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Licentiate thesis, 2019

Infection dynamics of Cryptosporidium bovis and Cryptosporidium ryanae in cattle

Åberg, Malin

Abstract

In order to investigate the infection dynamics of the protozoan parasites Cryptosporidium bovis and Cryptosporidium ryanae in cattle, a Swedish dairy farm known to be free of C. parvum was recruited. Two sampling regimes were utilized; a cross-sectional study of pre-weaned calves over one year (study I), and a two-year prospective cohort study (study II). In study I, feces samples were collected from up to twenty calves once a month (13 occasions). In study II samples were collected from 16 heifers from birth to calving. They were sampled once a week for two months, and then monthly until calving. The samples were cleaned using a flotation method and examined with immunofluorescence microscopy to quantify the shedding. The Cryptosporidium positive samples were further processed with molecular species determination.

In study I, a total of 238 samples were examined and oocysts were found in 92 samples, of which 72 were successfully species determined: 87.5% were C. bovis, 9.7% were C. ryanae and 2.8% were a mix of both species. In the cohort (study II), a total of 455 samples were collected and for calves up to nine weeks old, C. bovis was found in 58.5% of the samples, C. ryanae in 9.2%, and both C. bovis and C. ryanae in 3.1%. No parvum was found in either study.

The prevalence of shedding calves was at its highest at ages four and five weeks in both studies: 54.8% and 56.7% in study I, 81.3% and 87.5% in study II. The cumulative incidence in the cohort reached 100% when the calves were five weeks old, which is earlier than what many international studies have shown for C. bovis.

The highest oocysts per gram feces count (OPG) were 1.1 × 106 and 3.6 × 106 in study I and study II, respectively. The youngest calf in which C. bovis was identified was 5 days old, and the youngest calf in which C. ryanae was identified was 15 days old. In four calves in study II, the detected species changed from C. bovis to C. ryanae or the other way around, and two samples were a combination of both species. Several individuals shed oocysts sporadically up to 16 months of age. Calf housing type and seasonality were not associated with differences in the shedding of oocysts (I). There was no association between the presence of diarrhea and oocyst shedding.

Keywords

Cryptosporidium; C. bovis; C. ryanae; cohort; infection dynamics

Published in


ISBN: 978-91-576-9699-1, eISBN: 978-91-576-9700-4
Publisher: Department of Clinical Sciences, Swedish University of Agricultural Sciences

Authors' information

Åberg, Malin
Swedish University of Agricultural Sciences, Department of Clinical Sciences

UKÄ Subject classification

Clinical Science

URI (permanent link to this page)

https://res.slu.se/id/publ/103377