FAILURE IN THE CAT
Failure to Exhibit Estrus
- Although reproductive failure is a rare complaint
of the individual cat, it is a common problem in multiple cat
households, catteries and breeding colonies.
- Due to a wide range of factors, varying from
social and environmental stress to nutritional and infectious
disease, cats can be difficult to propagate under intensive
- Reproductive failure, whether it be a problem in
an individual cat or a widespread problem of the cattery, is best
handled by initially defining where in the reproductive cycle the
Persistent or Prolonged Estrus
- Failure of a queen to exhibit estrus must first
be differentiated from inadequate estrus detection. The signs of
estrus (increased vocalization, rubbing, lordosis, and treading of
the hind legs when exposed to a male) should be reviewed with the
client to establish that estrus can be detected when it occurs.
- Ovarian activity should then be investigated in
the queen who genuinely fails to exhibit estrus. It should be
verified that general conditions necessary for ovarian activity
are met. The cat should be of at least pubertal age, sexually
intact, healthy, and exposed to adequate light. Since cats can
show pubertal estrus from 4 to 21 months of age, failure to show
pubertal estrus by 24 months is necessary to diagnose primary
- Ovarian activity can be most conveniently
detected by demonstrating the effects of circulating estrogen on
vaginal cytology. Since the follicular phase lasts about a week in
the cat, vaginal smears twice a week can detect cyclic changes in
- If the cat fails to exhibit estrus but vaginal
cytologic changes suggest normal ovarian activity, the inhibition
of behavioral estrus may be due to social or psychological
factors. Inexperienced queens or queens low in a social hierarchy
of other females may not exhibit estrus. While some queens show
distinct male preferences, others will be inhibited in unfamiliar
breeding surroundings or in the presence of people.
- To promote behavioral estrus, the queen should be
kept at home until she is obviously cycling before introducing her
to the male's territory. She should be periodically introduced to
the breeding area by herself to familiarize her with the
surroundings. If possible a gentle but experienced male should be
used for breeding. If the female cannot be induced to exhibit
estrus behavior, and the client insists on breeding, then
artificial insemination can be attempted during cytologic estrus.
- Absence of ovarian activity can be detected by an
absence of cyclic changes in vaginal cytology. To be convincing,
vaginal cytology should be performed twice a week for an extended
period of time (say three months).
- An alternative, and perhaps more convenient
approach would be to test for the presence of functioning ovaries
by pharmacologic induction of estrus.
- Normal ovarian activity may be inhibited in cases
of environmental stress, chronic disease, cystic ovarian
degeneration, pharmacologic agents, or abnormal gonadal
development. A minimum data base should be assembled including a
complete medical history and physical examination, complete blood
count, serum chemistry, urinalysis, abdominal and thoracic
radiographs, and FeLV status. T4 levels should be assessed if the
cat is underweight.
- Environmental stresses include poor nutrition,
over crowding, temperature, subclinical disease, extensive showing
- The stress of any chronic infectious, metabolic,
or neoplastic condition can disrupt normal ovarian function.
Commonly administered steroids such as progestogens and
glucocorticoids may also inhibit gonadotropin release. Failure to
exhibit pubertal estrus by 2 years indicates primary anestrus and
premature gonadal failure discussed in detail in the section on
abnormal sexual development. Diagnostic evaluation of the patient
suspected of abnormal sexual development should include
determination of karyotype, levels of plasma LH and FSH, gonadal
histology, and gross appearance of the reproductive tract at
laparotomy. While XO monosomy will cause premature gonadal failure
and primary anestrus, other cases of abnormal phenotypic or
genetic sex may be accompanied by normal cyclic activity and even
- One can attempt to induce fertile estrus in the
anestrus queen pharmacologically, or by housing the anestrus queen
with cycling queens or changing light exposure to 8 hours of
daylight for one week and then increasing to 14 hours of daylight
for several weeks.
