Insecticide control of the Rocky Mountain wood tick on cattle in Wyoming.
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The development of a cell culture vaccine against tropical theileriosis in India is described. Observations on the experiments conducted for the standardization of dose, storage temperature, evaluation of immune response, cross-protection response and field immunization trials are summarized. Future strategies for epidemiological studies and the control of tropical theileriosis are discussed.
Ticks are an ancient group of obligate bloodsucking ectoparasites that has evolved over millions of years. Two general types of ticks are evident today: argasid or soft ticks, and ixodid or hard ticks. Each lineage exhibits distinct patterns of host coevolution and preference. However, about 10% of the approximately 850 species are of medical importance because of their indiscriminate host selection and catholic feeding behavior. As a result, a number of diseases have begun to emerge in the temperate zones, including Lyme borreliosis and several others putatively associated with ticks. Ticks may serve as both pathogens and disease vectors. Because of the unique physiology of the salivary glands and the contents in tick saliva of toxins, feeding alone may cause disease. Ticks also transmit a number of different types of pathogens (viruses, rickettsiae, spirochetes and bacteria, fungi, protozoa, filarial nematodes) and even exceed mosquitoes in this regard. Abatement and control of ticks emphasizes a broad approach because of the differing types of habitats in which pest species may be found. The use of repellents and acaricides as well as cultural and management practices are of primary importance. Other approaches (ivermectin) may be beneficial; with the advent of molecular genetics and its usefulness in immunology, the development of tick vaccines for common pest species appears promising.
The combination of the concentration of formic acid and the duration of fumigation (CT product) during indoor treatments of honey bee, Apis mellifera L., colonies to control the varroa mite, Varroa destructor Anderson & Trueman, determines the efficacy of the treatment. Because high concentrations can cause queen mortality, we hypothesized that a high CT product given as a low concentration over a long exposure time rather than as a high concentration over a short exposure time would allow effective control of varroa mites without the detrimental effects on queens. The objective of this study was to assess different combinations of formic acid concentration and exposure time with similar CT products in controlling varroa mites while minimizing the effect on worker and queen honey bees. Treated colonies were exposed to a low, medium, or high concentration of formic acid until a mean CT product of 471 ppm*d in room air was realized. The treatments consisted of a long-term low concentration of 19 ppm for 27 d, a medium-term medium concentration of 42 ppm for 10 d, a short-term high concentration of 53 ppm for 9 d, and an untreated control. Both short-term high-concentration and medium-term medium-concentration fumigation with formic acid killed varroa mites, with averages of 93 and 83% mortality, respectively, but both treatments also were associated with an increase in mortality of worker bees, queen bees, or both. Long-term low-concentration fumigation had lower efficacy (60% varroa mite mortality), but it did not increase worker or queen bee mortality. This trend differed slightly in colonies from two different beekeepers. Varroa mite mean abundance was significantly decreased in all three acid treatments relative to the control. Daily worker mortality was significantly increased by the short-term high concentration treatment, which was reflected by a decrease in the size of the worker population, but not an increase in colony mortality. Queen mortality was significantly greater under the medium-term medium concentration and the short-term high concentration treatments than in controls.
The efficacy of two commercially available formulations of a desiccant and insecticidal soap were compared with chlorpyrifos wettable powder (0.6 kg [AI]/ha) against the immatures of Ixodes scapularis Say in a woodlot in Westchester County, New York. The desiccant formulation (Drione) was applied at 61.04 kg/ha and an insecticidal soap (Safer's) was applied as a mixture (39 ml concentrate per liter of water) at 107 liters/ha. By 1 wk after application, all treatments significantly reduced the density of nymphs in comparison to untreated plots. Only plots treated with chlorpyrifos had significantly reduced nymphal densities 2 wk after application. By 6 wk after application, there were no differences in nymphal density between treated and untreated plots, which was likely the result of a decline in overall nymphal populations. None of the treatments against nymphs affected larval densities sampled 6 wk after application. Larval density was significantly lower 1 wk after application in plots treated with chlorpyrifos and Safer's insecticidal soap than in untreated plots. By 2 wk after treatment, only plots treated with chlorpyrifos had lower larval densities than untreated plots. Results indicate that the desiccant Drione and Safer's insecticidal soap are good for short-term control of immature I. scapularis.
Lyme disease, unknown in the United States two decades ago, is now the most common arthropod-borne disease in the country and has caused considerable morbidity in several suburban and rural areas. The emergence of this disease is in part the consequence of the reforestation of the northeastern United States and the rise in deer populations. Unfortunately, an accurate estimation of its importance to human and animal health has not been made because of difficulties in diagnosis and inadequate surveillance activities. Strategies for prevention of Lyme disease include vector control and vaccines.
