Dealing with the sick newborn puppy

Introduction

Veterinary patients younger than three weeks of age are fragile and — for various reasons — can deteriorate very rapidly when ill. For 85% of puppies that die within the first month of life, clinical signs appear less than five days before death, so newborn puppies that appear to be unwell must be seen as an emergency as soon as an owner has contacted the clinic — and treatment is usually implemented before (and most of the time without) any precise etiological diagnosis. Clinical signs in neonatal puppies are usually nonspecific, and can include respiratory distress, crying, abdominal distension and pain, anorexia, poor weight gain, weakness and hypothermia, but none are pathognomonic for a particular underlying cause.

Initial factors to consider

The owner should be asked to bring not only the sick puppy to the clinic, but also its littermates and the dam; apart from anything else, checking all individuals in a litter can allow early identification of other sick puppies. Examination of the dam may identify a condition that can impact on a puppy’s health — such as metritis, mastitis, agalactia/hypogalactia, invaginated teats (which prevent suckling), or (rarely) vulvar vesicles indicative of a maternal herpesvirus infection. If the owner has been monitoring the weights of the neonates, it is useful for them to bring the figures or growth curves as well. Advice on the correct way to transport neonatal puppies is also vital; since newborn pups have poor thermogenesis, it is important that the ambient temperature during transportation is maintained at around 28°C. However, excess heat is also to be avoided, since newborns are unable to move away from anything that is too hot. Microwavable heated pads or hot water bottles should be used with caution to avoid induced hyperthermia and to prevent skin burns (and cylindrical bottles may also roll and crush newborns). Hyperthermia will not only interfere with the clinical evaluation, as overheated newborns cry and are often hyperactive, it also increases a puppy’s metabolism and thus its energetic expenditure.

Once at the clinic, certain hygiene precautions are advisable. Newborns have an immature immune system and must be protected against nosocomial infections, so time spent in the waiting room should be as short as possible, with no contact with any surface or other animals. Examination should be on a clean, dry surface, preferably heated (e.g., a heat pad set at 28-35°C), using disinfected gloved hands. Ideally, the clinician should also wear fresh clothing.

Clinical examination of the dam

A general clinical examination should include an assessment for signs of bacteremia; for example, is there evidence of infection on the skin, ears or mouth (including dental tartar) of the dam that could represent a source of bacteria? Is there any foul-smelling vaginal discharge indicative of metritis? Check the mammary glands for signs of mastitis, inadequate development of the mammary tissue, and the teat anatomy to verify if the neonates can suckle easily (Figure 1). The dam’s body condition score should also be evaluated to check on her ability to secrete sufficient milk, and her maternal behavior should also be assessed; is the dam interested in her crying pups? However, the clinician should be cautious of the mother when handling the litter, since over-maternal dams may bite in such situations.

The neonatal clinical examination

The clinician should first verify some key facts regarding a puppy’s nutrition over the previous days: how was feeding during the first 8 hours of life managed (i.e., the period where the intestinal barrier is open to allow passive transfer of colostral antibodies) 1, and is the owner bottle-feeding the puppies (as aspiration with potential respiratory complications is possible)? If the puppies were weighed, calculating their growth rate between birth and two days of age is also informative: 96% of puppies that lose weight over this period have had inadequate passive immune transfer 2. Ideally, there should be no weight loss over the two first days of life. Later on, the weights should be compared to the reference growth curve for the breed (Figure 2) 3. The aim is a daily gain of around 2-4 g per kilogram of the expected adult weight, with a minimum target of 1.5 times the birth weight at day 7 and 3 times the birth weight at day 21.

