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Teratozoospermia in Dogs

Teratozoospermia is a morphological (referring to form and structure) reproductive disorder characterized by the presence of spermatozoal abnormalities. That is, 40 percent or more of the sperm are abnormally shaped. The sperm may have short or curled tails, double heads, or head that are too large, too small, or badly shaped.

The effect of specific abnormalities on fertility is largely unknown, but optimal fertility is expected in dogs that have at least 80 percent morphologically normal spermatozoa. Therefore, it is known that it is nearly impossible for sperm that are abnormally shaped to fertilize an egg.

This condition can affect dogs of any age, but older dogs are more likely to have other age-related diseases or conditions that affect overall sperm quality. There is no breed predilection, however, Irish wolfhounds have been reported to have significantly lower semen quality than dogs of other breeds.

Symptoms

Spermatozoal abnormalities are sometimes classified into primary and secondary defects. Primary defects occur during spermatogenesis, the development stage, and secondary defects occur during transport and storage within the epididymis (part of the spermatic duct system). Often there are no outward symptoms of this disorder. The most obvious symptom makes itself apparent in the breeding dog, when the male dog fails to impregnate a breeding partner.

Causes

Congenital

• Dogs with fucosidosis (a metabolic disorder caused by a deficiency of the enzyme fucosidase, which breaks down the sugar fucose) have been found to have an associated abnormality in spermatogenesis (the process by which spermatogonial stem cells develop into mature sperm cells) and sperm maturation (retention of proximal droplets), with morphologically abnormal sperm and poor motility (movement); English springer spaniels have an autosomal recessive inheritance pattern, but only males have presented reproductive abnormalities as a result
• Primary ciliary (hair-like cells) dyskinesia (difficulty in performing voluntary movements) – an abnormality of the cilia which results in absent or abnormal motility of the ciliated cells; affected animals are infertile; reported in many breeds; probably autosomal recessive inheritance
• Idiopathic (cause unknown) inherent poor sperm morphology
• Testicular underdevelopment

Acquired

• Conditions disrupting normal testicular thermoregulation (temperature regulation) – trauma; hematocele (swelling due to a flow of blood); hydrocele (collection of fluid in a sac); orchitis (inflammation of the testis); epididymitis (inflammation of the epididymus, the ducts through which the sperm are conveyed); prolonged fever secondary to systemic infections; obesity (increased scrotal fat); inability to adapted to high environmental temperatures; exercise-induced heat exhaustion; seasonal (summer months)
• Infections of the reproductive tract – prostatitis; brucellosis (infectious diseases caused by the bacteria Brucella melitensis); orchitis (inflammation of the testis); epididymitis (inflammation of the epididymus, the ducts through which the sperm are conveyed)
• Drugs
• Testicular cancer
• Prolonged sexual abstinence in a non-neutered male
• Excessive sexual activity
• Testicular degeneration

Diagnosis

You will need to give your veterinarian a thorough history of your dog's health, along with any possible incidents that might have led to this condition, such as trauma, infection, or travel (as other climates, especially hot climates, may have played a role).

A history of your dog’s infertility will help your veterinarian to make a diagnosis. For example, has he been infertile after appropriately timed mating to several reproductively-proven bitches? Have spermatozoal abnormalities been found during routine breeding soundness evaluation? Your veterinarian will probably do a hormonal profile as well as an examination of the ejaculates (the sperm cells). Your doctor will also test for bacterial infections, and may use visual diagnostic tools to examine the reproductive tract. An ultrasound examination may show whether there is a blockage, orchitis (inflammation of the testis), hydrocele, hemorrhage into a cavity, cyst of the epididymus, or tumor in the testicular region that is affecting the sperm ducts and sperm morphology.