Immunological studies on equine phycomycosis.

The research article discusses the development and application of immunological tests to investigate the infection by Hyphomyces destruens, commonly known as phycomycosis, in horses. The tests were used to differentiate between infected, recovered and healthy horses that had come in contact with the infection.

Test Development and Application

• The study developed one in vivo test (inside a living organism) and two in vitro tests (outside a living organism) to study the immunological response of horses to phycomycosis.
• These tests included an agar-gel double diffusion test, a complement fixation test, and an intradermal hypersensitivity test, which is known as a Heaf test.

Agar-Gel Double Diffusion Test

• This test checks for agglutination or clumping of cells in response to the fungal pathogen.
• The result was positive for all infected horses. This means the test detected phycomycosis infection in these horses.
• In contrast, serum samples taken from normal horses and those who had recovered from the infection did not react to the test, indicating they did not have the infection.

Complement Fixation Test

• This test identifies the presence of the antibody against Hyphomyces destruens in horse serum.
• About 82% of clinically infected horses had a detectable amount of the antibody with an average level of 20.
• However, antibodies were sporadically detected in serum taken from horses that had recovered or were in contact with the disease but were not clinically ill.

Intradermal Hypersensitivity Test

• This test, also referred to as the Heaf test, checks for evidence of cellular immune response to H. destruens.
• Positive responses were observed in 64% of clinically infected horses, all recovered animals, and 31% of normal in-contact horses.
• Negative reactions in the clinically infected group were thought to be either due to anergy (lack of immune response) in chronic cases or lack of simulation in very acute cases.

Conclusion

• The study concludes that many horses display evidence of past contact with H. destruens and have achieved resistance to the infection.
• This finding provides a basis for further investigation of immunity against phycomycosis in horses and aids in the understanding of the disease’s immunopathology.