TORCH Infections

The acronym TORCH refers to a group of pathogens that can cause congenital or perinatal infections leading to significant fetal and neonatal morbidity and mortality. The components are:

• Toxoplasmosis
• Others (Syphilis, Varicella-Zoster, Parvovirus B19, Zika virus, HIV, Hepatitis B, Listeria, Lymphocytic Choriomeningitis Virus, etc.)
• Rubella
• Cytomegalovirus (CMV)
• Herpes Simplex Virus (HSV)

General Principles:

• Maternal Symptoms: Infections are often mild or asymptomatic in the pregnant woman but can be disastrous for the fetus.
• Timing: Fetal outcomes depend heavily on the gestational age at infection. Generally, infection in the first trimester leads to severe teratogenicity or fetal loss, while infection later in pregnancy has a higher transmission rate but often less severe structural sequelae (though sequelae like deafness may still occur).
• Transmission:
  • Primary Infection: Highest risk of transmission and severe fetal damage usually occurs with primary maternal infection during pregnancy.
  • Reactivation/Reinfection: Fetal affection is infrequent with latent infection or reactivation (exception: CMV, where reactivation/reinfection contributes significantly to the burden, and Syphilis).
• Clinical Overlap: Manifestations in the neonate are often indistinguishable and include intrauterine growth restriction (IUGR), hepatosplenomegaly, jaundice, thrombocytopenia (blueberry muffin rash), and microcephaly.

1. Toxoplasmosis

Etiology and Transmission

• Agent: Toxoplasma gondii, an obligate intracellular protozoan.
• Hosts: Cats are the definitive hosts (shedding oocysts). Humans are intermediate hosts.
• Routes:
  • Ingestion of tissue cysts in undercooked meat (pork, lamb, venison).
  • Ingestion of oocysts from contaminated soil, water, or cat litter.
  • Transplacental transmission (vertical).
• Transmission Risk: The risk of fetal infection increases with gestational age (lowest in 1st trimester, highest in 3rd), but the severity of fetal disease decreases with advancing gestation.
  • Maternal primary infection is the main cause of fetal infection. Reactivation rarely affects the fetus unless the mother is immunocompromised (e.g., HIV).

Clinical Manifestations

• Classic Triad:
  1. Chorioretinitis: Bilateral, involves macula, vision-threatening. Can be active or quiescent (scars).
  2. Hydrocephalus: Due to obstruction of the aqueduct of Sylvius or foramen of Monro; may lead to macrocephaly.
  3. Intracranial Calcifications: Diffuse, scattered throughout the brain parenchyma (caudate nucleus, basal ganglia, cortex). Distinguishes from periventricular calcifications of CMV.
• Other Signs: Microcephaly, convulsions, mental retardation, hepatosplenomegaly, jaundice, thrombocytopenia, anemia, lymphadenopathy.
• Late Sequelae: Infants asymptomatic at birth may develop chorioretinitis, deafness, or developmental delay later in life (up to adulthood).

Diagnosis

• Maternal Screening:
  • IgG and IgM: IgM positivity suggests recent infection but has high false-positive rates.
  • IgG Avidity: Low avidity suggests infection within the last 12 weeks (useful in 1st trimester). High avidity rules out infection in the last 4 months.
  • Seroconversion: A rise in titer or seroconversion is diagnostic.
• Fetal Diagnosis: PCR for T. gondii in amniotic fluid (performed >18 weeks gestation).
• Neonatal Diagnosis:
  • Serology: Positive IgM or IgA in infant serum (IgM capture ELISA/ISAGA). IgA is more sensitive than IgM.
  • IgG: Persistence of IgG beyond 12 months of age confirms congenital infection (maternal IgG disappears by then).
  • PCR: Testing of CSF, urine, or peripheral blood.
  • Western Blot: Comparative immunoblot of mother and infant sera.

Management

• Pregnant Women:
  • Acute Infection (<18 weeks): Spiramycin is the drug of choice. It concentrates in the placenta and reduces transmission by ~60% but does not cross the placenta well to treat the fetus.
  • Confirmed Fetal Infection (Positive Amniotic PCR or >18 weeks): Switch to Pyrimethamine + Sulfadiazine + Folinic Acid.
• Neonate:
  • Treat All: All infected infants (symptomatic or asymptomatic) must be treated to prevent late sequelae.
  • Regimen: Pyrimethamine (loading dose followed by daily or intermittent dosing) + Sulfadiazine + Leucovorin (Folinic acid) for 12 months.
  • Adjuncts: Corticosteroids (Prednisone) if active chorioretinitis threatens vision or CSF protein >1000 mg/dL.

2. Rubella

Epidemiology and Transmission

• Agent: Rubella virus (Togaviridae, RNA virus).
• Transmission: Respiratory droplets. Transplacental transmission rate is highest (>90%) in the first 11 weeks of gestation.
• Fetal Risk: The fetus is severely affected if infection occurs in the first trimester. Infection after 16–20 weeks rarely causes defects.

