Bacteria Genomes - NEORICKETTSIA SENNETSU

Neorickettsia sennetsu (formerly Ehrlichia sennetsu) causes Sennetsu ehrlichiosis, an infectious mononucleosis-like disease. N. sennetsu are gram negative, nonmotile, obligate intracellular coccobacilli.

Although the mode of transmission of N. sennetsu is still unproven, N. sennetsu is genetically and antigenically closely related to known trematode-borne agents. Therefore, the trematode (flatworm) is considered to be the reservoir and vector. Transmission has also been associated with the consumption of raw or under-cooked gray mullet fish which is often infected with the metacercaria (The encysted maturing stage of a trematode in its intermediate host prior to transfer to the definitive host, usually representing the organism's infectious stage.)

N. sennetsu was first documented in Japan in 1954 under its previous name of E. sennetsu and has since been reported mainly in Japan and Malaysia, but it may exist in other parts of Asia.

Sennetsu fever is a relatively mild infection that resembles infectious mononucleosis. It has an incubation period of 14 days and is characterized by fever, malaise, anorexia, lymphadenopathy and hepatosplenomegaly. Fatigue, chills, headache, backache and myalgias have also been reported. Increased circulating mononuclear cells and atypical lymphocytes are often found. A rash is rare, but generalised erythematous reactions or localised petechiae have been described. Deaths have not been reported.

For many years, Sennetsu fever was the only form of ehrlichiosis known to afflict humans. Comparative studies of emerging Human Ehrlichiosis Agents, Anaplasma (formerly Ehrlichia) phagocytophilum, Ehrlichia chaffeensis, and Neorickettsia (formerly Ehrlichia) sennetsu will enhance the opportunities for investigation of virulence factors, pathogenesis, immune modulation, and novel targets for antimicrobial therapy and vaccines.

References:

http://riki-lb1.vet.ohio-state.edu/ehrlichia/background/ehrlichiosis.php
www.cfsph.iastate.edu/Factsheets/pdfs/ehrlichiosis.pdf
http://pathology5.pathology.jhmi.edu/micro/v15n11.htm