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

Heartworms in Halichoerus grypus: first records of Acanthocheilonema spirocauda (Onchocercidae; Filarioidea) in 2 grey seals from the North Sea

The assumed definitive host of the heartworm Acanthocheilonema spirocauda (Onchocerdidae; Filarioidea) is the harbour seal (Phoca vitulina). This filaroid nematode parasitizing in cardiac ventricles and blood vessel lumina of harbour seals (P. vitulina) has a low prevalence and seldom causes severe health impacts. The seal louse (Echinophthirius horridus) is the assumed intermediate host for transmission of A. spirocauda filariae between seals, comprising a unique parasite assembly conveyed from the terrestrial ancestors of pinnipeds. Although grey seals (Halichoerus grypus) are infected by seal lice, heartworm infection was not verified. Analysing a longterm dataset compiled over decades (1996–2021) of health monitoring seals along the German coasts comprising post mortem investigations and archived parasites, 2 cases of A. spirocauda infected male grey seals were detected. Tentative morphological identification was confirmed with molecular tools by sequencing a section of mtDNA COI and comparing nucleotide data with available heartworm sequence. This is the first record of heartworm individuals collected from the heart of grey seals at necropsy. It remains puzzling why heartworm infection occur much less frequently in grey than in harbour seals, although both species use the same habitat, share mixed haul-outs and consume similar prey species. If transmission occurs directly via seal louse vectors on haul-outs, increasing seal populations in the North- and Baltic Sea could have density dependent effects on prevalence of heartworm and seal louse infections. It remains to be shown how species-specificity of filarial nematodes as well as immune system traits of grey seals influence infection patterns of A. spirocauda.

Viability and Desiccation Resistance of Bartonella henselae in Biological and Non-Biological Fluids: Evidence for Pathogen Environmental Stability

Pathogen environmental stability is an often-neglected research priority for pathogens that are known to be vector-transmitted. Bartonella henselae, the etiologic agent of Cat Scratch Disease, has become a "pathogen of interest" in several serious human illnesses, which include neoplastic, cardiovascular, neurocognitive, and rheumatologic conditions. Survival in the flea gut and feces as well as the association with a biofilm in culture-negative endocarditis provides insight into this organism's ability to adjust to environmental extremes. The detection of B. henselae DNA in blood and tissues from marine mammals also raises questions about environmental stability and modes of pathogen transmission. We investigated the ability of B. henselae to survive in fluid matrices chosen to mimic potential environmental sources of infective materials. Feline whole blood, serum and urine, bovine milk, and physiologic saline inoculated with a laboratory strain of B. henselae San Antonio 2 were subsequently evaluated by culture and qPCR at specified time intervals. Bacterial viability was also assessed following desiccation and reconstitution of each inoculated fluid matrix. Bartonella henselae SA2 was cultured from feline urine up to 24 h after inoculation, and from blood, serum, cow's milk, and physiologic saline for up to 7 days after inoculation. Of potential medical importance, bacteria were cultured following air-desiccation of all fluid inoculates. The viability and stability of Bartonella within biological and non-biological fluids in the environment may represent a previously unrecognized source of infection for animals and human beings.

Preliminary study of shark microbiota at a unique mix-species shark aggregation site, in the Eastern Mediterranean Sea

Sharks, as apex predators, play an essential ecological role in shaping the marine food web and maintaining healthy and balanced marine ecosystems. Sharks are sensitive to environmental changes and anthropogenic pressure and demonstrate a clear and rapid response. This designates them a "keystone" or "sentinel" group that may describe the structure and function of the ecosystem. As a meta-organism, sharks offer selective niches (organs) for microorganisms that can provide benefits for their hosts. However, changes in the microbiota (due to physiological or environmental changes) can turn the symbiosis into a dysbiosis and may affect the physiology, immunity and ecology of the host. Although the importance of sharks within the ecosystem is well known, relatively few studies have focused on the microbiome aspect, especially with long-term sampling. Our study was conducted at a site of coastal development in Israel where a mixed-species shark aggregation (November-May) is observed. The aggregation includes two shark species, the dusky (Carcharhinus obscurus) and sandbar (Carcharhinus plumbeus) which segregate by sex (females and males, respectively). In order to characterize the bacterial profile and examine the physiological and ecological aspects, microbiome samples were collected from different organs (gills, skin, and cloaca) from both shark species over 3 years (sampling seasons: 2019, 2020, and 2021). The bacterial composition was significantly different between the shark individuals and the surrounding seawater and between the shark species. Additionally, differences were apparent between all the organs and the seawater, and between the skin and gills. The most dominant groups for both shark species were Flavobacteriaceae, Moraxellaceae, and Rhodobacteraceae. However, specific microbial biomarkers were also identified for each shark. An unexpected difference in the microbiome profile and diversity between the 2019-2020 and 2021 sampling seasons, revealed an increase in the potential pathogen Streptococcus. The fluctuations in the relative abundance of Streptococcus between the months of the third sampling season were also reflected in the seawater. Our study provides initial information on shark microbiome in the Eastern Mediterranean Sea. In addition, we demonstrated that these methods were also able to describe environmental episodes and the microbiome is a robust measure for long-term ecological research.

