Cat flea rickettsiosis
The majority of human infections by R. felis are subclinical. If symptomatic, fever and headache are typically followed by a pruritic eruption on the chest, abdomen, and lower extremities after 3-5 days. Additional symptoms, such as myalgia, arthralgia, abdominal pain, cough, and chest pain, may accompany. An eschar can develop at the site of the flea bite.
Cat flea rickettsiosis is considered an emerging and underreported infectious disease. Diagnosis is challenging as its clinical presentation resembles that of other rickettsial diseases and there is cross-reactivity in serological tests. Cat flea rickettsiosis appears to be a milder disease compared with other rickettsial diseases. However, reports of systemic complications, with photophobia, hearing loss, meningismus, alveolar hemorrhage and hepatosplenomegaly, have occurred.
A75.9 – Typhus fever, unspecified
416623000 – Cat flea typhus
- Endemic typhus – Caused by the flea-borne Rickettsia typhi. Similar to cat flea rickettsiosis, patients also develop fever and headache with additional systemic symptoms including cough, nausea, vomiting, myalgias, and arthralgias, followed by rash. Severe pulmonary, neurological, gastrointestinal symptoms, and laboratory abnormalities, including leucopenia / leukocytosis, anemia, thrombocytopenia, transaminitis, hyponatremia, and hypoalbuminemia, may ensue. However, in endemic typhus, there is no eschar. Polymerase chain reaction (PCR) may be used to differentiate R. typhi from R. felis infection. Rickettsia typhi and R. felis co-infections can occur, and doxycycline treats both.
- Epidemic typhus – Caused by Rickettsia prowazekii, which is transmitted to humans by the body louse with the southern flying squirrel as an animal reservoir. Similar to cat flea rickettsiosis, there is fever and headache with additional systemic symptoms including chills, myalgias, prostration, and cough, followed by a rash 4-5 days afterward. The disease can be life-threatening, with central nervous system, renal, gastrointestinal, and cardiac involvement. As opposed to cat flea rickettsiosis, there is no eschar.
- Scrub typhus – Caused by Orientia tsutsugamushi, which is transmitted from rodents to humans by larval mites (trombiculidae). Presents with a black eschar at the bite site after an incubation period of 6-18 days, with accompanying systemic symptoms including regional lymphadenopathy, cough, headache, fever, chills, and myalgias. A diffuse rash may develop. Severe systemic complications such as multiorgan failure, acute respiratory distress syndrome, meningoencephalitis, cranial neuropathies, and/or myocarditis may be seen. Unlike cat flea rickettsiosis, which is seen globally, this condition is endemic to Asian countries.
- Rickettsialpox – Caused by Rickettsia akari, transmitted by the house mouse mite. An eschar occurs at the site of the bite followed by the appearance of scattered papulovesicles. Patients have a low-grade fever and headache.
- African tick bite fever – Caused by Rickettsia africae. An eschar and low-grade fever are present. No exanthema is seen. Seen in sub-Saharan Africa.