Tag Archives: microbial contaminants

Economic Assessment of Cryptosporidiosis Outbreak, Ireland

Chyzheuskaya A, Srivinas R, O’Donovan D, Prendergast M, O’Donoghue C, Morris D. Economic Assessment of Waterborne Outbreak of Cryptosporidiosis. Emerging infectious diseases. 2017 Oct;23(10):1650-1656. doi: 10.3201/eid2310.152037.

In 2007, a waterborne outbreak of Cryptosporidium hominis infection occurred in western Ireland, resulting in 242 laboratory-confirmed cases and an uncertain number of unconfirmed cases. A boil water notice was in place for 158 days that affected 120,432 persons residing in the area, businesses, visitors, and commuters. This outbreak represented the largest outbreak of cryptosporidiosis in Ireland. The purpose of this study was to evaluate the cost of this outbreak. We adopted a societal perspective in estimating costs associated with the outbreak. Economic cost estimated was based on totaling direct and indirect costs incurred by public and private agencies. The cost of the outbreak was estimated based on 2007 figures. We estimate that the cost of the outbreak was >€19 million (≈€120,000/day of the outbreak). The US dollar equivalent based on today’s exchange rates would be $22.44 million (≈$142,000/day of the outbreak). This study highlights the economic need for a safe drinking water supply.

C. hominis, C. parvum dominant in China

Feng Y, Xiao L. Molecular Epidemiology of Cryptosporidiosis in China. Frontiers in microbiology. 2017 Sep 6;8:1701. doi: 10.3389/fmicb.2017.01701.

Molecular epidemiology of cryptosporidiosis is an active research area in China. The use of genotyping and subtyping tools in prevalence studies has led to the identification of unique characteristics of Cryptosporidium infections in humans and animals. Human cryptosporidiosis in China is exemplified by the high diversity of Cryptosporidium spp. at species and subtype levels, with dominant C. hominis and C. parvum subtypes being rarely detected in other countries. Similarly, preweaned dairy calves, lambs, and goat kids are mostly infected with non-pathogenic Cryptosporidium species (C. bovis in calves and C. xiaoi in lambs and goat kids), with C. parvum starting to appear in dairy calves as a consequence of concentrated animal feeding operations. The latter Cryptosporidium species is dominated by IId subtypes, with IIa subtypes largely absent from the country. Unlike elsewhere, rodents in China appear to be commonly infected with C. parvum IId subtypes, with identical subtypes being found in these animals, calves, other livestock, and humans. In addition to cattle, pigs and chickens appear to be significant contributors to Cryptosporidium contamination in drinking water sources, as reflected by the frequent detection of C. suis, C. baileyi, and C. meleagridis in water samples. Chinese scientists have also made significant contributions to the development of new molecular epidemiological tools for Cryptosporidium spp. and improvements in our understanding of the mechanism involved in the emergence of hyper-transmissible and virulent C. hominis and C. parvum subtypes. Despite this progress, coordinated research efforts should be made to address changes in Cryptosporidium transmission because of rapid economic development in China and to prevent the introduction and spread of virulent and zoonotic Cryptosporidium species and subtypes in farm animals.

Climate Changes and Human Pathogens Study Misleading

This study (here) of the affect of climate sensitivity on human pathogens is a literature search. The basic thesis being presented is that global warming will result in greater numbers of pathogens which in turn will result in more human illness. This line of thinking makes several assumptions. It might be useful in generating hypotheses for future surveillance but is inadequate for predicting future illness. Why? Because literature reviews are limited by what is called “publication bias”. That is, only certain articles and studies are publishable and others important studies relevant to this review are not published. Studies with negative findings are rarely published. Also, some studies are screened out because of reviewer bias. We can learn from this review but its interpretation is limited. 

Indeed, survival of some pathogens may be expected to decrease.  The authors themselves acknowledge:

“Although this study identifies a high degree of climate sensitivity among important pathogens, their response to climate change will be dependent on the nature of their association with climate drivers and impacts of other drivers.”

V. cholerae can survive in the river systems, Bangladesh

Grant SL, Tamason CC, Hoque BA, Jensen PK. Drinking cholera: salinity levels and palatability of drinking water in coastal Bangladesh. Trop Med Int Health. 2015 Apr;20(4):455-61. doi: 10.1111/tmi.12455. 

OBJECTIVES: To measure the salinity levels of common water sources in coastal Bangladesh and explore perceptions of water palatability among the local population to investigate the plausibility of linking cholera outbreaks in Bangladesh with ingestion of saline-rich cholera-infected river water.