Congenital Rubella Syndrome (CRS)

• Classic Triad (Gregg’s Triad):
  1. Cataracts: Nuclear cataracts, microphthalmia.
  2. Sensorineural Hearing Loss (Deafness): Most common permanent sequela.
  3. Congenital Heart Disease: Patent Ductus Arteriosus (PDA) and Pulmonary Artery Stenosis.
• Extended Syndrome:
  • “Blueberry muffin” rash (dermal erythropoiesis).
  • Microcephaly, meningoencephalitis.
  • Hepatosplenomegaly, radiolucent bone disease.
• Late-Onset Disease: Diabetes mellitus (Type 1), thyroid dysfunction, progressive panencephalitis.

Diagnosis

• Maternal: IgM antibodies or 4-fold rise in IgG.
• Fetal: PCR on amniotic fluid or chorionic villi.
• Neonatal:
  • IgM: Detection of Rubella IgM in cord blood or neonatal serum.
  • Viral Isolation/PCR: Throat swabs, urine, CSF (virus shedding can continue for up to 1 year).
  • Persistence of IgG: High titers beyond 6 months.

Management and Prevention

• Treatment: No specific antiviral therapy exists. Management is supportive (cataract surgery, hearing aids, cardiac repair).
• Prevention:
  • Vaccination: MMR vaccine. Live vaccine is contraindicated during pregnancy. Women should be vaccinated pre-conception and avoid pregnancy for 4 weeks (though accidental vaccination is not an indication for termination).
  • Isolation: Infants with CRS shed virus for months and are contagious; strict isolation is required.

3. Cytomegalovirus (CMV)

Epidemiology

• Burden: Most common cause of congenital infection in developed countries and a leading infectious cause of sensorineural hearing loss (SNHL) and mental retardation.
• Transmission Types:
  • Primary Maternal Infection: 30–40% transmission rate; high risk of severe sequelae (10–15% symptomatic).
  • Recurrent Infection (Reactivation/Reinfection): Lower transmission rate (~1%) but contributes to the majority of congenital infections globally due to high maternal seroprevalence (e.g., 99% in India).

Clinical Manifestations

• Symptomatic (10%): Cytomegalic Inclusion Disease (CID).
  • CNS: Periventricular calcifications (distinct from Toxo), microcephaly, chorioretinitis, sensorineural hearing loss.
  • Systemic: IUGR, hepatosplenomegaly, jaundice, petechiae/purpura (“blueberry muffin” spots), thrombocytopenia.
• Asymptomatic (90%): Appear normal at birth but 10–15% will develop late sequelae, particularly sensorineural hearing loss.

Diagnosis

• Gold Standard: Demonstration of CMV in urine or saliva by culture or PCR within the first 2–3 weeks of life.
• Sensitivity Note: IgM sensitivity is low; a negative IgM does not rule out congenital CMV. Testing after 3 weeks cannot distinguish congenital from postnatal infection (breast milk/blood).
• Imaging: Cranial Ultrasound/CT showing periventricular calcifications.

Management

• Antiviral Therapy: Recommended for neonates with symptomatic congenital CMV involving the CNS or severe organ disease.
  • Drug: Valganciclovir (oral) or Ganciclovir (IV).
  • Duration: 6 months.
  • Benefit: Prevents deterioration of hearing and may improve developmental outcomes.
• Monitoring: Monitor absolute neutrophil count (risk of neutropenia).

4. Herpes Simplex Virus (HSV)

Transmission

• Intrapartum (85%): Passage through an infected birth canal. Risk is highest (30–50%) if the mother has a primary genital infection near delivery, compared to recurrent infection (<1-3% risk) due to transfer of maternal antibodies.
• Postnatal: Contact with non-genital lesions (e.g., cold sores) or nosocomial.
• Intrauterine (5%): Rare; causes skin scars, microcephaly, and chorioretinitis at birth.

Clinical Patterns (Neonatal HSV)

Symptoms typically appear between 5 and 19 days of life.

1. Skin, Eye, and Mouth (SEM) Disease: Vesicular rash, keratoconjunctivitis, oral ulcers. Good prognosis if treated, but can progress to disseminated disease.
2. CNS Disease: Encephalitis with or without skin lesions. Seizures, lethargy, irritability. CSF shows pleocytosis and proteinosis. High morbidity.
3. Disseminated Disease: Sepsis-like illness involving multiple organs (liver, lungs, adrenals, brain). Hepatitis, pneumonitis, DIC, shock. High mortality.

Diagnosis

• PCR: HSV DNA PCR of CSF, blood, and surface swabs (mouth, nasopharynx, conjunctiva, anus) is the test of choice.
• Culture: Viral culture from vesicles or surface swabs.
• Tzanck Smear: Shows multinucleated giant cells (low sensitivity).