The puppy’s temperature should be measured using a pediatric electronic thermometer with a smooth tip; infrared contactless thermometers are, as yet, unverified for neonates. The normal temperature of the newborn is below that of an adult. As a guide, most puppies will have a mean temperature of 36.5±1°C at day 1, 37.0±1.3°C at day 7 and 37.2±0.5°C at days 14-21 4. There are two critical points to note here. Firstly, a hypothermic puppy should be warmed gradually (increasing at a maximum of 1°C per hour); abrupt warming can lead to death due to peripheral vasodilation and over-activation of cellular metabolism. Warming is ideally done via an incubator, progressively increasing the temperature by one degree more than that of the neonate until 37°C is reached. The incubator should be set at around 55-65% humidity. Secondly, feeding must be delayed until newborns have reached 35°C: a temperature below this point induces intestinal stasis and inhibits digestive enzymatic activity. As a consequence, milk will either stagnate in the stomach and/or remain undigested, providing conditions for bacterial proliferation and leading to bacteremia and death.

A newborn puppy’s hydration status can be difficult to determine, as tenting of the skin is not informative at this age. Dehydration can be determined either subjectively, by assessing the dryness of the oral mucosae, or objectively, by measuring urine specific gravity (SG) using a refractometer (Figure 3). Urine can be collected into a small plastic tube by massaging the perineal region with a cotton bud moistened with lukewarm water, with any SG value higher than 1.030 considered significant. In the absence of a refractometer, the urine color can be helpful; since neonate urine is usually almost colorless, a dark yellow color is indicative of dehydration.

Particular attention should be paid to the umbilicus; this is a major route for bacterial penetration, since the umbilical vein is in direct connection with the liver, and the umbilical arteries with the iliac artery. If the cord remnant has not dried and dropped off within a week of birth, this can be indicative of omphalitis/omphalophlebitis and possibly bacteriemia.

Even if the puppy is already several days old, it is important to assess for congenital abnormalities; these include hydrocephalus, cleft palate and atresia ani. Verify if the owner has noted the passage of meconium or feces, although this can be difficult to ascertain due to maternal cleaning of the puppies. Cardiac assessment may reveal a bradycardia (100-150 bpm); this is often a protective reflex associated with hypothermia, and is not an indication to administer any cardiac drug.

Further diagnostic tests

Blood sampling

Blood can be collected at any age by jugular puncture (using a 23-25G needle), although in neonates it is important to avoid using alcohol on the skin (to limit post-sample bleeding and cooling of the newborn), and the site should be compressed thoroughly for at least a minute afterwards. Nevertheless, jugular puncture is usually much easier for the practitioner than anticipated, and is quite safe for the newborn. Reference values for neonates differ from those in adults (Table 1). Glycemia is the easiest (and most useful) parameter to measure, using a glucometer designed for diabetic patients, and requires only a single drop of blood from an ear prick or paw; collection can be aided by the application of petroleum jelly to the skin.

Table 1. Reference values for blood parameters in neonatal puppies (adapted from 5,6,7,8).

Diagnostic imaging

Radiographic and ultrasonographic examinations can be confusing, because various findings which would be abnormal in adults may be of no significance in newborns (Figure 4). For example, peritoneal effusion is observed in 60% of puppies during the two first weeks of life (and in 30% at one month of age) and is of no clinical consequence; the fluid will spontaneously resolve. Similarly, dilatation of the renal pelvis is observed in 40% of puppies scanned at day 2, 25% at day 7 and 5% at two months of age, without any clinical signs. The neonate renal cortex can exhibit two distinct layers (the external layer being hypoechogenic, the internal more echogenic) on a scan until day 14. Up to day 21, the splenic parenchyma can exhibit a very characteristic “leopard” echotexture, suspected to be associated with activation of the newborn’s immune system (author’s unpublished data).

Further details on clinical examination of the neonatal puppy are available on-line (in French, English and German) as open access at https://neocare.pro/le-developpement-du-chiot/.

Hospitalization – why, who and where

Why hospitalize?

Hospitalization will not only allow specific treatment procedures to be performed (orogastric intubation, fluid administration and drug therapy), it will help ensure intensive monitoring and nursing: the poorly newborn can deteriorate rapidly and often without prior warning. The vast majority of disorders in the young puppy have a bacterial component, but three factors will combine to make the animal a lot worse; hypothermia, hypoglycemia, and dehydration. Hospitalization will help control these elements, and without proper nursing, medical treatments are ineffective. Hospitalization may also help reduce an owner’s concerns and – if death does occur – will enable an autopsy to be performed quickly post-mortem.

