Occupational risk factors for infection with parvovirus B19 among pregnant women

Oral fluid: Non-invasive alternative for parvovirus B19 diagnosis?

BACKGROUND

Infections with parvovirus B19 (B19V) have been associated with a wide range of disease manifestations of which erythema infectiosum (fifth disease) in children is most common. Clinical signs following infection of children with B19V can be similar to measles and rubella. Laboratory detection of B19V infections is based on detection of B19V-specific IgM antibodies by enzyme immunoassay (IgM-EIA) and/or B19V DNA by quantitative PCR (qPCR) on blood samples. The need for invasive sampling can be a barrier for public health diagnostics.

OBJECTIVES

To evaluate the use of a dual target B19V-qPCR directed against the NS1 and VP2 of B19V on oral fluid samples as a non-invasive alternative for laboratory diagnosis of B19V infections in children below 12 years of age with exanthema.

STUDY DESIGN

Oral fluid and serum samples were collected from 116 children with exanthema. All serum samples were tested by IgM-EIA/IgG-EIA, while all oral fluid and 56 serum samples were tested by B19V-qPCR.

RESULTS

B19V-specific IgM antibodies were detected in 25 of 116 children in the study. B19V DNA was detected in oral fluid in 17 of the 25 children who were IgM positive, as well as two children who were IgM-equivocal or negative. The child with the equivocal IgM had a high quantity of B19V DNA in oral fluid (7 log IU/ml), compatible with an acute B19V infection. The IgM-negative child was IgG-positive and 4 log IU/ml B19V DNA was detected in the oral fluid sample, suggesting an acute infection and a falsely negative IgM. Sample size calculations indicated that oral fluid samples for qPCR should be collected from 2 to 3 children during outbreaks of exanthema to achieve similar sensitivity as IgM-EIA for one child (≥0.9) to confirm or exclude B19V.

CONCLUSIONS

Results indicate that oral fluid samples are a suitable public health alternative for detection of B19V infections, potentially lowering the barriers for sampling.

Human Parvoviruses

Parvovirus B19 (B19V) and human bocavirus 1 (HBoV1), members of the large Parvoviridae family, are human pathogens responsible for a variety of diseases. For B19V in particular, host features determine disease manifestations. These viruses are prevalent worldwide and are culturable in vitro, and serological and molecular assays are available but require careful interpretation of results. Additional human parvoviruses, including HBoV2 to -4, human parvovirus 4 (PARV4), and human bufavirus (BuV) are also reviewed. The full spectrum of parvovirus disease in humans has yet to be established. Candidate recombinant B19V vaccines have been developed but may not be commercially feasible. We review relevant features of the molecular and cellular biology of these viruses, and the human immune response that they elicit, which have allowed a deep understanding of pathophysiology.

[Parvovirus B19 infection and pregnancy]

"Small virus" contagious during spring, parvovirus B19 is responsible for fifth disease of children. The prevalence of infection is very high before 10 years old and children are especially responsible for transmission to pregnant women. Approximately 50% of women old enough to procreate have stigmas serologic of old infection. Acquired immunity is long hasting and solid. During pregnancy, this virus is responsible for abortion, fetal anemia. Severe anemia can cause hydrops fetalis or fetal mortality in utero or neurologic damage. We are going to start again point by point of the contage has the care the situations with which the doctor can be confronted during the pregnancy.

Increased risk of human parvovirus B19 infection in day-care employees: a cohort study among pregnant workers during an epidemic in Finland

BACKGROUND

Human parvovirus B19 (B19V) infection during early pregnancy increases the risk of miscarriage. Studies have inconsistently shown an elevated risk of infection among women with occupational contacts with children. Methodological differences, particularly in defining occupational exposure and in the type of reference group, may explain the conflicting findings.

METHODS

This cohort study compared B19V infections in pregnant day-care employees and healthcare professionals during a B19V epidemic in Finland. Women were identified from the files of nationwide trade unions and the National Supervisory Authority for Welfare and Health. Early-pregnancy maternal B19V IgG was analysed in 3710 women, and infections were defined as seroconversions after analysing in parallel the available umbilical cord blood samples of the 847 seronegative mothers. Independently of the serological status, the actual employment during pregnancy was assessed using registered information on employment history.

