Rickettsial pox: causes, symptoms, diagnosis, treatment, prognosis, and prevention

Rickettsial pox, also known as Kew Gardens spotted fever, is a febrile, self-limiting disease characterized by fever, headache, back pain, and generalized papules and vesicles, caused by rickettsia akari transmitted by mites, resembling varicella clinically.


Causes

The pathogen is rickettsia akari, and the vectors are mites distributed all over the world who infect domestic mice and wild rats. Humans are infected mainly by bites of chigger mites or adult mites.

Pathogenesis

After mite bites, the pathogens invade the human body and replicate in the local lymph nodes and mononuclear phagocyte system, causing rickettsemia, damaging small blood vessels and capillaries.


Signs and Symptoms

The incubation period is 7 - 14 days.

A 5 - 15 mm in diameter, solid papule occurs at the bite site, developing into a round or oval blister, drying and incrusting eventually, with regional lymphadenopathy. In several days, patient present with flu-like symptoms, including fever, chills, sweating, headache, and back pain, usually lasting for 4 - 5 days.

During systemic symptoms, rashes spread throughout the whole body, including the mouth, but palms and soles are not involved. Skin lesions are mainly papules or papulovesicles, surrounded by vesicles, resembling varicella. The condition is generally mild and self-limiting, and usually heals within 2 weeks. Systemic lymphadenopathy and splenomegaly may occur in very few patients.


Diagnosis

The clinical manifestations are similar to those of varicella. However, vesicles of the disease occur on the base of papules and appear simultaneously, whereas vesicles in varicella occur one after another in groups. The number of vesicles of the disease is less than that of varicella. There is a primary lesion at the bite site before eruption. On the basis of these characteristics, the disease can be differentiated from varicella.


Treatment

The disease is self-limiting, and the prognosis is good even without medication. Medications are the same as those of other rickettsial diseases. Tetracyclines and doxycycline can shorten fever duration and promote healing. There is no relapse after recovery.


Prognosis

The disease is self-limiting, and good prognosis is present.


Prevention

Rats and mites should be eliminated.