Rickettsia-like organism associated with tremor disease and mortality of the Chinese mitten crab Eriocheir sinensis

Abstract

We report the discovery of a rickettsia-like organism (RLO) in cultured freshwater Chinese mitten crab Eriocheir sinensis. The RLO caused tremor disease and was apparently responsible for a mass mortality (30 to 90%) in 2 provinces in southeast China. Moribund crabs were investigated from different districts during outbreaks in 1999 and 2000. With electron microscopy, 3 different pathogens were detected in moribund crabs: a rickettsia-like organism (RLO), virus-like particles (VLP) and a microsporidian-like protozoan (MLP). Based on the high prevalence, infection intensity and cytopathological signs, the RLO was considered to be the probable cause of the high mortality. Both VLP and MLP occurred at low prevalences and were considered secondary infections. The RLO was 0.22 to 0.35 µm in diameter, granular or clavate, bounded by a cell wall and membrane, and possessed no nucleus but a nucleoid was present. When dividing, RLOs occurred in irregular shapes, such as dumbbells, awls, and crescents. The RLOs exhibited a predilection for muscle and connective tissues and were probably transported to various tissues and organs by hemocytes.

Molecular cloning, genomic organization and functional analysis of an anti-lipopolysaccharide factor from Chinese mitten crab Eriocheir sinensis

“…The untreated crabs and crabs that received an injection of 50 ml PBS were used as the blank group and the control group, respectively. The injected crabs were returned to water tanks and three individuals were randomly collected at 2,4,6,8,12,16,24,32,48 and 72 h post-injection. The haemolymphs from the blank, control and challenge groups were collected using a syringe from cheliped in an equal volume of anticoagulant modified Alsever solution (27 mM sodium citrate, 336 mM NaCl, 115 mM glucose, 9 mM EDTA, pH 7.0) [27], and centrifuged at 1000g, 4 1C for 10 min to harvest the haemocytes.…”

“…With the development of intensive culture, various diseases caused by bacteria, viruses and rickettsia-like organisms had frequently occurred in cultured E. sinensis populations [1][2][3][4][5][6] and caused catastrophic losses to the crab aquaculture. Understanding the immune defence mechanisms of the species and characterization of immune effectors are believed to be helpful to health management and diseases control in crab aquaculture.…”

Molecular detection methods developed for a systemic rickettsia-like bacterium (RLB) in Penaeus monodon (Decapoda: Crustacea)

“…To survive and reproduce, the rickettsia organism must enter the eucaryotic host cell, multiply within the cell, exit and reestablish this cycle in another cell (Winkler 1990). Rickettsia-like microorganisms infect a wide range of aquatic crustaceans including amphipods, crabs, freshwater crayfish and prawns (Federici et al 1974, Harshbarger et al 1977, Bonami & Pappalardo 1980, Larrson 1982, Johnson 1984, Brock et al 1986, Anderson et al 1987, Krol et al 1991, Frelier et al 1992, Fryer & Lan-nan 1994, Bower et al 1996, Jimenez & Romero 1997, Edgerton & Prior 1999, Wang & Gu 2002.…”

Proteínas transmembranales de organismos tipo rickettsia (OTR) en animales acuáticos: Factores de adherencia, invasión e infección

“…Aunque la mayoría de los estudios se han realizado sobre enfermedades en vertebrados y no sobre invertebrados acuáticos; se presupone que el modo de infección sea equivalente, ya que los genomas de distintas especies de rickettsias son altamente conservados, por lo que se espera que codifiquen para proteínas similares, con participación semejante en los mecanismos de infección (Wang & Gu 2002). La presencia de algunas translocasas tales como ADP/ATP translocasa parece tener una distribución universal en patógenos Tabla 5.…”