Who to hospitalize?

Hospitalizing the dam has the benefit of reducing the nursing burden on the ill puppy, but this means keeping the whole litter, including individuals who are doing well: they are then unnecessarily exposed to the risk of nosocomial disease. In addition, it is difficult to perform intensive care (such as fluid infusion) in young puppies placed next to their mother, as she will lick them and may damage a drip line or other equipment. In general, only the sick newborn should be hospitalized, but if several puppies from the same litter are admitted they must be identified using colored collars. If some or all of litter remain at the clinic, it is important to guard against the development of mastitis in the dam due to lack of suckling activity.

Where to hospitalize?

Ideally a newborn puppy should be in a room away from other in-patients — with an oxygen supply to hand — in a thermostatically controlled pen. This can be a dedicated puppy incubator, a second-hand human neonatal incubator (Figure 5), an avian incubator, or even a home-made device using a large plastic container or aquarium fitted with a cover (but one that allows circulation of air). Small incubators have the advantage of being portable: if the clinic does not have dedicated overnight staff, the veterinarian can take the litter home for treatment, although this is not ideal. Incubators will usually also allow a high humidity (60%) to be maintained: newborns can become significantly dehydrated, losing moisture both via the skin and by the respiratory route, particularly when they breathe open-mouthed. The incubator temperature should typically be around 28-30 °C for the first week of life and 26-28 °C for the following week, but it should be adapted as necessary according to the temperature of the newborns to keep them between 36 and 38 °C. Remember that incubators only provide warmth: they cannot reduce the temperature below the ambient room temperature. In the absence of a thermostatically controlled incubator, heating mats or microwave-safe pads can be used (after checking the temperature at the contact point with the newborns); infra-red lamps are not recommended.

Both the incubator and all surfaces in the holding room should be cleaned and disinfected regularly to ensure a neonate is not contaminated with bacteria from hospitalized adult animals. However, the choice of disinfectant is important, as some can damage delicate neonatal skin. The requirement for disinfection also applies to all equipment needed for feeding the puppies, such as bottles, teats and syringes, and if milk replacer is used, it should be stored as per the manufacturer’s instructions (including between successive hospitalizations).

Medical treatment and intensive care

Rehydration of neonates can be performed by the subcutaneous, intravenous (IV) or intraosseous (IO) routes (the latter using the femur). For the last two options it is important to eliminate air from the administration set before connection to the puppy. Note that the risk for fluid overload (and consequently pulmonary edema) is high in newborn puppies, so when treating moderate to severe dehydration, a bolus of isotonic lactated Ringer’s solution (30-45 mL/kg) should be given, followed by continuous rate infusion (CRI) maintenance at 3-4 mL/kg/h (with dextrose added if necessary) 9. The IV route is to be preferred 10, but an IO catheter should not be left in place for more than 3 days because of the risk of osteomyelitis. Warming the infusion is unnecessary because of the low flow rate involved; heated fluids will simply cool as they pass through the administration set.

To treat hypoglycemia, the puppy should be given an IV bolus of 12.5% dextrose (50% dextrose diluted 1:4) at a dose of 1 mL/kg, followed by CRI using an isotonic (Ringers) solution with added dextrose (1.25-5%). A less-critical newborn with normal body temperature can be given a 5-10% glucose solution at 0.25 mL/30 g 9,10. Sugar solutions (30% glucose or honey) can be administrated orally in order to avoid hypoglycemia, with a few drops applied on the tongue or the inside of the mouth.

