Microplastics in marine mammals stranded around the British coast: ubiquitous but transitory?

Plastic pollution represents a pervasive and increasing threat to marine ecosystems worldwide and there is a need to better understand the extent to which microplastics (<5 mm) are ingested by high trophic-level taxa, such as marine mammals. Here, we perform a comprehensive assessment by examining whole digestive tracts of 50 individuals from 10 species whilst operating strict contamination controls. Microplastics were ubiquitous with particles detected in every animal examined. The relatively low number per animal (mean = 5.5) suggests these particles are transitory. Stomachs, however, were found to contain a greater number than intestines, indicating a potential site of temporary retention. The majority of particles were fibres (84%) while the remaining 16% was fragments. Particles were mainly blue and black (42.5% and 26.4%) in colour and Nylon was the most prevalent (60%) polymer type. A possible relationship was found between the cause of death category and microplastic abundance, indicating that animals that died due to infectious diseases had a slightly higher number of particles than those that died of trauma and other drivers of mortality. It is not possible, however, to draw any firm conclusions on the potential biological significance of this observation and further research is required to better understand the potential chronic effects of microplastic exposure on animal health, particularly as marine mammals are widely considered important sentinels for the implications of pollution for the marine environment.

Infection with Brucella ceti and high levels of polychlorinated biphenyls in bottlenose dolphins (Tursiops truncatus) stranded in south-west England.

Eight bottlenose dolphins (Tursiops truncatus) that stranded in Cornwall, south-west England, between June 2004 and December 2007 were examined using standardised postmortem examination and bacteriological methods. Evidence of Brucella species infection was found in four of these dolphins on culture. In addition, of the eight dolphins, four were positive and two were weakly positive for antibodies to Brucella species on serological analyses of pericardial and other fluids using a competitive ELISA and two indirect ELISAs. High or very high levels of the sum of 25 individual chlorobiphenyl congeners (∑25CBs) were also determined in blubber samples from two of the dolphins (45.5 and 446.6 mg/kg lipid weight).

True hermaphroditism: first evidence of an ovotestis in a cetacean species.

An immature unilateral hermaphrodite common dolphin (Delphinus delphis) was found stranded on the southwest coast of the UK. The external phenotype was that of a female, but internally there was one ovotestis, containing both ovarian follicles and testicular tubular elements, and a contralateral ovary. Ovarian portions of the ovotestis appeared normal and demonstrated follicular development, whereas the testicular tissue exhibited hypoplasia and degeneration. This is the first reported case of an ovotestis in a cetacean species.

Prevalence of a host-adapted group B Salmonella enterica in harbour porpoises (Phocoena phocoena) from the south-west coast of England.

A monophasic group B Salmonella enterica 4,12:a:- was first isolated in harbour porpoises (Phocoena phocoena) in Scotland in 1991. This paper reports the isolation of the same group B S enterica from harbour porpoise carcases found stranded along the Cornwall and Devon coastlines. Between 1991 and 2002, 80 harbour porpoises were submitted for postmortem examination and subjected to bacteriological examination under the UK Cetacean Strandings Investigation Programme. A total of 28 Salmonella isolates were recovered and subjected to several tests, including biochemical, molecular and serological analysis.

Postmortem evidence of interactions of bottlenose dolphins (Tursiops truncatus) with other dolphin species in south-west England.

Reports of violent interactions between bottlenose dolphins (Tursiops truncatus) and harbour porpoises (Phocoena phocoena) in the coastal waters of the UK are well documented. Examination of stranded cetaceans by the Cornwall Wildlife Trust Marine Strandings Network and the UK Cetacean Strandings Investigation Programme has indicated that seven animals, of four other species, found stranded in south-west England, had pathology consistent with bottlenose dolphin interaction, including two juvenile and two adult common dolphins (Delphinus delphis), one juvenile pilot whale (Globicephala melas), one juvenile Risso's dolphin (Grampus griseus) and one adult striped dolphin (Stenella coeruleoalba). Although recorded traumatic lesions were often not as severe as those found in harbour porpoises, it is probable that the interactions did contribute to stranding and/or death in all four of the juvenile animals examined. Furthermore, analysis of photographs taken before establishment of the Marine Strandings Network revealed rake (teeth) marks consistent with bottlenose dolphin interaction on one stranded common dolphin in 1992. A number of causes have been suggested for these interactions in harbour porpoises stranded in the UK and it is possible that any combination of these factors may also be implicated in the cases described in this report.

Mass-dependent predation risk and lethal dolphin-porpoise interactions.

