Equine Disease Quarterly | EQUINE
larval stages of the species appear to have a relatively
low tolerance of dehydration, which may play an
important role in its ultimate distribution in the USA.
The ALT is a three-host tick with a life cycle that takes
about a year. While males and females occur in approxi-
mately equal numbers over its native habitat, very few
males have been found in the USA. Apparently, parthe-
nogenesis (female reproduction without the need of fer-
tilization by a male) is a significant feature of its biology
in the USA (Figure 2). Females can deposit about 2,000
eggs, all females, so local populations can grow rapidly
following establishment. This can result in significant
blood loss and stress to infested hosts. While the initial
introduction(s) of this tick is unknown, genetic mapping
has identified three mitochondrial DNA lineages. This
points to at least three distinct females lineages. Par-
thenogenesis would allow relatively rapid selection for
biotypes in response to environmental factors in its new
habitat.
Collections of ALT from sheep in China indicate the ears
and periocular areas are preferred attachment sites.
Specimens collected and tested in the USA have not
been shown to carry any diseases, but ALT are compe-
tent disease vectors in Asia contributing to theileriosis
and babesiosis in cattle in Australia and New Zealand
and anaplasmosis in Korea. Severe fever with thrombo-
cytopenia syndrome (SFTS) is an emerging hemorrhagic
fever in East Asia caused by SFTS virus (SFTSV), a newly
discovered phlebovirus. The Haemaphysalis longicornis
tick has been suspected to be the vector of SFTSV. Time
will tell the story of its vector potential in North America.
Preserved specimens of suspected Asian longhorned
ticks should be sent to the National Veterinary Services
Laboratories in Ames, Iowa for identification.
CONTACT:
Lee Townsend, MS, PhD
[email protected]
(859) 257-7455
Department of Entomology
University of Kentucky
Lexington, KY
Muscular Disorders of Athletic Horses
The equine muscular system is the engine room of
the horse, comprising over half of the body mass of
Thoroughbreds. At the cellular level it is a complex
system, comprised of a vast array of specialized
proteins that coordinate functions ranging from power
output to heat management. Disorders of the muscular
system cause poor performance and in some cases,
death; yet in certain groups of athletic horses, 5% to
25% of individuals have heritable muscular disorders.
Muscle disorders are very common in athletic horse
breeds because, surprisingly, they can also provide
some beneficial effects, ranging from enhanced
muscle mass to economic metabolism.
Given the importance of the muscular system to
athletic performance of the horse, not surprisingly,
it has attracted considerable research focus. In the
past two decades, “tying-up” up in athletic horses
has been teased into at least three distinct disorders,
which are heritable and therefore tend to have
strong breed predispositions. Several other heritable
muscular disorders of horses have also been defined,
causing problems ranging from profound weakness
to respiratory paralysis and early neonatal death.
Advances in medicine now permit convenient hair
or blood tests for many of these diseases due to their
genetic basis, and breeders are encouraged to display
appropriate stewardship by testing their breeding
stock for known disorders that have scientifically
validated genetic tests available. Current research
efforts are attempting to identify the genetic signature
of the disease causing tying-up in Thoroughbreds and
Standardbreds, which has proved challenging, and the
• Volume 21 Issue 1 | March 2019 •
25