Giemsa stain
"Neorickettsia helmintheoca" is the etiological agent for salmon poisoning disease, found to be present in all stages of the trematode. It is 0.3 micrometers in size and a purple Giemsa stain indicates that it is Gram negative. Thus far, only canids are susceptible to disease by rickettsia and it is still uncertain how the rickettsia leave the trematode vector and reaches the host tissues. Experiments do show that the bacteria lead to necrosis of lymph follicles, ulceration, and severe hemorrhage in its host.