Infertility, Associated Breeding Disorders, and Disorders Of Sexual Development

Chapter 24 INFERTILITY, ASSOCIATED BREEDING DISORDERS, AND DISORDERS OF SEXUAL DEVELOPMENT

















DEVELOPING THE PROBLEM LIST



Assessment of the Male


Before an investigation is begun into the potential causes of infertility in a bitch, the male should be assessed. The primary reason for evaluating the male before the female is that males are so much easier to study. The normal male is continuously fertile (i.e., continuously producing sperm). The female is usually fertile only 1 to 3 weeks per year. The easiest and usually most reliable method of establishing male fertility is a review of the male’s previous breeding history. Any male that has sired one or more litters in the preceding 1 to 4 months usually can be assumed to be fertile. It is also helpful to know if the male sired any litters at the time the bitch in question was in heat and bred. However, even with positive responses to these inquiries, the fertility of the male should be demonstrated with a semen analysis.


All active stud dogs should be tested for brucellosis every 6 months. Less active studs should be checked yearly and immediately prior to use. A male that has not sired a litter or that has sired litters in the past but not in the preceding 6 to 12 months must be viewed with suspicion. Whenever the male’s fertility is questionable, the owner of the bitch has three main alternatives: (1) have a semen analysis and Brucella titer performed on the male; (2) use an alternative, proven sire on the next heat; or (3) have the bitch evaluated, realizing that she may not be at fault.


A normal result on semen analysis is a major step toward ensuring that the male is not at fault. Abnormal semen or inability to obtain an ejaculate leaves suspicion directed at the male. Any normal male may have one or two abnormal semen analyses, but each abnormal study increases the likelihood of male infertility. In addition, males can have sperm that appear morphologically normal but that may not be capable of fertilization. Sophisticated studies on sperm function are not yet widely available in small animal reproduction. In any case, semen analysis is typically simple, safe, and inexpensive.



History (Anamnesis)







Physical Examination







DIGITAL EXAMINATION OF THE VESTIBULE AND VAGINA.

A digital examination of the vaginal vault should be performed routinely on any bitch examined for breeding soundness. If a culture or cytology specimen is needed, it should be obtained prior to the digital examination. Most bitches are easy to examine. A gloved, lubricated index finger should pass easily into the vaginal vault, allowing assessment of the lumen, the urethral opening, and the size and shape of the clitoris. Masses, foreign bodies, strictures, painful vaginitis, or abnormal tissue bands all prevent easy and painless examination.


If the digital examination result is abnormal but inconclusive, vaginoscopy can be performed for a more thorough evaluation. An otoscope or a vaginal speculum provides an extremely limited view of the vaginal vault and is of little value in most clinical situations. Pediatric proctoscopes are easy to use for vaginoscopy (Fig. 24-1), are relatively inexpensive, and can be used in all but the smallest of miniature breeds. An endoscope is a more expensive but smaller diameter alternative. In most breeds a small-diameter pediatric proctoscope can be used, which provides far better visualization of the area than an otoscope. If vaginoscopy is performed, the clinician must be knowledgeable about the changes in the appearance of the vaginal mucosa associated with each phase of the estrous cycle (Table 24-2).



TABLE 24-2 CHANGES SEEN IN THE VAGINAL MUCOSA DURING THE ESTROUS CYCLE
















Owner Management Practices





COMMON MISTAKES.

The following five major errors in breeding management are commonly encountered (negative results on Brucella tests are assumed).








These and similar practices do not consistently result in conception. They may work in a majority of bitches, but some normal bitches fail to conceive if bred according to such criteria.




INFERTILITY IN THE BRUCELLA-NEGATIVE BITCH THAT HAS NORMAL OVARIAN CYCLES, NORMAL INTERESTROUS INTERVALS, AND THAT ALLOWS BREEDING (Fig. 24-2



Initial Approach





BEHAVIOR OBSERVATION







OVARIAN FUNCTION IN PROESTRUS AND ESTRUS.



Plasma Progesterone.

The results of vaginal cytology can be reliable and helpful. However, to enhance evaluations, serial serum progesterone concentrations should be determined as the bitch progresses through proestrus and into estrus (see Chapter 19). Frequent serial progesterone assessments allow identification of the first day that the concentration rises above 2 ng/ml, which should coincide closely with the onset of behavioral estrus and the luteinizing hormone (LH) surge (Hegstad and Johnston, 1992). If an enzyme-linked immunosorbent assay (ELISA) in-hospital kit is used for the tests, the progesterone concentration usually is estimated as less than 1 ng/ml, greater than 1 to less than 5 ng/ml, and greater than 5 ng/ml (Manothaiudom et al, 1995). Breeding is recommended 4 days after the serum progesterone concentration is greater than 1 ng/ml as measured with these kits. Optimal breeding dates are 4 and 6 days after the rise in the serum progesterone concentration. Vaginal endoscopic evaluation of the bitch several times during proestrus and into estrus can also be informative (see Chapter 19 and 20) (Lindsay, 1990).



