from a veterinarian’s perspective
an in-depth look with dr. ingrid pyka
Body abnormalities that are present at birth are called birth defects. such abnormalities may involve any organ system or any part of the body.
Reading: Birth defects in dogs
Some may be minor and resolve with growth, while others may prevent normal development and function or even cause premature death.
Although certain defects may be quite obvious at birth, many can remain hidden for months, years, and some even for life.
Birth defects can occur for no known reason, they can be inherited, they can be caused by environmental factors, or they can be a combination of any of these.
Defects can occur at any time during the developmental stages of the embryo or fetus. the occurrence or severity of the defect may depend on the stage of development when an insult occurs. the earlier in pregnancy an insult occurs, the more risk there is to the embryo or fetus.
Abnormalities in the early stages of the embryo usually lead to embryonic or fetal death. During the first month of pregnancy in a female dog or cat, the fetus develops most of its organ systems. abnormalities that occur within this period can cause serious functional defects.
The latter part of pregnancy focuses on the growth and maturation of the existing fetal body and its organs. defects during this phase may be less severe. however, some systems still undergo significant development during the second half of pregnancy, including the oral palate, cerebellum (the part of the brain that coordinates movement), urinary, and genital systems. abnormalities here can still produce serious complications.
causes of birth defects in pets
The cause of many birth defects is unknown. environmental circumstances during pregnancy can lead to a predisposition to certain defects. Abnormalities in maternal metabolism, trauma, or extreme temperatures can cause problems in fetal development. Examples of general birth defects include cleft palate, polydactylism (extra toes), pectus excavatum (intrusion of the breastbone into the chest cavity), dwarfism, extra vertebrae, and hydrocephalus.
Exposure to specific infections, chemicals, or medications (known as teratogens) during pregnancy will also increase the risks of specific birth defects. A drug called griseofulvin, which is often used to treat ringworm, is an example of a drug with known teratogenic effects causing cleft palate in the fetus. Similarly, viral panleukopenia infection of the pregnant cat can lead to cerebellar hypoplasia of the kittens, which can lead to brain damage with severe incoordination.
Some birth defects are specific to certain breeds and are the result of exaggerated traits that characterize the breed. Brachycephalic syndrome is most commonly seen in bulldogs or other short-nosed dog breeds, and results in abnormal development of different parts of their airways. animals with these defects can have breathing difficulties that lead to airway obstruction. Another example is entropion, which is the rolling of the eyelids, commonly seen in the Shar Pei.
many animals with birth defects can still maintain a high quality of life. treatment options for abnormalities vary as for any health problem.
Many congenital anomalies are believed to be inherited, although the exact mode of inheritance is often unknown. examples include portosystemic shunts in Yorkshire terriers, dilated cardiomyopathy in Dobermans, and kidney disease in wheaten terriers. Ragdoll cats are known to have an increased tendency to eyelid defects (colobomas) at birth.
Some birth defects have been shown to run in families in certain breeds and are passed down through the genes of the parents. the name of the breed is often included in the description of the disease. examples include collie eye anomaly, scotch cramp, and copper toxicosis in bedlington terriers.
detect pet birth defects
Most external anatomic abnormalities are recognizable at or shortly after birth. cleft palate, umbilical hernias, or limb deformities may be readily visible. Subtle abnormalities, such as heart murmurs caused by poorly developed heart valves, may require veterinary evaluation for diagnosis.
Some defects, such as cryptorchidism (the inability of both testicles to descend into the scrotum) or dental problems, may take several weeks or months to become apparent. however, a number of birth defects may not be detected until the animal is very large. in such cases, it is possible that only abnormalities in routine screening tests raise early concerns.
Other times, it’s not until suspicious medical problems develop that a diagnostic search is triggered. a “healthy” maturing puppy or kitten, for example, may have a congenital portosystemic shunt in the liver. it will not be until mental confusion, disorientation, or seizures occur, or until pre-spay/neuter blood tests reveal abnormalities, that your veterinarian will perform additional relevant tests.
monitoring of birth defects
Because the cause of many birth defects is unknown, preventing them can be difficult. Having a complete physical exam of your pet by your veterinarian can help detect possible abnormalities early in life. if the abnormality can be modified or corrected, the sooner the problem is detected, the better the outcome for your pet.
Responsible breeders generally seek regular veterinary care and have a close relationship with their veterinarian. keeping breeding animals up to date on vaccinations, free of intestinal parasites and on a balanced diet are important factors in providing optimal health for parents and offspring. if medications are needed while the bitch is pregnant or lactating, the vet may choose to alter the course of treatment to increase the safety of the litter, or the vet may recommend no treatment at all. even some vaccines can be harmful to the fetus and may not be given. often the veterinarian will recommend appropriate screening and/or prophylactic treatments.
Reputable breeders strive to eliminate carriers of specific birth defects from their lineage. Registries have been established to list breeder animals tested as free from specified defects. The advent of DNA testing has also allowed animals to be registered as be