Bovine viral diarrhea virus in free-ranging wild ruminants in Switzerland: low prevalence of infection despite regular interactions with domestic livestock

ABSTRACT: BACKGROUND: In the frame of an eradication program for bovine viral diarrhea (BVD) in Swiss livestock, the question was raised whether free-ranging wildlife could threaten the success of this sanitary measure. Therefore, we conducted serological and virological investigations on BVD virus (BVDV) infections in the four indigenous wild ruminant species (roe deer, red deer, Alpine chamois and Alpine ibex) from 2009 to 2011, and gathered information on interactions between wild and domestic ruminants in an alpine environment by questionnaire survey. RESULTS: Thirty-two sera out of 1'877 (1.7%, 95% confidence interval [CI] 1.2-2.4) were seropositive for BVDV, and a BVDV1 sub genotype h virus was found in a seropositive chamois (0.05%, 95% CI 0.001-0.3). The seropositive animals originated from sub-alpine or alpine regions and significantly more seropositive red deer, chamois and ibex than roe deer were found. There were no statistically significant differences between sampling units, age classes, genders, and sampling years. The obtained prevalences were significantly lower than those documented in livestock, and most positive wild ruminants were found in proximity of domestic outbreaks. Additionally, BVDV seroprevalence in ibex was significantly lower than previously reported from Switzerland. The survey on interspecific interactions revealed that interactions expected to allow BVDV transmission, from physical contacts to non-simultaneous use of the same areas, regularly occur on pastures among all investigated ruminant species. Interactions involving cervids were more often observed with cattle than with small ruminants, chamois were observed with all three domestic species, and ibex interacted mostly with small ruminants. Interactions related to the use of anthropogenic food sources were frequently observed, especially between red deer and cattle in wintertime. CONCLUSIONS: To our knowledge, this is the first report of BVDV RNA isolated from an Alpine chamois. Nevertheless, our results suggest that BVDV infections are only sporadic in Swiss wild ruminants, despite regular occurrence of interactions with potentially infected livestock. Overall, serological, virological and ethological data indicate that wildlife is currently an incidental spill-over host and not a reservoir for BVDV in Switzerland.

Changes in Chemical Composition and Digestion Kinetics of Stockpiled Kura Clover in Late Fall

Stockpiled kura clover samples harvested on three different winter dates were used to determine changes in chemical composition and N digestion kinetics. Kura clover was harvested from four different plots at 14 d intervals and analyzed for neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), acid detergent insoluble nitrogen (ADIN), and in vitro digestible dry matter (IVDMD), and in situ digestion kinetics of N. Crude protein concentrations decreased, but ADIN concentrations increased with later date of harvest. Digestible N pool-size and the rate of digestion was the lowest in third-harvest kura clover. Although the proportion of protein that is soluble or nondigestible increased, proportion of protein that is potentially digestible decreased with maturity.

Kinetics of maternally acquired anti-hepatitis A antibodies: prediction of waning based on maternal or cord blood antibody levels

BACKGROUND Timing is critical for efficient hepatitis A vaccination in high endemic areas as high levels of maternal IgG antibodies against the hepatitis A virus (HAV) present in the first year of life may impede the vaccine response. OBJECTIVES To describe the kinetics of the decline of anti-HAV maternal antibodies, and to estimate the time of complete loss of maternal antibodies in infants in León, Nicaragua, a region in which almost all mothers are anti-HAV seropositive. METHODS We collected cord blood samples from 99 healthy newborns together with 49 corresponding maternal blood samples, as well as further blood samples at 2 and 7 months of age. Anti-HAV IgG antibody levels were measured by enzyme immunoassay (EIA). We predicted the time when antibodies would fall below 10 mIU/ml, the presumed lowest level of seroprotection. RESULTS Seroprevalence was 100% at birth (GMC 8392 mIU/ml); maternal and cord blood antibody concentrations were similar. The maternal antibody levels of the infants decreased exponentially with age and the half-life of the maternal antibody was estimated to be 40 days. The relationship between the antibody concentration at birth and time until full waning was described as: critical age (months)=3.355+1.969 × log(10)(Ab-level at birth). The survival model estimated that loss of passive immunity will have occurred in 95% of infants by the age of 13.2 months. CONCLUSIONS Complete waning of maternal anti-HAV antibodies may take until early in the second year of life. The here-derived formula relating maternal or cord blood antibody concentrations to the age at which passive immunity is lost may be used to determine the optimal age of childhood HAV vaccination.

