A Spotlight on Effective Parental Care: TORCH Serology
Published by
Olga Siemiatkowska
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TORCH is an acronym representing a group of infectious agents that typically cause mild and treatable diseases in healthy individuals, however, if acquired during pregnancy, they pose a risk of severe birth defects and fetal death. Recognizing maternal infections and closely monitoring diagnosed patients is crucial for the health of the baby. The risk of contracting a TORCH pathogen during pregnancy is influenced by geographic location, preventive measures, and the mother's immune status specific to each virus. Serological testing allows the determination of the mother's immune status guiding risk assessment and preventive measures, with ongoing monitoring in prenatal care (Warnecke et al., 2020).
Status of TORCH testing
The acronym TORCH stands for Toxoplasma gondii, other agents (i.e., syphilis, Listeria, parvovirus B19 or HIV), Rubella virus, Cytomegalovirus (CMV), and Herpes virus, but the final composition of recommended screenings depends on the clinical details provided. For example, Gloucestershire Hospitals NHS Foundation Trust conducts 'TORCH' screens in cases of intrauterine growth retardation, intrauterine death, and suspected congenital infection. The test involves analyzing the mother's blood for IgM and IgG antibodies against Rubella, Toxoplasma gondii, CMV, and parvovirus. These tests help identify potential causes of complications such as intrauterine growth restriction (IUGR) or intrauterine death, guiding clinicians in providing appropriate medical interventions when needed.
However, the full TORCH screen is not performed routinely in all healthy pregnancies. Instead, healthcare professionals in the UK offer HIV, hepatitis, and syphilis screening to all pregnant women as a part of the infectious diseases in pregnancy screening (IDPS) programme (Public Health England, 2015).
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The rationale for routine testing of the full TORCH panel in every pregnancy diminished in countries as the UK or Australia due to increased hygiene, education, and successful prevention strategies, although 0.2-2.2% of all live births are still affected by CMV congenital infection (Kenneson & Cannon, 2007).
The prevalence of parvovirus infections in pregnancy is at 1-2% in five European countries, with only a little more than half of tested women showing pre-existing immunity (MOSSONG et al., 2007).
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Impact of Vaccination Hesitancy
As a result of the decline in MMR vaccine uptake cases of measles have increased by 43% globally in 2022, resulting in 136 000 deaths – mostly among children (WHO, 2023).
Measles is the most transmissible pathogen which the MMR vaccine protects against. It requires at least 95% vaccine coverage for herd immunity, while the less contagious Rubella virus requires coverage to be maintained at least at 80% (WHO, 2020 As the MMR vaccine coverage dropped to 84.5% average in England and 74% for the prime-boost in London, the spread of Rubella infection is again a real possibility (NHS, 2023a).
Ensuring robust coverage of rubella-containing vaccines is crucial. Insufficient vaccination rates among infants and young children may reduce but not eliminate rubella virus circulation, heightening the vulnerability of women of reproductive age. This increased susceptibility poses a potential risk, leading to higher rates of congenital rubella syndrome (CRS) compared to the pre-vaccine era (WHO, 2020).
Fortunately, there have been no new laboratory-confirmed cases of rubella reported in the UK since 2019. However, before the introduction of the rubella vaccine, the recorded incidence of congenital rubella syndrome (CRS) was 0.1–0.2 cases per 1000 live births during endemic periods, escalating to 0.8–4 cases per 1000 live births during rubella epidemics (GOV.UK, 2024).
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Toxoplasma infections
Toxoplasma gondii (T. gondii) is the etiological agent of toxoplasmosis. In the United States, an estimated 1.1 million individuals contract T. gondii annually, leading to 789 deaths attributed to toxoplasmosis from 2000 to 2010 (Cummings et al., 2014).
The most common causes of acquiring the infection in the US are thought to be handling meat, consuming raw or undercooked meat, contact with cat feces, and ingestion of unfiltered water or unpasteurized goat milk (Deganich et al., 2022).
Toxoplasma's broad host range, coupled with numerous risk factors positions it as a global health threat, infecting approximately one-third of the world's population. Consequently, congenital toxoplasmosis continues to exert a significant toll on health, contributing to morbidity and mortality worldwide, particularly in developing nations. A study assessing congenital toxoplasmosis incidence projected around 190,000 cases annually, equating to approximately 1.5 cases per 1000 live births (Torgerson & Mastroiacovo, 2013).
Despite more than half of infected women being asymptomatic primary infection with T. gondii during pregnancy may result in congenital infection of the foetus (Boyer et al., 2011). Toxoplasmosis in pregnancy is treatable with antibiotics preventing congenital complications and even miscarriage caused by the disease (NHS, Toxoplasmosis 2023b), hence the immunodiagnostic in asymptomatic pregnant women can be immensely beneficial for the baby.
