Occurrence of anthropozoonotic parasitic infections and faecal microbes in free-ranging sperm whales (Physeter macrocephalus) from the Mediterranean Sea

Potential Fungal Zoonotic Pathogens in Cetaceans: An Emerging Concern

Over 60% of emerging infectious diseases in humans are zoonotic, often originating from wild animals. This long-standing ecological phenomenon has accelerated due to human-induced environmental changes. Recent data show a significant increase in fungal infections, with 6.5 million cases annually leading to 3.7 million deaths, indicating their growing impact on global health. Despite the vast diversity of fungal species, only a few are known to infect humans and marine mammals. Fungal zoonoses, especially those involving marine mammals like cetaceans, are of global public health concern. Increased human-cetacean interactions, in both professional and recreational settings, pose risks for zoonotic disease transmission. This review focuses on the epidemiology, clinical manifestations, and zoonotic potential of major fungal pathogens shared in humans and cetaceans, highlighting their interspecies transmission capability and the challenges posed by antifungal resistance and environmental changes. It underscores the need for enhanced awareness and preventative measures in high-risk settings to protect public health and marine ecosystems.

Identification and prevalence investigation of cyathocotylid trematode (Trematoda: Digenea: Cyathocotylidae) in Carassius auratus in Wuhu, China

The family Cyathocotylidae trematode is a world-widely distributed parasite whose adults are mainly found in fish, reptiles, birds, and mammals in both freshwater and marine environments. However, little is known of the prevalence of these trematode in China. For the first time, we found Cyathocotylidae trematode in the Wuhu area. Therefore, we investigated the prevalence of metacercariae in Carassius auratus from Zhang Lake, Kui Lake, Qingyi River, and Yangtze River (Wuhu Section) in Wuhu area. A total of 392 one-year-old C. auratus were tested in January, April, July, and October 2019, respectively. After the fish were euthanized, the back, chest, and tail muscles were used for preliminary screening for the presence of metacercariae by direct compression method. Metacercariae were isolated by the artificial digestion method and then morphologically and molecularly identified by cox1 (642 bp) and ITS2 (418 bp) sequences amplification by PCR. Based on morphological features and sequence analysis, they were identified as cyathocotylid metacercariae. The four water sources have different degrees of prevalence throughout the year, the prevalence ranges from 28.45% (29/102) in Yangtze River to 50.55% (46/91) in Zhang Lake, with an average prevalence of 40.56% (159/392). There were also differences in the prevalence in different months: The highest occurred in July, which was 81.63% (80/98), while the lowest occurred in January, which was 8.89% (8/90). This study can provide basic data for the prevention and control of cyathocotylid trematode in this area.

Dolphins and sea turtles may host zoonotic parasites and pathogenic bacteria as indicators of anthropic pressure in the Gulf of Taranto (Northern Ionian Sea, Central-Eastern Mediterranean Sea)

The occurrence of protozoan parasites Giardia duodenalis and Cryptosporidium spp. such as the pathogenic bacteria Salmonella spp. and Escherichia coli was molecularly investigated in the following free ranging species of striped dolphins (Stenella coeruleoalba), Risso's dolphins (Grampus griseus) as well as loggerhead (Caretta caretta) and green (Chelonia mydas) sea turtles living in the Gulf of Taranto (Mediterranean Sea). Out of forty-one investigated individuals belonging to the 4 species, 13 (31.7%) were positive to one or more pathogens and zoonotic G. duodenalis assemblage A, Cryptosporidium parvum and S. enterica were identified in striped dolphins, loggerhead and green sea turtles. In this work, the presence of these opportunistic pathogens has been investigated in fecal samples of free ranging dolphin and sea turtle species for the first time. Moreover, this is the first record of C. parvum in loggerhead sea turtles. These results may provide baseline data for the potential role of cetaceans and sea turtles as potential sentinel species for zoonotic and terrestrial pathogens in the marine environment.

