Dynamics, distribution, and transformations of mercury species from pyrenean high-altitude lakes

While mercury (Hg) is a major concern in all aquatic environments because of its methylation and biomagnification pathways, very few studies consider Hg cycling in remote alpine lakes which are sensitive ecosystems. Nineteen high-altitude pristine lakes from Western/Central Pyrenees were investigated on both northern (France) and southern (Spain) slopes (1620-2600 m asl.). Subsurface water samples were collected in June 2017/2018/2019 and October 2017/2018 for Hg speciation analysis of inorganic mercury (iHg(II)), monomethylmercury (MMHg), and dissolved gaseous mercury (DGM) to investigate spatial and seasonal variations. In June 2018/2019 and October 2018, more comprehensive studies were performed in four lakes by taking water column depth profiles. Besides, in-situ incubation experiments using isotopically enriched Hg species (¹⁹⁹iHg(II), ²⁰¹MMHg) were conducted to investigate Hg transformation mechanisms in the water column. While iHg(II) (0.08-1.10 ng L^-1 in filtered samples; 0.11-1.19 ng L^-1 in unfiltered samples) did not show significant seasonal variations in the subsurface water samples, MMHg (<0.03-0.035 ng L^-1 in filtered samples; <0.03-0.062 ng L^-1 in unfiltered samples) was significantly higher in October 2018, mainly because of in-situ methylation. DGM (0.02-0.68 ng L^-1) varies strongly and can exhibit higher levels in comparison with other pristine areas. Depth profiles and incubation experiments highlighted the importance of in-situ biotic methylation triggered by anoxic conditions in bottom waters. In-situ incubations confirm that significant methylation, demethylation and photoreduction extents are taking place in the water columns. Overall, drastic environmental changes occurring daily and seasonally in alpine lakes are providing conditions that can both promote Hg methylation (stratified anoxic waters) and MMHg photodemethylation (intense UV light). In addition, light induced photoreduction is a major pathway controlling significant gaseous Hg evasion. Global warming and potential eutrophication may thus have direct implications on Hg turnover and MMHg burden in those remote ecosystems.

Selenium distribution and speciation in waters of pristine alpine lakes from central-western Pyrenees (France-Spain)

The speciation of both redox reactive and volatile selenium (Se) compounds, barely reported in pristine aquatic environments, has never been investigated in remote alpine lakes, considered as sensitive ecosystems to detect the effect of global change. This work presents an integrated investigation on Se distribution and speciation conducted in 20 high altitude pristine lakes from the central-western Pyrenees. Five seasonal sampling campaigns were carried out after snowmelt (June/July) and in early fall (October) for the period 2017-2019. Concentrations of total dissolved Se (TDSe) ranged from 7 to 78 ng L^-1, with selenate being ubiquitously observed in most cases (median of 61% of TDSe). Selenite was only occasionally detected up to 4 ng L^-1, therefore a fraction of TDSe was presumably in the forms of elemental Se(0) and/or selenides. Depth profiles obtained in different lakes showed the occurrence of such Se(-II, 0) pools in bottom hypoxic to anoxic waters. The production of volatile Se compounds presented a low median total concentration (TVSe) of 33 pg L^-1 (range 3-120 pg L^-1), mainly in the form of dimethylselenide in subsurface samples (median of 82% of TVSe). The Se concentration in lake waters was significantly correlated with the sulphate concentration (ρ = 0.93, p < 0.0001), demonstrating that it is influenced by erosion and dissolution of Se and S-enriched parent bedrocks. In addition, for Se depleted alpine lake-bedrock systems, long-range transport and wet atmospheric depositions represent a major source of Se for lake waters.

Recent and historical pollution legacy in high altitude Lake Marboré (Central Pyrenees): A record of mining and smelting since pre-Roman times in the Iberian Peninsula

