A bacteria called Yersinia pestis which was carried by rats and the fleas that lived on them
the fleas where the start whom travelled from china, they had a bacteria in them which the fleas where immune to this bacteria was called versinnia. when the fleas bit the rats (black rat's ) drink the blood they would vomit out that bacteria that the rat wasn't immune to... soon the rat would die. after the fleas wiped out all the black rats they had no food so they moved onto the the humans and animals! so technically it wasn't the fleas who caused the plague it was the bacteria versinnia
rickettsia
Fleas on a rabbit are just called fleas, and a rabbit with fleas is just called a rabbit with fleas. If your rabbit has fleas, the safest way to treat it is to take the rabbit to a vet.
The infected fleas that spread the disease, The rats that carried the fleas, The ships that carried the rats from port to port. The Bacteria (Yersinia pestis), that infected the fleas.
Your answer is in the question. Fleas are not deadly, so spread beyond the death of the organism they infect. Deadly bacteria die with their host.
The Black Death was occured by bacteria that was disturded so then past on to fleas then the rats then the fleas and when the infected fleas bit a human it was all over for the infected person.
There were several reason that this disease was spread from person to person. People at this time had no idea that bacteria even existed. The cites were so very dirty. People would throw their "slops" into the street (feces and urine), there were no sewer systems. This disease was really due to the bite of fleas. The fleas were carried by rats from place to place. The saliva of the fleas had the bacteria. At times the bacteria got into the lungs of the person and this produced something called pneumonic plague. A cough would spread this even faster and further.
The Vorticella's diet is mainly of bacteria. It could eat other things, but it is mainly bacteria.
There are two species of fleas that are associated primarily with rats and mice: the northern rat flea (Nosopsyllus fasciatus), and the Oriental rat flea (Xenopsylla cheopis).It has been widely speculated that rats, carrying Oriental rat fleas infected with a bacteria called Yersinia pestis (which can infect humans with bubonic plague), were responsible for the Black Death plague epidemic.
Tapeworms, fleas, leeches, and most viruses, and some bacteria all fall under the label of parasites. Parasites benefit from another organism at that organism's expense.
Black Death was caused by fleas. They carried Yersinia pestis bacterium.