# Neutrophil differentials in bronchoalveolar lavage fluid in bottlenose dolphins (Tursiops truncatus) and beluga whales (Delphinapterus leucas) during treatment of respiratory infection: a preliminary study

## TL;DR

This study explores how bronchoalveolar lavage fluid neutrophil levels can help track respiratory infections in dolphins and beluga whales, showing they reflect lung inflammation better than blood markers.

## Contribution

The study introduces BALF neutrophil differentials as a novel diagnostic tool for respiratory infections in cetaceans.

## Key findings

- BALF neutrophil differentials decreased after antimicrobial treatment, indicating localized respiratory inflammation resolution.
- Blood inflammatory markers remained elevated in cases with concurrent conditions like wounds or anemia.
- Microorganisms in blow samples did not match those in BALF, highlighting BALF's specificity for lower respiratory infections.

## Abstract

Respiratory infections are major health concerns in wild and managed cetaceans, yet reliable methods for assessing lower respiratory tract inflammation are limited. We aimed to evaluate the clinical utility of bronchoalveolar lavage fluid (BALF) neutrophil differentials in three managed bottlenose dolphins (Tursiops truncatus) and three managed beluga whales (Delphinapterus leucas) undergoing treatment for respiratory infections. Infection status was monitored by assessing isolated bacteria and fungi from BALF, BALF neutrophil differentials, and inflammatory markers in the blood, such as total leukocyte counts, plasma fibrinogen levels, and serum iron levels. In animals with respiratory bacterial and/or fungal infections alone, both BALF neutrophil differentials (47.3–55.7%) and blood inflammatory markers were elevated. Following antimicrobial treatment, the differentials decreased (0.8–3.8%), and blood inflammatory markers also returned to normal ranges. Contrastingly, in animals with concurrent conditions, such as respiratory bacterial and/or fungal infections accompanied by wounds on the tail fin or infection-induced iron deficiency anemia, persistent blood inflammatory markers were observed after antimicrobial treatment. Despite this, BALF neutrophil differentials, which are specific to respiratory inflammation, decreased in response to treatment (3.1–21.6%). Moreover, microorganisms isolated from blow samples from these animals were not consistent with those isolated from BALF at the same time. These findings suggest that BALF reflects localized respiratory infection more accurately than the inflammatory markers in the blood, and BALF examination is useful for diagnosing microbial infections in the lower respiratory tract in cetaceans. This approach may improve clinical decision-making and therapeutic outcomes in managed cetacean populations worldwide.

The online version contains supplementary material available at 10.1007/s11259-026-11112-8.