2003

Serological evidence of exposure to tick fever organisms in young cattle on Queensland dairy farms.

OBJECTIVES: To compare the features of farms on which the exposure of young cattle to tick fever organisms is sufficient to ensure that immunity is high and the risk of clinical disease is low (endemic stability) with those of farms on which exposure is insufficient to induce widespread immunity (hence without endemic stability); to examine the relationships between the management of ticks and tick fever, and endemic stability to Babesia bovis, B. bigemina and Anaplasma marginale. DESIGN: Cross-sectional study of 874 cattle between the ages of 6 and 15 months on 64 dairy farms, from three centres in south-eastern Queensland (Mutdapilly, Dayboro and Kenilworth) and one centre in far-north Queensland (Malanda). PROCEDURE: Blood samples collected from between 5 and 20 calves from each farm were submitted for serological assay to determine exposure to B. bovis, B. bigemina and A. marginale. A questionnaire about the farm characteristics and the management of ticks and tick fever was completed with each farmer. RESULTS: On 73% of farms, confirmed clinical cases of tick fever were recalled by the farmer, indicating that tick fever was a threat on most farms. The majority of herds in the study (54 of 64) did not have sufficient numbers of seropositive animals aged between 6 and 15 months to have a low risk of tick fever. Region had an effect on the likelihood of endemic stability for all tick fever organisms. Cattle near Malanda in Far-north Queensland were more likely to be seropositive to B. bovis and B. bigemina. The method, strategy and intensity of tick control were not related to the likelihood of endemic stability when the effect of region was considered. The decision to leave a few ticks on cattle in an effort to induce endemic stability did increase the likelihood of endemic stability to A. marginale. However, in practical terms, it was ineffective, because only 26% of these farms had endemic stability against all three organisms. CONCLUSIONS: Given the low proportion of farms that have endemic stability to the tick fever organisms and the high likelihood of clinical disease, vaccination is recommended to protect dairy cattle from tick fever throughout the tick infested area of Queensland. However, further work is required to determine the economic value of vaccination, taking into account the costs of vaccination, of outbreaks and the protective value of vaccination.

Anaplasma marginale↗
PubMed2003

Passive immunization with monoclonal antibodies: effects on Haemaphysalis longicornis tick infestation of BALB/c mice.

Tick vaccine development plays an important role in current tick control strategies. Previously, we have produced three different isotypes of monoclonal antibodies (mAbs) which recognized a midgut protein of adult Haemaphysalis longicornis. These mAbs, typed as IgG1, 2a, and 2b, reacted with a 76 kDa surface protein of midgut cells. We speculated that the 76 kDa protein may be an unknown antigen for a tick vaccine and the three mAbs may work as probes to clone the protein. In this study, to test whether these three isotypes have anti-tick effects and if so which works more effectively, we conducted passive immunization in BALB/c mice with each of the mAbs, and infested the mice with adult ticks. All isotypes significantly reduced the number of hatched larvae, compared to controls, however, no differences in the magnitude of the reduction were observed among the three.

Animals↗