Torch Test Toxoplasmosis Rubella Cytomegalovirus Herpes Simplex Virus in details

What is TORCH?
Andres Nahmias in 1971, coined the term "TORCH," categorizing a group of perinatal infections found to manifest similar clinical symptoms. TORCH infections initially comprised of Toxoplasmosis, Rubella, Cytomegalovirus and Herpes Simplex Virus. As more infectious agents causing similar symptoms became recognized, the 'O' in TORCH is now denoted as "Other infections". TORCH infections acquired during pregnancy are one of the leading causes of prenatal and infant morbidity and mortality i.e. may lead to permanent fetal damage and even fetal loss.

Toxoplasmosis Toxoplasmosis infection is caused by an obligate intracellular parasite Toxoplasma gondii. This causative agent is a protozoan with a wide host range including humans and warm-blooded animals (especially cat family). Humans may get infected by consuming under cooked and contaminated meat pork, lamb, and venison) or shellfish, raw eggs, etc. Infections also occur from exposure to infected cat feces, litters and contaminated water or soil. Infected mothers may pass on the infection to the developing fetus through placenta (congenital toxoplasmosis). Higher risk of transmission has been found to be in later stage of pregnancy (third trimester). If mother gets infected in early stages of pregnancy first and second trimester), it may result in a more severe outcome such as miscarriage or birth defects in newborn. More recently it has also been discovered that T.gondii can be sexually transmitted. Incidence of Toxoplasmosis of 1 in 1,000 live births have been reported in newboms in India.

Rubella Rubella is a contagious viral infection that manifests in peculiar red rashes. Also known as German measles, it is caused by infection with Rubella virus (family Togoviridae) which has a single-stranded RNA genome. Rubella infection is spread by airborne transmission i.e. through inhalation of contaminated aerosol particles. Measles Rubella (MR) Vaccination given as a part of immunization programme in India has brought down the infection rate. However, infected pregnant women can pass on the virus to the developing fetus. Infection in the early stage of pregnancy may manifest a severe outcome at birth known as Congenital Rubella Syndrome (CRS). A higher incidence of congenital rubella infection (0.6% among asymptomatic infants and 12% among infants) has been reported in India.

Cytomegalovirus (CMV) CMV belongs to the virus family herpesviridae and has a double-stranded DNA genome. It is a common virus whose transmission is mediated through contact with infected body fluids such as saliva or urine. CMV can also be sexually transmitted. Infected mother can transmit CMV to newborn transplacentally or through breast milk. Majority of people and newborns with CMV infection may remain asymptomatic as CMV may remain latent. A higher risk to fetus has been reported if the mother acquires infection during initial stage of pregnancy (first trimester) which include hearing loss or epilepsy. About 1.8-2.1% incidence of congenital CMV has been reported in India.

Herpes Simplex Virus (HSV) HSV belongs to the virus family herpesviridae and has a double-stranded DNA genome. There are two forms - HSV1 (oral herpes) and HSV2 (genital herpes). Pregnant women may also acquire HSV infection via sexual contact with an infected person and subsequently pass the infection to the developing fetus during delivery. HSV1 infection may be acquired through direct skin-toskin contact with infected lesions after rupture of membranes leyes, skin or mouth contact). Neonates mostly acquire HSV2 infection while they pass through an infected birth canal during delivery. Incidence of HSV infection is between 1 in 1,000 and 1 in 5,000 live births.

Other Infections Syphilis Syphilis is a sexually transmitted disease caused by the spirochete Treponema pallidum. Pregnant women may also acquire Syphilis infection via sexual contact with an infected person and subsequently pass the infection transplacentally to the developing fetus. This infection can also spread through direct contact with a spirochete containing lesion. Risk of transmission (congenital syphilis) has been found to increase as the pregnancy progresses. If mother gets infected in early stages of pregnancy (first and second trimester), it may result in a more severe outcome.

Parvovirus B19 Parvovirus B19 belongs to the virus family Parvoviridae and has a single-stranded DNA genome. Parvovirus infection is also known as Fifth Disease and has peculiar presentation in the form of facial red rashes in children. The virus is transmitted through contact with contaminated respiratory tract secretions or contaminated blood. Pregnant women with parvovirus infection can transmit it to the fetus.

