Towards Understanding Microbial Degradation of Veterinary Drugs in Large Saltwater Aquariums

Abstract

In order to address the disappearance of chloroquine phosphate, an anti-parasitic drug, and to restore drug efficacy in aquarium systems, we collaborated with Shedd Aquarium and conducted microbial and chemical investigations focusing on tropical saltwater systems. Chloroquine phosphate is widely used as a bath pharmaceutical to treat external protozoa infections caused by Cryptocaryon irritans in aquariums, including large public aquariums like Shedd. Although common, this parasitic infection can be harmful or even deadly to animals that are already under stress from activities such as long-distance transport. For full parasite removal, a bath treatment is expected to last 14 to 21 days, during which time the chloroquine concentration needs to be maintained above a therapeutic dose. From November 2018 to January 2020, several exhibitions and quarantine systems treated with chloroquine experienced severe chloroquine degradation and the therapeutic dose could not be maintained for the prescribed period. Immediate water change but did not yield any improvement. As a result, the effectiveness of the drug has been severely jeopardized, making the animals vulnerable to ongoing infections as well as possible Cryptocaryon irritans outbreaks in the future.

In our investigation, we focused on two tropical saltwater systems. Our findings show that aquarium microbiome composition is impacted by the aquarium's residents, sampling location (tank vs pipeline), and chloroquine dosing. Several taxa belonging to the phyla Actinobacteria, Bacteroidetes, Chloroflexi, and Proteobacteria, along with functional genes related to pathways such as phenylethylamine degradation and denitrification, were found to be differentially abundant between samples where chloroquine degradation was observed and those without degradation. Overall, we found that the degradation was biological and associated with biofilm attached to water pipes. Together, these results provide practical mitigation options to prevent or delay the development of microbial chloroquine degradation. Our results further demonstrate the need to improve our understanding of the aquarium microbiome to best support healthy animal populations in closed loop aquarium systems.

Bio

Jinglin Hu is a fifth year PhD student in the Hartmann Group in the Department of Civil and Environmental Engineering at Northwestern University. Her research focuses on understanding the response of bacterial communities to chemical perturbation in the environments. She graduated from the University of Minnesota, Twin Cities with a B.S. in Environmental and Ecological Engineering in 2016.