Novel 3D in situ visualization of seal heartworm (Acanthocheilonema spirocauda) larvae in the seal louse (Echinophthirius horridus) by X-ray microCT

The seal heartworm Acanthocheilonema spirocauda (Nematoda: Onchocercidae) parasitizes the heart and pulmonary arteries of various phocid seals of the Northern Hemisphere. Over many decades, potential vectors of this parasite have been discussed, and to this date, the life cycle is not fully known. The seal louse Echinophthirius horridus (Anoplura: Echinophthiriidae) is an obligatory, permanent and haematophagous ectoparasite of phocids that has been hypothesized to function as obligate intermediate host for A. spirocauda. We examined 11 adult E. horridus specimens collected from stranded harbour seals (Phoca vitulina) in rehabilitation at the Sealcentre Pieterburen by X-ray microCT imaging, aiming to illustrate larval A. spirocauda infection sites in situ. In three of these specimens, thread-like larvae were detected in insect organs. Detailed imaging of the most infected louse revealed a total of 54 A. spirocauda larvae located either in fat bodies or the haemocoel. Histological analysis of the same specimen illustrated nematode cross-sections, confirming X-ray microCT data. The current data strongly suggest that E. horridus is a natural intermediate host for A. spirocauda. Moreover, we demonstrate the potential of X-ray microCT-based imaging as a non-destructive method to analyze host-parasite interactions, especially in the neglected field of marine mammal parasitology.

The seal louse (Echinophthirius horridus) in the Dutch Wadden Sea: investigation of vector-borne pathogens

BACKGROUND

Belonging to the anopluran family Echinophthiriidae, Echinophthirius horridus, the seal louse, has been reported to parasitise a broad range of representatives of phocid seals. So far, only a few studies have focused on the vector function of echinophthiriid lice, and knowledge about their role in pathogen transmission is still scarce. The current study aims to investigate the possible vector role of E. horridus parasitising seals in the Dutch Wadden Sea.

METHODS

E. horridus seal lice were collected from 54 harbour seals (Phoca vitulina) and one grey seal (Halichoerus grypus) during their rehabilitation period at the Sealcentre Pieterburen, The Netherlands. DNA was extracted from pooled seal lice of individual seals for molecular detection of the seal heartworm Acanthocheilonema spirocauda, the rickettsial intracellular bacterium Anaplasma phagocytophilum, and the cell wall-less bacteria Mycoplasma spp. using PCR assays.

RESULTS

Seal lice from 35% of the harbour seals (19/54) and from the grey seal proved positive for A. spirocauda. The seal heartworm was molecularly characterised and phylogenetically analysed (rDNA, cox1). A nested PCR was developed for the cox1 gene to detect A. spirocauda stages in seal lice. A. phagocytophilum and a Mycoplasma species previously identified from a patient with disseminated 'seal finger' mycoplasmosis were detected for the first time, to our knowledge, in seal lice.

CONCLUSIONS

Our findings support the potential vector role of seal lice in the transmission of A. spirocauda and reveal new insights into the spectrum of pathogens occurring in seal lice. Studies on vector competence of E. horridus, especially for bacterial pathogens, are essentially needed in the future as these pathogens might have detrimental effects on the health of seal populations. Furthermore, studies on the vector role of different echinophthiriid species infecting a wide range of pinniped hosts should be conducted to extend the knowledge of vector-borne pathogens.

