A novel bacterial symbiont in the nematode Spirocerca lupi

ABSTRACT: BACKGROUND: The parasitic nematode Spirocerca lupi (Spirurida: Thelaziidae), the canine esophagealworm, is the causative agent of spirocercosis, a disease causing morbidity and mortality indogs. Spirocerca lupi has a complex life cycle, involving an obligatory coleopteranintermediate host (vector), an optional paratenic host, and a definitive canid host. Thediagnosis of spirocercosis is challenging, especially in the early disease stages, when adultworms and clinical signs are absent. Thus, alternative approaches are needed to promote earlydiagnosis. The interaction between nematodes and their bacterial symbionts has recentlybecome a focus of novel treatment regimens for other helminthic diseases. RESULTS: Using 16S rDNA-based molecular methods, here we found a novel bacterial symbiont in S.lupi that is closely related to Comamonas species (Brukholderiales: Comamonadaceae) of thebeta-proteobacteria. Its DNA was detected in eggs, larvae and adult stages of S. lupi. Usingfluorescent in situ hybridization technique, we localized Comamonas sp. to the gut epithelialcells of the nematode larvae. Specific PCR enabled the detection of this symbiont's DNA inblood obtained from dogs diagnosed with spirocercosis. CONCLUSIONS: The discovery of a new Comamonas sp. in S. lupi increase the complexity of the interactionsamong the organisms involved in this system, and may open innovative approaches fordiagnosis and control of spirocercosis in dogs.     

A comparison of the prevalence of Spirocerca lupi in three groups of dogs with different life and hunting styles

The prevalence of Spirocerca lupi in 260 privately owned dogs with different life and hunting styles in Greece was based on the examination of randomly taken faecal samples using Teleman's sedimentation technique. The dogs did not demonstrate any clinical signs of spirocerciasis. Although the prevalence was 10%, it was found to be significantly higher in trace hunting dogs (21%), than in scent hunting dogs (5%) and household pets (0%). There was no relationship between prevalence and age/sex of dogs. The impact of life and hunting styles on the prevalence of S. lupi in the dog and that of the faecal examination technique, are discussed.     

Morphological and molecular characterization of Spirocerca lupi (Nematoda: Spirocercidae) from domestic dogs in Vietnam with reference to Spirocerca vulpis

Spirocerca lupi is a common parasitic nematode associated with esophageal cancer of canids. Recent surveys have revealed an increasing number of canids infected with Spirocerca spp. in Africa, the Americas, Europe and Western Asia, and described a new species, Spirocerca vulpis, from red foxes (Vulpes vulpes). However, in Southeast Asia, research on Spirocerca spp. is scarce. Therefore, the aim of this study is to explore Spirocerca infection in domestic dogs in Vietnam and to identify the Spirocerca species by analyzing their morphometric and molecular data. We found Spirocerca spp. specimens in 51 (17.7%) out of 287 dogs examined with the intensity of infection ranging from one to 29 nematodes per dog. These nematodes were morphologically and molecularly identified as S. lupi. For morphology, the presence/absence of teeth, the ratio of glandular to muscular esophagus lengths, and the position of the vulva opening of S. lupi and S. vulpis varied between reports, suggesting caution in identification of Spirocerca species based exclusively on morphological characteristics. The molecular analysis based on a partial cox1 sequence revealed that S. lupi from Vietnam is genetically close to those from India and China, but far different from those of Israel, South Africa, Peru and Hungary. Given high genetic and morphological variations, more extensive surveys on Spirocerca spp. from various mammalian hosts at a greater scale are necessary to elucidate the divergence of this nematode.     

Multinuclear stages of the life cycle ofAcetabularia mediterranea

Summary The reproductive stages of the life cycle ofAcetabularia mediterranea have been studied in Feulgen-stained material. Light-microscopical photographs of secondary nuclei, cyst formation, gamete formation, gamete release, zygote formation and early development of the germlings are presented. The time course of cytological events during gamete formation is described. Mitoses are found between 16 and 24 hours after the induction of cyst germination.The author is indebted to Mrs. S.Artelt who helped with the prepration of the specimens and the photographs.     

Comparative myoanatomy of cycliophoran life cycle stages

The metazoan phylum Cycliophora includes small cryptic epibionts that live attached to the mouthparts of clawed lobsters. The life cycle is complex, with alternating sexual and asexual generations, and involves several sessile and free‐living stages. So far, the morphological and genetic characterization of cycliophorans has been unable to clarify the phylogenetic position of the phylum. In this study, we add new details on the muscular anatomy of the feeding stage, the attached Prometheus larva, the dwarf male, and the female of one of the two hitherto described species, Symbion pandora. The musculature of the feeding stage is composed of myofibers that run longitudinally in the buccal funnel (two fibers) and in the trunk (variable number of fibers). The mouth opening is lined by a myoepithelial ring musculature. A complex myoepithelial sphincter is situated proximal to the anus. In the attached Prometheus larva, three longitudinal sets of myofilaments run dorsally, laterally, and ventrally along the entire anterior‐posterior body axis. The muscular architecture of the dwarf male is complex, especially close to the penis, in the posterior part of the body. An X‐shaped muscle structure is found on the dorsal side, whereas on the ventral side, longitudinal muscles and a V‐shaped muscle structure are present. These muscles are complemented by additional dorsoventral muscles. The mesodermal muscle fibers attach to the cuticle via the epidermis in all life cycle stages studied herein. The musculature of the female is similar to that of the Pandora larva of Symbion americanus and includes dorsoventral muscles and longitudinal muscles that run in the dorsal and ventral body region. Overall, our results reveal striking similarities in the muscular arrangement of the life cycle stages of both Symbion species. J. Morphol., 2010. © 2009 Wiley‐Liss, Inc.     

Role of dung beetle feeding mechanisms in limiting the suitability of species as hosts for the nematode Spirocerca lupi

Various species of dung beetle serve as intermediate hosts after ingesting the embryonated eggs (11–15 × 30–37 µm) of Spirocerca lupi (Spirurida: Spirocercidae) in dog faeces. The feeding mechanisms of coprophagous dung beetles restrict the size of the food particles they can ingest and hence may determine which species can be efficient vectors for S. lupi. In this study, we aimed to exclude certain dung beetle species as possible hosts of S. lupi based on whether or not they ingested latex beads of known diameters mixed into fresh cattle dung. We found that the majority (11/14) of species tested can potentially serve as intermediate hosts of S. lupi because their mouthparts allow the passage of food particles larger than the minimum size range of the eggs of this parasite.     

Genome ploidy in different stages of the Giardia lamblia life cycle

The early diverging eukaryotic parasite Giardia lamblia is unusual in that it contains two apparently identical nuclei in the vegetative trophozoite stage. We have determined the nuclear and cellular genome ploidy of G. lamblia cells during all stages of the life cycle. During vegetative growth, the nuclei cycle between a diploid (2N) and tetraploid (4N) genome content and the cell, consequently, cycles between 4N and 8N. Stationary phase trophozoites arrest in the G₂ phase with a ploidy of 8N (two nuclei, each with a 4N ploidy). On its way to cyst formation, a G₁ trophozoite goes through two successive rounds of chromosome replication without an intervening cell division event. Fully differentiated cysts contain four nuclei, each with a ploidy of 4N, resulting in a cyst ploidy of 16N. The newly excysted cell, for which we suggest the term 'excyzoite', contains four nuclei (cellular ploidy 16N). In a reversal of the events occurring during encystation, the excyzoite divides twice to form four trophozoites containing two diploid nuclei each. The formation of multiple cells from a single cyst is likely to be one of the main reasons for the low infectious doses of G. lamblia .