DOG CARE

Management & Therapeutic Approaches for Unwanted Pregnancy or Misalliance or Medical Termination of Pregnancy (MTP) in Bitches

November 22, 2022

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Management & Therapeutic Approaches for Unwanted Pregnancy or Misalliance or Medical Termination of Pregnancy (MTP) in Bitches

Mismating is a common clinical problem in canine veterinary practice which may arise because dog owners are not aware of the Oestrus status of bitches. Several methods are followed by the veterinarian for termination of unwanted pregnancy in bitches in recent years. Wanke et al., 2002 reported that delay the termination approaches until confirmation of pregnancy, as over half of the animals are unwantedly being treated. Srinivas et al., 2008 reported that termination of pregnancy should be initiated after confirmation of pregnancy by trans-abdominal ultrasonography to avoid treatment of non pregnant bitches with abortifacient agents that cause severe systemic side effects. Ovariohysterectomy (OHE) would be the choice to prevent the birth of puppies following unwanted mating, but for breeding bitches, a need arises to maintain future fertility. So medical termination of pregnancy becomes imperative.

The effervescent, affectionate and friendly attitude of female than the male dogs has made them most likable to pet owners. But even though the owners have a preference for female dogs as pets, they are averse to the idea of producing pups for various reasons. Under such situation, mating of an estrus bitch with an unknown cur (male dog) is even more appalling. Accidental mating or an unplanned breeding between sexually intact dogs during a time when the bitch could be fertile (in estrus) is known as mis-mating. On the other hand termination of an established pregnancy is known as medical termination of pregnancy (MTP).

STAGE OF PREGNANCY PERIOD

Stage 1: Fertilization to implantation (days 20 to 22 from LH peak)

Stage 2: Implantation to foetal skeletal ossification (40 – 42 days).

Stage 3: Foetal skeleton ossification to parturition (42 – 65 days). Feldman and Nelson (2004) opined that canine corpora lutea are relatively unresponsive to luteolytic agent during the first 14 -28 days of pregnancy. Stage 2 is considered to be appropriate choice of stage for the veterinarians to perform medical termination of pregnancy effectively.

Mis-mating in the bitches

The chances of mis-mating in dogs increases manifold due to the promiscuous behavior of bitches, compounded by longer estrus period. Further, roaming behavior of the estrus bitch, and the tendency to accept male partner increases the chances of mis-mating to a great extent. Once this happens, request for aborting sequel of mis-mating is one of the most common requests from dog owners. Though there are several medications to nullify the mis-mating, none of them were found to be effective universally.

Indications

Universally pet owners are very keen and affectionate towards health and management of their pets. Towards this goal, once mis-mating occurs they opt for therapeutics which shall prevent the establishment of unwanted pregnancy. The purpose for opting for abolition of effects of mis-mating varies greatly. Some of them are

Prevention of unintended mating at too young or old age
Reproductive management of valuable bitches
Control of the pet overpopulation
Prevent birth of non-descript pups
Inability of the owner to bear expenses involved with rearing of pups

Therapeutics of mis-mating

Though there are several therapeutic regimens with varied success rates available to handle cases of mis-mating, some important ones are described below

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Estrogens or synthetic estrogenic compounds

Different preparations of estrogen are used for the treatment of mis-mating or misalliance detected early in bitches. Some of the compounds having estrogenic property are estradiol valerate, estradiol cypionate, estradiol benzoate, conjugated estrogen and diethyl stilbesterol ( Refer Table_1 ). Estrogen interferes the transportation time in the oviduct and tightens the utero-tubal junction, resulting in implantation failure or embryonic death. On the other hand estradiol cypionate augments the early transport of the embryo in the oviduct thereby preventing the implantation, and failure of establishment of pregnancy.