In small birds, mass-dependent predation risk (MDPR) is known to make the trade-off between avoiding starvation and avoiding predation dependent on individual mass. This occurs because carrying increased fat reserves not only reduces starvation risk but also results in a higher predation risk due to reduced escape flight performance and/or the increased foraging exposure needed to maintain a higher body mass. In principle, the theory of MDPR could also apply to any animal capable of storing energy reserves to reduce starvation and whose escape performance decreases with increasing mass. We used a unique situation along certain parts of coastal Britain, where harbour porpoises (Phocoena phocoena) are pursued and killed but crucially not eaten by bottlenose dolphins (Tursiops truncatus), to investigate whether a MDPR effect can occur in non-avian species. We show that where high levels of dolphin 'predation' occur, porpoises carry significantly less energy reserves than would otherwise be expected and this equates to reducing by approximately 37% the length of time that a porpoise could survive without feeding. These results provide the first evidence that a mass-dependent starvation-predation risk trade-off may be a general ecological principle that can apply to widely different animal types rather than, as is currently thought, only to birds.

The 2000 canine distemper epidemic in Caspian seals (Phoca caspica): pathology and analysis of contributory factors.

More than 10,000 Caspian seals (Phoca caspica) were reported dead in the Caspian Sea during spring and summer 2000. We performed necropsies and extensive laboratory analyses on 18 seals, as well as examination of the pattern of strandings and variation in weather in recent years, to identify the cause of mortality and potential contributory factors. The monthly stranding rate in 2000 was up to 2.8 times the historic mean. It was preceded by an unusually mild winter, as observed before in mass mortality events of pinnipeds. The primary diagnosis in 11 of 13 seals was canine distemper, characterized by broncho-interstitial pneumonia, lymphocytic necrosis and depletion in lymphoid organs, and the presence of typical intracytoplasmic inclusion bodies in multiple epithelia. Canine distemper virus infection was confirmed by phylogenetic analysis of reverse transcriptase-polymerase chain reaction products. Organochlorine and zinc concentrations in tissues of seals with canine distemper were comparable to those of Caspian seals in previous years. Concurrent bacterial infections that may have contributed to the mortality of the seals included Bordetella bronchiseptica (4/8 seals), Streptococcus phocae (3/8), Salmonella dublin (1/8), and S. choleraesuis (1/8). A newly identified bacterium, Corynebacterium caspium, was associated with balanoposthitis in one seal. Several infectious and parasitic organisms, including poxvirus, Atopobacter phocae, Eimeria- and Sarcocystis-like organisms, and Halarachne sp. were identified in Caspian seals for the first time.

The relationship between polychlorinated biphenyls in blubber and levels of nematode infestations in harbour porpoises, Phocoena phocoena.

Post-mortem examinations of harbour porpoises, Phocoena phocoena, regularly reveal heavy parasitic worm burdens. These same post-mortem records show varying levels of polychlorinated biphenyls (PCBs) accumulating in the blubber of porpoises. Although a number of papers have documented geospatial and temporal changes of PCBs and their detrimental effects on marine mammal health, as yet none have examined their role in determining nematode burdens in wild marine mammal populations. Using a data set consisting of harbour porpoises stranded in the UK between 1989 and 2002, we found a significant, positive association between PCB levels and nematode burdens, although the nature of the relationship was confounded with porpoise sex, age and cause of death. It was also apparent that individuals with the heaviest infestations of nematodes did not have the highest PCB level: while PCBs are important, they are clearly not the sole determinants of nematode burdens in wild populations of the harbour porpoise around the UK.

Acute and chronic gas bubble lesions in cetaceans stranded in the United Kingdom.

The first evidence suggestive of in vivo gas bubble formation in cetacea, including eight animals stranded in the UK, has recently been reported. This article presents the pathologic findings from these eight UK-stranded cetaceans and two additional UK-stranded cetacean cases in detail. Hepatic gas-filled cavitary lesions (0.2-6.0 cm diameter) involving approximately 5-90% of the liver volume were found in four (two juvenile, two adult) Risso's dolphins (Grampus griseus), three (two adult, one juvenile) common dolphins (Delphinus delphis), an adult Blainville's beaked whale (Mesoplodon densirostris), and an adult harbour porpoise (Phocoena phocoena). Histopathologic examination of the seven dolphin cases with gross liver cavities revealed variable degrees of pericavitary fibrosis, microscopic, intrahepatic, spherical, nonstaining cavities (typically 50-750 microm in diameter) consistent with gas emboli within distended portal vessels and sinusoids and associated with hepatic tissue compression, hemorrhages, fibrin/organizing thrombi, and foci of acute hepato-cellular necrosis. Two common dolphins also had multiple and bilateral gross renal cavities (2.0-9.0 mm diameter) that, microscopically, were consistent with acute (n = 2) and chronic (n = 1) arterial gas emboli-induced renal infarcts. Microscopic, bubblelike cavities were also found in mesenteric lymph node (n = 4), adrenal (n = 2), spleen (n = 2), pulmonary associated lymph node (n = 1), posterior cervical lymph node (n = 1), and thyroid (n = 1). No bacterial organisms were isolated from five of six cavitated livers and one of one cavitated kidneys. The etiology and pathogenesis of these lesions are not known, although a decompression-related mechanism involving embolism of intestinal gas or de novo gas bubble (emboli) development derived from tissues supersaturated with nitrogen is suspected.

