The Toronto Globe & Mail reports that Brazilian health officials are a bit baffled by Zika’s link to fetal brain defects. The Ministry of Health has launched an investigation into the cluster of babies born with brain defects linked to the Zika virus, after an expected “explosion” of cases across the country did not occur. The bulk of the cases of congenital Zika syndrome remain clustered in the northeast region of the country where the phenomenon was first identified last October, the ministry says.
“We can see there is a kind of cluster in [part of] the northeast region with high prevalence and high severity, of miscarriage and congenital malformation that is really severe,” said Fatima Marinho, co-ordinator of epidemiological analysis and information at the ministry. “But we didn’t find this in other states – even the [adjacent] states didn’t see the same situation as in the epicentre.… We were preparing for an explosion and it didn’t come.
A central theory the ministry is now exploring is whether co-infection with other viruses, such as dengue or chikungunya, is the factor.
The ministry is also looking at social determinants, because initial analysis makes it clear the women with affected fetuses have a clear “profile.” Some 77 per cent of them are black or mixed-race (the national figure is 52 per cent), and the great majority are poor.
Because the virus produces no symptoms in up to 80 per cent of people who get it, and only mild symptoms in many others, few people confirm Zika infection with laboratory tests, and so statistics of Zika cases are always estimates.
After Brazil, the next country that was expected to see the wave of congenital Zika was Colombia, which has the second-largest number of reported Zika cases. But of more than 12,000 pregnant Colombian women with Zika, only 21 have had fetuses or babies with the brain defects.
According to a report by the New England Complex Systems Institute (NECSI), the number of missing cases in Colombia and elsewhere raises serious questions about the assumed connection between Zika and microcephaly.
In light of this evidence, NECSI says the cause of microcephaly in Brazil should be reconsidered. One possibility that has been raised is the pesticide pyriproxyfen, which is applied to drinking water in some parts of Brazil to kill the larvae of the mosquitos that transmit Zika.
A report by the Swedish Toxicology Sciences Research Center also raises the pesticide link: “The recent claims that increases in the use of the PPF insecticide in affected and/or high risk areas, may contribute in some way to the growing medical problem cannot pass without further investigation, as it may constitute a potentially complex human health risk situation that must be addressed post-haste.”
A change in the pattern of usage of this pesticide from the beginning of 2014 was claimed to coincide with a rise in the incidence of children born with microcephaly in affected areas of Brazil. This association was denied by the Brazilian Ministry of Health.
On July 15, Adriana Melo, a fetal medicine specialist in the state of Paraiba who was the first to find Zika in the brains of affected babies, released research in which she and her co-authors report finding proteins of bovine viral diarrhea virus (BVDV), a cattle disease, in the brains of three fetuses with microcephaly from Paraiba whose brains also tested positive for RNA from the Zika virus.
BVDV is known to cause serious birth defects in cows, but not to infect people. Their hypothesis is that Zika infection may weaken physiological barriers, so the cow virus that would not normally affect a human fetus can cause damage.
Meanwhile, the US is racing to test and approve vaccines to protect against the virus. This week, the National Institute of Health began human trials of a vaccination.
In May, House Republicans pushed through a bill they described as aiding local governments spray against disease-carrying mosquitoes. Under the new law, states and the EPA don’t have to require a permit from companies before they dump federally approved pesticides into navigable waterways.
Residents of Florida are being sprayed with an organophosphate neurotoxin called naled by air. Naled’s health effects include it being a severe skin and eye irritant, but it is most harmful and potent if it is inhaled. Toxicologists at the University of California found that naled when inhaled is twenty times more toxic to rats as opposed to when it is ingested. It can cause chronic nervous system damage. It is very toxic to most organisms.
Yaneer Bar-Yam, Dan Evans, Raphael Parens, Alfredo J. Morales, Fred Nijhout. Is Zika the cause of Microcephaly? Status Report. New England Complex Systems Institute, June 22, 2016
Pyriproxifen and microcephaly: An investigation of potential ties to the ongoing “Zika epidemic”, SWETOX (March, 2016), http://swetox.se/wp-content/uploads/2016/03/ppf-zika.pdf.