Author
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Fayer, Ronald |
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Submitted to: Meeting Abstract
Publication Type: Abstract Only Publication Acceptance Date: 9/8/2010 Publication Date: 5/2/2011 Citation: Fayer, R. 2011. Zoonotic cryptosporidiosis associated with livestock. Meeting Abstract. p3. Interpretive Summary: Technical Abstract: Cryptosporidium parvum is a zoonotic pathogen transmissible from a variety of animals to humans and is a considerable public health concern. Dairy cattle have been identified in numerous reports as a major source of environmental contamination with this pathogen. However, virtually all reports have been based on microscopic examination of the organism in feces from cattle on farms within a limited geographic area. A long term point preveance study has examined nearly 1000 cattle on 15 farms from 7 states from Vermont to Florida using molecular tools to identify the species and genotypes of Cryptosporidium. Results indicate that virtually all previous reports are misleading in identifying the presence and prevalence of C. parvum by microscopy. Structurally indistinguishable fecal stages to C. parvum were found in calves of all ages in the present study but gene sequencing identified distinct differences. Basically, nearly all of the Cryptosporidium excreted by pre-weaned calves was found to be C. parvum. In contrast, nearly all Cryptosporidium excreted by post-weaned calves were species other than C. parvum that have not been found infectious for humans. Cryptosporidium bovis and C. ryanae have oocysts that are morphologically indistinguishable from those of C. parvum and these have been detected in feces from pre-weaned and post-weaned calves, usually immediately after C. parvum infection has ended. This sequential series of infections with different species that appear microcopically similar has led to the mistaken conclusion that C. parvum, the only species tghat is both pathogenic and infectious for humans, is excreted by calves from approximately one week of age until several months of age. A longitudinal study on one farm involving calves from birth to 2 years of age has confirmed the findings of the multi-state study. |
