Showing papers in "Journal of Medical Entomology in 1989"
TL;DR: A diagrammatic couplet key to the adults of the six genera and 27 species of Ixodidae found in the eastern portion of the United States are presented.
Abstract: Six genera and 27 species of hard ticks (Ixodidae) currently are recognized in the United States east of the Mississippi River as follows: Amblyomma (4 species), Boophilus (1), Dermacentor (3), Haemaphysalis (2), Ixodes (16), and Rhipicephalus (1). We present a diagrammatic couplet key to the adults of the six genera and 27 species of Ixodidae found in the eastern portion of the United States.
346 citations
TL;DR: Differences observed in the rate of development were sufficient to alter postmortem interval estimates based on larval development in decomposing human tissues by up to 24 h.
Abstract: Larvae of the flesh fly, Boettcherisca peregrina (Robineau-Desvoidy), were reared on the tissue of rabbits to study the effects of cocaine and benzoylecognine on development rates. The rabbits were given 35, 69, and 137 mg of cocaine through cardiac puncture. From hours 30 to 70, larvae developed more rapidly on tissue containing cocaine, benzoylecognine, or both, from rabbits injected with 69 and 137 mg of cocaine than on tissue from rabbits injected with 35 mg of cocaine or no cocaine. Total development times required for pupation and adult eclosion were shortened correspondingly. Differences observed in the rate of development were sufficient to alter postmortem interval estimates based on larval development in decomposing human tissues by up to 24 h.
115 citations
TL;DR: Aedes japonicus (Theobald) was evaluated for competence as a vector of Japanese encephalitis virus and for its ability to transmit the virus vertically to its F1 larvae.
Abstract: Aedes japonicus (Theobald) was evaluated for competence as a vector of Japanese encephalitis virus and for its ability to transmit the virus vertically to its F1 larvae. Ae. japonicus supported the growth of the virus at 20 and 28 degrees C after feeding on a virus-blood mixture of 10(6.2) plaque forming unit (PFU)/ml. This species was able to transmit the virus to suckling mice after feeding on a virus-blood meal (10(6.2) PFU/ml) or a viremic chick (10(3.7) PFU/ml). Vertical transmission of the virus in Ae. japonicus was demonstrated with a minimum infection rate of 0.7%.
115 citations
TL;DR: Strains of A. albopictus from northern Asia and North America showed higher overwintering survival rates than strains from tropical Asia, Hawaii, and Brazil; strains from Indiana had greater ability to overwinter than those from Texas, Louisiana, and Florida.
Abstract: Eggs of 12 strains of Aedes albopictus (Skuse), two strains of A. aegypti L., and one strain of A. triseriatus (Say) were tested for ability to overwinter at three outdoor locations in Indiana. Some survival of A. albopictus eggs was observed during the winters of 1986–1987 and 1987–1988. A. triseriatus had greater overwintering ability than A. albopictus; A. aegypti did not survive at all locations. Prolonged cold-conditioning and photoperiodically induced diapause increased the overwintering ability of A. albopictus eggs. Strains of A. albopictus from northern Asia and North America showed higher overwintering survival rates than A. albopictus strains from tropical Asia, Hawaii, and Brazil; strains from Indiana had greater ability to overwinter than those from Texas, Louisiana, and Florida. Results are discussed in relation to the overwintering limits of this species in the United States.
113 citations
TL;DR: Results refute the contention that blood meals taken by diapausing Cx.
Abstract: Diapausing Culex pipiens L. females fed 10% sucrose for 7 d following eclosion contained significantly more lipids (P less than 0.05) than nondiapausing females reared and maintained at the same temperature (22 degrees C) but at a longer photophase (14:10 [L:D] instead of 9:15). Diapausing females with limited lipid reserves failed to increase their reserves after blood feeding. The average lipid content of 56 females tested decreased significantly (P less than 0.05) by day 6 after feeding and there was no correlation (r = -0.06) between lipid content at this time and original bloodmeal volumes of individual females. These results refute the contention that blood meals taken by diapausing Cx. pipiens result in fat body development when females are incubated at 18 degrees C during bloodmeal digestion. Diapausing Cx. pipiens with limited lipid reserves were unable to obtain sufficient energy from a single blood meal to survive extended hibernation. Although none became gravid, only 50% remained alive after 20 d in hibernation. In contrast, nonblood-fed females fed only 10% sucrose for 7 to 10 d before being placed in hibernation on a water diet survived for 6 mo with only 50% mortality. There was no evidence for gonotrophic dissociation. Failure of blood-fed, diapausing females to initiate vitellogenesis was correlated with the significantly smaller blood meals taken by most diapausing females and not with hypertrophy of the fat body or temperature during digestion.
