Abstract

Introduction

The weedy seadragon (Phyllopteryx taeniolatus) is a dramatic animal found in the temperate waters of southern Australia. Both the weedy seadragon and the leafy seadragon (Phycodurus eques) are members of the family Syngnathidae which includes the seahorses and pipefish.² Seadragons are currently being displayed in multiple aquaria throughout North America and are popular exhibit animals that are used to exemplify conservation in the Australian marine environment as well as coastal environments in general. Under current Australian law, effective in 1998, syngnathids are not allowed to be exported without a special permit. In addition, only those bred in captivity or collected under a government approved program are considered as candidates for exportation.³ The identification of coccidian parasitism in captive weedy seadragons represents a potential threat to the health of these animals and creates a significant management challenge for their caretakers. Coccidiosis is commonly found in many species of cartilaginous and bony fishes; in syngnathid species, coccidiosis has been reported in the great pipefish (Syngnathus nigrolineatus).^1,5 This report describes the clinical investigation of coccidiosis in weedy seadragons.

Environmental Management

Seadragons have very specific environmental requirements and thus are difficult to maintain in a captive setting. It is important to optimize environmental conditions in order maximize the animal's health. The weedy seadragons maintained at the New England Aquarium (NEAq) are housed with leafy seadragons in a 700 gallon tank. Water quality parameters are closely controlled with the temperature maintained between 14.5 and 15.5°C, salinity between 29 and 31 parts per thousand (ppt), pH 8.0-8.2, ammonia <70 mg/L, nitrite 0 mg/L, and nitrate < 3 mg/L. Seadragons require live food and mysid shrimp (Mysidacea spp.) are fed once a week. In addition fatty acid and lipid / vitamin enriched (Super Selco®, INVE Aquaculture, Dendermonde, Belgium) adult brine shrimp (Artemia selena) are fed three to four times per week. The water is purified by an undergravel filter, a foam fractionator (A.E. Technology Inc., Poughaug, NY, USA) and an UV sterilizer (Emperor Aquatics Inc. Pottstown, PA, USA). Water passing from the tank to the sump is filtered through 100 micron tubular bag filters (Aquaculture Supply, Dade City, FL, USA) which remove most of the particulate matter.

Clinical Signs and Diagnosis

Two weedy seadragons from the NEAq's collection were diagnosed with coccidial infections. The first animal's clinical signs included retarded growth, anorexia, labored respiration, disorientation, a superficial erosion of the dorsal fin and negative buoyancy. Diagnosis of coccidial infection was made on postmortem examination of intestinal scrapes from the first animal. The samples contained approximately 15 to 20 sporulated coccidial oocysts when viewed with a compound microscope viewed at 200x magnification. The coccidian parasite was identified as Eimeria phyllopteryx, a previously unrecognized species.⁴ Histopathology of the distal third of the animal's intestine revealed that 80% of the epithelial cells were occupied by various sexual and asexual stages of the coccidian. Enterocytes of the crypts of the villi were most affected though the middle and apical epithelial cells were also involved. The remaining normal cells were compressed by the parasite infected cells. The animal also had an Uronema-like parasite in the dermis of the skin around the head, which may also have contributed to mortality of this animal.

An antemortem diagnosis was made on the second animal based on identification of sporulated coccidial oocysts on direct fecal examination. Approximately 10 to 15 sporulated oocysts per field were visible when the sample was viewed with a compound microscope at 200x magnification. Fecal samples were also noted to contain undigested food particles. This animal was diagnosed five weeks prior to its death and showed only mild disorientation before dying acutely. Histopathology revealed marked coccidial infection of the intestinal epithelium with marked villous atrophy and the presence of degenerate epithelial cells in the intestinal lumen. Multiple stages of Eimeria were seen within the enterocytes.

Medical Management

The first animal was moved to a bare bottom tank. Due to the animal's negative buoyancy, a polypropylene sheet elevated on two 1" diameter polyvinylchloride pipes was draped across the bottom of the tank in order to help prevent pressure necrosis. The animal was given a 10 min. dip in 4 ppt saline that had been temperature and pH-matched to the animal's original tank water. This was done to help hydrate the animal as well as help to remove any potential parasites, though skin scrape of this animal did not reveal ectoparasites. In order to prevent secondary infection the seadragon was exposed to a ciprofloxacin (Cipro®, Bayer Corporation, Pharmaceutical division, West Haven CT, 06516 USA) bath at a concentration of 6.7 mg/L for one hour daily for three days. At this point there was little response to therapy and the animal remained anorectic.