We have analyzed potential harmful trace elements (PHTE; Pb, Hg, Zn, As and Cu) on sediment cores retrieved from lake Marboré (LM) (2612 m a.s.l, 42°41'N; 0° 2'E). PHTE variability allowed us to reconstruct the timing and magnitude of trace metal pollutants fluxes over the last 3000 years in the Central Pyrenees. A statistical treatment of the dataset (PCA) enabled us to discern the depositional processes of PHTE, that reach the lake via direct atmospheric deposition. Indeed, the location of LM above the atmospheric boundary layer makes this lake an exceptional site to record the long-range transport of atmospheric pollutants in the free troposphere. Air masses back-trajectories analyses enabled us to understand the transport pathways of atmospheric pollutants while lead isotopic analyses contributed to evaluate the source areas of metal pollution in SW Europe during the Late Holocene. PHTE variability, shows a clear agreement with the main exploitation phases of metal resources in Southern Europe during the Pre-Industrial Period. We observed an abrupt lead enrichment from 20 to 375 yrs CE mostly associated to silver and lead mining and smelting practices in Southern Iberia during the Roman Empire. This geochemical data suggests that regional atmospheric metal pollution during the Roman times rivalled the Industrial Period. PHTE also increased during the High and Late Middle Ages (10-15^th centuries) associated to a reactivation of mining and metallurgy activities in high altitude Pyrenean mining sites during climate amelioration phases. Atmospheric mercury deposition in the Lake Marboré record mostly reflects global emissions, particularly from Almadén mines (central Spain) and slightly fluctuates during the last three millennia with a significant increase during the last five centuries. Our findings reveal a strong mining-related pollution legacy in alpine lakes and watersheds that needs to be considered in management plans for mountain ecosystems as global warming and human pressure effects may contribute to their future degradation.

Effects of feeding a quebracho-chestnut tannin extract on lactating cow performance and nitrogen utilization efficiency

The effects of feeding a quebracho-chestnut tannin extract mixture on performance and nitrogen (N) utilization were assessed with 36 multiparous lactating Holstein cows (mean ± standard deviation; 706 ± 59 kg of body weight; 126 ± 20 d in milk) randomly assigned to 3 dietary treatments in a randomized complete block design. Following a 2-wk covariate adjustment period, cows were fed their assigned treatment diets for 13 wk. Rice hulls were removed from a total mixed ration with a 54:46 forage:concentrate ratio (% of dry matter; DM), and a tannin extract mixture from quebracho and chestnut trees (2:1 ratio) was included at 0, 0.45, and 1.80% of dietary DM. There was no interaction between dietary treatments and experimental week for the reported measurements except milk lactose percentage. Overall, treatments did not affect milk yield (48.6 ± 7.8 kg/d), fat- and protein-corrected milk (46.1 ± 7.6 kg/d), milk fat content (3.88 ± 0.65%) and yield (1.85 ± 0.38 kg/d), and true protein yield (1.45 ± 0.21 kg/d). However, incremental levels of tannin extracts in the diet produced a linear increase in DM intake (29.2 to 30.9 kg/d) and a linear decrease in kilograms of milk per kilogram of DM intake (1.67 to 1.57 kg/kg) and MUN (12.2 to 10.8 mg/dL). Furthermore, there was a quadratic effect of tannin extracts on milk true protein content (2.96, 3.13, and 3.00% for 0, 0.45, and 1.80% tannin extract, respectively) and a tendency for linear and quadratic response for body weight gain (0.31, 0.16, and 0.44 kg/d for 0, 0.45, and 1.80% tannin, respectively). Intake of N increased linearly (782, 795, and 820 g/d) and N utilization efficiency (milk N/intake N) decreased linearly (0.300, 0.301, and 0.275 for 0, 0.45, and 1.80% tannin, respectively). Relative to the 0% diet, 1.80% tannin extract reduced estimated urinary N excretion by 11%. In this study, adding 0.45% tannin extract to the diet reduced feed efficiency but had a positive effect on milk protein content. Feeding a tannin extract mixture from quebracho and chestnut may reduce environmental labile urinary N excretion without affecting milk yield but at the expense of a lower feed utilization efficiency.

Seabird Tissues As Efficient Biomonitoring Tools for Hg Isotopic Investigations: Implications of Using Blood and Feathers from Chicks and Adults

Blood and feathers are the two most targeted avian tissues for environmental biomonitoring studies, with mercury (Hg) concentration in blood and body feathers reflecting short and long-term Hg exposure, respectively. In this work, we investigated how Hg isotopic composition (e.g., δ²⁰²Hg and Δ¹⁹⁹Hg) of blood and feathers from either seabird chicks (skuas, n = 40) or adults (penguins, n = 62) can accurately provide information on exposure to Hg in marine ecosystems. Our results indicate a strong correlation between blood and feather Hg isotopic values for skua chicks, with similar δ²⁰²Hg and Δ¹⁹⁹Hg values in the two tissues (mean difference: -0.01 ± 0.25 ‰ and -0.05 ± 0.12 ‰, respectively). Since blood and body feathers of chicks integrate the same temporal window of Hg exposure, this suggests that δ²⁰²Hg and Δ¹⁹⁹Hg values can be directly compared without any correction factors within and between avian groups. Conversely, penguin adults show higher δ²⁰²Hg and Δ¹⁹⁹Hg values in feathers than in blood (mean differences: 0.28 ± 0.19‰ and 0.25 ± 0.13‰), most likely due to tissue-specific Hg temporal integration. Since feathers integrate long-term (i.e., the intermoult period) Hg accumulation, whereas blood reflects short-term (i.e., seasonal) Hg exposure in adult birds, the two tissues provide complementary information on trophic ecology at different time scales.