107 citations
TL;DR: Findings suggest that S. occidentalis, although an important host of I. pacificus immatures, may be less important as a source for infecting ticks with B. burgdorferi, and the relationship of immature western black-legged ticks to the western fence lizard is investigated.
Abstract: The relationship of immature western black-legged ticks, Ixodes pacificus Cooley and Kohls, to the western fence lizard, Sceloporus occidentalis Baird and Girard, and to the Lyme disease spirochete, Borrelia burgdorferi, was investigated in chaparral and woodland-grass habitats in northern California from 1984 to 1986. Immature ticks were found on lizards in spring and summer, but the prevalence and abundance of ticks on this host were considerably greater in spring. The peak of larval abundance preceded that of nymphs by several weeks, but there was considerable seasonal overlap between these parasitic stages. Larvae and nymphs attached primarily to the lateral nuchal pockets of lizards in chaparral (99.5%) and woodland-grass (91.8%). The numbers of larvae infesting lizards in spring fit the negative binomial distribution in woodland-grass but not in chaparral; insufficient data precluded similar analyses for nymphs. Tick loads did not differ significantly with respect to age or gender of the lizard. Spirochetal infection rates (range, 0-3.7%) in I. pacificus immatures were comparable in both habitats and were similar to those reported previously for adults of this tick. Overall, 1 (0.9%) of 117 larvae and 10 (1.8%) of 552 nymphs were infected with spirochetes resembling B. burgdorferi. Spirochetes were not observed in blood smears prepared from 261 wild-caught lizards, including five lizards fed upon by infected ticks at the time of collection. These and other findings suggest that S. occidentalis, although an important host of I. pacificus immatures, may be less important as a source for infecting ticks with B. burgdorferi.
105 citations
TL;DR: It is concluded that no clear-cut displacement occurred in mixed experimental populations of Ae.
Abstract: Interactions among the larvae of Aedes aegypti (L.), Ae. albopictus (Skuse), and Ae. triseriatus (Say) were studied in trispecific and bispecific mixed populations under laboratory and field conditions. Competitive stress (as evidenced by the average time to first, 50, and 75% pupation and the total pupation periods for mixed populations of each species in comparison with their single species controls) was more pronounced in mixed cultures reared in glass jars in the laboratory than in tires under field conditions. In the laboratory, the larval development of Ae. aegypti reared together with Ae. albopictus or Ae. triseriatus, or both, larvae was accelerated significantly. Conversely, the time to pupation for Ae. albopictus and Ae. triseriatus was delayed when reared with Ae. aegypti. However, the average wing length of female Ae. albopictus and Ae. triseriatus was greater in the mixed cultures than in single species cultures. These data indicated that the effect of intraspecific competition was greater than interspecific competition. Adequate food and higher temperature appeared to promote rapid development and higher survival of the immature stages of the three Aedes species in tires placed in the field. In general, Ae. triseriatus larvae required a longer period for larval development and had greater larval mortality than either Ae. aegypti or Ae. albopictus. In mixed populations of Ae, albopictus and Ae. aegypti in the jars and food-rich tires, the periods needed to attain first, 50, and 75% cumulative pupation were not significantly different than in single species controls. We conclude that no clear-cut displacement occurred in mixed experimental populations of Ae. aegypti and Ae. albopictus.
103 citations
TL;DR: Results do not suggest that the U.S Ae.
