Biomedical subjects

R S Lane

Publications and source records attributed to R S Lane.

At least 55 records · Page 3Linked to original sources

PubMed1996

Risk of human exposure to vector ticks (Acari: Ixodidae) in a heavily used recreational area in northern California.

The risk of humans encountering vector ticks along hiking trails or in picnic grounds in a Lyme disease-endemic area was evaluated in a multipurpose recreational area (Tilden Regional Park) in the populous San Francisco Bay region of California. Four hillside hiking trails (two high-use, two low-use) were sampled by dragging and walking through low vegetation biweekly for one year; four heavily used picnic areas were sampled concurrently by dragging. Adults of three human-biting ticks were enumerated (n = 1,911) along all trials: Dermacentor occidentalis (63.6% of total), Ixodes pacificus (26.2%), and D. variabilis (0.2%). Subadults (n = 1,669) of D. occidentalis (0.06% of total) and two nonhuman-biters, D. albipictus (70.3%) and Haemaphysalis leporispalustris (29.7%), also were collected. Dragging yielded many more adult ticks than walking year-round for all trials. These methods were significantly correlated during periods of peak tick abundance, but the associations were not sufficiently strong or consistent to allow prediction of captures for either method based on the other. Adult ticks were distributed largely in clusters along the uphill sides of trails. Several adult ticks collected adjacent to trails were found to contain spirochetes identified with polyclonal antibodies as Borrelia burgdorferi (D. occidentalis, 0 of 861; D. variabilis, 2 of 126 [1.6%]; I. pacificus, 1 of 609 [0.2%]). Picnic areas produced low numbers of adult D. occidentalis and I. pacificus, which prohibited testing them for spirochetes. Two measures for evaluating risk were calculated, the encounter distance (= mean number of meters traveled before encountering a vector tick by either dragging or walking) and the mean number of spirochete-infected ticks encountered by these methods per kilometer of trial. These measures revealed that the risk of exposure to spirochete-infected adult ticks along trails was low year-round irrespective of usage, and risk was even lower in picnic areas. Future studies evaluating human exposure to vector ticks in recreational areas should incorporate, whenever possible, testing for multiple pathogens because most ixodid ticks that commonly bite people in the United States are capable of transmitting two or more microbial disease agents.

Animals↗

PubMed1995

Infection with a babesia-like organism in northern California.

BACKGROUND: Human babesiosis is a tick-transmitted zoonosis associated with two protozoa of the family Piroplasmorida: Babesia microti (in the United States) and B. divergens (in Europe). Recently, infection with an unusual babesia-like piroplasm (designated WA1) was described in a patient from Washington State. We studied four patients in California who were identified as being infected with a similar protozoal parasite. All four patients had undergone splenectomy, three because of trauma and one because of Hodgkin's disease. Two of the patients had complicated courses, and one died. METHODS: Piroplasm-specific nuclear small-subunit ribosomal DNA was recovered from the blood of the four patients by amplification with the polymerase chain reaction. The genetic sequences were compared with those of other known piroplasm species. Indirect immunofluorescent-antibody testing of serum from the four patients and from other potentially exposed persons was performed with WA1 and babesia antigens. RESULTS: Genetic sequence analysis showed that the organisms from all four patients were nearly identical. Phylogenic analysis showed that this strain is more closely related to a known canine pathogen (B. gibsoni) and to theileria species than to some members of the genus babesia. Serum from three of the patients was reactive to WA1 but not to B. microti antigen. Serologic testing showed WA1-antibody seroprevalence rates of 16 percent (8 of 51 persons at risk) and 3.5 percent (4 of 115) in two geographically distinct areas of northern California. CONCLUSIONS: A newly identified babesia-like organism causes infections in humans in the western United States. The clinical spectrum associated with infection with this protozoan ranges from asymptomatic infection or influenza-like illness to fulminant, fatal disease.

