Epidemiology of infections due to zoophilic dermatophyte trichophyton simii, an update

Trichophyton simii is an important zoophilic dermatophyte. It has two different names, one for the asexual form (the anamorph state) that occurs in the vertebrate host, and the other for the sexual form (teleomorph also called “perfect state”) produced by mating between anamorphs. The sexual state of T. simii belongs to the genus Arthroderma in the family Arthrodermataceae of the phylum Ascomycota of the Kingdom fungi. Zoophilic Trichophyton species include Trichophyton equinum, T. bullosum, members of the T. mentagrophytes complex, T. simii, and T. verrucosum. The clinical lesions caused by T. simii in humans and animals are usually inflammatory and erythematous. It can be distinguished from other Trichophyton species by its faster growth on agar media, forming finely granular colonies with white-to-pale yellow color on reverse and distinctive to fusiform 3–7 septate macroconidia converting into chlamydospores in older cultures, and pyriform microconidia, and inability to perforate hair in-vitro, and produce the enzyme urease . Trichophyton simii is known to infect monkeys, chickens, dogs, and humans worldwide, though infections are sporadic and epidemic potential and zoonotic risk for humans is low; this dermatophyte is also known to occur as a geophilic species in several countries. The literature search generated a lot of data on T. simii infections from several countries, namely India, Sri Lanka, Japan, Iraq, Iran, Saudi Arabia, Belgium, France, the USA, and Brazil; many of the reports lacked details of clinical lesions and did not mention about treatment/outcome of infections. The results are analyzed and presented concisely in the tables. There is need for investigating the epidemiology of T. simii infections in countries from where, human T. simii infections have been reported, and occurrence of this dermatophyte in soil by employing conventional mycological methods and a newly developed PCR technique based on ITS genomic sequences of this dermatophyte.

Chrysomyxa rhododendri (European rhododendron rust).

C. rhododendri is a heteroecious rust fungus; an obligate parasite completing stages of its life cycle on different plants. Mating of haploid strains occurs on species of Picea, followed by the production of asexual aeciospores that infect Rhododendron species. Another asexual form producing urediniospores occurs on Rhododendron, followed by the production of teliospores (the sexual stage). All stages are known from Europe. The fungus was reported in 1954 on Rhododendron in the northwestern USA, but the aecial form has not been found in North America. The fungus is a Regulated Pest for the USA; it has been introduced into the UK, New Zealand and Australia. As an invasive species, this rust is damaging on species of Picea and Rhododendron. As latent infections on Rhododendron can be overlooked, accidental introduction of the rust may occur through the importation of these popular ornamental plants (Savile, 1973).

Puccinia gladioli.

P. gladioli is a heteroecious rust fungus, an obligate parasite with alternating life stages on different plants. The asexual form occurs on species of Valerianella, producing aeciospores that then infect Gladiolus species. The production of teliospores, the sexual stage, on Gladiolus, completes the cycle. Both stages are known in Europe, North Africa and southwestern Asia, but only the aecial form has been reported in North America, and only on the west coast. The fungus is a Regulated Pest for the USA (Wise et al., 2004) and is absent from South Africa and Australia, where other Gladiolus species are native or naturalized. Although not a significant problem in its native range, this rust fungus could be damaging as an invasive in other temperate areas. Small amounts of infection may be overlooked; therefore accidental introduction of the rust could occur through importation of infected germplasm by the horticultural industry or flower enthusiasts.

A Long Temporal Study of Parasitism in Asexual-Sexual Populations of Carassius gibelio: Does the Parasite Infection Support Coevolutionary Red Queen Dynamics?

Carassius gibelio is an extraordinary cyprinid species exhibiting both sexual and asexual reproduction. We hypothesized that parasitism selection is one of the potential mechanisms contributing to the coexistence of the two reproductive forms of C. gibelio living in the same habitat. We performed a four-year study to investigate the dynamics of parasite infection in C. gibelio. According to the Red Queen prediction, the asexual form is a target of parasite adaptation due to its low genetic variability. Both sexual and gynogenetic forms of C. gibelio exhibited similar levels of prevalence, with monogeneans being the most frequently observed parasite group. We observed the temporal dynamics of parasite infection in the last year of investigation, when both forms were more strongly parasitized. The sexual form was more parasitized by ectoparasites in the first and last years and less parasitized by nematodes in the last year when compared to the gynogenetic form. We found no trend of high parasite infection in gynogenetic mtDNA haplotypes. We conclude that Red Queen dynamics is not the mechanism driving parasite infection in sexual-gynogenetic C. gibelio over a long time scale. Alternatively, we suggest that the dynamics of parasite infection in this complex may be generated by multiple mechanisms.

