Zika Updates

Things have happened so quickly on the Zika virus front over the past three months, I thought a short update might be in order.  You may recall a post I wrote in December warning about a need to brace ourselves for what might possibly be a big year for the new Zika phenomenon.  As my wife might say, "Well, at least you were right this once."  A quick peak at Google Trends surely bears this out.  The following graph shows the relative number of times people on the Internet used the search term "Zika" in recent years:


Much of the excitement about Zika virus, of course, has centered around the possibility, insisted on by many Brazilian public health officials, that there is a connection between Zika infection and a condition in newbornes called microcephaly.  Since the initial reports, there has been some pretty wild speculation about whether Zika really is the cause of the condition.  One was a blog posted on Reddit, a "social networking newsite" that bills itself as "the front page of the Internet".  The post speculated that the real reason there had been no previous connection between microcephaly and Zika was that the microcephaly in Brazil was actually linked to experiments with genetically modified mosquitoes in some parts of the country where microcephaly was rampant. Many people have since discredited the logic behind this conspiracy theory.  But expect this idea to float around the Internet for a long time anyway--that's what conspiracy theories do.

Another theory posted online claimed that the real reason for microcephaly increases in Brazil is a pest control insecticide being used in the drinking water of Zika outbreak zones.  The insecticide was pyriproxifen, which we in the pest control industry use under the trade names Nylar® and Archer® flea and roach sprays. The anti-GMO group blaming pyriproxyfen claims that the association between microcephaly and areas where pyriproxyfen is used "is not a coincidence." Like the genetically modified mosquito claim, this group also asserted that so far, there have been no cases of microcephaly reported in other countries affected by Zika. While microcephaly does not (yet) seem to be as prevalent in some Zika areas, like Colombia, this claim is not strictly true. Higher rates of central nervous system malformations were also found in French Polynesia following the Zika outbreak there in 2014.  In addition, there is no scientific evidence of any connection between pyriproxyfen and brain abnormalities, and officials in Brazil point out that some areas that do not use pyriproxyfen to treat mosquitoes still have seen increases in microcephaly.  Pyriproxyfen, by the way, is an insect growth regulator that is one of the lowest toxicity treatments (LD50 greater than 5000 mg/Kg) available for fleas, cockroaches and other pests. The EPA does not consider it an endocrine disruptor, and it is not considered a carcinogen.

On the scientific side, last week an article was posted in the New England Journal of Medicine (a much more reliable source than social networking news sites) that provides some of the strongest evidence yet for a link between Zika and microcephaly.  Fetuses from 42 women with evidence of Zika infection during gestation were examined.  Preliminary analysis of ultrasound examination of these fetuses showed 29% (!) occurrence of microcephaly in infected women compared to 0% in 17 non Zika infected women.  The authors concluded that "despite mild clinical symptoms, ZIKV infection during pregnancy appears to be associated with grave outcomes, including fetal death, placental insufficiency, fetal growth restriction, and [central nervous system] CNS injury."

If research continues to show similar associations between Zika infection and microcephaly the stakes are surely raised this summer with thousands of expected travelers coming back into the U.S. from Zika zones, including the Olympic venues in Brazil.  All the more reason for all of us to be aware of travel safety recommendations by the CDC.

For our part, Texas A&M is also ramping up its educational efforts this summer with launch of a new website to collect information pertaining to ways to prevent Zika.  The bottom line of all the current news, however, is that there is currently no way to prevent getting the disease from an infected mosquito other than by avoiding mosquito bites.  And pest control is an important part of that equation.  So take the time to learn more about the Aedes mosquitoes that carry Zika, and consider how you might respond to the concerns that are sure to be around this summer.

Bracing for Zika

Will Zika be the next mosquito-borne disease to capture headlines in 2016?  Or will it be the little disease that few (at least in the U.S.) have heard of?  That's the question being debated by public health officials this year.

Current (2015) worldwide range of zika virus. Central and South
American countries were first reported with the disease in
2015 (U.S. Centers for Disease Control).

