Effects of Metarhizium anisopliae on the tick Boophilus microplus (Acari: Ixodidae) in stabled cattle.
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Interaction of entomopathogenic nematodes (Steinernematidae) with selected species of ixodid ticks (Acari: Ixodidae).
Entomopathogenic nematodes, currently used for biological control of various insect pests, were tested for their ability to penetrate and kill replete females of several species of ticks including Dermacentor variabilis (Say), Rhipicephalus sanguineus (Latreille), Amblyomma maculatum Koch, and A. cajennense (F.). These species were found to be susceptible to the entomopathogenic nematodes, Steinernema feltiae (Filipjev) or S. riobravus (Cabanillas & Poinar), shown in previous studies in our laboratory to be attracted to and kill replete A. americanum. S. riobravus killed D. variabilis (96%), R. sanguineus (89%), A. maculatum (24%), and A. cajennense (88%), and S. feltiae killed D. variabilis (91%) and R. sanguineus (71%). Of the ticks that survived mean egg mass weights were significantly lower than those of the unexposed controls. When nematode-exposed ticks were examined with light microscopy, nematodes were found to have entered ticks but did not multiply or produce subsequent generations of infective juveniles. The nematodes were separated from surrounding tissues by a clear space, suggesting that they produced protective compounds. Bacteria, thought to be symbiotes released from the nematodes, multiplied initially in the hemocoel of the tick and subsequently were found throughout the degenerating tick tissues. These bacteria eventually filled the tick and appeared to be the cause of tick death. Nematode guts were filled with the bacteria, suggesting that the bacteria were a food source. When ticks were exposed to nematodes while feeding on cattle, partially engorged females were most susceptible to the nematodes. Tick mortality and reduced egg production resulted when the ticks had fed 6 and 9 d before nematode exposure but not when ticks were exposed after 3 d of feeding. Exposure of feeding female ticks demonstrated that the nematodes were able to penetrate tick orifices other than via the hypostome, which was embedded in the bovine epidermis for the duration of the feeding process.
Animals↗
Successful interrupted feeding of adult Rhipicephalus appendiculatus (Ixodidae) is accompanied by reprogramming of salivary gland protein expression.
Ixodid female ticks take one comparatively large bloodmeal which they convert to a single large egg mass and then they die. To examine the outcome of interrupted feeding, equal numbers of male and female Rhipicephalus appendiculatus adult ticks were fed on guinea pigs (host 1) for either 2, 4, or 6 days, or to engorgement (8 days). All of the fully engorged (D8) females laid a single large egg mass (80-160 mg/tick), while 85% of the day 6-fed (D6) female ticks (n = 20) each laid a small egg mass (6.1 mg/tick). None of the females that had fed for 2 or 4 days oviposited. Ninety percent (n = 20) of the day 2-fed (D2) females survived for 4 weeks after their feeding was interrupted, whereas 65% (n = 20) of the day 4-fed (D4) females survived. All of the surviving partially fed female ticks (D2 and D4) attached to a second guinea pig (host 2) and attained engorged body weights that were not significantly different from those of the control females (P < 0.05). Female ticks that engorged following interrupted feeding layed egg masses comparable to the controls, indicating that engorgement on host 2 was successful. The salivary gland protein profile of female ticks changed constantly during feeding. However, when feeding was interrupted, the protein expression pattern switched back to that of the non-parasitic state, presumably to enable the partially fed ticks to survive and reattach on the new host. This observation indicates that female ixodid ticks have a natural ability to survive and re-establish successful feeding on a new host if the first attempt at feeding is unsuccessful. Such an interrupted feeding mechanism supports the hypothesis that partially engorged ticks may play a role in tick-borne pathogen transmission.
Animals↗
Application of representational difference analysis to identify sequence tags expressed by Metarhizium anisopliae during the infection process of the tick Boophilus microplus cuticle.
