Applying XGBoost and SHAP to Open Source Data to Identify Key Drivers and Predict Likelihood of Wolf Pair Presence.

Wolves have returned to Germany since 2000. Numbers have grown to 209 territorial pairs in 2021. XGBoost machine learning, combined with SHAP analysis is applied to predict German wolf pair presence in 2022 for 10 × 10 km grid cells. Model input consisted of 38 variables from open sources, covering the period 2000 to 2021. The XGBoost model predicted well, with 0.91 as the AUC. SHAP analysis ranked the variables: distance to the closest neighboring wolf pair was the main driver for a grid cell to become occupied by a wolf pair. The clustering tendency of related wolves seems to be an important explanatory factor here. Second was the percentage of wooded area. The next eight variables related to wolf presence in the preceding year, except at fifth, eighth and tenth position in the total order: human density (square root) in the grid, percentage arable land and road density respectively. Other variables including the occurrence of wild prey were the weakest predictors. The SHAP analysis also provided crucial added value in identifying a variable that had threshold values where its contribution to the prediction changed from positive to negative or vice versa. For instance, low density of people increased the probability of wolf pair presence, whereas a high density decreased this probability. Cumulative lift techniques showed that the model performed almost four times better than random prediction. The combination of XGBoost, SHAP and cumulative lift techniques is new in wolf management and conservation, allowing for the focusing of educational and financial resources.

Novel B19-like parvovirus in the brain of a harbor seal.

Using random PCR in combination with next-generation sequencing, a novel parvovirus was detected in the brain of a young harbor seal (Phoca vitulina) with chronic non-suppurative meningo-encephalitis that was rehabilitated at the Seal Rehabilitation and Research Centre (SRRC) in the Netherlands. In addition, two novel viruses belonging to the family Anelloviridae were detected in the lungs of this animal. Phylogenetic analysis of the coding sequence of the novel parvovirus, tentatively called Seal parvovirus, indicated that this virus belonged to the genus Erythrovirus, to which human parvovirus B19 also belongs. Although no other seals with similar signs were rehabilitated in SRRC in recent years, a prevalence study of tissues of seals from the same area collected in the period 2008-2012 indicated that the Seal parvovirus has circulated in the harbor seal population at least since 2008. The presence of the Seal parvovirus in the brain was confirmed by real-time PCR and in vitro replication. Using in situ hybridization, we showed for the first time that a parvovirus of the genus Erythrovirus was present in the Virchow-Robin space and in cerebral parenchyma adjacent to the meninges. These findings showed that a parvovirus of the genus Erythrovirus can be involved in central nervous system infection and inflammation, as has also been suspected but not proven for human parvovirus B19 infection.

Prevalence of phocine distemper virus specific antibodies: bracing for the next seal epizootic in north-western Europe.

In 1988 and 2002, two major phocine distemper virus (PDV) outbreaks occurred in harbour seals (Phoca vitulina) in north-western European coastal waters, causing the death of tens of thousands seals. Here we investigated whether PDV is still circulating among seals of the Dutch coastal waters and whether seals have protective serum-antibodies against PDV. Therefore seal serum samples, collected from 2002 to 2012, were tested for the presence of PDV-neutralizing antibodies. Antibodies were detected in most seals in 2002 and 2003 while after 2003 antibodies were detected only in seals less than two month-old and adult seals that probably had survived the 2002 PDV-epizootic. We estimated the current proportion of seals with antibodies against PDV at 11%. These findings suggest that at present the vast majority of seals are not immune to PDV infection. PDV re-introduction in this area may cause a major epizootic with infection of >80% and mass-mortality of >50% of the population.

A dermal melanoma in a young common seal (Phoca vitulina).

A subcutaneous melanocytic tumor was diagnosed during the rehabilitation period of a stranded 7-mo-old common seal (Phoca vitulina) suffering from parasitic bronchopneumonia. The clinical signs of the seal as well as the histopathology of the tumor are described. This is the first time a melanocytic tumor has been diagnosed in a common seal. The mass was identified as a low-grade dermal melanoma.

Identification of a Bartonella species in the harbor seal (Phoca vitulina) and in seal lice (Echinophtirius horridus).

To explore whether harbor seals (Phoca vitulina) are exposed to Bartonella spp., 35 seal lice (Echinophtirius horridus) were collected from seven seals, during their rehabilitation period in the Seal Rehabilitation and Research Center at Pieterburen, The Netherlands. Forty-eight spleen samples were collected during necropsies of other harbor seals that died during rehabilitation, or had stranded dead and were brought to the Seal Rehabilitation and Research Center for postmortem investigation. Lice were grouped into six pools, and DNA was extracted from each pool and from all the seals' spleen samples. One of the six lice pools and one spleen sample were found positive by high-resolution melt, real-time PCR amplifying partial loci of the rpoB gene, and the intergenic spacer (ITS) region. The Bartonella spp. identified in the spleen and lice were found to be identical to each other. One hundred percent sequence similarity with Bartonella henselae was found in the ITS, and 97% sequence similarity with Bartonella grahamii was detected in the rpoB gene. To the best of the authors' knowledge, this is the first report describing the detection of Bartonella spp. from a seal or any other pinniped, and from seal lice, E. horridus. The 100% sequence similarity in the ITS of the Bartonella sp. identified with the zoonotic B. henselae warrants further investigation and characterization of this organism, which may be found to be of public health importance.