A Comparative Study of Mini-FLOTAC With Traditional Coprological Techniques in the Analysis of Cetacean Fecal Samples

Free-ranging cetaceans are considered sentinels for the marine ecosystem's health. New and non-invasive methods have been set up for the collection of fecal samples from free-ranging big whales at sea, permitting to gain an excellent epidemiological picture of parasitic infections in wild populations. To select the best protocol to be used for copromicroscopic examination in cetaceans stool samples, we evaluated the sensitivity of two commonly used techniques, i.e., a sedimentation-floatation method and the Mini-FLOTAC through validation by helminth isolation from the digestive tract. For this aim, gastrointestinal content and fecal samples were collected during necropsy from 44 cetaceans, including bottlenose dolphins (Tursiops truncatus), striped dolphins (Stenella coeruleoalba), sperm whales (Physeter macrocephalus), Risso's dolphins (Grampus griseus), Cuvier's beaked whales (Ziphius cavirostris), pilot whale (Globicephala melas), and fin whales (Balaenoptera physalus). Helminths were recovered through washing and filtering of the gastrointestinal contents and morphologically identified. Copromicroscopic examinations were performed on formalin-preserved fecal samples, using a sodium nitrate, sodium thiosulphate, and sucrose solution (s.g. = 1.450) for both methods. Helminths belonging to 9 taxa (i.e., the trematodes Synthesium tursionis, Synthesium delamurei, Campula palliata, Braunina cordiformis, Pholeter gastrophilus, the nematode Anisakis sp., cestodes of the family Tetrabothriidae and the acanthocephalan Bolbosoma sp.) were isolated. Eggs referable to the same taxa, with the exception of cestodes, were found in copromicroscopic analyses. Sensitivity of the Mini-FLOTAC method appeared higher or equal for all taxa, proving superior to the sedimentation-flotation method for the detection of all except Anisakis sp. The concordance of the two tests indeed revealed a moderate to perfect agreement (kappa values 0.42–1). Not excluding the limitations inherent to the techniques themselves, explanations for false-negative results at copromicroscopy could be linked to parasite-related factors, including prepatent infections, low parasitic burdens, or intermittent egg shedding. Notwithstanding these limitations, this study evidenced that the Mini-FLOTAC protocol approximates more accurately the composition of the gastrointestinal helminthic community of cetaceans from copromicroscopic examination, providing at the same time a quantitative estimation.

First Report of the Parasitic Nematode Pseudoterranova spp. Found in Mediterranean Monk Seal (Monachus monachus) in Greece: Conservation Implications

The Mediterranean monk seal (Monachus monachus) is classified as an endangered species by the IUCN, with a global population that does not exceed 800 individuals. There is limited understanding around the biology and health status of the species, rendering possible parasitic infections grave for its conservation efforts. The aim of the current study was the molecular identification of a parasitic nematode found in the digestive system of a sub-adult Mediterranean monk seal individual, that was found stranded in the area of Pagasitikos Gulf, Greece in 2019. Analysis of the stomach contents revealed the presence of two intact female nematode individuals. Standard protocols were followed as DNA extraction of the parasites was conducted and PCR amplification of the cytochrome oxidase subunit I (COI) mitochondrial gene was implemented. Sequencing analysis of a 585 bp-amplified product displayed a 96% similarity of the screened nematodes to the Pseudoterranova bulbosa species. Bayesian inference was implemented for the subsequent tree reconstruction. The phylogenetic tree revealed a clear genetic similarity between our parasitic nematode individuals named as Pseudoterranova spp. and Pseudoterranova bulbosa (bootstrap value: 82%), which is indicated for the first and only time as such, to be found in the waters of the Mediterranean Sea and also in the stomach of a Mediterranean monk seal.