Smooth muscle actin and vimentin as markers of testis development in the harbour porpoise (Phocoena phocoena).

Testicular development in the harbour porpoise Phocoena phocoena was examined using animals (n = 192) stranded or by-caught off the coast of England, Wales and Scotland. Classification of animals according to their stage of sexual development was undertaken using gonadal morphology and the distribution of cytoskeletal proteins. Smooth muscle actin (SMA) and vimentin proved particularly useful in this respect; SMA was prominent in the myoid peritubular cells of the adult testis, and two stages of peritubular cell SMA expression could be recognized ('absent' or 'incomplete'). The initial appearance of SMA in peritubular cells was associated with significant increases in body length and body weight (P < 0.001), and occurred during the second year of life. Vimentin, which was prominent in prespermatogonia and spermatogonia, sometimes showed a polarized cytoplasmic distribution. This correlated with a developmental stage at which the seminiferous tubule epithelium becomes populated by germ cells (mean age 1.8 years). Several antibodies were tested for their utility as Sertoli cell markers, but none was found to be specific or useful. Nevertheless, immunohistochemical localization of desmin, GATA-4, Ki67 and androgen receptor was possible despite the poor quality of tissue preservation. This study showed that immunohistochemical classification of these individuals provides a robust basis for the recognition of key physiological stages of sexual development in the male harbour porpoise. This may provide an alternative to the estimation of age, body weight and body length in future analyses aimed at detecting possible adverse effects of environmental pollutants on the reproductive potential of wild marine mammals.

Odorant receptor gene expression changes during the parr-smolt transformation in Atlantic salmon.

The ability of salmon to home accurately to their natal stream to spawn has long intrigued biologists and has important consequences for the maintenance of population structure in these species. It is known that olfaction is crucial to homing, and that the transition from the freshwater to the marine environment (the parr-smolt transformation; PST) is a period of increased olfactory sensitivity and learning, resulting in a permanent memory of natal site odours that is retained, at least in part, in peripheral sensory neurones. These odours are then used as cues by sexually maturing fish on their homeward migration. We used quantitative polymerase chain reaction techniques to demonstrate transient increases in expression of odorant receptor transcripts (of up to fifty-fold over pre-PST levels) coincident with PST. Both olfactory (SORB) and vomeronasal receptors (SVRA and SVRC) are involved, which suggests that the fish learn both environmental odours and semiochemicals (pheromones). Receptor expression varies between families and changes over time indicating both genetic differences in odour stimuli and multiple periods of olfactory sensitivity. We suggest that changes in OR gene expression may have a role in homing behaviour and thus the maintenance of population structure in Atlantic salmon.

Mass die-Off of Caspian seals caused by canine distemper virus.

Thousands of Caspian seals (Phoca caspica) died in the Caspian Sea from April to August 2000. Lesions characteristic of morbillivirus infection were found in tissue specimens from dead seals. Canine distemper virus infection was identified by serologic examination, reverse transcriptase- polymerase chain reaction, and sequencing of selected P gene fragments. These results implicate canine distemper virus infection as the primary cause of death.

Genetic structure of fragmented populations of red squirrel (Sciurus vulgaris) in the UK.

The relationships among 207 squirrels from 12 locations in the UK and three in mainland Europe were examined using mitochondrial DNA (mtDNA) control region sequence. Twenty-six haplotypes were detected, many of which were population specific. Eighty per cent of the populations analysed contained two or more haplotypes. Hierarchical analysis of molecular variance showed the majority of genetic variation to be partitioned among populations. Genetic diversity varied considerably within the UK, and conformed to no obvious geographical trend. The populations in Argyll and Spadeadam Forest showed the highest levels of variation in the UK. However, the greatest genetic diversity was seen in Bavaria, southern Germany where six unique alleles were detected in a sample of 10 individuals. Phylogenetic analysis revealed no evolutionary divergence between UK and mainland European haplotypes. We conclude that, within the UK, the genetic patterns observed are most likely to be explained by the effects of genetic drift which has occurred since the isolation of populations during the past few hundred years, hence we cannot detect any underlying phylogeographic pattern. Therefore, the use of larger, geographically distinct populations within the UK for augmentation of small isolated populations is unlikely to pose problems of genetic incompatibility. Further, the role that demographic factors may have in complicating the application of current genetically based management unit criteria is likely to need further attention.

