Bacteriological and histopathological findings in cetaceans that stranded in the Philippines from 2017 to 2018

The relatively high frequency of marine mammal stranding events in the Philippines provide many research opportunities. A select set of stranders (n = 21) from 2017 to 2018 were sampled for bacteriology and histopathology. Pertinent tissues and bacteria were collected from individuals representing eight cetacean species (i.e. Feresa attenuata, Kogia breviceps, Globicephala macrorhynchus, Grampus griseus, Lagenodelphis hosei, Peponocephala electra, Stenella attenuata and Stenella longirostris) and were subjected to histopathological examination and antibiotic resistance screening, respectively. The antibiotic resistance profiles of 24 bacteria (belonging to genera Escherichia, Enterobacter, Klebsiella, Proteus, and Shigella) that were isolated from four cetaceans were determined using 18 antibiotics. All 24 isolates were resistant to at least one antibiotic class, and 79.17% were classified as multiple antibiotic resistant (MAR). The MAR index values of isolates ranged from 0.06 to 0.39 with all the isolates resistant to erythromycin (100%; n = 24) and susceptible to imipenem, doripenem, ciprofloxacin, chloramphenicol, and gentamicin (100%; n = 24). The resistance profiles of these bacteria show the extent of antimicrobial resistance in the marine environment, and may inform medical management decisions during rehabilitation of stranded cetaceans. Due to inadequate gross descriptions and limited data gathered by the responders during the stranding events, the significance of histopathological lesions in association with disease diagnosis in each cetacean stranding or mortality remained inconclusive; however, these histopathological findings may be indicative or contributory to the resulting debility and stress during their strandings. The findings of the study demonstrate the challenges faced by cetacean species in the wild, such as but not limited to, biological pollution through land-sea movement of effluents, fisheries interactions, and anthropogenic activities.

Novel cetacean morbillivirus in a rare Fraser’s dolphin (Lagenodelphis hosei) stranding from Maui, Hawai‘i

Cetacean morbillivirus (CeMV) is a global threat to cetaceans. We report a novel morbillivirus from a Fraser’s dolphin (Lagenodelphis hosei) that stranded in Maui, Hawaii in 2018 that is dissimilar to the beaked whale morbillivirus previously identified from Hawaii and to other CeMV strains. Histopathological findings included intranuclear inclusions in bile duct epithelium, lymphoid depletion, rare syncytial cells and non-suppurative meningitis. Cerebellum and lung tissue homogenates were inoculated onto Vero.DogSLAMtag cells for virus isolation and cytopathic effects were observed, resulting in the formation of multinucleated giant cells (i.e., syncytia). Transmission electron microscopy of infected cell cultures also revealed syncytial cells with intracytoplasmic and intranuclear inclusions of viral nucleocapsids, consistent with the ultrastructure of a morbillivirus. Samples of the cerebellum, lung, liver, spleen and lymph nodes were positive for morbillivirus using a reverse transcription-polymerase chain reaction. The resulting 559 bp L gene sequence had the highest nucleotide identity (77.3%) to porpoise morbillivirus from Northern Ireland and the Netherlands. The resulting 248 bp P gene had the highest nucleotide identity to porpoise morbillivirus in Northern Ireland and the Netherlands and to a stranded Guiana dolphin (Sotalia guianensis) in Brazil (66.9%). As Fraser’s dolphins are a pelagic species that infrequently strand, a novel strain of CeMV may be circulating in the central Pacific that could have additional population impacts through transmission to other small island-associated cetacean species.

Parasitic Anisakid Nematode Isolated from Stranded Fraser’s Dolphin (Lagenodelphis hosei Fraser, 1956) from Central Philippine Waters

Cetaceans, including dolphins, serve as definitive hosts of zoonotic anisakid nematodes, which are important etiological agents for human anisakiasis and allergy-associated health risks. With limited knowledge of these zoonotic parasites from the marine environment in the Philippine waters, the stranding of a Fraser’s dolphin (Lagenodelphis hosei Fraser, 1956) off the central Philippines made it possible to identify the worm species isolated from its gut. Parasitological examinations were carried out using morphological and molecular tools. Morphologically, the SEM and LM data revealed that the specimens belong to the genus Anisakis of the Type 1 group. Molecularly, PCR-RFLP results of the ITS region generated only a single fragment pattern on all worm samples corresponding to the reported molecular keys for A. typica. Further sequence and phylogenetic analyses of both ITS rDNA and mtDNA COX2 genes confirmed the anisakid nematodes’ identity as A. typica. The molecular data obtained in this study support previous findings on the possible existence of local variants of A. typica in this region.

Bacteriological and histopathological findings in cetaceans that stranded in the Philippines from 2017 to 2018

The relatively high frequency of marine mammal stranding events in the Philippines provide many research opportunities. A select set of stranders (n=21) from 2017 to 2018 were sampled for bacteriology and histopathology. Pertinent tissues and bacteria were collected from eight species (i.e. Feresa attenuata, Kogia breviceps, Globicephala macrorhynchus, Grampus griseus, Lagenodelphis hosei, Peponocephala electra, Stenella attenuata and Stenella longirostris) and were subjected to histopathological examination and antibiotic resistance screening, respectively. Lesions that were observed in tissues of 19 cetaceans include congestion, hemorrhage, edema, hemosiderosis, glomerulopathy, Zenker’s necrosis, atrophy, atelectasis, and parasitic cysts. These lesions may be associated with factors possibly contributing to the death, debility, and stress of the animals during their strandings. On the other hand, the resistance profiles of 24 bacteria (belonging to genera Escherichia, Enterobacter, Klebsiella, Proteus, and Shigella) that were isolated from four cetaceans were determined using 18 antibiotics. All 24 isolates were resistant to at least one antibiotic class, and 79.17% were classified as multiple antibiotic resistant (MAR). The MAR index values of isolates ranged from 0.06 to 0.39 with all the isolates resistant to erythromycin (100%; n=24) and susceptible to imipenem, doripenem, ciprofloxacin, chloramphenicol, and gentamicin (100%; n=24). The resistance profiles of these bacteria can be used as basis for selecting antibiotics needed in the medical management of stranded cetaceans that need to be rehabilitated. Overall, the histopathological and bacteriological findings of the study demonstrate the challenges faced by cetacean species in the wild, such as but not limited to, biological pollution through land-sea movement of effluents, fisheries interactions, and anthropogenic activities.

