It might look like a beautiful flower, but this image of the week is more the stuff of nightmares! The picture above shows a dog tapeworm (Taenia pisiformis) taken using a light microscope. The image clearly shows the hooks of the tapeworm on its head (scolex), which it uses (along with four suckers) to attach to the small intestine of canids like dogs and foxes.
The image was taken by Spike Walker. The tapeworm was on a microscope slide, giving it a slightly squashed look. The muscle and other tissue of the tapeworm were stained red, but the hooks (made of chitin) don’t stain. Therefore, Spike used a contrast enhancement technique called Rheinberg illumination, which gives the hooks their bright colours against a blue background. First demonstrated over a hundred years ago by Julius Rheinberg, this involves using coloured filters so a transparent sample can be seen.
These tapeworms can grow up to two metres long, with a very simple nervous system and no digestive tract, absorbing nutrients directly through their outer layer. They are long and flat, made up of thousands of segments called proglottids. These proglottids contain a complete reproductive system and can contain thousands of eggs. When mature, the proglottid breaks off from the tapeworm and is excreted by the host in faeces. It then ruptures and releases its eggs to infect another animal.
When a rabbit eats grass contaminated with these eggs, the eggs hatch in the rabbit’s stomach to form ’6-hooked embryos’ which claw their way through the gut wall and develop into ‘larvae’ known as bladder-worms. Dogs become infected with Taenia pisiformis after eating rabbits that have been parasitized in this way.
Image credit: Spike Walker, Wellcome Images
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Filed under: Animal Health, Wellcome Images Tagged: Dog tapeworm, Spike Walker