Plasma radiation dynamics with the upgraded Absolute Extreme Ultraviolet tomographical system in the Tokamak à Configuration Variable

We introduce an upgraded version of a tomographical system which is built up from Absolute Extreme Ultraviolet-type (AXUV) detectors and has been installed on the Tokamak à Configuration Variable (TCV). The system is suitable for the investigation of fast radiative processes usually observed in magnetically confined high-temperature plasmas. The upgrade consists in the detector protection by movable shutters, some modifications to correct original design errors and the improvement in the data evaluation techniques. The short-term sensitivity degradation of the detectors, which is caused by the plasma radiation itself, has been monitored and found to be severe. The results provided by the system are consistent with the measurements obtained with the usual plasma radiation diagnostics installed on TCV. Additionally, the coupling between core plasma radiation and plasma-wall interaction is revealed. This was impossible with other available diagnostics on TCV.

Characterization of extended-spectrum cephalosporin-resistant Salmonella enterica serovar Heidelberg isolated from food animals, retail meat, and humans in the United States 2009

Salmonella enterica is one of the most common causes of foodborne illness in the United States. Although salmonellosis is usually self-limiting, severe infections typically require antimicrobial treatment, and ceftriaxone, an extended-spectrum cephalosporin (ESC), is commonly used in both adults and children. Surveillance conducted by the National Antimicrobial Resistance Monitoring System (NARMS) has shown a recent increase in ESC resistance among Salmonella Heidelberg isolated from food animals at slaughter, retail meat, and humans. ESC resistance among Salmonella in the United States is usually mediated by a plasmid-encoded bla(CMY) β-lactamase. In 2009, we identified 47 ESC-resistant bla(CMY)-positive Heidelberg isolates from humans (n=18), food animals at slaughter (n=16), and retail meats (n=13) associated with a spike in the prevalence of this serovar. Almost 90% (26/29) of the animal and meat isolates were isolated from chicken carcasses or retail chicken meat. We screened NARMS isolates for the presence of bla(CMY), determined whether the gene was plasmid-encoded, examined pulsed-field gel electrophoresis patterns to assess the genetic diversities of the isolates, and categorized the bla(CMY) plasmids by plasmid incompatibility groups and plasmid multi-locus sequence typing (pMLST). All 47 bla(CMY) genes were found to be plasmid encoded. Incompatibility/replicon typing demonstrated that 41 were IncI1 plasmids, 40 of which only conferred bla(CMY)-associated resistance. Six were IncA/C plasmids that carried additional resistance genes. pMLST of the IncI1-bla(CMY) plasmids showed that 27 (65.8%) were sequence type (ST) 12, the most common ST among bla(CMY)-IncI1 plasmids from Heidelberg isolated from humans. Ten plasmids had a new ST profile, ST66, a type very similar to ST12. This work showed that the 2009 increase in ESC resistance among Salmonella Heidelberg was caused mainly by the dissemination of bla(CMY) on IncI1 and IncA/C plasmids in a variety of genetic backgrounds, and is likely not the result of clonal expansion.

A dynamic model for assessing universal Hepatitis A vaccination in Canada

Vaccination against Hepatitis A virus (HAV) in Canada is currently targeted toward high-risk groups. However, universal vaccination has been adopted in several other countries with a similar disease burden. Here we develop an age-structured compartmental model of HAV transmission and vaccination in Canada to assess potential universal vaccination strategies. The model predicts that universal vaccination at age 1 (respectively 4, 9, 15), with phasing out of targeted vaccination, would reduce reported incidence by 60% (respectively 52, 36, 31%) and mortality attributable to HAV by 56% (respectively 45, 26, 25%), relative to continued targeted vaccination, over 80 years.

Most ten-year-old children with negative or unknown histories of chickenpox are immune

To evaluate the proportion of children to vaccinate against varicella in a catch-up program targeting 9- to 10-year-old children, a study was conducted among children age 10 years to assess the age-specific incidence of varicella and document the immunity against varicella in those with negative or unknown chickenpox history. Of the latter 62% were seropositive for varicella.

