Prevalence of Equus caballus Papillomavirus Type-2 Infection and Seropositivity in Asymptomatic Western Canadian Horses.

The study provides insight into the prevalence of Equus caballus Papillomavirus type 2 (EcPV-2), a virus potentially linked to certain cancers in horses, in Western Canada. The research discovered a higher rate of the asymptomatic infection in horses than previously expected and indicated the possibility of vertical transmission among horses.

Study Objectives and Methodology

• The main purpose of this study was to determine the prevalence of EcPV-2 in asymptomatic (without signs of disease) horses in Western Canada. To accomplish this, researchers examined two groups: a herd of healthy horses and a group of horses known to have been exposed to EcPV-2.
• Another aim was to identify the specific tissues where the virus could be found within these horses. The researchers used polymerase chain reaction (PCR), a common laboratory technique used to make copies of a segment of DNA, and RNA in situ hybridization (R-ISH), which is a method to visualize specific genes or mRNA in tissue samples.
• These techniques were implemented on several tissue samples collected from 70 horses during necropsy (animal autopsy). These horses displayed no history or evidence of neoplasia (abnormal growth of cells) or diseases associated with papillomavirus.

Key Findings

• The study found that 29% of the necropsied horses were infected with EcPV-2, indicating that asymptomatic infection with EcPV-2 is common.
• The seropositivity rate, or the rate of individuals producing antibodies in response to the virus, amongst the healthy (without visible disease) horses was 36%, confirming the exposure of horses to EcPV-2 in the region.
• The R-ISH identified EcPV-2 infected tissues and found highest frequency in the penis, followed by the vulva, eyelid, and oral mucosa. In younger horses, EcPV-2 was found in fetuses, signaling the likely vertical (mother-to-offspring) transmission of the virus.
• The researchers suggest the increased prevalence found in this study compared to previous ones could be due to the use of biopsies, which go deeper into tissues, rather than superficial swabs.

Implications of the Study

• Overall, the findings suggest asymptomatic EcPV-2 infection in horses is more common than previously believed, which could have implications for management and treatment strategies.
• Moreover, the discovery of potential vertical transmission suggests a more complex role of the virus in equine genital SCCs than initially expected. This presents a heightened importance of studying this aspect in future research.