Biodiversity and host-parasite cophylogeny of Sphaerospora (sensu stricto) (Cnidaria: Myxozoa)

BACKGROUND

Myxozoa are extremely diverse microscopic parasites belonging to the Cnidaria. Their life-cycles alternate between vertebrate and invertebrate hosts, predominantly in aquatic habitats. Members of the phylogenetically well-defined Sphaerospora (sensu stricto) clade predominantly infect the urinary system of marine and freshwater fishes and amphibians. Sphaerosporids are extraordinary due to their extremely long and unique insertions in the variable regions of their 18S and 28S rDNA genes and due to the formation of motile proliferative stages in the hosts' blood. To date, DNA sequences of only 19 species have been obtained and information on the patterns responsible for their phylogenetic clustering is limited.

METHODS

We screened 549 fish kidney samples from fish of various geographical locations, mainly in central Europe, to investigate sphaerosporid biodiversity microscopically and by 18S rDNA sequences. We performed multiple phylogenetic analyses to explore phylogenetic relationships and evolutionary trends within the Sphaerospora (s.s.) clade, by matching host and habitat features to the resultant 18S rDNA trees. The apparent co-clustering of species from related fish hosts inspired us to further investigate host-parasite co-diversification, using tree-based (CoRE-PA) and distance-based (ParaFit) methods.

RESULTS

Our study considerably increased the number of 18S rDNA sequence data for Sphaerospora (s.s.) by sequencing 17 new taxa. Eight new species are described and one species (Sphaerospora diminuta Li & Desser, 1985) is redescribed, accompanied by sufficient morphological data. Phylogenetic analyses showed that sphaerosporids cluster according to their vertebrate host order and habitat, but not according to geography. Cophylogenetic analyses revealed a significant congruence between the phylogenetic trees of sphaerosporids and of their vertebrate hosts and identified Cypriniformes as a host group of multiple parasite lineages and with high parasite diversity.

CONCLUSIONS

This study significantly contributed to our knowledge of the biodiversity and evolutionary history of the members of the Sphaerospora (s.s.) clade. The presence of two separate phylogenetic lineages likely indicates independent historical host entries, and the remarkable overlap of the larger clade with vertebrate phylogeny suggests important coevolutionary adaptations. Hyperdiversification of sphaerosporids in cypriniform hosts, which have undergone considerable radiations themselves, points to host-driven diversification.

Benchmarking cataract surgery outcomes in an ethnically diverse and diabetic population: final post-operative visual acuity and rates of post-operative cystoid macular oedema

PurposeTo determine visual acuity and rates of post-operative cystoid macular oedema (CMO) in an ethnically diverse and predominantly diabetic population.MethodsThe study was undertaken over a one year period. Snellen visual acuity (VA) was measured pre and 4-8 weeks post-operatively and optical coherence topography (OCT) was performed at baseline and post-operatively. No eyes received prophylactic non-steroidal anti-inflammatory drugs (NSAIDs) prior to or after surgery.ResultsOut of 262 eyes, 59% were in the Black, Asian and minority ethnic group (BAME), 57% had a history of diabetes mellitus and 34% had pre-existing diabetic retinopathy. 76% of all eyes achieved 6/12 post-operative VA at the first postoperative review and the incidence of post-operative CMO within the study population was 7.6%. In patients with a history of diabetes mellitus the incidence of post-operative CMO was 10.7% compared to 3.5% in those without diabetes. This was found to be clinically significant (P=0.0297).ConclusionWe believe this is the first study to benchmark standards for care in this demographic of patients. A history of diabetes mellitus, irrespective of whether there is diabetic retinopathy or not, is an independent risk factor for the development of post-operative CMO in patients undergoing cataract surgery (P=0.0297). Ethnicity is not an independent risk factor for the development of post-operative CMO.

Molecular fingerprinting of the myxozoan community in common carp suffering swim bladder inflammation (SBI) identifies multiple etiological agents

Background

Swim bladder inflammation (SBI) is an important disease of common carp fingerlings in Central Europe. In the 1980s, its etiology was ascribed to multicellular proliferative stages of the myxozoan parasite Sphaerospora dykovae (formerly S. renicola). S. dykovae was reported to proliferate in the blood and in the swim bladder prior to the invasion of the kidney, where sporogony takes place. Due to the presence of emerging numbers of proliferative myxozoan blood stages at different carp culture sites in recent years we analysed cases of SBI, for the first time, using molecular diagnostics, to identify the myxozoan parasites present in diseased swim bladders.

Methods

We amplified myxozoan SSU rDNA in a non-specific approach and compared the species composition in swim bladders at culture sites where carp demonstrated 1. No signs of SBI, 2. Minor pathological changes, and 3. Heavy SBI. Based on DNA sequences, we determined the localisation and distribution of the most frequent species by in situ hybridisation, thereby determining which myxozoans are involved in SBI.