Metarhizium anisopliae is a well-characterized biocontrol agent of a wide range of plagues, including insects and acari. To identify genes involved in the infection process, representational difference analysis was performed using cDNA generated from germinated conidia of M. anisopliae in the tick Boophilus microplus cuticle, and cDNA generated during fungal growth in glucose-rich medium. Sequence determination of approximately 135 clones and comparison analysis using public databases led to the identification of 34 sequences and 14 expressed sequence tags with known orthologs. As expected, almost all identified sequences showed significant similarity to other fungal genes. The diversity of gene clusters found reflects the participation of several proteins in the early infection process of M. anisopliae in the cattle tick B. microplus.
Animals↗
Acquired resistance to ticks. I. Passive transfer of resistance.
Guinea-pigs developed resistance to larvae of the ixodid tick, Dermacentor andersoni, after one infestation. Resistance was characterized by guinea-pigs allowing fewer larvae to engorge (5-15%) during a second exposure than during an initial infestation (70-90%). Larvae feeding on resistant hosts weighed less than larvae engorging on a host with no previous exposure to ticks. Evidence is presented which indicates that this resistance can be passively transferred with viable lymph node cells, but not with serum, from resistant guinea-pigs. Recipients of cells from such resistant animals allowed significantly fewer larvae to engorge than did controls previously unexposed to ticks. This was not so in recipients of immune serum. The protection provided by passive transfer of cells from a resistant donor was not as complete as the protection afforded by natural exposure.
Animals↗
Methods to improve the health of cattle in the tropics: immunisation and chemoprophylaxis against haemoparasitic infections.
A study of methods to improve the health of native cattle in tropical areas of Colombia showed an advantage using immunisation techniques against haemoparasitic infections in comparison with other control methods. The control of anaplasmosis and babesiosis by immunisation of cattle with fully virulent Anaplasma marginale, Babesia argentina and B. bigemina is feasible in tropical cattle when the postimmunisation reaction is controlled by appropriate drug therapy. Chemoprophylaxis was found less effective in controlling haemoparasitic diseases; however, treated was found less effective in controlling haemoparasitic diseases; however, treated cattle surviving the acute stage of infection showed weight gains not significantly different from those of the immunised calves. Both methods were found to be advantageous with calves born and raised in an endemic area of anaplasmosis and babesiosis. Tick and gastrointestinal parasitic control without haemoparasitic control in calves had an advantage over no control system at all. These methods though were inferior to the immunisation and chemoprophylactic techniques.
Anaplasmosis↗
Pyriproxyfen effects on newly engorged larvae and nymphs of the lone star tick (Acari:Ixodidae).
Newly engorged larvae and nymphs of the lone star tick, Amblyomma americanum (L.), were exposed to 9 treatments of pyriproxyfen in glass vials consisting of dosages of 4, 8, and 16 micrograms/cm2 for 7 d, 14 d, and continuous exposure periods at each concentration. Treatment of newly engorged larvae resulted in decreased molting, altered postmolt defecation, and nymphal survival with results being dose and exposure dependent. Molting inhibition ranged from 35.9 to 68.4%. Successfully molted nymphs were lethargic, exhibited altered defecation patterns, and were short-lived compared with untreated adults. By 65 d after treatment, cumulative inhibition of molting and hastened mortality of molted adults resulted in 82.6-100% control, depending on dosage and exposure. Treatment of newly engorged nymphs showed minimal to no effect on molting; however, adults were lethargic and displayed altered postmolt defecation patterns. Subsequent adult longevity was most dramatically affected with 87.9-100% control achieved by 82-84 d after treatment. Fecal patterns and survivorship were dose and exposure dependent. Estimates of subsequent feeding success of adults treated as engorged nymphs, show reduced capacities of attachment, engorgement and reproduction.
Animals↗
Management of lone star ticks (Acari: Ixodidae) in recreational areas with acaricide applications, vegetative management, and exclusion of white-tailed deer.