RESULTS

B19V infections were more common among day-care employees (22/331, 6.6%), than among those working in healthcare (12/326, 3.7%). The adjusted HRs of B19V infection, using proportional hazard regression, was 2.63 (95% CI 1.27 to 5.46) among all women and 5.59 (95% CI 1.40 to 22.4) among nulliparous women.

CONCLUSIONS

Day-care employees are at an increased risk of B19V infection, which warrants preventive measures.

Increased seroprevalence of IgG-class antibodies against cytomegalovirus, parvovirus B19, and varicella-zoster virus in women working in child day care

Background

Primary maternal infection with cytomegalovirus (CMV), parvovirus B19 (B19V), and varicella-zoster virus (VZV) may result in adverse pregnancy outcomes like congenital infection or foetal loss. Women working in child day care have an increased exposure to CMV, B19V, and VZV. By comparing the seroprevalence of IgG-class antibodies against CMV, VZV and B19V in female day care workers (DCW) with the seroprevalence in women not working in day care this study aimed to assess the association between occupation and infection.

Methods

A cross-sectional design was used. Out of a random sample of 266 day care centres, demographic data, data on work history, and blood samples were collected from 285 women from 38 centres. In addition, blood samples and basic demographics from women who participated in a cross-sectional survey of the Amsterdam population (2004) were used. All blood samples were tested for IgG-class antibodies against CMV, B19V, and VZV.

Results

Twenty-seven percent of the DCW were still susceptible to B19V or CMV. Working in day care was independently associated with B19V infection in all DCW (prevalence ratio [PR] 1.2; 95 % CI 1.1–1.3), and with CMV infection in DCW of European origin only (PR 1.7; 95 % CI 1.3–2.3). Almost all women born outside Europe tested seropositive for CMV (96 %). All DCW tested seropositive for VZV, compared to only 94 % of the women not working in day care.

Conclusion

This study confirms the clear association between employment in child day care centres and infection with CMV and B19V. Intervention policies, like screening of new employees and awareness campaigns emphasizing hygienic measures among DCW, should be implemented urgently to improve the maternal health of these women and the health of their offspring.

Parvovirus b19 infection in fetal deaths

BACKGROUND

Parvovirus B19 infection during pregnancy can lead to nonimmune fetal hydrops, miscarriage, and intrauterine fetal death (IUFD). Some studies have suggested that parvovirus B19 infection may surprisingly often result in nonhydropic fetal death during the third trimester, in the absence of maternal serological evidence of acute infection. This study was conducted to investigate the prevalence of parvovirus B19 DNA among fetuses from miscarriages and IUFDs.

METHODS

We retrospectively studied 535 unborn fetuses, including 120 fetuses from miscarriages and 169 from IUFDs. The control fetuses were 246 fetuses from induced abortions. All fetuses were autopsied from July 1992 through December 1995 and from January 2003 through December 2005 in Helsinki, Finland. The period included a major epidemic of parvovirus B19 infection in 1993. Formalin-fixed, paraffin-embedded fetal tissues were studied with use of a highly sensitive and specific PCR that was capable of detecting all 3 parvovirus B19 genotypes and by histologic examination. In addition, maternal parvovirus B19 serological status was determined.

RESULTS

Parvovirus B19 DNA was detected in 5 fetuses with gestational ages of 14, 22, 23, 30, and 39 weeks; these included fetuses from 4 (2.4%) of the 169 IUFDs and 1 (0.8%) of the 120 miscarriages. During the epidemic year 1993, the prevalence of parvovirus B19 DNA-positive fetal deaths was 6 times the prevalence during nonepidemic years. All 5 mothers of the parvovirus B19 DNA-positive fetuses had serological signs of acute parvovirus B19 infection close to the time of fetal death. The only nonhydropic fetus was full-term.

CONCLUSIONS

Our findings indicate that the prevalence of parvovirus B19 infection among fetuses from IUFDs is low. In particular, our findings did not verify the claimed high prevalence of third-trimester nonhydropic IUFDs associated with parvovirus B19.

Best practice in primary care pathology: review 7

This seventh best-practice review examines four series of common primary care questions in laboratory medicine: (1) blood count abnormalities 2; (2) cardiac troponins; (3) high-density lipoprotein cholesterol; and (4) viral diseases 2. The review is presented in a question-answer format, with authorship attributed for each question series. The recommendations are a précis of guidance found using a standardised literature search of national and international guidance notes, consensus statements, health policy documents and evidence-based medicine reviews, supplemented by Medline Embase searches to identify relevant primary research documents. The recommendations are not standards, but form a guide to be set in the clinical context. Most are consensus based rather than evidence based. They will be updated periodically to take account of new information.

