A. INFECTIOUS CAUSES
1. Brucellosis
The classic sign of brucellosis in bitches is pregnancy loss late in gestation. All
bitches should be tested for brucellosis before breeding .
2. Canine Herpesvirus
Incidence of canine herpesvirus is not well defined in the United States, but canine herpesvirus is considered a ubiquitous virus. All dogs are likely to be exposed in their lifetime. Herpesviruses do not infect individuals outside their
species; dogs cannot get human herpesvirus and vice versa.
Herpesvirus is associated with overt clinical signs only in bitches infected
for the first time in the last 3 weeks of gestation and in puppies infected within
the first 3 weeks after birth. In most adult animals first exposed to canine herpesvirus, small vesicles, or blisters, may develop on the surfaces of the external
genitalia. These resolve quickly and cause the animal no discomfort. However,
in bitches first exposed during the last 3 weeks of pregnancy, the virus infects
the placenta, causing placental inflammation and abnormal development and
death of pups. The classic litter born to an infected bitch contains some live
pups, some stillborn pups, and some mummified pups. The live pups generally
do poorly. Puppies that become infected at or after birth usually are big and
vigorous; they quickly develop inappetence and become depressed and often
die within 24 hours of first clinical signs .
This class of virus does not provoke a strong immune response in dogs.
However, a population of memory cells is created after infection that allows the
bitch to fight off infection if she is exposed again. For this reason, most bitches
lose at most one litter to canine herpesvirus.
Diagnosis of herpesvirus infection in bitches can be difficult. Because a
strong immune response is not elicited by the presence of this virus, tests that
measure antibodies against the virus may not be useful for diagnosis. If antibody titers are high, it is clear the bitch was exposed, but if antibody titers are
low, we cannot differentiate lack of exposure from lack of a strong immune response. Polymerase chain reaction (PCR) tests are available in some laboratories. These tests identify pieces of the virus in the bloodstream or on the mucosal surface of the animal under investigation and may improve ability to
diagnose this cause of pregnancy loss.
There is no treatment for bitches that lose a litter to herpesvirus.
Vaccination has been shown to improve reproductive performance in bitches
housed in kennels that have chronic problems with herpesvirus. No vaccine is
available in the United States at this time, nor is one likely to be approved soon.
Prevention is preferred; bitches should be sequestered in the last 3 weeks of
pregnancy and puppies for the first 3 weeks of life.
3. Miscellaneous
Various bacteria, including aerobic and anaerobic bacteria and mycoplasma,
have been implicated in pregnancy loss in bitches. Diagnosis requires culture of
the same organism from the bitch after pregnancy loss and from aborted pups.
The stomach content of stillborn pups is an excellent source of culture material; pups drink the amniotic fluid during gestation, so their stomach content is
a good indicator of the environment in the uterus. Pregnancy loss from bacterial infection may be due to poor hygiene in a kennel or to overwhelming presence of organisms in food, in food or water bowls, or in grooming or cleaning
instruments. Excellent kennel hygiene includes thorough cleaning and bleaching of such materials whenever possible. If a raw diet is fed, scrupulous care
must be taken to prevent bacterial growth in the food .
B. NONINFECTIOUS CAUSE: HYPOLUTEOIDISM
Progesterone must be secreted throughout pregnancy for pregnancy to be
maintained. In dogs, all progesterone is produced and secreted from the corpora lutea on the ovaries. If this luteal tissue fails, pregnancy is lost.
Measurement of progesterone once or twice weekly throughout pregnancy allows identification of premature failure of the luteal tissue. Progesterone
should not be supplemented in pregnant bitches unless premature decline in
progesterone has been demonstrated because excessive progesterone can induce birth defects in the pups. If progesterone supplementation is necessary, it
can be provided as an injection or orally
