Toxoplasmosis and parvovirus B19

Intrauterine transfusion in 103 fetuses with severe anemia caused by parvovirus infection. A multicenter retrospective study

PURPOSE

Evaluating procedure-related complications and perinatal outcomes after intrauterine transfusion (IUT) before or after 20⁺⁰ weeks of gestation in fetuses with severe anemia due to intrauterine human parvovirus B19 infection.

METHODS

A retrospective study investigating fetuses requiring IUT for fetal Parvo B19 infection in two tertiary referral centers between December 2002 and December 2021. Procedure-related complications, intrauterine fetal death (IUFD), and perinatal outcome were correlated to gestational age (GA) at first IUT, the presence of hydrops and fetal blood sampling results.

RESULTS

A total of 186 IUTs were performed in 103 fetuses. The median GA at first IUT was 19⁺³ (13⁺⁰-31⁺⁴) weeks of gestation. IUFD occurred in 16/103 fetuses (15.5%). Overall survival was 84.5% (87/103). Hydrops (p = 0.001), lower mean hemoglobin at first IUT (p = 0.001) and low platelets (p = 0.002) were strongly associated with IUFD. There was no difference observed in fetuses transfused before or after 20⁺⁰ weeks of gestation.

CONCLUSION

IUT is a successful treatment option in fetuses affected by severe anemia due to parvovirus B19 infection in specialized centers. In experienced hands, IUT before 20 weeks is not related to worse perinatal outcome.

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 in human pregnancy

Human parvovirus B19 infection is widespread. Approximately 30-50% of pregnant women are nonimmune, and vertical transmission is common following maternal infection in pregnancy. Fetal infection may be associated with a normal outcome, but fetal death may also occur without ultrasound evidence of infectious sequelae. B19 infection should be considered in any case of nonimmune hydrops. Diagnosis is mainly through serology and polymerase chain reaction. Surveillance requires sequential ultrasound and Doppler screening for signs of fetal anaemia, heart failure and hydrops. Immunoglobulins, antiviral and vaccination are not yet available, but intrauterine transfusion in selected cases can be life saving.

Unexpected intrauterine fetal death in parvovirus B19 fetal infection

Parvovirus B19 infection during pregnancy can be transmitted to the fetus through the placenta. The consequences for the health of the fetus are very variable and can be very serious. They include intrauterine fetal death (IUFD) and miscarriage, which can lead to medico-forensic questions. For the most part, cases of IUFD take place during the second trimester of gestation and present an anatomopathologic picture characteristic of fetal infection with hydrops, placental edema, serous effusion, and erythroblastosis with nuclear inclusions. Endocardial fibroelastosis, medullar and thymic hypoplasia, and hepatic hemosiderosis are frequently present. In the third trimester, the cases are less frequent, not accompanied by hydrops, and can depend more on placental compromise than on direct infection of the fetus. We present 5 cases of IUFD resulting from parvovirus B19 and we discuss the pathogenetic and anatomopathologic aspects and obstetric liability. In 4 cases, the IUFD took place suddenly, in the absence of symptoms, in women who had not previously shown any symptom of the viral infection. In one case, the patient was hospitalized following an ultrasound diagnosis of fetal hydrops and IUFD took place 5 days after admission. Of these cases 3 were verified in the second trimester and 2 in the third trimester. Only the cases of the second trimester and one of the 2 cases of the third trimester presented the characteristic aspects of fetal infection. The other case of third trimester was characterized by placental involvement.

Advances in the biology, diagnosis and host-pathogen interactions of parvovirus B19