Abstract: Mosquito abatement workers in Houston, Tex., and New Orleans, La., have observed that the recent introduction of Aedes albopictus (Skuse) has been accompanied by a decline and virtual disappearance of Ae. aegypti (L.). This suggests competitive displacement but contradicts the direction of displacement observed in native habitats of Ae. albopictus . The paper reports a series of laboratory studies on competition between U.S. strains of the two species. Larval survivorship, size, and development time were monitored in increasing densities of pure and mixed cultures of the two species under limited and optimal diets. Oviposition preferences were examined by offering gravid females cups containing first or fourth instars of either species. Ethological isolation was studied by simultaneously offering virgin females of one species to males of both species and monitoring courtship behavior as well as rates of oviposition, percentage of hatch, and embryonation. The results of the larval competition studies suggest that interspecific competition increased development time only slightly and had no effect on survival of Ae. albopictus . Competition increased survival in Ae. aegypti . Size of both species was influenced by interspecific competition, but the magnitude and direction of the effect was inconsistent between strains and diets such that neither species emerged consistently larger. The results of the oviposition study indicated a higher fecundity in Ae. aegypti but otherwise demonstrated that both species oviposit without regard to the presence, age, or species of larvae in the oviposition container. The ethological isolation tests demonstrated that Ae. aegypti males were more sexually aggressive than males of Ae. albopictus . However, Ae. albopictus females placed with increasing densities of Ae. aegypti males demonstrated no decrease in rates of oviposition, and eggs laid showed equal rates of hatch and embryonation. In general, the results do not suggest that the U.S. Ae. albopictus population is inherently more competitive in the laboratory than Ae. aegypti . Other reasons for the observed decline in Ae. aegypti in the United States are discussed.
88 citations
TL;DR: The effectiveness of the canopy trap for female Tabanidae was increased significantly when l-octen-3-ol was used as an attractant and there was a significant increase in number of tabanids captured by traps with octenol and with dry ice plusOctenol.
Abstract: The effectiveness of the canopy trap for female Tabanidae was increased significantly when l-octen-3-ol was used as an attractant. There was a threefold increase in the number of tabanids captured by traps with octenol (12.8 ± 2.1 females/trap) versus unbaited traps (3.7 ± 1.2 females/trap), and with dry ice plus octenol (72.1 ± 9.7 females/trap) versus traps with dry ice alone (24.7 ± 2.6 females/trap). There was also a significant increase in number of species in collections from traps with dry ice plus octenol (9.8 ± 0.9 species/trap) versus traps with dry ice alone (6.2 ± 0.9 species/trap). Tabanus molestus Say constituted 70% of the 1,038 tabanids collected.
78 citations
TL;DR: The distributions of Ixodes dammini Spielman, Clifford, Piesman, and Corwin and Lyme disease spirochetes were studied on Fire Island, N.Y, and the proportion of ticks infected did not differ significantly among habitats.
Abstract: The distributions of Ixodes dammini Spielman, Clifford, Piesman, and Corwin and Lyme disease spirochetes were studied on Fire Island, N.Y. Adult ticks were more common in high-shrub habitats (shrubby vegetation ≥1 m high) than in grassy and lowshrub habitats (vegetation <1 m) in spring and fall. In the fall, adults were also common in the woods. Adults were more abundant on narrow trails than in nearby vegetation. During the summer, questing nymphs and larvae were far more common in the woods (primarily in leaf litter) than in open grass-shrub habitats. In contrast, the number of nymphs and larvae per white-footed mouse did not differ among habitats, suggesting that mice play a role in tick dispersal. CO2 trap captures of nymphs on trails were not significantly greater than off trails. Most collections of larvae and nymphs had more than one tick, whereas most samples of adults had only one individual. Borrelia burgdorferi infection rates in free-living ticks were 38% ( n = 121) to 50% ( n = 32) in adults, 32% in nymphs ( n = 184), and 0% in larvae ( n = 15). The proportion of ticks infected did not differ significantly among habitats. Therefore, during the spring and fall, activities that take place in high-shrub areas or in the woods (e.g., landscaping, trail or brush clearing) involve a high risk of exposure to adult ticks infected with Lyme disease. In late spring to early summer, any activity involving close contact with leaf litter (e.g., playing in the leaves, gathering leaves for camp bedding) results in a high risk of exposure to infected nymphs.
70 citations
TL;DR: The sudden appearance of numerous documented bite cases indicates that either the species is becoming more anthropophilic in this area or than an introduction of a more human adapted population of R. sanguineus has occurred.
