Distribution of Crimean-Congo hemorrhagic fever viral antibody in Senegal: environmental and vectorial correlates

The spatial pattern in Senegal of Crimean-Congo hemorrhagic fever (CCHF) virus IgG antibody prevalence in human and sheep was determined as was the relative abundance of potential tick vectors. A systematic, country-wide serological survey of sheep demonstrated that 10.4% of sheep exhibited IgG to CCHF virus. Sexes were infected equally. Antibody prevalence increased with age from 2.1% during the first year to 18.2% among sheep greater than or equal to 3 years of age. IgG prevalence was highest in the northern, arid Sahelian zone, averaging 75.7% seropositivity, and decreased to zero in the southern, moister Sudano-Guinean and Guinean zones. Human IgG prevalence ranged from 21% to less than 1% among the 8 sites that were sampled throughout the country, being greatest in the arid north and least in the south. Hyalomma ssp. ticks predominated in those biotopes where antibody prevalence was highest. The abundance of Hyalomma ticks may be the proximal determinant of endemic transmission.

A fatal case of Crimean-Congo haemorrhagic fever in Mauritania: virological and serological evidence suggesting epidemic transmission

Crimean-Congo haemorrhagic fever (CCHF), a tick-borne viral zoonosis, is focally endemic throughout parts of Eurasia, the Middle East and Africa. In sub-saharan West Africa only 2 previous cases, both non-fatal, have been reported. We documented a fatal human case of CCHF in south-western Mauritania during May 1988 by demonstrating CCHF virus-specific class M antibodies and by isolating CCHF virus. Five of 7 other patients simultaneously in hospital with haemorrhagic fever symptoms also exhibited elevated immunoglobulin (Ig) G. Healthy family members and contacts of these patients showed an IgG prevalence of 36%; similarly 29% of their sheep also had antibodies. A serosurvey of 1219 sheep from 14 widely dispersed sites throughout southern Mauritania demonstrated IgG prevalences ranging from 4.9% to 43.6%. IgM was found in many herds. These observations demonstrate that CCHF virus is enzootic in southern Mauritania, and suggest a recent period of intense transmission in parts of the region.

Co-overproduction and localization of the Escherichia coli motility proteins motA and motB

The motility genes motA and motB of Escherichia coli were placed under control of the Serratia marcescens trp promoter. After induction with beta-indoleacrylic acid, the levels of MotA and MotB rose over about a 3-h period, reaching plateau levels approximately 50-fold higher than wild-type levels. Both overproduced proteins inserted into the cytoplasmic membrane. Growth and motility were essentially normal, suggesting that although the motor is a proton-conducting device, MotA and MotB together do not constitute a major proton leak. Derivative plasmids which maintained an intact version of motB but had the motA coding region deleted in various ways were constructed. With these, the levels of MotB were much lower, reaching a peak within 30 min after induction and declining thereafter; pulse-chase measurements indicated that a contributing factor was MotB degradation. The low levels of MotB occurred even with an in-frame internal deletion of motA, whose translational initiation and termination sites were intact, suggesting that it is the MotA protein, rather than the process of MotA synthesis, that is important for MotB stability. Termination at the usual site of overlap with the start of motB (ATGA) was not an absolute requirement for MotB synthesis but did result in higher rates of synthesis than when translation of motA information terminated prematurely. Even in the total absence of MotA, the MotB that was synthesized was found exclusively in the cytoplasmic membrane fraction. In wild-type cells, MotA was estimated by immunoprecipitation to be in about fourfold excess over MotB; a previous estimate of 600 +/- 250 copies of MotA per cell then yielded an estimate of 150 +/- 70 copies of MotB per cell.

BacT/Alert: an automated colorimetric microbial detection system

BacT/Alert (Organon Teknika Corp., Durham, N.C.) is an automated microbial detection system based on the colorimetric detection of CO2 produced by growing microorganisms. Results of an evaluation of the media, sensor, detection system, and detection algorithm indicate that the system reliably grows and detects a wide variety of bacteria and fungi. Results of a limited pilot clinical trial with a prototype research instrument indicate that the system is comparable to the radiometric BACTEC 460 system in its ability to grow and detect microorganisms in blood. On the basis of these initial findings, large-scale clinical trials comparing BacT/Alert with other commercial microbial detection systems appear warranted.

