Conditions that cause spontaneous abortion

Spontaneous abortion may occur early or late into the pregnancy of a bitch. When spontaneous abortion occurs during the first or second trimester of the pregnancy, the fetuses will be resorbed. If prior confirmation of pregnancy has not been obtained, the owner may suspect failed breeding or infertility in the bitch. As such, diagnosis of the cause leading to early spontaneous abortions is often challenging.

Spontaneous abortions in the third trimester will result in expulsion of the fetuses and, therefore, greatly narrow the field for possible causes. Aborted fetuses and placenta should be collected and refrigerated (not frozen). Necropsy of the fetuses is often helpful for identifying conditions responsible for spontaneous abortion, however, results may not always provide a definitive explanation. Causes for spontaneous abortions may be either infectious or non-infectious conditions. The most common causes are discussed here.



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<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Brucellosis.</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif] Bacteria of the Brucella sp. are well known for inducing spontaneous abortion in the bitch. B. canis is the most common of the brucellosis-causing bacterial strains found in dogs and, as such, is routinely screened for by serological testing as part of the breeding management plan. Limitations to serological testing for B. canis, however, do exist and typically occur with use of the rapid slide agglutination test (RSAT) or the tube agglutination test which may result in false-positives or false-negatives. False-positives should be suspected if a dog is asymptomatic or concurrent blood cultures drawn at the same time as serological samples are negative for bacterial growth. Follow-up assessment with the agar-gel immunodiffusion (AGID) test will rule-out the possibility of false-positive results.[/font]

[font=Garamond, Times, Serif]False-negatives will occur if serological testing is conducted within a 4 week period after the dog has initially contracted B.canis. Therefore, all negative tests should be confirmed by repeat testing 30 days from the first test before considering a dog to be free of infection. [/font]

[font=Garamond, Times, Serif]B. canis infections in pregnant bitches will typically cause spontaneous abortions between 49 and 59 days after breeding, however, infections may also induce early spontaneous abortions with resorption of the fetuses, result in stillborn puppies, or cause death of puppies shortly after birth. A bitch that aborts a litter due to B. canis will demonstrate a brown or greenish-gray discharge that contains a large number of bacteria that will be infectious to both dogs and humans. Extreme caution, therefore, should be used when caring for a bitch suspected of harboring B.canis. At such point, collection of the vaginal discharge and specific culture testing for B.canis is usually sufficient to obtain the diagnosis. [/font]

[font=Garamond, Times, Serif]Though B. canis is most often conceived as being transmitted from dog to dog during the actual act of copulation, the primary mode of transmission actually occurs via oronasal contact with infected body fluids. Therefore, spread of infection is not limited to breeding contact and as such, once introduced into a breeding kennel, the highly infectious B. canis will quickly spread through the population. Long-term, multiple treatments with antibiotics may assist in controlling symptoms and extent of infection within an individual dog, however, antibiotic treatment has limited efficacy for cure and the dog will remain potentially infectious to other dogs. As such, infected dogs should be neutered and removed from the breeding kennel environment to prevent spread to other breeding dogs. Retesting should be performed 6 months following completion of the antibiotic regimen to assess treatment efficacy. The alternative for controlling spread of B. canis is euthanasia of all confirmed-infected dogs. [/font]

[font=Garamond, Times, Serif]Dogs may also become infected with other strains of Brucella sp. that typically infect livestock. Dogs with a history of spontaneous abortion, negative serological testing for B. canis, and exposure to livestock may harbor one of the other strains such as B. abortus, B. suis, and B. melitensis. Since serological tests for B. canis will not cross react with these other Brucella sp., dogs suspected of carrying an alternate strain of Brucella should be tested specifically for these other strains.[/font]

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Canine Herpesvirus Infection.</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif] Canine herpesvirus infection occurs as a relatively mild viral infection in the average dog, however, new infection in a pregnant bitch or newborn puppies will usually result in spontaneous abortion or neonatal fatality. Greatest risk occurs in the last three weeks of pregnancy and the first 3 weeks of birth. The virus is commonly found in dogs, and as many as 80% to 100% of dogs with a history of high exposure to other dogs (such as show dogs and kennel dogs) will be found to have life-long, latent states of infection (asymptomatic infection). Bitches that become infected with herpesvirus during pregnancy will usually experience pregnancy complications resulting in fetal death, fetal mummification, spontaneous abortion, or premature birth. Newborns that become infected with the virus usually succumb to septicemia. Additionally, surviving puppies will typically show indications of permanent nerve, kidney and lymphatic system damage. Bitches previously infected with canine herpesvirus may have normal pregnancies and litters without fatality, but at other times have a spontaneous abortion or lose puppies following birth. Outcome in bitches harboring infection prior to breeding appears to rely on the maternal immune system status at the particular point in time.[/font]