Abstract: Throughout most of its range, the brown dog tick, Rhipicephalus sanguineus (Latreille), prefers dogs as a host, but human bites occasionally occur in the Mediterranean region and Central America; historically, this species has rarely bitten humans in the United States. A focus of 15 human bite cases by this tick is reported from four Air Force bases located within 200 miles of each other in north central Texas and southwestern Oklahoma. The sudden appearance of numerous documented bite cases indicates that either the species is becoming more anthropophilic in this area or than an introduction of a more human adapted population of R. sanguineus has occurred. The species is a known reservoir and vector of Ehrlichia canis, the causative agent of canine ehrlichiosis in dogs. The presence of an anthropophilic strain of R. sanguineus in the United States may lead to increased exposure to E. canis and thus an increase in the incidence of human ehrlichiosis.
TL;DR: Ticks of eight medium-sized mammal species were studied in an area of endemic Lyme disease in Westchester County, N.Y., from 1 April 1984 to 31 March 1985 and the prevalence of I. dammini on medium- sized mammals in southern New York may influence the epizoötiology of Lyme disease.
Abstract: Ticks of eight medium-sized mammal species were studied in an area of endemic Lyme disease in Westchester County, N.Y., from 1 April 1984 to 31 March 1985. Most (81%) of the 266 total mammal captures were raccoon, Procyon lotor (L.) (47%), opossum, Didelphis virginiana (Kerr) (19%), and striped skunk, Mephitis mephitis Schreber (15%); these host species accounted for 91% of the 1,519 ticks collected. Although the total number of ticks was rather evenly distributed among these mammals, species composition of ticks on each host species differed markedly. Ixodes dammini Spielman, Clifford, Piesman, and Corwin was the most abundant tick species and accounted for 45% (690) of the total ticks collected. Immatures were most prevalent (56%) on opossum, and nearly all (86%) adults were found on this host species. I. cookei Marx was second in abundance (34%) and was most prevalent (60%) on skunk. I. texanus Banks and Dermacentor variabilis (Say) were less abundant (less than 20% collectively) and were most prevalent on raccoon. I. dentatus Marx on eastern cottontail, Sylvilagus floridanus (Allen), and I. marxi Banks on gray squirrel, Sciurus carolinensis Gmelin, were least abundant (less than 2% collectively). The prevalence of I. dammini on medium-sized mammals in southern New York may influence the epizootiology of Lyme disease.
TL;DR: A key to the adult of 24 species belonging to six subgenera is presented and it is proposed that H. wellingtoni Nuttall & Warburton, 1908, be placed in the subgenus Kaiseriana.
Abstract: Specimens of the genus Haemaphysalis collected in Thailand were examined, and a key to the adult of 24 species belonging to six subgenera is presented. We propose that H. wellingtoni Nuttall & Warburton, 1908, be placed in the subgenus Kaiseriana; H. obesa Larrousse, 1925, be moved from Segalia to Kaiseriana; and that H. cornigera Neumann, 1897, be removed from the species list of Thailand.
TL;DR: A case of urogenital myiasis in a patient with transverse myelitis is reported from Imphal, Manipur, India, the first known case of urinary myiasis caused by M. scalaris in India.
Abstract: A case of urogenital myiasis in a patient with transverse myelitis is reported from Imphal, Manipur, India. The larvae of Megaselia scalaris Lowe were recovered repeatedly from the urine of the patient and were reared to adult to facilitate identification. This is the first known case of urinary myiasis caused by M. scalaris in India.
TL;DR: There was no increase in the concentrations of host IgG in the hemolymph of the soft ticks during the first week following the blood meal, and the potential contribution to the resistance of hosts against ticks by host antibodies that cross into the tick hemocoel is discussed.