A Preliminary Comparison on Faecal Microbiomes of Free-Ranging Large Baleen (Balaenoptera musculus, B. physalus, B. borealis) and Toothed (Physeter macrocephalus) Whales

Large baleen and toothed whales play crucial ecological roles in oceans; nonetheless, very little is known about their intestinal microbiomes. Based on striking differences in natural history and thus in feeding behaviours, it can be expected that intestinal microbiomes of large baleen whales and toothed whales are different. To test this hypothesis, the phylogenetic composition of faecal microbiomes was investigated by a 16S rRNA gene amplicon sequence-based approach for Bacteria and Archaea. Faecal samples from free-ranging large whales collected off the Azores Archipelago (Portugal) were used, comprising 13 individual baleen whales (one sei, two blue and ten fin whales) and four sperm whales. The phylogenetic composition of the Bacteria faecal microbiomes of baleen and toothed whales showed no significant differences at the phylum level. However, significant differences were detected at the family and genus levels. Most abundant phyla were Firmicutes, Bacteroidetes, Proteobacteria, Tenericutes and Spirochaeta. Few highly abundant bacterial genera were identified as key taxa with a high contribution to differences among baleen and toothed whales microbiomes. Only few archaeal sequences were detected, primarily Methanomassiliicoccales representing potential methanogenic Archaea. This is the first study that directly compares the faecal bacterial and archaeal microbiomes of free-ranging baleen and toothed whales which represent the two parvorders of Cetacea which members are fully aquatic large mammals which were evolutionary split millions of years ago.

Endoparasitic Insights of Free-Living Fin (Balaenoptera physalus), Humpback (Megaptera novaeangliae) and North Atlantic Right Whales (Eubalaena glacialis) from Eastern Canadian Waters

Purpose

To date, little is still known on parasite infections affecting free-living large whale populations worldwide. Data presented should be considered as a baseline study for future monitoring surveys on endoparasites affecting whales, thereby enhancing investigations on impacts of zoonotic parasitoses not only on vulnerable or endangered baleen whale population health but also on public health.

Methods

The presented study is a first report on gastrointestinal parasites infecting different free-living baleen whales inhabiting East Canadian waters using non-invasive methods. Individual faecal samples from fin (n = 3; Balaenoptera physalus), humpback (n = 4; Megaptera novaeangliae) and North Atlantic right whales (n = 1; Eubalaena glacialis) were collected without animal disturbance, within their natural habitats on an ecological expedition during annual surveys in summer 2017. Faecal samples were assessed by standardized diagnostic methods, such as sodium acetate acetic formalin (SAF) technique, carbol fuchsin-stained faecal smears, Giardia/Cryptosporidium coproantigen ELISAs and were applied for further identification.

Results

Parasitological infections included three different potentially zoonotic parasite species, one protozoa (Entamoeba spp.) and two metazoans (Diphyllobothriidae gen. sp., Ascaridida indet.). No positive Giardia/Cryptosporidium coproantigen ELISA could be found in the studied whales.

Conclusion

This study adds to the current knowledge of intestinal and zoonotic parasite infections of vulnerable to partly endangered free-ranging baleen whales. Only few or no parasitological studies exist for these whale species, usually dealing with only one dead specimen. We call for more research in this field especially for the importance of conservation of free-living marine mammals using non-invasive methods.

Wild whale faecal samples as a proxy of anthropogenic impact

The occurrence of protozoan parasite, bacterial communities, organic pollutants and heavy metals was investigated in free-ranging species of fin (Balaenoptera physalus, n. 2) and sperm (Physeter macrocephalus, n. 2) whales from the Pelagos Sanctuary, Corsican-Ligurian Provencal Basin (Northern-Western Mediterranean Sea). Out of four faecal samples investigated, two from fin whales and one from sperm whale were found positive to Blastocystis sp. A higher number of sequences related to Synergistetes and Spirochaetae were found in sperm whales if compared with fin whales. Moreover, As, Co and Hg were found exclusively in sperm whale faecal samples, while Pb was found only in fin whale faecal samples. The concentration of both PAH and PCB was always below the limit of detection. This is the first report in which the presence of these opportunistic pathogens, bacteria and chemical pollutants have been investigated in faecal samples of free-ranging whale species and the first record of Blastocystis in fin and sperm whales. Thus, this study may provide baseline data on new anthropozoonotic parasite, bacterial records and heavy metals in free-ranging fin and sperm whales, probably as a result of an increasing anthropogenic activity. This survey calls for more integrated research to perform regular monitoring programs supported by national and/or international authorities responsible for preservation of these still vulnerable and threatened whale species in the Mediterranean Sea.

