Animal Blog Post: Tularemia and Rocky Mountain Spotted Fever

Dermacentor Variabilis

“The American Dog Tick”

Introduction:

The American Dog Tick is an arthropod that is a carrier of two toxins, Tularemia (Francisella tularensis) and Rocky Mountain Spotted Fever (Rickettsia rickettsii). This species is known to feed primarily in the spring and summer seasons. There is a significant increase in epidemiological cases of both toxins within these two seasons, with the female being the dominant feeder. Click here to see the region where the American Dog Tick is located and more literature.

Toxicokinetics: 

Tularemia and Rocky Mountain Spotted Fever.

Tularemia (Francisella tularensis)

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Tularemia (Francisella tularensis), is a highly infectious bacterium that is transmitted through the saliva of a tick and continues its lifecycle through the host. An individual can contract the bacterium as an aerosol if inhaled and through physical contact. Due to this method of contracting the bacterium it has been labeled as a possible biowarfare toxin. 

Mechanism of Action:

The bacterium acts on cellular components of targets organs cellular physiology for proliferation. Disrupting cell signaling inadvertently reducing a mitochondrial inflammatory response . Little is known about the genetic factors of F. tularensis, but it is documented that by infecting macrophages it impairs phagocytosis which in turn increases its own survival rate. 

Target Organs:

  • Lungs
  • Lymph Nodes
  • Kidney
  • Spleen
  • Liver
  • Pleura

Signs & Symptoms:

  • Frequent exhaustion
  • Headache
  • Skin sores
  • Fever
  • Excessive sleep
  • Swollen lymph nodes
  • Pharyngitis

Carcinogenicity:

There are no known carcinogenic effects documented to date.

Treatment:

Antibiotics such as, ciprofloxacin, gentamicin, streptomycin, doxycycline. Duration of treatment is typically 10-21 days.

Rocky Mountain Spotted Fever (Rickettsia rickettsii)

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Rocky Mountain Spotted Fever (Rickettsia rickettsii), is a bacterial disease that is transmitted by the American Dog Tick. Rickettsia preferentially infects the vascular endothelial cells lining small and medium vessels throughout the body, causing the systemic symptoms and high mortality occurs with Rocky Mountain spotted fever. The infection of endothelial cells leads to disseminated inflammation, loss of barrier function, and altered vascular permeability throughout the body (Snowden, 2020). 

Mechanism of Action:

Rickettsia rickettsii, infects endothelial cells and vascular linings. This bacterium has a low level of virulence which acts a means to coincide with host and prolong survival. 

Target Organs:

  • Heart
  • Kidney
  • Lung
  • Cortex-meninges (meningitis)

Signs & Symptoms:

  • Vomiting
  • Headache
  • Rash
  • Fever
  • Excessive sleep
  • Muscle aches
  • Paralysis (chronic)
  • Loss of hearing (chronic)
  • Cognitive deficits (chronic)

Carcinogenicity:

There are no known carcinogenic effects documented to date.

Treatment:

Doxycycline is an antibiotic that is the first choice of treatment. Chloramphenicol, also an antibiotic can be used in early development of the disease. Duration of treatment is typically 10-15 days.

References:

  1. CDC Tularemia. (2018, April 04). Retrieved July 26, 2020, from https://emergency.cdc.gov/agent/tularemia/tularemia-biological-weapon-abstract.asp 
  2. Francisella Tularensis (Tularemia). (n.d.). Retrieved July 26, 2020, from https://www.centerforhealthsecurity.org/our-work/publications/francisella-tularensis-fact-sheet
  3. Snowden J, Simonsen KA. Rickettsia Rickettsiae (Rocky Mountain Spotted Fever) [Updated 2020 Apr 14]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430881/
  4. Tick ID. (2019, January 10). Retrieved July 26, 2020, from https://www.cdc.gov/ticks/tickbornediseases/tickID.html