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PubMed2005

Spatial and temporal distribution of imidacloprid and thiamethoxam in citrus and impact on Homalodisca coagulata populations.

Titers of two systemic neonicotinoid insecticides in citrus trees were measured in conjunction with conventional evaluations of their impact on glassy-winged sharpshooter (Homalodisca coagulata (Say); GWSS) populations. Xylem fluid samples were collected at regular intervals and from multiple locations within field-grown citrus trees to determine imidacloprid and thiamethoxam concentrations using commercial ELISA kits. Uptake profiles varied considerably with peak mean titers of imidacloprid occurring 6-8 weeks after application compared with 2 weeks for thiamethoxam. The persistence of each compound also varied as near-peak levels of imidacloprid were sustained for another 6-10 weeks before gradually declining. In contrast, thiamethoxam titers declined more rapidly after the initial peak, possibly reflecting an application rate only one-quarter of that used for imidacloprid. Within-tree distributions were more similar for the two compounds, with no significant effect due to height of the sample (upper or lower half) or to the quadrant location within the tree, with the exception of one quadrant in the thiamethoxam-treated trees. Substantial reductions in GWSS nymphs and adults were observed in imidacloprid-treated trees during the 2001 trial and were sustained for 4-5 months after treatment. Treatment effects on nymphs were not as well pronounced in the 2002 trial, when overall GWSS infestations were much reduced from the previous year. However, consistently lower adult infestations were still observed in 2002 for both treatments compared with untreated trees. Information on the spatial and temporal profiles in citrus trees was obtained for both compounds to complement field impact data and improve understanding of their pest management potential.

Animals↗
PubMed1999

Effect of endosulfan runoff from cotton fields on macroinvertebrates in the Namoi river.

Of the several pesticides used in the pest management strategy for cotton, endosulfan is ranked as having the greatest impact on the riverine ecosystem. A survey of changes in the densities of six abundant macroinvertebrate taxa (ephemeropteran nymphs Jappa kutera, Atalophlebia australis, Tasmanocoenis sp., and Baetis sp. and two trichopteran larvae, Cheumatopsyche sp. and Ecnomus sp.) between upstream and downstream zones of the cotton-growing region in the Namoi River was conducted between November 1995 and February 1996. In November and December 1995, there were few differences in population densities between all sites. In January and February 1996, population densities of the study taxa increased 7- to 10-fold higher at the two reference sites, with low concentrations of endosulfan in sediment and in passive samplers placed in the water column. In contrast, densities of these taxa at sites with exposure to 25-fold higher concentrations of endosulfan remained static and were between one and two orders of magnitude lower than densities at the reference sites in January and February. Population densities of Baetis sp., a mobile ephemeropteran, did not indicate any inverse relationship with endosulfan concentrations. Multivariate redundancy analysis indicated that endosulfan concentrations were the leading environmental predictor of changes in density of the five benethic taxa. Laboratory 48-h LC50 values of technical endosulfan in river water were 0.6, 1.3, and 0.4 ppb for early-instar nymphs of A. australis and J. kutera, and larvae of Cheumatopsyche sp., respectively. Endosulfan sulfate formed a large proportion of the total endosulfan concentrations measured from in situ passive samplers, indicating that its main route of entry into the river is through surface runoff during storm events.

Agrochemicals↗
PubMed2001

Phylogeny of the major lineages of Membracoidea (Insecta: Hemiptera: Cicadomorpha) based on 28S rDNA sequences.

Analysis of sequences from a 3.5-kb region of the nuclear ribosomal 28S DNA gene spanning divergent domains D2-D10 supports the hypothesis, based on fossil, biogeographic, and behavioral evidence, that treehoppers (Aetalionidae and Membracidae) are derived from leafhoppers (Cicadellidae). Maximum-parsimony analysis indicated that treehoppers are the sister group of a lineage comprising the currently recognized cicadellid subfamilies Agalliinae, Megophthalminae, Adelungiinae, and Ulopinae. Based on this phylogenetic estimate, the derivation of treehoppers approximately coincided with shifts in physiology and behavior, including loss of brochosome production and a reversal from active, jumping nymphs to sessile, nonjumping nymphs. Myerslopiidae, traditionally placed as a tribe of the cicadellid subfamily Ulopinae, represented a basal lineage distinct from other extant membracoids. The analysis recovered a large leafhopper lineage comprising a polyphyletic Deltocephalinae (sensu stricto) and its apparent derivatives Koebeliinae, Eupelicinae (polyphyletic), Selenocephalinae, and Penthimiinae. Clades comprising Macropsinae, Neocoelidiinae, Scarinae, Iassinae, Coelidiinae, Eurymelinae + Idiocerinae, Evacanthini + Pagaroniini, Aphrodinae + Ledrinae (in part), Stenocotini + Tartessinae, and Cicadellini + Proconiini were also recovered with moderate to high branch support. Cicadellinae (sensu lato), Ledrinae, Typhlocybinae, and Xestocephalinae were consistently polyphyletic on the most-parsimonious topologies, but constraining these groups to be monophyletic did not significantly increase the length of the cladograms. Relationships among the major lineages received low branch support, suggesting that more data are needed to provide a robust phylogenetic estimate.