Detection and quantification of snow algae with an airborne imaging spectrometer

We describe spectral reflectance measurements of snow containing the snow alga Chlamydomonas nivalis and a model to retrieve snow algal concentrations from airborne imaging spectrometer data. Because cells of C. nivalis absorb at specific wavelengths in regions indicative of carotenoids (astaxanthin esters, lutein, beta-carotene) and chlorophylls a and b, the spectral signature of snow containing C. nivalis is distinct from that of snow without algae. The spectral reflectance of snow containing C. nivalis is separable from that of snow without algae due to carotenoid absorption in the wavelength range from 0.4 to 0.58 microm and chlorophyll a and b absorption in the wavelength range from 0.6 to 0.7 microm. The integral of the scaled chlorophyll a and b absorption feature (I(0.68)) varies with algal concentration (C(a)). Using the relationship C(a) = 81019.2 I(0.68) + 845.2, we inverted Airborne Visible Infrared Imaging Spectrometer reflectance data collected in the Tioga Pass region of the Sierra Nevada in California to determine algal concentration. For the 5.5-km(2) region imaged, the mean algal concentration was 1,306 cells ml(-1), the standard deviation was 1,740 cells ml(-1), and the coefficient of variation was 1.33. The retrieved spatial distribution was consistent with observations made in the field. From the spatial estimates of algal concentration, we calculated a total imaged algal biomass of 16.55 kg for the 0.495-km(2) snow-covered area, which gave an areal biomass concentration of 0.033 g/m(2).

The microbial community of Ophrydium versatile colonies: endosymbionts, residents, and tenants

Ophrydium versatile is a sessile peritrichous ciliate (Kingdom Protoctista, class Oligohymenophora, order Peritrichida, suborder Sessilina) that forms green, gelatinous colonies. Chlorophyll a and b impart a green color to Ophrydium masses due to 400-500 Chlorella-like endosymbionts in each peritrich. Ophrydium colonies, collected from two bog wetlands (Hawley and Leverett, Massachusetts) were analyzed for their gel inhabitants. Other protists include ciliates, mastigotes, euglenids, chlorophytes, and heliozoa. Routine constituents include from 50-100,000 Nitzschia per ml of gel and at least four other diatom genera (Navicula, Pinnularia, Gyrosigma, Cymbella) that may participate in synthesis of the gel matrix. Among the prokaryotes are filamentous and coccoid cyanobacteria, large rod-shaped bacteria, at least three types of spirochetes and one unidentified Saprospira-like organism. Endosymbiotic methanogenic bacteria, observed using fluorescence microscopy, were present in unidentified hypotrichous ciliates. Animals found inside the gel include rotifers, nematodes, and occasional copepods. The latter were observed in the water reservoir of larger Ophrydium masses. From 30-46% of incident visible radiation could be attenuated by Ophrydium green jelly masses in laboratory observations. Protargol staining was used to visualize the elongate macronuclei and small micronucleus of O. versatile zooids and symbiotic algal nuclei. Electron microscopic analysis of the wall of the Chlorella-like symbiont suggests that although the Ophrydium zooids from British Columbia harbor Chlorella vulgaris, those from Hawley Bog contain Graesiella sp. The growth habit in the photic zone and loose level of individuation of macroscopic Ophrydium masses are interpretable as extant analogs of certain Ediacaran biota: colonial protists in the Vendian fossil record.

[Lack of conviction about vaccination in certain Quebec vaccinators]

A questionnaire was mailed to all vaccinators in Quebec in 1998. The objective of this survey was to document vaccinators' attitudes, knowledge, and practices related to vaccination. Vaccinators generally believe in the security, efficacy and usefulness of vaccines given to young children. However, 41% of nurses do not fully agree with these opinions. More than 94% of pediatricians completely disagree that "certain practices (homeopathy, good eating habits and a healthy lifestyle) can eliminate the need for vaccination", compared with 85% of general practitioners and only 60% of nurses. Less than 25% of doctors recall children who are late in getting their immunizations; approximately 45% of vaccinators are in complete agreement with simultaneous injections of two vaccines; many circumstances are incorrectly seen as contra indications for vaccination. Public health authorities should target systematic interventions towards vaccinators to improve this situation and to increase nurses' conviction regarding the benefits of vaccination.

Opinions of Quebec parents and vaccinators on the usefulness of chickenpox vaccine

BACKGROUND

A chickenpox vaccine was recently licensed in Canada. Because this vaccine has caused some controversy within the health care profession, studies among Quebec parents and vaccine providers were carried out, surveying their opinions concerning chickenpox vaccination.

METHODS

Three studies among parents of preadolescents, parents of two-year-old children completely or incompletely vaccinated and vaccinators were completed. The studies asked for opinions concerning the usefulness of vaccinating children against chickenpox.