- Persistent or prolonged estrus (greater than a
week) may be due to individual variations of cyclic activity, or
hormonally active pathologic conditions of the ovary
- Individual variations of cyclic activity in cats
include cats with persistent behavioral estrus during an
endocrinologically normal estrous cycle, cats with slightly
elevated estrogen levels during the interestrous period due to
overlapping follicular waves, and cats which show estrous behavior
during diestrus. These conditions are characterized by a cyclic
and seasonal pattern to the periods of estrus. In the first two
cases ovulation might bring the cat into diestrus and eliminate
estrous behavior. This could be attempted by repeated vaginal and
cervical stimulation during the estrous periods, or by
pharmacologic induction of ovulation as described above.
- Estrus which is non seasonally prolonged or
persistent is commonly due to cystic ovarian follicles, or rarely
due to neoplasia of the ovary.
- Cystic ovarian follicles are commonly found at
routine ovariohysterectomy, and tend to occur in older,
nulliparous queens, many of which have concurrent cystic
- Queens with cystic ovarian follicles may exhibit
signs of hyperestrogenism such as persistent estrous behavior,
nymphomania, and aggression to the point of becoming unsuitable as
- The treatment of choice is ovariohysterectomy.
- In those queens required for breeding purposes,
prognosis for fertility is low. Medical rupture of the follicles
can be attempted using 250 IU of HCG IM once daily for 2 days,
although its efficacy is controversial. Alternatively, laparotomy
and manual rupture of the cystic follicles may be attempted. On
the subsequent estrus after either treatment, the queen should be
bred to an aggressive tom to prevent recurrence of the problem.
Not all cystic structures of the ovary are follicular cysts,
- Cysts of the rete ovarii may be found at routine
ovariohysterectomy without any particular clinical signs observed
prior to surgery. The clinical and functional significance of
these cysts is not yet known. Parovarian cysts may also be
incidental findings in the mesovarium at routine
- Tumors of the feline ovaries occur rarely, and
are unlikely causes of persistent estrus in cats. However,
granulosa cell tumors are frequently accompanied by signs of
hyperestrogenism, and account for half of all feline ovarian
- A Sertoli-Leydig like tumor has been associated
with what appeared to be estrogen induced endometrial hyperplasia
in a cat.
- Estrus like behavior was reported in a Siamese
cat with a dysgerminoma, although this tumor is otherwise
considered to have minimal endocrine activity.
- Malignancy is reported in both granulosa cell
tumors and a proportion (16%) of dysgerminomas, metastasis being
to other abdominal viscera.
- Ovariohysterectomy should be considered in intact
females which show persistent, non seasonal estrus. Such females
are predisposed to cystic endometrial hyperplasia and pyometra due
to the prolonged effect of estrogen on the endometrium.
- At the time of introducing the estrous female to
the male for breeding, copulation may not occur or it may be
- Hallmarks of successful coitus in the domestic
cat are the copulatory cry and the characteristic post coital
- Failure to copulate, or failure to achieve
successful coitus may be due to behavioral or physical reasons.
- Behavioral failure of copulation may result
primarily from an inappropriate social setting.
- Breeding should take place in territory where the
male is dominant.
- Copulation may fail when a shy male is introduced
to a domineering female, or if the pair are members of the same
household where the female maintains a higher social position.
- Additionally, previous breeding experience
encourages successful coitus. An experienced male may be required
to achieve coitus in an inexperienced female and vice versa.
- Finally, the female needs to exhibit adequate
behavioral estrus. The queen in proestrus usually will not accept
the male, and sexually receptive behavior during estrus may be
suppressed due to shyness, social stress, or male preferences.
Repeated Breeding - Ovulation
- Physical incompatibility or abnormalities in both
the male and female can prevent successful coitus.
- Male problems may include dental problems which
prevent the male from establishing an adequate grip on the female,
hair rings around the penis, or penile injury or abnormality
preventing extension and intromission.
- Body size differences between male and female may
also prevent normal intromission.
- The female with stricture, aplasia, inflammation,
infection or neoplasia of the vagina or vestibule may not allow
breeding. Vaginal speculum examination can be achieved to a
limited degree under sedation using an otoscope with a sterile
cone and may allow detection of mechanical obstructions.
