Lab Grown Mosquitoes Reduce Dengue Fever

Dengue Fever is a serious viral infection transmitted by Aedes mosquitoes that become infected by biting a carrier and then bite a non-infected individual. There are four distinct Dengue virus types so humans can contract the disease four times. The mosquito that transmits Dengue can also transmit the Zika virus and Chikengunya virus.

Dengue has been a disease primarily seen in the Caribbean islands, Central America, South America and Asia. With climate change and migration the disease is moving northward and cases are seen routinely now in Southern Florida and Texas.  Most cases are self-limiting and considered non-life threatening with symptoms of headache, eye pain, severe bone pain, muscle and joint pain, rash and sometimes nausea and vomiting. Treatment is supportive with hydration and pain relief

Individuals who survived an initial Dengue infection and then are re-infected are more likely to develop the severe form of the disease. When their initial fever resolves they develop severe abdominal pain, vomiting and bleeding from the nose or gums. This is a life threatening illness and requires immediate emergency medical attention.

At the recent meeting of the American Society of Tropical Medicine and Hygiene, investigators discussed the success of the release of genetically modified Aedes mosquitoes carrying the Wolbachia bacterium in reducing Dengue infections. This bacterium prevents the transmission of the Dengue virus from mosquito to humans. These modified mosquitoes have been bred and released in Brazil, Indonesia and Australia with a marked reduction in Dengue infections in humans.

Currently a Dengue Fever preventive vaccine is in the experimental phase as well. With climate change and population growth, the CDC expects up to 60% of the world’s population to be at risk from Dengue in the future.

Zika Update

Zika is an infectious virus introduced to Florida by individuals who traveled to South and Central America plus the Caribbean Islands and were infected by the bite of an aegypti mosquito or a close relative of that mosquito. They then brought the infection back to the USA. The disease has an incubation period of less than two weeks and generally produces a mild illness that most adults do not even know they have. Fever, aches and pains, a fleeting rash, headache and conjunctivitis are common symptoms. Once infected the disease can be transmitted from human to human by body fluids during sexual activity. It can additionally be transmitted when an infected individual is bitten by a mosquito and then it bites a human being. Fortunately the mosquitoes have a flight range of about 100 yards. It is the mobility of infected human beings causing the geographical spread of the virus more than mosquitoes. The virus infects a male’s semen and can remain infectious for about six months. This has led to the suggestion that infected men use condoms when having sex for six months post infection.

The disease is mild in adults but the body’s response to infection has produced a neurological ascending paralysis known as Guillan Barre Syndrome (GBS) at three times the expected rate of this diseases occurrence.  GBS is painful and can affect our respiratory muscles necessitating the use of mechanical respirators and ICU care for survival. The disease is most dangerous in pregnant women causing permanent brain and developmental damage and death in developing fetuses.

At the current time treatment is supportive. There are lab tests to detect an infection using blood and urine specimens. A vaccine to prevent infection is under development with early success noted in rhesus monkeys. Prevention at this point involves practicing safe sex, avoiding mosquito bites using repellant and appropriate clothing.  The mosquito spreading Zika bites during daylight hours. Spraying to reduce the mosquito population is an ongoing strategy being hampered by poor funding. An experimental project to introduce sterile genetically engineered female mosquitoes is being hampered by lack of funding and citizen concern about potential dangers of releasing mutated mosquitoes.

President Obama asked Congress last spring for 1.9 billion dollars to fight Zika but Congress adjourned without providing any funds. The CDC used other funds to begin the research and fight against Zika but is rapidly running out of funds.

Zika Virus: Updates and Need for Congressional Action

As we move from spring to summer we will be facing warmer temperatures, higher humidity and more rain.  This creates a perfect environment for standing water mosquito breeding grounds, and an increase in the mosquito population especially the Aedes aegypti which carries the Zika Virus, Dengue Fever and Chikengunya Viruses.  President Obama and the Center for Disease Control have asked the United States Congress to allocate 1.9 billion dollars to fight Zika virus but conservative Republican elected officials have failed to address the issue. As a short term stop gap measure the CDC has suspended its work on Ebola and other hemorrhagic diseases and begun using those funds for Zika Virus research.  They are in the process of developing a Zika Virus Vaccine for prevention in humans but are several years away from achieving this.  Zika virus is currently widespread in South America, Central America and the Caribbean Basin.  While the infection produces an extremely mild clinical pattern in most humans, it causes severe birth defects in pregnant women including microcephaly or small skull or cranial cavity for an enlarging growing brain. Infected fetuses result in spontaneous abortion, death of the child or lifelong neurologic deficits. At this point researchers are not sure exactly at what point in a pregnancy, exposure to the Zika virus causes birth defects.  In adults the disease is mild but the body’s antibody response against the virus can result in progressive ascending paralysis with a disease known as Guillan Barre. Many of these patients eventually have their diaphragm and respiratory muscles involved and require intubation and respirators to survive. If they survive the adult illness they are often left with painful neurologic issues post paralysis.  To date most Zika infections occurred in travelers returning from areas of the world overrun with Zika. There has been documented sexual transmission of the virus between an infected and uninfected partner.  The disease symptoms are so mild in some they do not even realize they are infected.

The fear is that with the warm wet weather our local mosquito population will become infected with the Zika virus by sampling the blood of infected individuals and start a local epidemic.  NASA has created a model which predicts an epidemic in South Florida, Houston and southern Texas and parts of Louisiana. Mosquito control is one means of fighting the vector of transmission. Most local spraying programs hope to reduce the mosquito population by 50% to be considered successful but this rate of success will not prevent transmission of these three viruses.  Officials in the Florida Keys have begun releasing sterile male Aedes aegypti mosquitoes into the population in the hopes of reducing the overall mosquito population.  In a recent article in the journal Cell Symposia, researchers presented data suggesting that infecting the male Aedes aegypti mosquito with parasitic bacteria known as Wolbachia may inhibit viral replication of the virus and transmission by mosquito bites.  They have already shown that infecting mosquitoes with this parasitic bacterium reduces the spread of Dengue fever and Chikengunya.  To move forward with a project like this requires Federal funding and Congress is delaying addressing the issue as part of the politics of NO in an election year.

To protect yourself this spring and summer please make sure there is no free standing water on your property which can be used as a breeding ground by mosquitoes. Make sure your screens are intact at your home.   Wear long sleeves and use insect repellant. Consumer Reports still recommends repellant with 8 – 30% DEET, 20% Picardin or 30% Oil of Lemon Eucalyptus. They specifically suggest Sawyer Fishermans Formula Picardin or 2 Repel Lemon Eucalyptus or Deep Woods Off with 25% DEET.  Above all contact your Congresspersons and Senators and encourage them to fund the fight against Zika.