Poster
Evaluation of gastric fluid cytology can be an important diagnostic tool in marine mammal medicine. However, references on the topic are limited. During a student preceptorship at SPAWARSYSCEN SAN DIEGO, we completed a project to evaluate gastric fluid obtained from clinically healthy Atlantic bottlenose dolphins, (Tursiops truncatus). We also investigated the digestive process and resulting cytology of fluid samples. Using filtered gastric fluid and a heated agitating water bath we were able to create a "pseudo-stomach" in the laboratory and examine the breakdown and resulting cytology of fish, squid, and aquatic plant material. Also specific fish tissues such as scales, muscle, gills, and reproductive organs were examined in independent preparations. Photomicrographs were obtained at various time intervals to evaluate and document the effects of in vitro digestion on the cytology of these gastric fluid contents. The pH of the fluid products was monitored throughout the breakdown process.
Results
Chemical and physical analysis of water parameters in the treated tanks have only shown a mild increase in the total ammonia readings after drug administration and a double check analysis under laboratory conditions has shown that, most probably, this increase was in fact a misreading of the chloroquine degradation compounds, not materially affecting the performance of the biological filter.
The number of animals per species has certainly been a limitation to the analysis of the results. Among the species treated, Pseudanthias squamipinnis and Chromis viridis showed sensitivity to the drug at both concentrations.
Autopsies carried out during the treatment on a few individuals revealed live parasites both on the skin and the gills, after the first dose of the drug. In all cases, after the second day, the trophonts on the skin were dead, and in only one case (Dascyllus trimaculatus) they were dead on the gills as well. In all cases from the second week of treatment onwards, no live parasites have been identified on either skin or gills. At the end of all the trials none of the animals from the 3 groups showed any visible signs of parasite presence and scrapings from some live animals or autopsies conducted on fish which died for unrelated causes, from 10 days to several months from the end of the treatment, did not reveal any trophont.
Due to the small number of specimens represented per species statistical analysis could not be carried out.
The number of animals, species and survival rate will be presented in the poster with final results updated to April 1998.
Discussion and Conclusion
Treatment choices should always take into account that Cryptocaryon irritans has been generally accepted as a stress related parasite (Blasiola, 1976). On this basis the only evident stress of the chloroquine bath remains the one handling after the second week of administration.
The bath protocol approach is certainly to be considered in all those cases where fish suffer loss of appetite or where a large population has undergone a history of stress followed by early detection of the disease (i.e., quarantine, previous contact with infested fish, mild outbreaks), but certainly difficult to apply in large volume exhibit tanks. If an acceptable range of therapeutic dose can be established, the oral treatment could be the solution for outbreaks in multispecific exhibit tank, even if only aimed at single valuable individuals, providing that a diagnosis is made at the initial stage.
Trials still need to be conducted under laboratory conditions that would be inclusive of fish control groups and species comparison; these studies should aim to establish if chloroquine thoroughly eradicates the parasite from the fish, to develop a proper in vivo diagnostic technique and to evaluate therapeutic tissue levels, minimum therapeutic dose, its half life and the toxicological effects.