In brain tissue of three harbor seals of the German North Sea coast, high virus loads of highly pathogenic avian influenza virus (HPAIV) H5N8 were detected. Identification of different virus variants indicates high exposure to HPAIV circulating in wild birds, but there is no evidence for H5 specific antibodies in healthy seals. Replication of avian viruses in seals may allow HPAIV to acquire mutations needed to adapt to mammalian hosts as shown by PB2 627K variants detected in these cases.

Harbour porpoises are under pressure from increasing human activities. This includes the detonation of ammunition that was dumped in large amounts into the sea during and after World War II. In this context, forty-two British ground mines from World War II were cleared by means of blasting in the period from 28 to 31 August 2019 by a NATO unit in the German Exclusive Economic Zone within the marine protected area of Fehmarn Belt in the Baltic Sea, Germany. Between September and November 2019, 24 harbour porpoises were found dead in the period after those clearing events along the coastline of the federal state of Schleswig-Holstein and were investigated for direct and indirect effects of blast injury. Health evaluations were conducted including examinations of the brain, the air-filled (lungs and gastrointestinal tract) and acoustic organs (melon, acoustic fat in the lower jaw, ears and their surrounding tissues). The bone structure of the tympano-periotic complexes was examined using high-resolution peripheral quantitative computed tomography (HR-pQCT). In 8/24 harbour porpoises, microfractures of the malleus, dislocation of middle ear bones, bleeding, and haemorrhages in the melon, lower jaw and peribullar acoustic fat were detected, suggesting blast injury. In addition, one bycaught animal and another porpoise with signs of blunt force trauma also showed evidence of blast injury. The cause of death of the other 14 animals varied and remained unclear in two individuals. Due to the vulnerability and the conservation status of harbour porpoise populations in the Baltic Sea, noise mitigation measures must be improved to prevent any risk of injury. The data presented here highlight the importance of systematic investigations into the acute and chronic effects of blast and acoustic trauma in harbour porpoises, improving the understanding of underwater noise effects and herewith develop effective measures to protect the population level.

In times of massive biodiversity loss and ongoing environmental crises, it is extremely important to ensure long-term conservation efforts of threatened species like Eurasian otters (Lutra lutra). To gain insights into the status of Northern Germany’s otter population, 92 otters found dead in Schleswig-Holstein between 2015−2020 were collected and underwent detailed dissection with the aim to establish a monitoring program for this population. Examinations followed a protocol especially designed for otters, including various biological data assessments and extended sampling. The finding sites showed a clear concentration in the Continental region. Seasonal concentration differed among the years, yet peaks were seen from fall to winter. Overall, more males than females were found, although this differed among the years. The majority of otters that could be aged were between 1–3 years. Placental scars and pregnancy were recorded in only few females. Nutritional status was good in most cases. Infectious diseases found included Vagococcus lutrae, Toxoplasma gondii, and Emmonsia spp. A major cause of death was roadkill. Known sample bias in studies focusing on roadkill was considered in the finding interpretation. Continuation of the population health investigations is mandatory to analyze potential trends and to establish an actual monitoring program for Eurasian otters in Schleswig-Holstein.

Arthropod ectoparasites of aquatic wildlife often have complex relationships with their host species that have developed over long evolutionary time scales. Specialist parasite occurrence might depend on these hosts’ distributions. Eurasian otter (Lutra lutra) populations are recovering in Northern German federal states, such as Schleswig-Holstein and Lower Saxony. Chewing lice (Lutridia exilis; Ischnocera; Mallophaga) are considered otter-specific yet rare parasites in their known range. In 2022, they were recorded for the first time on nine otters found dead in Northern Germany. All otters originated from the years 2021–2022 and were dissected during population health monitoring programs in 2022. Females (n = 6) were 0–5.5 years old and showed signs of disease in five cases. Males (n = 3), in contrast, were 0–1.6 years old and showed disease in a single case. Individual lice intensity of infection ranged from 1 to 75 specimens per otter. No direct adverse health effects of chewing lice on the otters were noted. Lutridia exilis morphological characteristics were documented and measurements were taken to study specialized adaptations that allow lice to attach to semi-aquatic otters. In addition, morphology was compared between lice from different geographical regions and specimens from previous reports. A region of the COI mDNA was amplified to molecularly characterize L. exilis for the first time and detect genetic differences between otter lice populations in Germany. It is believed that specialist parasites reduce in numbers even before their host populations decline. Recovering otter populations in Northern Germany could be an example of a reverse effect, where the comeback of a host species results in the return of a specialist parasite, which reflects an ultimate boost in overall species biodiversity.

Emerging contaminants are produced globally at high rates and often ultimately find their way into the aquatic environment. These include substances contained in anti-seizure medication (ASM), which are currently appearing in surface waters at increasing concentrations in Germany. Unintentional and sublethal, chronic exposure to pharmaceuticals such as ASMs has unknown consequences for aquatic wildlife. Adverse effects of ASMs on the brain development are documented in mammals. Top predators such as Eurasian otters (Lutra lutra) are susceptible to the bioaccumulation of environmental pollutants. Still little is known about the health status of the otter population in Germany, while the detection of various pollutants in otter tissue samples has highlighted their role as an indicator species. To investigate potential contamination with pharmaceuticals, Eurasian otter brain samples were screened for selected ASMs via high-performance liquid chromatography and mass spectrometry. Via histology, brain sections were analyzed for the presence of potential associated neuropathological changes. In addition to 20 wild otters that were found dead, a control group of 5 deceased otters in human care was studied. Even though none of the targeted ASMs were detected in the otters, unidentified substances in many otter brains were measured. No obvious pathology was observed histologically, although the sample quality limited the investigations.

Amphibian populations are undergoing dramatic global declines, with infectious diseases recognized as major contributors. While chytridiomycosis, caused by Batrachochytrium dendrobatidis (Bd), and disease caused by ranaviruses are well known, herpesviruses in amphibians remain comparatively neglected. We conducted a passive survey using carcasses collected between 2022 and 2025 in Schleswig-Holstein, northern Germany. Dead amphibians (n = 187) were dissected. Skin, kidney, liver, and brain samples were screened for Bd, ranaviruses, bufonid herpesvirus 1 (BfHV1), and ranid herpesvirus 3 (RaHV3) by PCR. BfHV1 was detected in nearly half of the Bufo bufo (common toads; 48.6%), while RaHV3 was identified in 23.6% of the Rana temporaria (common frogs) examined. Bd was detected in a single B. bufo, while ranaviruses were not detected. BfHV1 was present in skin, liver, kidney, and brain samples, whereas RaHV3 was detected exclusively in skin samples. No macroscopical or histological lesions characteristic of herpesviruses or Bd were found. However, the carcass-based approach frequently limited detailed examination due to compromised sample quality. Our findings confirm the presence of amphibian herpesviruses (BfHV1 and RaHV3) in the region without associated lesions, raising questions about their potential to cause systemic infections. Furthermore, our results highlight the limitations of carcass-based surveillance and underscore the need for complementary diagnostic approaches, such as immunohistochemistry and meta-omics.