Drug therapy in newborns is potentially problematic; before any medication is administered, its safety for neonates must be assessed, and this is best sourced from textbooks (e.g., 11) rather than using a manufacturer’s recommendations, since most drugs have not been evaluated for neonates before approval. Since the majority of neonatal illnesses have a bacterial component, antibiotic therapy is nearly always given routinely. Wherever possible this should be via the subcutaneous or intravenous route; oral administration in smaller animals requires liquid preparations, with a risk of uncontrolled dosage and mis-dosing. Moreover, some antibiotics given orally (especially ampicillin, metronidazole and amoxicillin) may modify (at least temporarily) the digestive flora, increasing the risk of diarrhea. The author’s first choice antibiotics are ampicillin/amoxicillin, and amoxicillin-clavulanic acid, followed by some of the macrolides (erythromycin, tylosin) and cefalexin or ceftiofur. Other antibiotics with known side effects (e.g., aminoglycosides – which can cause nephrotoxicity – and tetracyclines – which can discolor tooth enamel) may be considered, but only for a short period of time, and where no other antibiotic is effective (e.g., if there is no clinical improvement after three days of treatment), or if indicated by the antibiogram results.

Puppy nursing

The success of both medical and surgical treatment relies on the quality of nursing. In addition to administration of injections, fluid infusions and the like, puppies require much more intensive care than older animals, including daily weighing, frequent feeding, and induction of defecation/micturition, not to mention routine preventatives such as scheduled worm treatments. The nursing team will benefit from specific training for neonate evaluation and care. Appropriate nutrition is especially important; feeding can be achieved by either bottle or tube methods (Table 2), but the rectal temperature must first be checked (feed only if temperature > 35°C) and the stomach assessed (feed only if the stomach is empty). If the stomach has not emptied 4 hours after the last meal, check for hypothermia and verify if the puppy has defecated; if the rectum is full, defecation can be stimulated with the tip of a thermometer.

Table 2. Feeding options for neonatal puppies.

Clinical improvement of a poorly puppy is usually demonstrated initially by cessation of constant crying, an improved vitality and normalization of rectal temperature; further reassurance is gained if the hospitalized puppy begins to gain weight within a day or so. It is also essential not to neglect the owners, who will be very worried, and it is important to ensure they are kept informed of the patient’s status, at least once, if not twice, daily. Sending weight charts, photographs or short videos of the puppy feeding keeps owners up to date without wasting a lot of time, and the nursing team can play a central role in this communication.

Continuing treatment – home hospitalization?

Even if the newborn puppy is a potentially valuable pedigree animal, it is often difficult to charge properly for the time spent on hospital care (and perhaps even more so if dealing with a crossbred or unregistered animal). Home hospitalization may be an option after the initial in-clinic treatment, and can be facilitated by owner education sessions; these are especially effective for breeders, as they have more time, a strong motivation, and will often have their own incubator. The ongoing costs are then reduced, and the risks of nosocomial infection reduced. Training the owner in basic techniques (subcutaneous injections, urine SG measurement, and tube feeding (Box 1)) is worthwhile, and once the puppy is back home progress can be monitored via a daily telephone update using the nursing team.

Box 1. Safe tube feeding.

• Select a tube that is 1.5 mm in diameter for animals less than 300 g, 2.6-3.3 mm above this weight.
• Determine the correct length to introduce by measuring the distance between the puppy’s chin and the point of the elbow; mark the distance with a felt-tip pen.
• Fill the syringe with milk warmed to 37°C, allowing 4-5 mL/100 g body weight.
• Attach the tube to the syringe and fill with milk, ensuring all the air is removed.
• Place the newborn in ventral recumbency, with the head and body aligned. Slightly open the mouth by pressing against the sides of the mouth. Keep the head straight and introduce the tube into the mouth (Figure 6).
• Advance the tube towards the pharynx and allow the newborn to swallow it (this should happen even with weak puppies). Note that there is no cough reflex, even if the tube enters the trachea, until 6-10 days of age.
• To avoid regurgitation, the volume of milk is limited (4-5 mL per 100 g body weight) and given over 1-2 minutes to allow the stomach to fill gradually.
• Once feeding is finished, fold the tube in half (to stop further milk flow) before removing it.
• The tube should be cleaned immediately with hot water and detergent, then rinsed and dried before storing in a clean place until the next meal.
• The artificial milk replacer should be freshly prepared for each feeding session.