Abstract: A radioimmunoassay was used to measure the concentration of host immunoglobulin G (IgG) in the hemolymph of female hard and soft ticks. Hyalomma excavatum Koch, Rhipicephalus sanguineus Latreille, Ornithodoros tholozani (Laboulbene and Megnin), and O. moubata (Murry) were fed on rabbits immunized with ovalbumin; Argas persicus (Oken) was fed on chickens immunized with cytochrome 'C.' At 24 h after feeding, the concentration of antiovalbumin IgG in the hemolymph was 7 micrograms/ml for H. excavatum, 5 micrograms/ml for R. sanguineus, and 0.15 micrograms/ml for O. moubata; the percentage of intact IgG molecules was 30, 44, and 100%, respectively. Host IgG was not detected in the hemolymph of O. tholozani and A. persicus. There was no increase in the concentrations of host IgG in the hemolymph of the soft ticks during the first week following the blood meal. The potential contribution to the resistance of hosts against ticks by host antibodies that cross into the tick hemocoel is discussed.
TL;DR: The micropylar collar in Ae.
Abstract: Complete descriptions, including details of the micropylar apparatus and outer chorion at the anterior and posterior poles and on the dorsal surface, are given for the eggs of Aedes (Stegomyia) albopictus Skuse and Ae. (S.)aegypti (L.). The egg of Ae. (Howardina) bahamensis Berlin, the first of this subgenus to be examined with the electron microscope, is described for the first time. Certain characters may be useful for differentiating eggs of these three species under a stereomicroscope. The substantially greater egg length in Ae. bahamensis alone separates it from the other two species, at least in the laboratory populations studied. The micropylar collar in Ae. aegypti clearly differentiates it from the other two. Further examination of mixed groups of eggs is needed to determine whether fine structural differences in the outer chorion can be correlated with consistent differences in the stereomicroscopic image.
TL;DR: It is concluded that Mesocyclops may prove useful for biological control of Anopheles by observing to prey readily upon first-instar An.
Abstract: Forty-two ground water sites on the Pacific and Atlantic coasts of Colombia were sampled quantitatively with a plankton net to assess the abundance of mosquito larvae and associated fauna. Many of the sites contained substantial numbers of Anopheles albimanus Wiedemann larvae, but the larvae were virtually absent wherever there were large populations of the copepods Mesocyclops venezolanus, M. longisetus, or M. aspericornis. Mesocyclops were observed to prey readily upon first-instar An. albimanus larvae in the laboratory, but smaller genera of cyclopoid copepods did not kill An. albimanus larvae. We conclude that Mesocyclops may prove useful for biological control of Anopheles.
TL;DR: Because I. dentatus feeds solely on rabbits, and these hosts may be extraordinarily abundant in nature, this tick provides potential for a hidden enzoötic cycle of natural Lyme disease transmission.
Abstract: We compared the development of the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt and Brenner, in subadult rabbit-feeding Ixodes dentatus Marx with that in mouse-feeding I. dammini Spielman, Clifford, Piesman and Corwin. Rabbits were infected with spirochetes by the bites of I. dammini that had been infected naturally in a zoonotic site. Larval ticks of both species were permitted to engorge simultaneously on each of these infected hosts. Spirochetes were present in the guts of about half of the resulting nymphal I. dentatus and most of the I. dammini that developed. An experimentally infected nymphal I. dentatus, in turn, infected a rabbit. Because I. dentatus feeds solely on rabbits, and these hosts may be extraordinarily abundant in nature, this tick provides potential for a hidden enzootic cycle of natural Lyme disease transmission.
TL;DR: The Oviposition behavior of the treehole mosquito Aedes triseriatus (Say) was studied by counting the eggs laid in 300 oviposition traps weekly for one season (May-October) in Illinois, indicating that females were laying clumps of eggs in an overdispersed manner.
Abstract: The oviposition behavior of the treehole mosquito Aedes triseriatus (Say) was studied by counting the eggs laid in 300 oviposition traps weekly for one season (May-October) in Illinois. Eggs were aggregated spatially among traps each week, and temporally among weekly samples and for individual traps over weekly counts. Aggregation could be associated with a nonrandom dispersion pattern of oviposition events and with the oviposition of 20-60 eggs per event. Thus, females were laying clumps of eggs in an overdispersed manner. The greatest number of eggs was found in late July when prevalence (proportion of traps with eggs) and intensity (number of eggs per positive trap) peaked simultaneously. Intensity also peaked in May and prevalence peaked in mid-June and early September. When traps from which eggs were removed each week were compared with traps in which eggs were allowed to accumulate, prevalence was naturally higher in the latter group. However, the intensity of eggs was similar in both groups, indicating that more eggs were laid in traps from which eggs were removed. Thus, the presence of eggs on oviposition surfaces was associated with a decrease in further oviposition.