Adult↗

PubMed1995

Diel activity of nymphal Dermacentor occidentalis and Ixodes pacificus (Acari: Ixodidae) in relation to meteorological factors and host activity periods.

Relation of diel activity and questing behavior of nymphal Dermacentor occidentalis Marx and Ixodes pacificus Cooley & Kohls to meteorological factors was investigated in a shaded versus a sun-exposed outdoor arena. Oak-woodland soil covered partially with leaf litter and small rocks, and 24 vertically oriented grass stems 2.5, 5.0, 10.0, and 20.0 cm tall were provided as substrate and potential questing sites. Tick activity and weather conditions were monitored bihourly during 15 diel (24-h) experiments (D. occidentalis, 8; I. pacificus, 7). In shade, D. occidentalis was active throughout the day, but questing occurred mainly at night and in the morning on grass stems or atop soil when temperatures were cool and relative humidities high. Ticks seemed to prefer to quest at heights between approximately 4 and 10 cm. The time of day and height at which D. occidentalis quested on grass stems coincided with the activity periods and size of its lagomorph and rodent hosts. Low percentages (< or = 15%) of I. pacificus nymphs (n = 100 or 200) were active atop soil or leaf litter at night or sporadically throughout the day, but none ascended grass stems. This finding was reconfirmed by monitoring diurnal behavior of nymphs in an outdoor aquarium having leaf litter as substrate; < or = 4% of 53 ticks were detected on the topmost layer of leaves and, of those, most I. pacificus were situated on the lower versus the upper surfaces of such leaves. Activity of I. pacificus was correlated positively with relative humidity and negatively with soil temperature in one experiment. In the sun-exposed arena, ticks of both species died within 9-11 d as daytime soil-surface temperatures sometimes reached maximums of 73-77 degrees C and relative humidities dropped to 14-24%. In contrast, D. occidentalis and I. pacificus survived for up to 6 and 8 wk, respectively, in the shaded arena. After its introduction into the shaded arena, the western fence lizard (Sceloporus occidentalis Baird & Girard) acquired more I. pacificus nocturnally while asleep in soil than during its diurnal period of activity above ground. Sleeping wild lizards also became infested more often and had significantly greater burdens of I. pacificus subadults, primarily larvae, than diurnally active lizards. Collectively, these findings demonstrate that I. pacificus subadults are capable of locating and attaching to their saurian hosts subterraneanly as well as above ground.

Animals↗

PubMed1995

Evidence implicating nymphal Ixodes pacificus (Acari: ixodidae) in the epidemiology of Lyme disease in California.

To clarify the role of nymphal versus adult western black-legged ticks (Ixodes pacificus) in the epidemiology of Lyme disease, the seasonal distribution, abundance, and spirochetal infection rates in these stages, and the seasonal occurrence of ticks biting humans and of incident cases of Lyme disease were determined in northern California. Although their seasonal activity periods overlapped for about one-third of the year, nymphs and adults predominated in different seasons, the former from late spring to summer and the latter from fall to early spring. At one site, four (4%) of 100 adults from low vegetation bordering a hardwood forest and 44 (13.6%) of 324 nymphs from leaf litter in the forest were found to contain Borrelia burgdorferi. Biting-collection records revealed that nymphs attach to people more commonly than recognized previously; I. pacificus nymphs comprised 12.5% of 967 ticks of various species and stages and 42% of all nymphs submitted for identification. Attachments by nymphs occurred primarily between April and August, which coincided with the seasonal occurrence of most incident cases of Lyme disease. Collectively, these findings strongly implicate the nymphal stage of I. pacificus as the primary vector of B. burgdorferi to humans in this region.

Animals↗

PubMed1995

Transmission of Borrelia burgdorferi by Ixodes pacificus nymphs and reservoir competence of deer mice (Peromyscus maniculatus) infected by tick-bite.

