The Experimental Transmission of Human Intestinal Protozoan Parasites:

Rendtorff, Robert C.; Holt, Carvel J.

doi:10.1093/oxfordjournals.aje.a119756

Cited by 93 publications

(126 citation statements)

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“…We preface any such discussion of quantitative comparisons with the caveat that additional research on MID and carrying capacities would dramatically improve these estimates. Nonetheless, we estimate that the infectious dose for giardiasis is slightly higher than the typical density in natural water reservoirs (Rendtorff, 1954;LeChevallier et al, 1991). The MID would be much lower for the immuno-compromised, thus lower than the density in aquatic reservoirs.…”

Section: Two Measures Of Distance To An Epidemicmentioning

confidence: 67%

“…Further, variation in the disease threshold due to heterogeneity in innate immune systems may also play a key role in facilitating movement of pathogens from reservoirs to humans. On the other hand, if the (Kaper et al, 1995) ( Levine et al, 1981;(Brayton et al, 1987) Colwell et al, 1996 Cryptosporidiosis 10 8 100-300 1-5 (DuPont et al, 1995) (LeChevallier et al, 1991) Giardiasis 10 8 -10 9 10-100 1-5 (Rendtorff, 1954) (Rendtorff, 1954) (LeChevallier et al, 1991) Rotavirus disease 10 12 -10 13 100 10-1000 (White and Fenner, 1994) (Ward et al, 1986) Disease B I Cholera 10-100 0.001-1 Cryptosporidiosis 20-300 0.01-1 Giardiasis 1-100 0.01-0.1 Rotavirus disease <10 NA minimum pathogen density fluctuation to cause an epidemic or endemic is small, maintaining or lowering in-reservoir pathogen density will prevent the disease. For diseases with nonhuman alternative hosts, controlling alternative zoonotic hosts for pathogens can be an effective approach.…”

Section: Two Measures Of Distance To An Epidemicmentioning

confidence: 99%

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Dynamics of Indirectly Transmitted Infectious Diseases with Immunological Threshold

et al. 2008

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There are numerous examples of human pathogens which persist in environmental reservoirs while infectious outbreaks remain rare. In this manuscript, we consider the dynamics of infectious diseases for which the primary mode of transmission is indirect and mediated by contact with a contaminated reservoir. We evaluate the realistic scenario in which the number of ingested pathogens must be above a critical threshold to cause infection in susceptible individuals. This minimal infectious dose is a consequence of the clearance effect of the innate immune system. Infected individuals shed pathogens back into the aquatic reservoir, indirectly increasing the transmittability of the pathogen to the susceptible. Building upon prior works in the study of cholera dynamics, we introduce and analyze a family of reservoir mediated SIR models with a threshold pathogen density for infection. Analyzing this family of models, we show that an outbreak can result from noninfinitesimal introductions of either infected individuals or additional pathogens in the reservoir. We devise two new measures of how likely it is that an environmentally persistent pathogen will cause an outbreak: (i) the minimum fraction of infected individuals; and (ii) the minimum fluctuation size of in-reservoir pathogens. We find an additional control parameter involving the shedding rate of infected individuals, which we term the pathogen enhancement ratio, which determines whether outbreaks lead to epidemics or endemic disease states. Thus, the ultimate outcome of disease is controlled by the strength of fluctuations and the global stability of a nonlinear dynamical system, as opposed to conventional analysis in which disease reflects the linear destabilization of a disease free equilibrium. Our model predicts that in the case of waterborne diseases, suppressing the pathogen density in aquatic reservoirs may be more effective than minimizing the number of infected individuals.

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Section: Two Measures Of Distance To An Epidemicmentioning

confidence: 67%

Section: Two Measures Of Distance To An Epidemicmentioning

confidence: 99%

Dynamics of Indirectly Transmitted Infectious Diseases with Immunological Threshold

et al. 2008

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“…Such levels of potentially infective organisms ensure a high level of environmental contamination, and increases the risk of infection for other susceptible animals, and possibly human beings, if ingested. Whereas the minimum infectious dose of Giardia for man is 10-100 cysts [12], the minimum infectious dose of Cryptosporidium for man is unknown. However, as few as 10 oocysts can produce infection in non-human juvenile primates [13].…”

Section: Methodsmentioning

confidence: 99%

Occurrence ofGiardiasp. cysts andCryptosporidiumsp. oocysts in faeces from public parks in the west of Scotland

et al. 1993

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SUMMARYOne hundred faecal specimens, randomly collected from various locations within seven public parks in the west of Scotland, were examined for the presence of Giardia sp. cysts and Cryptosporidium sp. oocysts. Eleven percent of samples contained Giardia sp. cysts and 1 % contained Cryptosporidium sp. oocysts. Occurrence data from individual parks varied from 0 to 40 % for Giardia and 0 to 2 4 % for Cryptosporidium. The occurrence of parasitic organisms in public parks, especially in the vicinity of children's playing areas is a matter of concern for public health officials and regulators of leisure and recreation amenities.

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“…Giardiasis may be a self-limiting infection and, even in the presence of persistent excretion of cysts, symptoms often abate and resolve, perhaps because of a reduction in numbers of trophozoites in the small intestine. 21 Additionally, patients may improve because of the intermittent nature of symptoms of giardiasis. 1,15,22 Therefore, patients with intermittent symptoms might delay seeking care, as it may be difficult to distinguish the spontaneous waning of symptoms from disease resolution.…”

Section: Discussionmentioning

confidence: 99%

Care-seeking behaviour and diagnostic processes for symptomatic giardiasis in children attending an academic paediatric hospital

Escobedo¹,

Almirall²,

Ávila

et al. 2014

Pathogens and Global Health

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Giardiasis is one of the commonest intestinal parasitic infections in Cuba. In order to determine careseeking behaviour and diagnostic processes in paediatric in-patients with giardiasis, structured questionnaires were administered by interview mothers of children with giardiasis during January to December 2010. During the study period, 97 children were diagnosed with giardiasis, of whom 86 (88.6%) caregivers were interviewed. The median number of days from symptoms onset to the first presentation in a health unit was 2 days (range: 0-15 days). The pattern of care-seeking behaviour was variable; 41 (47.7%) of children initially visited the emergency unit in a paediatric hospital. Sixty-six children had, at least, one further contact for help before diagnosis of giardiasis was made (range: 1-5 contacts) and of the 128 contact visits, 94 (73.4%) were also targeted more to hospitals. There was a median time of 6 days between the first presentation to a health unit until diagnosis, which was mainly made by microscopic examination of duodenal aspiration. Among factors investigated in mothers, only knowing other person with giardiasis had significant association with their ability to suspect giardiasis [odds ratio (OR): 29.8, 95% confidence interval (CI): 3.71-239.4, P50.001]. Requesting a faecal specimen or ordering duodenal aspiration for microscopic examination during the first visit appeared associated with correct diagnosis (OR: 3.84, 95% CI: 1.57-9.40, P50.003). Efforts should be made to increase doctors' awareness of-and diagnostic skills for childhood giardiasis. At the same time, it is necessary to improve caregivers' awareness about giardiasis.

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The Experimental Transmission of Human Intestinal Protozoan Parasites:

Cited by 93 publications

References 0 publications

Dynamics of Indirectly Transmitted Infectious Diseases with Immunological Threshold

Dynamics of Indirectly Transmitted Infectious Diseases with Immunological Threshold

Occurrence ofGiardiasp. cysts andCryptosporidiumsp. oocysts in faeces from public parks in the west of Scotland

Care-seeking behaviour and diagnostic processes for symptomatic giardiasis in children attending an academic paediatric hospital

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