Surface Waters and Urban Brown Rats as Potential Sources of Human-Infective Cryptosporidium and Giardia in Vienna, Austria

Abstract

Cryptosporidium and Giardia are waterborne protozoa that cause intestinal infections in a wide range of warm-blooded animals. Human infections vary from asymptomatic to life-threatening in immunocompromised people, and can cause growth retardation in children. The aim of our study was to assess the prevalence and diversity of Cryptosporidium and Giardia in urban surface water and in brown rats trapped in the center of Vienna, Austria, using molecular methods, and to subsequently identify their source and potential transmission pathways. Out of 15 water samples taken from a side arm of the River Danube, Cryptosporidium and Giardia (oo)cysts were detected in 60% and 73% of them, with concentrations ranging between 0.3–4 oocysts/L and 0.6–96 cysts/L, respectively. Cryptosporidium and Giardia were identified in 13 and 16 out of 50 rats, respectively. Eimeria, a parasite of high veterinary importance, was also identified in seven rats. Parasite co-ocurrence was detected in nine rats. Rat-associated genotypes did not match those found in water, but matched Giardia previously isolated from patients with diarrhea in Austria, bringing up a potential role of rats as sources or reservoirs of zoonotic pathogenic Giardia. Following a One Health approach, molecular typing across potential animal and environmental reservoirs and human cases gives an insight into environmental transmission pathways and therefore helps design efficient surveillance strategies and relevant outbreak responses.

Monitoring Urban Zoonotic Virus Activity: Are City Rats a Promising Surveillance Tool for Emerging Viruses?

“…As the likelihood of infection with viruses increases with age for many viruses, and many viral infections follow an acute course, there was a low probability of detecting active virus infections [9,10]. However, zoonotic infections were detected in the examined sample in previous studies [42,43,96], while viral infections have been detected in comparable [9,35,70,76] or lower [15,25,77] sample sizes, demonstrating that a modest sample size of the rat population enables to reveal current viral infections. Therefore, targeted surveillance of the rat population for zoonotic viral pathogens should focus on older rats, or at least attempt to include all age classes.…”

Methods used for concentrating oocysts of Cryptosporidium spp., spores Encephalitozoon spp. and Enterocytozoon spp. and their occurrence in Slovak water samples

“…The remaining parasites were also identified in rivers, lakes, drinking and wastewater. Cervero-Aragó et al (2021) detected from surface waters in Austria Cryptosporidium spp. in 60% of samples.…”