Tattoo skin disease (TSD) is a poxviral dermatopathy diagnosed in cetaceans. We review the literature on TSD aetiology, clinical characteristics, pathology and epidemiology and evaluate immune responses against the virus. In addition, necropsy reports for fifty-five harbour porpoises (Phocoena phocoena), twenty-two Delphinidae and four Kogiidae stranded in northern California in 2018–2021 were checked for diagnostic tattoo lesions. TSD occurs in the Mediterranean, North and Barents Seas, as well as in the Atlantic, eastern Pacific and Indian Oceans in at least 21 cetacean species, with varying prevalence. Two cetacean poxvirus (CePV) clades are recognised: CePV-1 in odontocetes and CePV-2 in mysticetes. CePV-1 isolates were recovered from six Delphinidae and one Phocoenidae in the Americas, Europe and Hong Kong. Strains from Delphinidae are closely related. Among Phocoenidae, poxviruses were sampled only in harbour porpoises around the British Isles. CePV-2 isolates were obtained from southern right whales (Eubalaena australis) and a bowhead whale (Balaena mysticetus). In healthy animals, an immune response develops over time, with young calves protected by maternal immunity. Salinity and sea surface temperature do not seem to influence TSD prevalence in free-ranging cetaceans. High concentrations of immunotoxic halogenated organochlorines may cause a more severe clinical disease. Substitution and loss of genes involved in anti-viral immunity may favour CePV entry, replication and persistence in the epidermis. Off California, Delphinidae were less often (26.3%) affected by TSD than harbour porpoises (43.6%). Male porpoises were significantly more prone (58.1%) to show clinical disease than females (25%). Among males, TSD affected a high proportion of juveniles and subadults. TSD was not detected in the Kogiidae.

The surveillance of marine mammal strandings within the framework of a biomonitoring scheme for the Mauritanian coast led to the discovery in 2013 of a 3.98 m long, juvenile rorqual Balaenoptera sp. in an advanced state of decomposition near Chott Boul (16°32.488′N, 016°27.0317′W). Photographs and skin samples were taken, but the specimen could not be collected. Based on limited morphological evidence, only Balaenoptera edeni and B. omurai were plausible. Sequences of three mtDNA regions, i.e. parts of the cox1 and the cytb genes as well as the D-loop, for a total of 2636 bp (> 16% of the mitogenome) identified the specimen as an Omura's whale, B. omurai, the first record in the Atlantic Ocean and at least 11,400 km away from its closest known range in the SW Indian Ocean (Madagascar). The question of whether the specimen is a vagrant or belongs to an unrecognized Atlantic population is discussed. Advection by currents or transport on a ship's bow bulb following collision are discarded. Circumstances (juvenile status, great distance from Indo-Pacific, necessary inter-oceanic passage through cold temperate waters) may slightly favour the hypothesis that B. omurai, if rare, could be autochthonous in the Atlantic. Beach surveys remain a useful tool to assess trends in cetacean species composition, to detect unusual mortality events and to help assess the impacts of anthropogenic activities. This is particularly applicable to remote areas where the marine mammal fauna is poorly known and where fisheries effort is high, such as the Mauritanian coast.

Cetacean poxviruses (CePVs) cause ‘tattoo’ skin lesions in small and large cetaceans worldwide. Although the disease has been known for decades, genomic data for these poxviruses are very limited, with the exception of CePV-Tursiops aduncus, which was completely sequenced in 2020. Using a newly developed pan-pox real-time PCR system targeting a conserved nucleotide sequence located within the Monkeypox virus D6R gene, we rapidly detected the CePV genome in typical skin lesions collected from two Peruvian common bottlenose dolphins (Tursiops truncatus) by-caught off Peru in 1993. Phylogenetic analyses based on the sequencing of the DNA polymerase and DNA topoisomerase genes showed that the two viruses are very closely related to each other, although the dolphins they infected pertained to different ecotypes. The poxviruses described in this study belong to CePV-1, a heterogeneous clade that infects many species of dolphins (Delphinidae) and porpoises (Phocoenidae). Among this clade, the T. truncatus CePVs from Peru were more related to the viruses infecting Delphinidae than to those detected in Phocoenidae. This is the first time that CePVs were identified in free-ranging odontocetes from the Eastern Pacific, surprisingly in 30-year-old samples. These data further suggest a close and long-standing pathogen–host co-evolution, resulting in different lineages of CePVs.

A small, juvenile rorqual live-stranded on Qeshm Island, Iran, in the northern Strait of Hormuz (Persian Gulf) in September 2007. Cause of stranding remains unknown but the whale (QE22.09.2007) showed no severe traumatic injuries nor was emaciated. Based on at least seven morphological features, considered diagnostic in combination, allowed a positive identification as Omura’s whale Balaenoptera omurai . Features included diminutive body size (397 cm), a large number of ventral grooves (n=82) extending caudad of the umbilicus, a strongly falcate dorsal fin, asymmetric colouration of the head (especially lower jaws) reminiscent of fin whale, including three unilateral dark stripes, faint/incomplete lateral rostral ridges, record low number of short, broad baleen plates (204 in right jaw). The likelihood for the existence of a local B. omurai population in the eastern Persian Gulf or northern Arabian Sea seems higher than the wandering of a very young animal or mother/calf pair from any of the known distant distribution areas in the eastern Indian Ocean or SW Indian Ocean (Madagascar). This is the first record of B. omurai in the NW Indian Ocean.