Parasites

Coccidia vs. Macrophage

Enteric coccidiosis, the infestation of the small intestine by the Eimeria spp. parasites, is a common cause of diarrhoea and even death in rabbits.

Coccidiosis

Autolysed villus with a macrogametocyte (H&E x400)

 

There are loads of species of Eimeria.  If they cause disease they shrink the villi (finger-like projections in the intestine) by destroying the enterocytes (cells that line the villi).  This leads to poor absorption from the gut lumen, and also leakage of fluid into the lumen.  This results in diarrhoea.  Dehydration and electrolyte loss can prove fatal to the rabbit.

The immune system tries to get rid of the parasite.  Below we managed to capture the moment a team of macrophages have fused to form a giant cell, which is in the process of ingesting (by phagocytosis) a parasite oocyst.

Coccidiosis2

Giant cell (arrow) engulfing an oocyst

Standard
Parasites, What's this?

What’s this? #10 Bot fly larvae

Horse bot flies have a life cycle which is not very pleasant for the poor horse. The adult fly will lay her eggs on the hairs of the horse’s front-half (front legs, chest, shoulders and sides). After the first stage of the larvae has formed within the egg, the action of licking at the area by the horse prompts them to emerge. These larvae will then migrate to the mouth, or enter the mouth during licking, and embed themselves in the horse’s tongue. They sit in the soft tissues of the mouth for about a month before they moult into their second stage. They then crawl into the stomach and attach to the lining where they complete their growth and moulting into the third larval stage. They stay here for about a year, before detaching and passing out with the manure, where they will pupate and then hatch as adult flies a few weeks later…

When the stomach was opened the larvae crawled away and re-attached to the cut surface of the oeseophags!

When the stomach was opened the larvae crawled away and re-attached to the cut surface of the oesophagus!

Whilst they are migrating through the horse’s body they can cause irritation of the mouth and gastrointestinal tract. In large enough numbers they may even cause a blockage. Stomach ulcers, stomach rupture, oesophageal paralysis, and even tumours may result from the long standing infestation by these critters.

Rows of spines distinguish these as Bot fly larvae.  Well done to all those who guessed correctly!

Rows of spines distinguish these as Bot fly larvae. Well done to all those who guessed correctly!

Standard
Parasites, What's this?

What’s this? #10

Do you know what these creepy fellows are?  Bonus points if you know the species and organ they are found on…

Who are they and what are they eating?!

Who are they and what are they eating?!

Standard