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Rabbits infested with different stages of Amblyomma variegatum Fabricius, 1794 became resistant to subsequent infestations by the same tick. Resistance was manifested by a reduction of 73.6% in the mean engorged weight of female ticks by the 3rd infestation. By the 5th infestation, only 70% of the nymphs engorged and their mean engorged weight was 57.7% of that of nymphs fed on tick-naive control rabbits. In the case of larvae, there was a 22.8% reduction in their mean engorged weight by the 6th infestation. Based on increases in body length while feeding on tick-naive rabbits, the nymphs could be divided into four feeding categories, i.e. Nl (unfed), N2, N3 and N4 (increasing states of engorgement). While 92-96% of ticks which dropped from susceptible rabbits fitted into feeding category N4, only 28% of those that dropped from tick-resistant rabbits fitted into that category. The remainder of the ticks fitted into categories N3 (60%) and N2 (12%). The majority of those ticks with reduced weight developed into adults which had an atypical scutal ornamentation pattern, in that an additional pair of lateral spots was regularly observed on the males. The females of such ticks deposited small numbers of eggs from which no larvae hatched.
In this study we assess the effect of pyrrolizidine alkaloids (PAs) extracted from Lithospermum canescens on the biology of the two-spotted spider mite (Tetranychus urticae Koch). Lithospermum canenscens (Michaux) Lehm. (Boraginaceae) is a common prairie plant also known as Indian paint or hoary puccoon. A mixture of seven PAs with known chemical structures was used in this investigation. Mites treated with PAs showed a high mortality of juveniles, a decrease in female fecundity and a shortened longevity. The intrinsic rate of population increase (r(m)) was used as an indicator of T. urticae population performance after treatment with PAs. The r(m) value obtained with alkaloid-treated leaves was lower than that for mites developing on untreated leaves, which indicates that the mite population would develop much slower on treated plants. The results suggest that further studies should be performed to assess the possible use of PA extracts for spider mite control.
There exist many tick borne infections that are of either economic or public health interest. Mathematical models have previously been used to describe the dynamics of these infections. However it has recently come to light that there is an alternative mechanism for the transmission of these diseases that has not been considered in a modelling framework. This is transmission through ticks co-feeding on non-viraemic hosts. This paper extends a simple mathematical model to include this alternative transmission mechanism. The model is used to describe the dynamics of Louping ill virus in red grouse (the viraemic host) and hares (the non-viraemic host). However, these results are applicable to many other systems. The model is analysed using joint threshold density curves. It is found that the presence of a non-viraemic host allows the virus to persist more readily than it would in the presence of a host that simply amplified the tick population. More importantly, if the level of non-viraemic transmission is high enough the virus can persist in the absence of the viraemic host. This result has important implications for the control of tick borne diseases.
Two major parasitic pests threaten honey bee populations, the external mite Varroa destructor and the internal mite Acarapis woodi (Rennie). Varroa are beginning to develop resistance to the main chemical defense fluvalinate, and alternative control methods are being pursued. Previous studies have shown that botanical oils, especially thymol, can be effective. Six release devices for either thymol or a blend of botanical oils known as Magic 3 were tested in beehives. The release devices were as follows: (1) low density polyethylene (LDPE) sleeves filled with Magic 3, (2) Magic 3-infused florist blocks, (3) thymol infused florist blocks, (4) a canola oil and thymol mixture wick release, (5) a plastic strip coated with calcium carbonate and Magic 3, and (6) an untreated control. There were significant decreases in varroa levels with the use of Magic 3 sleeves, but brood levels also decreased. Tracheal mite levels significantly decreased with the Magic 3 sleeve treatment, the Magic 3 florist block treatment, and the thymol canola wick treatment. A second experiment showed that changing the location of Magic 3 sleeves in the colony did not detrimentally effect brood levels, but also did not effectively control varroa mites.
Blood-feeding ticks must control C activation or be damaged by the host inflammatory response. We report the characterization and expression of a novel, relatively small, broad-acting C inhibitory protein (termed OmCI) from the soft tick Ornithodoros moubata. The native 17-kDa nonglycosylated protein inhibits both human and guinea pig classical and alternative C activation pathways. The IC50 values for each pathway were 12 and 27 nM, respectively, in hemolytic assays using human serum diluted 40-fold. The cDNA encodes a protein of 168 aa, including an 18-aa secretion signal sequence that is absent in the mature form. The inhibitor has 46% amino acid identity with moubatin, a platelet aggregation inhibitor also from O. moubata that is an outlying member of the lipocalin family. Native OmCI had no inhibitory effect on the addition of C8 and C9 to preformed C5b-C7 and C5b-C8 to form the membrane attack complex and no effect on the rate of C3a production by the C3 convertase enzymes C4bC2a, C3(H2O)Bb, or C3bBb. Both recombinant and native OmCI abolish production of C5a by human classical (C4bC3bC2a) and alternative (C3bC3bBb) C5 convertases. Addition of excess C5 but not C3 competes away the inhibitory activity of OmCI, indicating that OmCI targets C5 itself rather than inhibiting the C5 convertase C4bC3bC2a itself. Direct binding of OmCI to C5 was demonstrated by Western blotting and gel filtration chromatography using 125I-labeled proteins. OmCI is the first lipocalin family member shown to inhibit C and also the first natural inhibitor that specifically targets the C5 activation step.
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