Comparative Ecology of Bartonella and Brucella Infections in Wild Carnivores

Phylogenetic sister clades Bartonella and Brucella within the order Rhizobiales present some common biological characteristics as well as evident differences in adaptations to their mammalian reservoirs. We reviewed published data on Bartonella and Brucella infections in wild carnivores to compare the ecology of these bacteria in relatively similar host environments. Arthropod vectors are the main mechanism for Bartonella species transmission between mammalian hosts. The role of arthropods in transmission of Brucella remains disputed, however experimental studies and reported detection of Brucella in arthropods indicate potential vector transmission. More commonly, transmission of Brucella occurs via contact exposure to infected animals or the environment contaminated with their discharges. Of 26 species of carnivores tested for both Bartonella and Brucella, 58% harbored either. Among them were bobcats, African lions, golden jackals, coyotes, wolves, foxes, striped skunks, sea otters, raccoons, and harbor seals. The most common species of Bartonella in wild carnivores was B. henselae, found in 23 species, followed by B. rochalimae in 12, B. clarridgeiae in ten, and B. vinsonii subsp. berkhoffii in seven. Among Brucella species, Br. abortus was reported in over 30 terrestrial carnivore species, followed by Br. canis in seven. Marine carnivores, such as seals and sea lions, can host Br. pinnipedialis. In contrast, there is no evidence of a Bartonella strain specific for marine mammals. Bartonella species are present practically in every sampled species of wild felids, but of 14 Brucella studies of felids, only five reported Brucella and those were limited to detection of antibodies. We found no reports of Bartonella in bears while Brucella was detected in these animals. There is evident host-specificity of Bartonella species in wild carnivores (e.g., B. henselae in felids and B. vinsonii subsp. berkhoffii in canids). A co-adaptation of Brucella with terrestrial wild carnivore hosts is not as straightforward as in domestic animals. Wild carnivores often carry the same pathogens as their domesticated relatives (cats and dogs), but the risk of exposure varies widely because of differences in biology, distribution, and historical interactions.

Genotyping ofBartonellabacteria and their animal hosts: current status and perspectives

Growing evidence demonstrates that bacterial species diversity is substantial, and many of these species are pathogenic in some contexts or hosts. At the same time, laboratories and museums have collected valuable animal tissue and ectoparasite samples that may contain substantial novel information on bacterial prevalence and diversity. However, the identification of bacterial species is challenging, partly due to the difficulty in culturing many microbes and the reliance on molecular data. Although the genomics revolution will surely add to our knowledge of bacterial systematics, these approaches are not accessible to all researchers and rely predominantly on cultured isolates. Thus, there is a need for comprehensive molecular analyses capable of accurately genotyping bacteria from animal tissues or ectoparasites using common methods that will facilitate large-scale comparisons of species diversity and prevalence. To illustrate the challenges of genotyping bacteria, we focus on the genusBartonella, vector-borne bacteria common in mammals. We highlight the value and limitations of commonly used techniques for genotyping bartonellae and make recommendations for researchers interested in studying the diversity of these bacteria in various samples. Our recommendations could be applicable to many bacterial taxa (with some modifications) and could lead to a more complete understanding of bacterial species diversity.

Bartonella spp. exposure in northern and southern sea otters in Alaska and California

Since 2002, an increased number of northern sea otters (Enhydra lutris kenyoni) from southcentral Alaska have been reported to be dying due to endocarditis and/or septicemia with infection by Streptococcus infantarius subsp. coli. Bartonella spp. DNA was also detected in northern sea otters as part of mortality investigations during this unusual mortality event (UME) in Kachemak Bay, Alaska. To evaluate the extent of exposure to Bartonella spp. in sea otters, sera collected from necropsied and live-captured northern sea otters, as well as necropsied southern sea otters (Enhydra lutris nereis) unaffected by the UME, were analyzed using an immunofluorescent antibody assay. Antibodies against Bartonella spp. were detected in sera from 50% of necropsied and 34% of presumed healthy, live-captured northern sea otters and in 16% of necropsied southern sea otters. The majority of sea otters with reactive sera were seropositive for B. washoensis, with antibody titers ranging from 1:64 to 1:256. Bartonella spp. antibodies were especially common in adult northern sea otters, both free-living (49%) and necropsied (62%). Adult stranded northern sea otters that died from infectious causes, such as opportunistic bacterial infections, were 27 times more likely to be Bartonella seropositive than adult stranded northern sea otters that died from noninfectious causes (p<0.001; 95% confidence interval 2.62-269.4). Because Bartonella spp. antibodies were detected in necropsied northern sea otters from southcentral (44%) and southwestern (86%) stocks of Alaska, as well as in necropsied southern sea otters (16%) in southcentral California, we concluded that Bartonella spp. exposure is widely distributed among sea otter populations in the Eastern Pacific, providing context for investigating future disease outbreaks and monitoring of Bartonella infections for sea otter management and conservation.

Prevalence and diversity of Bartonella species in commensal rodents and ectoparasites from Nigeria, West Africa

Background

Bartonellae are fastidious bacteria causing persistent bacteremia in humans and a wide variety of animals. In recent years there is an increasing interest in mammalian bartonelloses in general and in rodent bartonelloses in particular. To date, no studies investigating the presence of Bartonella spp. in rodents and ectoparasites from Nigeria were carried out.