Differences in primary sites of infection between zoonotic and human tuberculosis: results from a worldwide systematic review.

Tuberculosis (TB) is one of the most devastating infectious diseases worldwide. Whilst global burden estimates for M. tuberculosis infection (MtTB) are well established, accurate data on the contribution of zoonotic TB (zTB) caused by M. bovis or M. caprae to human TB are scarce. The association of M. bovis infection with extrapulmonary tuberculosis has been suggested repeatedly, though there is little scientific evidence available to support this relationship. The present study aimed to determine globally the occurrence of extrapulmonary TB and the primary site (i.e. primary body location affected) of zTB in comparison with MtTB, based on previously published reports. A systematic literature review was conducted in 32 different bibliographic databases, selecting reports on zTB written in English, French, German, Spanish or Portuguese. Data from 27 reports from Africa, America, Europe and the Western Pacific Region were extracted for analyses. Low income countries, in Africa and South-East Asia, were highly underrepresented in the dataset. The median proportion of extrapulmonary TB cases was significantly increased among zTB in comparison with data from registries of Europe and USA, reporting mainly MtTB cases (47% versus 22% in Europe, 73% versus 30% in the USA). These findings were confirmed by analyses of eight studies reporting on the proportions of extrapulmonary TB in comparable populations of zTB and MtTB cases (median 63% versus 22%). Also, disparities of primary sites of extrapulmonary TB between zTB and MtTB were detected. Our findings, based on global data, confirm the widely suggested association between zTB and extrapulmonary disease. Different disability weights for zTB and MtTB should be considered and we recommend separate burden estimates for the two diseases.

Observed management practices in relation to the risk of infection with paratuberculosis and to the spread of Mycobacterium avium subsp. paratuberculosis in Swiss dairy and beef herds

Abstract BACKGROUND: Many studies have been conducted to define risk factors for the transmission of bovine paratuberculosis, mostly in countries with large herds. Little is known about the epidemiology in infected Swiss herds and risk factors important for transmission in smaller herds. Therefore, the presence of known factors which might favor the spread of paratuberculosis and could be related to the prevalence at animal level of fecal shedding of Mycobacterium avium subsp. paratuberculosis were assessed in 17 infected herds (10 dairy, 7 beef). Additionally, the level of knowledge of herd managers about the disease was assessed. In a case-control study with 4 matched negative control herds per infected herd, the association of potential risk factors with the infection status of the herd was investigated. RESULTS: Exposure of the young stock to feces of older animals was frequently observed in infected and in control herds. The farmers' knowledge about paratuberculosis was very limited, even in infected herds. An overall prevalence at animal level of fecal shedding of Mycobacterium avium subsp. paratuberculosis of 6.1% was found in infected herds, whereby shedders younger than 2 years of age were found in 46.2% of the herds where the young stock was available for testing. Several factors related to contamination of the heifer area with cows' feces and the management of the calving area were found to be significantly associated with the within-herd prevalence. Animal purchase was associated with a positive herd infection status (OR = 7.25, p = 0.004). CONCLUSIONS: Numerous risk factors favoring the spread of Mycobacterium avium subsp. paratuberculosis from adult animals to the young stock were observed in infected Swiss dairy and beef herds, which may be amenable to improvement in order to control the disease. Important factors were contamination of the heifer and the calving area, which were associated with higher within-herd prevalence of fecal shedding. The awareness of farmers of paratuberculosis was very low, even in infected herds. Animal purchase in a herd was significantly associated with the probability of a herd to be infected and is thus the most important factor for the control of the spread of disease between farms.

