Isolation and characteristics of an equine reovirus type 3 and an antibody prevalence survey to reoviruses in horses located in New York State.

The study deals with the isolation and characterization of a specific type of virus known as Reovirus type 3 from a sick foal, as well as conducting a survey about reovirus prevalence in horses based in New York state.

Introduction and Initial Observations

• The researchers started by identifying that reoviruses have been previously isolated from various species, including humans, cattle, cats, dogs, and horses. They also noted that these viruses generally cause mild or unnoticeable diseases in most species.
• A strain called the Ralph strain was isolated from a foal suffering from diarrhea.

Research Method and Observations

• The Ralph strain was grown in two types of cell lines designated as MA-104 and A-72. It produced cytoplasmic inclusion bodies in these cells, indicating typical signs of viral infection.
• When the virus was tested in the presence of reovirus antibodies, it fixed complement (a process that helps to clear pathogens from an organism). However, it didn’t show the same reaction when tested with rotavirus antiserum, indicating that this strain has specific immune responses.
• The size of the viral particle was observed under an electron microscope as +/- 65nm.
• The Ralph strain exhibited a feature known as hemagglutination – it clumped together pig red blood cells (erythrocytes). However, this phenomenon was not observed with human, calf, cow, chicken, or guinea pig erythrocytes.
• During a hemagglutination test, complete reciprocal crossing (a measure of compatibility) was seen with the Ralph strain and the NIH reovirus type 3, but not with NIH reovirus types 1 and 2. This suggests that the Ralph strain shares certain antigenic properties with NIH reovirus type 3.

Prevalence Survey

• The researchers conducted a limited serological survey by collecting serum samples from horses in New York State in the years 1976-1977 and in 1981.
• The samples were tested using the hemagglutination-inhibition test to check for the presence of antibodies against reovirus types 1, 2, and 3.
• The percentages of samples which had antibodies to reovirus types 1, 2, and 3, in the years 1976-1977 were 24.5, 42.2, and 3.9% respectively. However, these percentages fell to 8.8, 9.8, and 3.9% in 1981, indicating a decrease in exposure or immune response to reoviruses amongst the tested horse population over time.