- High numbers of neutrophils in vaginal cytology
can indicate a vaginitis, but the possibility of purulent
endometritis or pyometra should not be ignored. Due to the
likelihood of contamination, positive vaginal cultures by
themselves do not indicate vaginitis, but must be interpreted in
conjunction with cytology and otoscopic examination to confirm
- A queen that continues to show heat every 2-3
weeks despite repeated breeding is probably failing to ovulate.
- Failure to ovulate can be diagnosed by
progesterone levels less than 2 ng/ml from day 7 post estrus to
- Ovulation can fail if coital stimulation is
inadequate, mistimed, or a primary dysfunction of the
neuroendocrine reflex exists.
- Infectious infertility is unlikely to be a cause
of repeated breeding in the cat, unlike other domestic species,
because of the cat's unique estrous cycle with its requirement for
Inadequate coital stimulation
- Inadequate coital stimulation may occur when
coitus is unsuccessful, or occurs too few times. Unsuccessful
coitus is characterized by absence of both a copulatory cry and
post coital reaction and if documented should be analyzed as a
failure to copulate. An insufficient number of mountings may also
result in a failure of the LH spike necessary for ovulation.
Ideally, the female should be left with the male until at least 3
or 4 breeding have taken place and be bred on more than one day
during estrus. Some females may ovulate after only one mount,
however, if the follicles are mature.
Neuroendocrine Reflex Problems
- Coitus that occurs too early or too late in
estrus may not result in ovulation.
- If too early, the follicles are not yet mature,
if too late the follicles may have undergone regression. Before
day 2 of estrus, breeding may fail to result in ovulation.
- Optimal response to vaginal stimulation usually
occurs on day 3 of estrus and shortly after.
- Failure of the neuroendocrine reflex is most
likely associated with the development of cystic follicles.
Possible treatment may be 250 IU HCG IM daily for 2 days, at the
time she is bred, however, success of this treatment
- Additionally, any number of neurologic,
endocrine, or developmental abnormalities could potentially lead
to a failure of the neuroendocrine reflex.
- A cat with spinal neurologic disease might be
expected to have difficulty transmitting sensory information to
- Neuroendocrine disease may prevent GnRH or LH
- Gonadal abnormality may prevent ovulation. An
apparently normal queen which showed cyclic estrous behavior, but
upon ovariohysterectomy revealed enlarged gonads with testicular
morphology, would not have been expected to undergo normal
ovulation post coitus.
Loss of an Undetected Pregnancy
- When a cat is found open at pregnancy exam a
minimum data base should be assembled to determine if the cat is
healthy, if appropriate breeding practices were followed using a
fertile male, whether the queen ovulated post breeding, and if
primary reproductive disease is present.
- Possible causes of infertility in the queen who
ovulates when bred to a fertile male are failure of sperm to reach
the egg, failure of fertilization, or undetected death of the
- The minimum data base for the queen who is non
pregnant at pregnancy exam should include history, physical, serum
progesterone, abdominal radiographs, complete blood count,
chemistry panel, urinalysis, FeLV antigen test (Elisa or IFA) and,
depending on the presence of a vaginal discharge, vaginal
cytology, culture, and vaginoscopy.
- T4 levels should be run if the cat is thin.
- The history taker should attempt to detect
abnormalities in the queen's cycling behavior that may indicate a
failure to exhibit normal estrus (frequency and duration of estrus
periods), or a failure to ovulate (success, number and timing of
copulations; repeated breeding every 2-3 weeks).
- Inquiries should be made into the general
hygiene, nutrition, and environment in the cattery.
- The male should be ruled out as a possible cause
of infertility by confirming siring of recent litters of kittens,
or results of recent semen evaluations.
Causes for Undetected
- The physical examination should include
determining presence of a vaginal discharge, abdominal palpation
to detect uterine or ovarian enlargement, and ophthalmic
examination to detect retinal degeneration due to taurine
- Routine blood work and urinalysis are performed
to detect any chronic underlying disease which may prevent normal
cycling or predispose to reproductive failure.
- A progesterone level greater than 2 ng/ml before
day 40 of gestation indicates ovulation occurred.
