Sunday, 6 January 2013

Science Sunday; Vaccines

Immunological memory
The immune system needs to remember the things it has had to fight off in the past in order to be able to treat them efficiently if the horse is reinfected. Some studies have shown that the memory of some viruses and diseases can last for over 75 years in humans. This is why vaccines work well as the animal will remember the infection and kill it more quickly next time it becomes infected. Vaccines stimulate a normal protective immune response of host to successfully fight invading pathogens.

Types of vaccine
There are a number of types of vaccine. These include a killed version of the bacteria/virus. It can be a live version that has been altered. They can be a section of protein or DNA taken from the bacteria/virus. They want the disease to still be recognisable to the immune system of the animal without still being able to cause harm. 

There are a number of reasons why some vaccines work and others don't. Some are toxic to the animal. Some need to be boosted as one injection will not provide lifelong treatment (although they should in theory).  A lot of knowledge into the disease is needed before they can start designing a vaccine. They need to understand it's life cycle to work out when is best to target the bacteria/virus. 


Vaccines when the foal is very young are questionable. The antibodies in the colostrum cause the offspring’s immune system not to make its own antibodies. The length of time the maternal immunity (passed on from the mother) lasts for is questionable and antibodies for different things may last different amounts of time. The mare should be given a tetanus vaccine during pregnancy as the horse is susceptible to tetanus and foals may be at risk. These antibodies will be passed onto the foal in the colostrum. However, if you are unsure if the mare has had the vaccine the foal should be vaccinated as it may have a benefit. The foal should start having vaccines around 6 months. 

There are some problems when developing vaccines for parasites as they hide from the animals immune system and can also suppress the immune system. Success with commercial parasitic vaccines has been seen in some animals. Some have a poor shelf life so have not worked well commercially. A vaccine for ticks and another for tapeworm in sheep were produced but are not produced now due to commercial reasons. 

Love Laura

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