Increased recognition of parvovirus B19 (B19), an erythrovirus, as a significant human pathogen that causes fetal loss and severe disease in immunocompromised patients has resulted in intensive efforts to understand the pathogenesis of B19-related disease, to improve diagnostic strategy that is deployed to detect B19 infection and blood-product contamination and, finally, to elucidate the nature of the cellular immune response that is elicited by the virus in diverse patient cohorts. It is becoming clear that at least three related erythrovirus strains (B19, A6/K71 and V9) are circulating in the general population and that viral entry into target cells is mediated by an expanding range of cellular receptors, including P antigen and beta-integrins. Persistent infection by B19 is emerging as a contributory factor in autoimmune disease, a hypothesis that is constrained by the detection of B19 in the skin of apparently healthy individuals. B19 infection during pregnancy may account for thousands of incidences of fetal loss per annum in Europe, North America and beyond, yet there is currently only minimal screening of pregnant women to assess serological status, and thereby risk of infection, upon becoming pregnant. Whilst major advances in diagnosis of B19 infection have taken place, including standardization of serological and DNA-based detection methodologies, blood donations that are targeted at high-risk groups are only beginning to be screened for B19 IgG and DNA as a means of minimizing exposure of at-risk patients to the virus. It is now firmly established that a Th1-mediated cellular immune response is mounted in immunocompetent individuals, a finding that should contribute to the development of an effective vaccine to prevent B19 infection in selected high-risk groups, including sickle-cell anaemics.

Detection of human parvovirus B19 infection: a study of 212 suspected cases in the state of Rio de Janeiro, Brazil

BACKGROUND

Parvovirus B19 infections are associated with different clinical manifestations that vary from symptom-less to severe. The main clinical manifestations are erythema infectiosum or fifth disease, transient aplastic crisis in individuals with hemoglobinopathies, chronic anemia in the immunocompromised, acute polyarthralgia syndrome in adults, hydrops fetalis, spontaneous abortion and stillbirth. Although the classical features of B19 and rubella infections are distinct, uncommon presentations can lead to misdiagnosis.

OBJECTIVE

The goal of this study was to assess the occurrence of parvovirus B19 (B19) infection in patients with clinical signs of toxoplasmosis or rubella, both of which were not confirmed by laboratorial techniques.

STUDY DESIGN

Serum samples from 214 patients were collected between January 1996 and December 1997 in the state of Rio de Janeiro, Brazil, B19 specific IgG and IgM were detected by using commercial enzyme-linked immunosorbent assays (ELISA), and viral nucleic acid was detected employing a nested polymerase chain reaction (PCR) protocol.

RESULTS

Combining the results obtained by IgM ELISA and PCR, 14.5% of the samples were positive in one or both tests, with a concordance of 92.5% between the two techniques.

CONCLUSIONS

Specimens collected in 16 out of 22 municipalities were positive in at least one out of the three tests employed, indicating that parvovirus B19 circulates in several regions of the state of Rio de Janeiro.

Toxoplasmosis

Toxoplasmosis is caused by the protozoan organism, Toxoplasma gondii. Infection with this organism primarily results from contact with infected cats and from ingestion of improperly cooked meat. Most adults with toxoplasmosis are asymptomatic. When symptoms are present, they typically resemble a mononucleosis or flulike illness. The diagnosis of toxoplasmosis in the pregnant adult is best made using serological techniques to detect IgM antibody and to document significant changes in the IgG antibody titer. Congenital toxoplasmosis usually occurs as a result of primary maternal infection. The most useful tests for confirmation of fetal infection are ultrasound examination, cordocentesis for detection of IgM-specific antibody, and amniocentesis for detection of toxoplasma DNA in amniotic fluid. Congenital toxoplasmosis can be treated with reasonable success by administration of antibiotics (spiramycin, sulfadiazine, and pyrimethamine) to the mother. In an effort to prevent acquisition of infection, pregnant women should be counseled to avoid contact with cat litter and improperly cooked beef, pork, or lamb.

Polymerase chain reaction in the detection of microbes in amniotic fluid

Intra-amniotic infection during pregnancy can be caused by bacteria, viruses or protozoa, Toxoplasma gondii for example. Bacterial intrauterine infections are connected with premature birth, premature rupture of fetal membranes, and infective complications of both the mother and the newborn. Viral infections and Toxoplasma gondii can cause fetal malformations and illness with serious sequelae to the infant or fetal death in utero. Determining the causative agent is important and often greatly affects the prognosis of the newborn. Amniotic fluid is in most cases easily and safely obtainable during the second and third trimester and can be used in several microbiological assays. These include bacterial and viral cultures, Gram staining, quantitative assays for immunoglobulins or cytokines, and polymerase chain reaction (PCR) for detecting microbial DNA. This review concentrates on broad-spectrum or universal bacterial PCR for detection of bacterial DNA in amniotic fluid and on PCR assays for certain clinically important viruses and for Toxoplasma gondii.