Results

Large multicellular myxozoan swim bladder stages characterised heavy SBI cases and were identified as S. dykovae, however, blood stages were predominantly represented by Sphaerospora molnari, whose numbers were greatly increased in carp with mild and heavy SBI, compared with SBI-free fish. S. molnari was found to invade different organs and cause inflammatory changes also in the absence of S. dykovae. One site with mild SBI cases was characterised by Buddenbrockia sp. infection in different organs and a general granulomatous response.

Conclusions

We provide evidence that the etiology of SBI can vary in relation to culture site and disease severity and that emerging numbers of S. molnari in the blood represent an important co-factor or precondition for SBI.

Endovascular management of proximal lower limb deep venous thrombosis - A prospective study with six-month follow-up

BACKGROUND

Catheter-directed thrombolysis with assisted mechanical thrombolysis is the standard of medical care for proximal deep vein thrombosis. We studied the immediate and intermediate (six months) safety and effectiveness of catheter-directed thrombolysis in patients with proximal lower limb deep vein thrombosis.

METHODOLOGY

Thirty consecutive patients aged between 20 and 70 years with proximal lower limb deep vein thrombosis formed the study group. Catheter-directed thrombolysis was done with streptokinase infuse through a catheter kept in the ipsilateral popliteal vein. Unfractionated heparin was given along with streptokinase. Mechanical thromboaspiration using guiding catheter was performed in addition to thrombolytic therapy. After six months, post-thrombotic syndrome and deep venous patency were assessed by using Villalta scale and duplex ultrasound, respectively.

RESULTS

Thirty patients with proximal lower limb deep vein thrombosis were treated with catheter-directed thrombolysis. Mean age of the study patients was 41.7 ± 15 years. Mean duration of illness was 13.3 ± 12 days. The mean duration of thrombolysis was 4.5 ± 1.3 days. Grade III (complete) lysis was achieved in 10 (33%) and Grade II (50-90%) lysis in 20 (67%) of patients. Patients with significant residual lesion in Grade II lysis following catheter-directed thrombolysis underwent percutaneous transluminal angioplasty alone (12/20) or venous stenting (8/20). All patients improved clinically following catheter-directed thrombolysis or assisted catheter-directed thrombolysis. Four patients (13%) developed pulmonary embolism during course of hospital stay and among them two (6.5%) patients died. Eleven patients (37%) had minor bleeding or hematoma at local site, and seven (23%) developed anemia requiring blood transfusion and four (13%) patients had thrombocytopenia. After six months, iliofemoral patency was found in 20 (72%) and post-thrombotic syndrome was seen in six (21%) patients. Two (6.5%) patients died during follow-up due to nephrotic syndrome and carcinoma breast.

CONCLUSION

Catheter-directed thrombolysis and conventional manual aspiration thrombectomy are an effective treatment for proximal lower extremity deep vein thrombosis with good short and intermediate outcome.

Hidden diversity and evolutionary trends in malacosporean parasites (Cnidaria: Myxozoa) identified using molecular phylogenetics

Malacosporeans represent a small fraction of myxozoan biodiversity with only two genera and three species described. They cycle between bryozoans and freshwater fish. In this study, we (i) microscopically examine and screen different freshwater/marine fish species from various geographic locations and habitats for the presence of malacosporeans using PCR; (ii) study the morphology, prevalence, host species/habitat preference and distribution of malacosporeans; (iii) perform small subunit/large subunit rDNA and Elongation factor 2 based phylogenetic analyses of newly gathered data, together with all available malacosporean data in GenBank; and (iv) investigate the evolutionary trends of malacosporeans by mapping the morphology of bryozoan-related stages, host species, habitat and geographic data on the small subunit rDNA-based phylogenetic tree. We reveal a high prevalence and diversity of malacosporeans in several fish hosts in European freshwater habitats by adding five new species of Buddenbrockia and Tetracapsuloides from cyprinid and perciform fishes. Comprehensive phylogenetic analyses revealed that, apart from Buddenbrockia and Tetracapsuloides clades, a novel malacosporean lineage (likely a new genus) exists. The fish host species spectrum was extended for Buddenbrockia plumatellae and Buddenbrockia sp. 2. Co-infections of up to three malacosporean species were found in individual fish. The significant increase in malacosporean species richness revealed in the present study points to a hidden biodiversity in this parasite group. This is most probably due to the cryptic nature of malacosporean sporogonic and presporogonic stages and mostly asymptomatic infections in the fish hosts. The potential existence of malacosporean life cycles in the marine environment as well as the evolution of worm- and sac-like morphology is discussed. This study improves the understanding of the biodiversity, prevalence, distribution, habitat and host preference of malacosporeans and unveils their evolutionary trends.