High prevalence of Aleutian mink disease virus in free-ranging mink on a remote Danish island.

Aleutian mink disease virus (AMDV) causes severe disease in farmed mink (Neovison vison) worldwide. In Denmark, AMDV in farmed mink has been confined to the northern part of the mainland since 2002. From 1998 to 2009, samples from 396 free-ranging mink were collected from mainland Denmark, and a low AMDV antibody prevalence (3% of 296) was found using countercurrent immune electrophoresis. However, on the island of Bornholm in the Baltic Sea, a high prevalence (45% of 142 mink) was detected in the free-ranging mink. Aleutian mink disease virus was detected by polymerase chain reaction in 32 of 49 antibody-positive free-ranging mink on Bornholm, but not in mink collected from other parts of Denmark. Sequence analysis of 370 base pairs of the nonstructural gene of the AMDV of 17 samples revealed two clusters with closest similarity to Swedish AMDV strains.

Implementation and validation of a sensitive PCR detection method in the eradication campaign against Aleutian mink disease virus.

Aleutian mink disease virus (AMDV) is a severe progressive disease causing multiple different clinical syndromes in mink. In Denmark, the disease is notifiable and under official control. The control programme, based on serological screening, has confined successfully AMDV to the northern part of Denmark. However, re-infections and new introductions of virus into farms require a confirmatory virological test to verify the positive test results of single animals and ultimately to investigate disease transmission. A one step PCR amplifying a 374-base fragment of the NS1 gene of AMDV was compared to the counter-current immune electrophoresis (CIE) routinely used in the serological screening programme. Mink organs (n=299) obtained from 55 recently infected farms and 8 non-infected farms from 2008 to 2010 were tested by PCR, and the results were found to have a high correlation with the serological status of the mink. The relative diagnostic sensitivity of the PCR was 94.7%, and the relative diagnostic specificity was 97.9% when read in parallel with the CIE. PCR positive samples were sequenced and phylogenetic analysis revealed high similarity within the analysed AMDV strains and to AMDV strains described previously.

Pregnancy loss ascribable to parvovirus B19/erythrovirus is associated with a high prevalence of trisomy.

INTRODUCTION: In most cases of stillbirth, the cause is still unknown. AIM: The impact of parvovirus B19/erythrovirus infection and chromosomal abnormalities in stillborns and neonatal deaths. MATERIAL AND METHODS: 57 consecutive cases, 23 second-trimester abortions (from gestational weeks 16 to 22), 27 intrauterine fetal deaths (from gestational week 22 onwards) and 7 early neonatal deaths were examined for intrauterine parvovirus B19 infection with PCR, dot blot, Southern blot, in situ hybridization, specific IgM and IgG antibodies in maternal serum, fetal serum, placenta and fetal liver tissue. Chromosomal analysis and extensive histopathology were performed on all fetuses. RESULTS: A sensitive PCR was developed and enabled detection of 9 (15.8%) parvovirus B19-infected fetuses. Parvovirus B19 IgM and IgG antibody tests were in good concordance with PCR findings. 5 of 9 infected fetuses had a concurrent abnormality that could have contributed to fetal death, 4 of which (44%) were trisomy karyotypes, compared to 0/48 in the non-B19-infected group (p = 0.0004). CONCLUSION: Combination of PCR and specific parvovirus B19 IgG/IgM tests enabled high detection rates of parvovirus B19 infection in this series of 57 consecutive pregnancies with adverse outcomes. The high mortality rate in the B19-infected fetuses was partly explained by a high occurrence of fetal trisomy, compared to non-B19-infected fetuses, suggesting a higher vulnerability of the former. After correction for this concomitant karyotype abnormality, the percentage of presumably lethal infection due to parvovirus B19 was 8.8%.

Detection of Campylobacter bacteria in air samples for continuous real-time monitoring of Campylobacter colonization in broiler flocks.

Improved monitoring tools are important for the control of Campylobacter bacteria in broiler production. In this study, we compare the sensitivities of detection of Campylobacter by PCR with feces, dust, and air samples during the lifetimes of broilers in two poultry houses and conclude that the sensitivity of detection of Campylobacter in air is comparable to that in other sample materials. Profiling of airborne particles in six poultry houses revealed that the aerodynamic conditions were dependent on the age of the chickens and very comparable among different poultry houses, with low proportions of particles in the 0.5- to 2-microm-diameter range and high proportions in the 2- to 5-microm-diameter range. Campylobacter could also be detected by PCR in air samples collected at the hanging stage during the slaughter process but not at the other stages tested at the slaughterhouse. The exploitation of airborne dust in poultry houses as a sample material for the detection of Campylobacter and other pathogens provides an intriguing possibility, in conjunction with new detection technologies, for allowing continuous or semicontinuous monitoring of colonization status.

The molecular epidemiology of foot-and-mouth disease virus serotypes A and O from 1998 to 2004 in Turkey.

