Consider the science below and what facts are known about this disease.
https://www.frontiersin.org/articles/10.3389/fmicb.2018.00452/full
Identification of Four Distinct Phylogenetic Groups in Flavobacterium columnare With Fish Host Associations
Benjamin R. LaFrentz1*,
Julio C. García1,
Geoffrey C. Waldbieser2,
Jason P. Evenhuis3,
Thomas P. Loch4,
Mark R. Liles5,
Fong S. Wong6 and
Siow F. Chang6
- 1Aquatic Animal Health Research Unit, United States Department of Agriculture – Agricultural Research Service, Auburn, AL, United States
- 2Warmwater Aquaculture Research Unit, Thad Cochran National Warmwater Aquaculture Center, United States Department of Agriculture – Agricultural Research Service, Stoneville, MS, United States
- 3National Center for Cool and Cold Water Aquaculture, United States Department of Agriculture – Agricultural Research Service, Kearneysville, WV, United States
- 4Department of Pathobiology and Diagnostic Investigation, College of Veterinary Medicine, Michigan State University, East Lansing, MI, United States
- 5Department of Biological Sciences, Auburn University, Auburn, AL, United States
- 6MSD Animal Health Innovation Pte. Ltd., Singapore, Singapore
Columnaris disease, caused by the Gram-negative bacterium
Flavobacterium columnare, is one of the most prevalent fish diseases worldwide. An exceptionally high level of genetic diversity among isolates of
F. columnare has long been recognized, whereby six established genomovars have been described to date. However, little has been done to quantify or characterize this diversity further in a systematic fashion. The objective of this research was to perform phylogenetic analyses of 16S rRNA and housekeeping gene sequences to decipher the genetic diversity of
F. columnare. Fifty isolates and/or genomes of
F. columnare, originating from diverse years, geographic locations, fish hosts, and representative of the six genomovars were analyzed in this study. A multilocus phylogenetic analysis (MLPA) of the 16S rRNA and six housekeeping genes supported four distinct
F. columnare genetic groups. There were associations between genomovar and genetic group, but these relationships were imperfect indicating that genomovar assignment does not accurately reflect
F. columnare genetic diversity. To expand the dataset, an additional 90 16S rRNA gene sequences were retrieved from GenBank and a phylogenetic analysis of this larger dataset also supported the establishment of four genetic groups. Examination of isolate historical data indicated biological relevance to the identified genetic diversity, with some genetic groups isolated preferentially from specific fish species or families. It is proposed that
F. columnare isolates be assigned to the four genetic groups defined in this study rather than genomovar in order to facilitate a standard nomenclature across the scientific community. An increased understanding of which genetic groups are most prevalent in different regions and/or aquaculture industries may allow for the development of improved targeted control and treatment measures for columnaris disease.
H. Abdelhamed, S.W. Nho, A. Karsi, M.L. Lawrence, The role of denitrification genes in anaerobic growth and virulence of
Flavobacterium columnare,
Journal of Applied Microbiology, Volume 130, Issue 4, 1 April 2021, Pages 1062–1074,
https://doi.org/10.1111/jam.14855
Introduction
Flavobacterium columnare is a long Gram‐negative rod causing columnaris disease, which affects numerous fish species worldwide (Wagner
et al.
2002). Six genomovar types have been described among
F. columnare isolates (I, II, II‐B, III, I/II and II‐A) (LaFrentz
et al.
2014; Garcia
et al.
2018). More recently,
F. columnare isolates were reclassified into four genetic groups based on 16S rRNA gene sequences (LaFrentz
et al.
2018). Genetic group 2 is the most virulent for channel catfish (
Ictalurus punctatus) (Triyanto and Wakabayashi
1999; Shoemaker
et al.
2008). In the United States,
F. columnare is responsible for significant economic losses in channel catfish aquaculture (Wagner
et al.
2002). Infected catfish often exhibit external lesions on the body surface, gills and fins
. Flavobacterium columnare may cause chronic infection with low‐level mortalities, or it may cause acute infection with mortalities occurring within a few days (Declercq et al. 2013; Mohammed and Arias 2014). Host stress (e.g. low oxygen, high nitrite and ammonia, elevated water temperature, mechanical injury or crowding) enhances the occurrence and severity of columnaris disease. Minimizing fish stress helps prevent columnaris disease outbreaks, but the ubiquitous presence of this pathogen in aquatic environments makes eradication of the disease in aquaculture systems difficult.
Red added by me