Brazil has announced that it has received over 4,000 reports of a birth defect called microcephaly since October. At the same time, the nation has been experiencing an epidemic of Zika viral illness, transmitted from person to person through the bite of an infected mosquito. Public health authorities are suggesting that the two are more than coincidental. They have strongly suggested that pregnant women who contract Zika may find that their fetus or newborn now suffers from microcephaly.
Setting aside the issue of Zika viral infections for now, there are many causes for microcephaly. It should also be clear that Brazil had cases of microcephaly before the arrival of Zika, a “normal” level. Which known causes of microcephaly can be shown to preexist the Zika epidemic?
Causes of microcephaly
|Some Causes of Microcephaly|
|CDC ||Boston Children’s Hospital ||Cleveland Clinic |
|changes in their genes||an inherited defect in a gene||Chromosomal disorders such as Down’s syndrome, Cri du chat syndrome, Trisomy 13, and Trisomy 18|
|Infections such as rubella, toxoplasmosis, or cytomegalovirus||exposure to certain viruses – especially chickenpox, rubella (German measles) or cytomegalovirus||Maternal viral infections such as rubella (German measles), toxoplasmosis, and cytomegalovirus|
|Severe malnutrition||inadequate nutrition||Maternal malnutrition|
|Exposure to harmful substances, such as alcohol, certain drugs, or toxic chemicals||use of drugs or alcohol, abuse of prescription medications, exposure to toxic chemicals||Maternal alcoholism or drug abuse, Mercury poisoning|
|untreated phenylketonuria (PKU)||Uncontrolled maternal PKU|
Known Causes in Brazil
A study published in 2015 of 94 children in a Brazilian orphanage found that 17 percent had fetal alcohol spectrum disorders.  In an Aug. 2000 piece in Pediatrics titled Fetal Alcohol Syndrome and Alcohol-Related Neurodevelopmental Disorders, it states “… approximately 80% of children with FAS have microcephaly and behavioral abnormalities.”  A study in published in 2015 found “In 2003, the World Health Organization estimated that 19.1% of men and 4.1% of women in Brazil were in the category heavy episodic drinking. When analyzing only those who drank, these values rose to 32.4% for men and 10.1% for women.” 
A study published in 2014 found that Brazilian women who are pregnant or lactating may not change their eating habits to meet the nutritional needs of their condition. “The prevalence of nutrient inadequacy in pregnant women was higher than in reproductive-age women for folate…”  The U.S. National Library of Medicine states that “Pregnant women need to get enough folic acid. The vitamin is important to the growth of the fetus’ spinal cord and brain.” 
Toxoplasmosis – an infection by a feline parasite, Toxoplasma gondii. A study published in 2012 found “… 50-80% of women of child-bearing age have antibodies to T. gondii.” 
Cytomegalovirus – In a 2009 study conducted in SE Brazil, 1.08 percent of the children were found to have been born with congenital cytomegalovirus (CMV) infections.  In one study, as many as 25 percent of those with congenital CMV infections were also diagnosed with microcephaly. 
Screening of 653,375 live births in Bahia resulted in the finding of PKU with an incidence of “1 case for each 16,333 LB.” . This rate would result in about
12,661 cases throughout Brazil. [Correction Feb 8 2016 12:26 pm – I cannot determine how that number of cases was calculated. Reading the paper at the cite and others suggests that cases of PKU-microcephaly probably number less than 200 annually.]
Other Possible Sources
I have not found an incidence rate for Down’s Syndrome in Brazil. One large study published in 2010 for the incidence in the United States is 14.47:10,000 live births. 
The Brazilians have claimed that their national incidence for microcephaly is 0.5:10000. That suggest they have an estimated 148 cases of the birth defect yearly.
However, a study on the prevalence of toxoplasmosis in Brazil suggested that as many as 927 births every year suffer “neurological disease”, including cases of microcephaly.  This, alone, seems to indicate that Brazil has under-reported its case count.