A project on management of lone star ticks, Amblyomma americanum (L.), at Land Between the Lakes, a Tennessee Valley Authority recreational area in Kentucky-Tennessee, during 1984-1988, demonstrated the effectiveness and economics of three control technologies. Acaricide applications (chlorpyrifos at 0.28 kg [AI]/ha), vegetative management (mowing and removal of 40% overstory and 90-100% of midstory, understory, and leaf litter), and host management (white-tailed deer exclusion from a 71-ha campground with a single-line fence) provided 75, 70, and 64% mean controls of all life stages of the lone star tick, respectively. Combinations of acaricide applications + vegetative management, acaricide applications + host management, and acaricide applications + vegetative management + host management produced 94, 89, and 96% mean control of all life stages, respectively. The costs of acaricide applications (two per year), vegetative management (two mowings per year), and white-tailed deer exclusion (single-line fence) were $45, $150, and $30/ha/yr, respectively. Results of this project are used to design management strategies that could be considered for use against lone star ticks in recreational areas.
Analysis of Variance↗
Quinone inhibition of sex pheromone activity in the ticks Dermacentor andersoni Stiles and Dermacentor variabilis (Say).
Disruption of sex pheromone activity in female Rocky Mountain wood ticks, Dermacentor andersoni Stiles, and American dog ticks, Dermacentor variabilis (Say), was achieved by treatment with the quinones para-benzoquinone and menadione. The most effective treatments were those administered by inoculation to unfed, mature, adult females prior to feeding. Inoculation of p-benzoquinone was also effective when administered to feeding ticks, from 2 to 5 days after they had attached, though not to the same extent as when it was given to unfed ticks. Decreases in sex pheromone activity were also observed with D. andersoni females, but not D. variabilis females, allowed to feed on rabbits receiving menadione daily by oral administration. Histochemical studies and electron microscopy revealed loss of neutral lipid secretory droplets in the pheromone glands, but no damage to gland structure, following treatment with p-benzoquinone. Elemental analysis revealed more than four times as much chlorine in pheromone glands of p-benzoquinone-treated D. variabilis females than in pheromone glands from control specimens. An extract of partially fed D. variabilis females treated with p-benzoquinone before feeding contained much more 2,6-dichlorophenol than an extract of untreated, partially fed females. Evidently, the quinone affects the neutral lipid component of the female sex pheromone gland, disrupting secretion and release of pheromone to the external body surface.
Animals↗
Some aspects of tick-borne diseases of British sheep.
The significance of tick-borne fever (TBF) and other tick-borne diseases of British sheep are reviewed. Experimental and field studies were carried out to clarify the role of TBF as a pathogen per se and as a predisposing factor in other diseases. Experimental TBF infection caused anorexia and depression in two- to three-week-old lambs, which under the stress of a hill environment could alone be a cause of mortality. Nine out of 10 lambs experimentally inoculated with Staphylococcus aureus during the febrile phase of a TBF reaction developed pyaemic lesions compared with four out of 20 lambs inoculated with S aureus alone. Specific pathogen-free lambs inoculated with an aerosol of Pasteurella haemolytica serotype A1 during a TBF reaction showed more severe clinical signs and had more extensive pathological changes at necropsy than control lambs given P haemolytica alone. Dual infection with TBF and louping-ill virus showed that not only were dually infected sheep more susceptible to louping-ill but almost all of them succumbed to a haemorrhagic syndrome involving a systemic mycotic infection with Rhizomucor pucillus. None of eight sheep given louping-ill virus alone developed this syndrome. Field studies indicated that morbidity and mortality in lambs in south-west Scotland could be markedly reduced by dipping and long acting antibiotic prophylaxis. Lamb groups in which both of these were carried out incurred losses of only 0.6 per cent compared with 10.3 per cent in control groups. In addition antibiotic-treated lamb groups demonstrated significantly better weight gains than untreated groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Abortion, Veterinary↗
Evaluation of an imidacloprid (8.8% w/w)--permethrin (44.0% w/w) topical spot-on and a fipronil (9.8% w/w)--(S)-methoprene (8.8% w/w) topical spot-on to repel, prevent attachment, and kill adult Rhipicephalus sanguineus and Dermacentor variabilis ticks on dogs.