Main causes of neonatal mortality

If a puppy dies, necropsy, followed by bacteriological, histological and/or PCR examination, can help to identify the underlying cause, which can often be multi-factorial (Box 2). Various specific pathogens have been implicated (Table 3) but non-specific opportunistic bacterial infections leading to septicemia are considered to be responsible for 40-65% of all neonatal deaths 12,13. Newborns are infected mainly by the oral route and/or the open umbilical vessels, with the development of septicemia being dependent on exposure to a significant bacterial load (from the environment or the mother) and/or an intrinsic weakness of the neonate arising from the so-called “4H syndrome” (hypothermia-hypoglycemia-hypoxia-hypovolemia). Other factors may also be involved. Significant parasite burdens (especially roundworms, hookworms, and coccidia) can be a major factor, either by direct competition for nutrients and/or indirectly through causing diarrhea. Parasitism can also be indirectly responsible for bacteremia, with migrating Toxocara larva crossing from the digestive tract to the lungs through the liver, spreading bacteria from the gastrointestinal tract. Finally, some form of trauma may be involved. This may be accidental in origin, with the owner being “aggressive” or impatient when bottle feeding; this is especially possible with weak newborns who have an inefficient swallowing reflex, causing inhalation of milk. Injuries caused by the dam are also possible; if newborns are crushed or bitten by their mother, this may be attributed to inappropriate maternal behavior, but weakness of the newborn itself (from hypoglycemia and hypothermia) is often the initial trigger.

Box 2. Factors predisposing to death in newborn puppies.

Table 3. Specific infectious causes of neonatal death (0-21 days of life).

Necropsy and complementary tests

If a puppy dies it is important to perform a necropsy examination, but certain factors are crucial to optimize the quality of the results: if the examination cannot be performed immediately after death, the puppy should be stored at +4°C. Freezing is inappropriate, as this interferes with histopathology and can confuse even the gross examination after thawing. Practitioners often have to be encouraged to perform a necropsy, possibly because they are concerned that the differences between newborns and adults will be confusing. Nevertheless, gross observation often provides evidence as to the cause of death. For example, it may reveal a failure to ingest milk (empty stomach and intestines, full gallbladder, meconium retention), a major congenital abnormality (e.g., atresia jejuni) or a large parasite burden (parasites visible within the intestines or hepatic scars of Toxocara larval migrans). Photographs of organs at post-mortem can also allow retrospective analysis. Frequently, there will be no obvious lesions at necropsy, but samples should be taken for additional examination (bacteriology, histology, PCR and parasitology) that can help determine the cause of death.

Bacteriological culture is only informative if death occurred less than 6 hours before necropsy, otherwise bacteria escape from the digestive tract and contaminate other organs. A sterile swab is introduced deep into the splenic parenchyma and transferred into a sterile vial, having taken care to avoid contamination when opening into the abdominal cavity. The entire spleen can also be collected in a sterile manner. If necessary, samples should be refrigerated before being sent to the laboratory, which should receive them for analysis within 24 hours.

Tissues for histology should be taken into 10% formalin (3.4% formaldehyde). Samples should be no more than 5 mm in thickness, and must be processed (using a paraffin-embedded technique) within 7 days of collection to allow optimal interpretation by the pathology laboratory.

Parasitology assessment can be via gross examination of intestinal and rectal contents, but can also be aided by histological samples (e.g., for Neospora and Toxoplasma).

Finally, if the cadaver was frozen before necropsy and/or there are signs of autolysis, PCR is the only reliable examination option; quantitative (real time) PCR can provide useful information for most infectious agents.

Conclusion

Caring for a sick neonatal puppy relies much more on appropriate nursing, supportive fluids and antibiosis therapy than on any specific medication. Rapid instigation of treatment is a key element for success, together with appropriate preventative measures for all littermates. In most cases, clinical signs before death are of short duration and very similar whatever the underlying cause, and treatment is not infrequently unsuccessful. A proactive approach should be implemented to control neonatal mortality, and a visit to the breeding facility is the best way to evaluate the peripartum organization, with a focus on pregnancy and whelping management, revival and nutrition of the newborns, hygiene procedures and environmental conditions.