Management

• Drug of Choice: High-dose IV Acyclovir (60 mg/kg/day divided q8h).
• Duration:
  • SEM disease: 14 days.
  • CNS/Disseminated disease: 21 days.
• Suppressive Therapy: Oral Acyclovir for 6 months following acute treatment improves neurodevelopmental outcomes and prevents skin recurrences.

5. Syphilis (Treponema pallidum)

Etiology and Epidemiology

• Transmission: Transplacental spirochete transmission can occur at any stage of pregnancy. Risk is nearly 100% in primary/secondary maternal syphilis.
• Outcome: Stillbirth, hydrops fetalis, prematurity, or congenital disease.

Clinical Manifestations

• Early Congenital Syphilis (<2 years):
  • Rhinitis (“Snuffles”): Copious, persistent, highly infectious nasal discharge.
  • Rash: Maculopapular, bullous, or desquamating rash involving palms and soles (pemphigus syphiliticus).
  • Bone Lesions: Osteochondritis, periostitis (Wimberger sign - destruction of proximal medial tibial metaphysis).
  • Visceral: Hepatosphlenomegaly, lymphadenopathy, jaundice, pseudoparalysis of Parrot (due to painful osteochondritis).
• Late Congenital Syphilis (>2 years): Stigmata of chronic inflammation.
  • Hutchinson’s Triad: Hutchinson teeth (notched incisors), Interstitial Keratitis, VIII nerve deafness.
  • Skeletal: Saber shins (anterior bowing of tibia), Clutton’s joints (painless knee effusion), frontal bossing, saddle nose.
  • Cutaneous: Rhagades (fissures at mouth angles).

Diagnosis

• Maternal Screening: VDRL/RPR (non-treponemal). Confirmed by TPHA/FTA-ABS (treponemal).
• Neonatal:
  • Quantitative VDRL: Titer 4-fold higher than maternal titer indicates infection.
  • IgM: IgM ELISA or immunoblot.
  • Darkfield Microscopy: Direct visualization of spirochetes from nasal discharge or skin lesions.
  • CSF Analysis: VDRL, cell count, protein to rule out neurosyphilis.
  • Long Bone X-rays: Osteochondritis/Periostitis.

Management

• Proven/Highly Probable Disease: Aqueous Crystalline Penicillin G IV (100,000–150,000 units/kg/day) for 10 days.
• Prevention: Screening of all pregnant women and treatment with Benzathine Penicillin G.

6. Parvovirus B19

• Clinical Features: The virus infects erythroid progenitor cells. Transplacental infection leads to severe fetal anemia, high output cardiac failure, non-immune hydrops fetalis, and fetal death. It does not typically cause congenital malformations.
• Diagnosis: Maternal serology (IgM/IgG), Fetal MCA Doppler (to detect anemia), PCR of amniotic fluid or fetal blood.
• Management: Intrauterine blood transfusion for severe fetal anemia/hydrops.

7. Zika Virus

• Vector: Aedes mosquito. Sexual transmission also possible.
• Congenital Zika Syndrome:
  • Severe Microcephaly: Partially collapsed skull, redundant scalp skin.
  • Brain Anomalies: Thin cerebral cortices, subcortical calcifications, ventriculomegaly.
  • Ocular: Macular scarring, focal pigmentary retinal mottling.
  • Neurologic: Congenital contractures (arthrogryposis), hypertonia.
• Diagnosis: RT-PCR (serum/urine) in symptomatic infants; IgM ELISA.
• Management: Supportive.

8. Varicella Zoster Virus (VZV)

• Congenital Varicella Syndrome: Occurs if mother acquires infection between 8 and 20 weeks of gestation.
  • Features: Cicatricial skin scarring (zigzag pattern), limb hypoplasia, microcephaly, cataracts, chorioretinitis.
• Neonatal Varicella: Occurs if maternal rash appears 5 days before to 2 days after delivery. Severe disseminated infection with high mortality.
  • Prophylaxis: Varicella Zoster Immunoglobulin (VZIG) to neonate.

9. Diagnostic Approach to “TORCH”

• The “TORCH Screen”: Indiscriminate screening of neonates with IUGR or small for gestational age (SGA) using a battery of serological tests (TORCH IgM/IgG) has low yield and is not cost-effective.
• Targeted Approach: Investigations should be guided by specific clinical findings:
  • Cataracts/CHD: Suspect Rubella.
  • Calcifications: Periventricular (CMV) vs Diffuse (Toxo).
  • Snuffles/Bone lesions: Suspect Syphilis.
  • Vesicles: Suspect HSV.
• Preferred Tests:
  • CMV: Urine/Saliva PCR.
  • Syphilis: Maternal + Infant RPR/VDRL.
  • Toxo: Maternal serology + Infant IgM/IgA + Placental/AF PCR.
  • Rubella: Infant IgM + Viral isolate.
  • HSV: Surface swabs + Blood/CSF PCR.