RESULTS

The majority of parents of preadolescents (56%), and parents of two-year-old children completely (64%) and incompletely vaccinated (60%) favoured chickenpox vaccination. Among vaccinators, 53% of paediatricians, 37% of general practitioners and 33% of nurses considered universal vaccination of young children to be useful. A greater proportion of health care professionals were in favour of a policy of vaccinating groups at risk, such as susceptible adolescents (86%, 75% and 58%, respectively). There was a positive association between the perceived severity of chickenpox and the potential usefulness of the vaccine.

CONCLUSION

Quebec parents are more favourably disposed to chickenpox vaccine than vaccine providers. In contrast, strategies targeting susceptible groups would be generally well received by health care professionals. A considerable amount of work will be needed to convince vaccinators of the benefits of a universal childhood vaccination against chickenpox.

Effectiveness of a single dose of acellular pertussis vaccine to prevent pertussis in children primed with pertussis whole cell vaccine

We estimated the protection given by one booster dose of acellular pertussis vaccine (aP) given at 18 months or before school entry to children already primed with whole cell vaccine (wP). Case-control studies were conducted in these two age groups. In children who received or were eligible to receive their 18 months booster, the risk of pertussis was 1.4 and 3.6 times higher for those with 4 and 3 wP, respectively, compared to those with 3 wP + 1 aP. In 5 and 6 yr old children, the risk of pertussis among the subjects with 5 and 4 wP, was 1.4 and 2.1 times higher respectively than in those who received 4 wP + 1 aP. A single dose of aP increased the protection against pertussis and this protection was greater than that obtained with a wP booster.

[Lack of conviction about vaccination in certain Quebec vaccinators]

A questionnaire was mailed to all vaccinators in Quebec in 1998. The objective of this survey was to document vaccinators' attitudes, knowledge, and practices related to vaccination. Vaccinators generally believe in the security, efficacy and usefulness of vaccines given to young children. However, 41% of nurses do not fully agree with these opinions. More than 94% of pediatricians completely disagree that "certain practices (homeopathy, good eating habits and a healthy lifestyle) can eliminate the need for vaccination", compared with 85% of general practitioners and only 60% of nurses. Less than 25% of doctors recall children who are late in getting their immunizations; approximately 45% of vaccinators are in complete agreement with simultaneous injections of two vaccines; many circumstances are incorrectly seen as contra indications for vaccination. Public health authorities should target systematic interventions towards vaccinators to improve this situation and to increase nurses' conviction regarding the benefits of vaccination.

Importance of attributable risk in monitoring adverse events after immunization: hepatitis B vaccination in children

OBJECTIVES

Most vaccine safety data present only the postvaccination incidence of all adverse events rather than an estimate of attributable risk. This study sought to illustrate the difference between the 2 estimates with data from a hepatitis B immunization program.

METHODS

The incidence of health problems occurring before and after each dose of hepatitis B vaccine in a cohort of 1130 children were compared.

RESULTS

Although 47.5% of all children reported an adverse event during the 4 weeks following each of the 3 doses, adverse events attributable to immunization occurred in only 10.6% of children.

CONCLUSIONS

Postimmunization incidence systematically overestimates the risk of adverse events. Estimating actual attributable risk is necessary to avoid false beliefs regarding immunization.

Cerro Negro bitumen degradation by a consortium of marine benthic microorganisms

Cerro Negro bitumen, separated from an Orimulsion sample, was incubated for up to 120 days with sediments collected at a petroleum-impacted site in Tampa Bay, Florida. Biodegradation conditions were optimized by increasing bitumen surface area, continuous agitation on a shaker apparatus, use of a complete growth medium, and maintenance at 37 degrees C. Aerobic degradation conditions were promoted by maintaining sediment contact with the laboratory atmosphere. Bitumen recovered in solvent extracts when compared to autoclaved controls decreased by up to 40% during the first 56 days. There was no detectable change after this. Molasses addition and use of a culture enriched from the sediments did not change the extent or rate of decrease in bitumen recovery. Chemical fractionation of bitumen control and degraded bitumen showed that aromatic and aliphatic fractions were depleted by approximately equals 50%. Accumulation of polars was observed; however, the apparent increase was relatively small when compared to the mass loss of the other fractions. Selected biomarker ratios were not affected by incubation indicating their utility for fingerprinting the source bitumen in environmental samples. PAH distribution in the aromatic fraction favored the higher alkyl-homologues with the relative degree of alkylation increasing as the mass of bitumen recovered decreased with degradation. The study showed that up to 40% of the bitumen was bioaccessible and that bioremediation may be a treatment option for sediments contaminated with bitumen by an Orimulsion spill.