The transmission of Borrelia burgdorferi to deer mice (Peromyscus maniculatus) by Ixodes pacificus nymphs was investigated experimentally. Deer mice were exposed to infected nymphs for 24, 48, or 72 hr, or until ticks had fed to repletion (> or = 96 hr). Infection status of hosts was assessed 4 wk later by culture of ear-punch biopsies in BSK II medium and by indirect immunofluorescence. Eight mice exposed to ticks for 24 hr did not become Infected. In contrast, infection was acquired by 1 of 9 (11%), 2 of 8 (25%), and 8 of 10 (80%) mice exposed for 48, 72, and > or = 96 hr, respectively. Eight weeks after exposure to infected nymphs, the infectivity of 5 deer mice for I. pacificus larvae was assessed. Overall, 33% of I. pacificus larvae fed on these mice acquired and transstadially passed spirochetes. We conclude that most I. pacificus nymphs require 4 days or longer to transmit spirochetes to deer mice, and that larvae efficiently acquire and maintain spirochetes from mice that have been infected by tick-bite.

Animals↗

PubMed1995

Natural occurrence and characterization of the Lyme disease spirochete, Borrelia burgdorferi, in cotton rats (Sigmodon hispidus) from Georgia and Florida.

This is the first report of natural infection by Borrelia burgdorferi in the cotton rat Sigmodon hispidus. Nine B. burgdorferi isolates were obtained from ear tissues, urinary bladders, or both, by culturing tissues in BSKII medium. The rat from which the SI-3 isolate was cultured was from the same site (Sapelo Island, Georgia) as an infected cotton mouse Peromyscus gossypinus and Ixodes scapularis tick reported previously. The 8 B. burgdorferi isolates from rats in Florida included 1 (AI-1) from Amelia Island, 1 (FD-1) from Faver-Dykes State Park, and 6 (MI-3 through MI-8) from Merritt Island. The distance between Sapelo Island and Merritt Island is approximately 400 km. All B. burgdorferi isolates were characterized by indirect immunofluorescence using monoclonal antibodies to OspA (H3TS, H5332) and OspB (H5TS, H6831), polymerase chain reaction detection of specific B. burgdorferi B-31 DNA target sequences (ospA, fla, and a random chromosomal sequence), and sodium dodecyl sulfate-polyacrylamide gel electrophoresis of spirochetal proteins. The phenotypic and genotypic characteristics of the isolates are discussed, as well as the probable importance of the cotton rat as a reservoir for B. burgdorferi in the southern United States.

Animals↗

PubMed1994

Vector competence of Ixodes pacificus and Dermacentor occidentalis (Acari: Ixodidae) for various isolates of Lyme disease spirochetes.

The vector competence of the western black-legged tick, Ixodes pacificus Cooley & Kohls, and the Pacific Coast tick, Dermacentor occidentalis Marx, for the Lyme disease spirochete (Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner) was compared. Rabbits, hamsters, and the deer mouse, Peromyscus maniculatus (Wagner), were injected with cultured spirochetes or infected tick-suspensions, or were fed upon by spirochete-infected ticks. Five of seven isolates used as inocula were reisolated from vertebrates with the ear-punch biopsy technique. Three isolates (CA4, 5, 7) that were infectious for both vertebrates and ticks possessed prominent low-molecular-weight protein bands that had relative mobilities of approximately 24-26 kd. The ability of ticks to acquire and maintain various inocula of B. burgdorferi was evaluated by feeding uninfected larvae xenodiagnostically on all three hosts 0-63 d postinjection. Low percentages (0-10.6%) of the I. pacificus and none of the D. occidentalis became infected. By contrast, 33% of I. pacificus and 40% of Ixodes scapularis Say (= I. dammini Spielman, Clifford, Piesman & Corwin) that fed on hamsters infected by tick-bite acquired and transstadially passed spirochetes; 10% of D. occidentalis fed on infected hamsters similarly acquired but did not maintain spirochetes. Ixodes pacificus nymphs efficiently transmitted B. burgdorferi to deer mice and a hamster. Feeding by one spirochete-infected nymph was sufficient to produce patent infections in each of five mice.

