Zika

   After a lifetime in medicine I hadn't even heard of the Zika virus, until just recently.  The Director of the United States National institute of Allergy and Infectious Diseases pointed out that it was regarded as clinically inconsequential and that it wasn't even on a recent World Health Organization list of pathogens that need urgent research.  It was first discovered in 1947 and is carried by the mosquito Aedes Aegypti.  It causes a mild flu-like illness in about 25% of the people infected.  It occurred almost exclusively in Africa but in recent years has been found in Micronesia and the Polynesia.  Then, in the last year it appeared in Brazil and other South American countries, as well as Puerto Rico,  A.Aegypti is the vector of Dengue Fever and Yellow Fever     the Zika virus was thought to bejust a mild virus that it also sometimes carries.
   Last year Brazil was noted to have a very significant increase in the number of cases of microcephaly cases which coincided with the incidence of Zika.  Microcephaly is a neurodevelopmental disorder in which the baby is born with a major brain deficit and a small head and severe cognitive and  sometimes motor disorders.  Seizures are common.   The association does not prove that Zika causes the microcephaly.  There are also reports of outbreaks of Guillain-Barre syndrome associated with the Zika outbreaks.
  Control of the diseases that a mosquito propagates is achieved by eradication of the mosquito.  This is very resource dependent particularly in the third world counties most affected.  
   One of the current research projects is to genetically modify male mosquitoes so that their offspring don't survive.  These males don't bite, so they can't transmit   disease.   The suppression is achieved by a self-limiting gene prevents the offspring from surviving.  The modified mosquitoes do not bite or spread disease and their offspring inherit the self-limiting gene and die before reaching adulthood. To produce more of the mosquitoes for control projects the self-limiting gene is switched off using the antibiotic tetracycline.  This does not happen in the wild, so the mosquito population is suppressed.  The altered mosquitoes are called OX513A.
   Now, at first glance, this seems to be a giant step forward in solving the problem.  However, a friend of mine brought to my notice speculations about genetic engineering that raise some troubling concerns and I intend to share those concerns with you in a subsequent blog.  We'll look at such strange entities as 'promiscuous' transposons and jumping genes and the ominous consequences that could result from genetic meddling.   So don't miss next week!