- A uterus visible on abdominal X ray suggests
abnormal uterine enlargement and requires further investigation
- Vaginal cytology, culture, and vaginoscopy will
help determine the nature and source (uterus or vagina) of a
- Failure of sperm to reach the egg would be due to
blockage of the cervix, uterus or oviducts. Assessing the patency
of these structures can be attempted at laparotomy by infusing
sterile saline into the uterine horn using a small gauge needle,
and milking fluid through the oviducts, both horns, or retrograde
through the cervix. Due to the risk of developing a peritonitis,
this procedure would probably be contraindicated if the uterus
appeared infected, or if free fluid was detected in the uterine
lumen prior to infusion. Since semen traverses the oviduct during
estrus, this would be the appropriate time to attempt this
- Failure of fertilization is not yet commonly
evaluated in practice. However, new technical developments in
feline oocyte collection, in vitro fertilization, and embryo
transfer show that the ability to evaluate a queen's oocytes may
soon be possible perhaps even clinically. It is currently possible
to obtain oocytes by laparoscopic aspiration of follicles for use
in vitro fertilization studies. Fertilized embryos and
unfertilized oocytes have been obtained 7 days after the first
breeding from the uterine lumen by placing a flanged tomcat
catheter in the caudal terminus of the uterine lumen, 2-3 cm
cranial to the uterine bifurcation, and flushing 25-30 ml of
culture media cranial to caudal through a 17-gauge catheter placed
near the utero tubular junction. The fluid is collected into
gridded petri dishes and searched with a stereomicroscope. If
fertilized embryos can be collected from the queen which
consistently fails to become pregnant, one can establish that the
reproductive tract is patent through its entire length, that
fertilization took place, and that infertility is likely due to
loss of the undetected pregnancy.
Abortion, Stillbirths, Mummies
- Confirmed Pregnancy Loss
- Likely causes for undetected pregnancy loss would
be cystic endometrial hyperplasia and endometritis. (Infectious
agents, nutrition, genetic defects, and hypoluteoidism might also
be responsible, but are discussed in the following section.)
- Cystic endometrial hyperplasia
and endometritis are presumptively diagnosed by detecting a
radiographically visible uterus. Definitive diagnosis would
require exploratory surgery accompanied by uterine biopsy and
culture of the uterine lumen. Cystic endometrial hyperplasia is
thought to result from prolonged exposure to estrogen in an aged,
non pregnant queen, or in one who develops cystic follicles.
Pregnancy protects the uterus from the harmful effects of estrogen
that can lead to cystic endometrial hyperplasia. The treatment of
choice for cystic endometrial hyperplasia is ovariohysterectomy.
- Endometritis can
result from cystic endometrial hyperplasia aggravated by bacterial
contamination, persistence of mummified or incompletely resorbed
fetuses, retained fetal membranes, or from postpartum metritis of
a previous pregnancy. If culture of the endometritic uterus is
successful one can institute specific antibiotic therapy. Vaginal
cultures are of value if the queen has an endometritis of
sufficient magnitude to cause a vaginal discharge, and surgical
culture is not an option. Prostaglandin therapy at a dose of 0.2
mg/kg subcutaneously once daily for two days followed by 0.5 mg/kg
for three days, in conjunction with broad spectrum antibiotics has
been successful in treating pyometra (see section titled Pyometra)
with good subsequent fertility. A similar protocol may be
appropriate in cases of presumptively or definitively diagnosed
endometritis in the cat. Prostaglandin has been used successfully
to treat endometritis in the dog. If abdominal radiography
suggests that fetal remnants are present in the uterus, surgical
removal of fetal remains may be necessary.
Systemic Infectious Agents
- When a confirmed pregnancy is lost, either by
observed abortion or failure to queen following positive pregnancy
diagnosis, a minimum data base should include clinical evaluation
of the queen and submission of fetus and placenta, if available,
for post mortem examination.
- Likely causes for loss of a detected pregnancy
include systemic viral or bacterial disease, ascending bacterial
infection, nutritional deficiency, exposure to fetotoxic or
abortogenic agents, hypoluteoidism, or lethal genetic defects.
