John G. Shedd1;Jeffrey R. Boehm1; Geraldine
Lacave2; Rhonda Patterson3
Erysipelas has been the cause of significant morbidity and mortality in
cetaceans for decades. The acute, septicemic form of the disease can lead to fatalities within
hours, following a disease course that manifests with few clinical signs. Although the causative
organism, Erysipelothrix sp., is a well-characterized pathogen in domestic animal
medicine, the pathogenesis and control of the disease is poorly understood in marine
A three-day workshop at the John G. Shedd Aquarium in 2000 brought together
clinicians and research scientists to share information and develop strategies for advancing the
study of erysipelas in cetaceans.
The workshop objectives were to" (1) share current knowledge about
erysipelas, specifically as it affects cetaceans, (2) develop and prioritize an agenda of
research that will advance knowledge of the disease and provide clinicians with greater
resources to control and prevent it, and (3) develop research funding strategies.
Twenty-one participants representing 13 institutions and three countries
included representatives of aquarium and zoo husbandry and veterinary staffs, veterinary
pathologists, research scientists and students. The workshop was a balance of invited
presentations and facilitated group discussions; all discussions were recorded to create the
basis for comprehensive proceedings.
Dr. Richard Wood (Retired, National Animal Disease Center, USDA, Ames,
Iowa USA) presented a history of erysipelas in domestic animals (swine), and an overview of E.
rhusiopathiae identification and disease manifestations. Discussion included a history of
the development of an effective vaccine in swine.
Dr. Patterson presented a distillation of selected literature on erysipelas
research. Discussion centered on advances of the last 20 years and highlighted the recent
increase in Japanese research. Of note were studies focused on the characterization of an
antigen believed to be protective.
Ms. Brigita Harris (microbiologist, Shedd Aquarium) led a discussion on
pathogen surveillance techniques: The presentation included results of feed fish testing and
recommendations on standardized microbiologic techniques for isolating the organism.
Mr. Dick Mathews (IBA -- Food Safety Division, Gumee, IL, USA) led
discussion on food sterilization techniques focused on the feasibility of using this technology
to provide a safe and cost-effective means of reducing E. rhusiopathiae in feed fish. The
state of technology and its availability currently precludes this use. There was great interest
among participants in monitoring further advances in this technology applied to the seafood
Drs. Patterson and Lacave presented overviews of research at their
respective laboratories. Progress was reported in the development of diagnostic tests for
erysipelas using techniques specific to marine mammal species. In addition, work was described
on the characterization of isolates of Eirhusiopathiae obtained from cetaceans following
fatal and nonfatal cases. Trial vaccinations are under way in Belgium and Portugal, and
preliminary results suggest that vaccine therapy may be effective in controlling this
Dr. Lacave reported on a survey of the prevalence of erysipelas and the
associated morbidity and mortality in captive cetaceans. The survey, covering the years
1989-2000, had a response rate of 65 per cent. Preliminary results suggest that while erysipelas
is seen worldwide in both vaccinated and unvaccinated animals, incidence of disease is lower in
animals that have been vaccinated more than once. Her work pointed out a wide disparity in
clinical approaches to vaccinating, with some facilities currently not using a vaccine or using
it a single time, while others vaccinate very regularly or sporadically.
Research goals fell into two broad categories: immunology and
epidemiology. Proposed Immunology studies include the development of quick, effective diagnostic
tests, as well as the further characterization of the organism and its protective antigen
component. Epidemiologic studies discussed include a standardized approach to the microbiologic
surveillance of feed fish and correlation studies between these organisms and morbidity and
mortality in cetaceans.
The history of erysipelas vaccination in cetaceans and current vaccination
strategies was discussed in depth. Thus far, vaccination protocols have been inconsistent among
institutions and participants sought consensus on how facilities should proceed.
Concern exists regarding the incidence in U.S. facilities of untoward side
effects linked to erysipelas vaccination and, subsequently, many facilities have discontinued
its use. [Routine vaccination of cetaceans has not occurred in the United States since 1990,
which is prior to Dr. Lacave's survey.] Vaccination trials are under way however at European
facilities and thus far there have been no reactions that suggest that the administration of the
vaccine is unsafe. Understanding the composition of the current vaccine and comparing it
(specifically the adjuvants used) to previous vaccines administered in the U.S. may clarify this
An overriding concern among participants was the lack of any method for
measuring the efficacy of erysipelas vaccines in cetaceans. With perceived risk yet associated
with vaccines, it was seen as imprudent to initiate new trials until such tools are available.
The group recommended that investigations into developing diagnostic tests (e.g., ELISA)
specific to protective antigens precede any new vaccination trials. New diagnostic tests could
help evaluate the current vaccine trials in Europe and any future vaccine trials.
Support and Funding Strategies
University of Ghent and the University of Southern Mississippi are two
laboratories currently engaged in work that complements the developed research agenda. A matrix
of research projects and potential supporting/funding institutions was proposed as a strategy
for engaging aquariums in the support of this work. This matrix will be useful in tracking and
communicating progress, and linking supporting institutions with laboratories. Specific
arrangements for funding will be left to the individual aquariums and laboratories.