Page 585 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

560 CHAPTER 2

VetBooks.ir Differential diagnosis administration of ivermectin, which may result
in transient worsening of the scrotal oedema due to
The presence of other skin conditions such as sar-
coid, frostbite, onchocerciasis, habronemiasis or
SCC should be investigated. tissue reaction from dying microfilaria. Sarcoids
may be surgically excised if they are not extensive.
Diagnosis Prognosis
The many potential reasons for dermatitis are best The prognosis is guarded to poor, depending on the
investigated by skin biopsy. cause. Sarcoids are difficult to treat and recurrence
is common.
Management
Treatment involves removal of the inciting cause
if possible. Onchocerciasis can be treated by

POOR SPERM QUALITY

Poor sperm quality may consist of oligospermia of the epididymis for only short periods of time
(reduced sperm number in the ejaculate), necrozoo- and removed during ejaculation or masturba-
spermia (increased numbers of dead sperm), terato- tion. Senescent sperm are also removed in the tail
zoospermia (increased numbers of morphological of the epididymis by phagocytosis. Stallions prone
abnormalities of sperm) or azoospermia (absence of to spermiostasis appear to have difficulty with the
sperm in the ejaculate). normal transit and emission of sperm from the epi-
Poor sperm quality may be caused by primary tes- didymis, allowing sperm to accumulate there despite
ticular disease, causing dysfunction of spermatogen- ejaculation. The physiological reasons behind this
esis, or extragonadal conditions of the epididymis, condition are not known. Occasionally, spermatozoa
efferent ducts or accessory glands. Additional causes may accumulate in the distal ductus deferens and
include environmental conditions, medications, ill- form obstructive plugs, leading to ampullary gland
ness, fever and poor semen handling. obstruction.

SPERMIOSTASIS/PLUGGED AMPULLAE Clinical presentation
Affected stallions appear to ejaculate normally, but
Definition/overview have reduced sperm motility. An increase in mor-
Spermiostasis is abnormal sperm accumulation dur- phologically abnormal sperm indicative of stagna-
ing sexual rest within the ampullary glands, although tion of sperm is present, including a large number of
the condition may also affect the efferrent ducts and tailless heads, hairpin bent tails and distal cytoplas-
epididymides. ‘Sperm accumulator’ is a term some- mic droplets.
times used for stallions suffering this condition. The
unusually prolonged retention of sperm within the Differential diagnosis
extragonadal reserves leads to oligospermia, necro- Other conditions causing alterations to sperm mor-
zoospermia and/or teratozoospermia. Less frequently, phology such as TD.
complete azoospermia is seen.
Diagnosis
Aetiology/pathophysiology An ejaculate typical of spermiostasis contains a large
Spermatogenesis continually produces new sperm number of tailless heads when sperm morphology is
in an assembly-line fashion. Transit time through examined. Examination of the in-line filter follow-
the epididymis takes approximately 7.5–11 days. ing semen collection may demonstrate gritty casts of
In normal stallions, sperm are stored in the tail sperm clumps. Changes to the spermiogram reflect