Introduction

The total prevalence of perinatal puppy deaths in dogs varies with colony, breed and country and is in the order of 10-30% from birth to weaning. Mortality occurs most frequently during the first week of life, as much as 75% of all neonatal disease and deaths occur at this time. In kennels with hygiene problems or endemic diseases, such as canine herpesvirus (CHV1), the overall incidence may reach 30%. A preweaning loss of more than 20% and postweaning losses of more than 10% are reasons for major concerns in a kennel. Furthermore, disproportional losses to any particular cause are reasons for major concern regardless of the overall percentage.

Causes of Neonatal Disease

The emergence of problems particularly with endemic herpesvirus infection has led to an increase in neonatal diseases and deaths. However, the puppy loss due to non-infectious causes may remain unchanged or fluctuate due to management, surveillance of deliveries and follow-up of the puppies and mother, particularly during the first week. Non-infectious causes of puppy death during the first 3 weeks of life are often linked to problems developed while the foetus was in the uterus or problems associated with parturition. The most common problems during nursing and weaning that can cause neonatal disease include various bacterial and viral infectious diseases, as well as parasites. Parvovirus (CPV1) and canine herpesvirus are primary aetiological factors in puppy disease and death between the ages of 0 and 12 weeks. Escherichia coli, Staphylococcus spp. and Streptococcus spp. bacterial infections are also commonly associated with disease in newborn puppies.

Non-Infectious Causes

Physiology and Parturition

Extended labour due to uterine inertia (primary or for instance due to hypocalcaemia) or difficulty passing the puppy can result in potentially fatal traumatic injuries. Congenital anomalies, including stillbirth, may account for up to 40% of early puppy deaths. It is sometimes difficult to differentiate congenital from acquired disease. Genetic factors play a role in the development and growth of the foetus and newborn puppy. There are significant physiological differences between neonatal pups and older puppies. Differences such as immaturity in the regulation of body temperature, blood sugar and resistance to infection should be considered.

Warmth is essential for newborns because temperature regulation is impaired just after birth. Rectal temperatures do not reach 'normal' (37.5-38.5°C) until the pups are approximately four weeks when they more efficiently metabolise food. An ambient whelping box temperature of 24-27°C, with a relative humidity of 55-65% is desirable during the first week, though it can be somewhat lower if the dam is present to provide body heat and warm milk. Neglect of the newborn, either due to a nervous, highly strung mother, lack of milk ejection and udder oedema, or maternal illness, usually results in early puppy death. Newborn pups generally do not recover well from only a few hours of chilling, so it is important that the bitch is present almost continuously the first days.

Nutrition and Metabolism

Nervousness and restlessness can also be induced by hypocalcaemia and hypoglycaemia; the condition is treatable without harm to the puppies. Calming drugs may be used in extremely nervous or aggressive bitches, but care must be taken not to sedate the puppies.

Pregnant bitches that are fed a low-quality diet deficient in carbohydrates or other essential nutrients have a higher incidence of fading puppies. The offspring of nutrient-deficient mothers are often born weak, diseased and underweight. In very large litters, some puppies suffer from uterine malnutrition due to competition with other developing foetuses. Bitches may become hypoglycaemic during the last week of pregnancy and pregnancy ketosis or pregnancy toxaemia may be induced, which is the result of a more latent relative lack of carbohydrate (CH) supply or a pregnancy-related change in CH metabolism. Large litters may predispose to this condition. Hypoglycaemic bitches and bitches with an increase in blood beta hydroxybutyrate resulting from a CH-restricted diet in late pregnancy experienced a reduced survival rate of their pups.

Foetal size and neonatal weight significantly influence survival rate. If the birthweight of individuals or all pups is more than 25% below the average for the breed, survival rate is significantly reduced. In normally developing puppies the birthweight should double in 8-10 days. Hence, an increase in body weight of 15-20% per day is not unusual. Comparison with littermates is useful in these cases.