This study evaluated the effectiveness of two topical spot-on formulations, imidacloprid (8.8% w/w)--permethrin (44.0% w/w) and fipronil (9.8% w/w)--(S)-methoprene (8.8% w/w), to repel, prevent the attachment of, and kill adult Rhipicephalus sanguineus and Dermacentor variabilis on dogs. Twelve purpose-bred beagles were distributed into three groups of four dogs each; one group served as untreated controls and each of the other two groups received one of the test products. Dogs were exposed to 25 adult ticks of each species for 10 minutes on posttreatment days 3, 7, 14, 21, and 28. Nonattached or repelled ticks were collected and evaluated for viability, and on-dog tick counts were conducted at 3, 24, and 48 hours after tick exposure. The imidacloprid-permethrin formulation provided significant repellency of R. sanguineus and D. variabilis for up to 3 and 4 weeks after treatment, respectively; and provided good overall control for R. sanguineus and D. variabilis during the study period. The fipronil--(S)-methoprene formulation provided good overall tick control during the study period.
Administration, Topical↗
Efficacy of injectable doramectin against natural Boophilus microplus infestations in cattle.
Three experiments were conducted in Latin America--1 in Brazil, 1 in Venezuela, and 1 in Argentina--using a common protocol to investigate the efficacy of a single SC injection of doramectin (200 micrograms/kg of body weight) for treatment and control of Boophilus microplus infestations in grazing cattle. In each experiment, 2 groups of 20 to 27 cattle were allocated on the basis of tick burdens present 24 hours before treatment to a treated or control group, which received saline solution (1 ml/50 kg). All cattle were injected in the mid-dorsal cervical region and examined on treatment day and on posttreatment days (PTD) 8, 14, 21, and 28. On each observation day, the number of engorged and semiengorged ticks on half of each animals was counted and recorded. Doramectin was highly efficacious in removing tick burdens and controlling reestablishment of B microplus under field conditions of continuous reinfestation. Compared with tick counts in the control group, doramectin-treated cattle began to eliminate ticks after treatment and efficacy improved on subsequent observation days. In Brazil, efficacy was 91% at PTD 8 and 14, and increased to 99% or higher at PTD 21 and 28. In Venezuela, efficacy was 100% at PTD 8, 14, and 21 and 92% at PTD 28. In Argentina, efficacy progressed from 94.5% at PTD 8 to 99 and 98.5% at PTD 21 and 28, respectively. The reduction of the number of ticks in the doramectin-treated cattle was significant (P < 0.05) at each observation day.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
[Antibacterial therapy as a means of preventing ixodid tick-borne borreliosis].
A special epidemiological experiment to prevent borreliosis in persons bitten by infected ticks was performed in 1992-1994 in the Russia's Perm region where Borrelia garinii and B.afzelii circulate, and Ixodes persulcatus tick is the sole vector transmitting these pathogens to human beings. Adult ticks were removed from the bodies of persons who had referred to health facilities for first aid. Vital preparations were made from the material obtained from the gut of each tick and examined microscopically (up to 250 microscopic fields per preparation). The patients bitten by infected ticks were divided into experimental and control groups and kept under special medical and serological control for 4-5 months. The patients of the experimental group received doxycycline (100 mg twice daily) for 3-5 days after ticks had bitten. Borreliosis was diagnosed by a combination of clinical and serological data. The control group consisted of 97 patients who took no antibiotics after ticks biting and 12 of them contracted borreliosis. In 823 cases Borrelia were not revealed while microscopically analyzing the ticks removed from the patients' bodies; in this group six patients contracted borreliosis. The morbidity rate (per 100 patients) in the experimental group was 1.1, i.e. 11 times lower than that in control group. Among the patients bitten by infected ticks and untreated with antibiotics, this index was 17.6 times higher than in the group bitten by ticks in which Borrelia were not found. There is no absolute probability of detecting the pathogen during a direct microscopic analysis of the preparation made from the tick removed from the body of a bitten patient. However, this rapid identification of Borrelia, followed by short-term antibiotic treatment for microbiological evidence is an effective tool for preventing patients from contracting borrelioses.