Progesterone synthesis inhibitors and Tamoxifen citrate

The drugs like Epostane which inhibits the synthesis of progesterone by blocking the enzyme β-hydroxy steroid dehydrogenase isomerase (β-HSD) are also used for the management of mis-mating in the bitches. On the other hand Tamoxifen citrate has estrogenic activity in bitches thereby interfering in zygote transport and/or implantation ( Refer Table_2)

Advice to pet owners

Since the premise of administering therapeutics is that the mis-mated bitch might conceive, many bitches may receive medication even with minimal chances of getting pregnant. The side effects of medication following mis-mating could be avoided all together by taking necessary steps to prevent mis-mating at first hand itself. The mis-mating can be prevented with proper care and management of bitches by their owners during the estrus period.

Pet owners should be advised:

To identify the females in estrus early by observing the symptoms like sero-sanguinous vulvar discharge, and increased roaming of the male dogs in the vicinity of the females in estrus.
Not to let loose their pet in estrous to prevent the occurrence of unwanted mating
To decide early about future pups. In cases of unwillingness to rear pups then elective ovariohysterectomy at the pre-pubertal age can be advised as same can effectively prevent estrus in the bitch, and consequently avoids mis-mating

Once mis-mating has occurred and the bitch is under medicament regimen, pet owner should be requested to follow below following guidelines:

Provision of adequate nutritious food and fresh water ad lib to offset side effects of medication like weakness, or debility
Follow up of hygienic measures to minimize side effects related to reproductive system

Inform the owner that it is required to ascertain that bitch was in estrus when so called mating has taken place and undertake steps for confirmation by taking vaginal smear and looking for presence of spermatozoa.

Owner may be requested to wait till the confirmation of pregnancy to avoid unnecessary cost and side effects. Following confirmation of pregnancy at 25-30 days, termination of pregnancy can be prescribed using Cabergoline and Prostaglandins combination which are much safer to use.

Medical termination of pregnancy ( MTP ) in bitches

This has been indicated that premature medical termination of pregnancy may be required as an adjunctive for the betterment of pet as well as the owner. Different medications have been used for MTP, however, prior to initiation of therapy veterinary practitioner should ascertain the pregnancy of the bitch to avoid unnecessary medications cost and side effects. This is much more important because it has been found that only 40% of the mis-mating cases lead to establishment of pregnancy whereas the 60% case remains non-pregnant. The drugs like estrogen, prostaglandins, dexamethasone, dopamine agonists, progesterone antagonists, GnRH antagonists, embryo toxic drugs and their combinations have been used depending upon the stage of pregnancy with varied level of success for the premature termination of pregnancy in bitches.

Indications

Following conditions may warrant MTP in bitches

For reproductive management of valuable bitches
Control of pet over population
Prevent birth of non-descript pups
Bitches diagnosed with dead fetus or malformed fetus
Medical emergency requiring termination of pregnancy in the bitch
To avoid the unnecessary cost related to maintenance of pregnant bitch and the future pups

Therapeutics of MTP

The medications used for the medical termination of pregnancy in bitches are

Prostaglandin and its analogues

Prostaglandins like Prostaglandins F₂α (PGF₂α) and its synthetic analogues are used commonly in the bitches for the premature induction of parturition between days 30-53 of the gestation. Natural PGF₂α is found highly effective in for termination of pregnancy in bitches after day 30 of gestation. ( Refer Table _3 )

To minimize these side effects related to natural as well as synthetic PGF₂α administration, observe the dog for 30 minutes for any side effects. Food should be given to the bitch 1-2 h after the administration of PGF₂α to avoid vomiting. To avoid the side effects associated with PGF₂α administration, atropine sulphate @ 0.04 mg/kg S/C should be given 10-15 min before the administration of PGF₂α.