Animals↗

PubMed1994

Experimental infection of Columbian black-tailed deer with the Lyme disease spirochete.

The course of Borrelia burgdorferi-infection in Columbian black-tailed deer. (Odocoileus hemionus columbianus), its effect on the health of these animals, and their reservoir competence for fleas were evaluated experimentally. Four yearling females inoculated intramuscularly with 10(8) organisms of the CA4 strain of B. burgdorferi, and two yearling males unexposed to spirochetes, were monitored daily for 3 mo. Spirochetes were reisolated from the blood of three does at 14 or 70 days postinjection, and from several tissues of the fourth doe at necropsy. Considerable antigenic heterogeneity was observed among the reisolates as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Only two of the four infected deer developed significant antibodies (> or = 1:128) to B. burgdorferi with titers persisting for < or = 2 mo. Hematological values were highly variable and the degree of variation observed was much greater than that reported previously for Columbian black-tailed deer or other subspecies of mule deer. Infected deer did not manifest signs of Lyme disease. On histologic examination of eight tissues per deer, we observed a minimal hepatic lesion in all animals exposed to B. burgdorferi. No spirochetes were detected in 367 fleas (Pulex irritans) that had naturally infested these deer; thus this flea probably is an inefficient host of B. burgdorferi.

Animals↗

PubMed1994

Natural and experimental Borrelia burgdorferi infections in woodrats and deer mice from California.

Sequestration of spirochetes and concurrent histopathologic lesions were evaluated in tissues of Borrelia burgdorferi-infected dusky-footed woodrats (Neotoma fuscipes) and deer mice (Peromyscus maniculatus). Rodents were either wild-caught and naturally infected or were experimentally infected by tick bite, by intramuscular (i.m.) injection of cultured spirochetes, or by i.m. injection of tick suspensions. Samples of host tissues, including skin, blood, ear, brain, eye, heart, lung, liver, spleen, kidney, and urinary bladder, were removed from up to 21 woodrats and four deer mice and cultured in BSK II medium. Borreliae-positive cultures of ear punch biopsies were obtained from 10 of 11 woodrats and from all of four deer mice. Additionally, positive cultures were obtained from three of 36 skin biopsies of woodrats, and from one of 36 cultures of woodrat blood. In contrast, spirochetes were not observed in 505 cultures of internal organs or whole blood. Samples of tissues from seven naturally infected woodrats, four experimentally infected woodrats, and nine experimentally infected deer mice also were examined for histopathologic lesions. Nonsuppurative cellular infiltrates were recognized in samples from most tissue types from woodrats, but few lesions were observed in tissues from deer mice. Recognized lesions in woodrats that were consistent with infections of Lyme borreliosis in other species included synovitis, myositis, and myocarditis. Such lesions were more common in woodrats than in deer mice. Inflammatory lesions, especially synovitis, were more common in woodrats with long-term infections than in woodrats with relatively short-term infections. No clinical signs of disease were observed in either species of rodent.

Animals↗

PubMed1993

Isolation and transmission of the Lyme disease spirochete from the southeastern United States.

The isolation of the Lyme disease spirochete (Borrelia burgdorferi) from the southeastern United States is reported. Three isolates, two from cotton mice (Peromyscus gossypinus) and one from the black-legged tick (Ixodes scapularis), were recovered from Sapelo Island, Georgia, in July and September 1991. The spirochetes were characterized by indirect fluorescent antibody assay using a battery of five monoclonal antibodies, by sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS/PAGE) of whole cell lysates, and by the polymerase chain reaction (PCR) assay using primers for three DNA target sequences found in B. burgdorferi reference strain B-31. Transmission experiments indicate that the three Georgia isolates can infect experimentally inoculated hamsters and mice. Tick transmission of one of the isolates has been attempted so far; I. scapularis transmitted isolate SI-1 from hamsters to mice, but the lone-star tick, Amblyomma americanum, did not.

