Tick- and flea-borne rickettsial emerging zoonoses

Abstract

- Between 1984 and2004, nine more species or subspecies of spotted fever rickettsiae were identified as emerging agents of tick-borne rickettsioses throughout the world. Six of these species had first been isolated from ticks and later found to be pathogenic to humans. The most recent example is Rickettsia parkeri, recognized as a human pathogen more than 60 years after its initial isolation from ticks. A new spotted fever rickettsia, R. felis was also found to be associated with fleas and to be a human pathogen. Similarly, bacteria within the family Anaplasmataceae have been considered to be of veterinary importance only, yet three species have been implicated in human diseases in recent years, including Ehrlichia chaffeensis, the agent of human monocytic ehrlichiosis, Anaplasma phagocytophilum, the agent of human anaplasmosis (formerly known as "human granulocytic ehrlichiosis agent", E. equi and E. phagocytophila), and finally Ehrlichia ewingii, which causes granulocytic ehrlichiosis in humans. We present here an overview of the various tick-and flea-borne rickettsial zoonoses described in the last 20 years, focusing on the ecological, epidemiological and clinical aspects.

Rickettsia infection in five areas of the state of São Paulo, Brazil

“…However, these authors did not find correlation between seropositive opossums and R. felis-infected fleas collected on these opossums. After its first report infecting C. felis felis fleas in the USA (Adams et al 1990), R. felis has turned to be a cosmopolitan species infecting mostly C. felis fleas (Parola et al 2005a). The contrast of few reported human cases of R. felis-spotted fever with the cosmopolitan distribution of R. felis-infected fleas deserves further investigations.…”

“…Unlike the above two Rickettsia species, which are vectored by ticks, R. felis is possibly carried by fleas especially Ctenocephalides spp. (Parola et al 2005a).There have been two reports of isolation of R. rickettsii from opossums (Didelphis spp.) from the states of São Paulo and Minas Gerais, Brazil (Moreira & Magalhães 1935, Travassos 1937 …”

“…Unlike the above two Rickettsia species, which are vectored by ticks, R. felis is possibly carried by fleas especially Ctenocephalides spp. (Parola et al 2005a).…”

Spotted fever group Rickettsia infecting ticks (Acari: Ixodidae) in the state of Santa Catarina, Brazil

“…From 1990 confirmed cases of Brazilian spotted fever were reported in these southeastern states; the fatality rates varied from 20-33% among the four states (data available from the Brazilian Ministry of Health site: saude.gov.br). Because most of these cases were diagnosed solely using serological assays employing R. rickettsii antigens and because serological crossreactions between all members of the SFG are known to occur (Philip et al 1978, Parola et al 2005, technically these cases could have been caused by any SFG species. Therefore, these cases cannot be considered confirmed cases of R. rickettsii infection.…”

Isolation of Rickettsia rhipicephali and Rickettsia bellii from Haemaphysalis juxtakochi Ticks in the State of São Paulo, Brazil

“…are intracellular bacteria in obligatory association with eukaryotic cells. They are associated primarily with invertebrates (ticks, mites, insects, and leeches), but some species are also capable of infecting and causing disease in humans, animals, or plants (9,21,30). Rickettsia spp.…”