Streptococcal Infections in Marine Mammals

Marine mammals are sentinels for the marine ecosystem and threatened by numerous factors including infectious diseases. One of the most frequently isolated bacteria are beta-hemolytic streptococci. However, knowledge on ecology and epidemiology of streptococcal species in marine mammals is very limited. This review summarizes published reports on streptococcal species, which have been detected in marine mammals. Furthermore, we discuss streptococcal transmission between and adaptation to their marine mammalian hosts. We conclude that streptococci colonize and/or infect marine mammals very frequently, but in many cases, streptococci isolated from marine mammals have not been further identified. How these bacteria disseminate and adapt to their specific niches can only be speculated due to the lack of respective research. Considering the relevance of pathogenic streptococci for marine mammals as part of the marine ecosystem, it seems that they have been neglected and should receive scientific interest in the future.

Description and genetic characterisation of Pulchrascaris australis n. sp. in the scalloped hammerhead shark, Sphyrna lewini (Griffin & Smith) in Australian waters

Being listed in the IUCN Red List of Threatened Species, knowledge on the biology, health and diseases of the scalloped hammerhead, Sphyrna lewini (Griffith & Smith) is limited; this is especially true for its parasites. In this paper, a new species, Pulchrascaris australis, is morphologically described followed by genetic characterisation based on the sequence of the ITS region. The new species can be easily differentiated from its congeners based on the morphology of the mouthpart, spicules, plectanes, eggs and vulva. Phylogenetic analyses clearly distinguish specimens in the present study from other parasitic nematodes found in the Australasian waters and elsewhere. The sequencing data also suggest that Terranova larval type I found previously in various fish from New Caledonian and Australian (Queensland) waters also belong to Pulchrascaris australis n. sp.

Broad tapeworms (Diphyllobothriidae), parasites of wildlife and humans: Recent progress and future challenges

Tapeworms of the family Diphyllobothriidae, commonly known as broad tapeworms, are predominantly large-bodied parasites of wildlife capable of infecting humans as their natural or accidental host. Diphyllobothriosis caused by adults of the genera Dibothriocephalus, Adenocephalus and Diphyllobothrium is usually not a life-threatening disease. Sparganosis, in contrast, is caused by larvae (plerocercoids) of species of Spirometra and can have serious health consequences, exceptionally leading to host's death in the case of generalised sparganosis caused by 'Sparganum proliferum'. While most of the definitive wildlife hosts of broad tapeworms are recruited from marine and terrestrial mammal taxa (mainly carnivores and cetaceans), only a few diphyllobothriideans mature in fish-eating birds. In this review, we provide an overview the recent progress in our understanding of the diversity, phylogenetic relationships and distribution of broad tapeworms achieved over the last decade and outline the prospects of future research. The multigene family-wide phylogeny of the order published in 2017 allowed to propose an updated classification of the group, including new generic assignment of the most important causative agents of human diphyllobothriosis, i.e., Dibothriocephalus latus and D. nihonkaiensis. Genomic data of selected representatives have also begun to accumulate, promising future developments in understanding the biology of this particular group of parasites. The list of nominal species of taxonomically most complicated genus Spirometra as well as host-parasite list of 37 species of broad tapeworms parasitising marine mammals (pinnipeds and cetaceans) are also provided.

Parasite fauna of wild Antillean manatees (Trichechus manatus manatus) of the Andean Region, Colombia

BACKGROUND

Antillean manatees (Trichechus manatus manatus) are large herbivorous aquatic mammals living in limited areas of South, Central and North America. As with other aquatic mammals, Antillean manatees can be infected by a variety of protozoan and metazoan parasites, some of them with zoonotic potential, which affect not only their welfare but also population health status. Therefore, we conducted the first epidemiological survey in Colombian free-ranging Antillean manatees to estimate their actual gastrointestinal parasite status.