Morbidity of pertussis in adolescents and adults

The effect of age on the clinical presentation of pertussis was assessed in 664 adolescent and adult cases. Complications were more frequent in adults than in adolescents (28% vs. 16%). Pneumonia occurred in 2% of patients <30 years old but in 5%-9% of older patients. Urinary incontinence occurred in 34% of women >/=50 years old. Duration of cough, risk of sinusitis, and number of nights with disturbed sleep increased with smoking and asthma. The secondary attack rate in other household members >/=12 years was 11%. Pertussis in secondary case patients was less severe than in index case patients but presented with classic symptoms. The main source of infection in adolescents was schoolmates or friends; in adults it was workplace or their children. Teachers and health care workers had a greater risk of pertussis than did the general population. The burden of disease appears to increase with age, with smoking, and with asthma.

Methane production and release from two New England peatlands

The rate of methane production and release to the atmosphere was determined for two New England peat bogs. Methane production rates from peat sediments, which were measured down to depths of 150 cm, ranged from 1 to 15 micromoles per liter per hour. The highest rates of methane production occurred at depths of 60-100 cm. Methane release from these same peats was quantified from various habitats on the bog using gas collection chambers. The chambers enclose a two-liter volume and cover an area of 0.02 m2. Methane accumulation in the chambers was measured for periods of up to 18 days. Methane release was related to pH and habitat zone. The lowest rates of methane release were from those portions of the bogs that had pH values below 5.0. Peak methane release occurred during or immediately after ice melt in both wetlands with release rates as high as 34 mmoles/m2/d. The overall estimate of yearly release of methane from these bog systems is 2,900 and 14,900 moles per year for Arcadia and Hawley Bogs respectively. Both of these bogs have pH environments close to the lowest limit for methanogenesis, and small differences in pH values can have a large impact on both the rate of methane production and the rate of methane release to the atmosphere.

Comparative immunogenicity under field conditions of two recombinant hepatitis B vaccines in 8-10-year-old children

The immunogenicity of two hepatitis B vaccines was compared in 8-10-year-old children immunized in a school program. One year apart, 1129 children received Engerix-B 10 microg vaccine (EB), and 1126 received Recombivax-HB 2.5 microg (RB), following the 0, 1, 6 schedule. Blood samples were collected one month after the third dose. Anti-Hbs were measured by commercial radioimmunoassay. In the EB group, 99.1% of the children seroconverted (>/=2 IU/l) compared to 99.7% in the RHB group (p=0.09). The seroprotection rate (>/=10 IU/l) was similar for both groups: 98.9% in the EB group and 99.2% in the RB group (p=0.66). However, GMCs of anti-HBs were higher in children given EB compared to those given RB (7307 vs. 3800 mIU/ml, p<0.0001). This study showed that both vaccines were highly immunogenic, in the course of a regular field immunization program. However, the difference observed in the antibody levels attained according to the vaccine may play a role in the long-term protection of these children.

Protection after two doses of measles vaccine is independent of interval between doses

The protection provided by one or two doses of measles vaccine was compared, as was the effect of the timing of delivery of the doses on the protection provided. A total of 5542 measles cases occurred in Ontario, Canada, between January 1990 and December 1996. Three controls per case were matched for age and residence. Children who received a single dose at age 15 months and older were 5 times more likely to contract measles than were children who received two doses of vaccine after their first birthday. Among children given two doses of vaccines, the risk of measles was 3 times greater in those who had their first vaccination at age 11 months compared with children who first received vaccine after age 1 year, but the protection was independent of the interval between doses. Delaying the second dose >6 months after the first does not increase protection.

Failure of physicians to consider the diagnosis of pertussis in children

To determine the ability of physicians to make a diagnosis of pertussis and factors associated with improved diagnosis, 8,235 children from 88 child care centers and 14 elementary schools from Quebec City, Quebec, Canada, were evaluated by using a questionnaire completed by parents and a medical record review. Children must have consulted a physician to be included in the evaluation. There were 558 children meeting the surveillance case definition and 416 meeting a modified World Health Organization case definition who consulted a physician. A diagnosis of pertussis was considered in 24%-26% of children meeting either case definition, made in 12%-14%, and reported for 6%. Pertussis diagnosis was significantly associated with having a history of pertussis exposure (P < or = .003), four pertussis-related symptoms (P < .001), and a cough for > or = 5 weeks (P < or = .05) and consulting in a hospital setting (P < or = .03). The proportion of cases of pertussis diagnosed and reported is low even when children present with classical symptoms.

