Rocky Mountain spotted fever

The Rocky Mountain spotted fever (English Rocky Mountain spotted fever ) is the most common and most difficult runs caused by rickettsial disease in the United States. It occurs on the entire American continent. In other countries it is referred to as tick typhus or Tobia fever (Colombia ), São Paulo fever or febre maculosa (Brazil ) or fiebre manchada ( Mexico). Without rapid and targeted treatment, the Rocky Mountain spotted fever can be fatal.

Pathogen

The causative bacterium Rickettsia rickettsii is an obligate intracellular parasite. Transmission is by hard ticks of the genus Amblyomma and Dermacentor. In nature rickettsiae undergo a complex change of host between arthropods and mammals; man is an accidental host basically.

Epidemiology and dissemination

Since 1918, the cases in the U.S. are registered. In the last 50 years 250-1200 disease cases were reported annually. With high probability the actual number of cases is much higher. More than 90% of patients infected from April to August. In the majority of cases can elicit a previous tick bite.

The name of Rocky Mountain spotted fever is actually inappropriate, since it became clear since the 30s that affected areas were far outside of the Rocky Mountains as well. In the spread today the continental part of the United States, southern Canada, Mexico, and large parts of South America are included. Within the U.S., the states of North Carolina and Oklahoma are affected the most. In the states in the area of the Rocky Mountains, only about 3 % of the total cases occurred.

Symptoms

The incubation period is from a few days to two weeks. Initial symptoms are suddenly rising fever, headache, nausea with vomiting, muscle pain and rash. Diarrhea and abdominal pain may be added. In early stages, the disease is difficult to diagnose because the rash becomes visible only about six days after the first symptoms. This consists primarily of small, non-raised, purple, not itchy spots ( macules ) on wrists, ankles and forearms. Later, these lesions are slightly raised. The eponymous, typical red and spotty rash is observed only about every second patient. Pathophysiologically is petechiae, so widely scattered hemorrhages in the skin.

Complications can arise by manifestations in the lungs, kidneys, gastrointestinal tract and in the central nervous system.

Diagnosis

In addition to the clinical picture sometimes laboratory findings such as thrombocytopenia, hyponatremia and elevated liver enzymes can help.

Therapy

Treatment must already be started immediately suspected case. Effective antibiotics are doxycycline and chloramphenicol, the latter should be considered only as a reserve drug because of possible serious side effects. The treatment is continued for at least three days for the addition of fever.

Forecast

The Rocky Mountain spotted fever remains a dangerous and potentially life-threatening disease even today. Despite the availability of effective antidotes still die 3-5 % of patients. Nevertheless, the effective antibiotic therapy has significantly reduced the mortality rate. Before use, died almost one in three infected.

History

The first description dates back to 1896. Then on the disease occurred in the Snake River Valley ( Idaho) and was named because of the characteristic skin manifestations as the "black measles ". The dreaded and often fatal illness befell hundreds of people in the region. At the beginning of the 20th century, it expanded on areas between Washington and Montana in the north and California and Arizona in the south.

Howard Taylor Ricketts first identified the infectious organism that causes the disease. Along with other scientists, he managed to establish the basic epidemiological facts and to understand the role of ticks as vectors. Dr. Ricketts died tragically shortly after the publication of his studies in 1910 at another caused by rickettsial disease, spotted fever ( typhoid eng. ).

• Bacterial infectious disease of humans
• Zoonosis