Clinical aspects of parvovirus B19 infection

Parvovirus B19 is a significant human pathogen that causes a wide spectrum of clinical complications ranging from mild, self-limiting erythema infectiosum in immunocompetent children to lethal cytopenias in immunocompromised patients and intrauterine foetal death in primary infected pregnant women. The infection may also be persistent and can mimic or trigger autoimmune inflammatory disorders. Another important clinical aspect to consider is the risk of infection through B19-contaminated blood products. Recent advances in diagnosis and pathogenesis, new insights in the cellular immune response and newly discovered genotypes of human parvoviruses form a platform for the development of modern therapeutic and prophylactic alternatives.

Parvovirus B19 infection in pregnancy

Parvovirus B19 is a small single-stranded DNA virus and a potent inhibitor of erythropoiesis, due to its cytotoxicity to erythroid progenitor cells. Infection with parvovirus B19 during pregnancy can cause several serious complications in the fetus, such as fetal anemia, neurological anomalies, hydrops fetalis, and fetal death. Early diagnosis and treatment of intrauterine parvovirus B19 infection is essential in preventing these fetal complications. Testing maternal serum for IgM antibodies against parvovirus B19 and DNA detection by PCR can confirm maternal infection. If maternal infection has occurred, ultrasound investigation of the fetus and measurement of the peak systolic flow velocity of the middle cerebral artery are sensitive non-invasive procedures to diagnose fetal anemia and hydrops. Intrauterine transfusion is currently the only effective treatment to alleviate fetal anemia, but if the fetus is (near) term, induction of delivery should be considered. Most maternal infections with parvovirus B19 occur through contact with infected children at home. Individual counseling of susceptible pregnant women will reduce unnecessary fetal deaths.

Human parvovirus B19

Parvovirus B19 (B19) was discovered in 1974 and is the only member of the family Parvoviridae known to be pathogenic in humans. Despite the inability to propagate the virus in cell cultures, much has been learned about the pathophysiology of this virus, including the identification of the cellular receptor (P antigen), and the control of the virus by the immune system. B19 is widespread, and manifestations of infection vary with the immunologic and hematologic status of the host. In healthy immunocompetent individuals B19 is the cause of erythema infectiosum and, particularly in adults, acute symmetric polyarthropathy. Due to the tropism of B19 to erythroid progenitor cells, infection in individuals with an underlying hemolytic disorder causes transient aplastic crisis. In the immunocompromised host persistent B19 infection is manifested as pure red cell aplasia and chronic anemia. Likewise, the immature immune response of the fetus may render it susceptible to infection, leading to fetal death in utero, hydrops fetalis, or development of congenital anemia. B19 has also been suggested as the causative agent in a variety of clinical syndromes, but given the common nature, causality is often difficult to infer. Diagnosis is primarily based on detection of specific antibodies by enzyme-linked immunosorbent assay or detection of viral DNA by dot blot hybridization or PCR. Treatment of persistent infection with immunoglobulin reduces the viral load and results in a marked resolution of anemia. Vaccine phase I trials show promising results.

An epidemic of parvovirus B19 in a population of 3,596 pregnant women: a study of sociodemographic and medical risk factors

OBJECTIVES

To estimate the incidence of human parvovirus B19 among pregnant women before and during an epidemic, to elucidate possible sociodemographic and medical risk factors during pregnancy and to estimate the association between parvovirus B19 infection and negative pregnancy outcome.

DESIGN

Prospective study among pregnant women followed from their first antenatal visit before 24 full weeks of gestation until delivery.

SETTING

Department of Obstetrics and Gynaecology, Odense University Hospital, Denmark, November 1992 to February 1994.

METHODS

3,596 pregnant women were invited to participate. The women were examined at first antenatal visit in the period from November 1992 to February 1994 and at delivery. The last delivery was in August 1994 and samples were thus collected before and during a large parvovirus B19 epidemic in Denmark January to September 1994. A blood sample for parvovirus B19 serology was taken at enrollment and from the umbilical cord at delivery. Three questionnaires were completed during 2nd and 3rd trimesters and a registration form at delivery. In total, 3,174 (87.6%) were enrolled and 79.5% completed the study.

