No surveys are published about the relative frequencies of the causes of infertility.
It might be predicted that infectious causes are commoner in crowded colonies, that management causes might be commoner in inexperienced breeders colonies and it seems that endometritis is the commonest overall cause.
Normal physiology: age of puberty varies according to the time of year and the breed (Siamese-type Siamese have early puberty and Persians Persian longhair late puberty). There is marked normal individual variation, cats are normally seasonally polyestrus but there is individual variation in this and it is controlled by day length so it can be artificially manipulated. Some queens may be showing few external signs of estrus (more likely in the less vocal breeds). The breeder may not be recognizing estrus due to inexperience. A neutered male housed with the queen may be mating or otherwise stimulating ovulation in the queen which can inhibit estrus behavior.
Stress: a subservient queen may be inhibited in showing estrus signs. A queen that is frightened either due to the traveling, the unfamiliar housing or by the male may not mate, estrus behavior may be temporarily or permanently inhibited.
Failure of ovulation might occur if copulation is not performed adequately or frequently enough at the correct time. Male causes of infertility are important here.
Failure of fertilization: Male causes are important.
Nutrition is unlikely to be a cause of infertility unless an unbalanced diet is being fed. Taurine Taurine deficiency can cause infertility.
Endocrine causes: ovarian and paraovarian cysts are common and usually insignificant. Progesterone deficiency, probably due to early regression of the corpora lutea has been proposed as a cause of infertility but has not been scientifically documented.
ToxoplasmosisToxoplasmosis seems to not cause infertility in cats but can cause abortion.
Opportunist infection: infections by opportunist bacteria in the uterus may occur infrequently eg Streptococci Streptococcus spp Staphylococci Streptococcus spp, colibacteria.
Non-specific infection: any infectious disease, especially if it causes systemic signs such as pyrexia or anorexia can cause infertility by inhibiting estrus, early embryonic death or resorption/abortion. Other serious diseases such as inflammatory diseases, neoplasia or trauma will also cause these problems.
Chronic endometritis may cause failure of implantation, early embryonic death, resorption/abortion or the birth of dead kittens.
Fetal abnormality: this has not been proven to occur. Some breeders think that certain matings are unsuccessful because the stud and queen are incompatible due to fetal genetic abnormalities. This is unproven.
For evidence of infertility look for failure of estrus, failure to accept the mate, failure to become pregnant or to maintain pregnancy (negative pregnancy tests or recurrent calling), abortion or the production of stillborn kittens.
Look for predispositions. Check whether the owner is reporting seeing estrous behavior and definite mating with a proven male. If so is there evidence that pregnancy is occurring (production of small litters or stillbirths or positive pregnancy diagnoses). Have there been any other signs of disease, anorexia (infections, systemic illnesses), conjunctivitis with Chlamydia, vulval discharge (endometritis)? This may be detected by the owner noticing the cat overgrooming.
Check the diet.
Pregnancy diagnosis by palpation or ultrasound when appropriate.
General examination looking for any signs of illness.
Look for a vaginal discharge (as well as seeing the discharge directly you may see messy fur on the tail).
Confirmation of diagnosis
Discriminatory diagnostic features
Routine hematology, biochemistry and urinalysis are useful for background and to help rule out infections and systemic diseases. Hematology is very useful for diagnosing feline panleukopenia rapidly.
Measuring serum progesterone levels 72 hours after mating will confirm adequate copulation and induction of ovulation.
Opportunist infections may be diagnosed by histopathological and micrological examinations of aborted material.
Trial mating and assessing the outcome carefully may be useful. Just having an early pregnancy test may allow differentiation between failure of fertilization/early embryonic death and resorption. To differentiate between failure of fertilization and early embryonic death require collection of eggs 3-5 days after mating, via laparotomy, and microscopic examination of the eggs to check for successful fertilization.
Progesterone deficiency is diagnosed by serial progesterone levels being recorded prior to during and after the period when the fetuses are seen to be lost by pregnancy detection. Cautious interpretation must be performed, as progesterone levels may be reduced secondarily as a consequence of disease in the uterus.
Chronic endometritis can be evaluated by ultrasound, but can only be diagnosed by biopsy. Bacterial culture from the biopsy material is probably worthwhile. Bacterial cultures from the vagina are not helpful.
Definitive diagnostic features
A combination of history and clinical signs. Some diagnosis, eg feline leukemia virus or Chlamydia may be made quite easily. If a vaginal discharge is found, other than just after abortion, then a presumptive diagnosis of chronic endometritis should be pursued.