An estimate can also be made for cases of microcephaly caused by Congenital cytomegalovirus infections. An estimated 31,899 cases of this type can be estimated to occur each year. (2,953,597 live births times 1.08 percent). Up to 25 percent of these children may have microcephaly, over 7,900.
Arbitrarily cutting both maximum totals (927 and 7,900) to ten percent still provides an estimated 883 microcephaly cases in Brazil every year. That is due to just two potential causes.
Brazil is coping with a large number of conditions and diseases that may result in microcephaly in newborns. The public health authorities in that nation clearly do not have a handle on what the “normal” number of cases ought to be. It continues to appear that the “outbreak” of microcephaly is nothing of the sort but is the recognition of something that had been there all along.
Sources and Citations
- Facts about Microcephaly – CDC
- Microcephaly Symptoms & Causes – Boston Children’s Hospital
- Microcephaly in Children – Cleveland Clinic
- Strömland, K., Ventura, L. O., Mirzaei, L., Fontes de Oliveira, K., Marcelino Bandim, J., Parente Ivo, A. and Brandt, C. (2015), Fetal alcohol spectrum disorders among children in a Brazilian orphanage. Birth Defects Research Part A: Clinical and Molecular Teratology, 103: 178–185. doi: 10.1002/bdra.23326
- Fetal Alcohol Syndrome and Alcohol-Related Neurodevelopmental Disorders, Committee on Substance Abuse and Committee on Children With Disabilities, Pediatrics: August 2000, VOLUME 106 / ISSUE 2
- Portugal Flávia Batista, Campos Mônica Rodrigues, Carvalho Juliana Ribeiro de, Flor Luisa Sório, Schramm Joyce Mendes de Andrade, Costa Maria de Fátima dos Santos. Disease burden in Brazil: an investigation into alcohol and non-viral cirrhosis. Ciênc. saúde coletiva [Internet]. 2015 Feb [cited 2016 Feb 01] ; 20( 2 ): 491-501. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1413-81232015000200491&lng=en. http://dx.doi.org/10.1590/1413-81232015202.01142014.
- dos Santos Q, Sichieri R, Marchioni D ML, Verly Jr. EBMC Pregnancy and Childbirth 2014 14:186 DOI:10.1186/1471-2393-14-186
- Folate deficiency – MedlinePlus
- Dubey JP, Lago EG, Gennari SM, Su C, Jones JL. Toxoplasmosis in humans and animals in Brazil: high prevalence, high burden of disease, and epidemiology. Parasitology. 2012 Sep;139(11):1375-424. doi: 10.1017/S0031182012000765. Epub 2012 Jul 10.
- Clin Infect Dis. (2009) 49 (4): 522-528. doi:10.1086/600882
- Sherwal BL, Jais M, Jyotsna K, Urvashi, Mehta G. Original Paper: Seroprevalence of Cytomegalovirus in Suspected Cases of Congenital Infections. Indian Journal for the Practising Doctor Vol. 5, No. 1 (2008-03 – 2008-04)
- Amorim Tatiana, Boa-Sorte Ney, Leite Maria Efigênia Q, Acosta Angelina Xavier. Clinical and demographic aspects of phenylketonuria in Bahia State, Brazil. Rev. paul. pediatr. [Internet]. 2011 Dec [cited 2016 Feb 01] ; 29( 4 ): 612-617. Available from: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0103-05822011000400022&lng=en. http://dx.doi.org/10.1590/S0103-05822011000400022.
- Parker SE, Mai CT, Canfield MA, Rickard R, Wang Y, Meyer RE, Anderson P, Mason CA, Collins JS, Kirby RS, Correa A. Updated National Birth Prevalence estimates for selected birth defects in the United States, 2004-2006. Birth Defects Res A Clin Mol Teratol. 2010 Dec;88(12):1008-16. doi: 10.1002/bdra.20735. Epub 2010 Sep 28.