OVARIAN FUNCTION IN DIESTRUS: DETERMINING WHETHER OVULATION HAS OCCURRED.

The question regarding ovulation cannot be answered with testing completed during proestrus or estrus. Vaginal cytologic identification of the first diestrual day offers an indirect method of determining an approximate ovulation date, as previously described. However, a more precise determination can be made by measuring the plasma progesterone concentration daily or on alternate days. Ovulation begins 2 to 4 days after the progesterone concentration rises above 2.0 ng/ml (see Fig. 19-15). Again, these values do not confirm that ovulation took place, because progesterone is initially derived from luteinized follicles; that is, the serum progesterone concentration increases prior to actual ovulation. The initial rise does not confirm that ovulation occurs.


If the veterinarian wishes to determine whether a bitch ovulates, daily vaginal cytology smears can be used to identify day 1 of diestrus, and that information can be coupled with measurement of the plasma progesterone concentration obtained between the 10th and 20th day of diestrus. During the initial few weeks of diestrus, the plasma progesterone concentration should be greater than 3 ng/ml and usually is 10 to 50 ng/ml. Concentrations into the ranges mentioned can be attained only by progesterone secretion from functioning corpora lutea (excluding exogenous sources), which exist as a result of previous ovulation. Normal diestrual progesterone concentrations, therefore, are consistent with ovulation and proper luteal function.






SUMMARY OF MANAGEMENT PROBLEMS.

Management problems are the most common cause of apparent infertility in the bitch with a normal cycle (Johnston, 1980; Soderberg, 1989; Freshman, 1991). Veterinarians should remember to evaluate the male before embarking on the somewhat involved task of assessing the bitch. The entire question regarding proper management of an individual bitch can be answered through the relatively inexpensive approach of obtaining a thorough history, with corrections made, as needed, in past incorrect practices; behavior observation; review of vaginal cytology results; and monitoring of plasma progesterone concentrations. This approach answers the following questions: (1) how is the owner managing this bitch? (2) when does standing heat begin? (3) how long does standing heat persist? (4) what is the first day of true diestrus? (5) when is the bitch truly fertile? (6) what are her ideal breeding dates? (7) does she ovulate? (8) when does she ovulate? and (9) does she have the luteal function necessary to support pregnancy?



Brucella Infection


Brucella canis classically causes abortion late in gestation (see Chapter 26). In addition, the organism may render a bitch infertile or may cause resorption of fetuses early in gestation. B. canis infection can also result in ill or stillborn puppies (Olson et al, 1983). All bitches in active breeding programs should be repeatedly evaluated for canine brucellosis. The rapid slide agglutination test (Canine Brucellosis Diagnostic Test; Pitman-Moore, Washington Crossing, NJ) is an excellent screening test. False-negative results are unlikely, and a negative result can be trusted. Bitches that test seropositive should be retested with the tube agglutination method, because false-positive results do occur (Johnston, 1980).



Problems Arising from Infection




QUESTIONABLE VALUE OF A POSITIVE RESULT ON VAGINAL CULTURE.


Culture Technique.

Bacterial infections have been implicated as a cause of infertility in the bitch (Johnston, 1980; Lein, 1983). These infections are thought to be subclinical in the infertile bitch, only occasionally resulting in obvious vaginitis, metritis, pyometra, or systemic infection. It has been recommended that the anterior vagina of infertile bitches be cultured with a guarded swab (Accu-CulShure, from Accu-Med, Pleasantville, NY; Guarded Culture Instrument, from Kalayjian Industries, Long Beach, CA; and Tiegland Swab, HL 206400, from Haver-Lockhart Laboratories, Shawnee Mission, KS). Bacterial isolation and identification, as well as antimicrobial sensitivity, are suggested, after which the bitch can be given the appropriate antibiotics for 4 weeks (Johnston, 1980). However, it is difficult to establish the role of bacterial infections in canine infertility. Virtually all normal bitches have bacterial flora in the anterior vagina, and similar types of aerobic bacteria are present in the vaginal vaults of infertile bitches (Olson et al, 1983; Okkens et al, 1992). For these reasons, a request by stud owners that a vaginal culture be free of bacteria prior to mating is nonsensical (Watts et al, 1996; Wright and Watts, 1998).



Bacteria.

Approximately 95% to 100% of normal bitches harbor aerobic bacteria in the vaginal tract (see Table 23-2; Bjurstrom and Linde-Forsberg, 1992a). A wide variety of bacteria have been isolated from normal canine vaginal tracts, and the numbers are often increased during proestrus and estrus. Merely isolating bacteria from the vagina does not constitute the basis for a diagnosis of disease; rather, it is likely to confirm that a bitch is normal. Furthermore, the most worrisome organism, B. canis, may be difficult to isolate. A negative culture result, therefore, does not ensure that a bitch is free of an infectious disease.