Methodology/Principal Findings

The aim of the current study was to investigate the presence of Bartonella spp. in commensal rodents and their ectoparasites in Nigeria. We report, for the first time, the molecular detection of Bartonella in 26% (46/177) of commensal rodents (Rattus rattus, R. norvegicus and Cricetomys gambianus) and 28% (9/32) of ectoparasite pools (Xenopsylla cheopis, Haemolaelaps spp., Ctenophthalmus spp., Hemimerus talpoides, and Rhipicephalus sanguineus) from Nigeria. Sequence analysis of the citrate synthase gene (gltA) revealed diversity of Bartonella spp. and genotypes in Nigerian rodents and their ectoparasites. Bartonella spp. identical or closely related to Bartonella elizabethae, Bartonella tribocorum and Bartonella grahamii were detected.

Conclusions/Significance

High prevalence of infection with Bartonella spp. was detected in commensal rodents and ectoparasites from Nigeria. The Bartonella spp. identified were previously associated with human diseases highlighting their importance to public health. Further studies need to be conducted to determine whether the identified Bartonella species could be responsible for human cases of febrile illness in Nigeria.

Bartonella species are zoonotic vector-borne bacteria that typically parasitize the erythrocytes of mammalian hosts, resulting in long lasting infections. They are responsible for a wide range of clinical manifestations in both immunocompetent and immunocompromised hosts.

Rodents and a wide range of small mammals serve as reservoirs of bartonellae, usually with no apparent clinical manifestations. Close association between rodents and humans especially in rural communities as well as in the overcrowded cities facilitates transmission of these bacteria.

There have been no studies investigating the presence of Bartonella spp. in rodents and ectoparasites from Nigeria. The aim of the current study was to investigate the presence of Bartonella spp. in commensal rodents and their ectoparasites in Nigeria and its public health implications. We report, for the first time, the molecular detection of Bartonella in 26% (46/177) of commensal rodents and 28% (9/32) of ectoparasite pools from Nigeria. Sequence analysis of the citrate synthase gene (gltA) revealed diversity of Bartonella spp. and genotypes in Nigerian commensal rodents and their ectoparasites. The Bartonella spp. detected in this study were identical or closely related to Bartonella elizabethae, Bartonella tribocorum and Bartonella grahamii previously associated with human diseases highlighting their importance to public health.

Bartonella species and their ectoparasites: selective host adaptation or strain selection between the vector and the mammalian host?

A wide range of blood-sucking arthropods have either been confirmed or are suspected as important vectors in Bartonella transmission to mammals, including humans. Overall, it appears that the diversity of Bartonella species DNA identified in ectoparasites is much broader than the species detected in their mammalian hosts, suggesting a mechanism of adaptation of Bartonella species to their host-vector ecosystem. However, these mechanisms leading to the fitness between the vectors and their hosts still need to be investigated.

Feline bartonellosis

Bartonella infection is common among domestic cats, but the role of Bartonella species as feline pathogens requires further study. Most Bartonella species that infect cats are zoonotic. Cats are the mammalian reservoir and vector for Bartonella henselae, an important zoonotic agent. Cat fleas transmit Bartonella among cats, and cats with fleas are an important source of human B henselae infections. New information about Bartonella as feline pathogens has recently been published, and this article summarizes much of that information. Issues surrounding diagnosis and treatment of feline Bartonella infections are described, and prevention of zoonotic transmission of Bartonella is discussed.

Recombination within and between species of the alpha proteobacterium Bartonella infecting rodents

Bartonella infections from wild mice and voles (Apodemus flavicollis, Mi. oeconomus, Microtus arvalis and Myodes glareolus) were sampled from a forest and old-field habitats of eastern Poland; a complex network of Bartonella isolates, referrable to B. taylorii, B. grahamii, B. birtlesii and B. doshiae, was identified by the sequencing of a gltA fragment, comparable to previous studies of Bartonella diversity in rodents. Nested clade analysis showed that isolates could be assigned to zero- and one-step clades which correlated with host identity and were probably the result of clonal expansion; however, sequencing of other housekeeping genes (rpoB, ribC, ftsZ, groEl) and the 16S RNA gene revealed a more complex situation with clear evidence of numerous recombinant events in which one or both Bartonella parents could be identified. Recombination within gltA was found to have generated two distinct variant clades, one a hybrid between B. taylorii and B. doshiae, the other between B. taylorii and B. grahamii. These recombinant events characterised the differences between the two-step and higher clades within the total nested cladogram, involved all four species of Bartonella identified in this work and appear to have played a dominant role in the evolution of Bartonella diversity. It is clear, therefore, that housekeeping gene phylogenies are not robust indicators of Bartonella diversity, especially when only a single gene (gltA or 16S RNA) is used. Bartonella clades infecting Microtus were most frequently involved in recombination and were most frequently tip clades within the cladogram. The role of Microtus in influencing the frequency of Bartonella recombination remains unknown.