No abstract

Three hemotropic mycoplasmas have been identified in pet cats: Mycoplasma haemofelis, "Candidatus Mycoplasma haemominutum," and "Candidatus Mycoplasma turicensis." The way in which these agents are transmitted is largely unknown. Thus, this study aimed to investigate fleas, ticks, and rodents as well as saliva and feces from infected cats for the presence of hemotropic mycoplasmas, to gain insight into potential transmission routes for these agents. DNA was extracted from arthropods and from rodent blood or tissue samples from Switzerland and from salivary and fecal swabs from two experimentally infected and six naturally infected cats. All samples were analyzed with real-time PCR, and some positive samples were confirmed by sequencing. Feline hemotropic mycoplasmas were detected in cat fleas and in a few Ixodes sp. and Rhipicephalus sp. ticks collected from animals but not in ticks collected from vegetation or from rodent samples, although the latter were frequently Mycoplasma coccoides PCR positive. When shedding patterns of feline hemotropic mycoplasmas were investigated, "Ca. Mycoplasma turicensis" DNA was detected in saliva and feces at the early but not at the late phase of infection. M. haemofelis and "Ca. Mycoplasma haemominutum" DNA was not amplified from saliva and feces of naturally infected cats, despite high hemotropic mycoplasma blood loads. Our results suggest that besides an ostensibly indirect transmission by fleas, direct transmission through saliva and feces at the early phase of infection could play a role in the epizootiology of feline hemotropic mycoplasmas. Neither the investigated tick nor the rodent population seems to represent a major reservoir for feline hemotropic mycoplasmas in Switzerland.

Chromosome sizes of 71 phytoplasmas belonging to 12 major phylogenetic groups including several of the aster yellows subgroups were estimated from electrophoretic mobilities of full-length chromosomes in pulsed-field gels. Considerable variation in genome size, from 660 to 1,130 kilobases (kb), was observed among aster yellows phytoplasmas. Chromosome size heterogeneity was also observed in the stolbur phytoplasma group (range 860 to 1,350 kb); in this group, isolate STOLF contains the largest chromosome found in a phytoplasma to date. A wide range of chromosome sizes, from 670 to 1,075 kb, was also identified in the X-disease group. The other phytoplasmas examined, which included members of the apple proliferation, Italian alfalfa witches' broom, faba bean phyllody, pigeon pea witches' broom, sugarcane white leaf, Bermuda grass white leaf, ash yellows, clover proliferation, and elm yellows groups, all have chromosomes smaller than 1 megabase, and the size ranges within each of these groups is narrower than in the aster yellows, stolbur, and X-disease groups. The smallest chromosome, approximately 530 kb, was found in two Bermuda grass white leaf phytoplasma isolates. This not only is the smallest mollicute chromosome found to date, but also is the smallest chromosome known for any cell. More than one large DNA band was observed in several phytoplasma preparations. Possible explanations for the occurrence of more than one band may be infection of the host plant by different phytoplasmas, the presence of more than one chromosome in the same organism, or the presence of large extrachromosomal DNA elements.

The recently proposed transfer of four rickettsias from the genera Haemobartonella and Eperythrozoon to the genus Mycoplasma with the Candidatus status is herein revised. This is because the Candidatus designation is for new, incompletely described taxa, in order to give them a provisional status. Thus, 'Candidatus Mycoplasma haemofelis' is revised to Mycoplasma haemofelis comb. nov., nom. nov., 'Candidatus Mycoplasma haemomuris' is revised to Mycoplasma haemomuris comb. nov., nom. nov., 'Candidatus Mycoplasma haemosuis' is revised to Mycoplasma haemosuis comb. nov., nom. nov. and 'Candidatus Mycoplasma wenyonii' is revised to Mycoplasma wenyonii comb. nov.

Eperythrozoon ovis, an erythrocytic agent that causes haemolytic anaemia in sheep and goats, occurs worldwide and is currently thought to be a rickettsia. To determine the relationship between this agent and other haemotrophic bacterial parasites, the 16S rRNA gene of this organism was sequenced. Phylogenetic analysis revealed that this wall-less bacterium is not a rickettsia, but a mycoplasma. This mycoplasma is related closely to several other uncultivated, epierythrocytic mycoplasmas that comprise a recently identified group, the haemotrophic mycoplasmas (haemoplasmas). The haemoplasma group is composed of former Eperythrozoon and Haemobartonella species, as well as newly identified epierythrocytic mycoplasmas. Haemoplasmas parasitize the surface of erythrocytes of a wide variety of vertebrate animal hosts and are transmitted mainly by blood-feeding arthropod vectors. Recognition that E. ovis is a mycoplasma provides a new approach to dealing with this bacterium. It is proposed that E. ovis should be reclassified as Mycoplasma ovis comb. nov.Eperythrozoon ovis is an uncultivated, wall-less bacterium that parasitizes the surface of sheep erythrocytes. This organism is transmitted by blood-feeding arthropods and parasitizes animals in sheep-rearing regions throughout the world. Signs of infection include mild to severe haemolytic anaemia, as well as icterus; animals may exhibit poor weight gain and depression, but death is rare in adults. Infections are frequently unapparent and chronic. E. ovis also infects goats, in which it results in more severe disease (Splitter et al., 1956;Kreier & Ristic, 1963;Daddow, 1979;Mason et al., 1989;Mason & Statham, 1991).As E. ovis has not been cultivated, diagnosis is made by detection of organisms on erythrocytes in Romanowskytype or acridine orange-stained blood smears and by serological methods. Parasitism of erythrocytes often occurs at a low level and is transient; detection requires examination of repeated blood smears. However, erythrocyte parasitaemia can be as high as 100 % in our experience; a high level of parasitaemia can occur even in subclinical infection and can persist for months (Overas, 1969;Brun-Hansen et al., 1997). E. ovis is completely resistant to penicillin and other antimicrobial agents that target the cell wall. Also, tetracycline treatment does not eliminate this agent from chronically infected animals. This organism has been thought to be a rickettsia because of its obligate parasitism, erythrocyte localization, small size, staining properties and transmission by arthropod vectors. E. ovis and a number of similar haemotrophic bacteria have been classified in the order Rickettsiales, family Anaplasmataceae, in the genera Haemobartonella and Eperythrozoon (Kreier & Ristic, 1984;Kreier et al., 1992). Recently, phylogenetic analysis of 16S rRNA gene sequences from four of these bacteria, Haemobartonella felis, Haemobartonella muris, Eperythrozoon suis and Eperythrozoon wenyonii, has demonstrated that these wallless bacteria are not rickettsiae, but tha...