TL;DR: It is indicated that, in addition to the chemical factors associated with the food substances, the physiological and environmatal conditions of the larvae play an important role in regulating the ingestion rate of suspended particles by mosquito larvae.
Abstract: Relative ingestion rates of mosquito larvae, as indicated by the number of substrate-filled gut segments per unit time, were determined for Culex tarsalis Coquillett, Aedes aetypti L., and Anopheles albimanus Wiedemann. Among the three species, Ae. aegypti larvae were the most rapid feeders. F50 (median time for complete repletion of 50% of the larvae) was 61, 42, and 100 min for the three species feeding on a wheat flour suspension, respectively. Food particles with nutritive values (dried yeast, wheat flour, fishmeal, or dried blood) were ingested faster than inert particles (kaolin, talc, chalk, or charcoal). The addition of aqueous yeast extracts containing phagostimulants accelerated the ingestion of inert particles. Increasing the concentration of inert particles did not increase ingestion rates. Larval age, water temperature, and starvation, but not larval density, influenced rates of ingestion. Younger instars were more rapid feeders than older instars. First instars of the three species filled their guts with wheat flour approximately two times faster than fourth instars. Increasing water temperature from 18 to 31 degrees C accelerated wheat flour ingestion by fourth instars of Cx. tarsalis, Ae. aegypti, and An. albimanus by factors of 1.9, 1.5, and 1.7, respectively. After starvation for 12 h, fourth instars of Cx. tarsalis and Ae. aegypti increased ingestion of wheat flour about 1.6 and 1.8 times, respectively. In contrast, starvation of An. albimanus larvae for the same period resulted in decreased wheat flour ingestion by 2.2 times when compared with unstarved larvae. These results indicare that, in addition to the chemical factors associated with the food substances, the physiological and environmatal conditions of the larvae play an important role in regulating the ingestion rate of suspended particles by mosquito larvae.
TL;DR: The resulting bimodal peak in autumn and spring appears to reflect temperature-induced activity of the same cohort and not different generations, and it is suggested that adult abundance, measured independently of ambient temperature, may be an accurate indicator of survival.
Abstract: Mark-recapture studies demonstrated that adult Ixodes dammini Spielman, Clifford, Piesman, and Corwin in southern New York successfully overwinter and resume active host-seeking in the spring. Thus, the resulting bimodal peak in autumn and spring appears to reflect temperature-induced activity of the same cohort and not different generations. Adult tick abundance in the field was monitored by counting the number of ticks collected by a domestic dog on routine walks and correcting for the effects of temperature on tick activity. It is suggested that adult abundance, measured independently of ambient temperature, may be an accurate indicator of survival. The field tick abundance curve was negatively exponential ( y = e(4.26–0.12 x ) and significantly different from the survival curve for ticks maintained in the laboratory, which displayed a constant mortality rate ( y = −3.7 x + 105.5). Body size influenced male survival during the winter, whereas female survival was independent of body size. Greater male mortality in fall and winter resulted in a lower sex ratio in spring.
TL;DR: Three laboratory colonies of the argasid tick Onithodoros moubata porcinus van der Merwe were started from collections made in 1983 at three different sites in Zimbabwe and showed that mortality rates were considerably higher among the infected ticks, probably involved in the clearance of ASF virus from tick populations that are not subjected to reinfection.
Abstract: Three laboratory colonies of the argasid tick Onithodoros moubata porcinus van der Merwe were started from collections made in 1983 at three different sites in Zimbabwe. All of the colonies contained ticks infected with African swine fever (ASF) virus that was readily transmitted by bite to domestic pigs. Although they were maintained on virus-free pig blood, ASF virus infections persisted in the colonies for at least 1 yr. Despite the fact that ASF virus passes transstadially, sexually, and transovarially in this tick species sometime during the following year, the virus disappeared from the colonies. Studies comparing fecundity in infected and uninfected lots of O. moubata porcinus showed that mortality rates were considerably higher among the infected ticks. A similar study with Ornithodoros erraticus Lucas, a tick that harbors and transmits ASF virus on the Iberian Peninsula, gave essentially the same results. This is probably a factor involved in the clearance of ASF virus from tick populations that are not subjected to reinfection. How this information may be applied in the eradication of African swine fever in Portugal and Spain is discussed.
