Cryptosporidium oocyst persistence in agricultural streams -a mobile-immobile model framework assessment

Modeling Contaminant Microbes in Rivers During Both Baseflow and Stormflow

Rivers transport contaminant microorganisms (including fecal indicator bacteria and human pathogens) long distances downstream of diffuse and point sources, posing a human health risk. We present a mobile-immobile model that incorporates transport as well as immobilization and remobilization of contaminant microbes and other fine particles during baseflow and stormflow. During baseflow conditions, hyporheic exchange flow causes particles to accumulate in streambed sediments. Remobilization of stored particles from streambed sediments occurs slowly during baseflow via hyporheic exchange flow, while remobilization is vastly increased during stormflow. Model predictions are compared to observations over a range of artificial and natural flood events in the dairy contaminated Topehaehae Stream, New Zealand. The model outputs closely matched timing and magnitude of E. coli and turbidity observations through multiple high-flow events. By accounting for both state-of-flow and hyporheic exchange processes, the model provides a valuable framework for predicting particle and contaminant microbe behavior in streams.

Analysis of Long Non-Coding RNA in Cryptosporidium parvum Reveals Significant Stage-Specific Antisense Transcription

Cryptosporidium is a protist parasite that has been identified as the second leading cause of moderate to severe diarrhea in children younger than two and a significant cause of mortality worldwide. Cryptosporidium has a complex, obligate, intracellular but extra cytoplasmic lifecycle in a single host. How genes are regulated in this parasite remains largely unknown. Long non-coding RNAs (lncRNAs) play critical regulatory roles, including gene expression across a broad range of organisms. Cryptosporidium lncRNAs have been reported to enter the host cell nucleus and affect the host response. However, no systematic study of lncRNAs in Cryptosporidium has been conducted to identify additional lncRNAs. In this study, we analyzed a C. parvum in vitro strand-specific RNA-seq developmental time series covering both asexual and sexual stages to identify lncRNAs associated with parasite development. In total, we identified 396 novel lncRNAs, mostly antisense, with 86% being differentially expressed. Surprisingly, nearly 10% of annotated mRNAs have an antisense transcript. lncRNAs occur most often at the 3' end of their corresponding sense mRNA. Putative lncRNA regulatory regions were identified and many appear to encode bidirectional promoters. A positive correlation between lncRNA and upstream mRNA expression was observed. Evolutionary conservation and expression of lncRNA candidates was observed between C. parvum, C. hominis and C. baileyi. Ten C. parvum protein-encoding genes with antisense transcripts have P. falciparum orthologs that also have antisense transcripts. Three C. parvum lncRNAs with exceptional properties (e.g., intron splicing) were experimentally validated using RT-PCR and RT-qPCR. This initial characterization of the C. parvum non-coding transcriptome facilitates further investigations into the roles of lncRNAs in parasite development and host-pathogen interactions.

Cryptosporidium and Giardia in dam water on sheep farms - An important source of transmission?

Cryptosporidium and Giardia infections can negatively impact livestock health and reduce productivity, and some species and genotypes infecting livestock have zoonotic potential. Infection occurs via the faecal-oral route. Waterborne infections are a recognised source of infection for humans, but the role of livestock drinking water as a source of infection in livestock has not been described. This study aimed to determine whether contaminated drinking water supplies, such as farm dams, are a likely transmission source for Cryptosporidium and Giardia infections for extensively managed sheep. Dam water samples (n = 47) were collected during autumn, winter and spring from 12 farm dams located on six different farms in south west Western Australia, and faecal samples (n = 349) were collected from sheep with access to these dams. All samples were initially screened for Cryptosporidium spp. at the 18S locus and Giardia spp. at the gdh gene using qPCR, and oocyst numbers were determined directly from the qPCR data using DNA standards calibrated by droplet digital PCR. Cryptosporidium-positive sheep faecal samples were typed and subtyped by sequence analysis of 18S and gp60 loci, respectively. Giardia-specific PCR and Sanger sequencing targeting tpi and gdh loci were performed on Giardia- positive sheep faecal samples to characterise Giardia duodenalis assemblages. To identify Cryptosporidium and Giardia spp. in dam water samples, next-generation sequencing analysis of 18S and gdh amplicons were performed, respectively. Two species of Cryptosporidium (Cryptosporidium xiaoi and Cryptospordium ubiquitum (subtype family XIIa)) were detected in 38/345 sheep faecal samples, and in water from 9/12 farm dams during the study period, with C. xiaoi the species most frequently detected in both faeces and dam water overall. Giardia duodenalis assemblages AI, AII and E were detected in 36/348 faecal samples and water from 10/12 farm dams. For dam water samples where oo/cysts were detected by qPCR, Cryptosporidium oocyst concentration ranged from 518-2429 oocysts/L (n = 14), and Giardia cyst concentration ranged from 102 to 1077 cysts/L (n = 17). Cryptosporidium and Giardia with zoonotic potential were detected in farm dam water, including C. ubiquitum, C. hominis, C. parvum, C. cuniculus, C. xiaoi, and G. duodenalis assemblages A, B and E. The findings suggest that dam water can be contaminated with Cryptosporidium species and G. duodenalis assemblages that may infect sheep and with zoonotic potential, and farm dam water may represent one source of transmission for infections.