Dogs are dirty, dirty animals. I know because I’ve had several, which currently includes a mud-loving, cockroach-catching, drooly mess of a boxer who enjoys nothing more than sleeping her way over every soft surface in my house. The fact that dogs also transmit diseases, and an incredible variety of them at that, does not help matters! Parasites, viruses, bacterial and fungal infections! To their owners! To me, maybe you, maybe your friends! Your relationship with your pet is, in short, a lot richer than you could ever imagine. In light of this, I have a real doozy of a story about the relationship between pet dogs and a miserable little parasite set in the barren desert of northwest Kenya.
First, the parasite. Echinococcus granulosus is the causative agent of hydatid disease, a real nasty piece of work that usually plagues dogs and the ruminants they herd or hunt. Hydatid disease typically follows a dog-sheep-dog pattern, cycling through its intermediate host, the sheep, with the ultimate destination in its definite host, the dog. Dogs eat infected viscera, become infected with thousands of tiny tapeworms, shed the tapeworm eggs in their feces, sheep consume the eggs and the band plays on.
The life cycle of E. granulosus. Image: CDC. Click for source.
E. granulosus is ugly business for intermediate hosts and those poor souls who have inadvertently consumed the eggs. Following ingestion of the eggs, the larva bursts free from its shell, penetrates the intestinal wall and speeds it way to the liver, lungs, spleen and a few other choice organs. The disease manifests slowly, with bubble-like cysts sprouting from these organs. It’s horrific. At this point, this infection is termed hydatid disease. One of the most striking experiences of my parasitological studies was seeing an image of a dissected echinococcosis-infected rat with its entire body cavity filled with spherical pink cysts. It looked like an overflowing bubble bath. In my opinion, hydatid disease is the ne plus ultra of gruesome parasitic diseases.
