Application of Sartwell's model (lognormal distribution of incubation periods) to age at onset and age at death of foals with Rhodococcus equi pneumonia as evidence of perinatal infection

Miriam L. Horowitz, Noah D. Cohen, Shinji Takai, Teotimu Becu, M. Keith Chaffin, Karin K. Chu, K G Magdesian, Ronald J. Martens

Research output: Contribution to journalArticle

83 Scopus citations

Abstract

The distributions of the incubation periods for infectious and neoplastic diseases originating from point-source exposures, and for genetic diseases, follow a lognormal distribution (Sartwell's model). Conversely, incubation periods in propagated outbreaks and diseases with strong environmental components do not follow a lognormal distribution. In this study Sartwell's model was applied to the age at onset and age at death of foals with Rhodococcus equi pneumonia. The age at onset of clinical signs and age at death were compiled for 107 foals that had been diagnosed with R equi pneumonia at breeding farms in Argentina and Japan. For each outcome (disease and death), these data followed a lognormal distribution. A group of 115 foals with colic from the University of California were used as a comparison group. The age at onset of clinical signs for these foals did not follow a lognormal distribution. These results were consistent with the hypothesis that foals are infected with R equi during the 1st several days of life, similar to a point-source exposure.

Original languageEnglish (US)
Pages (from-to)171-175
Number of pages5
JournalJournal of Veterinary Internal Medicine
Volume15
Issue number3
StatePublished - 2001

Keywords

  • Epidemiology
  • Horses
  • Natural history

ASJC Scopus subject areas

  • veterinary(all)

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