Cryptosporidium: from laboratory diagnosis to surveillance and outbreaks

Abstract

Summary :The burden of disease caused by the protozoan parasite Cryptosporidium is unknown. However, routine laboratory diagnosis and surveillance enables the basic epidemiology to be described, changes to be monitored and under-ascertainment to be measured. Although the two main species involved in human disease in developed countries, Cryptosporidium parvum and Cryptosporidium hominis, have differing epidemiologies and risk factors, national surveillance is generally from isolates identified to the genus level only. Enhancing the data by typing, at least to identify the isolates to the species level, removes some of the noise generated and better identifies the risks than when reports are not species-specific. This level of identification is also valuable for outbreak investigations, but further investigation of the population genetics of C. parvum and C. hominis is required for the development of more readily applied subtyping tools.

Comparison of the Triage Micro Parasite Panel and Microscopy for the Detection ofEntamoeba histolytica/Entamoeba dispar,Giardia lamblia, andCryptosporidium parvumin Stool Samples Collected in Kenya

“…These three samples could have contained low levels of C. parvum oocysts that the assay was unable to detect. The shedding of C. parvum oocysts in the stool can be sporadic, and the infective dose required can be quite low as well [29, 30]. Though the numbers of positive samples were not as high as in the study conducted by Garcia et al, they were comparable to other studies that have compared the sensitivity and specificity of O&P examination and the Triage Micro Parasite Panel [18, 19, 21].…”

Cryptosporidiosis - From Epidemiology to Treatment

“…However, Cryptosporidium presents two main problems for the isolation of DNA; the robust nature of the oocysts, requiring a disruption step prior to DNA extraction and the richness of PCR inhibitors in the sample matrix, requiring separation during DNA extraction. Currently, there is no international consensus of typing methods and many rely on DNA sequence analysis which can be time-consuming and costly (Chalmers, 2008). In 1991, Mark Laxer was the first to apply PCR to the detection of Cryptosporidium oocysts (Laxer et al, 1991).…”

“…With Masson's stain, a small red nucleus and blue cytoplasm can be distinguished in many of the organisms. Species identification is an important element of outbreak investigations particularly where the source is not clear, and it is important that this is underpinned by routine species identification to establish the background epidemiology (Chalmers, 2008). Even though oocysts of many Cryptosporidium spp are morphologically similar, morphometric measurement of oocysts can play a vital role in the differentiation of some Cryptosporidium spp.…”

“…However, laboratory techniques are unable to discriminate between the two main species involved in human disease, C. hominis and C. parvum. Species identification can be achieved with molecular methods which provide a precious tool for detecting Cryptosporidium and differentiating species in biological samples of infected patients (Chalmers, 2008). However, Cryptosporidium presents two main problems for the isolation of DNA; the robust nature of the oocysts, requiring a disruption step prior to DNA extraction and the richness of PCR inhibitors in the sample matrix, requiring separation during DNA extraction.…”

“…There are currently 16 recognized species of Cryptosporidium, which have been isolated from a large variety of hosts (Table 1), (Xiao et al, 2004) : C. parvum, C. hominis, C. felis, C. canis, C. wrairi, C. varanii, C. suis, C. bovis, C. andersoni, C. muris, C. serpentis, C. galli, C. meleagridis, C. molnari, C. scophithalmi and C. baileyi. The four basic requirements for the naming of Cryptosporidium species are (Xiao, 2010;Chalmers, 2008) felis, C. canis, C. suis, C. muris and C. andersoni, although some are reported extremely rarely, particularly the latter three species, and the pathogenicity of some species for man has not been proven (Chalmers, 2008). C. hominis and C. parvum are recognized globally as the most important Cryptosporidium species infecting humans (Dunand et al, 1997; Two different types of oocysts are produced, the thick-walled, which is commonly excreted from the host, and the thin-walled oocyst, which is primarily involved in autoinfection.…”