Eighteen-Year Study of South Australian Dolphins Shows Variation in Lung Nematodes by Season, Year, Age Class, and Location

Abstract

ABSTRACT:Between 1990 and 2007, carcasses of opportunistically collected short-beaked common dolphins (Delphinus delphis; n5238), Indo-Pacific bottlenose dolphins (Tursiops aduncus; n5167), and common bottlenose dolphins (Tursiops truncatus; n515) were examined for parasites and life history data. Three species of lung nematodes (Halocercus lagenorhynchi, Stenurus ovatus, Pharurus alatus) were identified in surface nodules, subsurface lesions, or airways. Nematode burdens were light to heavy and, in many cases, would have compromised the dolphins' health. The number of dolphins infected was related to species, year, season, age class, and geographic region. Nematodes were found in all three species but were more prevalent in short-beaked common dolphins (mean annual prevalence526%) than in bottlenose dolphins (12%). There was a significant increase in prevalence of nematodes in short-beaked common dolphins in 2005-06 (63%) compared to 1990-2004 (14%), with a peak in April-June. More young short-beaked common dolphins were infected than subadults and adults and, during the unusual infection event, there were more dependent calves (,130 cm) than juveniles. There were also more infections in dependent bottlenose dolphin (Tursiops spp.) calves but no increase in overall prevalence was detected during 2005-06. Because neonates of both short-beaked common dolphins and bottlenose dolphins were infected, mother-to-calf transmission is suspected for these species in South Australia. Numbers of infections in short-beaked common dolphins were higher in Gulf St Vincent than elsewhere in South Australia, particularly in 2005-06. The cause of the unusual infection event in short-beaked common dolphins is unknown. We discuss the influence of dolphin diet, life history, and external factors.

Population- and growth-related differences in helminthic fauna of finless porpoises (<i>Neophocaena asiaeorientalis</i>) in five Japanese populations

“…The present study also supports this possibility. Such vertical transmission has also been suspected during H. lagenorhynchi infection of the bottlenose dolphin ( Tursiops truncatus ) [8, 10] and the common dolphin ( D. delphis ) [35]. If the vertical transmission hypothesis is true, it is strange that H. pingi is almost not found in >110 cm porpoises.…”

Şişe Burunlu Bir Yunusta (Tursiops truncatus) Patolojik ve Parazitolojik İncelemeler

“…In one study, the prevalence of lungworm infections was determined to be 77% in the stranded bottlenose dolphins [15] . To date, Stenurus ovatus, Halocercus lagenorhynchi, Pharurus alatus, and Skrjabinalius cryptocephalus related verminous pneumonia [1,15,16] was reported in the bottlenose dolphins; but there was no case related to S. minor. It is reported that the prevalence of S. minor infection of harbor dolphins on the coast of Norway, Iceland, Greenland and South America was 66-100% [17,18] .…”

“…However, little information is known about the role parasites in the deaths and strandings of dolphins [1] . Lungworms (Metastrongyloidea: Pseudaliidae) have been implicated as the main factor of natural mortality of dolphins [2] .…”

Wildlife parasitology in Australia: past, present and future

“…Since then, the parasites of phocids (seals and sea-lions) have been further investigated, primarily due to pup mortality caused by the hookworm Uncinaria sanguinis (see Marcus et al 2014), while the potential pathological impact of the lungworms Parafilaroides normani and the gastric ascaridoid Contraceacum ogmorhini remain to be determined (Arundel 1978;Nicholson and Fanning 1981;Ladds 2009). There has been little published on the parasites of cetaceans apart from a study of the lungworms of dolphins and their pathological significance (Tomo et al 2010). A review of the helminth parasites causing disease in cetaceans, pinnipeds and the dugong has been published by Ladds (2009).…”