- Clinical evaluation of the queen should include a
history to detect signs of concurrent illness, particularly upper
- Physical examination should include abdominal
palpation, and fundoscopic examination of the retina. Abdominal
radiography should be performed to detect retained fetuses,
ectopic pregnancies, or evidence of uterine rupture. CBC,
chemistry panel, urinalysis, FeLV antigen test (ELISA or IFA) and
acute serum to be paired with convalescent serum two weeks later
should be submitted If the queen is showing signs of upper
respiratory infection, ocular, nasal, and oropharyngeal swabs
should be submitted for viral, chlamydial, and mycoplasmal
isolation, and impression smears of the conjunctiva submitted for
detection of chlamydia. Chilled fetus, frozen and formalin fixed
samples of placenta should also be submitted if available. The
receiving diagnostic laboratory should be contacted for preferred
methods of collecting and transporting specimens.
- Systemic infectious agents which are considered
potential causative agents of abortion include feline leukemia
virus (FeLV), feline panleukopenia virus (FPV), feline infectious
peritonitis virus (FIP), feline herpes virus (FHV), chlamydia,
mycoplasma, ureaplasma, and toxoplasma.
- The effect of feline leukemia virus on
reproduction depends on whether the queen is viremic or not.
- In viremic queens (positive ELISA or IFA) FeLV
appears to cause pregnancy loss.
- In a report describing 10 IFA positive cats, 4
underwent unsuccessful breeding, 2 became pregnant but resorbed
the fetus, 3 aborted, and 1 developed purulent endometritis with
several degenerating fetuses.
- A pregnant cat with lymphosarcoma was also
reported to resorb fetuses at 5 weeks of gestation.
- Another author reports a pattern of fetal
resorption in FeLV infected queens, and isolation of the virus
from litters of unborn fetuses, newborn kittens, and the uterus of
viremic, pregnant queens.
- While it appears that pregnancy loss is due to
direct fetal infection, it has also been suggested that the virus
disrupts the endometrium at the sites of placental attachment.
However, further study is necessary to accurately define the
occurrence and pathogenesis of abortion in FeLV viremic queens.
- Nonviremic queens (ELISA or IFA negative), who
have overcome the initial infection but are latently infected in
the bone marrow can reproduce normally and do not appear to be at
significantly increased risk for pregnancy loss.
- However, the virus may be passed to the
occasional kitten, who may then infect his or her litter mates. In
a study of 6 latently infected queens (identified by reactivation
of the virus from bone marrow aspirates) none of the queens
experienced any reproductive problems over multiple pregnancies,
never did they revert to viremia during pregnancy or lactation.
- A single kitten of 30 kittens was viremic at two
weeks of birth and nonviremic litter mates subsequently developed
viremia at ten weeks post partum. Possible routes of infection in
the viremic kitten may have been transplacental or via milk.
Latent infection was not detected in any kittens borne to these
latently infected queens. Evidence for milk borne transmission was
presented in another study in which transmission of virus from a
supposedly latently infected queen to a suckling kitten occurred,
and the milk cultured positive for the virus. This queen was
periodically viremic however. Although direct infection of fetuses
with FeLV has been achieved in latently infected queens, the
queens were reinoculated with live virus intraperitoneally during
gestation. Consequently, this particular model of fetal infection
does not apply to the latently infected queen.
- Control of feline leukemia virus in the cattery
is achieved by removing all ELISA positive animals from the
cattery, and retesting all negative animals in 90 days. Feline
immunodeficiency virus, a virus similar to FeLV, has not yet been
associated with reproductive failure.
