you are here: home > explore > zika virus
Written by Sloka Iyengar,
Ph.D., Neuroscience for Kids Guest Writer
June 20, 2016
Infection of the pregnant mother by Zika virus may cause microencephaly, a condition where the baby's head is smaller than expected as compared to babies of the same sex and age. Guillain-Barr syndrome, a condition where the immune system attacks the nerves, may also occur
Microencephaly resulting from the Zika virus may be mild or severe. The clinical definition of microencephaly is that the head occipto-frontal circumference is more than two standard deviations below the mean for age and gender. Babies with microencephaly have smaller and less developed brains. An ultrasound test in the third trimester can sometimes identify the problem. Microencephaly may cause seizures, developmental delays, problems walking and with motor coordination and delays in hearing, vision and speech. There is no way to reverse the small size of the head. Therefore, these babies need close follow-up with their healthcare provider to monitor their growth and development. Speech, occupational and physical therapy also help.
Neuronal development is a complicated process that requires generation, migration and differentiation of neurons. Microtubules, microscopic structures found in the cytoplasm of neurons, play a critical role in all the development of the nervous system. Tubulin, a protein that is an important component of microtubules, and mutations in certain subtypes of tubulin protein have been linked to various neurodevelopmental disorders.
Scientists have reported that a depleted subtype of tubulin known as Tubb5 prevents the proper migration of neurons in mice. The scientists also looked at three patients with microencephaly and found mutations in Tubb5 in all of them. Therefore, it is likely that Tubb5 is an important factor in the development of microencephaly. It remains to be determined if Tubb5 is involved with microencephaly associated with Zika virus.
Zika virus has also been linked to Guillain-Barr syndrome. In contrast to microencephaly which affects the central nervous system, Guillain-Barr syndrome affects the peripheral nervous system. Specifically, the immune system mistakenly identifies peripheral nerves as intruders and damages the myelin insulation resulting in muscle weakness and changes in sensation and pain. In Guillain-Barr syndrome, white blood cells target and attack the Schwann cells, and hence the myelin coating on peripheral neurons.
Copyright © 1996-2016, Eric H. Chudler, University of Washington