Risk Factors for Owner‐Reported Occurrence of Equine Protozoal Myeloencephalitis in the US Equine Population

Abstract

Background: Equine protozoal myeloencephalitis (EPM) is a serious and often fatal neurologic disease of horses, but few studies have investigated risk factors.Objectives: To evaluate operation-and individual-level factors associated with likelihood of the occurrence of EPM. Animals: Data were collected as part of a study of the US equine industry from 1,178 operations representing 83.9% of horses and 51.6% of operations with 3 horses in 28 states.Methods: Probability-based sampling was used to enroll representative operations in a cross-sectional study. Interviews were conducted to collect information regarding health and management of horses. A nested case-control study was used to investigate risk factors among individual horses. Interview data were combined with climate data, human population density, and opossum regional ecology categories. Data were analyzed using logistic regression to identify risk factors for the occurrence of EPM.Results: Owners reported that 95% of EPM cases included in this study were diagnosed by veterinarians. Variables associated with EPM occurrence on premises included opossum regional ecology, reported exposure to small wildlife, climate, terrain, housing, choice of bedding material, method of storing feeds, equine stocking density, and primary use of horses. Among individual horses, age was most strongly associated with disease risk. Associations also were identified with sex, breed, primary use, and participation in competitions.Conclusions and Clinical Importance: Because the risk of EPM occurrence on operations is closely tied to factors that impact exposure to opossums, their feces, and their environment, controlling these exposures may be important in preventing the occurrence of EPM.

Seroepidemiology of Sarcocystis neurona, Toxoplasma gondii and Neospora spp. among horses in the south of the state of Minas Gerais, Brazil

“…Given its high synanthropy, this species is a potential disseminator of pathogens between domestic animals and man (MULLER et al, 2005). This would explain the association between the presence of forest reserves either on the farms or bordering the farms and seropositivity for S. neurona, which has also been reported in other studies (MORLEY et al, 2008;DUBEY et al, 2015). The greater risk of infected animals found on farms that manufactured their own feed suggests that the storage of the raw material used in the formulation was inadequate, thus allowing access by wild animals (possums) to the food (MORLEY et al, 2008).…”

“…The prevalence of S. neurona among horses (26.0%) was within the range observed in previous studies conducted in Brazil, 37.7% (Western blot) in Rio Grande do Sul (LINS et al, 2012) and 8.3% (IFAT) in Rio de Janeiro (STELMANN, 2014), and worldwide, same 26.1% (Western blot) in Argentina (MORÉ et al, 2014) and 27.6% (IFAT) in EUA (PUSTERLA et al, 2014). The high prevalence among herds (88.3%) can be explained by the fact that most horses were reared in picket-fenced enclosures, thus facilitating their contact with wild fauna, which predisposed the animals towards infection by S. neurona (MORLEY et al, 2008). In addition, the presence of woodlands near the pastures in the absolute majority of the farms (90.57%), probably increased the risk of contact between horses and wild animals, such as possums (DUBEY et al, 2015).…”

An update on Sarcocystis neurona infections in animals and equine protozoal myeloencephalitis (EPM)

“…Although many neurologic disorders affect the horse, EPM remains the most commonly diagnosed infectious equine neurologic disease in the Americas (Dubey et al, 2001a; Morley et al, 2001; Furr et al, 2002; Morley et al, 2008). A complete neurologic examination and implementation of a thorough diagnostic plan to rule out differential diagnoses are essential prerequisites to laboratory testing and appropriate interpretation of clinical signs and death.…”

“…Only two epidemiologic studies have assessed the risk factors associated with clinical EPM in horses in the USA (Saville et al, 2000; Morley et al, 2008). One was done at a tertiary care facility (Saville et al, 2000), which was not an ideal population of horses to reflect risk factors on a national scale.…”

“…More than 900 operators completed survey questions regarding a Control Horse from premises where there is no history of EPM. The analysis was performed and the results were reported (Morley et al, 2008). The following conclusions were drawn:…”