- Feline panleukopenia virus is a hardy parvovirus
with a predilection for mitotic tissue. It has been shown to cause
in utero infection, leading to cerebellar hypoplasia and ataxia in
kittens. The cerebellar external granule cell layer is highly
mitotic in the perinatal period and ataxia is manifested when the
infected kittens first become mobile. However, earlier in
gestation, tissues located in the kidney and gut are mitotically
active and serve as sites of viral replication. Consequently,
although neonatal ataxia indicates in utero infection late in
gestation, infection earlier in gestation can lead to abortion or
fetal resorbtion. Similar mitogenic viruses have been shown to
cause abortion and fetal resorption in rats. Although dams
infected during gestation seroconvert, they usually do not show
clinical signs. Diagnosis of fetal infection due to feline
panleukopenia virus is by isolation of virus from fetuses or
neonates submitted to necropsy, by documenting a seroconversion in
the dam, or clinically by characteristic ataxia observed in the
- Interestingly, cerebellar dysfunction can also
occur in kittens borne to queens fed taurine deficient diets.
- Vaccination of queens against panleukopenia virus
prior to breeding is recommended.
Feline infectious peritonitis virus (FIP)
- Feline infectious peritonitis virus (FIP), once
believed to be a major cause of pregnancy loss and kitten
mortality in catteries, is currently an unproven cause of
- FIP does cause fatal neonatal infection, however.
- The initial association of FIP with poor
reproductive performance came from observations of high
coronavirus titters in catteries with reproductive problems. With
the discovery of the widespread nature of feline enteric
coronavirus, which cross reacts with FIP in serological tests, and
similar reproductive problems occurring in SPF catteries free of
coronavirus, the role of FIP virus as a cause of pregnancy loss
- It is established, however, that FIP causes
disease in the neonate, and that kittens borne to infected mothers
are at particular risk. While milk borne transmission is a
possibility, transplacental transmission cannot be ruled out.
Lesions which could only have been caused in utero have been
attributed to a feline coronavirus and the possibility of dual
infection of FIP and feline panleukopenia virus has been
- Since FeLV is a major potentiator of FIP, control
of FIP is commonly achieved by elimination of FeLV viremic animals
from the cattery.
- A recently licensed vaccine for FIP is now
commercially available in the Primucell FIPTM, SmithKline Beecham
Animal Health. In clinical trials using a highly virulent
challenging strain of FIP, 100% of non vaccinated controls became
ill, 83% of which died. Among the vaccinated animals 85% survived
the challenge, and exhibited substantially reduced clinical signs
compared to the surviving non vaccinates. The vaccine is comprised
of a temperature sensitive mutant virus which grows at 31oC
but is inhibited at 37oC.
When administered intranasally the virus replicates in the
respiratory tract at the reduced temperature and provides
protective cell mediated and local immunity. Temperature
sensitivity prevents systemic spread. Because it is a modified
live preparation, its use in pregnant queens is contraindicated. A
serologic test by which FIP latently infected animals can be
removed from the cattery does not currently exist.
Feline herpes virus
- Feline herpes virus appears to cause abortion due
to the debilitating effect of upper respiratory infection in
queens, and infects kittens in the neonatal period.
- In utero transmission of the disease has not been
shown except under certain experimental conditions. In one study,
pregnant queens infected intranasally aborted following severe
upper respiratory disease. However, no virus was isolated from the
uterus, fetus or placenta, nor were any histologic lesions seen.
- When pregnant cats were infected intravenously,
pregnant queens aborted after showing minimal signs of illness,
and virus was isolated from uterus and placenta, both of which
showed histologic lesions. This intravenous inoculation of the
virus probably does not represent a true clinical picture of an
upper respiratory pathogen.
- Because approximately 80% of cats infected with
the virus become latently infected, and shed virus during periods
of stress, the neonatal kitten is susceptible to infection from
the queen who sheds virus during lactation.
- Although shedders can be detected by isolation of
the virus from cats treated with corticosteroids, control of the
disease focuses on protecting the neonatal kitten through ensuring
adequate colostral protection and vaccination as maternal antibody
wanes at 6-12 weeks.
- Chlamydia psittaci, a causative agent of upper
respiratory infection and feline pneumonitis has been implicated
as a cause of reproductive failure and in utero infection.
- Two queens from a cattery in the UK had kittens
which experienced upper respiratory infection due to chlamydia.
Both queens had experienced problems with abortions and failure to
conceive. One queen, treated with tetracycline, subsequently had
two healthy litters.
