Letter to the Editor: Regarding Zika Microcephaly

| July 1, 2018 | 0 Comments

By Beuy Joob, PhD, and Viroj Wiwanitkit, MD

Funding/financial disclosures: The authors have no conflicts of interest relevant to the content of this letter. No funding was received for the preparation of this letter.

Dear Editor:

We read the article on zika microcephaly, which was published in the September-October 2017 issue of ICNS with a great interest.[1] Kolikonda et al[1] stated, “Even infants with normal head circumference at birth might develop microcephaly in early infancy because of deceleration in head growth.”[1] The authors also stated, “Regular developmental follow-up is indicated.”[1] We would like to share our ideas and experience regarding this issue. In fact, the zika virus infection-related microcephaly is an important issue in clinical neurology. Prevention of the infection is an important concept, but it is usually difficult to achieve, and many questions still remain regarding the zika virus. In our setting, tropical Asia, the zika virus infection is endemic, and there are many asymptomatic exposures among the local population.[2] Interesting to note, however, is that zika microcephaly is not a problem in our region,[3] and there has been no cases of late deceleration of head growth in exposed infants. Obviously more research is needed to fully understand the zika virus and its impact in clinical neurology.

REFERENCES

  1. Kolikonda MK, Srinivasan K, Enja M, Sagi V, Lippmann S. Zika microcephaly. Innov Clin Neurosci. 2017;14(9– 10):11–12.
  2. San K, RajadhanV. Seroprevalence of Zika virus in Cambodia: a preliminary report. Adv Lab Med Int. 2016;6(3):37–40.
  3. Sriwijitalai W, Wiwanitkit V. Zika virus infection, pregnancy and microcephaly. Rev Bras Ginecol Obstet. 2018;40(1):53.

With regards,

Beuy Joob, PhD

Sanitation, Medical Academic Center, Bangkok, Thailand

Viroj Wiwanitkit, MD

Honorary professor, Dr DY Patil University, Pune, India

Author Response

By Rajashekar Reddy Yeruva, MD, and Steven Lippmann, MD

Funding/financial disclosures: The authors have no conflicts of interest relevant to the content of this letter. No funding was received for the preparation of this letter.

We appreciated learning that zika-induced microcephaly does not occur in some zikaendemic areas. The history of zika might explain why the prevalence of zika-induced microcephaly incidence is rare in some areas of Asia and Africa. The zika virus was first identified in Africa in 1958.[1] During the 1950s, zika infections in humans were described as mild, self-limited, modestly febrile illnesses with maculopapular cutaneous eruptions.[2] Zika virus infections in Asia were documented during 1966,[3] but the 2007 epidemic in Micronesia also included conjunctivitis, pharyngitis, cephalgia, and arthralgia.[4] The 2013 to 2014 epidemic in French Polynesia revealed a dangerous association between zika infection and Gullian- Barre syndrome and meningoencephalitis.[5] The Brazilian 2015 outbreak evidenced zika as etiology for gestational microcephaly, mental retardation, and neurologic and/or other congenital anomalies.[6]

The zika virus evolved from a mild, localized condition to a serious public health crisis involving huge numbers of people in the world. Alteration in the pattern and effects of this viral infection might be related to replication and transcription changes newly becoming part of its genetic profile.[7] The pre-membrane precursor (prM) protein of the zika virus is documented with greater variability when comparing the virus in Asian humans to those in African mosquitoes. That variability could contribute to structural differences in the virus. Amino acid or nucleotide variations might induce neurotropism, heightened transmissibility, and mosquito vector infectivity to humans.[7] Sequence variations can mediate specific alterations in the prM protein, which affect virulence and might partially explain why it spread to human populations in the Americas.[7]

More rare occurrences of microcephaly could be related to population factors, viral mutations, immunity in the population, herd immunity induced by endemic long-term presence of the virus, and/or low sensitivity of surveillance systems. A zika outbreak causing congenital microcephaly in Brazil was evident.[6] In a retrospective assessment of infected infants, it was documented that despite absence of microcephaly at birth, some infants with laboratory evidence of zika virus infection evidenced brain anomalies associated with a congenital zika syndrome. Neuroimaging revealed ventriculomegaly, decreased brain volumes, cortical malformations, and subcortical calcifications.[8] Time will clarify the future patterns of zika virus existence and its effects on humans.

References

  1. Dick GW, Kitchen SF, Haddow AJ. Zika virus. I. Isolations and serological specificity. Trans R Soc Trop Med Hyg. 1952;46(5):509–520.
    2.Simpson DI. Zika virus in man. Trans R Soc Trop Med Hyg. 1964;58:335–338.
  2. Marchette NJ, Garcia R, Rudnick A. Isolation of Zika virus from Aedes aegypti mosquitoes in Malaysia. Am J Trop Med Hyg. 1969;18(3): 411–415.
  3. Duffy MR, Chen TH, Hancock WT, et al. Zika virus outbreak on Yap Island, Federated States of Micronesia. N Engl J Med. 2009;360(24):2536– 2543.
  4. Cao-Lormeau VM, Blake A, Mons S, et al. Gullain- Barre syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. Lancet. 2016;387(10027):1531–1539.
  5. Bogoch II, Brady OJ, Kraemer MU, et al. Anticipating the international spread of zika virus from Brazil. Lancet. 2016;387(10016):335–336.
  6. Wang L, Valderramos SG, Wu A, et al. From mosquitos to humans: genetic evolution of zika virus. Cell Press. 2016:561–565.
  7. Van der Linden V, Pessoa A, Dobyns W, et al. Description of 13 infants born during October 2015–January 2016 with congenital zika virus infection without microcephaly at birth-Brazil. MMWR (Morbidity and Mortality Weekly Report). 2016:65.

With regards,

Rajashekar Reddy Yeruva, MD

Research Associate, University of Louisville School of Medicine, Louisville, Kentucky

Steven Lippmann, MD

Emeritus Professor, University of Louisville School of Medicine, Louisville, Kentucky

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