Background: HenneguyaThélohan, 1892 (Myxobolidae) is one of the most species-rich genera of myxosporean parasites infecting fish. Although common in nature, there are few reports of these parasites causing important disease in aquaculture. In this paper, we describe a new species ofHenneguyainfectingPagrus major(Temminck & Schlegel), a fish host introduced to the Mediterranean Sea from Japan in the late 1980s.Results: Large plasmodia of the parasite were found in the bulbus arteriosus and in the ventricle of the infected fish. Spores were found mainly in the kidney and heart and were accompanied by melanized macrophages or vascular intimal proliferation mixed with a mild non-suppurative response, respectively. Comparisons of morphometric data for spore and polar capsule length and width, suggest a unique combination of features in the newly described species. Molecular analysis, based on18SrDNA sequence of the parasite, followed by phylogenetic analysis, indicated that the parasite described here is a novel species ofHenneguya, clustered with the marine congeneric species.Conclusions: Henneguya aegean. sp. infects in aquacultureP. major, a host introduced as eggs to the Mediterranean from Japan. Despite the high host specificity of the myxobolid parasites,H. aegean. sp. seems to be able to useP. majoras a host and propagate successfully, causing morbidity and mortality. This could result in spillback of the new species from high density cultured non-nativeP. majorto native fish hosts.

This case report describes the clinical, ultrasonographic and postmortem findings in an alpaca with Mycobacterium kansasii infection. The alpaca was referred because of chronic weight loss and weakness. The results of clinical examination, haematology and serum biochemistry were not diagnostic. Ultrasonography of the liver revealed multiple, hyperechogenic lesions with a diameter of 1 to 3 cm. Histological evaluation of a liver biopsy sample showed acute, multifocal, suppurative, necrotising hepatitis. Despite treatment with antibiotics, the alpaca died. Postmortem examination revealed nodular to coalescing lesions in the liver, lungs, mediastinum, pleura and greater omentum, which could not be differentiated macroscopically or histologically from lesions caused by tuberculosis. Ziehl-Neelsen staining showed massive numbers of rods within epithelioid macrophages, which were identified as Mycobacterium kansasii by polymerase chain reaction analysis.

Epitheliocystis is a fish gill disease caused by a broad range of intracellular bacteria infecting freshwater and marine fish worldwide. Here we report the occurrence and progression of epitheliocystis in greater amberjack reared in Crete (Greece). The disease appears to be caused mainly by a novel Betaproteobacteria belonging to the Candidatus Ichthyocystis genus with a second agent genetically similar to Ca. Parilichlamydia carangidicola coinfecting the gills in some cases. After a first detection of the disease in 2017, we investigated epitheliocystis in the following year’s cohort of greater amberjack juveniles (cohort 2018) transferred from inland tanks to the same cage farm in the open sea where the first outbreak was detected. This cohort was monitored for over a year together with stocks of gilthead seabream and meagre co-farmed in the same area. Our observations showed that epitheliocystis could be detected in greater amberjack gills as early as a month following the transfer to sea cages, with ionocytes at the base of the gill lamellae being initially infected. Cyst formation appears to trigger a proliferative response, leading to the fusion of lamellae, impairment of gill functions and subsequently to mortality. Lesions are characterized by infiltration of immune cells, indicating activation of the innate immune response. At later stages of the outbreak, cysts were no longer found in ionocytes but were observed in mucocytes at the trailing edge of the filament. Whole cysts appeared finally to be expelled from infected mucocytes directly into the water, which might constitute a novel means of dispersion of the infectious agents. Molecular screening indicates that meagre is not affected by this disease and confirms the presence of previously described epitheliocystis agents, Ca. Ichthyocystis sparus, Ca. Ichthyocystis hellenicum and Ca. Similichlamydia spp., in gilthead seabream. Prevalence data show that the bacteria persist in both gilthead seabream and greater amberjack cohorts after first infection.