Animals↗

PubMed1993

Efficiency of transovarial transmission of the Lyme disease spirochete, Borrelia burgdorferi, in the western blacklegged tick, Ixodes pacificus (Acari: Ixodidae).

The efficiency of transovarial transmission of Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner was evaluated in Ixodes pacificus Cooley & Kohls collected from two areas of northern California where Lyme disease is endemic. In total, 132 (8.8%) of 1,499 replete females examined by direct immunofluorescence were demonstrated to be infected with B. burgdorferi. Larvae or eggs from 119 of these females were examined for the presence of spirochetes by direct immunofluorescence, placing them in culture, or both; none was found to contain B. burgdorferi. The fecundity of 20 midgut-infected (mean = 874.2) and 20 uninfected (mean = 1,048.3) I. pacificus females did not differ statistically. Likewise, the fertility of infected (mean = 87.0%) and uninfected (mean = 89.9%) females and the mean engorged weights of both groups (infected, 120.8 mg versus uninfected, 132.7 mg), were comparable. The fecundity, fertility, and mean weights of six replete females having ovarian infections, six females having midgut-restricted infections, and six uninfected females were also similar. We conclude that transovarial transmission is not efficient for maintaining B. burgdorferi in populations of I. pacificus, a known vector of that pathogen. Infection with the spirochete does not appear to affect either feeding or reproductive success adversely in females of this tick.

Animals↗

PubMed1993

Genetic diversity among Borrelia burgdorferi isolates from wood rats and kangaroo rats in California.

Twenty-nine Borrelia burgdorferi isolates, obtained from dusky-footed wood rats (Neotoma fuscipes) and California kangaroo rats (Dipodomys californicus) in California, were analyzed genetically. Chromosomal DNA was examined by restriction endonuclease analysis (REA) and gene probe restriction fragment length polymorphism. Pulsed-field gel electrophoresis was used to analyze the plasmid profiles of the isolates. REA, the method with the greatest discrimination, disclosed 24 distinct restriction patterns among the 29 isolates. These restriction patterns were sorted into four restriction fragment length polymorphism groups on the basis of their gene hybridization patterns. Results of the REA and plasmid profile analysis supported this grouping. The degree of genetic diversity among Californian isolates demonstrated by our findings is greater than that previously reported among other groups of North American isolates and is similar or greater than the diversity reported among European isolates.

Animals↗

PubMed1992

Risk factors for Lyme disease in a small rural community in northern California.

A 1-year prospective study of risk factors for seropositivity to and contraction of Lyme disease among members of a small rural community (population, approximately 150) was conducted in northwestern California in 1988-1989. The initial rate of seropositivity for Borrelia burgdorferi for 119 current or former residents ranged from 15 to 20% among three laboratories, with statistically significant interlaboratory agreement. Questionnaires were completed by 93 current residents at entry and 80 residents a year later to evaluate the association of serologic status with 20 categorical and 47 continuous variables. Seropositive subjects had resided in the study area about 2 years longer, were bitten by unspecified biting flies more often, and were less likely to have engaged in hiking than seronegative subjects. One of 59 seronegative subjects seroconverted a year later (annual incidence = 1.7%). The cumulative frequency of seropositivity for Lyme disease in the study population was > or = 24%. Of 83 subjects examined physically, 13 were diagnosed as having definite and 18 as having probable Lyme disease. The seropositivity rate was significantly higher (38.7%) among individuals with definite/probable Lyme disease than in asymptomatic subjects (13.5%). Subjects who were seronegative or free of Lyme disease reported nearly as many tick bites as subjects who were seropositive or had a diagnosis of the disease. Age, time spent outdoors in the fall multiplied by a clothing index, and woodcutting were significantly associated with Lyme disease in logistic regression analyses.

Adult↗

PubMed1992

Blood donation.

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Antibodies, Viral↗

PubMed1992

Lyme disease in California: a novel enzootic transmission cycle of Borrelia burgdorferi.

