Monday, 17 July 2006

Travel Vaccinations

In the spirit of taking medical science into my own hands, and with a holiday to India and the Philippines coming up, I thought I’d take a look into vaccinations.

A vaccination is the process of giving weakened or dead pathogens to a healthy person to give that person immunity against a related disease. A dose of the weakened infectious agent is called an immunogen. The immunogen primes the immune system in a process known as immunisation. When one or more immunogens are administered, this is known as a vaccination.

The vaccinations I needed for my travels were for Cholera, Hepatitis A, Hepatitis B and Typhoid.

To my surprise, thankfully a needle was not needed for the cholera vaccine. The vaccine is taken orally and does not taste too bad, and in further good news, protects against not only cholera, but also travellers’ diarrhoea. Cholera is an infection caused by the bacteria Vibrio Cholerae, that once having been ingested through contaminated water or food and in the intestine, the bacteria secretes a toxin that causes severe diarrhoea. It is most commonly found in Asia and South America, and is not seen as problem in more developed countries due to water treatment and chlorination. Travellers’ diarrhoea is caused by a variety of different bacteria, the most common being enterotoxigenic E. coli (ETEC).

In the cholera vaccine, the cholera bacterium is modified such that the toxin-producing part of the bacteria is non-functional. This means that when it is administered, the symptoms of cholera do not develop. This allows the body to make antibodies against the real cholera bacteria so that if the bacteria do get into the body, it is immediately attacked by the body’s defence system. As the cholera toxin is very similar to the toxin produced by ETEC, the body’s defences against cholera will also work against the ETEC toxin.

So whilst the vaccine against Cholera was reasonably painless, the Hepatitis vaccines came in the form of a needle. Hepatitis is a gastroenterological disease, often including inflammation of the liver. There are a number of causes of Hepatitis, and the two causes against which I was immunised were Hepatitis A and Hepatitis B.

Hepatitis A is virus transmitted through contaminated food. It causes an acute form of hepatitis, however the infected person’s immune system makes antibodies that confer immunity against future infection. People with Hepatitis A are advised to rest, stay hydrated and avoid alcohol. A vaccine, like the one I had, is available that will prevent infection from Hepatitis A for life. It has no chronic stage, and so is not as dangerous as Hepatitis B. Hepatitis B can cause both acute and chronic Hepatitis, and is spread through bodily fluids. One of the dangers of Hepatitis B is that the infection establishes itself in the DNA of the affected liver cells. This makes it hard to defeat once you’ve got it. The vaccine prevents infection from Hepatitis B for life. However, Hepatitis B infections result in up to 1.2 million deaths per year worldwide.

The fourth and final vaccination I needed was against Typhoid fever. Typhoid fever is an illness caused by the bacteria Salmonella Typhi and is transmitted by ingestion of food or water contaminated with faeces from an infected person. The bacteria then multiply in the blood stream and are absorbed into the digestive tract. Typhoid fever can be fatal, and adding to the danger is that it can be spread by flying insects that have dined on infected faeces. However, it is mostly spread through poor hygiene. Symptoms most often include a fever, chills, a slow heart rate, weakness, diarrhoea, headaches, muscle pain, lack of appetite, constipation and stomach pains. It is thought that a devastating plague of typhoid fever killed one third of the population of Athens, including their leader Pericles, in 430 BC.

And just to make this simple holiday seem a little more dangerous, I’m taking some antibiotics along just in case I come across malaria, an infectious disease that kills over 1 million people each year. And I thought travelling would be safe.

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