The development of a sedation model in dogs

The effect of various sedatives (ketamine, valium, acetylpromazine) on the saliva flow rate, swallowing capacity, muscle rigidity and ability to immobilize in an upright position was investigated in dogs. Ten healthy beagle dogs (3, six months old, 3, six years old, and 4 fourteen years old) were used for this study. A combination of ketamine (5 mg/kg) and acetylpromazine (0.175 mg/kg) produced the desired effect of normal saliva flow rate, swallowing capacity and muscle rigidity; immobilization in an upright position was attained. The saliva flow rate (unsedated) was found to decrease with increasing age of the dogs. The time to recovery from the ketamine/acetylpromazine sedation increased with increasing age of the dogs.

A multidisciplinary approach to information and critical appraisal instruction

The formulation of clinical decisions based on evidence requires the ability to locate information and evaluate it critically. A ten-week critical appraisal course for third-year medical students, taught cooperatively by library and Department of Medicine faculty, integrates education in the selection, evaluation, and application of information to patient care. The course is distinctive in that information management skills are taught by a multidisciplinary team in a problem-based format as part of the compulsory medical curriculum. Medical faculty provided instruction in reading and evaluating research methodology, as well as statistical analyses in published reports, using clinical scenarios and related journal articles at weekly sessions. Library faculty provided instruction in locating pertinent research on a sample clinical problem using standard printed and computerized indexes and local library resources, and presented criteria for selecting the most useful and significant works from those retrieved. Library faculty also met individually with students to provide instruction in online literature searching. Based on formal evaluation and informal feedback, the course was well received; it effectively presents the literature search as an integral part of critical appraisal of the medical literature and of the clinical decision-making process.

Comparing the relative potential of rodents as reservoirs of the Lyme disease spirochete (Borrelia burgdorferi)

The authors compared the contribution of white-footed mice (Peromyscus leucopus), chipmunks (Tamias striatus), and meadow voles (Microtus pennsylvanicus) to infection of vector ticks with the Lyme disease spirochete, Borrelia burgddorferi. At one Massachusetts location where Lyme disease is endemic, all three species of rodents were found to be infected. Prevalence of infection, however, varied from 90% for mice, and 75% for chipmunks to just 5.5% for meadow voles. Infectivity of these hosts for larval Ixodes dammini also varied, but mice were found to be the most infective, followed by chipmunks and meadow voles. Density estimates of these three hosts, collected between 1981 and 1986 in three coastal Massachusetts locations, revealed that mice were more abundant than the other two rodents in areas in which ticks were abundant. In addition, mice were infested more abundantly with larval I. dammini than the other two host species. Integrating these results, we determined each species' "reservoir potential," a novel term which describes the relative contribution made by a host species to the horizontal infection of a vector population. The authors' findings demonstrate that, at least in coastal Massachusetts, P. leucopus is the most important small mammal reservoir for B. burgdorferi.

Rapid emergence of a focal epidemic of Lyme disease in coastal Massachusetts

We describe a focal epidemic of Lyme disease, which spread from a nature preserve and affected an adjacent community of permanent residents in coastal Massachusetts. The attack rate from 1980 through 1987 was 35 percent among 190 residents living within 5 km of the nature preserve and was greatest (66 percent) among those living closest to the preserve. The risk of infection bore little relation to sex or age. Late Lyme disease, which clustered near the preserve, occurred mainly in residents infected early in the epidemic who did not have a history of erythema migrans and did not receive antibiotic therapy. All the residents with serologic evidence of infection had early or late clinical manifestations of Lyme disease, or both, during the period of study. The seasonal risk of infection was bimodal--greatest in June, with a secondary peak in October--and corresponded to periods of increased transmission. In the nature preserve, the density of the vector tick, Ixodes dammini, exceeded that in other New England sites. The zoonosis rapidly became endemic, and the severity of its impact correlated with the abundance of deer. This epidemic of Lyme disease demonstrated that outbreaks can be focal and can spread rapidly within a community of permanent residents.