Virological, biochemical and histological effects of human lymphoblastoid interferon in Swedish patients with chronic hepatitis C.

Thirty-eight Swedish patients with chronic hepatitis C were randomly assigned to receive either 3 million units (MU) or 5 MU of human lymphoblastoid interferon-alpha-n1 (Wellferon) three times per week for either 6 or 12 months. The patients were monitored biochemically, histologically and by quantitative polymerase chain reaction for circulating HCV RNA, during therapy and for the following year. Overall, 22 (58%) of the patients lost detectable hepatitis C virus (HCV) viraemia during therapy but eight of these patients relapsed during follow-up, leaving 14 (37%) sustained responders. Patients infected with HCV non-type 1 genotypes were significantly more likely to achieve a sustained response than were those infected with HCV type 1 (63% vs 10.5%, P = 0.001). Sustained virological responses were also associated with lower pretreatment viraemia level, younger age, absence of cirrhosis and the higher interferon dosage regimens but these associations failed to reach statistical significance. In 97% of patients there was concordance between virological and biochemical responses, and a statistically significant (P = 0.005) improvement in the Knodell histological activity index was observed in the virological sustained responders.

Acute hepatitis C viral infection during pregnancy: failure of mother to infant transmission.

A pregnant woman developed an acute hepatitis C virus (HCV) type 3a infection during the second trimester of pregnancy. The clinical virological features are presented, including HCV RNA quantification of maternal serum samples collected during pregnancy. These findings are discussed in light of the child's remaining uninfected after 5 years of follow-up.

Analysis of clinical and virological factors associated with response to alpha interferon therapy in chronic hepatitis C.

Interferon alpha (IFN-alpha) therapy is currently the treatment of choice for chronic hepatitis C (HCV) infection, but it fails to achieve a sustained response in approximately 75% of those treated. The factors which determine whether or not an individual will respond to IFN-alpha are uncertain, although a number of potentially predictive factors have been proposed. In this study a wide range of clinical, demographic, and virological parameters were evaluated in relation to therapeutic outcome in a group of 30 Italian patients with chronic hepatitis C. All patients received 3 MU leukocyte-derived IFN-alpha three times a week for 6 months and were then followed prospectively for at least 12 months. 53% of patients responded initially, but a sustained response was observed in only 17%. Responders were found to be significantly younger than nonresponders (45.6 +/- 3.1 vs. 55.4 +/- 2.7), and less frequently cirrhotic (2/16 vs. 7/14). Sustained responders had a mean pretreatment HCV-RNA titer approximately tenfold lower than that of those who did not have a sustained response, but the difference was not statistically significant. HCV genotype was found to be significantly associated with both initial and sustained response. Patients infected with HCV-2a were more likely to respond (89%) than those who were infected with HCV-1b (37%), and they were also more likely to sustain that response (33% vs. 6%).(ABSTRACT TRUNCATED AT 250 WORDS)

A pilot study of combination therapy with ribavirin plus interferon alfa for interferon alfa-resistant chronic hepatitis C.

BACKGROUND/AIMS: In chronic hepatitis C, interferon alfa (IFN-alpha) therapy fails to achieve a sustained response in approximately 75% of patients. Similarly, ribavirin induces only a transient response. The aim of this study was to evaluate whether ribavirin and IFN-alpha in combination could be effective in IFN-alpha-resistant chronic hepatitis C. METHODS: Twenty patients with chronic hepatitis C resistant to a previous course of IFN-alpha were randomly assigned to receive either ribavirin combined with IFN-alpha or IFN-alpha alone for 6 months. RESULTS: Serum alanine aminotransferase levels decreased significantly during therapy in both treatment groups, but after therapy, the levels remained significantly decreased only in the combination therapy group. Nine months after treatment, sustained normalization of aminotransferase levels, associated with sustained loss of serum hepatitis C virus RNA, was observed in 40% of the patients in the combination therapy group but in none of the patients treated with IFN-alpha alone (P < 0.05). The sustained response was accompanied by reduced hepatic necroinflammatory activity on biopsy. CONCLUSIONS: These findings suggest that ribavirin plus IFN-alpha combination therapy is able to induce a sustained biochemical and virological response in a significant proportion of patients with IFN-alpha-resistant chronic hepatitis C.