Knowledge of zoonotic transmission cycles is essential for the development of effective strategies for disease prevention. The enzootiology of Lyme disease in California differs fundamentally from that reported from the eastern United States. Woodrats, not mice, serve as reservoir hosts, and Ixodes neotomae, a nonhuman-biting tick, maintains the agent of Lyme disease, Borrelia burgdorferi, in enzootic cycles. The western black-legged tick, Ixodes pacificus, is the primary vector to humans, but it appears to be an inefficient maintenance vector. Isolates of B. burgdorferi from California exhibit considerable antigenic heterogeneity, and some isolates differ strikingly from isolates recovered from this and other geographic regions.

Animals↗

PubMed1992

Production and therapeutic use of a factor XI concentrate from plasma.

Factor XI deficiency is an uncommon bleeding disorder usually manifested by excessive bleeding after surgery or trauma. Until recently the only effective therapy has been fresh-frozen plasma (FFP) infusion. We describe the efficacy and safety of a new factor XI concentrate produced from human donor plasma by a modification of the method used for antithrombin III concentrate. The mean recovery of factor XI in the circulation measured on 62 occasions was approximately 91% of the injected dose, and the mean half-disappearance-time was 52 h. The concentrate was used for 31 invasive procedures in 30 patients, including 16 patients who had a definite bleeding tendency on previous occasions, with normal haemostasis being achieved in all but 1. Only 1 patient (previously experiencing allergy to FFP) experienced adverse effects during infusion. Monitoring of liver function tests and viral antibody status in suitable patients has shown no evidence of transmission of hepatitis viruses, HIV-1 or parvovirus B19. We conclude that this concentrate provides effective treatment for patients with factor XI deficiency. Preliminary results suggest safety from virus transmission, but this needs to be established in further studies of previously untreated patients.

Adolescent↗

PubMed1992

First isolation of Borrelia burgdorferi in southern California.

The Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, was isolated from the blood of a dusky-footed wood rat, Neotoma fuscipes Baird, in the San Bernardino Mountains of southern California. Antigenic, protein, and molecular analyses demonstrated that the isolate varied slightly from most isolates of B. burgdorferi from northern California and was clearly distinct from other species of Borrelia that are endemic to the state. This is the first reported isolate of B. burgdorferi from southern California and demonstrates that the Lyme disease spirochete is enzootic in mountains near the major human population center of the state.

Animals↗

PubMed1992

The western fence lizard Sceloporus occidentalis: evidence of field exposure to Borrelia burgdorferi in relation to infestation by Ixodes pacificus (Acari: Ixodidae).

The role of the Western fence lizard Sceloporus occidentalis in the enzootiology of the Lyme disease spirochete Borrelia burgdorferi was evaluated in the Hopland and Ukiah areas of Mendocino County, California. In 1989, half of 74 lizards collected monthly from April to October at Hopland were infested by the immature western black-legged tick Ixodes pacificus at a mean intensity of 6.0 ticks per lizard. The prevalence of infestation of lizards by immature I. pacificus (36 of 73) at Ukiah was similar, but the mean intensity (12.9) was approximately twice as great. Overall, zero of 223 larvae and 2 (0.6%) of 330 nymphs from both sites were found to contain spirochetes by direct immunofluorescence. Larval and nymphal I. pacificus fit the negative binomial distribution in spring, and the prevalence and abundance of these stages were significantly greater in spring than in summer at both sites. Spirochetes were not visualized in thick blood films prepared from 133 lizards from both localities. Plasma antibodies against B. burgdorferi were detected in seven of 10 experimentally inoculated lizards, in five (8%) of 63 lizards from Hopland, and in 10 (14%) of 70 lizards from Ukiah. Adult lizards had a significantly greater tick burden and seropositivity rate than juvenile lizards only at Ukiah. In 1991, efforts to detect and culture spirochetes from the blood of 21 wild-caught lizards and from the tissues of 189 associated ticks that fed xenodiagnostically on them were unsuccessful.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