Animals↗
PubMed1996

Infestations of the bont tick Amblyomma hebraeum (Acari: Ixodidae) on different breeds of cattle in Zimbabwe.

Infestations of adults and nymphs of Amblyomma hebraeum were counted on Brahman (Br), Brahman x Simmental (BS), Sanga (Sa) and Hereford (He) steers exposed to infested pastures at Mbizi in southern Zimbabwe in 1986-1987. Herefords were always the most heavily infested, while the Sanga tended to carry the fewest ticks with the Brahman and Brahman x Simmental groups being in between. The ratios of the engorged females on the four breeds were 2.3:1.4:1.4:1.0 for He:Br:BS:Sa. The ratios of the standard nymphs were 2.2:1.4:1.7:1.0 for He:Br:BS:Sa. The results confirm earlier observations in Africa and support the view that there are genetic differences between breeds in the expression of resistance to this tick species.

Animals↗
PubMed1993

Ticks (Acari: Ixodidae) infesting the Arabian camel (Camelus dromedarius) in the Sinai, Egypt with a note on the acaricidal efficacy of ivermectin.

In this study, tick burdens on camels (Camelus dromedarius) were determined in the vicinity of the St. Catherine monastery, Sinai, Egypt. In total 2,545 ticks (1,491 adults and 1,054 nymphs) were collected and identified. Mean tick burdens were relatively heavy and the range in number of ticks per camel was very broad (6-173). Hyalomma dromedarii was the predominant tick species and accounted for 95.6% of the adult ticks. Other ticks found were H. marginatum subspp. and H. anatolicum excavatum. All nymphs collected were Hyalomma spp. In addition, the effect of ivermectin (Ivomec MSD AGVET) on tick burdens, when given subcutaneously at 0.2 mg/kg-1, was evaluated in nine camels in the date-palm plantation of Kibbutz Yahel in the Arava valley, Israel. Initial tick burdens on these camels (half-body tick counts) ranged from 20-105 ticks per camel. Seven camels from the same herd with half-body tick counts ranging from 40-107 ticks per camel were not treated and served as a control group. Ivermectin was not effective against Hyalomma tick infestation in camels under these conditions.

Animals↗
PubMed1994

The effect of rainfall on tick challenge at Kyle Recreational Park, Zimbabwe.

The effect of rainfall pattern on tick challenge was investigated at Kyle Recreational Park, Zimbabwe, from 1991 to 1992 using drag and removal plot methods to sample environmental tick density. The abundance of adults and nymphs of the brown ear-tick Rhipicephalus appendiculatus and larvae of the bont tick Amblyomma hebraeum was positively correlated with monthly rainfall, whereas no relationship with rainfall was revealed for larval R. appendiculatus, adults of the red-legged tick R. evertsi, or larvae of the blue tick Boophilus decoloratus. A comparison between 1991 (490 mm rainfall) and the drought year of 1992 (161 mm) revealed significant differences in the abundance of R. appendiculatus, A. hebraeum, and B. decoloratus. During the wet season, R. appendiculatus adults were 2-3 times more numerous in the environment during the higher rainfall year of 1991. A. hebraeum larval abundance exhibited a similar pattern to that of R. appendiculatus adults, but B. decoloratus larvae were more abundant in the drought year of 1992 during both the wet and dry seasons. Comparable tick abundance data collected at Kyle during the above-average rainfall years of 1975-1977 (mean = 1029 mm) were compared with tick challenge during the below-average rainfall years of 1991-1992 (mean = 326 mm). In grassland sand habitat and all habitats combined R. appendiculatus adults, nymphs, and larvae were much more abundant during the high rainfall years. In contrast, larvae of B. decoloratus were more numerous during the drier years. A hebraeum larvae were also more abundant during the drier years. The strong positive correlation of adult R. appendiculatus abundance with rainfall and the coincidence of increased adult tick challenge with increased rainfall indicate that adult R. appendiculatus tick burden on hosts would be heaviest during the wet season and high rainfall years.

