Visit our new website

Canadian Amphibian and Reptile Conservation Network - Réseau Canadien de 
Conservation des Amphibiens et des Reptiles

Necture Tacheté - Necturus maculosus

Detroit River, Ontario
Summary:
A large die-off of Mudpuppies (possibly in the thousands) was reported from the Detroit River in southwestern Ontario in July of 2006. No other species are known to have been affected. The cause of death appears to be septicemia (Edwardsiella tarda).

Background:
A total of 27 dead Mudpuppies were collected from the Detroit River in southwestern Ontario on 19 July, 2006. Interviews with Coast Guard Search and Rescue staff indicated that, at the time of collection, the incident had been ongoing for about a month and showed no sign of tapering off. Dead Mudpuppies were reported throughout the lower end of the Detroit River, in the Amherstburg, Livingston, Sugar Island and Trenton Channels. A rough estimate suggests the number of dead animals is in the thousands. Dead animals were usually found in association with floating vegetation, with a density in the open water of approximately one carcass per 70 meters throughout the area sampled. It is unclear whether the distribution/association with vegetation was caused by wind and currents. There does not appear to be accompanying mortality in other species as only three dead fish (one Carp, one Freshwater Drum, and one Crappie) were seen, and no dead birds were observed.

Results of Necropsies

External Findings:
There is brown-tan mucoid material on the dorsum, the tail, the side and the ventrum of the snout and the side of the body wall. The dorsum is mottled grey-black with pinpoint coalescing white to tan foci, 0.25 to 1-mm in diameter, and pink-red skin around the ventral thorax and under and around the gills; the ventral surface of the hindlimbs are also red-pink.

Internal Findings:
There is brown-red turbid fluid in the coelom (~5-mL). There is yellow mucoid material in the gut, bright red mucoid material in the distal intestine which has a roughened raised mucosa and there is an irregular-shaped black marking on the distal intestinal serosa, approximately 1-cm long by 4-mm wide running longitudinally.

Histology:
Lesions are not apparent in the following tissues: heart, liver, intestine, pancreas, brain, spinal cord. The following lesions are present:

  • KIDNEY: Mild, diffuse infiltrate of polymorphs in the interstitium.

  • SPLEEN: There are multifocal areas of necrosis in which there are masses of rod-shaped bacteria, as well as many thick-walled spherical structures.

  • SKIN: There is a focal area in which the epidermis is thickened, with much distorted tissue architecture. Within this area, some cells contain brightly eosinophilic intracytoplasmic inclusions.

Bacteriology:
Large numbers of Edwardsiella tarda and a few Aeromonas hydrophila isolated from pooled kidney, liver and spleen. Large numbers of Edwardsiella tarda and a few Aeromonas hydrophila isolated from the coelomic fluid. No Salmonella species isolated.

Virology:
No virus isolated from the kidney or liver .

For more information, contact the Canadian Cooperative Wildlife Health Centre: ccwhc@ovc.uoguelph.ca