TL;DR: Of eight viruses isolated from 28,909 female Aedes normanensis collected from the north of Western Australia, two were identified as Murray Valley encephalitis virus and six as Ross River virus, the first confirmed isolations of this virus from an Aedes species.
Abstract: Of eight viruses isolated from 28,909 female (643 pools) Aedes normanensis collected from the north of Western Australia, two were identified as Murray Valley encephalitis virus and six as Ross River virus. The two isolates of Murray Valley encephalitis virus represent the first confirmed isolations of this virus from an Aedes species. The possible implications of these findings with regard to virus survival mechanisms during the dry season are discussed.
TL;DR: A comprehensive computer model was developed for simulation of the population dynamics of the American dog tick, Dermacentor variabilis Say, in North America and produced acceptable values for initial population growth rate and generation time, as well as realistic equilibrium population densities and seasonal activity patterns.
Abstract: A comprehensive computer model was developed for simulation of the population dynamics of the American dog tick (ADT), Dermacentor variabilis Say, in North America. The model simulates the effects of major environmental variables, such as ambient temperature, saturation deficit, kind of habitat, and host density, on ADT population dynamics in ecosystems with small mammals as hosts for immature ticks and medium-sized mammals or domestic dogs as hosts for adult ticks. General validity of the model was established by comparisons between simulated and actual population densities for a series of years at locations in Virginia, Maryland, and Massachusetts using actual weekly weather data for each year as a model input. Using historical-average weather data for 11 locations within the known geographic range of ADT and 3 locations outside this range, the model produced acceptable values for initial population growth rate and generation time, as well as realistic equilibrium population densities and seasonal activity patterns. This model can be used as a framework for additional modeling efforts to simulate the transmission of Rocky Mountain spotted fever and to study various strategies for management of ADT populations.
TL;DR: Seasonal and habitat influences on the egg-laying activity of four species of Culex were compared in south Florida using jar- and vat-type oviposition traps, and nigripalpus was the dominant species in the summer and fall, and Cx.
Abstract: Seasonal and habitat influences on the egg-laying activity of four species of Culex were compared in south Florida using jar- and vat-type oviposition traps. Egg rafts of Culex nigripalpus Theobald, Cx. quinquefasciatus Say, and Cx. salinarius Coquillett were collected in every month of the year, but rafts of Cx. restuans Theobald were absent during spring and summer. Cx. nigripalpus was the dominant species in the summer and fall, and Cx. quinquefasciatus and Cx. salinarius peaked during the winter and spring. Cx. restuans oviposited most rafts in the fall (98.4%). Most Cx. nigripalpus egg rafts were laid in vats (88.5%), and most Cx. quinquefasciatus egg rafts were deposited in jars (58.7%). Fewer Cx. quinquefasciatus rafts were found in a wooded area (32.4%) with a dense undergrowth than in a more open area (67.6%), but Cx. nigripalpus showed no ovipositional preference between these two habitats. The number of rafts oviposited by all species was reduced during periods of rainfall.
TL;DR: It is concluded that the provisional standard for mattress dust of 0.6 mg guanine/g dust can be extended to dust from floor coverings and padded furniture, at least in western Europe, and the sensitization risk to patients allergic to house dust mites seems to be minimal.
Abstract: The development of a quick color reaction for guanine in house dust has made it possible to screen many homes for mite products of allergenic consequence. The azo dye methods are specific enough to be useful for the development of a sanitary standard. Comparing the guanine quantification results with mite counts and determinations of the mite antigen P1 ( Der p I) leads to the conclusion that the provisional standard for mattress dust of 0.6 mg guanine/g dust can be extended to dust from floor coverings and padded furniture, at least in western Europe. Below this level, the sensitization risk to patients allergic to house dust mites seems to be minimal.
TL;DR: White-tailed deer are biologically suitable hosts for B. annulatus, but significantly fewer ticks complete engorgement and those that complete Engorgement have reduced fecundity are found.