Animals↗
PubMed1996

Seasonal incidence of Ixodes ricinus ticks (Acari:ixodidae) on rodents in western France.

Data collected from a longitudinal survey carried out over 2 years on four farms in western France were used to assess the incidence and infestation of Ixodes ricinus on rodents. Once a month, on each farm, 25 Sherman live traps were set in hedges bordering selected pastures. A total of 799 micromammals were examined, including Apodemus sylvaticus, Clethrionomys glareolus, Microtus agrestis, Microtus arvalis, and Crocidura spp. Larvae and nymphs of I. ricinus were found. Small numbers of Ixodes (Exopalpiger) trianguliceps were also recovered from each farm. The mean infestation rate of the I. ricinus larvae (1.6-5.9) among all animals examined varied between farms Most animals were infested by only a single tick, but one M. agrestis harboured 43 I. ricinus larvae. Larvae or nymphs were found throughout the year, with peaks from March to October.

Animals↗
PubMed1993

The Ixodes ricinus tick as a vector of Borrelia burgdorferi in Slovenia.

In many parts of Slovenia, the vegetation, climate and animals form an ideal natural environment for the persistence of different tick species. In this study, Ixodes ricinus ticks, the prevalent tick species in our country, are identified as the vectors of Borrelia burgdorferi in Slovenia. Ticks were collected by flagging between May and October 1990. All the ticks collected from different parts of Slovenia were I. ricinus and each one was examined individually. The ticks were tested to determine the presence of B. burgdorferi by indirect immunofluorescent assay. Among the 496 ticks examined for borreliae there were 85 adults and 411 nymphs. Twenty (23.5%) adults and 18 (4.4%) nymphs were found positive for Borreliae. This study discusses the importance of I. ricinus ticks in the role of Lyme borreliosis in Slovenia.

Animals↗
PubMed1983

Ultrastructural studies on sporogony of Babesia microti in salivary gland cells of the tick Ixodes dammini.

Tick larvae were permitted to feed on infected hamsters and then allowed to molt. Nymphs were examined just prior to feeding on uninfected hamsters or at timed intervals thereafter. Invasion of the salivary gland by B. microti occurs before feeding of the nymph begins, and development of the parasite is further stimulated by feeding. The sporoblast forms a massive multinucleated meshwork which ramifies throughout the large host cell. No separation of the meshwork into multiple subdivisions, termed "cytomeres" by other workers, has been detected. Instead the specialized organelles characteristic of sporozoites, namely micronemes, rhoptries, and segments of double membrane appear in the meshwork itself and gradually become organized into sporozoite anlagen which protrude from its surface. At the same time the meshwork shortens and thickens giving rise to large compact undifferentiated bodies whose surface is also studded with sporozoite anlagen. Sporozoites thus originate either from the meshwork or from the undifferentiated bodies. In either case large lobate nuclei send projections into the anlagen as they protrude from the surface of the sporoblast. In a final step the mature sporozoites arise by simultaneous nuclear and cytoplasmic divisions. There is no separate stage of schizogony and the process is one of true budding.

Animals↗
PubMed1988

Acquired resistance in rabbits to immature stages of Rhipicephalus evertsi evertsi.

Host resistance, accompanied by demonstrable anti-tick antibodies, developed in groups of rabbits that were infested repeatedly with different numbers of Rhipicephalus evertsi evertsi larvae. This resistance was associated with a drastic reduction in the number of ticks that attached but not in the ability to feed and moult by immatures already established on the hosts. Furthermore, resistance reduced to below 50% the proportion of nymphs which emerged from the larvae applied to the three host groups. Nymphs weighing 5-9.9 and 15-19.9 mg moulted to give mainly males or females respectively. The proportion of males and females which moulted from the remaining weight categories was variable. Anti-tick antibodies were detected by enzyme-linked immunosorbent assay as early as 7 days after primary infestation in all hosts. The titres plateaued after the second challenge and declined drastically during the fifth infestation. No appreciable differences were observed in the antibody responses stimulated by different challenge regimens.

Animals↗
PubMed1989

Repetitive detection by immunoblotting of an integumental 25-kDa antigen in Ixodes ricinus and a corresponding 20-kDa antigen in Rhipicephalus appendiculatus with sera of pluriinfested mice and rabbits.

Mice were pluriinfested with nymphs and rabbits, with adult Ixodes ricinus. As determined by immunoblotting, greater than 50% of sera from these animals reacted against a tick antigen with a molecular weight of 25 kDa, which was detected in total extracts of partially fed I. ricinus females and in tick integumental extract. It was also found in engorged nymphs but was absent from larvae. Sera of I. ricinus-infested rabbits and mice or of rabbits infested with Rhipicephalus appendiculatus adults reacted with a 20-kDa antigen in total extracts of partially fed R. appendiculatus females and the integument of this species.