Dexamethasone

Dexamethasone is also used occasionally for the premature induction of parturition in bitches at the mid gestation. It results in the production of estrogen and prostaglandins in the body by feto-placental unit. ( Refer Table_4)

Dopamine agonists

Prolactin and LH are required for luteotropic action in bitches where LH peak of estrus maintains CL function for approximately 4 weeks and prolactin becomes dominant luteotropic agent during 2^nd half of gestation. Dopamine agonists are ergot derivative alkaloid compounds that exert anti-prolactinergic effects. ( Refer Table_4)

Combination of PGF₂α and dopamine agonists

The combination of synthetic PGF₂α analogue i.e. cloprostenol and dopamine agonist like Cabergoline are found to be more effective in the premature termination of pregnancy with minimum or no side effects at all. This therapy can be started at day 28 of gestation after confirmation of the pregnancy. ( Refer Table_4)

Anti-progesterone therapy

The application of synthetic steroids which are progesterone receptor antagonists ( Refer Table_5 ) blocking the action of progesterone, for the premature termination of pregnancy in bitches has increased considerably.

GnRH antagonist

GnRH antagonist like Acycline can be used for premature termination of pregnancy in bitches. It is highly efficacious drug and causes abortion in almost all cases within 6-7 days of administration when used after mid-gestation ( Refer Table_5)

Non-hormonal compounds

Some non-hormonal compounds like L-10492 and L-10593 can also be used for the premature termination of pregnancy in bitches during first half of gestation when implantation is still under way. However, side effects associated with administration of these drugs like decreased appetite, loss of body weight, and diarrhea coupled with commercial unavailability limit their use in veterinary practice.

Supportive therapy

As discussed before, there are many side effects associated with medication for mis-mating and MTP. These side effects like decreased appetite, depression and prolonged therapy schedule leads to immunosuppression and stress on the animal, predisposing them for secondary infections. To combat such side effects, supportive and anti-stress therapy plays an important role. These supportive therapies are

Broad spectrum antibiotics to prevent occurrence of secondary infections
Antihistamines like chlorpheniramine maleate to prevent side effects and hypersensitivity related to drugs
Analgesics (pain killers) or NSAIDs should be used to prevent unnecessary pain to the animal
Multivitamins and multiminerals should be given as supportive therapy
Vitamin C as a part of anti-stress treatment with appetizers to increase the feed intake and for proper digestion
Fluid therapy to prevent dehydration and compensate anorectic period of bitch

There are many combinations of drugs available for the management of mis-mating and also for the premature termination of unwanted pregnancy in bitches. Such medications are invariably associated with several side effects. These unwanted effects of primary medication can be minimized by using a combination of drugs like prostaglandins and dopamine agonists or novel drugs like Aglepristone. A permanent solution is to get the bitch spayed. This practice will not only solve the current problem but also prevent the bitch from future pregnancies. In a nut shell, the time of gestation at which different therapy schedules should be followed and their effective periods are summarized in the Table_6

Though several medications are available to manage mis-mating, owners can be advised to further opt for MTP at a later period.

In general, pet owners should be informed about preventive measures like spaying and other management practices.

Several protocols exists for treatment of misalliance in canine species. Depending upon the time of presentation of cases, abortifacients are to be advised accordingly. Consent from the owner is necessary before attempting the treatment owing to the side effects of the drugs that are being used. Confirmation of pregnancy by using ultrasonography of fetal heartbeats and combination therapy provides very good efficacy in treating misalliance. Now a day’s veterinarians are estimating serum Relaxin of bitches between day 26 and 30 to ascertain the gestational status and appropriately initiate medical termination of pregnancy. Most of the abortifacient drugs are prescribed via signed release form is important from legal standpoint. Veterinarians advice strongly recommended for any such termination of pregnancy.

COMBINATION THERAPY

Combination treatments of dopamine agonist and PG analog reported to terminate pregnancy in pet animals (dog and cat) when administrated starting around day 25 to 28 days onwards. Action may be due to lysis of CL followed by withdrawal of prolactin support. Cabergoline at 5 mcg/kg BW daily and low dose of Cloprostenol injection @ 1 mcg/kg BW every 48 hours upto 9 days gives good results when compared to single drug. Cabergoline at 5 mcg/kg BW daily for 10 days and Cloprostenol injection @ 1 mcg/kg BW twice on days 1 and 5 of treatment. Low doses of Mifepristone and intra-vaginal applicable compounds like Prostaglandin E such as Misoprostol is currently used to terminate the pregnancy effectively.