Abstract

Microbiological assessment of the composition of blowhole microbiota is one of the mandatory routine tests carried out during veterinary-medical surveys and monitoring of the health status of cetaceans. At the same time, limited information on the spectrum of respiratory microorganisms of healthy wild and captive killer whales (KWs) is available in literature.^1-3

The current research was organized with the aims to evaluate the diversity and determine the composition of the aerobic respiratory microbiota of the wild and captive KWs at different stages of adaptation to “noogenic” environmental conditions.

The study was conducted in 2012–2019. Opportunity to perform veterinary medical examinations of KWs was provided by White Whale Ltd., Sochi Dolphinarium Ltd., “Afalina” Co, Ltd., and “Okeanarium DV” Co, Ltd. A total of 31 captured Okhotsk Sea KWs (3–9 years old; 16 males, 15 females) were surveyed. Seven whales were examined immediately after the catch near the place of capture (one big female was released just after sampling). Initial checkup of the remaining whales was carried out at the Center for Adaptation of Marine Mammals (CAMM, Srednyaya Bay, Nakhodka, Russia) upon arrival of the animals from the wild (after 5–7 days’ transportation). In CAMM KWs were housed in small groups (up to four animals) in floating sun-protected marine pools equipped with removable winter protection against cold. During the entire period of stay at the CAMM, the animals were under constant veterinary medical monitoring and were examined in regular dynamics.

Blowhole samples were collected in semisolid Stuart transport medium (Aptaca, Italy) and/or in ESwab Liquid Amies medium (Copan, Italy), placed in thermal container (at +8), and then delivered by air transport to the specialized laboratories in Moscow. Cultural studies were performed in “Shans Bio” or “Bio Vita” laboratories (by classical methods) and/or in “Vet Union” laboratory (with the use of automatic analyzers). Microbiological studies were carried out in complex with hematological, biochemical, and hormonal tests used to assess health of KWs.

As a result of the research, 38 species of microorganisms were identified in clinically healthy whales with an uncomplicated course of the adaptation process (Table 1). The minimum diversity of microbiota was detected in newly captured individuals. Significantly wider variety of species of microorganisms was found in animals, tested on the day of arrival at CAMM. Maximum microbial diversity was observed in the first three months of captivity. In this period of “early” microbiological adaptation, the detection rate of potentially pathogenic microorganisms, such as Pseudomonas aeruginosa and Enterococcus faecalis, considerably increased. Significant reorganization of blowhole microbiota with a sequential change in the prevalent microorganisms and gradual decrease in the proportion of opportunistic pathogens was noted in subsequent periods of observation. In some whales, the adaptation process was complicated by the development of infectious-inflammatory diseases. Animals were more susceptible to infections during the first 6 months of being in captivity. Probable pathogens, isolated in these cases, were Acinetobacter radioresistens, Citrobacter freundii, Edwardsiella tarda, Myroides spp., Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Candida glabrata. By the end of the observation period, several individuals showed formation of a special microbial status, which can be characterized as polymicrobial bacteriocarrier (condition described earlier for bottlenose dolphins⁴). Identified individual, seasonal, and interannual differences in the structure of respiratory microbiota of the adapting-to-captivity KWs, as well as the possible consequences and risks in the case of reintroduction of adapted individuals into the wild are discussed in the presentation.

Table 1. Identified blowhole microbiota of the wild, and adapting-to-captivity Okhotsk Sea killer whales

Legend: N—number of examined individuals; n—number of samples; *—total number of isolates=375

Literature Cited

1.  Higgins R. 2000. Bacteria and fungi of marine mammals: a review. Can Vet J. 41:105–116.

2.  Gaydos JK, Balcomb KC, Osbornec RW, Dierauf L. 2004. Evaluating potential infectious disease threats for southern resident killer whales, Orcinus orca: a model for endangered species. Biol Conserv. 117:253–262.

3.  Raverty S, Zabek E, Schroeder JP, et al. 2007. Preliminary investigation into the microbial culture and molecular screening of exhaled breaths of southern resident killer whales (Orcinus orca) and pathogen screening of the sea-surface microlayer (SML) and sub-surface water samples in Washington State. IAAAM 38th Annual Conference Proceedings, Lake Buena Vista, FL; Pp. 97–98.

4.  Andreeva NA, Ostapchuk TV, Liskun OV, Mazovskaya SV. 2013. Microbiological adaptation of bottlenose dolphins (Tursiops truncatus) to life in captivity. Scientific notes of Taurida National University. Series Biology, Chemistry 26(65) 3:3–14. (in Russian).

*Presenting author