When presented with a blubber layer the cysts can be carefully dissected.

When isolated they look like this…

but they can have many forms.

What are they ?

What is their true name ?

What other intermediate metacestodes can used to presume infection ?

Who is the final host ?

The distinguishing characteristics include compatible length and maximum width, lack of pre-acetabular vitellaria, weakly lobed testies and ovary divide into 2-4 blunt lobes (Neiland, et al., 1970).

The parasite is implicated for several type of disease.

1) Irritation and competition for nutrients, mostly likely not a component of diseases without unusually high colonization rates.

2) Migration into the brain along a nerve tract; any CNS involvement can cause fatal acute disease and serious chronic medical problems.

3) Chronic pulmonary irritation and inflammation from inhaling the eggs, which act as small foreign objects, deep into the bronchial tree.

(Chronic sterile interstitial pneumonia with nodules) – Kumar et al., 1975.

But it gets worse….

4) The migration of Nasitrema along the 8th cranial nerve, with eggs embedded into the crevices of the nerves (Morimitsu et al., 1992).

And still worse….

Additionally, adult Nasitrema have been found in brain tissue with both chronic and acute lesions (Daily and Walker, 1978) easily capable of causing strandings.

Nasitrema encephalitis (O’Shea et al., 1991) may be the most extreme form, but infection occurs in the air sinus, brain, and even in the umbilical artery (Daily and Walker, 1978).

So a full account of the effect on strandings requires a full necropsy with a complete gross and histological examination of the brain and 8th cranial nerve.

A diagnosis of infection can be made by examining the “blow” from a captive cetacean looking for the characteristic golden brown triangular eggs.

Collecting a dolphin blowhole sample. Photo by Frere et al., 2010, PLoS ONE 5(8): e12299.

Here is a closer look.  The black marks are 1mm each.

Further identification requires examination of internal structures, which is traditionally accomplished by clearing, staining, dehydrating, and mounting.  As I am more veterinarian then parasitologist, I opted to turn the specimens into biopsy samples and had them processed into standard H&E 5um slides.  Here is a full worm spread out on a composite digital micrograph.

What is the parasite?

How does it relate to the stranding?

How would you diagnose the infection with a dolphin in rehabilitation?

enjoy . . .

These are roundworms or nematodes.  The first clue was obscured in the original post (didn’t think I was going to make this too easy did you?) and required you to look at the oral opening and the three lips (covered in this case by the capsule). This and the marine mammal host place them in the family Anisakidae.

Here is a close up of the lips from another specimen (in this case a harbor seal, likely a different genus), each red arrow points to a “lip”.

The capsule (a molt) and the point on the terminal end (a mucron), combined with the  lack of spicules or eggs, identifies this as a larval form (L3).

This is a classic group of marine nematodes where the adults inhabit marine mammals and the larva use a huge number of different intermediate and transport hosts.  The Anisakidae are further classified into their respective genus by the morphology of their esophagus, ventriculus and presence or lack of an intestinal caecum (see chart).  In this case, the simple ventriculus identifies the genus Anisakis.

The species identification requires the adult (or L5) males which were not observed in this case.

Many reviews of the Genus Anisakis (Dujardin, 1845) have been published; for the truly geeky see the following:  Davey 1971; Abollo and Pascual 2002.

Known species of Anisakis:
A. physeteris (Baylis, 1923)
A. typica (Diesing, 1860)
A. simplex (Rudolphi, 1809) senso lato complex (with 13 synonyms)
A. simplex s.s.
A. pegreffi (Campana, Rouget & Bioca, 1954)
A. simplex (Nascetti et al., 1986)
A. ziphidarum (Paggi, et al., 1998)
A. brevispiculata (Dollfus, 1966)

Of these,  A. simplex , A. brevispiculata, and A. physeteris have all been found in Kogia.

The larval forms are zoonotic and can be pathogenic to the host, particularly in large numbers or when they cause ulceration.  The worm in the blowhole was likely aspirated as a terminal event, as the worms are inhabitants of the stomach. The genus is intensely studied as the larval worms are human health hazards, typically encountered by eating improperly cooked fish and resulting in the unpleasant disease called Anisakiasis.  Recent genetic studies may hold the key to correct identification of larval forms.

The best way to handle them (besides “with gloves” which I also accepted) is to wash them by shaking them in a jar with 0.9% saline to remove blood and mucous, then fix them in near boiling saline for 5 seconds to straighten the worms, then move them to a vial with 70% ethanol and add a few drops of glycerin.  They can also be fixed in glacial acetic acid for a few hours and stored in 70% ethanol with a few drops of glycerin added.

…at least for the parasites, thanks to Suzanne Thurman for sending along samples of the acanthocephalan parasite Bolbosoma turbinella from a Sei Whale stranded which stranded Delaware.   This parasite is known from several baleen whales (the big ones), including the humpback, blue (the largest whale), and northern right whale (one of the most endangered whales).  While it may not have caused the stranding the heavy burden would have some effect on the whale. Our lab focuses an parasites and parasitic diseases of stranded marine mammals and sea turtles.