Stability and kinetics of nucleic acid triplexes with chimaeric DNA/RNA third strands

A series of chimaeric DNA/RNA triplex-forming oligonucleotides (TFOs) with identical base-sequence but varying sequential composition of the sugar residues were prepared. The structural, kinetic and thermodynamic properties of triplex formation with their corresponding double-helical DNA target were investigated by spectroscopic methods. Kinetic and thermodynamic data were obtained from analysis of non-equilibrium UV-melting- and annealing curves in the range of pH 5.1 to 6.7 in a 10 mM citrate/phosphate buffer containing 0.1M NaCl and 1 mM EDTA. It was found that already single substitutions of ribo- for deoxyribonucleotides in the TFOs greatly affect stability and kinetics of triplex formation in a strongly sequence dependent manner. Within the sequence context investigated, triplex stability was found to increase when deoxyribonucleotides were present at the 5'-side and ribonucleotides in the center of the TFO. Especially the substitution of thymidines for uridines in the TFO was found to accelerate both, the association and dissociation process, in a strongly position-dependent way. Differential structural information on triplexes and TFO single-strands was obtained from CD-spectroscopy and gel mobility experiments. Only minor changes were observed in the CD spectra of the triplexes at all pH values investigated, and the electrophoretic mobility was nearly identical in all cases, indicating a high degree of structural similarity. In contrast, the single-stranded TFOs showed high structural variability as determined in the same way. The results are discussed in the context of the design of TFOs for therapeutic or biochemical applications.

Model for ranking freshwater fish farms according to their risk of infection and illustration for viral haemorrhagic septicaemia

We developed a model to calculate a quantitative risk score for individual aquaculture sites. The score indicates the risk of the site being infected with a specific fish pathogen (viral haemorrhagic septicaemia virus (VHSV); infectious haematopoietic necrosis virus, Koi herpes virus), and is intended to be used for risk ranking sites to support surveillance for demonstration of zone or member state freedom from these pathogens. The inputs to the model include a range of quantitative and qualitative estimates of risk factors organised into five risk themes (1) Live fish and egg movements; (2) Exposure via water; (3) On-site processing; (4) Short-distance mechanical transmission; (5) Distance-independent mechanical transmission. The calculated risk score for an individual aquaculture site is a value between zero and one and is intended to indicate the risk of a site relative to the risk of other sites (thereby allowing ranking). The model was applied to evaluate 76 rainbow trout farms in 3 countries (42 from England, 32 from Italy and 2 from Switzerland) with the aim to establish their risk of being infected with VHSV. Risk scores for farms in England and Italy showed great variation, clearly enabling ranking. Scores ranged from 0.002 to 0.254 (mean score 0.080) in England and 0.011 to 0.778 (mean of 0.130) for Italy, reflecting the diversity of infection status of farms in these countries. Requirements for broader application of the model are discussed. Cost efficient farm data collection is important to realise the benefits from a risk-based approach.

Towards harmonised procedures in wildlife epidemiological investigations: A serosurvey of infection with Mycobacterium bovis and closely related agents in wild boar (Sus scrofa) in Switzerland

Bovine tuberculosis (bTB) is a (re-)emerging disease in European countries, including Switzerland. This study assesses the seroprevalence of infection with Mycobacterium bovis and closely related agents in wild boar (Sus scrofa) in Switzerland, because wild boar are potential maintenance hosts of these pathogens. The study employs harmonised laboratory methods to facilitate comparison with the situation in other countries. Eighteen out of 743 blood samples tested seropositive (2.4%, CI: 1.5-3.9%) by ELISA, and the results for 61 animals previously assessed using culture and PCR indicated that this serological test was not 100% specific for M. bovis, cross-reacting with M. microti. Nevertheless, serology appears to be an appropriate test methodology in the harmonisation of wild boar testing throughout Europe. In accordance with previous findings, the low seroprevalence found in wild boar suggests wildlife is an unlikely source of the M. bovis infections recently detected in cattle in Switzerland. This finding contrasts with the epidemiological situation pertaining in southern Spain.