Rift Valley fever among domestic animals in the recent West African outbreak

Severe haemorrhagic disease among the human population of the Senegal River Basin brought the Rift Valley fever virus (RVFV) outbreak of 1987 to the attention of science. As in previous RVFV outbreaks, local herdsmen reported a high incidence of abortion and disease in their livestock. Serum samples were obtained from domestic animal populations from areas near Rosso, the best studied focus of human infection, as well as other areas distant from known human disease. Among animals from the area of high incidence of human disease, antibody prevalence was as high as 85%, with approximately 80% of the sera positive for both RVFV IgG- and viral-specific IgM antibodies. In contrast, human populations in the same area had lower RVFV antibody prevalences, 40% or less, with 90% also being IgM-positive. Sera from livestock in coastal areas 280 km south of the epidemic area were negative for RVFV antibodies. Thus, the detection of RVFV specific IgG and IgM antibodies provided evidence of recent disease activity without the requirement to establish pre-disease antibody levels in populations or individuals and without viral isolation. Subsequently, detection of modest levels of IgG and IgM in the Ferlo region, 130 km south of the Senegal River flood plain, established that RVFV transmission also occurred in another area of the basin. Similar serological testing of domestic ungulates in The Gambia, 340 km south of Rosso, demonstrated antibody prevalence consistent with a lower level of recent transmission of RVFV, i.e., 24% IgG-positive with 6% of the positive sera also having RVFV-specific IgM.

[Prevalence of antibodies against Rift Valley fever virus in sheep and goats in Senegal]

A total of 1,715 randomly selected sheep and goat sera from Senegal were tested for antibodies against Rift Valley fever virus using an enzyme-linked immunosorbent assay. The results showed that Rift Valley fever is enzootic. The prevalence is highly heterogeneous, depending on the area. Sheep and goats expressed comparable antibody prevalence, suggesting that both are involved equally in the virus cycle.

Reference activity and the external user: confluence of community needs at a medical school branch library

The allocation of reference services between primary and secondary users constantly challenges academic medical libraries. Routine statistics at a medical school branch library suggested that over 40% of its reference transactions involved persons not affiliated with the university. To investigate this finding, a survey of reference activity was conducted using measurement techniques unobtrusive to the user. Fifteen data items were recorded, including user status, type of question, intended use of information requested, status of staff taking request, and staff time spent. Survey results showed that nonaffiliates accounted for 51% of reference activity. Based on this documented data, definitive reference guidelines addressing hours, priority of requests, charges, and staffing patterns can now be developed. Findings will also assist in evaluating the library's regional role, in formulating marketing strategies, and in determining library objectives.

Incompetence of deer as reservoirs of the Lyme disease spirochete

To determine whether deer may serve as reservoir hosts for the Lyme disease spirochete, we sought evidence of infection in nymphal Ixodes dammini derived from larvae that had engorged on white-tailed deer. A total of 19 deer were shot in two Lyme disease foci in Massachusetts during September 1986, the season in which larvae were most abundant. An average of 342 larval ticks of this species were collected from each deer. Of those that developed to the nymphal stage, the gut contents of 185 were examined for Borrelia burgdorferi by a direct fluorescent antibody test. Spirochetes were detected in about 1% of these nymphs, a rate of infection attributable to transovarial transmission. In contrast, infection was detected in 23% of 39 field-swept nymphal ticks of the same cohort that were collected during the following season. Although deer may be infested by numerous larval I. dammini, such ticks appear not to become infected by Lyme disease spirochetes.

Overproduction of the MotA protein of Escherichia coli and estimation of its wild-type level

The motA gene of Escherichia coli was placed under the control of a high-level promoter, that of the tryptophan operon of Serratia marcescens. In the presence of the inducer beta-indoleacrylic acid, MotA was synthesized at greatly elevated levels and inserted without apparent limit into the inner membrane. Growth and motility were impaired, but not drastically so, indicating that MotA by itself does not act as a proton ionophore. Antibody raised against the overproduced protein was used to estimate that a wild-type cell contained 600 +/- 250 copies of MotA. This number is more than would be needed to surround each flagellar basal body with a single circlet of MotA protein; possible interpretations of the result are discussed. The antibody was also used to establish that the MotA protein of Salmonella typhimurium has a similar molecular weight to that of E. coli and is immunologically cross-reactive with it; functional complementation of S. typhimurium motA mutants by the E. coli gene was established.

