title: Ulcerative disease outbreak in crayfish Orconectes propinquus linked to Saprolegnia australis in big Muskellunge Lake, Wisconsin.
abstract: Crayfish populations in the area of the North Temperate Lakes Long Term Ecological Research (LTER) project, Wisconsin, USA, have been monitored for >25 yr. In 2005, native crayfish Orconectes propinquus from Big Muskellunge Lake were found with ulcerated lesions in the cuticle. In 2006, lesions occurred in 9.5% of sampled crayfish from the lake (n=3146). Ulcers generally occurred on the appendages of affected individuals but varied in location and severity. The prevalence of ulcers varied widely among sites, sample depths, and sampling dates, ranging from < 2% to >20%. The prevalence of ulcers in crayfish increased from a minimum in early June to a maximum in late July and August. In aquarium trials, healthy crayfish representing either O. propinquus or O. rusticus co-housed with ulcerated crayfish did not develop ulcers within 4 wk of exposure. Gross and histopathologic analyses of ulcerated crayfish revealed the presence of filamentous hyphae in the lesions while hemocytic infiltrates, melanotic reactions and silver-stained sections indicated that the ulcers had an oomycete etiology. Excised samples of ulcerated crayfish cuticle grown in culture developed an oomycete that was identified as Saprolegnia australis by PCR amplification and sequence analysis of 2 different DNA fragments. This is the first report of the occurrence of ulcers in wild crayfish associated with S. australis infection in the U.S.A. The advent of the outbreak and its underlying ecological causes are still under investigation.
authors.affiliation: Research Animal Resources Center, University of Wisconsin-Madison, Madison, Wisconsin 53726, USA. lisakh@rarc.wisc.edu
authors.forename: Lisa
authors.initials: L
authors.lastname: Krugner-Higby
authors.forename: Danielle
authors.initials: D
authors.lastname: Haak
authors.forename: Pieter T J
authors.initials: PT
authors.lastname: Johnson
authors.forename: Jeffery D
authors.initials: JD
authors.lastname: Shields
authors.forename: William M
authors.initials: WM
authors.lastname: Jones
authors.forename: Kimberly S
authors.initials: KS
authors.lastname: Reece
authors.forename: Tim
authors.initials: T
authors.lastname: Meinke
authors.forename: Annette
authors.initials: A
authors.lastname: Gendron
authors.forename: James A
authors.initials: JA
authors.lastname: Rusak
mesh_terms: D000818:Animals; D003400:Astacoidea / Q000469:parasitology*; D004196:Disease Outbreaks; D005618:Fresh Water; D006790:Host-Parasite Interactions; D034582:Integumentary System / Q000469:parasitology / Q000473:pathology; D010802:Phylogeny; D044762:Saprolegnia / Q000235:genetics / Q000302:isolation & purification*; D014922:Wisconsin