In epidemiology, infections that spread at the expense of their host, harming or even killing it in the process. Are said to be virulent.

The most virulent stage of an infection usually corresponds to the period of greatest transmissibility, for obvious reasons — it does the pathogen no good to risk killing off its host unless doing so helps it spread to other hosts. Conversely, if the host is about to die anyway, it becomes essential for the infection to spread itself to new hosts, or it will also die when the host does.

Alas, the word “virulent” won’t fit your example sentence as written, since it calls for a noun phrase rather than an adjective. Does a virulent parasite bursting out of its dying host have a real meaning?