BACKGROUND: Foot-and-Mouth Disease (FMD) causes significant economic losses in Turkish livestock. We have analysed the genetic diversity of the 1D sequences, encoding the hypervariable surface protein VP1, of Turkish isolates of serotype A and O collected from 1998 to 2004 in order to obtain epidemiological and immunological information. RESULTS: The 1D coding region of 33 serotype O and 20 serotype A isolates, obtained from outbreaks of FMD between 1998 and 2004, was sequenced. For serotype A, we confirmed the occurrence of the two subtypes IRN99 and IRN96. These subtypes are most divergent within the region encoding the immuno-dominant GH-loop. Also a close relationship to Foot-and-Mouth Disease virus (FMDV) serotype A isolates obtained from outbreaks in Iraq and Iran were detected and a clustering of isolates collected during the same period of time were found. The analysis of the deduced amino-acid sequences of these subtypes revealed evidence of positive selection in one site and one deletion, both within the GH-loop region. By inferring the ancestral history of the positively selected codon, two potential precursors were found. Furthermore, the structural alignment of IRN99 and IRN96 revealed differences between the tertiary structures of these subtypes. The similarity plot of the serotype O isolates suggested a more homogeneous group than the serotype A isolates. However, phylogenetic analysis revealed two major groups, each further divided in subgroups, of which some only consisted of Turkish isolates. Positively selected sites and structural differences of the Turkish isolates analysed, were not found. CONCLUSION: The sequence and structural analysis of the IRN99 strains is indicative of positive selection suggesting an immunological advantage compared to IRN96. However, results of antigenic comparison reported elsewhere do not substantiate such a conclusion. There is evidence that IRN99 was introduced to Turkey, in all probability from Iran. Since, a member of the IRN96 lineage was included as a component of the FMDV vaccine produced since 2000, the outbreaks caused by IRN96 strains in 2004 could be due to incomplete vaccine coverage. The Turkish type O strains, all with a VP1 structure similar to the O1/Manisa/69 vaccine, appear in several sublineages. Whether these sublineages reflect multiple samplings from a limited number of outbreaks, or if they reflect cross-boundary introductions is not clear.

Evidence of recombination among early-vaccination era measles virus strains.

BACKGROUND: The advent of live-attenuated vaccines against measles virus during the 1960'ies changed the circulation dynamics of the virus. Earlier the virus was indigenous to countries worldwide, but now it is mediated by a limited number of evolutionary lineages causing sporadic outbreaks/epidemics of measles or circulating in geographically restricted endemic areas of Africa, Asia and Europe. We expect that the evolutionary dynamics of measles virus has changed from a situation where a variety of genomic variants co-circulates in an epidemic with relatively high probabilities of co-infection of the individual to a situation where a co-infection with strains from evolutionary different lineages is unlikely. RESULTS: We performed an analysis of the partial sequences of the hemagglutinin gene of 18 measles virus strains collected in Denmark between 1965 and 1983 where vaccination was first initiated in 1987. The results were compared with those obtained with strains collected from other parts of the world after the initiation of vaccination in the given place. Intergenomic recombination among pre-/early-vaccination strains is suggested by 1) estimations of linkage disequilibrium between informative sites, 2) the decay of linkage disequilibrium with distance between informative sites and 3) a comparison of the expected number of homoplasies to the number of apparent homoplasies in the most parsimonious tree. No significant evidence of recombination could be demonstrated among strains circulating at present. CONCLUSION: We provide evidence that recombination can occur in measles virus and that it has had a detectable impact on sequence evolution of pre-vaccination samples. We were not able to detect recombination from present-day sequence surveys. We believe that the decreased rate of visible recombination may be explained by changed dynamics, since divergent strains do not meet very often in current epidemics that are often spawned by a single sequence type. Signs of pre-vaccination recombination events in the present-day sequences are not strong enough to be detectable.

Analysis of the epidemiological dynamics during the 1982-1983 epidemic of foot-and-mouth disease in Denmark based on molecular high-resolution strain identification.

An epidemic of foot-and-mouth disease (FMD) causing a total of 23 cases in 1982-1983, primarily on the island of Funen, Denmark, was subjected to molecular epidemiological investigations. In an attempt to exploit the quasi-species nature of foot-and-mouth disease virus strains for molecular high-resolution strain identification in order to analyse the dynamics of this epidemic, full-length VP1 coding regions were sequenced for 17 isolates collected at different farms during the epidemic. The sequence information together with epidemiological information gathered during the epidemic suggests that the epidemic was caused by at least three introductions across Danish borders and one case of airborne transmission between two islands in Denmark over a distance of 70 km. The assortment of nucleotide markers among the three strains is indicative of common recombination events in their evolutionary history, and the prerequisite of co- or superinfection of animals with variant strains in turn implies that they have a common source or epidemiologically related sources originating from an area with endemic FMD.

Presence and significance of TT virus in Danish patients on maintenance hemodialysis.

OBJECTIVES: To determine the prevalence of TT virus (TTV) in a population of Danish hemodialysis patients and evaluate possible relations between TTV infection and elevated levels of C-reactive protein (CRP) and hypo-response to treatment with erythropoietin (EPO). MATERIAL AND METHODS: Patients on maintenance hemodialysis at a single center were invited to participate. Demographic and clinical data were registered. Blood samples for virological and routine biochemical tests were drawn simultaneously. TTV DNA was detected using polymerase chain reaction (PCR). TTV viral load was estimated by means of semi-quantitative PCR. All patients were tested for hepatitis B, hepatitis C and GB virus C. RESULTS: Of 252 patients, 204 (80.9%) gave their written informed consent to participate in the study. The prevalence of TTV was 68% and 50% of TTV-positive patients had a high TTV viral load. TTV-positive patients were significantly older than TTV-negative patients (p = 0.011). No relations were found between TTV infection and elevated levels of alanine aminotransferase (ALT) or CRP or hypo-response to EPO treatment. The mean hemoglobin concentration was 11.24 +/- 1.48 g/dl. Patients with a high TTV viral load had a lower level of hemoglobin (10.86 +/- 1.47 g/dl) than the others (p = 0.01). This trend suggested a positive relation between TTV infection and the number of blood transfusions. A restriction fragment length polymorphism assay suggested that patients were infected with different TTV strains. CONCLUSIONS: TTV is common in patients on maintenance hemodialysis. The presence of TTV is associated with increasing age. Patients with a high TTV viral load had lower levels of hemoglobin than the others. TTV infection is not related to elevated levels of ALT or CRP or to hypo-response to EPO treatment.