Effect of charge on hepatic specific nature of vesicle encapsulated insulin in conscious dogs

Positively [(+)-VEI] and negatively [(-)-VEI] charged formulations of vesicle encapsulated insulin (VEI) were compared with insulin on the basis of their ability to suppress hepatic glucose production (hepatic Ra) and stimulate glucose utilization (Rd) in conscious dogs. Our results indicate that (-)-VEI and insulin have an equivalent capacity to suppress hepatic glucose production at dose levels of 0.2, 1.2, and 2.4 mU X kg-1 X min-1. (+)-VEI is less effective at suppressing hepatic Ra than both insulin and (-)-VEI at dose levels of 1.2 and 2.4 mU X kg-1 X min-1. Both (+)-VEI and (-)-VEI induced significantly less glucose utilization than a comparable amount of insulin at dose levels of 1.2 and 2.4 mU X kg-1 X min-1. The amount of glucose utilization stimulated by (+)-VEI was significantly less than that induced by insulin at 0.6 mU X kg-1 X min-1. This difference was not evident with (-)-VEI. These results suggest that the insulin contained in (+)-VEI is less bioavailable than that contained in (-)-VEI. This difference in bioavailability is believed to be the result of greater serum stability of (+)-VEI vesicles when compared with that of (-)-VEI. In conclusion, both (+)-VEI and (-)-VEI have the capacity to shield encapsulated insulin from interacting with peripheral tissues and deliver insulin selectively to the liver. Both formulations afford one an opportunity to expand the therapeutic window for hepatically active compounds where their utility is limited by systemic toxicity.

Longitudinal assessment of the clinical and epidemiological features of Lyme disease in a defined population

From 1979 to 1983, Lyme disease was studied longitudinally in the 162 long-term residents of Great Island, Massachusetts. In retrospect, the index case occurred in 1962, and the peak years of disease transmission (about three new cases per 100 residents per year) were the late 1970s. Thereafter, during the period of active surveillance, attack rates declined by half. Altogether, 26 (16%) of the 162 residents developed symptoms of the disease. Most of those affected had erythema chronicum migrans, and when untreated, they subsequently developed arthritis or, in one instance, myocarditis. A minority of individuals, mostly children, had arthritis alone. Of 121 asymptomatic residents who gave blood samples, 10 adults (8%) had high titers of IgG antibodies to the Lyme disease spirochete; these titers sometimes persisted for years. From 1981 to 1983, the estimated ratio of apparent-to-inapparent infection was 1:1. The high frequency of Lyme disease on Great Island underscores the need for surveillance and control programs.

Racial and socioeconomic disparities in childhood mortality in Boston

We examined racial and income-related patterns of mortality from birth through adolescence in Boston, where residents have high access to tertiary medical care. Childhood mortality was significantly higher among black children (odds ratio, 1.24; P less than 0.05) and low-income children (odds ratio, 1.47; P less than 0.001). Socioeconomic effects varied for different age groups and causes of death. The largest relative disparity occurred in the neonatal and postneonatal periods, and the smallest in adolescence. Of the total racial differential in neonatal mortality (6.88 deaths per 1000 live births), 51.2 per cent occurred in premature infants, 13.4 per cent in term infants who were small for their gestational age, and 25.9 per cent in neonates who were both premature and small for their age. Black neonatal mortality was elevated at all income levels. Beyond the neonatal period, mortality from respiratory disease, fire, and homicide had strong inverse relationships with income, and mortality from injuries to the occupants of motor vehicles was directly related to income. These data suggest that despite access to tertiary medical services, substantial social differentiation in mortality may exist throughout childhood. Equity in childhood survival will probably require policies that emphasize preventive goals.

