A Rickettsiella Endosymbiont Is a Potential Source of Essential B-Vitamins for the Poultry Red Mite, Dermanyssus gallinae

Prevalence and Diversity of Haemotropic Mycoplasma Species in Cats and Their Ectoparasites (Fleas and Ticks)

Mycoplasma spp. pathogens frequently cause chronic and acute diseases in cats. The aim of the present study was to investigate the presence and genetic diversity of Mycoplasma spp. in cats and their ectoparasites using PCR and sequence analysis of the 16S rRNA gene. Blood samples were collected from 541 domestic and stray cats in Lithuania. Ectoparasites (153 fleas and 321 ticks) were collected from owned domestic cats that live both outdoors and indoors. Mycoplasma spp. were detected in 7.2% of cat blood samples and 4.4% of Ctenocephalides felis fleas. The sequence analysis revealed the presence of Mycoplasma haemofelis in 1.1% of cats and 'Candidatus Mycoplasma haematominutum' in 4.8% of cats. Ct. felis fleas harboured M. haemofelis. To the best of the authors' knowledge, this is the first report on the prevalence and molecular characterisation of Mycoplasma bacteria in cats in Lithuania and cat fleas in the Baltic States.

Microbiome comparison of Dermanyssus gallinae populations from different farm rearing systems and the presence of common endosymbiotic bacteria at developmental stages

The hematophagous arthropod, Dermanyssus gallinae (Poultry red mite, PRM) can cause remarkable economic losses in the poultry industry across the globe. Although overall composition of endosymbiotic bacteria has been shown in previous studies, how farm habitats influence the microbiome remains unclear. In the present study, we compared the bacterial communities of D. gallinae populations collected from the cage and free-range farms using next-generation sequences targeting the V3-V4 hypervariable region of the 16S rRNA gene. The QIIME2 pipeline was followed in bioinformatic analyses. Proteobacteria represented a great majority of the total bacterial community of D. gallinae from both farming systems. More specifically, Bartonella-like bacteria (40.8%) and Candidatus Cardinium (21.5%) were found to be predominant genera in free-range and cage rearing systems, respectively. However, the microbiome variation based on farming systems was not statistically significant. In addition, the presence of the five common endosymbiotic bacteria (Wolbachia, Cardinium, Rickettsiella, Spiroplasma, and Schineria) was screened in different developmental stages of D. gallinae. Cardinium was detected in all developmental stages of D. gallinae. On the other hand, Wolbachia and Rickettsiella were only found in adults/nymphs, but neither in the eggs nor larvae. To our knowledge, this study provides the first microbiome comparison at genus-level in D. gallinae populations collected from different farm habitats and will contribute to the knowledge of the biology of D. gallinae.

What do we know about the microbiome of I. ricinus?

I. ricinus is an obligate hematophagous parasitic arthropod that is responsible for the transmission of a wide range of zoonotic pathogens including spirochetes of the genus Borrelia, Rickettsia spp., C. burnetii, Anaplasma phagocytophilum and Francisella tularensis, which are part the tick´s microbiome. Most of the studies focus on "pathogens" and only very few elucidate the role of "non-pathogenic" symbiotic microorganisms in I. ricinus. While most of the members of the microbiome are leading an intracellular lifestyle, they are able to complement tick´s nutrition and stress response having a great impact on tick´s survival and transmission of pathogens. The composition of the tick´s microbiome is not consistent and can be tied to the environment, tick species, developmental stage, or specific organ or tissue. Ovarian tissue harbors a stable microbiome consisting mainly but not exclusively of endosymbiotic bacteria, while the microbiome of the digestive system is rather unstable, and together with salivary glands, is mostly comprised of pathogens. The most prevalent endosymbionts found in ticks are Rickettsia spp., Ricketsiella spp., Coxiella-like and Francisella-like endosymbionts, Spiroplasma spp. and Candidatus Midichloria spp. Since microorganisms can modify ticks' behavior, such as mobility, feeding or saliva production, which results in increased survival rates, we aimed to elucidate the potential, tight relationship, and interaction between bacteria of the I. ricinus microbiome. Here we show that endosymbionts including Coxiella-like spp., can provide I. ricinus with different types of vitamin B (B2, B6, B7, B9) essential for eukaryotic organisms. Furthermore, we hypothesize that survival of Wolbachia spp., or the bacterial pathogen A. phagocytophilum can be supported by the tick itself since coinfection with symbiotic Spiroplasma ixodetis provides I. ricinus with complete metabolic pathway of folate biosynthesis necessary for DNA synthesis and cell division. Manipulation of tick´s endosymbiotic microbiome could present a perspective way of I. ricinus control and regulation of spread of emerging bacterial pathogens.

Genetic variations and microbiome of the poultry red mite Dermanyssus gallinae

The poultry red mite Dermanyssus gallinae poses a significant threat to the health of hens and poultry production. A comprehensive understanding of D. gallinae is necessary to develop sustainable and efficacious control methods. Here we examined 144 D. gallinae collected from 18 poultry farms throughout the Japanese Archipelago for their genetic variations based on mitochondrial cytochrome c oxidase subunit I (COI) sequences, and microbiome variations based on amplicon sequencing of the 16S ribosomal RNA gene. According to COI sequencing, the Japanese samples were categorized into three haplogroups, which did not reflect the geographical distribution. Microbiome analyses found that the major bacteria associated with D. gallinae were Bartonella, Cardinium, Wolbachia, and Tsukamurella, with Bartonella being most predominant. Among 144 individual mites, all possessed one of the two major types of Bartonella (Bartonella sp. A), while 140 mites possessed the other type (Bartonella sp. B). The presence of the two strains of Bartonella was also confirmed by a single copy gene, rpoB. The presence of Bartonella in laid eggs suggested transovarial vertical transmission. Given that obligate blood-feeding arthropods generally require a supply of B vitamins from symbiotic bacteria, Bartonella may play an important role in mite survival. Rickettsiella, a major symbiont in European D. gallinae populations, and suggested to be an important symbiont by genomic data, was rarely found in Japanese populations. Cardinium detected from D. gallinae fell into a major clade found widely in arthropods, whereas Wolbachia detected in Japanese D. gallinae appear to be a new lineage, located at the base of Wolbachia phylogeny. Of the mitochondrial phylogeny, infection patterns of Cardinium and Wolbachia were strongly correlated, possibly suggesting one or both of the symbionts induce reproductive manipulations and increase spread in the host populations.