Restriction of nutrients to pathogens (nutritional immunity) is a critical innate immune response mechanism that operates when pathogens such as Mycobacterium tuberculosis have the potential to evade humoral immunity. Tuberculosis is of growing concern for zoological collections worldwide and is well-illustrated by infections of Asian and African elephants, where tuberculosis is difficult to diagnose. Here, we investigated hematological parameters and iron deposition in liver, lung, and spleen of three Asian elephants (Elephas maximus) infected with Mycobacterium tuberculosis. For reference purposes, we analyzed tissue samples from control M. tuberculosis-negative elephants with and without evidence of inflammation and/or chronic disease. Molecular analyses of bacterial lesions of post mortally collected tissues confirmed M. tuberculosis infection in three elephants. DNA sequencing of the bacterial cultures demonstrated a single source of infection, most likely of human origin. In these elephants, we observed moderate microcytic anemia as well as liver (mild), lung (moderate) and spleen (severe) iron accumulation, the latter mainly occurring in macrophages. Macrophage iron sequestration in response to infection and inflammation is caused by inhibition of iron export via hepcidin-dependent and independent mechanisms. The hepatic mRNA levels of the iron-regulating hormone hepcidin were increased in only one control elephant suffering from chronic inflammation without mycobacterial infection. By contrast, all three tuberculosis-infected elephants showed low hepcidin mRNA levels in the liver and low serum hepcidin concentrations. In addition, hepatic ferroportin mRNA expression was high. This suggests that the hepcidin/ferroportin regulatory system aims to counteract iron restriction in splenic macrophages in M. tuberculosis infected elephants to provide iron for erythropoiesis and to limit iron availability for a pathogen that predominantly proliferates in macrophages. Tuberculosis infections appear to have lingered for more than 30 years in the three infected elephants, and decreased iron availability for mycobacterial proliferation may have forced the bacteria into a persistent, non-proliferative state. As a result, therapeutic iron substitution may not have been beneficial in these elephants, as this therapy may have enhanced progression of the infection.

The Chlamydiaceae is a family of strict, intracellular bacteria which include human and animal pathogens such as Chlamydia trachomatis and Chlamydia psittaci. Following the death of multiple Ancistrus dolichopterus fish (bushymouth catfish) in a tropical aquarium, the specimens were examined for a potential infectious agent. To do so, McCoy cells (ATCC CRL-1696) were inoculated with samples isolated from the specimens and became infected by an intracellular bacterium. The entire genome of the infectious agent was sequenced (study accession PRJEB69484) and, based on nine taxonomic markers, was classified as a novel species belonging to the Chlamydia genus (DSMZ no. 117479, CSUR no. QA1836). We propose the name Chlamydia vaughanii sp. nov., in memory of the late Professor Lloyd Vaughan. C. vaughanii has the largest genome (1.3 Mbp) of the Chlamydia genus. This appears to be a consequence of multiple duplications in genes encoding putative adhesins. Like other pathogenic Chlamydia, it can infect mammalian cells, but it cannot infect either insect or amoeba cells. It additionally can grow in Epithelioma papulosum cyprinis (EPC) cells (fathead minnow, ATCC CRL-2872) but only when cultivated at 30 °C. We developed a C. vaughanii-specific quantitative PCR which amplifies the mutS gene and analysed several samples from the aquarium. C. vaughanii was retrieved from all deceased A. dolichopterus fish, but not from any other sample in the aquarium, suggesting that it indeed originated from the fish and was not a contaminant. C. vaughanii is the first Chlamydia isolated from fish.

Soft tissue tumors/sarcomas (STSs) in felines, encompassing a variety of mesenchymal tumors with similar histomorphological features, present diagnostic challenges due to their diverse cellular origins and the overlap with other tumor types such as feline sarcoid. This study aimed to delineate the clinical, histomorphological, and immunohistochemical characteristics of 34 feline facial spindle cell tumors affecting 29 cats, including testing for bovine papillomavirus type 14 (BPV14), the virus causing feline sarcoids. Only five out of 12 tumors previously diagnosed as feline sarcoids based on histomorphology were confirmed by PCR for BPV14, underscoring the importance of comprehensive diagnostic approaches to accurately distinguish between STSs and feline sarcoids. This study shows that most facial spindle cell tumors were compatible with peripheral nerve sheath tumors (PNSTs) based on positive immunohistochemical staining for Sox10 and other immunohistochemical markers such as GFAP, NSE, and S100. Some of these tumors displayed as multiple independent masses on the face or as erosive and ulcerative lesions without obvious mass formation, an atypical presentation and an important highlight for general practitioners, dermatologists, and oncologists. This study also describes periadnexal whorling of neoplastic cells as a novel histomorphologic finding in feline facial PNSTs and emphasizes Sox10 as a useful complementary immunohistochemical marker for the diagnosis of facial PNST in cats, providing valuable insights for veterinary pathologists.