[font=Garamond, Times, Serif]Serological testing showing any degree of titer for canine herpesvirus infection is considered positive since humoral immunity to this virus is minimal and short-lived. Monitoring titer, however, may provide an indication of viral "flare-up" at a particular point in time and may be helpful for assessing immune status and potential pregnancy complications in those bitches that have previously lost litters to canine herpesvirus complications. Additionally, serological titer is useful for diagnosis of canine herpesvirus as a cause for spontaneous abortion in the pregnant bitch. When abortion occurs late in the pregnancy, histopathological examination of tissues from the aborted fetuses can be used to confirm the presence of canine herpesvirus infection. [/font]
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Treatment for canine herpesvirus, as with most viruses, is extremely limited and there is currently no preventative vaccine available. Recommendations for reducing risk of new infection in pregnant bitches is to isolate the bitch from other dogs particularly during the last 3 weeks of pregnancy and to isolate newborn puppies for their first 3 weeks of life. (Canine Herpesvirus in newborn puppies is often fatal, however, some treatment success has been reported for the following treatment protocols:

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Toxoplasmosis.</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif] The cat is the definitive host for the toxoplasmosis organism, however, dogs may serve as an intermediate host. As in humans, toxoplasmosis infection in the dog may produce spontaneous abortion, but more commonly causes developmental problems that will impact upon the puppies in life. [/font]

[font=Garamond, Times, Serif]Dogs may become infected with toxoplasmosis by ingesting the organism when eating the feces of an infected cat, by eating infected meat, or in utero if the dam is acutely infected during the pregnancy (chronic infections in the dam are usually not transmitted to the fetuses). In the latter instance, if an infected litter survives, the puppies will usually develop symptoms of neurological, respiratory and gastrointestinal abnormalities.[/font]

[font=Garamond, Times, Serif]Diagnosis of toxoplasmosis is accomplished by serological titers sampled 2 weeks apart. A significant increase in the second titer compared to the first titer is indicative of an acute toxoplasmosis infection. Chronic infections may present a high baseline titer (initial titer).[/font]

[font=Garamond, Times, Serif]Prevention is the recommendation for reducing risk of toxoplasmosis infection in the pregnant bitch. Bitches should not be exposed to cat feces or raw meat, both of which may pose palatable temptations to the bitch. Since cats only shed toxoplasmosis during a brief time after exposure, chronically infected cats are not of particular concern.[/font]

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Mycoplasma and Ureaplasma</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif]. These organisms are of the Mycoplasmataceae family and normally inhabit the canine urogenital and nasopharyngeal tracts. If, however, there is an increase in the number of these organisms in comparison to the other common organisms also inhabiting the vaginal tract of the bitch, then there is an increase in infertility, spontaneous abortion resulting in resorption or premature birth, stillbirth, weak puppies, or neonatal death. Bitches kept in large, overcrowded breeding kennels are at greatest risk for acquiring these infections. [/font]

[font=Garamond, Times, Serif]Diagnosis of spontaneous abortion caused by Mycoplasma or Ureaplasma is obtained by vaginal cultures and cytological examination of the vaginal discharge for signs of inflammatory cells. Cultures may also be obtained from aborted fetuses for confirmatory results.[/font]

[font=Garamond, Times, Serif]Administration of chloramphenicol or tetracyline is effective for Mycoplasma or Ureaplasma infections. These antibiotics, however, are not safe for pregnant bitches. Therefore, if a bitch is diagnosed with an infection during pregnancy, before complications occur, Erythromycin, which is less effective against the infection but safer to the developing fetuses is the recommended treatment.[/font]

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Miscellaneous Bacterial Infections</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif]. The vaginal tract of the bitch houses a multitude of various organisms, anyone of which may become opportunistic pathogens under certain conditions. Some of these bacterial organisms that have been associated with spontaneous abortions or post-delivery complications most commonly include Escherichia coli and Streptococcus, or less commonly Salmonella or Campylobacter (particularly if diarrhea has been observed in the bitch or any humans in contact with her). Infections can occur in any bitch, however, endometrial hyperplasia that occurs with aging places older bitches at increased risk for these infections. [/font]