For many years it seemed like new things happened relatively slowly in public health in Texas. In the mid-1980s entomologists reported the Asian tiger mosquito in Texas for the first time--a daytime-flying mosquito from Japan that is not shy about biting humans. Then in 2002 the first cases of west Nile virus hit our state.  Carried by the southern house mosquito, WNV affected a couple of hundred people or less each year. This was the case until the blazing hot summer of 2012 when over 1800 cases were reported, including 83 deaths. Health departments throughout the state are still reeling, in some ways, from the impact.

Now health officials are bracing for another mosquito-borne disease caused by Zika virus (abbreviated ZIKV by epidemiologists).  A cousin of west Nile virus and dengue fever, ZIKV has been thought of as a less severe form of these flavivirus.  Most people who get ZIKV show no, or very mild symptoms.  Others exhibit a rash, conjunctivitis (inflammation of the eye), and flu-like symptoms.  Most people do not get as sick with ZIKV as with dengue fever or chikungunya, and recover relatively quickly.

For this reason, since its discovery in 1947 until 2007, it was not on the radar of many public health experts. But in 2007 ZIKV cases started to spread throughout Micronesia French Polynesia, and eventually Easter Island. There it was thought to possibly be the cause of a twenty-fold increase in cases of Guillain-Barre syndrome--an autoimmune disease of the central nervous system that can be highly disabling, at least temporarily.

In 2015 the disease made its appearance in Brazil and has since spread to at least nine other member states of the Pan-American Health Organization (PAHO/WHO), and prompting that organization this month to issue an alert to all of member public health agencies.

So here's where things get a little scary.  Since the arrival of ZIKV to Brazil, the virus has been detected in babies born with a condition known as microcephaly.  Microcephaly is a relatively rare condition where the brain fails to develop normally. It may result in miscarriage or in babies being born with under-sized brains.  There is no cure for the condition.  The PAHO/WHO alert noted that the number of diagnosed cases of microcephaly has increased to 2700, a 10-fold increase, in Brazil this year.  Health officials there are worried that there might be a connection between this unprecedented increase in microcephaly and the arrival of ZIKV.  And last month, unusual nervous system birth defects were also reported in Polynesian mothers who tested positive for flavivirus antibodies.

Public health officials guess that these cases may result when a pregnant woman who is bitten by an infected mosquito contracts the virus.  The virus then infects the developing fetus, resulting in this serious condition.

So far there is no hard proof of a connection between ZIKV and microcephaly or Guillain-Barre syndrome, but medical researchers are rushing to learn more about the virus and its possible effects on human health.  According to one expert, quoted in the New York Times, it could be that the risk of microcephaly is increased among people who have previously contracted dengue fever or chikungunya, neither of which diseases are common to Texas or the U.S. If this hypothesis proves correct, the risks to the unborn in this country would likely be negligible.

Currently, ZIKV is thought to be transmitted by the yellow fever mosquito, Aedes aegypti.  This mosquito, along with its close relative, Aedes albopictus, the Asian tiger mosquito, are both very common throughout Texas and the southern U.S.  Unlike west Nile virus, which is primarily a disease of birds, ZIKV is solely a disease of primates.  To be spread among people, it must be picked up from another infected human.

Dengue and chikungunya are similar, human-only, viruses that have not been quick to spread in Texas or other U.S. locations.  This may be the result of lower rates of mosquito biting in the U.S., perhaps due to our more indoor lifestyles, or more common use of repellents.  Some experts argue that for similar reasons ZIKV is likely to be slow to establish in the U.S.  Nevertheless, Brazil shows that given the right conditions, this virus is capable of establishing itself very rapidly, with 85,000 known infections in its first year of spread.

A few U.S. cases of ZIKV have been reported in 2015, but all from travelers who contracted the virus elsewhere.  Mexico has also seen a few cases this year.  There are still no known cases of ZIKV, however, contracted within the U.S.

So be prepared to hear more about the zika virus this year.  It may turn out to be a big event, or it may not.  Even if we didn't need more reasons to dislike biting mosquitoes, now we have one more reminder of the importance of residential mosquito control, and putting on the insect repellent when venturing outdoors.