Epidemiologic evidence for clustering of equine motor neuron disease in the United States

Ricardo de la Rúa-Domènech From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Ricardo de la Rúa-Domènech in
Current site
Google Scholar
PubMed
Close
 DMV
,
Hussni O. Mohammed From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Hussni O. Mohammed in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD
,
Edward R. Atwill From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Edward R. Atwill in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
John F. Cummings From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by John F. Cummings in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
,
Thomas J. Divers From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Thomas J. Divers in
Current site
Google Scholar
PubMed
Close
 DVM
,
Brian A. Summers From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Brian A. Summers in
Current site
Google Scholar
PubMed
Close
 BVSc, PhD
,
Alexander deLahunta From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Alexander deLahunta in
Current site
Google Scholar
PubMed
Close
 DVM, PhD
, and
Cindy Jackson From the Sections of Epidemiology (de la Rúa-Domènech, Mohammed, Atwill) and Medicine (Divers, Jackson), Department of Clinical Sciences, Department of Anatomy (Cummings, deLahunta), and Department of Pathology (Summers), College of Veterinary Medicine, Cornell University, Ithaca, NY 14853-6401.

Search for other papers by Cindy Jackson in
Current site
Google Scholar
PubMed
Close
 DVM

Click on author name to view affiliation information

Abstract

Objective

To examine the regional variations in the distribution of equine motor neuron disease (emnd) in the United States and the factors that might explain those variations.

Design

Cluster investigation and case-control study.

Sample population

The study population consisted of 97 horses with histopathologically confirmed emnd and 698 controls with diagnosis of other spinal cord disorders at 21 US veterinary teaching hospitals participating in the Veterinary Medical Data Base.

Procedure

The total horse population of the United States was divided into 21 regions, and the regional incidence rates of emnd from January 1985 through January 1995 were estimated. Moran's index of spatial autocorrelation was calculated to test for spatial clustering of the disease. The 21 regions were then joined in broader areas according to the similarity of their emnd rates by means of the cluster analysis statistical technique. Finally, the role of potential confounding factors (age at diagnosis, month of diagnosis, breed, and sex) in the present distribution of emnd was assessed, using logistic regression analysis.

Results

Differences in estimated rates across the 21 regions resulted in a strong pattern of spatial clustering of emnd in the United States. The geographic units were grouped into 5 risk regions, with the gradient of emnd incidence rates increasing from the western states (almost 0 cases/1,000,000 horse-years) toward New England (20.78 cases/1,000,000 horse-years). Reported risk factors of emnd (age, breed) and other extraneous factors (sex, month of diagnosis) could not explain the observed geographic variations of disease rates. Nevertheless, there is evidence of some confounding attributable to age and breed.

Conclusions

Although the mechanism responsible for the clustering of emnd in northeastern states is still unexplained, it is not an epiphenomenon caused by regional differences in the distribution of the factors investigated.

Abstract

Objective

To examine the regional variations in the distribution of equine motor neuron disease (emnd) in the United States and the factors that might explain those variations.

Design

Cluster investigation and case-control study.

Sample population

The study population consisted of 97 horses with histopathologically confirmed emnd and 698 controls with diagnosis of other spinal cord disorders at 21 US veterinary teaching hospitals participating in the Veterinary Medical Data Base.

Procedure

The total horse population of the United States was divided into 21 regions, and the regional incidence rates of emnd from January 1985 through January 1995 were estimated. Moran's index of spatial autocorrelation was calculated to test for spatial clustering of the disease. The 21 regions were then joined in broader areas according to the similarity of their emnd rates by means of the cluster analysis statistical technique. Finally, the role of potential confounding factors (age at diagnosis, month of diagnosis, breed, and sex) in the present distribution of emnd was assessed, using logistic regression analysis.

Results

Differences in estimated rates across the 21 regions resulted in a strong pattern of spatial clustering of emnd in the United States. The geographic units were grouped into 5 risk regions, with the gradient of emnd incidence rates increasing from the western states (almost 0 cases/1,000,000 horse-years) toward New England (20.78 cases/1,000,000 horse-years). Reported risk factors of emnd (age, breed) and other extraneous factors (sex, month of diagnosis) could not explain the observed geographic variations of disease rates. Nevertheless, there is evidence of some confounding attributable to age and breed.

Conclusions

Although the mechanism responsible for the clustering of emnd in northeastern states is still unexplained, it is not an epiphenomenon caused by regional differences in the distribution of the factors investigated.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 35 35 8
PDF Downloads 16 16 2
Advertisement