RESULTS

In total, 69 faecal samples were collected from free-ranging individual manatees during ecology field studies in the rivers Carare and San Juan and in two associated wetlands in the Andean region of Colombia. Parasite diversity encompassed six different endoparasite species. The highest prevalence was found for protozoan infections with Eimeria nodulosa (47.8%) and Eimeria manatus-like species (type A, B; 43.4%), followed by Entamoeba sp. (14.49%) and Giardia sp. (1.4%) infections. In addition, infections with the trematode Chiorchis fabaceus were detected at a high prevalence (33.3%). Molecular characterization of sirenian Eimeria species led to the distinction of three species, E. nodulosa and two E. manatus-like species (type A, B). Phylogenetic analyses indicated a host-specific adaptation of sirenian Eimeria species as previously reported for Eimeria species from other mammalian hosts.

CONCLUSIONS

This study provides the first record of Antillean manatee infection with Giardia and Entamoeba species in Colombia, representing two important anthropozoonotic parasite genera. This survey should serve as a baseline investigation for future monitoring on parasitic zoonoses in this mammal and encourage for investigations on their impact on both public health and wild manatee welfare.

Antarctophthirus microchir infestation in synanthropic South American sea lion (Otaria flavescens) males diagnosed by a novel non-invasive method

Antarctophthirus microchir is a sucking louse species belonging to the family Echinophthiriidae and has been reported to parasitize all species of the subfamily Otariinae, the sea lions. Former studies on this ectoparasite mainly required fixation, immobilization, or death of host species and especially examinations of adult male sea lions are still very rare. Between March and May 2018, adult individuals of a unique “urban” bachelor group of South American sea lions (Otaria flavescens) living directly in the city of Valdivia, Chile, were studied regarding their ectoparasite infestation status. For first time, a non-invasive method in the form of a lice comb screwed on a telescopic rod and grounded with adhesive tape was used for sample taking process. Overall, during combing different stages of A. microchir were detected in 4/5 O. flavescens individuals, especially at the junction between the back and hind flippers. Our findings represent the first report of A. microchir infesting individuals of this synanthropic colony and fulfilling complete life cycle in a sea lion group despite inhabiting freshwater and in absence of females/pups. Our “telescopic lice comb apparatus” offers a new strategy to collect different stages of ectoparasites and a range of epidermal material, such as fur coat hair and superficial skin tissue for a broad spectrum of research fields in wildlife sciences in an unmolested and stress reduced manner.

Pinniped- and Cetacean-Derived ETosis Contributes to Combating Emerging Apicomplexan Parasites (Toxoplasma gondii, Neospora caninum) Circulating in Marine Environments

Leukocytes play a major role in combating infections either by phagocytosis, release of antimicrobial granules, or extracellular trap (ET) formation. ET formation is preceded by a certain leukocyte cell death form, known as ETosis, an evolutionarily conserved mechanism of the innate immune system also observed in marine mammals. Besides several biomolecules and microbial stimuli, marine mammal ETosis is also trigged by various terrestrial protozoa and metazoa, considered nowadays as neozoan parasites, which are circulating in oceans worldwide and causing critical emerging marine diseases. Recent studies demonstrated that pinniped- and cetacean-derived polymorphonuclear neutrophils (PMNs) and monocytes are able to form different phenotypes of ET structures composed of nuclear DNA, histones, and cytoplasmic peptides/proteases against terrestrial apicomplexan parasites, e.g., Toxoplasma gondii and Neospora caninum. Detailed molecular analyses and functional studies proved that marine mammal PMNs and monocytes cast ETs in a similar way as terrestrial mammals, entrapping and immobilizing T. gondii and N. caninum tachyzoites. Pinniped- and cetacean leukocytes induce vital and suicidal ETosis, with highly reliant actions of nicotinamide adenine dinucleotide phosphate oxidase (NOX), generation of reactive oxygen species (ROS), and combined mechanisms of myeloperoxidase (MPO), neutrophil elastase (NE), and DNA citrullination via peptidylarginine deiminase IV (PAD4).This scoping review intends to summarize the knowledge on emerging protozoans in the marine environment and secondly to review limited data about ETosis mechanisms in marine mammalian species.