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Herpes Simplex Virus Infection in Pregnancy
In recent times, the prevalence of genital herpes has risen as a more widespread sexually transmitted infection. Since the late 1970s, there has been a 30% increase in herpes simplex virus 2 (HSV-2) seroprevalence, leading to one in five adults being infected. The likelihood of infection seems connected to the number of sexual partners, with women experiencing it more frequently than men (Smith & Robinson, 2002, Weiss, 2004).
In the United States, about 22% of pregnant women are infected with HSV-2, and 2% contract genital herpes while pregnant, exposing their newborns to the risk of herpes infection (Brown et al., 1997).
Primary infection with HSV-2 during pregnancy has been linked to various complications such as neonatal herpes infections, especially if the infection is acquired in the third trimester as there may not be enough time to develop antibodies needed to suppress viral replication before labour (Straface et al., 2012). The infection can be cleared with a course of antivirals if detected after week 28 of pregnancy, therefore routine testing could prevent the potential complications at birth (NHS, Genital herpes 2023c).
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Conclusion
Antenatal immunodiagnostics continue to play a pivotal role in preventing complications and promoting optimal quality of life for both the mother and the baby. Despite an ever-expanding landscape of diagnostics, extended TORCH panel testing remains a valuable diagnostic tool for screening populations at risk. The global rise in vaccination hesitancy has contributed to a resurgence of congenital infections. Consequently, there is a growing rationale for reintroducing asymptomatic antenatal screening for TORCH pathogens alongside HIV, hepatitis, and syphilis in the Western world.
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References
Boyer, K. et al. (2011) ‘Unrecognized ingestion of Toxoplasma gondii oocysts leads to congenital toxoplasmosis and causes epidemics in North America’, Clinical Infectious Diseases, 53(11), pp. 1081–1089. doi:10.1093/cid/cir667.
Brown, Z.A. et al. (1997) ‘The acquisition of Herpes Simplex Virus during pregnancy’, New England Journal of Medicine, 337(8), pp. 509–516. doi:10.1056/nejm199708213370801.
Cummings, P.L. et al. (2014) ‘Trends, productivity losses, and associated medical conditions among toxoplasmosis deaths in the United States, 2000–2010’, The American Journal of Tropical Medicine and Hygiene, 91(5), pp. 959–964. doi:10.4269/ajtmh.14-0287.
Deganich, M., Boudreaux, C. and Benmerzouga, I. (2022) ‘Toxoplasmosis infection during pregnancy’, Tropical Medicine and Infectious Disease, 8(1), p. 3. doi:10.3390/tropicalmed8010003.
GOV.UK (2024) Laboratory confirmed cases of measles, rubella and mumps in England: April to June 2023. Available at: https://www.gov.uk/government/publications/measles-mumps-and-rubella-lab-confirmed-cases-in-england-2023/laboratory-confirmed-cases-of-measles-rubella-and-mumps-in-england-april-to-june-2023 (Accessed: 12 March 2024).
Kenneson, A. and Cannon, M.J. (2007) ‘Review and meta‐analysis of the epidemiology of congenital cytomegalovirus (CMV) infection’, Reviews in Medical Virology, 17(4), pp. 253–276. doi:10.1002/rmv.535.
MOSSONG, J. et al. (2007) ‘Parvovirus B19 infection in five European countries: Seroepidemiology, force of infection and maternal risk of infection’, Epidemiology and Infection, 136(8), pp. 1059–1068. doi:10.1017/s0950268807009661.
NHS (2023a) Childhood Vaccination Coverage Statistics, England, 2022-23. Available at: https://digital.nhs.uk/data-and-information/publications/statistical/nhs-immunisation-statistics/england-2022-23/6in-1-vaccine#mmr2-vaccine-second-dose- (Accessed: 12 March 2024).
NHS (2023b) Toxoplasmosis, NHS choices. Available at: https://www.nhs.uk/conditions/toxoplasmosis/ (Accessed: 12 March 2024).
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Public Health England (2015) Infectious diseases in pregnancy screening (idps): Programme overview, Infectious diseases in pregnancy screening (IDPS): programme overview. Available at: https://www.gov.uk/guidance/infectious-diseases-in-pregnancy-screening-programme-overview#Evidence%20Base (Accessed: 12 March 2024).
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Torgerson, P.R. and Mastroiacovo, P. (2013) ‘The global burden of congenital toxoplasmosis: A systematic review’, Bulletin of the World Health Organization, 91(7), pp. 501–508. doi:10.2471/blt.12.111732.
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WHO (2020) Summary of the WHO position on rubella vaccine- July 2020, Summary of Key Points Rubella vaccines: WHO position paper – July 2020. Available at: https://www.who.int/docs/default-source/immunization/position_paper_documents/rubella/summary-of-the-who-position-on-rubella-vaccine-2020.pdf?ua=1 (Accessed: 12 March 2024).