The burden of parainfluenza virus infection in patients with hematological malignancy and hematopoietic stem cell transplant (HSCT) recipients in the absence of active immunization and approved therapy: The role of infection control

Background. Community respiratory viruses, mainly RSV and influenza, are significant causes of morbidity and mortality in patients with leukemia and HSCT recipients. The data on impact of PIV infections in these patients is lacking. Methods. We reviewed the records of patients with leukemia and HSCT recipients who developed PIV infection from Oct'02–Nov'07 to determine the outcome of such infections. Results. We identified 200 patients with PIV infections including 80(40%) patients with leukemia and 120 (60%) recipients of HSCT. Median age was 55 y (17-84 y). As compared to HSCT recipients, patients with leukemia had higher APACHE II score (14 vs. 10, p<0.0001); were more likely to have ANC<500 (48% vs. 10%, p<0.0001) and ALC<200 (45% vs. 23.5%, p=0.02). PIV type III was the commonest isolate (172/200, 86%). Most patients 141/200 (70%) had upper respiratory infection (URI), and 59/200 (30%) had pneumonia at presentation. Patients in leukemia group were more likely to require hospitalization due to PIV infection (77% vs. 36% p=0.0001) and were more likely to progress to pneumonia (61% vs. 39%, p=0.002). Fifty five patients received aerosolized ribavirin and/or IVIG. There were no significant differences in the duration of symptoms, length of hospitalization, progression to pneumonia or mortality between the treated verses untreated group. The clinical outcome was unknown in 13 (6%) patients. Complete resolution of symptoms was noted in 91% (171/187) patients and 9% (16/187) patients died. Mortality rate was 17% (16/95) among patients who had PIV pneumonia, with no significant difference between leukemia and HSCT group (16% vs. 17%). The cause of death was acute respiratory failure and/or multi-organ failure in (13, 81%) patients. Conclusions. Patients with leukemia and HSCT could be at high risk for serious PIV infections including PIV pneumonia. Treatment with aerosolized ribavirin and/or IVIG may not have significant effect on the outcome of PIV infection.^

POPULATION ASSESSMENTS OF INFECTION WITH SCHISTOSOMA MANSONI: EFFECTS OF BIAS CAUSED BY THE RELATIVE SENSITIVITY OF DIAGNOSTIC TECHNIQUES (PUERTO RICO)

This study establishes the extent and relevance of bias of population estimates of prevalence, incidence, and intensity of infection with Schistosoma mansoni caused by the relative sensitivity of stool examination techniques. The population studied was Parcelas de Boqueron in Las Piedras, Puerto Rico, where the Centers for Disease Control, had undertaken a prospective community-based study of infection with S. mansoni in 1972. During each January of the succeeding years stool specimens from this population were processed according to the modified Ritchie concentration (MRC) technique. During January 1979 additional stool specimens were collected from 30 individuals selected on the basis of their mean S. mansoni egg output during previous years. Each specimen was divided into ten 1-gm aliquots and three 42-mg aliquots. The relationship of egg counts obtained with the Kato-Katz (KK) thick smear technique as a function of the mean of ten counts obtained with the MRC technique was established by means of regression analysis. Additionally, the effect of fecal sample size and egg excretion level on technique sensitivity was evaluated during a blind assessment of single stool specimen samples, using both examination methods, from 125 residents with documented S. mansoni infections. The regression equation was: Ln KK = 2.3324 + 0.6319 Ln MRC, and the coefficient of determination (r('2)) was 0.73. The regression equation was then utilized to correct the term "m" for sample size in the expression P ((GREATERTHEQ) 1 egg) = 1 - e('-ms), which estimates the probability P of finding at least one egg as a function of the mean S. mansoni egg output "m" of the population and the effective stool sample size "s" utilized by the coprological technique. This algorithm closely approximated the observed sensitivity of the KK and MRC tests when these were utilized to blindly screen a population of known parasitologic status for infection with S. mansoni. In addition, the algorithm was utilized to adjust the apparent prevalence of infection for the degree of functional sensitivity exhibited by the diagnostic test. This permitted the estimation of true prevalence of infection and, hence, a means for correcting estimates of incidence of infection. ^