Human Immunodeficiency Virus (HIV) HIV belongs to the virus family Retroviridae. There are two types of HIV: HIV-1 and HIV-2. Both of them affect human beings. HIV genome consists of two single stranded RNA molecules. HIV can be transmitted due to sexual contact with infected person. Moreover, exposure to infected blood or use of contaminated needles or sharp objects may also transmit HIV. Transplacental transmission of HIV can happen to the fetus from infected pregnant mother with the highest risk of infection during delivery due to exposure to the maternal blood.

Varicella-Zoster Virus (VZV) VZV belongs to the virus family herpesviridae. It is highly infectious and known to cause Chicken Pox and Herpes Zoster (Shingles). VZV is transmitted via airbome contact with infected aerosols or respiratory secretions. VZV can be transmitted transplacentally from infected mother to developing fetus.

Common clinical manifestations associated with TORCH infections during pregnancy and in newborns are:

What is TORCH Screen test?
TORCH screen test is a panel of specific serological tests which measures the presence of antibodies against TORCH infections. TORCH screen panel includes measuring the IgM and IgG antibody titers of infections Toxoplasmosis, CMV, Rubella and HSV type 1 and 2 by Enzyme Linked Immunosorbent Assay (ELISA) technique. Serum sample is required for TORCH screen.

When we acquire any infection, our body's immune system produces different antibodies (immunoglobulins, Ig) to fight the foreign infectious agents. IgM antibodies are first produced to fight a new infection and is a measure of an acute infection. IgG antibodies produced later are the most abundant type of antibodies which remain in our body life long and is a measure of a past infection. Maternal IgG antibodies undergo selective transfer across placenta and confer protection to fetus against infections in future.

TORCH screen will thus help in identifying pregnant women who have acquired these infections and thus at a high risk to pass along these infections to developing fetus.

Interpretations:
IgM (positive). Current or present infection
IgM (negative) and IgG (positive) - Previous infection/ vaccination taken
IgM (negative) and IgG (negative) - No infection

Other Methods To Diagnose Torch Infections Real Time. Polymerase Chain Reaction (RT-PCR) - It is a sensitive test which detects and quantitatively measures the presence of individual infections principle of amplifying specific region of the genome of pathogen required to determine genotype. Detection of nfectious DNA OG RNA in amniotic fluid or chorionic villi can confirm fetal infection. It is used for diagnosis of Toxoplasmosis, Rubella, CMV, HSV, Syphilis, Parvovirus B19, VZV and HIV.

Culture (blood/urine/lesion/CSF) - Culturing of sample to detect specific pathogen and also checking the cytopathic effects on cells
Dark field microscopy and VDRL/RPR tests -For detection of Syphilis

Are only pregnant women at risk?
No. TORCH infections can affect anybody. Men, women (non-pregnant) and children may also catch these infections.

Then why so much emphasis on pregnant women?
Pregnant women with TORCH infections pass on these infections to the fetus either transplacentally or during the birth process through contact with blood or other body fluids.

I am pregnant but I have no symptoms. Should I also opt for TORCH screen?
Sometimes TORCH infections may not result in any visible clinical symptoms in the expecting mother, but the developing fetus may be at a major risk. All pregnant women may undergo TORCH screen.

Preventive Measures
Best method of preventing the TORCH infection is maintaining proper personal hygiene. Proper immunization can be provided to fetus in form of vaccination (Rubella vaccine). Routine TORCH screening in women planning for pregnancy can be a preventive measure. Consuming under-cooked meat should be avoided. Only clean drinking water (boiled or filtered) or properly washed fruits and vegetables should be consumed.

Thyrocare offers two TORCH - TORCH All Eight and TORCH All Ten. TORCH All Eight includes measuring Toxoplasma IgM and Toxoplasma IgG levels, CMV, Rubella and HSV by ELISA. TORCH All Ten includes measuring IgM and IgG levels of Toxoplasma, CMV, Rubella, HSV1 and HSV2 by ELISA.