Membrane protein conformational change dependent on the hydrophobic environment

Two conformational states of the coat protein of the filamentous bacteriophage M13 have been detected in detergent solution by using magnetic resonance techniques. When 3-fluorotyrosine is incorporated in place of the two tyrosine residues in the protein, four 19F nuclear magnetic resonance signals are observed, two for each conformer of the protein. The equilibrium between the two forms can be modulated by pH, temperature, and detergent structure. The rate of interconversion of the isomers is rapid on the minutes time scale but is slow relative to the T1 relaxation time of the fluorine resonances of approximately 50 ms. The conformational change between the conformers results in the perturbation of a basic residue in the protein such that this group has a pKa of approximately 9.5 in one state which shifts to 10.5 or more in the other conformational state. The temperature dependence of the equilibrium suggests an enthalpy difference of about 10 kcal/mol which is offset by entropy to give nearly zero free energy difference between the states at pH 8.3 in deoxycholate solution at room temperature. This suggests a substantial reorganization of the noncovalent interactions defining the two conformational states. The conformational equilibrium is strongly dependent on detergent structure and the presence of phospholipid in the detergent micelle. The results are not consistent with a strong, specific lipid binding to the protein but appear to be consistent with a more general effect of the overall micelle structure on the conformational state of the protein.

Mice as reservoirs of the Lyme disease spirochete

In evaluating the white-footed mouse as a reservoir host for the Lyme disease spirochete, we compared spirochete infection in vector ticks (Ixodes dammini) having different histories of attachment to these mice, estimated their relative importance as hosts for immature I. dammini and compared the seasonality of tick activity and spirochetemia in mice. Infection in trapped white-footed mice appears to be universal. Prevalence of spirochetal infection in I. dammini correlates with frequency of attachment to mice, and in mice, with the season of vector activity. The relative abundance of this mouse makes it numerically the most important host for I. dammini. Most immature I. dammini appear to attach to white-footed mice. Taken together, these considerations demonstrate that the white-footed mouse serves as reservoir for the Lyme disease spirochete in coastal Massachusetts.

Female homosexuals' need for dominance and endurance

An analysis of whether differing sex-object choice by 46 heterosexual and 46 homosexual females (21 to 50 yr. old) is associated with significant differences in scores on the Edwards Personal Preference Schedule indicated heterosexual women scored higher on the heterosexuality scale while homosexual women scored higher on the Dominance scale and the Endurance scale. Neither group scored above or below what is considered the normal T-score ranges of 30 to 70 on any scale.

Vectorial capacity of North American Ixodes ticks

Ixodes dammini, the vector of Lyme disease and babesiosis, is distributed in various locations in the northeastern quadrant of the United States and nearby Canada. The life cycle of this tick, which includes larval, nymphal, and adult stages, spans at least two years. The tick over-winters between larval and nymphal feeding. Horizontal transmission of pathogens is facilitated by a feeding pattern in which both the larval and nymphal stages feed on the white-footed mouse, Peromyscus leucopus, and by a seasonal pattern of activity in which nymphs precede larvae. The species range appears to have expanded from a single island location, and has invaded new sites since the 1940s, some as recently as 1980. This increased abundance appears to be related to the increased abundance of deer, the preferred host of the adult stage. I. muris predominated in coastal Massachusetts before I. dammini became abundant, but is probably now extinct. I. scapularis, which is present in the southern U.S., is a poor vector of mouse parasites because about 90 percent of these immature ticks feed on lizards. To the extent that horizontal transmission occurs, we suggest that mice serve as the principal reservoir for the Lyme spirochete as well as Babesia microti.

Effect of deer reduction on abundance of the deer tick (Ixodes dammini)

To evaluate the role of deer in regulating the abundance of the deer tick (Ixodes dammini) we attempted to treat with acaricide, but eventually removed, about 70 percent of deer from Great Island, Cape Cod, Massachusetts. Deer were captured in box traps, a corral, an entanglement net, and with rifle-fired tranquilizer. Failure of these attempts, combined with ineffective acaricides, led us to deer destruction begun in fall 1982. Larval tick abundance on mice was monitored before and after deer removal. We concluded that deer removal, to the extent accomplished, did not markedly reduce the abundance of the tick. Reduced abundance of deer may not result in reduced abundance of immature ticks if deer removal follows the period of adult tick feeding, or if intensity of infestation per deer increases, or if other mammals substitute as suitable hosts. Reduced tick abundance may be delayed if unattached immature ticks survive more than one year.