RESULTS

The prevalence of B19 IgG seropositivity at the first antenatal visit before 24 full weeks of gestation was 66% . The cumulative prevalence proportion of acute parvovirus B19 infection during pregnancy among IgG negative women was found to be 10.3% (IgM seropositivity and/or IgG seroconversion). The IgG seroconversion incidence increased significantly from 1.0% to 13.5% among 932 seronegative pregnant women before and during the epidemic, respectively (P < 0.001). Independent risk factors related to increased risk of B19 infection during pregnancy, adjusted for other sociodemographic and medical factors, were: children at home (adjusted OR 2.1, 95% CI 1.3-3.2); serious medical disease (adjusted OR 3.0, 95% CI 1.0-8.5); and a stressful job (adjusted OR 1.8, 95% CI 1.0-3.3). Parvovirus B 19 IgM seropositivity was associated with events of late spontaneous abortions and stillbirths (crude OR 9.9; 95% CI 3.3-29.4).

CONCLUSION

Before and during an epidemic of acute B19 infection incidences were measured among pregnant women to be 1.0% and 13.5%, respectively. Three factors, significantly increasing the risk of acute B19, were identified as: having children at home; suffering from serious medical diseases; and having a stressful job. IgM positivity for parvovirus B19 was associated with negative outcome of pregnancy.

Human parvovirus B19 infection in organ transplant recipients

We report a 61-yr-old kidney transplant recipient with human Parvovirus B19 (HPV B19) infection presenting as a severe pancytopenia 1 month after transplantation. Bone marrow aspiration revealed severe erythroid hypoplasia with giant and dystrophic proerythroblasts. Bone marrow cells were positive for HPV B19 DNA detected by polymerase chain reaction (PCR). Pancytopenia resolved shortly after administration of intravenous immunoglobulins. Nineteen cases of HPV B19 infection in organ transplant recipients have been so far reported in the literature. Immunocompromised patients should be considered at risk from developing symptomatic HPV B19 infections. In such patients, specific anti-HPV B19 IgM and IgG antibodies may be absent or transient and therefore their negativity cannot rule out the diagnosis of HPV B19 infestation. Bone marrow smear morphological findings may suggest the diagnosis but testing for viral DNA by PCR is mandatory. Patients may spontaneously recover. However, since specific anti-viral therapy is not currently available, intravenous immunoglobulin administration appears to be the more efficacious treatment.

A clinical and epidemiological study of human parvovirus B19 infection in fetal hydrops using PCR Southern blot hybridization and chemiluminescence detection

Ninety-eight samples from 80 cases of spontaneous abortions after fetal death or hydrops fetalis from 12,000 pregnant women were examined using PCR. DNA was extracted from amniotic fluid, fetal blood, ascitic fluid and fetal biopsies or placenta specimens using QIA amp kits (QIAGEN). A 270-bp length fragment located within the B19 gene NS1 was amplified using PCR followed by electrophoresis and southern-blot hybridization assay using a horseradish peroxidase-labelled probe and chemiluminescence detection. This assay was able to detect 1 to 10 DNA copies in a 10 microliters sample. Parvovirus B19 was identified in 11 cases (14% of fetal hydrops; 1 case for 1,100 pregnancies). Amniotic fluid was the most common and reliable sample to assess the diagnosis. Gestational age ranged from 17 to 28 weeks (mean 23 weeks). IgM antibodies were detected in 3 maternal sera, 2 patients of which reported an exposure to B19 infection during pregnancy. In 2 cases, intrauterine blood transfusions led to the cessation of symptoms and to birth of normal babies.

Exposure Workups

Exposure workups are an important responsibility for infection control personnel. A well-designed plan for investigating exposures, which includes appropriate algorithms, will enable infection control personnel to evaluate exposures rapidly and consistently so that nosocomial transmission is minimized. Infection control personnel should use their own data to develop policies and procedures that suit the needs of their facility. After they have imple-merited the plan, infection control personnel should continue to collect data on exposures so they can continuously improve their performance.

