Chikungunya Virus in Italy: Case Closed

EuroSurveillance.org released an interesting report of the cases of Chikungunya Virus in Italy. The outbreak appears to be over, due to the change in weather. The outbreak, which was centered in the Ravenna province in north-eastern Italy, has not had a reported case since September 28, 2007. Of the suspected 334 cases of Chikungunya virus, 204 were confirmed by lab results.

Chikungunya virus is a common illness, spread by mosquito bite (Aedes Albopictus species), and found in tropical countries. The initial source of this particular outbreak in Italy is believed to be a traveler from India, who imported the virus. Chikungunya is generally a self-limited infection that causes influenza like symptoms such as fever, muscular aches and fatigue.

There are several important learning points, from this outbreak. A virus that has previously never been a problem in Europe, can now run rampant. This underscores the ease of transmission, with a traveler being infected in India, only to continue to spread that tropical illness at their new destination. Several things had to be in place for this to occur. First, there needs to be a suitable vector, to carry the disease. The vector in the Chikungunya Italy outbreak was the Aedes mosquito.

The presence of this unique mosquito species in Italy has multiple causes but climate change is one of the leading ideas. http://woodshedenvironment.wordpress.com/ is a very good blog that addresses some of these factors. The blog centers on the fight against Dengue fever (another mosquito spread virus) in the Carribean. However, the author clearly addresses the factors of mosquito spread and the role of the vector in transmission.

Lastly, the change in the weather, from summer to winter, has effectively killed all the mosquitoes. No mosquitoes, no disease spread. If a person has the virus and is bitten by a mosquito, the mosquito carries the virus until it bites another person. This is how the virus spreads quickly and is difficult to control. For some tips on controlling mosquito bites and basic protection: https://adventuredoc.wordpress.com/2007/11/06/mosquito-bite-prevention/

Adventure Doc

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7 Responses

  1. That is the one good thing about “Climate Change” 🙂 eh Doc, that cooler temps can halt transmission of a mosquito-borne disease. This, however, is not a luxury that we have in places like ours where it remains sunshiny, for the most part, all year round.

    At least, the vector and epidemiology guys out there in Ravenna, Italy can rest easy for some months to come and gear up for the summer of ’08. For us here in the Caribbean, cool means high 70’s, which is not cold enough that we can afford to take a break.

  2. Very true, Israel! A few months break in the vector cycle can provide some much needed time to get a control program ready for the summer months.

    With your climate, in the Carribean, do you see a drop in the number of cases, during winter months? From what I understand, you either have all the mosquitoes or nothing? Meaning that if there is good breeding weather, for the mosquitoes :), there will be lots. If the temperature drops, all the mosquitoes die off. Is this correct?

  3. Actually, the temperature in these parts is always right for mosquito breeding. Therefore, the main variables that we measure and which make a difference are rainfall and sanitation.

    The only time of the year when there is usually a marked drop in mosquito breeding is within the first two quarters of the year when it is relatively dry. Consequently, breeding will become less prolific.

    However, poor sanitary conditions are such that the “Potential Containers” (containers used to catch water for household use or those that are disposed of indiscriminately) that are left unprotected out in the open allow fertile females to lay their eggs in the meantime so that when the rainy season returns, these eggs hatch and the infestations intensify.

    In summary, amount of rainfall and sanitation determine mosquito breeding and density in the Caribbean; in colder climes with torrid summers, temperature and rainfall would be the prime determining factors.

  4. What’s up with this man? A new template? Is this part of the grand scheme for 2008? Cool!

    But seriously, I was moved to re-read the above entry and it brought into focus the fact that the Cayman Islands is now banking on the upcoming dry season in January to reduce mosquito density. They are hopeful that decreased rainfall will stunt the potential for returning vacationers to initiate as yet unproven local transmission.

    In much the same way, the changing weather in Europe has saved the Italians, at least for now, from any problems with Chikungunya.

    The next question is whether the Aedes albopictus mosquito can facilitate transovarial transmission of the Chikungunya virus as it would the Dengue virus. You know of course that the reason why the spread of albopictus was feared so much in the 1980’s was because of its efficacy in passing on the Dengue virus via its eggs.

    This thought just came to mind thus I have not researched it/ But I was wondering if you have any information at your fingertips on this question.

  5. I am glad you like the new layout…Thanks! As for the Aedes-egg-chikungunya transmission question: One of the benefits of having to work on New Year’s Day is access to the library and journals. I will do some research tomorrow and gather a bit of information for you. Great question and I really should know more about this. Thanks for the motivation to do a little digging!

  6. Dated but interesting abstract looking at a lessen known species of Aedes Mediovittatus that has confirmed vertical transmission in the Caribbean (yikes!)
    http://www.ajtmh.org/cgi/content/abstract/39/2/218

    Abstract from study in Oaxaca, Mexico that showed viral genome of Dengue was vertically transmitted (aedes aegypti), but not actual live virus transmission:
    http://content.karger.com/produktedb/produkte.asp?typ=fulltext&file=000107272

    A great article and the most concerning: (Full text)
    http://www.searo.who.int/LinkFiles/Dengue_Bulletins_Volumes_29_(2005)_CHAPTER13.pdf
    “Transovarial Transmission of Dengue Virus in
    Aedes aegypti and Aedes albopictus in Relation to
    Dengue Outbreak in an Urban Area in Malaysia”

    Lastly, an intersting article abstract that looks at Aedes mosquito parasites (Ascogregarina culicis and Ascogregarina taiwanensis) that DO carry chikungunya virus and contribute to vert. transmission.
    http://cat.inist.fr/?aModele=afficheN&cpsidt=15160458

    My overall feeling is that there is definite vertical transmission of dengue and chikungunya in Aedes species. It appears to be geographically dependent, suggesting that there is a genetic mutation required. This is the same story as Reunion Island and Italy have seen. A genetic mutation in local Aedes species allows vertical transmission of the virus, either dengue or chikungunya.

    A few people on my end are now interested in how you could go about setting up a study to look at the possibility of vertical transmission in the Caribbean. Happy New year too!

  7. […] visceral form (most severe). Given the recent increase in vector borne illnesses in Europe, such as Chikungunya virus in Italy, this parasite needs to be recognized as an “up and coming” issue in […]

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