Vertical Transmission infections [TORCH]

 

Vertical Transmission infections

“vertically transmitted infection is an infection caused by pathogens (such as bacteria and viruses) that use mother-to-child transmission.”

 

Types of infections:

Several vertically transmitted infections are included in the

“TORCH complex”

T – toxoplasmosis from Toxoplasma gondii

O – other infections (see below)

R – rubella

C – cytomegalovirus

H – herpes simplex virus-2 or neonatal herpes simplex

 

Vertical transmission of pathogens:

Babies born of pregnant women who are infected with a particular virus are at risk of contracting that virus from the parent. Transmission is more likely when the baby is in direct contact with the mother’s fluids, such as during breastfeeding and also in utero if there are breaks in the placental barrier, although most vertical transmissions occur during delivery.

Multiple types of virus can be passed from mother to child via vertical transmission, including those known as “TORCH” pathogens: toxoplasma gondii, other (listeria monocytogenes, treponema pallidium, parvovirus, HIV, varicella zoster virus), rubella, cytomegalovirus (CMV), and herpesviruses (HSV) 1 and 2.

Recently, the Zika virus (ZIKV) was identified as being transmissible vertically, adding to the TORCH pathogens which have now become a focus of research once again. The emergence of the Zika virus has reignited the need to address vertical transmission.

Even in developed countries, such as the US, infections with TORCH pathogens are linked with severe disease in infants. Additionally, infection rates in developed countries remain high, with up to 4,000 infants born in the US annually with toxoplasmosis infections which can cause blindness, developmental delay, epilepsy and more. Infections of the CMV virus are even more common, with 40,000 infants born in the US each year with congenital infections of the virus which can require complex surgical attention.

 

Signs and symptoms:

Subtle signs such as an influenza-like illness, or possibly no symptoms at all. In such cases, the effects may be seen first at birth.

Symptoms of a vertically transmitted infection may include fever and flu-like symptoms. The newborn is often small for gestational age. A petechial rash on the skin may be present, with small reddish or purplish spots due to bleeding from capillaries under the skin. An enlarged liver and spleen (hepatosplenomegaly) is common, as is jaundice. However, jaundice is less common in hepatitis B because a newborn's immune system is not developed well enough to mount a response against liver cells, as would normally be the cause of jaundice in an older child or adult. Hearing impairment, eye problems, mental retardation, autism, and death can be caused by vertically transmitted infections.

 

During childbirth:

Babies can also become infected by their mothers during birth. Some infectious agents may be transmitted to the embryo or fetus in the uterus, while passing through the birth canal, or even shortly after birth. The distinction is important because when transmission is primarily during or after birth, medical intervention can help prevent infections in the infant.[citation needed]During birth, babies are exposed to maternal blood, body fluids, and to the maternal genital tract without the placental barrier intervening. Because of this, blood-borne microorganisms (hepatitis B, HIV), organisms associated with sexually transmitted diseases (e.g., Neisseria gonorrhoeae and Chlamydia trachomatis), and normal fauna of the genitourinary tract.

 

TORCH infection during pregnancy:

TORCH infections are the term given to a group of infectious diseases that can be passed to your baby during pregnancy, at delivery or after birth. TORCH stands for toxoplasmosis, rubella, cytomegalovirus, herpes and other agents.

Diagnosis:

When physical examination of the newborn shows signs of a vertically transmitted infection, the examiner may test blood, urine, and spinal fluid for evidence of the infections listed above. Diagnosis can be confirmed by culture of one of the specific pathogens or by increased levels of IgM against the pathogen.

 

Prevention methods for vertical transmission:

While more research into the mechanism of vertical transmission is needed, there are currently a number of preventative methods employed to reduce the vertical transmission of pathogens. To prevent the vertical transmission of HIV, doctors test mothers for infection with the virus and in the case of maternal infection, the best practice involves controlling maternal infection, implementing prenatal antiviral therapy and treating the mother and baby during labor and delivery, delivering the baby by cesarean section rather than a natural birth.

 

 Treatment:

Some vertically transmitted infections, such as toxoplasmosis and syphilis, can be effectively treated with antibiotics if the mother is diagnosed early in her pregnancy. Many viral vertically transmitted infections have no effective treatment, but some, notably rubella and varicella-zoster, can be prevented by vaccinating the mother prior to pregnancy.

 

Pregnant women living in malaria-endemic areas are candidates for malaria prophylaxis. It clinically improves the anemia and parasitemia of the pregnant women, and birthweight in their infants.

 

If the mother has active herpes simplex (as may be suggested by a pap test), delivery by Caesarean section can prevent the newborn from contact  and consequent infection with this virus.

IgG2  antibody may play a crucial role in prevention of intrauterine infections and extensive research is going on for developing IgG2-based therapies for treatment and vaccination.[ntact, and consequent infection, with this virusvoiding breastfeeding when possible.

 

Vertical transmission of COVID-19:

Back in March 2020, the World Health Organization determined the COVID-19 outbreak to be a pandemic. To date, there have been more than 113 million cases confirmed in the laboratory and more than 2.5 million deaths have been attributed to COVID-19. While COVID-19 remains a significant threat to public health, its impact on infants born to infected mothers remains unclear.

 Other viral infections, such as influenza, are well documented as increasing the risk of severe illness in pregnant women. Current research seems to suggest the risk of severe disease is not typically increased in pregnant women, with minimal risk to mother and child in most cases. However, age and pre-existing conditions can increase the risk of complications (for more information on this see COVID-19 and pregnancy).

Furthermore, whilst COVID-19 in newborns is rare, there have been cases of positive COVID-19 testing within 24 hours of birth (most of which have had mild or no symptoms). It is unknown whether newborns in these cases have contracted the virus before, during or post-birth.

This has led scientists to question whether SARS-CoV-2 could be transmitted vertically. While this was never documented in SARS-CoV and Middle East respiratory syndrome (MERS), far fewer people contracted these viruses so datasets may not have been large enough to detect it.

A recent paper, published in the journal Nature Communications in October 2020, has provided data that shows that babies born to SARS-CoV-2-positive women demonstrate elevated SARS-CoV-2-specific immunoglobulin G (IgG) and IgM antibody levels. This evidence suggests transference of the virus across the placenta, and, therefore, suggests vertical transmission occurred. 

Additionally, a newer study, published in the American Journal of Obstetrics and Gynecology in January this year has revealed evidence that suggests that vertical transmission is most likely when the mother is infected during the third trimester. Again, further evidence is required to more thoroughly understand the nature of vertical transmission in COVID-19.

Overall, the future prevention of vertical transmission of a range of viruses will heavily depend on the research that is conducted going forward. There is a clear need to protect children from vertical transmission in order to protect their health. The emergence of COVID-19 may help to direct attention towards this need, just as the Zika virus did.