Bartonellosis (Oroya fever or Carrion’s disease) is caused by the rickettsial organism Bartonella bacilliformis and occurs only in Andean mountain regions of South America. The vector is the sandfly Phlebotomus (species). The organism is related to Rochalimaea quintana, the rickettsial etiology of trench fever and therefore is also related to Rochalimaea henselae, one of the etiologies of cat scratch fever.

Q fever is a rickettsial disease whose etiology is Coxiella burnetii. Goats and cows are the major vectors; infection occurs through exposure to contaminated milk or animal placentas, or may occur by inhalation of infected material. The organism is very resistant to drying, so that dust inhalation can spread the disease in dry areas. The incubation period is 2-4 weeks. Clinical disease is similar to moderately severe influenza. Infection usually (not always) does not produce a rash, which is unusual among the rickettsiae. Liver function tests are abnormal in 80% of patients, but only to a small degree. Diagnosis is usually by immunofluorescent serologic tests, generally performed in large reference laboratories or public health laboratories. The Weil-Felix test panel is nonreactive.

Ehrlichiosis is a rickettsial disease caused by Ehrlichia chaffeensis. The disease is spread by a tick vector and is clinically similar to Rocky Mountain Spotted Fever, except that only about 20% of patients develop a rash. Over half of Ehrlichiosis patients develop some degree of leukopenia (74%-85%) or thrombocytopenia (72%-84%), and mild aminotransferase enzyme level elevations (78%-100%) are common. Usually the disease is not severe. About one third of patients have symptoms that raise the question of CNS involvement. CSF shows elevated WBC count in 67%-71% of cases, with lymphocytes predominating in one third of cases. Total protein is elevated in 33%-62% of cases. There is also a canine Ehrlichiosis caused by a related but not identical tick-borne Rickettsia. In fact, for several years the usual diagnostic test for human Ehrlichiosis was an immunofluorescent test based on cross-reaction with canine Ehrlichiosis organisms. Now indirect immunofluorescent assays (IFA) are available that are specific for E. chaffeensis and that are being done in some large reference laboratories or public health laboratories. Acute and convalescent serum specimens may be required to document active or recent infection (vs. old infection).