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Pathogen Page

Piscirickettsia salmonis

Table of Contents

General Information
Vaccine Information
1. Arthrobacter Live Culture Vaccine (USDA: 1K11.00)
References

I. General Information

1. NCBI Taxonomy ID:

1238

2. Disease:

Salmon Rickettsial Disease, Piscirickettsiosis

3. Introduction

Piscirickettsia salmonis is the first Gram-negative, intracellular bacterial pathogen isolated from fish and is a significant cause of mortality in salmonid fish (Fryer and Hedrick, 2003).

4. Microbial Pathogenesis

Microscopic lesions caused by P. salmonis in naturally acquired infections can be found in numerous organs and tissues characteristic of a systemic or septicaemic condition. Although the sequential development of the naturally acquired infections has not been reported, initial infections presumably commence when the physical barriers of the skin and/or gills are breached by the bacterium (Almendras et al. 1997; Smith, Pizarro, Ojeda, Contreras, Oyanedel & Larenas 1999). Replication of the bacterium results in raised discoloured areas on the skin that may then progress to shallow ulcers, as observed under field conditions and following experimental applications of the bacterium with filter paper patches to the skin (Smith, Contreras, Larenas, Aguillon, GarcÃ©s, Perez & Fryer 1997). Direct dispersion of the bacterial suspension onto the gills also initiates local infections that spread via the blood (haematogenous) and then via major vessels to the parenchyma of numerous organs (Almendras et al. 1997). A serosal spread of the bacterium is more characteristic of infections induced by intraperitoneal injections of the bacterium. In injected fish, the capsules of the major organs in the peritoneum are sites of replication prior to invasion of the parenchyma (Almendras et al. 1997). In the later stages of infection the internal and microscopic pathological changes observed in fish exposed via different routes become similar, most likely because septicaemia eventually occurs even in cases of the serosal spread of the bacterium (Cvitanich et al. 1991). The septic nature of infections is demonstrated by the presence of infected macrophages visible in blood smears from heavily infected fish (Cvitanich et al. 1991) (Fryer and Hedrick, 2003).

5. Host Ranges and Animal Models

The transmission of P. salmonis in natural infections is horizontal or fish-to-fish and no vector is required. The reservoir for the bacterium is unknown but may include one or more species of fish or other aquatic animals. The principal hosts for P. salmonis are salmonid fish. Coho salmon was the species involved in the first recorded outbreaks of piscirickettsiosis in Chile. The disease has also been reported in rainbow trout, cherry salmon, Oncorhynchus masou (Walbaum), and Atlantic salmon in Chile (Fryer and Hedrick, 2003).

6. Host Protective Immunity

The immune response of salmonids to P. salmonis infections remains poorly understood, but more recent studies, including successful laboratory vaccine trials, provide optimism for this approach to control of the disease. The humoral response following natural or experimental exposures to P. salmonis is weak, although anti-P. salmonis antibodies have been detected in the serum of convalescent coho salmon (Fryer and Hedrick, 2003).

II. Vaccine Information

1. Arthrobacter Live Culture Vaccine (USDA: 1K11.00)

a. Manufacturer:

Novartis Animal Health US, Inc

b. Vaccine Ontology ID:

VO_0001819

c. Type:

Live vaccine

d. Status:

Licensed

e. Location Licensed:

USA

f. Host Species for Licensed Use:

Trouts, salmons & chars

III. References

1. Fryer and Hedrick, 2003: Fryer JL, Hedrick RP. Piscirickettsia salmonis: a Gram-negative intracellular bacterial pathogen of fish. Journal of fish diseases. 2003; 26(5); 251-262. [PubMed: 12962234].