PHYSICAL EXAMINATION AND DIAGNOSTICS
Cetacean diagnostics have advanced, but the fundamentals of examination and clinical approach covered in Blyde and Vogelnest (2008) still apply.
1.1 Imaging
Significant advances have been made in diagnostic imaging of cetaceans, facilitated by the availability of high-quality portable radiographic and sonographic equipment.
CT
Fig. 46.1. Juvenile humpback whale (Megaptera novaeangeliae) entangled in shark netting off Australia's Gold Coast.
and magnetic resonance imaging are being used with increasing frequency (Van Bonn et al. 2001). They have been used for clinical diagnostics and research (Dennison et al. 2012). Ultrasonography is particularly useful in cetaceans because their smooth, hairless skin and emersion in water enhance acoustic coupling and animals are readily trained to accept the procedure. Routine screening scans of the abdomen and thorax may be useful in identifying abnormalities that are not apparent on physical examination (Dold 2015). In addition to primary imaging, ultrasonography aids sample collection, such as venipuncture, cystocentesis and organ biopsies, and guiding IV catheter placement (Ivancic et al. 2015).
1.2 Auditory testing
Odontocetes use auditory processing of echolocation for navigation, foraging, predator evasion and socialisation. Mann et al. (2010) demonstrated that as many as 57% of stranded common bottle-nosed dolphins and 36% of stranded rough-toothed dolphins (Steno bredanensis) studied had hearing impairments. In a study by Strobel et al. (2017), 63% of stranded individual cetaceans with diagnosed hearing loss behaved differently to animals with normal hearing. Hearing can be assessed by using auditory evoked potential (AEP) testing. AEP studies should be undertaken on all stranded cetaceans that enter a rehabilitation facility.
Hearing loss could be the primary reason for or contribute to an individual cetacean stranding. Animals with substantial hearing loss have a poor prognosis for rehabilitation and release. Brucellosis has been described as a potential cause of vestibulocochlear nerve damage leading to hearing deficits and should be investigated in these cases (see section 4.1.2c).1.3 Respiratory vapour analysis
The respiratory vapour or secretions (‘blow’) can be used to detect and measure reproductive hormones (F Min- gramm, unpublished), stress hormones including cortisol (Thompson et al. 2015), bacterial flora of the upper respiratory tract (C Vendl, unpublished) and volatile and non-volatile compounds such as hydrocarbons, aromatic alcohol, amino acids and peptides (Aksenov et al. 2014). ‘Blow’ can be collected directly into sterile containers placed above the animal’s blow hole during exhalation. The vapour can also be collected into containers lined with nylon tulle and extracted (F Mingramm, unpublished). By examining the metabolome from normal healthy animals and comparing it with that of diseased animals it may be possible to detect certain disease syndromes (Aksenov et al. 2014). This technique, which is challenging because of the need for specialised equipment, the cryptic nature of many cetacean species and the potential for contamination from sea water, may be extrapolated to free-ranging populations.