Snow algae of the Sierra Nevada, Spain, and High Atlas mountains of Morocco

Snow algae (Chlorophyta) are reported from the Sierra Nevada mountains in southern Spain and the High Atlas mountains of Morocco. Populations of the snow algae Chlamydomonas sp., coloring the snow orange-red, were collected from Pico de Veleta, Spain, while snow samples from Mt. Neltner in the High Atlas mountains, contained resting spores of an orange-green colored Chloromonas sp. Other microbes observed in snow samples include bacteria, fungi, heterotrophic euglenids, diatoms, nematodes, and heterotrophic mastigotes (flagellated protists). This is the first report of snow algae from the Sierra Nevada mountains of Spain and from the Afro-alpine environment.

Effectiveness of a whole cell pertussis vaccine in child-care centers and schools

BACKGROUND

Pertussis has substantially increased in Quebec, Canada, since 1990. We estimated pertussis vaccine effectiveness and vaccine coverage in child-care centers and elementary schools.

METHODS

Two retrospective cohort studies were simultaneously conducted. One included 4482 children attending 88 public child-care centers and the other included 3429 pupils in 14 elementary schools. Cough and pertussis symptoms were assessed through a questionnaire and medical records; immunization status was ascertained by examination of written records.

RESULTS

In child-care centers 95% of children had received at least three vaccine doses at the beginning of the follow-up; in schools more than 98% of pupils had received at least 4 doses. With > or = 4 doses of vaccine and a standard case definition used for surveillance (cough > or = 2 weeks, > or = 1 pertussis symptom and no other apparent cause for cough), vaccine effectiveness was estimated at 61% (95% confidence interval, 44 to 72%) in child-care centers and at 60% (95% confidence interval, 10 to 82%) in schools. With the same number of doses but a case definition requiring a cough > or = 5 weeks, vaccine effectiveness increased to 71% (95% confidence interval, 49 to 83) in child-care centers and to 86% (95% confidence interval, 66 to 94%) in schools.

CONCLUSIONS

The increase in pertussis in Quebec is not caused by a low vaccine coverage. A low vaccine effectiveness may contribute to the resurgence of pertussis in the past decade.

Field effectiveness of erythromycin prophylaxis to prevent pertussis within families

To evaluate the field effectiveness of erythromycin prophylaxis for pertussis within families, a retrospective cohort study was conducted among 246 families. Overall 41% of the subjects (387 of 940) had been sick. The secondary attack rate was 65% for infants younger than 2 years, 54% for those 2 to 4 years old and 39% for children 5 to 9 years old, and it declined thereafter. The secondary attack rate decreased from 25% in families without prophylaxis to 17% in families with prophylaxis. The protection induced by prophylaxis did not vary with age or vaccination status. When prophylaxis was used before the onset of a secondary case, the secondary attack rate was 4% compared with 35% when given after a secondary case (P < 0.001). Erythromycin prophylaxis seems to be efficient in preventing secondary cases but is most useful when administered before the occurrence of the first secondary case.

Measles, mumps, and rubella antibodies in children 5-6 years after immunization: effect of vaccine type and age at vaccination

The levels of antibody against measles, mumps, and rubella were determined at 5-6 years postimmunization in 468 children vaccinated with two different trivalent vaccines. The proportions of children without detectable antibody levels were 12 and 3.6% for measles (p < 0.001), 14.9 and 7% for mumps (p = 0.006), and 3.3 and 3.1% for rubella (p = 0.88), respectively, in MMR II and Trivirix recipients. A higher proportion of those vaccinated at younger ages had undetectable or low levels of measles antibody. These data indicate that a large proportion of children vaccinated under routine conditions do not have detectable measles and mumps antibody.

Need for vaccination of sewer workers against leptospirosis and hepatitis A

OBJECTIVES

This study compared the prevalence of Leptospira interrogans and hepatitis A virus (HAV) antibodies in serum samples from sewer workers and controls.

METHODS

A blood sample was obtained from 76 of the 101 municipal sewer workers (75%) of Quebec City and from two controls matched to each for age and sex. Testing was done for antibodies against serovars of Leptospira icterohaemorragiae, bratislava, hardjo, grippotyphosa, and kennewicki (pomona) and hepatitis A.

RESULTS

Sewer workers had a greater prevalence of antibodies against leptospirosis than controls (12% v 2%, P = 0.003). In contrast, antibodies to HAV were not significantly more prevalent among workers than among controls (54% v 49%, P = 0.51). Prevalence of HAV antibodies increased significantly with age both among workers and controls (chi 2 for trend, P < 0.001). In contrast with younger workers, prevalence of HAV antibodies was greater among workers > or = 40 years than among their controls (81% v 65%, P = 0.04).

