For thousands of years, humans have struggled against infectious diseases transmitted by mosquitos. Records describing the symptoms of malaria can be traced back to 2700 B.C. in China. Other mosquito-borne diseases, such as yellow fever, dengue, and West Nile virus are a perennial threat to the health and safety of people all over the world.
One mosquito-borne illness that has rapidly gained notoriety recently is the Zika virus. This disease was first documented in monkeys in Uganda in 1947, and then in humans in 1952. However, recent large outbreaks of the disease in French Polynesia (in 2013) and Brazil (in 2015) have drastically heightened public awareness of the virus. In January, the CDC issued a level 2 alert for travel to Mexico, Central America, South America and the Caribbean due to Zika virus outbreaks, warning travelers to “practice enhanced precautions” and take steps to protect themselves from mosquito bites.
The Zika virus is mainly transmitted through the bite of the Aedes aegypti mosquito. The same species of mosquito is also responsible for transmitting other diseases, including dengue, chikungunya and yellow fever. Officials are concerned that the Zika virus is also on its way to becoming an endemic disease: a feature of the natural ecosystem, like those listed above. The disease becomes endemic when a sylvatic cycle is established; animals, such as apes, birds, horses, and other wildlife become carriers of the disease that continually transfer the pathogen to and from mosquitos. In that situation, the disease becomes impossible to eliminate by treating humans alone, since the wild animal population will be able to re-introduce the virus to mosquitos all over again.
The symptoms of the Zika virus are often relatively minor, consisting of things like a mild fever, skin rashes, conjunctivitis, muscle and joint pain, malaise or headache. The symptoms often last less than a week, and only one in five people infected will exhibit symptoms at all. But if the symptoms in adults are so mild, then why is there so much concern about an epidemic? This is due to increased levels of reported birth defects in Brazil that coincide with the beginning of the virus infection. These babies were born exhibiting microcephaly: they are born with unusually small heads. This condition is sometimes only aesthetic (in about 15% of cases), but usually it results in variety of problems, including developmental delays, intellectual deficits, or hearing loss. There is no treatment for microcephaly.
This increase in birth defects is suspected to be related to the outbreak of the Zika virus. Therefore, a woman who contracts the virus while pregnant may have a serious risk of birth defects in her child. Currently, the only defense against the virus is to prevent contact with the disease by taking steps to avoid mosquito bites when in infected areas. There is currently no treatment for the Zika virus.
The Zika virus is also suspected of increasing the occurrence of Guillain-Barré syndrome, a rare condition where a person’s immune system attacks their peripheral nerves. It is most commonly found in adults and males. Most cases of the disease include symptoms like muscle weakness and loss of feeling in the limbs, but severe cases can cause paralysis. However, symptoms usually only last for several weeks, and most people will see a full recovery even from severe cases of the illness.
There is no vaccine for the Zika virus at this time. Despite the discovery of the virus over 70 years ago, there are a lot of holes in our understanding of it. One of the issues is that testing for the virus itself can be tricky. Detecting it in blood samples can be difficult. The virus can only be found in the blood during the first five days of infection, but symptoms don’t usually manifest until four to five days after infection, so an infected person is unlikely to be tested until after the detection window is closed. A new DNA-based screening method exists in the United States, but only a small number of labs actually know how to use it, currently.
Scientists are seeking funding for research aimed at controlling the spread of the virus (along with other mosquito-borne diseases), as well as how to vaccinate against it or cure it. Containing the spread of the virus looks to be the most likely approach in the short-term. This week, Scientific American published an article about the World Health Organization’s Vector Control Advisory Group’s (VCAG) various approaches to curtail the spread of the Zika virus by controlling the mosquito populations. Three of the five techniques the group considered were determined too experimental to be deployed. The other two techniques potentially have promise. One approach is to release cultivated male mosquitos infected with Wolbachia bacteria. This bacteria (which has no effect on humans) causes the eggs of female mosquitos who mated with the infected males to fail to hatch. Another option is to release transgenic (i.e. genetically-modified) mosquitos that have been developed to generate offspring that die off before reaching adulthood. These methods could be effective in limiting the spread of the virus by suppressing the mosquito population.
So where do we go from here? More research is certainly required, and that is where we can lend a hand. Our Drosophila and Small Insect Chambers are great for applications involving mosquito rearing, such as studies on vector biology, vector-parasite interactions, insecticide susceptibility, vaccine studies, etc. Our chambers have a 15-60°C programmable temperature range, making them flexible for a multitude of applications. The Level 3 chambers are controlled by thermoelectric (Peltier) coolers and come equipped with ultrasonic humidity generators capable of providing up to 80% relative humidity. Programmable digital clock-controlled fluorescent lighting (LED lighting is available as an option) is also included on the Level 3 models for complete control over lighting conditions in the chamber. Since all of our chambers are custom-built, we can also provide additional doors or screening inside the chamber for added security against escaping mosquitos when opening the chamber door.
For more information on the Zika virus, check out the following links: