Equine Disease Quarterly | EQUINE
limit inbreeding.
CONTACT:
Ernest Bailey
[email protected]
Ted Kalbfleisch
[email protected]
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, Kentucky
Jessica Petersen
[email protected]
University of Nebraska-Lincoln
Lincoln, Nebraska
Besnoitiosis in Donkeys
Figure 01. Besnoitiosis eye
Besnoitiosis is a protozoan infection caused by Besnoitia
spp., which are cyst-forming coccidian parasites that
affect multiple host species worldwide. Besnoitia
bennetti is the species known to infect equids and
has been reported in horses and donkeys in Africa,
Asia, and more recently, the United States and Europe.
Equine besnoitiosis was first reported in 1927 in four
horses from Sudan. The only reported cases of equine
besnoitiosis in North America have been in donkeys.
The life cycle of Besnoitia species involves both a
definitive (predator) and intermediate (prey) host.
Although a feline definitive host has been identified
for Besnoitia species known to infect several types of
wildlife, attempts to demonstrate a cat as the definitive
host of B. bennetti have been unsuccessful, thus
precluding researchers from elucidating the parasite’s
life cycle and mode of disease transmission in donkeys.
Clinical disease is characterized by a miliary dermatitis
caused by pinpoint parasitic cysts in the skin, mucous
membranes, and conjunctiva. The skin over the muzzle,
nostrils, ears, perineum, and medial thigh appears to be
preferentially affected. One of the most unique features
of besnoitiosis is the development of “scleral pearls,”
which are cysts on the sclera of the eye (Figure 1). Cysts
have also been infrequently identified in the testicles,
nasopharynx, larynx, trachea, and esophagus of infected
donkeys. Infected donkeys may also have generalized
crusting dermatitis, poor hair coat, and/or focal areas
of alopecia. Often affected donkeys have a history of
chronic dermatitis non-responsive to treatment with
antibiotics, ointments, medicated baths, etc.
In an epidemiologic investigation of besnoitiosis in
donkey herds across the United States, young animals
(average age 2 years) were at increased risk of infection
when compared to older individuals. Sex and breed
were not associated with developing besnoitiosis. The
most common lesions in infected donkeys were cysts
in the nostrils (94%), perineum (69%) and sclera (81%).
Some infected animals remain seemingly otherwise
healthy, while others become cachexic and debilitated
as a result of the disease. The reason for this difference
in host response to infection is unknown, but similar
clinical subtypes are observed with bovine besnoitiosis
in European cattle herds.
• Volume 22 Issue 01 | March 2020 •
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