Parvovirus B19 infection

Human parvovirus B19, discovered in 1974, is a single-stranded DNA virus which causes erythema infectiosum, arthralgia, aplastic crisis in patients with red cell defects, chronic anaemia in immunocompromised patients, and fetal hydrops. Seroprevalence in developed countries is 2-10% in children less than 5 years, 40-60% in adults more than 20 years, and 85% or more in those over 70 years. The virus may be transmitted by the respiratory route and by transfusion of infected blood and blood products. After an incubation period of six to eight days, viraemia occurs, during which reticulocyte numbers fall dramatically resulting in a temporary drop in haemoglobin of 1 g/dl in a normal person. Clearance of viraemia is dependent on development of specific antibody to the B19 structural proteins, VP1 and VP2. The red cell receptor for the virus is blood group P antigen. Diagnosis in immunocompetent persons depends on detection of specific IgM in serum. Diagnosis in immunocompromised persons depends on detection of B19 antigen or DNA in serum. There is no specific treatment for B19 infection; however, human normal immunoglobulin may be used as a source of specific antibody in chronically infected persons. A recombinant parvovirus B19 vaccine is under development.

Infectious causes of hydrops fetalis

A variety of infectious agents have been associated with nonimmune hydrops fetalis, most notably parvovirus B19, cytomegalovirus, herpes simplex virus, Toxoplasma gondii, and Treponema pallidum. These agents produce hydrops through effects on fetal bone marrow, myocardium, or vascular endothelium. Knowledge of the epidemiology and clinical characteristics of maternal and fetal infection can be used to select a diagnostic approach. Etiologic diagnosis will guide prognosis and the selection of specific chemotherapy.

Parvovirus: the expanding spectrum of disease

Treatment of parvovirus infections among immunocompromised hosts using immunoglobulin has provided the clinician with a useful therapeutic tool but has also highlighted the problems concerning chronic disease states. The discovery of the human parvovirus B19 in 1975 and subsequent studies of its effects in humans have identified this virus as the causative agent of a broad spectrum of diseases. Recent improvements regarding the development of sensitive PCR techniques and methods for cultivation have provided new insight into its pathogenic role, its virology and immunology, and the varied clinical manifestations. The current state of knowledge concerning parvovirus enabled us to divide the long list of diseases caused by this virus into three main categories: (1) disease found among normal hosts (asymptomatic disease, erythema infectiosum, arthropathy, hydrops fetalis), (2) hematologic diseases (aplastic crisis, chronic anemia, idiopathic thrombocytopenic purpura, transient erythroblastopenia of childhood, Diamond-Blackfan anemia) and, finally, (3) a heterogeneous group of diseases, in which the etiologic role of parvovirus is less clear and sometimes putative (neurologic disease, rheumatologic disease, vasculitic and myocarditic syndromes). In particular, arthropathy, hydrops fetalis and the hematologic disorders may be of pediatric concern. Consequently, it is of paramount importance that in all of these cases the clinician includes parvovirus as a differential diagnosis.

Health considerations for pregnant child care staff

Child care is a profession comprised predominantly of young women of child-bearing age. Yet the pregnancy of child care staff has been discussed only incidentally in the health literature on early childhood. Because nursing professionals serve in a number of roles in child care centers, this is an important topic to include for health in-services and consultations. This article reviews what is currently known and recommended for pregnant child care staff regarding illnesses, stress, and the ergonomics of the job. The occupational health research that included women employed in child care is examined. Guidelines and recommendations for staying healthy and managing classroom activities during pregnancy are suggested.

Long-term outcome in fetal hydrops from parvovirus B19 infection

Parvovirus B19 infection in the fetus is associated with anemia and hydrops and can result in fetal death. Fetal transfusion has been used in an attempt to improve outcome; however, it is associated with its own perinatal morbidity. We report two cases of fetal parvovirus B19 infection that were confirmed by polymerase chain reaction for parvovirus B19 deoxyribonucleic acid in umbilical cord blood. Ultrasonographic signs of compromise were observed at 30 and 24 weeks of gestation. Both fetuses were hydropic and one fetus was also anemic. Serial sonograms demonstrated that the hydrops resolved spontaneously over 3 to 5 weeks after diagnosis. One infant was delivered at 32 weeks of gestation as a result of idiopathic preterm labor. The other infant was delivered at term. Both infants appeared relatively normal at birth and have developed normally in the first year of life. Thus fetal hydrops in association with parvovirus B19 infection does not always lead to poor long-term outcome. A conservative approach without in utero therapy may be appropriate for the management of some of these fetuses.