Animals↗
PubMed1989

Monitoring of naturally acquired and artificially induced immunity to Amblyomma variegatum and Rhipicephalus appendiculatus ticks under field and laboratory conditions.

The ability of rabbits, goats and cattle to acquire immunity to the ixodid ticks Amblyomma variegatum and Rhipicephalus appendiculatus was studied under laboratory and field conditions. Rabbits were successfully immunized with crude salivary gland extract (SGE) and midgut extract (ME) obtained from flat or partly fed female R. appendiculatus ticks. The lowest numbers of larvae were produced by females fed on rabbits immunized with unfed midgut extract. Similar reductions in larval production could be induced after three infestations of rabbits with adult R. appendiculatus. Also, successive feedings of nymphs of R. appendiculatus on rabbits resulted in significantly reduced engorgement weights. Skin testing with SGE induced delayed-type hypersensitivity reactions, which could be correlated with immunity to R. appendiculatus in rabbits. Moreover, circulating antibodies were detected in rabbits with an ELISA using SGE of R. appendiculatus. Immunity to A. variegatum nymphs could be induced in rabbits by repeated infestations, but this failed in goats. Immunization of goats with midgut extract from adult A. variegatum did not protect against subsequent nymphal challenge, but strong skin reactions were noticed when adults ticks fed on immunized goats. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of SGE and ME from A. variegatum revealed the presence of 48 protein bands in SGE and 29 bands in midgut extract. Western blotting employing serum from a rabbit immune to R. appendiculatus recognized a number of bands in SGE from R. appendiculatus, but also in SGE of A. variegatum. Immunity acquired by cattle to ixodid tick infestations under field conditions was monitored by skin testing with SGE and western blot analysis. In general, cattle with the lowest tick numbers manifested the strongest delayed-type hypersensitivity responses. Finally, western blot analysis employing sera from tick-infested and tick-naive cattle could not be related to actual immune status.

Animals↗
PubMed1994

RH-5849, a nonsteroidal ecdysone agonist, does not mimic makisterone-A in Dysdercus koenigii.

The response of final instar nymphs of Dysdercus koenigii to topical application of the non-steroidal ecdysone agonist, RH-5849, was dose dependent. The candidate compound produced mortality even at moderate doses, but precocious adult development was not observed. Similar results were obtained after oral administration or injection. Conversely, injections of makisterone-A (the principal moulting hormone of Dysdercus) into 5th instar nymphs resulted in precocious adult development within 4 days. We conclude that RH-5849 does not mimic makisterone-A, as is the case with ecdysone, and that toxicity is mediated instead through non-endocrine targets in this insect species.

Animals↗
PubMed1994

The effect of feeding immature Karoo paralysis ticks Ixodes rubicundus (Acari: Ixodidae) on the metabolic rate of the rock elephant shrew.

The effect of feeding immature Karoo paralysis ticks (Ixodes rubicundus) on the resting metabolic rate (RMR) of their principal natural host, the rock elephant shrew (Elephantulus myurus), was investigated under laboratory conditions. The elephant shrews were artificially infested with numbers of ticks simulating natural burdens. The RMR of the elephant shrews was quantified by measuring the oxygen consumption in an open through-flow system. The RMR of hosts infested only with larvae did not differ from that of the control group. Those infested with nymphs, or nymphs and larvae, had significantly lower RMR's compared to the control animals. There were no signs of paralysis in any of the infested hosts.

Animals↗
PubMed1997

Theileriosis of sheep and goats in China.

Theileriosis is an important disease of sheep and goats in West China. Its main distribution includes Qinghai, Gansu, Ningxia, Inner Mongolia, Shaanxi and Sichuan. The epidemic period is from late March to July with April-May being the peak months. This is the period of most intensive tick attack by Haemaphysalis qinghaiensis (77.2-99.24%) during the year. It has been proved that the nymphs and adults, which develop from larvae and nymphs engorged on infected sheep or goats can transmit the pathogen. Experimental infections revealed the incubation period, clinical signs and the pathogen's morphological characteristics. The disease was more serious in lambs and exotic adult animals than native adult animals. The sickness rates of lambs, exotic and native adult animals were 78-85%, 41% and 9% respectively; death rates were 81.41%, 62.5% and 65% respectively. Clinical prophylaxis, chemical therapy and destruction of ticks have been carried out with antiparasitic compounds to control the disease since 1982. Experiments demonstrated that the curative rate was up to 76-86%, but no satisfactory prophylactic methods were found.

