Workshop Report

Background

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 mammals.

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.

Workshop Objectives

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.

Format

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.

Presentation Overviews

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 industry.

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 disease.

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 Discussion

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.

Vaccination Discussion

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 inconsistency.

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.