- Another report describes a condition of fatal
pneumonitis in a litter of kittens infected from birth, the
survivors afflicted with mucopurulent ocular discharge. Chlamydia
psittaci was isolated from the lung of a dead kitten. Abortions
were also reported in this cattery.
- Diagnosis of chlamydial infection is by
demonstration of organisms in conjunctival scrapings or by culture
of ocular or nasal swabs.
Mycoplasma and ureaplasma
- Mycoplasma and ureaplasma have been suggested to
be causative agents of abortion among cats. Diagnosis is also by
isolation of the organisms from ocular or nasal swabs.
- Tetracycline is the treatment of choice for
mycoplasma, ureaplasma and chlamydia and may be warranted when
outbreaks occur among non pregnant animals housed with pregnant
queens. It should not be administered to pregnant animals,
however, since it causes bone and teeth malformation in the
developing fetus. Further research is necessary to elucidate the
role of these intracellular bacteria in feline abortion and
- Protozoal infections are unlikely causes of
- Attempts to transmit Toxoplasma gondii from
pregnant queens to their fetuses have not been successful.
However, one case of neonatal infection characterized by
pneumonitis, myocarditis, encephalitis, and retinitis in a two
week old kitten is thought to have originated in utero since
encysted organisms which were found would have normally taken four
weeks to develop.
- Ascending bacterial agents which may cause
abortion include Coliform, Staphylococci, Streptococci,
Salmonella, and Mycobacteria.
- It is felt that bacteria rarely cause abortion
unless unhygienic conditions prevail in the cattery. Bacteria are
thought to migrate from the heavily contaminated vagina into the
uterus where infection leads to fetal infection and death.
- Bacterial contamination commonly occurs at
parturition but abortion is more likely to result from
contamination at breeding.
- The cat aborting due to bacterial causes may show
signs of systemic illness including fever, malaise, anorexia,
abdominal straining and vaginal discharge.
- Recommended treatment includes appropriate
supportive and antibiotic therapy continued for two to three weeks
post abortion. In addition, uterine evacuation can be attempted
using prostaglandin F2".
- Nutritional deficiency is an unlikely cause of
pregnancy loss since most cat are fed commercial, balanced diets,
and other signs would be apparent. Nevertheless, special attention
should be paid to vitamin A and taurine.
- Vitamin A has been associated with reproductive
failure such as anestrus, failure to conceive, early embryonic
death, abortion and congenital defects.
- Queens fed a taurine deficient diet can appear
clinically normal, yet suffer from reproductive failure. Of 18
queens fed a taurine deficient diet, only 6 carried pregnancy to
full term. Clinical findings included abortions, early embryonic
death and malformations in the neonates. Mothers were clinically
normal except for retinal degeneration detected by fundoscopic
examination. Interestingly, affected neonates suffered from
cerebellar dysfunction due to a persistence of mitotic activity in
the external granule cell layer of the cerebellum. While the
histopathologic lesions were thus different from those seen with
panleukopenia virus infection, the clinical signs were similarly
indicative of cerebellar dysfunction. Hindlegs were abnormally
developed, The kittens tended to be paretic in the hind legs,
which frequently splayed out.
- Hypoluteoidism, failure of the corpus luteum or
placenta to secrete sufficient progesterone to maintain pregnancy,
has not been definitively documented as a cause of pregnancy loss
in the cat, although it is suspected in those cats which
habitually abort around day 50 - 58 of pregnancy.
- The suggested treatment is to administer
injections of progesterone in oil to cats at a dose of 1-2 mg/kg
weekly beginning a week prior to the anticipated abortion date,
and to discontinue treatment a week prior to parturition.
- There is concern that administration of sex
steroids during pregnancy can lead to gonadal dysgenesis of the
fetus in utero.
- Fetal injury due to administration of fetotoxic
drugs during pregnancy should also be considered as a potential
source of fetal death.
- The specific drugs below are known to cause fetal
injury and should not be administered during pregnancy:
antibiotics (quinolones and tetracyclines), antifungals (griseofulvin),
antiinflammatories (dimethyl sulfoxide), anesthetics
(pentobarbital), gastrointestinal drugs (misoprostol),
anticonvulsants (phenytoin), steroids (testosterone and estrogen
analogues), vitamin A analogues (isotretinoin) and mitotane (o,p'-DDD).
