Strong and his colleagues found in the blood of Oroya fever cases rod-shaped forms in the red cells, varying from 1 to 2 microns in length, the red cells containing from 1 to 30 of these elements.
A study of sections of lymphatic glands of severe fatal cases showed great numbers of these bodies packed in the endothelial cells. These cells rupture and set free the organisms.
Intravenous inoculation of blood containing these elements into monkeys and rabbits was negative in result. Strong failed to cultivate the organism. These organisms were considered as intermediate between bacteria and protozoa. They are closely related to Grahamella and the Harvard commission has proposed the name Bartonella bacilliformis. In many ways they resemble piroplasms, especially Theileria.
Pathology
At autopsy the skin shows the pale yellowish waxy hue of pernicious anaemia. The lymphatic glands are somewhat enlarged and may be oedematous. The heart is flabby and ecchymoses may be present in the pericardium. The spleen is enlarged, shows numerous infarctions and contains large amounts of pigment in the form of yellowish masses or granules deposited between the splenic cells and in the endothelial leucocytes. This pigment is like melanin in not giving the iron reaction. The liver likewise is enlarged, shows areas of toxic degeneration and contains moderate amounts of pigment. The femoral marrow is soft and dark red. Microscopically, the endothelial cells of the lymphatics distended with the causative organisms were particularly noted by Strong.
Symptomatology
The incubation period is about three weeks and the onset of the disease is marked by malaise and apathy, to be followed by a rapidly developing anaemia, of the pernicious anaemia type, with an irregular fever of a remittent character fluctuating between 100° and 102°F. and only exceptionally going up to 104°F., and pains in head, joints and bones. The tenderness over the bones is undoubtedly associated with the marked changes going on in the bone marrow and is particularly marked over the sternum.
The patient rapidly develops a very severe anaemia and death results in 20 to 40% of cases in two or three weeks. Delirium is often noted.
The spleen and the lymphatic glands are somewhat enlarged. Associated with the profound anaemia there may be oedema of legs and about joints and functional cardiac murmurs. The kidneys do not seem to be affected. There may be a diarrhoea in the later stages of the disease. There is no eruption in uncomplicated cases.
The most important findings in the disease are those in connection with the blood examination. The rod-shaped organisms, which are thought to be the cause of the disease, are somewhat difficult to observe in fresh blood preparations. They show definite motility within the red cells, particularly after warming the blood slide. The motion is a rather gliding one. In Romanowsky-stained preparations the 1 to 2 micron-long rods within the red cells may occur singly or in numbers of 4 or 5. V-shapes are frequently seen. The rod shows a bluish staining with a deep purplish-red chromatin-stained granule at one extremity. Rounded, oval or pear-shaped forms may also be seen.