An initial genetic characterisation of the grape powdery mildew (Erysiphe necator) in New Zealand associated with recent reports of the sexual stage

The asexual form of the grape powdery mildew Erysiphe necator has been present in New Zealand for over 100 years In 2013 the sexual stage was reported for the first time in vineyards in Hawkes Bay associated with increased disease issues This paper presents an initial genetic analysis of New Zealand populations compared to known populations overseas and tentatively identifies two haplotypes new to New Zealand Initial analysis of matingtype ratios indicates only one of these haplotypes is sexually reproducing A better understanding of the fundamental character of the New Zealand populations of Erysiphe necator is needed before an accurate assessment can be made of the practical impact that the introduction of the sexual stage has had on disease incidence and control

Particular Structure of Plasmopara viticola Populations Evolved Under Greek Island Conditions

Plasmopara viticola populations collected from three islands in the Ionian Sea—an arm of the Mediterranean Sea to the west of Greece—were analyzed with microsatellite molecular markers in order to investigate the pathogen population structure. Downy mildew populations from mainland regions previously studied were found to have high genotypic diversity and limited clonality; however, populations under Mediterranean island conditions mostly showed limited variation and the epidemics basically were driven by the multiple clonal infections of one or a few genotypes. Populations from different islands were differentiated from each other, whereas genetic divergence also was found among subpopulations of the same plot. Polyploid individuals and individuals that overwintered in asexual form were observed in some cases. The findings obtained by this population genetics study improve our understanding of the biology of the pathogen and lead to potential alternative control measures for the disease.

Cytogenetics of Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli)

Cytogenetic and morphological studies were conducted with Colletotrichum lindemuthianum (Glomerella cingulata f. sp. phaseoli), the pathogen responsible for anthracnose of common bean (Phaseolus vulgaris). In this species, there is some evidence of genomic variation but it is unknown whether the process occurs in a manner similar to other fungal genetic models. Six isolates from bean plants were used and sexual reproduction was observed in vitro. Meiosis and ascospore formation were investigated by cytogenetical approaches and light microscopy. To study the nucleus and chromosome numbers, a mixture of carmine and orcein propionic dyes was used. Nucleus divisions as well as ascospore maturation were asynchronous. Meiosis was observed in three isolates. In the asexual form, chromosomal polymorphism in conidia was also observed microscopically and the mitosis process was described.

HyBra1, a Brachyury homologue, acts during head formation in Hydra

A homologue of the T-box gene, Brachyury, has been isolated from hydra. The gene, termed HyBra1, is expressed in the endoderm and is associated with the formation of the hypostome, the apical part of the head in four different developmental situations. In adults, which are continuously undergoing patterning, HyBra1 is continuously expressed in the hypostome. During budding, hydra's asexual form of reproduction, the gene is expressed in a small area that will eventually form the hypostome of the developing bud before any morphological sign of budding is apparent. The gene is also expressed very early during head regeneration and is confined to the region that will form the hypostome. During embryogenesis, HyBra1 is expressed shortly before hatching in the region that will form the apical end of the animal, the hypostome. The absence of expression at the apical end of decapitated animals of reg-16, a head formation-deficient mutant, provides additional evidence for a role of HyBra1 during head formation. Further, treatments that alter the head activation gradient have no effect on HyBra1 expression indicating the role of the gene is confined to head formation. Transplantation experiments indicate that the expression occurs before head determination has occurred, but expression does not irreversibly commit tissue to forming a head. A comparison of the function of the Brachyury homologues suggests an evolutionary conservation of a molecular mechanism that has been co-opted for a number of developmental processes throughout evolution.

A Rare Record of the Salp, Thetys Vagina (Tunicata: Thaliacea) From Western Scottish Waters

There are no species of salps (Order: Salpida) indigenous to British waters. Those species that can be found, the most abundant being Salpa fusiformis Cuvier (Fraser, 1981) are carried to British and Irish waters from the open ocean of the western Atlantic. Because of this salps can be good indicators of oceanic water movements near to Britain (Fraser, 1981). The largest species of the Salpidae is Thetys vagina (Tilesius, 1802) which generally reaches ≥230 mm in total length (TL) in the solitary asexual form and ~250 mm TL in the aggregate sexual form (Metcalf, 1918; Fraser, 1981). However, a solitary form measuring 333 mm TL was caught in a trawl from the Hawaiian islands (Nakamura & Yount, 1958). The distribution of T. vagina is usually limited to warm water throughout the Atlantic, including the Mediterranean, Indian and Pacific Oceans (Berrill, 1950). Up to 1981 there have been only two records of T. vagina in British waters (Fraser, 1981). This short paper describes, to the best of my knowledge a third recording of this salp from British waters.