CONCLUSION

Leptospirosis continues to be a problem to sewer workers but hepatitis A is apparently no longer a risk. The likely explanation is that leptospira are still abundant in the sewage system in contrast with HAV, which is only rarely to be found in sewage as a result of the generalised decrease in incidence of hepatitis A in the past three decades. The decision to vaccinate sewer workers against hepatitis A should take into account that it is impossible to avoid all contact with sewage fluid and, despite the fact that the actual incidence of hepatitis A is low, there is a real possibility of sporadic exposure during a future outbreak.

Seroepidemiologic study of three zoonoses (leptospirosis, Q fever, and tularemia) among trappers in Québec, Canada

This study was undertaken to evaluate the prevalence of antibodies against Francisella tularensis, Coxiella burnetii, and certain serovars of Leptospira interrogans among trappers in Québec, Canada. Muskrat trapping was identified as a risk factor for F. tularensis infection, whereas having a cat at home apparently protected trappers against infection by L. interrogans. High percentages of control sera were positive for antibodies against C. burnetii (15%) and L. interrogans (5%), most frequently serovar bratislava. This is the first report of human infection by serovar bratislava in North America.

[The opinions of Quebec physicians regarding AIDS: Part II]

Based on a representative sample of Quebec physicians (n = 879), this study assesses physicians' motivation to perform a clinical examination on an HIV-infected patient and their opinion about issues related to HIV screening. Confronted with an HIV-infected patient, 70% of physicians would perform a clinical examination; however, more senior medical specialists with fewer contacts with patients seem less inclined to perform a clinical examination on these patients. Almost 80% agree with a mandatory nominal confidential notification of positive HIV screenees. However, 33% agree with the practice of contact tracing and 40% consider it acceptable to test a patient without his or her explicit consent. Even if Canada does not regulate the testing of immigrants for HIV, more than 75% of the respondents agree with such a policy. Finally, a negative association was observed between the intent to perform a clinical examination on an HIV-infected patient and a favourable attitude toward the screening of immigrants and the testing of patients without their consent.

[The opinion of Quebecois physicians with regard to AIDS]

A mail survey on several medical and social issues surrounding the AIDS epidemic was conducted among Québec physicians of a random sample. Of 1,530 physicians, 879 (57.5%) returned their completed questionnaire. Results show that the majority of physicians (79.3%) considered AIDS as a priority. A large proportion of physicians (66%) overestimate the occupational risk of contracting HIV following exposure to a contaminated needle. Logistic regression suggests that the perceived risk of contracting HIV through contact with patients is directly related to the physicians' type of medical training and to their estimate of the risk of contamination with a contaminated needle. Finally, a third of the respondents consider continuing medical education on AIDS insufficient in the Province of Québec while 82.1% want to improve their knowledge about AIDS.

Frequency of sexually transmitted diseases among university students

OBJECTIVE

To estimate the incidence rate of sexually transmitted diseases (STDs) among university students and evaluate the associated sociodemographic factors.

DESIGN

Mail survey in April 1990. Included in the questionnaire were questions about the subjects' STD experience since their admission to the university and the type and date of the infection.

SUBJECTS

Of the 19,682 undergraduate students 2920 subjects, in 10 groups of 292, were randomly selected. A total of 1731 (59.4%) completed the questionnaire.

MAIN OUTCOME MEASURES

Estimated annualized incidence rates of genital human papillomavirus infection and Chlamydia infection.

RESULTS

The estimated annualized incidence rates of genital human papillomavirus and Chlamydia infections were 2.2% and 1.5% respectively. Among the students who indicated being infected with genital human papillomavirus 59% were 18 to 21 years old (p < 0.05), 76% were women (p < 0.01) and 69% had more than one sexual partner (p < 0.01). No statistically significant associations were observed between age, sex and Chlamydia infection. On the other hand, 95% of the cases of Chlamydia infection were found among those who had more than one sexual partner (p < 0.01).

CONCLUSION

University students continue to have sexual activities at risk for STDs and should be specifically targetted by general practitioners and health services in an effort to slow the spread of STDs.

[Knowledge and attitude to sexually transmitted diseases and condoms in students and undergraduate students]

Since sexually transmitted diseases (STDs) are a serious health problem among youth, proper understanding of knowledge about STDs, beliefs about condom use and associated factors are public health necessities. A self-administered questionnaire was sent to 2,920 randomly selected students and was returned by 59.3% of the sample. We observed a lack of knowledge in one third of students, negative beliefs on condom use for at least 20% of students and a low perceived risk to contract STDs. With multivariate analyses, we observed that male students, youths between 18-21 years of age and those who didn't have any sexual partner since their admission to the university should be the target of intervention programs.