Abstract: White-tailed deer (Odocoileus virginianus L.) were evaluated as an alternate host for the cattle fever tick, Boophilus annulatus (Say). The total of adult female ticks recovered and associated reproductive parameters were compared between deer and bovine hosts. Significantly fewer ticks were recovered from deer than from cattle; this was attributed to the grooming behavior of the deer. The mean weight of ticks taken from deer (243.5 mg) was significantly less than that of ticks recovered from cattle (344.5 mg) with about 15% of the ticks from deer prematurely detached. Egg mass weight from the ticks recovered from deer (129.4 mg) was significantly less than that of ticks from cattle (172.1 mg). A significant difference was observed between the percentage hatch of the eggs of ticks from deer (63.1%) and ticks from cattle (76.7%). The index of reproduction was about 20 times greater for the ticks from the cattle than for the ticks from the deer. When the larval progeny of the ticks recovered from deer were reared on cattle, significantly fewer adult females were recovered than when larvae of ticks recovered from cattle were reared on cattle. This indicates a possible reduction in viability. All other parameters were comparable between the two groups. Thus, deer are biologically suitable hosts for B. annulatus, but significantly fewer ticks complete engorgement and those that complete engorgement have reduced fecundity.
TL;DR: Natural infections with Dirofilaria immitis (Leidy) in a population of mosquitoes and dogs and its antibodies in a human population were surveyed in Miki City, a rural area of Japan to reveal ecological features of this arthropod-borne zoönotic parasite.
Abstract: Natural infections with Dirofilaria immitis (Leidy) in a population of mosquitoes and dogs and its antibodies in a human population were surveyed in Miki City, a rural area of Japan, to reveal ecological features of this arthropod-borne zoonotic parasite. Micronfilaremic and amicrofilaremic infection rates in 190 dogs were 52.6 and 9.0%, respectively, as determined by the hematocrit centrifuge method and the indirect fluorescent antibody test. An enzyme-linked immunosorbent assay (ELISA) test for antibodies to D. immitis showed that almost all of 917 inhabitants had antibodies in varying degrees, indicating frequent exposure of this parasite to the human population. Among the six species of wild mosquitoes sampled from 1985 through 1987 by attraction with dry ice, Culex tritaeniorhynchus Giles was the most abundant in two sites and Aedes albopictus (Skuse) in another two sites. Filarial infections were found every year in Cx. tritaeniorhynchus and Ae. albopictus collected between July and September, as examined by ELISA for detecting larval antigens in mosquito homogenate, suggesting that these species are important natural vectors in this survey area.
TL;DR: Larvae of C. variipennis were associated positively with plankton volume, degree of animal access, and salinity, and negatively with slope and the pumping of the ponds for irrigation, and the pumped ponds tended to hold water continuously and have lower phytoplankton volumes and lower values of chemical oxygen demand.
Abstract: Culicoides variipennis (Coquillett) larvae were sampled five times over a 10-wk period in late summer in each of 26 dairy wastewater ponds in western Riverside County, Calif. Slope, degree of cattle access, prevalence of visible manure solids, salinity, chemical oxygen demand, plankton volume, and whether the ponds were pumped for irrigation were determined concurrently. Larvae of C. variipennis were associated positively with plankton volume, degree of animal access, and salinity, and negatively with slope and the pumping of the ponds for irrigation. High densities of larvae were found in shoreline mud in shallow, "evaporation bed" type ponds that were not pumped (means = 106 larvae per 30 ml). In contrast, pumped ponds were deeper, had steeper slopes, and supported lower densities of C. variipennis (means = 52 larvae per 30 ml). The pumped ponds tended to hold water continuously (more stable in time), and to have lower phytoplankton volumes and lower values of chemical oxygen demand. Rapid water level fluctuations in the pumped ponds also may have reduced C. variipennis density.
TL;DR: The female, male, nymphal instars, and larva of Ornithodoros puertoricensis Fox are redescribed from specimens collected in Haiti.
Abstract: The female, male, nymphal instars, and larva of Ornithodoros puertoricensis Fox are redescribed from specimens collected in Haiti. Data on host species and geographic distribution are also presented.