[font=Garamond, Times, Serif]Bacterial infections of the uterus and urogenital tract during pregnancy usually present with clouded, sometimes green-tinged discharge and if left untreated often results in spontaneous abortion. When puppies survive they usually have neonatal conjunctivitis (infection of the eyes) and often die shortly after birth due to septicemia (systemic infection). [/font]

[font=Garamond, Times, Serif]Culture and examination of the vaginal discharge will indicate bacterial infection and processes of inflammation, respectively (a special culture must be run separately if Campylobacter is suspected). Additionally, the bitch may have a fever. For treatment, the antibiotic administered will be based on efficacy as determined by sensitivity screening as well as safety to the developing fetuses if the bitch is still pregnant. When spontaneous abortions occur, care must be taken to ensure that the uterus is completely evacuated in order to control infection.[/font]

 

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Miscellaneous Viral Infections</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif]. Spontaneous abortions as a result of viral infections occur infrequently in the bitch, most likely attributed to the preventative vaccination programs utilized by most breeders as well as the duration of immunity afforded by anti-viral vaccines. When spontaneous abortions do occur they are most often associated with canine distemper virus, canine adenovirus and canine herpesvirus. Commercial vaccines are available to protect against canine distemper and adenovirus and should be administered prior to the proestrus stage to prevent vaccine-associated complications during breeding and gestation[/font][font=Garamond, Times, Serif]. Currently, there are no commercial vaccines available to protect against canine herpesvirus [/font]

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<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Progesterone Insufficiency.</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif] Bitches for which pregnancy has been confirmed by ultrasound or serum relaxin diagnosis [/font][font=Garamond, Times, Serif]and subsequently experience spontaneous abortion without evidence of any of the infectious causes outlined above should be suspected of having progesterone insufficiency (insufficient luteal phase). Progesterone hormone rises just prior to ovulation and continues to increase to levels above 5 ng/ml during the pregnancy then will decrease just prior to whelping. This hormone is essential for the maintenance of the pregnancy because it is required in high levels to suppress the hypothalamus from producing gonadotropin releasing hormone (GnRH). If levels of progesterone drop below 2 ng/ml, GnRH levels will rise and stimulate the pituitary to release follicular stimulating hormone (FSH) and lutenizing hormone (LH). FSH and LH will reset the ovarian cycle causing an abrupt termination of the current cycle, thus resulting in spontaneous abortion. This premature decrease in progesterone will typically occur between 2 and 4 weeks after breeding. When the condition occurs early in gestation, prior to confirmation of pregnancy, diagnosis is often complicated because other factors associated with unsuccessful breeding must be ruled out. Bitches for which there is a strong suspicion of progesterone insufficiency or that are confirmed to be pregnant prior to spontaneous abortion with no evidence of other conditions should be monitored for serum progesterone levels by ELISA during subsequent pregnancies. In such an instance, progesterone levels are measured from the time of breeding through the weeks of gestation. If progesterone levels begin to fall, exogenous progesterone therapy can be administered to maintain the pregnancy. Progesterone therapy is discontinued at the end of the gestation period with birth occurring within 72 hours after the final injection is administered. [/font]

<A href="http://%3cfont%20face=%22garamond,%20times,%20serif%22%3e%3cfont%20size=%224%22%3e%3cfont%20color=%22/#800040"><i><b>Miscellaneous Causes</b></i></font></font></font>" target=_blank>http://<font face="Garamond, Times,...></font></font>[font=Garamond, Times, Serif]. Fetal genetic defects may result in resorption or stillbirth of effected fetuses, but generalized spontaneous abortion typically only occurs if all the fetuses are afflicted. Such defects are diagnosed by chromosome analysis of the fetal tissue.[/font]

[font=Garamond, Times, Serif]Hypothyroidism has been linked to spontaneous abortion in bitches, however, its role in the occurrence of spontaneous abortion has not been established. In general, bitches with any type of endocrine disorder are discouraged from being bred because of the hereditary nature of many of these diseases. [/font]

[font=Garamond, Times, Serif]Though nutritional deficiencies, particularly manganese deficiency, may lead to fetal demise, the widespread availability of nutritionally-balanced, commercial dog foods has made this a rare cause for spontaneous abortion. In regard to diet, however, the practice of calcium supplementation still has implications for producing pregnancy complications, such as uterine inertia and prolonged gestation, that may increase risk to both the fetuses and the dam. [/font]

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