Rocky Mountain spotted fever (RMSF): Nursing

Rocky Mountain spotted fever is a tick-borne, infectious disease caused by the bacteria Rickettsia rickettsii, which are endemic in the Midwestern, Northeastern. and south Atlantic and south-central regions of the United States. The organism primarily attacks the endothelial cells lining the inside of small blood vessels causing small vessel vasculitis, or inflammation of small blood vessels. If not treated promptly, the disease can be fatal.

Alright, first let’s quickly review some physiology. The endothelium consists of a single layer of endothelial cells that line the inside of the entire circulatory system, from the heart to the smallest blood vessels supplying the various organ systems. In addition to being a protective barrier, the endothelium plays a major role in the regulation of the vascular tone by releasing vasoconstrictive and vasodilatory substances, while it is also an important regulator of inflammation.

During an inflammatory response, the endothelial cells contribute to the release of small proteins, called cytokines, and other proinflammatory molecules that help modulate the activity of other immune cells, as well as promote the adhesion of immune cells, called leukocytes, to the endothelium, thereby facilitating their migration to the site of inflammation. Finally, the endothelium also helps to regulate blood flow, platelet aggregation, and blood clotting.

Okay, now Rocky Mountain spotted fever is caused by the obligate intracellular, Gram negative bacterium Rickettsia rickettsii. The infection is transmitted to humans through vectors primarily through the bite of an infected tick, like Dermacentor variabilis, or the American dog tick, which can be found in Eastern and South-central US; Dermacentor andersoni, or the Rocky Mountain wood tick, which can be found west of Mississippi River; and Rhipicephalus sanguineus, or the common brown dog tick, which can be found in Southwestern US.

Now, the infection is more common during the active tick season, which lasts from May to September, but can occur anytime during the year in places where the weather is warm. Since ticks like to live in warm, humid environments, they are usually found in forested areas with wood, bushes, and tall grass. Risk factors for this disease include living in endemic areas or traveling there, especially during spring and summer; living near wooded areas or areas with high grass; and frequent exposure to dogs.

Alright, after entering the body through the bite of an infected tick, Rickettsia rickettsii spreads through the body via the blood and attaches to endothelial cells lining the inside of small blood vessels. Rickettsiae then invade endothelial cells, replicate inside them, and spread from cell to cell causing endothelial cell injury. Now, an important consequence of endothelial cell injury is increased vascular permeability, meaning that the small blood vessels dilate and become more permeable, allowing plasma proteins, such as albumin, and fluid to leak from the vessel lumen into the interstitial tissue. This results in edema, or expansion of the interstitial fluid volume; hypovolemia, that can lead to hypotension, and hypoalbuminemia, or reduced levels of albumin in the blood.