If the mother develops clinically overt diabetes mellitus during her pregnancy, the hyperglycaemic situation resulting from insulin deficiency or insulin resistance, which may occur as early as 35 days post ovulation, may stimulate the foetal growth hormone to induce excessive growth of the foetus (large offspring). These puppies tend to be too large for a normal delivery. They also experience a significant hypersecretion of insulin in response to the previous hyperglycaemic state, and they may then become hypoglycaemic in a lower CH environment postpartum. Maternal diabetes may also disturb placental function, and the severely hyperglycaemic bitch rarely carries her foetuses to term.

Fading Puppies

The term fading puppy was first restricted to those that died of an infection with canine contagious hepatitis (HCC) and haemolytic streptococci. Later on the term was revised to include also non-infectious causes. Fading puppy syndrome is characterised by a pattern of increasing weakness, failure to nurse, weight loss, hypothermia and death prior to weaning, usually within the first 2 weeks of life. It is now generally accepted that this is not a single disease entity, but rather that common clinical signs are caused by different underlying disease processes. There are no obvious clinical signs or pathological findings, such as poor mothering, mastitis, neonatal canine herpes infections, or malformations. Fading puppies usually have a low birthweight, are restless and cry, often beginning shortly after birth. Normal puppies are quiet unless they are diverted from the mother and their littermates. Birth defects, which include both genetic as well as drug or environmental causes, account for a large number of fading puppies.

Infections

Zoonoses--The Not So Innocent Bacteria

The presence of foul-smelling dark or blood-tinged watery faeces in newborns is cause for immediate concern. Campylobacter spp. or Salmonella spp. and enterotoxic strains of E. coli (0103, 0157) may affect puppies and may pose a risk to the other dogs in the kennel as well as to humans. Disposal of potentially contaminated faeces should be done using hygienic measures, gloved hands and should be followed by proper disinfection. Bacteriological culture may be necessary to arrive at the correct diagnosis.

Neonatal Sepsis

The most feared incident in a kennel is neonatal sepsis in which normal puppies are healthy at birth and within hours are all squealing, and then within the next day one by one they all start to become ill and die. This may also be part of the fading puppy syndrome since the aetiology may include a variety of factors that may influence the immune response to bacterial, viral or fungal infection. Umbilical trauma and invasion may be the route of infection in single puppies, but the gastrointestinal or respiratory routes may often also be involved when the whole litter becomes ill. These puppies should be treated immediately: gradual warming, turning and massage of the body, rehydration and nutrient supply and probiotics, sometimes also including antibiotics.

The third generation cephalosporins, ceftiofor sodium, are considered an appropriate choice for neonatal septicaemia at a dose of 2.5 mg/kg s.c. q12h for 5 days maximum. Drug distribution and elimination may be severely diminished in these puppies, and doses should be less than 50% of adult dose. Normoglycaemia can be maintained by giving 2-4 ml/kg of a warm 10% dextrose solution via the oral or subcutaneous route, but hyperglycaemia due to treatment should also be controlled, since neonate puppies have reduced metabolic regulatory capacity. Weighing of the patient regularly and measurement of rectal temperature, which should be at least 36°C, are both necessary. The mother should receive antibiotics if one decides to treat the puppies, but treatment of the dam only may not be sufficient.

Prevention

Prevention of disease in newborns is based on the principle of good management of the dam, hygienic measures in the whelping room and kennels, appropriate vaccines and deworming programmes and proper postnatal care of dam and pups. If the puppies fall ill, treatment is a challenge, because diagnosis is often difficult, symptoms may be different to those of older young and adults, and many of the drugs available for treatment in dogs may pose a risk to the newborn.

References

1.  Davidson A. Husbandry and clinical management of the neonate to optimize survival. In: Proceedings of the 2nd EVSSAR/ESAVS Course: reproduction in companion, exotic and laboratory animals, School of Veterinary Medicine Hannover, 2003; 19.1-19.6.

2.  Günzel-Apel A-R. Non infectious causes of pregnancy loss a/disturbed pregnancy in dogs and cats. Reproduction in companion, exotic and laboratory animals 2nd ESAVS course, Hannover, 2003; Volume 2: 17.1-17.11.

3.  Johnston SD. Canine and feline theriogenology (first edition). Philadelphia: WB Saunders Company, 2001; 66-104 (A list of drugs and safety recommendations for pregnant and lactating dams is found on pp. 81-85).