Abstract

Parasitic mastitis has been reported as a post mortem finding in the Atlantic white-sided dolphin, Lagenorhyncus acutus, the finless porpoise, Neophocoena phocoenoides , the bottlenose dolphin, Tursiops truncatus and the Dall's porpoise, Phocoenoides dalli.¹ The causative nematode in all cases was proposed to be the same Crassicaudid, with slight morphologic variations.¹ Geraci et al. (1978) postulated that parasitic mastitis may impact on reproductive success by reducing milk output, thereby compromising calves. Crassicaudids are said to be 'commonly observed in mammary tissue'² of cetaceans at necropsy and to require an invertebrate as an intermediate host and not to be directly transmitted.¹ To the best of our knowledge, this condition has not previously been diagnosed by sonography nor has treatment been documented.

In this case, three adult, female, Indonesian bottlenose dolphins (A, E and H) were being routinely monitored with sonography as part of a controlled breeding programme, with weekly scans of the ovaries and uterus being performed. The dolphins are maintained in concrete pools, with good water quality and fed A grade, human consumption quality, frozen fish. Dolphin A had been in the facility since 1987, dolphins E and H arrived in 1997.

The mammary glands overly the reproductive tract, and they are noticed at each ultrasonographic examination. In January 2001, dolphin E had given birth to a stillborn calf. At follow up sonography, it was noted that the mammary glands remained enlarged and, in fact, increased again in size. The lactiferous ducts were dilated and a single discrete lesion was noted in the underlying left abdominal muscle. The sonographic appearance at this time was suspicious of an old parasitic lesion, however, there was no evidence of eosinophilia or inflammation and the recent pregnancy allayed clinical suspicion. Following the stillbirth, dolphin E was housed with dolphin H and later, in June 2001, dolphin A joined the group. Shortly following this, both dolphins A and H developed enlarged mammary glands. Again confusing factors entered the picture, as dolphin A was temporarily reunited with a calf she had weaned in February 2001. Apparent attempts at nursing had been observed and her mammary enlargement was deemed to be a response to this. Dolphin H was then assumed to have begun spontaneous lactation as a response.

From June to December 2001, the gland size fluctuated from week to week in all three animals [VD diameter 1.8-3.4 cm]. During this time, dolphin H was observed to have two, small underlying muscle lesions with similar sonographic appearance to that in dolphin E. She also developed several small echogenic foci within the parenchyma of the left gland. No muscle lesions were identified in dolphin A and no lesions were seen in any other muscle in any animal. On two occasions, dolphin E had mild unexplained hepatic enzyme and bilirubin elevation. The muscle lesion in this animal also underwent changes in size and sonographic appearance. By this stage a pathologic cause was being considered, although milk samples did demonstrate an increased number of white blood cells on cytology, there were no conclusive findings on microbiological culture.

Ultrasonography of dolphin E, in January 2002, indicated an active, vermiform parasite inside the left main lactiferous duct. Milk samples collected at this time contained multiple ova, with dimensions 30 by 27.5 micrometers. The following week a similar parasite was observed in the left gland of dolphin A, who this time had both ova and suspected larvae in her milk sample. Samples from dolphin H were negative, despite evidence of intramammary and muscular lesions.

Definitive identification of the parasites is awaited. Treatment with ivermectin, fortnightly, at 200 micrograms/kg has been commenced. Response to therapy is being monitored by weekly ultrasonography and fortnightly milk samples. A comparison of milk composition with that of normally lactating females will also be undertaken.

References

1.  Geraci JR, Dailey MD, St. Aubin DJ. (1978). Parasitic mastitis in the Atlantic white-sided dolphin, Lagenorhyncus acutus, as a probable factor in herd productivity. Journal of the Fisheries Research Board of Canada 35:1350-1355.

2.  Dailey MD. (2001). Parasitic Diseases, in: CRC Handbook of Marine Mammal Medicine (2nd edition) Dierauf, L.A. & Gulland, F.M.D (Eds) 357-379. CRC Press LLC, USA.