Animals↗
Efficacy of various concentrations of coumaphos to control adult, nymphal, and larval stages of an organophosphate-resistant strain of Boophilus microplus on infested cattle.
OBJECTIVE: To evaluate the efficacy of coumaphos, an organophosphate (OP) acaricide, at concentrations up to 2 times higher than the highest concentration required by the US Eradication Program against all stages of an OP-resistant strain of Boophilus microplus in experimentally infested cattle. ANIMALS: 16 tick-naïve 200-kg female Hereford calves. PROCEDURE: Four groups of cattle (4 calves/group) were all infested with Boophilus ticks 3 times before treatment. Each group was treated with coumaphos as follows: group 1, at 0.165% active ingredient (AI); group 2, at 0.299% AI; group 3, at 0.566% AI; and group 4, not treated. Following treatment, ticks were collected for 21 days. Ticks collected 1 to 7, 8 to 14, and 15 to 21 days after treatment were considered adults, nymphs, and larvae, respectively, at time of treatment. RESULTS: Overall control at 0.165, 0.299, and 0.566% AI was 52.9, 75.8, and 89.7%, respectively. Control of adults ranged from 4.3% at 0.165% AI to 73.5% at 0.566% AI. Control of nymphs ranged from 60.6% at 0.165% AI to 97.3% at 0.566% AI. Control of larvae was > 98% at all coumaphos concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: All coumaphos concentrations failed to provide acceptable control for use in the US Eradication Program against OP-resistant ticks. Treatment was least effective against adults and most effective against larvae. Even at 0.566% AI (2 times higher than required by the US Eradication Program), ticks were not eradicated, placing the United States at risk from dispersing cattle harboring viable ticks to uninfested areas.
Animals↗
Reduction of nymphal Ixodes dammini (Acari: Ixodidae) in a residential suburban landscape by area application of insecticides.
Seven formulations of three commercially available insecticides were evaluated for their ability to reduce the density of nymphal deer ticks (Ixodes dammini Spielman, Clifford, Piesman & Corwin) in a suburban residential area endemic for Lyme disease. In total, 101 residential properties in Mount Kisco, Westchester County, NY, were treated with one of the following: carbaryl emulsifiable concentrate (EC) at 0.6 or 1.1 kg AI/ha, carbaryl granular (GR) at 4.5 kg AI/ha, chlorpyrifos wettable powder (WP) at 0.6 or 1.1 kg AI/ha, chlorpyrifos GR at 1.1 kg AI/ha, or cyfluthrin EC at 0.1 kg AI/ha. All three chemicals were found to reduce the density of nymphs on treated properties significantly compared with untreated controls. Percentage of reduction of nymphs ranged from 67.9% for carbaryl EC 1.1 kg AI/ha to 97.4% for chlorpyrifos WP 1.1 kg AI/ha. There was no difference in the amount of reduction provided by each formulation of the same chemical, but carbaryl formulations were significantly less effective than chlorpyrifos or cyfluthrin. Nymphal densities after treatment remained low throughout the course of the study, indicating that a single well-timed spring application is sufficient to provide significant reduction of nymphs for an entire transmission season.
Animals↗
Reduced abundance of Ixodes scapularis (Acari: Ixodidae) with exclusion of deer by electric fencing.
