Abstract

Parasitism of the ear sinuses in odontocetes has resulted to be a serious and more frequent illness than expected. Two parasites, nematodes of the genus Crassicauda and trematodes of the genus Nasitrema, have been described in the air spaces as causing severe lesions and even death. The paraotic sinuses are strategically located, surrounding the ear complex and in close relation with the cranial nerves exiting the brain. There are no helpful diagnostic methods for assessing possible ear region damage but limited analysis like hematology or egg findings in culture swabs or blow extensions. For the purpose of introducing endoscopy as a diagnostic tool the anatomy of the paraotic sinuses is presented as well as its nasal access.

Heads of different species of odontocetes were studied by means of standard dissection, serial cutting in different planes and imaging techniques. Endoscopy was performed testing different probes ranging from 3 to 10 mm. in diameter.

The introduction of the endoscope probe through the nasal sac system has to go beyond its closing structures, the blowhole, the slitlike opening and the nasal plug. Right ventrally, once the probe reaches the bony tract, it has to deepen following the lateral wall. The external opening of the pharyngotympanic tube (PTT) lies in the lateral aspect of the mucosa covering the laryngopharyngeal sphincter. When entering the PTT the duct bends caudally towards the ear complex. The big internal opening of the PTT allows the introduction of the endoscope in a caudal orientation pointing at the middle ear. For a good inspection of the rest of the sinuses a bending of approximately 180 degrees of the probe head must be achieved to observe the rostral end of the air spaces, anterior and pterigoid sinuses. Although, the most common ten millimeter probes can be used, especially in large species, the limiting size of the PTT opening recommends using 5 mm. or even better 3 mm. ones.

The diagnosis of the paraotic region parasitism through endoscopy appears to be a useful and conclusive method in spite of the restraint availability of the apparatus. Moreover the accessibility of the paraotic sinuses expands the procedure as a direct method for drug delivery avoiding general antiparasitary treatment. Although endoscopy is well suited for captive animals, it should be included in the clinical routine of stranded dolphins when illness is suspected because of the parasite high incidence in many species inhabiting different areas.