Organophosphate insecticides, anticancer drugs, corticosteroids,
and vaccination with modified live vaccines (eg feline
panleukopenia vaccine) should be avoided in pregnant queens.
- Care should be taken to avoid excessive levels of
vitamin A during pregnancy (eg from feeding raw liver), since this
can be embryo toxic.
Abnormal Sexual Development
- Genetic defects tend to occur when close
inbreeding takes place.
- While cats may have many genetic abnormalities,
the Manx syndrome is of interest. Breeders of Manx cats find that
genetic fetal defects associated with incomplete formation of the
spinal cord and fetal death occurs in some litters. Some cats are
born with a tendency to acquire megacolon or urinary incontinence
due to incomplete innervation of the pelvic viscera. Analysis of
aborted fetuses or stillborns for genetic defects such as spina
bifida or sacral dysgenesis should be considered when one or both
parents are of Manx breeding.
- Failure of normal development of the gonads is
termed premature gonadal failure. A common clinical sign is
absence of pubertal estrus by two years of age.
- Diagnostic evaluation of the patient suspected of
abnormal gonadal development should include determination of
karyotype, levels of plasma LH, and FSH, gonadal histology, and
gross appearance of the reproductive tract at laparotomy. In the
cat, the XO chromosomal abnormality, while uncommon, causes
- Clinical signs reported include a cat smaller
than its litter mates and lack of pubertal estrus by 2.5 years of
age, but otherwise outwardly normal appearance. The reproductive
tract is apparently normal early in life but undergoes ovarian
atresia as the animal matures.
- The XO condition can be predicted in some
situations if one knows the coat color of the parents. The alleles
for orange and black are carried on the X chromosome. Females born
to a black female (homozygous for the black allele) by a ginger
tom (single orange allele on the single X chromosome) should carry
a black gene from the mother and a orange gene from the father.
Such a female kitten would be tortoiseshell (heterozygous for
orange and black). If black, however, she would probably have
failed to receive the X chromosome with its orange gene from the
father, and would carry only the X chromosome with its black gene
from the mother, making her XO. Similar reasoning is used to
predict the likelihood of Kleinfelter's syndrome (XXY) and hence
sterility in tortoiseshell toms.
- Presence of abnormal sexual development, however,
does not rule out the possibility of cyclic estrus behavior or
even normal pregnancy. At routine ovariohysterectomy of an
outwardly normal female with normal cyclic behavior, abdominal
testes have been reported in the place of ovaries. This male
pseudohermaphrodite (male because she had testes,
pseudohermaphrodite because gonads of only one sex were present)
had essentially normal external genitalia, except that the vulva
was slightly smaller than usual, and the clitoris somewhat
enlarged. Normal pregnancies have been reported in two cats with
unilateral ovarian dysgenesis, also detected at routine
ovariohysterectomy. Both cats exhibited sex chromosome mosaicism
in cultured lymphocytes, (one X/XXY, the other X/XX), and both
cats were pregnant with fetuses of normal gonadal development and
genetic sex, occupying both horns of the uterus. While each had a
small nodule in place of one ovary, the contralateral ovary was
- A condition equivalent to Kleinfelter's syndrome
(XXY) has been described in male blue cream burmese, tortoiseshell
or calico cats. Such cats can be recognized as unusual since a
normal male (XY) has only one X chromosome. Blue cream,
tortoiseshell, and calico indicate heterozygosity (two X
chromosomes) at the sexlinked locus for coat color, indicating the
XXY genotype in males or a mosaic consisting of two cell
populations with different X chromosomes. XXY males have slower
than average development of external genitalia and libido, but are
still within the normal range. No pregnancies have been reported,
however, after apparently normal matings using strictly XXY males
although mosaics and chimeras at this locus (eg XY/XXY, XX/XY)
have been reported to be fertile, as have X chromosome mosaic
contributed by Bruce
E Eilts modified 23