Understanding the Pathogenesis of Red Mark Syndrome in Rainbow Trout (Oncorhynchus mykiss) through an Integrated Morphological and Molecular Approach

Red mark syndrome (RMS) is a widespread skin disorder of rainbow trout in freshwater aquaculture, believed to be caused by a Midichloria-like organism (MLO). Here, we aimed to study the pathologic mechanisms at the origin of RMS by analyzing field samples from a recent outbreak through gene expression, MLO PCR, quantitative PCR, and a histopathological scoring system proposed for RMS lesions. Statistical analyses included a One-Way Analysis of Variance (ANOVA) with a Dunnett's multiple comparisons test to assess differences among gene expression groups and a nonparametric Spearman correlation between various categories of skin lesions and PCR results. In short, the results confirmed the presence of a high quantity of 16S gene copy numbers of Midichloria-like organisms in diseased skin tissues. However, the number of Midichloria-like organisms detected was not correlated to the degree of severity of skin disease. Midichloria-like organism DNA was found in the spleen and head kidney. The spleen showed pathologic changes mainly of hyperplastic type, reflecting its direct involvement during infection. The most severe skin lesions were characterized by a high level of inflammatory cytokines sustaining and modulating the severe inflammatory process. IL-1 β, IL-6, IL-10, MHC-II, and TCR were upregulated in severe skin lesions, while IL-10 was highly expressed in moderate to severe ones. In the moderate form, the response was driven to produce immunoglobulins, which appeared crucial in controlling the skin disease's severity. Altogether our results illustrated a complex immune interaction between the host and Midichloria-like organism.

Detection of a Novel Chlamydia Species in Invasive Turtles

Simple Summary

The pond slider (Trachemys scripta) is a turtle species native to Central America. Pond sliders have been commercialized as pets since the 1950s, but often ended up being released or escaping into an environment to which they are allochthonous. Trachemys scripta is presently classified as an invasive alien species in Europe and other countries. The introduction of pond sliders in foreign ecosystems has had a deep environmental and ecological impact. Moreover, freed or escaped captive turtles could be carriers of pathogens, such as Chlamydiaceae. In this study, we report the identification of a Chlamydia spp. in two pond sliders found dead after the hibernation period. Further molecular characterization revealed that this Chlamydia is identical to a strain reported in Poland in 2017, found in both captive and free-living freshwater turtles, and has a close phylogenetic relationship to Chlamydia pneumoniae, a species infectious to humans, and to chlamydial strains found in other reptiles. This first finding evidences the presence of this novel Chlamydia in Italian turtles, but further studies will be necessary to evaluate the prevalence in the local turtles’ population and the strain pathogenicity.

Abstract

Trachemys scripta is a turtle species native to Central America. Since the 1950s, pond sliders have been imported worldwide as companion animals, but have often ended up in foreign ecosystems with great ecological consequences. Moreover, both autochthonous and invasive species of turtles can be carriers of pathogens, including Chlamydiaceae. In the present study, pulmonary tissues collected from four Trachemys scripta were tested with a 23S-targeting real-time PCR (rPCR) specific for the Chlamydiaceae family. The turtles were hosted in a rescue center for wild exotic animals located in northeastern Italy, and were found dead after the hibernation period. Two out of four individuals resulted positive in rPCR for the presence of Chlamydiaceae. Further characterization of this positivity was performed by phylogenetic analysis of the 16S rRNA and outer membrane protein A genes. The phylogenetic tree showed that these chlamydial strains are identical to a novel Chlamydia reported in 2017 in Polish freshwater turtles, and closely related to Chlamydia pneumoniae and to other chlamydial strains found in reptiles. This first finding evidences the presence of this Chlamydia strain in Italian turtles, but further studies will be necessary to confirm the presence and the strain pathogenicity and to evaluate its prevalence in the local turtles’ population.

First detection of Cytauxzoon spp. infection in European wildcats (Felis silvestris silvestris) of Italy

Cytauxzoonosis is an emerging, tick-transmitted, protozoan disease affecting domestic and wild felids and caused by Cytauxzoon felis, Cytauxzoon manul and Cytauxzoon spp. This study aimed to determine the presence of infection with Cytauxzoon spp. in Felis silvestris silvestris in Italy, in order to enhance the comprehension of its pattern distribution among domestic cat populations. In addition, wildcats were tested for other endemic vector-borne pathogens in Italy. The carcasses of 21 F. s. silvestris were collected from central and northern regions of Italy. All the animals were submitted to necropsy and samples of the spleens were collected. Cytauxzoon infection was surveyed by a conventional PCR amplifying a portion of the SSU-rDNA of species of Piroplasmida. The samples were also screened for Anaplasma spp., Ehrlichia spp., Rickettsia spp., Babesia spp., Theileria spp., and Leishmania spp. using SYBR Green Real-Time PCR (rPCR) assays. Four animals (19%) were positive for Piroplasmida-PCR assay and three sequenced amplicons were obtained (14.3%), clustering with the Italian, Spanish, French and Romanian Cytauxzoon spp. isolates and with C. manul found in Mongolia. The samples were negative for the other pathogens screened. The present results showed that Cytauxzoon spp. may infect both F. s. silvestris and F. s. catus.

Squamous cell carcinoma with presence of poxvirus-like inclusions in the foot of a pink-backed pelican (Pelecanus rufescens)

Squamous cell carcinoma (SCC) or avian keratoacanthoma is a neoplastic skin lesion of unknown aetiology that has been well described in birds. Some studies have reported that poxviruses may contribute to the onset of SCC. Here we describe a case of SCC on the underside of a pelican's foot. Histologically, the tumour consisted of irregular cords of pleomorphic epithelial cells that invaded the adjacent tissues. Additionally, keratinized epithelial cells and moderate numbers of keratin pearls were observed. Intracytoplasmic inclusions, a characteristic of this virus, were observed in some of these cells, and viral particles were characterized by electron microscopy. Although the aetiology of the carcinoma in this case may have been secondary to chronic focal trauma, the possibility of a latent or chronic form of fowlpox should be considered in the pathogenesis of the lesion.