The types of bacteria may vary with the age of the bitch; a higher percentage of prepubertal bitches have coagulase-positive staphylococci than do postpubertal dogs. The stage of the cycle did not alter the types of bacteria isolated in some studies, but other studies demonstrated increased numbers in proestrus and estrus (Allen and Dagnall, 1982; Baba et al, 1983). In a more recent study, the bacteria isolated did vary with the stage of the ovarian cycle (Fig. 24-3) (Bjurstrom and Linde-Forsberg, 1992a). The composition of the gram-positive and gram-negative organisms has been found to be unique to individual dogs.



Normal flora usually are recovered in mixed cultures of light to moderate growth (see Table 23-2; Bjurstrom and Linde-Forsberg, 1992a). If an organism is a significant pathogen, it usually produces clinical signs, is recovered in large numbers, and is present in a nearly pure culture because it gains advantage as a pathogen and overgrows the normal mixed flora (Allen and Dagnall, 1982; Allen, 1986; Olson et al, 1986). Of 826 vaginal swabs taken from 59 healthy, fertile bitches, cultures of only one organism were identified in 18%; mixed cultures were seen in 77%; and completely negative results occurred in only 5% (Fig. 24-4) (Bjurstrom and Linde-Forsberg, 1992a).



Some owners of stud dogs require a “negative” vaginal culture from the bitch to be used in breeding. However, most male dogs harbor microorganisms in the prepuce and urethra similar to those identified as normal vaginal flora (Bjurstrom and Linde-Forsberg, 1992b). There is no justification for refusing to breed a bitch to a stud dog because bacteria have been isolated from the vagina.


It should now be clear that it is unjustified to associate positive findings on vaginal cultures with infertility. Systemic antibiotics may have significant side effects. Heavy growth of one bacteria is more likely to be normal than abnormal. Treatment with vaginal douches for 2 to 3 weeks, with or without systemic antibiotics, may be beneficial, but such therapies should be reserved for bitches with obvious clinical signs of infection, such as a purulent vaginal discharge (Bjurstrom and Linde-Forsberg, 1992a and 1992b).


Finally, the canine uterus may contain small numbers of bacteria and still be normal (Baba et al, 1983). Obtaining a uterine culture requires laparotomy or transcervical uterine cannulation during proestrus, estrus, or diestrus. However, in normal fertile bitches these phases of the estrous cycle are associated with migration of bacteria from the vaginal vault into the uterus via the relaxed cervix (Watts and Wright, 1995). Without obvious vaginitis or pyometra, vaginal cultures are not believed to be of benefit in managing the infertile bitch.



MYCOPLASMA AND UREAPLASMA INFECTIONS.

Mycoplasma and Ureaplasma are organisms commonly cultured from the vaginal tract of normal bitches. However, a syndrome of poor conception, early embryonic death, embryonal or fetal resorption, abortion, stillborn pups, weak newborns, and neonatal death has been suggested to be caused by these smallest of free-living microorganisms. Currently, evidence regarding the pathogenesis of these disorders is circumstantial (Doig et al, 1981; Lein, 1989). As with bacterial culture results, if large numbers of these organisms are identified in pure or nearly pure growth from the vaginal vault of a breeding bitch with an infertility problem, these microorganisms may be at fault. However, in one study 59% of healthy, fertile bitches had Mycoplasma organisms recovered from vaginal swabs (Bjurstrom and Linde-Forsberg, 1992a). Management includes isolation of the animal and tetracycline or chloramphenicol therapy for 10 to 14 days (Lein, 1986).




Chronic Endometritis: Cystic Endometrial Hyperplasia







Hypoluteoidism


Plasma progesterone concentrations begin to rise prior to the onset of standing heat and decline to basal levels immediately prior to parturition. The first 6 to 7 weeks of diestrus are usually associated with progesterone concentrations of 5 to 50 ng/ml. With any bitch diagnosed as having an infertility problem, the plasma progesterone concentration should be evaluated 10 to 20 days after termination of standing heat and once or twice weekly thereafter. These studies should be completed in conjunction with evaluation by abdominal ultrasonography.


If the progesterone concentration is below 1.0 ng/ml when a bitch is timed to be in diestrus, either she never ovulated or the corpora lutea have failed to synthesize and/or secrete progesterone. Serum progesterone concentrations above 5 ng/ml should be sufficient to maintain pregnancy. If the progesterone concentration is 1.0 to 5.0 ng/ml, the amount of progesterone secreted may be insufficient to maintain pregnancy (hypoluteoidism), and abortion or fetal resorption may result. If fetuses are observed on abdominal ultrasonography early in gestation, abortion or fetal resorption should become demonstrable with repeated ultrasound examinations. (See Chapter 21 for a complete discussion of hypoluteoidism.)


To complicate matters, decreased progesterone concentrations in diestrus are not always a primary problem. Fetal factors, placentitis, or exogenous glucocorticoid therapy are a few of the many potential causes of premature luteal regression. In some situations progesterone administration may be contraindicated, but these conditions are not completely understood. Progesterone therapy should be recommended only with great caution.

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Jul 10, 2016 | Posted by in INTERNAL MEDICINE | Comments Off on Infertility, Associated Breeding Disorders, and Disorders Of Sexual Development
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