Sunday, April 4, 2010

Easter Infection


I had a difficult time deciding what to kick off my first blog entry with – there are so many viruses and parasites to choose from! Do I start with something basic and move onwards and upwards from there? Or do I jump right in with both feet and bombard my initial readers with my favorites?
But then I realized I should obviously go with a festive theme for Easter. I mean, that’s the logical thought, right?
Truth be told, the Easter bunny does become occasionally ill. Unfortunately, it’s usually with a brutally fatal virus: the myxoma virus.
The myxoma virus is part of the poxviridae family, and is a class 1 virus within Baltimore Classification Standards. The myxomoa virus has an exterior envelope structure which encases the viral capsid and assists with viral entry to the host’s cell. This envelope structure contains many important glycoproteins that assist with entry through membrane fusion and location specific phagocytosis. Later on in the viral lifecycle, or the “infectivity cycle”, the viral envelope also assists with budding from the host’s cell for dissemination of newly matured virions. For all viruses, the viral genome is protected within the viral capsid. The myxoma virus utilizes a double stranded DNA genome that is non-segmented and linear.
 
The myxoma virus only seems to infect rabbits and hares due to components of their immune system that are easy to evade. It is not necessarily exclusive to one geographic region, although does have a higher infectivity in specific areas. High incidence rates have been reported in the UK, Australia, Egypt, France and South American (specifically Uruguay).  The South American incidents are typically not dangerous and illustrate a lower mortality rate than any other region affected. Common cottontail rabbits usually experience characteristic dermal tumors, yet European rabbits can experience severe myxomatosis. 

Symptoms of myxomatosis begin with tumors on the skin and genital areas. After spreading, the rabbits can experience blindness, fever and exhaustion. Due to the rabbit’s weakened state, secondary bacterial infections are very common and are habitually what cause the onset of the eventual death. This is usually due to swelling of the lung tissues and pneumonia. Myxomatosis is also associated with Rabbit Hemorrhagic Disease (RHD) which can cause the infected rabbit to become comatose and die. Death from  a myxoma infection can occur anywhere between 48 hours to 14 days after initial infection. 

Australia’s government decided to utilize the fatality of the myxoma virus to control the overwhelming rabbit population. Initial experiments for population control “successfully” reduced the rabbit population from 600 million rabbits to 100 million rabbits over the course of two years. I can’t imagine what wading through rabbit carcasses decorated with tumors would be like. I mean, 500 million is a lot of dead rabbits. 

The virus is spread through direct contact with infected rabbits, and also through insects that take blood meals, such as mosquitoes.  It’s still a pretty rampant problem, thanks to governmental abuse for population control, and has lead to the development of a vaccine for those who wish to keep pet rabbits.
So, don’t be alarmed if the Easter Bunny didn’t quite make it through his rounds of delivering baskets. You might be the lucky one that finds a lumpy rabbit carcass amongst your chocolate eggs.

As far as festive parasitic infections go, Iodamoeba butschlii takes the egg-shaped cake.
Iodamoeba butschlii, as you can see from the name, is an amoebic parasite. It does infect humans, but is considered mostly non-pathogenic. Generally, these little buddies reside in your large intestines and feast on the excess yeast in your system. Rarely do people experience symptoms, but if they do, it’s generally just mild diarrhea and stomach cramps.

 The festivity is in the structure of the parasite, not necessarily the function (I mean, nothing says Happy Easter like mild diarrhea and stomach cramps!). Iodamoeba butschlii is one of the smaller parasites, with an average cyst size of 10 µm. It has all the normal components of an amoebic parasite, such as a nucleus, endosomes, etc., yet can be easily diagnosed because of its abnormally large glycogen vacuole! Why am I so excited about this glycogen vacuole, you wonder? Well, it is the key to our festive riddle!
Scientists, being the witty and intelligent creatures that they are, decided that this glycogen vacuole paired with the ovoid shape of the cyst makes Iodamoeba butschlii look like an EASTER BASKET! Take a look for yourself:

Don't you just want to put all your eggs in that little basket? An Iodamoeba butschlii infection can be diagnosed through a fecal wet mount. Exciting!

So with that, watch out for excess rabbit carcasses and avoid eating focally contaminated food this Easter.
Happy bunny day!

p.s.-  Radiohead's Myxomatosis:

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