Animals↗
PubMed1997

Ticks and tick-borne bovine piroplasmosis in the Southmountain pasture of Hunan Province, China.

Ticks and tick-borne bovine piroplasmosis is one of the most serious diseases affecting cattle bred in the Southmountain pasture of Hunan province. An investigation carried out from 1992 to 1995 showed that Theileria sergenti was found in the blood of disease-stricken cows. Ticks were collected from cattle. The species concerned (three genera and four species of ticks: Haemaphysalis vietnamensis, Haemaphysalis longicornis, Ixodes sinensis and Boophilus microplus) were identified by microscopy and their numbers recorded every month. Because H. longicornis is a three-host tick, with the larvae, nymphs and adults all infesting cows and seasonal fluctuations in nymphs and adults correlating with theileriosis outbreaks, this tick species was a potential vector of T. sergenti. Epidemiological studies indicated that this disease usually occurred in summer or autumn. The disease attacked calves from May to August reaching a peak in June or July (as happened from 1992-1994). In cattle, the disease occurred from June to September with a peak in September. The following pathological lesions were observed: haemorrhages were seen in the subcutaneous tissues and serosa, in the intestinal mucosa and the mesenteric lymph nodes. The surface of the abomasum looked like a piece of red cloth. The liver was enlarged, its edge blunt and curled over. The gall bladder was filled with tawny coloured bile. The spleen was enlarged and dark brown. The heart was enlarged with numerous haemorrhagic foci in the auricle. The blood clotted incompletely. Sick cattle were treated with Berenil and imidocarb and the death rate was reduced from 26% to 5.9%.

Animals↗
PubMedDate not supplied

First isolation and characterisation of Borrelia garinii, agent of Lyme borreliosis, from Irish ticks.

Nymphal Ixodes ricinus, the tick vector of Lyme borreliosis, were collected from the edges of paths in Muckross Demesne, Killarney National Park, Co. Kerry, Ireland. Examination of some of these nymphs by indirect immunofluorescence showed an infection prevalence of 12% with Borrelia burgdorferi sensu lato, the spirochaete agent of Lyme borreliosis. Gerbils (Meriones unguiculatus) were infected by infesting them with other nymphs from the same batch. Subsequently uninfected laboratory larvae were applied to the gerbils and the contents of the resulting infected engorged ticks were then placed in media and the spirochaetes cultured. The spirochaetes were identified as B. burgdorferi sensu lato by indirect immunofluorescence using monoclonal antibodies and they were further characterised by polymerase chain reaction and pulsed-field gel electrophoresis. Both of these latter techniques showed that spirochaetes in all samples belonged to the genomic species, Borrelia garinii.

Animals↗
PubMed1999

Effects of heavy metals (Hg2+, cd2+, Pb2+) during the embryonic development of acridid grasshoppers (Insecta, caelifera)

Heavy metals present in the soil get differently accumulated in organisms and show different rates of toxicity at different stages of the life cycle of any organism living there. To see whether such toxicants get accumulated during the embryonic development and/or change the normal developmental processes of organisms exposed to heavy metals, freshly laid eggs and egg pods of two acridids, Aiolopus thalassinus and Eyprepocnemis plorans, were tested against different concentrations of Hg2+, Cd2+, and Pb2+. At increasing Hg2+ concentration in the substrate, an increased egg mortality and reduced nymphal hatching in A. thalassinus were observed, yet no change in the normal duration for embryonic development was noticed. A higher hatching rate of E. plorans nymphs than that of A. thalassinus could possibly be due to the higher tolerance, contributed by larger egg volume and thicker foam around the egg pods of the former. Treated concentrations of Hg2+ could be of sublethal (0.121 &mgr;g Hg2+/g substrate) to lethal (0.605 &mgr;g and more Hg2+/g substrate) doses. The mortality of eggs did not always increase with increasing substrate concentration of Cd2+ and Pb2+, and the hatching rates of both grasshopper species in many cases were even higher than that in the control. Still, lower accumulation factors of Cd2+ and Pb2+ than that of Hg2+ were found coupled with not increased mortality. The tested concentrations of Cd2+ and Pb2+ in the substrates, thus, could be of subacute doses. The embryonic development was found prolonged due to Cd2+ and Pb2+. During parallel egg and egg pod treatments, higher metal concentrations were found in not developed eggs than that in fresh nymphs hatching from the same substrates. This indicated the role of foam around the egg pods as "protective filter" against the toxic substances in the soil.

Journal Article↗