| Summary Information |
| Diseases / List of Bacterial Diseases
/ Disease summary |
| Alternative Names |
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| Disease Agents |
- A rickettsial organism distinct from Neorickettsia helminthoeca (the causative agent of salmon poisoning)
(J13.34.w3, J13.34.w4)
- Differentiated from Neorickettsia helminthoeca based on mutual lack of
conferred immunity between the two diseases (J13.34.w4,
J13.34.w5) and by direct fluorescent antibody techniques (lack of major cross reaction).
(J13.34.w5)
- The rickettsia infect a trematode, Nanaophyetus salmonica, which uses fish such as trout and salmon as an intermediate host. Mammals are infected when they eat fish parasitised by the infected
trematodes.
- The disease is associated only with the Pacific Northwest of North
America, since this is the only area where the first intermediate host
of the trematode, the snail Oxytrema plicifer, can live. (D251.9.w10)
- The disease only occurs if living flukes are present; the
rickettsias are released/injected into the bloodstream after the adult
fluke penetrates the mucosal lining of the gut. (D251.9.w10)
- Dead flukes, in fish which has been cooked or frozen, cannot
transmit the organism. (D251.9.w10)
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| Infectious
Agent(s) |
Neorickettsia sp. (Tenericutes (Lacking cell-walls) (Division)) |
| Non-infectious
Agent(s) |
-- |
| Physical
Agent(s) |
--
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| General Description |
Clinical signs
- In Ursus americanus - American black bear
experimentally infected by being fed trout infected with
Nanaophyetus salmonica metaceria:
- Anorexia, lassitude and diarrhoea in four of five bears, on days 9-14 after infection.
(J13.34.w3)
Gross pathology
- Mesenteric lymph
nodes: enlarged (three to four times normal size) and soft; on pressure, grey fluid could be
expressed. (
J13.34.w3)
Impression smears: rickettsial bodies visible in smears from three bears.
(J13.34.w3)
Histopathology
- Mesenteric lymph nodes: reticuloendothelial hyperplasia, oedema, lymphocytic depletion, scattered
necrotic foci.
(J13.34.w3)
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| Further Information |
Diagnosis
- Detection of the organisms and or passage of infection.
(D251.9.w10,
J13.34.w3)
- Take a fine needle aspirate of enlarged lymph nodes, stain with
Giemsa and examine microscopically for the intracytoplasmic
rickettsial bodies. (D251.9.w10)
- Infection was confirmed by the presence of rickettsial organisms in lymph node impression smears from three bears and by passage of lymph nodes to dogs in all five experimentally infected bears.
(J13.34.w3)
Treatment
- Suggested treatment includes both treatment of the rickettsial
infection and elimination of the fluke. (D251.9.w10)
- Antibiotics against the rickettsial infection include
tetracycline, 20 mg/kg orally every eight hours for three weeks, or
oxytetracycline 7 mg/kg intravenously every 12 hours until oral
dosing is tolerated or chloramphenicol, 30 mg/kg orally or
intravenously every eight hours; or trimethoprim
sulphadiazine 15 mg/kg orally or subcutaneously every 12 hours; or
sulfadimethoxone/ormetoprim, first dose 55 mg/kg orally then 27.5
mg/kg orally once daily. (D251.9.w10)
- Anthelmintic against the fluke: fenbendazole
50 mg/kg orally
once daily for 10-14 days; or Drontal Plus (praziquantel/pyrantel/febental)
according to the manufacturer's instructions. (D251.9.w10)
Prevention
- Avoid feeding salmonid fish from the Pacific Northwest, or
feed fish which have been thoroughly frozen (at least three days of
freezing for large salmon). (D251.9.w10)
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| Associated Techniques |
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| Host taxa groups /species |
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