Treatment was changed to tube feeding of enrofloxacin (Baytril®, Bayer Corporation, Agricultural division, Shawnee Mission, KS, 66201 USA) at 10 mg/kg every 72 hours; 24 hours after the first enrofloxacin treatment the dragon voluntarily ate several mysid shrimp. This treatment was performed once more with the addition of enriched baby brine shrimp (Artemia selena) to increase the nutritional plane of the patient. The animal died the following day, just nine days after it presented with a clinical problem.

The second animal appeared clinically normal despite the coccidial infection. A course of diclazuril (Vecoxen®, Jensen Pharmaceutica, Sundown, Republic of South Africa)* was initiated at a dosage of 10 mg/kg; this was tube fed to the animal once a week for three weeks. Subsequent fecal samples still contained sporulated coccidial oocysts and a second course of diclazuril treatment was started. Only one treatment was given to the dragon before it died acutely, just prior to the second treatment. Only mild disorientation was exhibited before the animal expired. It is unknown whether the diclazuril treatment contributed to the animal's death though clinical trials of this drug in potbelly seahorses (Hippocampus abdominalis) caused no apparent clinical problems.

Shedd Aquarium Seadragon Cases

Similar problems have been seen at the Shedd Aquarium in Chicago where four weedy seadragons have determined to be infected with coccidia based on histopathology. Histological findings are similar to those seen at NEAq showing marked infection of the enterocytes with multiple stages of the coccidian. The infections have been severe enough to distort the normal villous and crypt architecture. Death in one of Shedd Aquarium's fish was attributed to acute bacterial sepsis and in a second individual was due to severe proliferative bronchitis. No definitive cause of death was determined in the remaining two fish, however intestinal coccidiosis in all individuals was speculated to have caused some degree of intestinal dysfunction, contributing to the clinical course of disease. Treatment attempts have been unsuccessful and included tube feeding the animals with Sulfamethoxazole-Trimethoprim (Sulfatrim®, Barre-National Inc., Baltimore, MD 21244 USA) at 30 mg/kg once a day for five days. It is currently under investigation whether the species of Eimeria involved is the same between the two institutions.

Conclusions

Coccidiosis has contributed to morbidity and possibly mortality in the weedy seadragon populations at both the NEAq and the Shedd Aquarium. To date no treatments have been successful in the elimination of the coccidial infection and its management is still under investigation. It is unknown if there is more than one fish species affected by Eimeria phyllopteryx. So far the leafy seadragons, housed in the same aquarium system as the infected weedy seadragons at NEAq, have had multiple negative fecal samples and show no clinical signs of disease. Research is still being conducted into this problem and institutions or individuals with knowledge of this disease or related problems are encouraged to contact the authors so that a more thorough account can be documented.

*This drug was used with permission of the Department of Compliance, Food and Drug Administration, Rockville, MD.

Acknowledgements

The authors would like to thank the following individuals for their contributions to this study: Robert Cooper, Sonia Mumford, and Casey Sugarman of the New England Aquarium for their parts in diagnosing and managing these cases; Michael Callahan of the New England Aquarium for his contributions relating to dragon handling and husbandry; Steve Upton of Kansas State University, Manhattan, Kansas for the identification of New England Aquarium samples of this previously unrecognized coccidian; Robin Overstreet of the Gulf Coast Marine Lab for identification of the Shedd Aquarium coccidian; and Mac Law of the North Carolina State University, College of Veterinary Medicine, for his rapid histopathological diagnosis of the NEAq's second weedy seadragon.

References

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2.  Dawson CE. 1985. Indo Pacific Pipefish--Red Sea to the Americas. Gulf Coast Research Laboratory. Ocean Springs, Mississippi, USA.

3.  Groves P. 1998. Leafy Seadragons. Scientific American. Dec. 1998. Pp. 85-89.

4.  Upton S, Stamper MA, Mumford SL, AL Osborn. Unpublished. A new species of Eimeria (Apicomplexa, Eimeriidae) from the weedy seadragons, Phyllopteryx taeniolatus (Pisces: Syngnathiformes).

5.  Yakimoff WL, WF Gousseff. 1936. XVII.--Eimeria syngnathi n. sp., a new coccidium from the great pipe fish (Syngnathus nigrolineatus). J. Micr. 56:376.