Population genetic diversity and historical dynamics of Fraser’s dolphins Lagenodelphis hosei

Marine organisms face relatively few barriers to gene flow, and yet even highly mobile species such as dolphins often show population structure over regional geographic scales. Understanding the processes that promote this pattern of differentiation helps us understand the evolutionary radiation of this group, and to promote more effective measures for conservation. Here we report the first population genetic study of Fraser’s dolphin Lagenodelphis hosei (Fraser, 1956), a species that was not recognized by the scientific communities until the early 1970s. We use 18 microsatellite DNA loci and 1 mitochondrial DNA (mtDNA) locus to compare 112 Fraser’s dolphins collected in various locations, mainly from the waters off Japan, Taiwan, and the Philippines, but also including samples from the Gulf of Mexico and Caribbean Sea. Our results indicate differentiation between populations in waters off Japan, Taiwan, and the Philippines, and support the findings from earlier morphological assessments for differentiation between Japanese and Philippine waters. Small sample sets also show likely differentiation between other regions in the North Pacific and North Atlantic Oceans. Moreover, neutrality tests and mismatch analysis based on mtDNA data indicate that the populations in the western North Pacific Ocean have expanded demographically and spatially, possibly since the latest global deglaciation, when sea levels and global temperatures started to rise.

The status and trends of small cetacean landings at Dixcove artisanal fishing port, western Ghana

One of the largest documented takes of small cetaceans in western Africa occurs in Western regional coastal waters of Ghana. This temporally coincided with steadily decreasing catches of finfish, especially small pelagics (sardinellas, anchovies, mackerel) over the past decades, attributed to both climate change and indiscriminate exploitation methods. Dixcove, a key fishing port for cetacean landings was surveyed during 96 days between 12 September -17 December 2018. Our goal was to update insights from our earlier surveys, especially on catch rates, catch per unit effort and species composition. A total of 57 delphinids of 10 species were observed landed: Stenella attenuata (28.1%), Stenella clymene (17.5%), Lagenodelphis hosei (10.5%), Steno bredanensis (10.5%), unidentified stenellids (8.8%), Grampus griseus (3.5%), Delphinus sp. (3.5%), Pseudorca crassidens (3.5%) and single specimens of Tursiops truncatus, Stenella longirostris and Stenella frontalis. The observed cetacean catch per diem (cpd =0.59) at Dixcove was low compared to earlier rates for this port (e.g. cpd =2.82, in 2013-2014). However, fishing effort, measured as the number of canoes landing per diem (range 0-25; mean= 8.82 ± 6.05; n=22) was also reduced. Poor fish catches forced many canoes to remain in port. The prevalence in landings of common bottlenose dolphins and common dolphins has significantly decreased in the period 2000-2018. The prevalence of Fraser's dolphins and false killer whales increased. Indications are that a higher proportion of cetacean carcasses may be utilised offshore as shark bait. Hooks baited with cetacean parts are deployed in auxiliary longlines set longside large-mesh drift gillnets with a shark aggregating purpose, a first report in Africa. Shore-based incidental sightings of humpback whales suggest the potential for small scale whale-watching ecotourism in Ghanaian coastal waters, as pertains in the nearby waters of the Republic of Benin.

The status and trends of small cetacean landings at Dixcove artisanal fishing port, western Ghana

One of the largest documented takes of small cetaceans in western Africa occurs in Western regional coastal waters of Ghana. This temporally coincided with steadily decreasing catches of finfish, especially small pelagics (sardinellas, anchovies, mackerel) over the past decades, attributed to both climate change and indiscriminate exploitation methods. Dixcove, a key fishing port for cetacean landings was surveyed during 96 days between 12 September -17 December 2018. Our goal was to update insights from our earlier surveys, especially on catch rates, catch per unit effort and species composition. A total of 57 delphinids of 10 species were observed landed: Stenella attenuata (28.1%), Stenella clymene (17.5%), Lagenodelphis hosei (10.5%), Steno bredanensis (10.5%), unidentified stenellids (8.8%), Grampus griseus (3.5%), Delphinus sp. (3.5%), Pseudorca crassidens (3.5%) and single specimens of Tursiops truncatus, Stenella longirostris and Stenella frontalis. The observed cetacean catch per diem (cpd =0.59) at Dixcove was low compared to earlier rates for this port (e.g. cpd =2.82, in 2013-2014). However, fishing effort, measured as the number of canoes landing per diem (range 0-25; mean= 8.82 ± 6.05; n=22) was also reduced. Poor fish catches forced many canoes to remain in port. The prevalence in landings of common bottlenose dolphins and common dolphins has significantly decreased in the period 2000-2018. The prevalence of Fraser's dolphins and false killer whales increased. Indications are that a higher proportion of cetacean carcasses may be utilised offshore as shark bait. Hooks baited with cetacean parts are deployed in auxiliary longlines set longside large-mesh drift gillnets with a shark aggregating purpose, a first report in Africa. Shore-based incidental sightings of humpback whales suggest the potential for small scale whale-watching ecotourism in Ghanaian coastal waters, as pertains in the nearby waters of the Republic of Benin.