Initial symptomatic treatment
Management issues and diets need to be corrected by education and trial management changes, eg changing group sizes, separating neutered males.
Nervous queens can be given sedatives and anxiolytics for traveling and mating but is must be debated whether these behavior characteristics, which may have some genetic component to them, should be deliberately perpetuated.
Failure to show estrus Failure to show estrus behavior may be altered by keeping the queen in a smaller group however, sometimes the presence of other cycling females can start the problem queen cycling too.
If the cat is having estrus but it is not being detected she may be able to be housed for longer periods with an experienced stud. The stud will be able to detect receptiveness and mating should occur. If estrus was not occurring then the presence of the stud might stimulate it.
Drug treatment to induce estrus may be tried Failure to show estrus. The diagnosis of a healthy queen should be secure before trying this treatment.
Failure to ovulate despite an otherwise successful mating is a difficult problem to recognize. Ovulation can be stimulated by giving 200-500 iu of human chorionic gonadotrophin IVor IM or at half the dose both IV and IM; preferably it is given within an hour of mating.
Some diseases may be self-limiting or the reproductive aspect will resolve once the underlying disease is controlled.
Feline leukemia virus, feline immunodeficiency virus and feline infectious peritonitis are all untreatable and affected cats should be isolated and not used for breeding.
Chlamydia should be treated with suitable antibiotics. Doxycycline Doxycycline (5 mg/kg q24h) for about six weeks is recommended. All in-contact cats should be treated. Any cats with conjunctivitis should be treated for at least two weeks after clinical signs have disappeared. Azithromycin Azithromycin at 5-10 mg/kg every 2-7 days is a recently recommended treatment for Chlamydophilia. It might be effective in much shorted courses than doxycycline.
Opportunist organisms may be treated as appropriate if actually diagnosed.
Chronic endometritis/pyometra Pyometra often does not respond to treatment. Severely affected cases, should be spayed. If treatment is desired in a valuable breeding queen, it can be achieved using a prostaglandin- Lutalyse 0.01-0.02 mg/kg q 8-24 h to effect (monitor by ultrasound, serial progesterone levels and hematology). This may cause significant physical side effects and the cats are often hospitalized for the treatment. Vocalization, restlessness, panting, salivation, vomiting and diarrhea are often seen. Antibiotics should be based on culture results, coliforms are most commonly associated with pyometra in the queen.
Progesterone deficiency could be treated by a progesterone implant, placed in early pregnancy and removed five days before the intended parturition date, or supplementation. Side effects include failure to queen (prolonged gestation), failure to lactate, and anomalies of female fetuses. This should not be undertaken without a firm diagnosis.
Feed the cats on commercial cat food.
Know about normal cat breeding and their reproductive cycle.
Test all in contact-cats for feline leukemia virus and feline immunodeficiency virus. Remove any positive cats.
Vaccinate against feline panleukopenia, feline upper respiratory tract viruses and Chlamydia.
Try to control exposure to coronavirus.
Keep the cats in groups that reduce their stress levels. Do not over-populate.
Maintain general health.
Choose stud cats that are maintained to similar standards. Avoid long travel periods to the stud and think about whether the queen is going to be happy in the accommodation provided.
Guarded; as a positive outcome often requires a detailed investigations which many owners will not fund or will not think worthwhile.
No authors named (1993) Fertility and infertility in dogs, cats and other carnivores. Proceedings of the 2nd International symposium on canine and feline reproduction. Liege, Belgium, August 1992.J Reprod Fertil Suppl 47, 1-564 PubMed.
Stein B S (1991) Reproductive dysfunction in the feline.Tijdschr Diergeneeskd 116 (Suppl 1), 96S-102S PubMed.
Wolf A M (1989) Feline reproduction.Tijdschr Diergeneeskd 114 (Suppl 1), 11S-15S PubMed.
Sturman J A, Gargano A D, Messing J M et al (1986) Feline maternal taurine deficiency: effect on mother and offspring. J Nutr 116 (4),655-67 PubMed.
Henderson R T (1984) Prostaglandin therapeutics in the bitch and queen.Aust Vet J 61 (10),317-9 PubMed.
Other sources of information
Chandler E A, Gaskell C J & Gaskell R M (1994) Feline Medicine and Therapeutics. 2nd edn. Oxford: Blackwell Scientific Publications, pp272-273, 445-565. ISBN 0 632 03361 4.
Christiansen I J (1984) Reproduction in the Dog and Cat. London: Bailliere Tindall, pp243-245. ISBN 0 7020 0918 0.