METHODS: Hundred participants took part in a taste-testing experiment of water with varying levels of salinity. Salinity measurements were taken of both drinking and non-drinking water sources. Informal group discussions were conducted to gain an in-depth understanding of water sources and water uses.

RESULTS: Salinity levels of non-drinking water sources suggest that the conditions for Vibrio cholerae survival exist 7-8 days within the local aquatic environment. However, 96% of participants in the taste-testing experiment reported that they would never drink water with salinity levels that would be conducive to V. cholerae survival. Furthermore, salinity levels of participant’s drinking water sources were all well below the levels required for optimal survival of V. cholerae. Respondents explained that they preferred less salty and more aesthetically pleasing drinking water.

CONCLUSION: Theoretically, V. cholerae can survive in the river systems in Bangladesh; however, water sources which have been contaminated with river water are avoided as potential drinking water sources. Furthermore, there are no physical connecting points between the river system and drinking water sources among the study population, indicating that the primary driver for cholera cases in Bangladesh is likely not through the contamination of saline-rich river water into drinking water sources.

Warmer Temperatures Might Actually Enhance Predator Control of Parasites

Spencer R. Hall, Alan J. Tessier, Meghan A. Duffy, Marianne Huebner, and Carla E. Cceres. Warmer Does Not Have to Mean Sicker: Temperature and Predators can Jointly Drive Timing of Epidemics. Ecology, 87(7), 2006, pp. 1684-1695

Ecologists and epidemiologists worry that global warming will increase disease prevalence. These fears arise because several direct and indirect mechanisms link warming to disease, and because parasite outbreaks are increasing in many taxa. However, this outcome is not a foregone conclusion, as physiological and community-interaction-based mechanisms may inhibit epidemics at warmer temperatures. Here, we explore this thermal-community ecology-based mechanism, centering on fish predators that selectively prey upon Daphnia infected with a fungal parasite. We used an interplay between a simple model built around this system’s biology and laboratory experiments designed to parameterize the model. Through this data-model interaction, we found that a given density of predators can inhibit epidemics as temperatures rise when thermal physiology of the predator scales more steeply than that of the host. This case is met in our nsh-Daphnia-iungus system. Furthermore, the combination of steeply scaling parasite physiology and predation-induced mortality can inhibit epidemics at lower temperatures. This effect may terminate fungal epidemics of Daphnia as lakes cool in autumn. Thus, predation and physiology could constrain epidemics to intermediate temperatures (a pattern that we see in our system). More generally, these results accentuate the possibility that warmer temperatures might actually enhance predator control of parasites.

Wild Geese and Swans May Transmit Avian Influenza Virus, Salmonella, Campylobacter, and Antibiotic Resistance

Elmberg J, Berg C, Lerner H, Waldenström J, Hessel R. Potential disease transmission from wild geese and swans to livestock, poultry and humans: a review of the scientific literature from a One Health perspective. Infection ecology and epidemiology. 2017 Apr 10;7(1):1300450. doi: 10.1080/20008686.2017.1300450.

There are more herbivorous waterfowl (swans and geese) close to humans, livestock and poultry than ever before. This creates widespread conflict with agriculture and other human interests, but also debate about the role of swans and geese as potential vectors of disease of relevance for human and animal health. Using a One Health perspective, we provide the first comprehensive review of the scientific literature about the most relevant viral, bacterial, and unicellular pathogens occurring in wild geese and swans. Research thus far suggests that these birds may play a role in transmission of avian influenza virus, Salmonella, Campylobacter, and antibiotic resistance. On the other hand, at present there is no evidence that geese and swans play a role in transmission of Newcastle disease, duck plague, West Nile virus, Vibrio, Yersinia, Clostridium, Chlamydophila, and Borrelia. Finally, based on present knowledge it is not possible to say if geese and swans play a role in transmission of Escherichia coli, Pasteurella, Helicobacter, Brachyspira, Cryptosporidium, Giardia, and Microsporidia. This is largely due to changes in classification and taxonomy, rapid development of identification methods and lack of knowledge about host specificity. Previous research tends to overrate the role of geese and swans as disease vectors; we do not find any evidence that they are significant transmitters to humans or livestock of any of the pathogens considered in this review. Nevertheless, it is wise to keep poultry and livestock separated from small volume waters used by many wild waterfowl, but there is no need to discourage livestock grazing in nature reserves or pastures where geese and swans are present. Under some circumstances it is warranted to discourage swans and geese from using wastewater ponds, drinking water reservoirs, and public beaches. Intensified screening of swans and geese for AIV, West Nile virus and anatid herpesvirus is warranted.