To assess the effect of deer exclusion on populations of Ixodes scapularis Say (formerly I. dammini Spielman, Clifford, Piesman & Corwin) in the northeastern United States, host-seeking ticks and ticks on white-footed mice, Peromyscus leucopus (Rafinesque), were monitored inside and outside a wooded, residential deer exclosure (approximately 3.5 ha) in Lyme, CT, in 1991 and 1992. Another deer exclosure was added in Lyme (approximately 7.4 ha) during 1992. Additional sample sites at other residences served as secondary controls. A seven-wire, slanted, high-tensile electric deer fence was used at both areas. Larvae of I. scapularis were 81.5% (1991) and 97.8% (1992) less abundant within the exclosure than immediately outside the deer exclosures. Nymphs of I. scapularis were 47.4% (1991) and 55.8% (1992) less abundant within the deer fence. The effect on adult ticks was mixed. No difference in tick abundance was seen at the 3.5-ha site. However, larvae, nymphs, and adults were 100, 83.8, and 74.1% less abundant, respectively, in plots at the 7.4-ha exclosure > or = 70 m from the deer fence and isolated from woodlands outside the fence by lawns, driveways, and buildings. The recovery of larvae and nymphs of I. scapularis from mice captured within the deer exclosures indicates that infestations of nymphs and adults are probably, at least in part, a result of the movement of these rodents. Based upon the number of nymphs per 100 m2 infected with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, the causal agent of Lyme disease, there were 73 and 82% fewer infected nymphs within the deer exclosures in 1992 in comparison with the number of infected ticks outside the fence and at the secondary control sites, respectively. The exclusion of deer in conjunction with other tick control strategies in large areas could substantially reduce populations of I. scapularis and the risk of acquiring Lyme disease.
Animals↗
[Ecology of Soldado virus: apparent lack of a viral inhibitor in th tissues of the vector tick Ornithodoros (Alectorobius) maritimus Vermeil and Marguet 1967].
It was previously postulated by others that suspensions of ticks O. (A.) maritmus may contain virucidal material (viral inhibitor) for Soldado virus leading to observe different infection rates according as the ticks were tested individually or in pools. In order to test this hypothesis, suspensions of nymphs of this species originating from a laboratory breeding stock, were mixed with Soldado virus before inoculation to suckling mice. No difference in mortality was observed between the mice receiving the virus exposed to tick suspensions and the controls. So, it seems unlike a viral inhibitor was responsible for the phenomenon. Other factors involved in Soldado virus ecology and possibly influencing the virus isolation efficiency are briefly discussed.
Animals↗
Infectiousness for humans of Ixodes ricinus containing Borrelia burgdorferi.
We studied the rate of transmission of Borrelia burgdorferi from ticks (Ixodes ricinus) to man under field conditions in a case control study. At a holiday camp in southern Germany 384 ticks were removed from 272 persons. Information on symptoms possibly related to Borrelia infection were obtained by a questionnaire to be sent back six weeks after the tick bite. Ticks were examined by immunofluorescence microscopy (IFT) for Borrelia and 49 (12.8%) were found positive. Blood was obtained from 41 persons bitten by Borrelia positive and 41 age and sex matched persons bitten by Borrelia negative ticks. Sera from age and sex matched patients of local hospitals and clinics served as additional controls. Antibody titers were obtained by indirect IFT about 13 weeks after tick bite. Titers 1 : greater than 32 suggested recent infection and 1 : 32 immunity. In the exposed group there were about half as many persons with titers 1 : less than 32 (n = 14) than in the control group (n = 27) suggesting that either part of the infected ticks was in a non-infectious state or the hosts were immune. In the exposed group there were 46.4% (n = 19) and in the control group, bitten by Borrelia negative ticks, 14.7% (n = 6) persons with titers 1 : greater than 32, but 5/6 of these persons in the control group recalled additional tick bites in 1984. Only one child (in the exposed group) developed an Erythema chronicum migrans, and no other Borrelia related manifestations were reported. The manifestation rate of the Borrelia-related disease was 4%.
Adolescent↗