Neonatal Mortality

CHAPTER 11 Neonatal Mortality

Owners frequently present a dead puppy or kitten to the veterinarian, seeking the cause of death. The veterinarian should always remember that the dead neonate is the end result of a process that may have been mediated by problems with the owner, stud, dam, environment, or the neonate itself. This stark fact dictates that a systematic, methodical approach be employed in pursuing a diagnosis for puppy and kitten losses. Even then, there are many deaths whose etiology escapes discovery.

The primary chronologic benchmarks for neonatal survival generally are birth, the first 24 hours, the first week, and weaning. The neonatal mortality rate for each of these benchmarks decreases as the neonate progresses along the timeline; 75% of puppy deaths occur in the first 3 weeks of life, 50% of neonatal deaths happen in the first 3 days, and 65% in the first week. In some studies, stillbirth accounts for 50% of the losses (Table 11-1).

TABLE 11-1 Summary of 421 puppy deaths

Age Number (%)
Parturition (stillbirth) 126 (29.9)
Days 0-3 (live birth) 209 (49)
Days 4-28 71 (16.9)
Days 29-42 5 (1.2)
Days 42-45 (postweaning) 10 (2.4)

From Lawler DF: Neonatal and pediatric care of the puppy and kitten, Theriogenology 70(3):384-392, 2008.

The vast majority of these early losses are due to neonatal hypoxia, malnutrition, and hypothermia. Mortality can be caused by dystocia, physiologic abnormalities, environmental problems, genetic issues, infections, and behavior abnormalities. Some dams historically have increased rates of fading puppies and kittens.

The majority of the factors responsible for early mortality are centered on poor management and suboptimal husbandry. Certain breeds are known for increased neonatal mortality such as the brachiocephalic breeds in both dogs and cats. Some breeds are known anecdotally for early whelping with an increased number of weak puppies, for example, the Cavalier King Charles Spaniel. Likewise, the Norwich/Norfolk Terriers and the Schipperke have reputations among breeders for delayed onset of puppy deaths (fading puppies), beginning at 2 and 3 weeks of age.

The veterinarian may be presented with a dead neonate by a wide variety of owners. Sometimes, the breeder has significant financial interest in the litter and is seeking a specific diagnosis as a long-term herd health business solution. Other times, a new owner wants to know why the neonate has died; those cases in which a newly purchased pet is involved can carry an increased risk of litigation between the owner and breeder (the classic financial interest and who is paying for this scenario). Occasionally, owners let their dog/cat have one litter to show their children the miracle of life and were ill prepared for the miracle of death and desperately looking for a cause of death to answer their children’s questions. The extent that each of these owners is willing to pursue a diagnosis varies. Often, no answer is found. The local diagnostic laboratory can provide guidelines on sample preparation before submission; following guidelines can increase the probability of obtaining a specific diagnosis (see Chapter 29).

The key to enhancing the probability of finding the etiology for neonatal puppy and kitten deaths is to obtain a quality history through encompassing questions regarding the owner, stud, dam, and environment. Physical examination of a dead neonate is usually insufficient to determine the cause of death. Use of a quality diagnostic laboratory for a complete necropsy and special studies, if indicated, is usually required. A full physical examination of the mother and living siblings can be extremely informative and should be performed.

The diagnostic approach to neonatal death is dictated by several factors. The loss of a single puppy or kitten often offers a different problem set than multiple deaths in a litter. Is a single death strictly an individual problem or is it the first in a series of multiple deaths? Is the body in good condition and weight or is it emaciated? Was the dead offspring the largest, fastest-growing littermate or was it always the smallest, weakest “runt”? These and many other questions need to be answered.

Environmental Issues

Early, preweaning neonatal vulnerability is influenced most by the dam and the environment into which the neonates are born (Box 11-3).

Incorrect environmental temperatures can have devastating impacts on neonates. Puppies and kittens are unable to shiver or generate much heat by movement in the first 6 days of life. When temperatures are low, their immunity and metabolism are significantly decreased. If the neonate’s temperature is less than 94° F (34.4° C), intestinal ileus develops, shutting down the digestive process. Hyperthermic environments can stress the dam, and she may be resistant to lying close to her puppies or kittens. Additionally, hyperthermia can also lead to neonatal dehydration.

Poor whelping or nesting box design can be a major source of neonatal mortality. If the box is too large, the chances for a neonate to get separated from the mother are increased. If the box is too small, the chances of neonates being stepped on or laid on is increased. Whelping or nesting boxes without “hog rails” (Figure 11-1) increase the probability of neonates being crushed against the wall by their mother. Additionally, the whelping box should be made of materials that are easily cleaned and disinfected and do not retain moisture.

Improper placement of the whelping box can heighten the mother’s stress level, particularly if the area is loud, with lots of human and/or animal traffic. Stressful locations or environments have the potential to increase neonatal mortality. Stress elevates the anxiety of the dam, which can promote poor mothering and decrease milk let-down. Anxious mothers do not quietly lie with their offspring, instead, they are up and down and very restless, which means the young are at increased risk of being stepped on and cannot settle in for quality nursing. Poor whelping box placement can also allow drafts from open doors or windows in other locations in the building.

Improper bedding materials can allow neonates to become buried or lost and unable to find their mothers and therefore are unable to nurse, becoming both hypoglycemic and hypothermic. Poor bedding retains moisture and dissipates the heat away from the puppies, allowing increased bacterial growth. Regardless of how appropriate the bedding material is, it must be kept cleaned or changed frequently or it can contribute to higher neonatal death rates.

Proper environmental hygiene is paramount, since puppies and kittens have a variety of structural, metabolic, and immune conditions that although normal for their age, makes them more susceptible to infectious disease. Proper selection of disinfectants is important; however, care should be taken to keep these from becoming environmental toxins (Table 11-2). Neonates have very thin skin and transdermally absorb toxins more readily than adults. The owner should be particularly careful with cleaning agents such as pine oils and phenols. Overuse of bleach or other disinfectants or employing high concentrations of these products puts the neonates at risk. Few disinfectants work well in the face of organic debris, therefore proper cleaning should occur before disinfecting the area (Box 11-4).

TABLE 11-2 Disinfectants*

Disinfectant Effective spectrum of activity
Phenolics Most bacteria except spore formers, possibly some viruses
Alkalis Most bacteria, some spore formers, some viruses
Chlorine Wide bacterial spectrum, viruses and protozoa, little activity vs. spore formers
Chloramine Most bacteria
Quaternary ammonium Most bacteria, some viruses
Chlorhexidine Most bacteria and fungi, poor on spore formers or viruses
Hydrogen peroxide Most bacteria, spore formers and virus

* Use at manufacturer’s recommended concentration.

Significantly decreased activity in organic material.

Sep 11, 2016 | Posted by in SMALL ANIMAL | Comments Off on Neonatal Mortality
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