Category Archives: Rickettsia rickettsii

Ticks and Fleas: fortune tellers of the tropics — Amber’s Pick

Editor’s Pick by Amber for the JIDC October Issue.  Thanks Amber!

Alyson

Tick-borne diseases are a hallmark of tropical weather. One can come across pathogen laden ticks not only in the rainforest but even in kitchens, gardens, backyard compounds or on domestic animals.  These common pathogen reservoirs which can accelerate disease spread at the community level.  The end result of the spread of tick-borne diseases may be many casualties. While several tick-borne viral, protozoal and bacterial infections are known, Rickettsial diseases are thought of as the worst human rival due to its deadly outcome, which even Dr. Howard T. Riketts (the researcher credited with the discovery of Rickettsial disease) and several other investigators succumbed to in nineteenth century. Since then, the rivalry goes on…..  

Figure 1D Immunohistochemical staining of spotted fever group rickettsial antigens

 

In an article published this month in JIDC, Tribaldos et al. report the case fatalities in a family cluster of Rocky Mountain spotted fever (RMSF) in Panama. RMSF is a systemic infection caused by Rickettsia rickettsii, the Gram-negative bacterium which is transferred to humans by the bite of infected ticks that feed on domestic pets, rodents, reptiles, birds and medium or large mammals. The organism infects the endothelial lining of blood vessels resulting in vascular damage, fluid loss, and poor circulation and bleeding in vital organs, leading to death. The disease is often misdiagnosed at the initial stages due to unavailability of specialized diagnostic procedures in routine settings, especially in developing countries. This article describes the clinical presentation, the presence of the Escher lesion, and the PCR based diagnosis of Rickettsia from the autopsies of three patients who belonged to the same household. Sequence analysis and restriction fragment profiling of ompA gene and immunostaining of Rickettsial antigens further describe the disease pattern.

Figure 1c RFLP analysis of ompA

In Panama, RMSF was prevalent in the latter half of the 20th century, but very few cases with 100% mortality were observed in the last decade. Moreover, in recent years, global literature has reported an increase in RMSF cases in other Latin American countries as well as in the southeastern United States, indicating the resurgence of this disease in the neotropics.

In the current scenario, I believe that the report by Tribaldos et al. significantly contributes to a better understanding of the clinical picture of RMSF which can help save lives if a diagnosis can be made faster. 

-Amber

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