Mosquito and Virus Interaction

Scientist have discovered Dengue Fever to only occur as a result of specific interaction between mosquito and virus strains 

 

        http://en.wikipedia.org/wiki/File:Aedes_aegypti.jpg

           

     When the right strain of mosquito meets the right strain of Dengue a genetic interaction occurs between them and Dengue infection occurs. Researchers discovered that mosquitoes can be susceptible to a certain strain of the Dengue virus, and at the same time they can be resistant to another.  

      
     Although scientist suggest there are genetic interactions occurring between the mosquito and the virus, they have never been mapped onto the chromosome of the mosquito. Therefore understanding exactly where the genes are interacting is unknown. 

     What's next? 

      

      Scientists hope to determine the genetic factors in Aedes aegypti that lead to Dengue Fever by creating finer mapping of the mosquitoes chromosomes. They believe this research is crucial and it may be a the foundation for other studies to completely stop the mosquitoes from transmitting the virus.

      Possible areas for Dengue Fever management include interrupting the transmission of Dengue in the mosquito and interrupting the cycle of the disease in the human host. Scientists hope the information gained from further research into these areas may provide possible drug targets to control the disease. Researchers believe that it may be necessary to genetically modify Dengue resistant mosquitoes. Oppositions claim this theory may be dangerous. The jury is still out whether genetically modified Aedes aegypti is our strongest defense against Dengue Fever.




     http://www.dw.de/thai-french-genetic-investigation-of-dengue-fever-reveals-a-fussy-little-disease/a-17162657

     Halstead, S. B. (2008). Dengue virus-mosquito interactions. Annu. Rev. Entomol., 53, 273-291.

 

     Rosen, L., Roseboom, L. E., Gubler, D. J., Lien, J. C., & Chaniotis, B. N. (1985). Comparative susceptibility of mosquito species and strains to oral and parenteral infection with dengue and Japanese encephalitis viruses. The American journal of tropical medicine and hygiene, 34(3), 603.

Mosquitoes Evolving Resistance Against Dengue

As previously stated in my first post, there are currently no vaccines commercially available for Dengue Fever. So what is in the pipeline? 

Earlier this year a study was carried out on investigated the effects of the microsporoidan parasite Vavraia culicis on the female Aedes. aegypti mosquito. A series of experiments were created involving the female mosquito and its microsporoidian parasite to show how intra-specific competition and parasitism shape life history traits. Many of these life-history changes are thought to be down to reallocation or decrease in the host's resources either caused by the host to minimize the effects of infection or caused by the parasite to maximize its growth rate. Parasitic infection is often associated with changes in host life-history traits, such as host development.

http://onlinelibrary.wiley.com/doi/10.1111/eva.12144/full

Results showed Vavraia. culicis caused changes in the behaviour of the female Aedes. aegypti this is seen in the graphs above.Infected female mosquitoes were found to be less likely to take a blood meal in the first few days after Vavraia. culicis infection (shown in graph A). Females that did feed took smaller volumes of blood than uninfected females (Shown in graph B). Infected females were noted to produce 20% fewer eggs than uninfected female mosquitoes (Shown in graph C). It was also suggested the female mosquitoes could alter their life-history traits to bring forward their schedule of reproduction and The survival rates of the adult mosquitoes were reduced if infected with Vavraia. culicis.

Could this information be the breakthrough we have been looking for? Is this a possible future management strategy?

Sy, V. E., Agnew, P., Sidobre, C., & Michalakis, Y. (2014). Reduced survival and reproductive success generates selection pressure for the dengue mosquito Aedes aegypti to evolve resistance against infection by the microsporidian parasite Vavraia culicis. Evolutionary Applications.

Mosquitoes and Climate Change

       

      Evidence suggest average global temperatures will increase between approximately 1.5°C and 6°C by the end of this century. This rise in temperature may be beneficial for the spread of some infectious diseases. Global incidence of Dengue has increased in recent decades with climate change being a suspected cause. Dengue Fever is typically seen in the tropic and sub tropic climates. Changes in weather such as milder winter and warmer summers could lead to ecological changes in Dengue.     

  

   Female Aedes Spotted in Germany!

      

      Due to milder winters and moist air, mosquitoes are capable of surviving and  thriving in Germany. During a period of 8 weeks in 2011 two adult females of the Aedes genus were collected for the first time in June and August. Previously, only immature stages of the genus had been collected in Germany.   

      The table below shows the amount of mosquitoes that were trapped over the 8 week period;         

 

 

 http://www.eurosurveillance.org/images/dynamic/EE/V17N04/Werner_Tab.jpg

      

      Currently the mosquitoes survive for a limited time and die during the cold winter. However, due to global warming, it it thought the climate in Germany will on average become warmer and the winters shorter and the count of exotic mosquitoes will continue to increase. 

      Mosquitoes typically travel with a companion such as viruses. The further from their native tropic climates the mosquitoes can migrate, the further the virus can also. Thus the spread of infectious diseases such as dengue will spread further around the wold.  

    

       Werner, D., Kronefeld, M., Schaffner, F., & Kampen, H. (2012). Two invasive mosquito species, Aedes Albopictus and Aedes japonicus japonicus, trapped in south-west Germany, July to August 2011. Euro Surveill, 17 (4).

 

 

 

 

Prevalence of Dengue Fever

Cases of Dengue Fever have increased dramatically in the last 50 years. The graph below illustrates the rapid change in reported Dengue Fever cases; 

http://www.who.int/csr/disease/dengue/impact/en/

Now in 2014 who exactly is effected by the infectious disease? 

- Half of the population is now at risk of contracting dengue
- Dengue is endemic in more than 100 countries in Africa, the Americas, the  
  Eastern Mediterranean, South-east Asia and the Western Pacific
- Up to 100 million cases of Dengue Fever are reported per year
- Dengue is predominantly found in areas of overcrowding and major urban
   centers
- Leading cause of serious illness and death among children in some Asian and
   Latin American countries.     

What is Dengue Fever?

Dengue Fever

Dengue fever is a infectious tropical disease caused by the dengue virus. Dengue is transmitted by females of several species of mosquito within the genus Aedes, with Aedes. Aegypti being the most common vector. 

http://www3.nd.edu/~dseverso/genome.html



Dengue Transmission

 

 Dengue can not be transmitted from person to person. Transmission is at its highest early in the morning and late at night. Below is a simple diagram to illustrate the transmission process:

 

http://ilandvibez.com/5-plus-people-infected-with-dengue-fever-in-the-past-2-weeks-minister-of-public-health-shares-his-concerns/dengue-lifecycle-diagrams/#

 Symptoms 

Dengue fever has three phases. In phase one, infected individuals may experience flue like symptoms, sever headaches and aching in the joints and bone. Around a quarter of victims become very unwell and in a small proportion of cases it can be fatal. 

  

http://en.wikipedia.org/wiki/Dengue_fever

Management of Dengue 

Currently there are no vaccines or cures commercially available for Dengue Fever. Therefore preventing the spread of dengue is very important. The following methods are used to manage the spread;

1. Mosquito nets

http://kgraumann.blogspot.co.uk/2012/03/malaria-initiative-through-persuasive.html 

2. Fumigation 

  http://www.crainsnewyork.com/article/20100824/FREE/100829910/dengue-fever-in-tropics-sparks-nyc-travel-advisory#

 3. Insect repellent 

http://health.howstuffworks.com/skin-care/information/health-factors/insect-repellent-and-sunscreen.htm

4. Avoid stagnant water

http://www.dw.de/thai-french-genetic-investigation-of-dengue-fever-reveals-a-fussy-little-disease/a-17162657