Neonatal Pathology

Twinning is common in the giant panda, with one neonate usually rejected by the dam at birth. Hand-rearing the rejected cubs is challenging but has become more successful in recent years (see Chapter 13).

The species is highly altricial. A newborn cub is generally 10 to 15 cm long and weighs 60 to 200 g. The per cent body weight ratio of cub to mother is only about one-tenth of one per cent, which is more typical of a marsupial than eutherians. Necropsy and histological assessments of giant panda neonates have revealed an underdeveloped immune system (compared with domestic carnivores), including a haemolym-phatic organisation that contains few lymphocytic cells. Any interference with colostrum intake within the first few hours of life renders the infant extremely vulnerable to sepsis and death (Knight et al., 1985; Montali et al., 1990).

Research into the neonatal immunity of giant pandas and im-munoglobulin (Ig) supplementation is just beginning, but its importance is well recognised. One impediment to progress in this area has been the unavailability of stored colostrum or sufficient volumes of panda serum for supplementation. In the USA, concentrated Ig of the horse, cow and cat are commercially available for oral or parenteral use in hypoimmune neonates (generally <400 mg dl_1 of Ig) of those species. The Smithsonian's National Zoological Park has begun to bank serum from the resident female giant panda (studbook, SB, 473) and is collaborating with a commercial producer of purified Ig to generate a lyophilised product in preparation for future giant panda offspring. Methods of evaluating the immune status of neonates will continue to be challenging due to the small size of cubs and the hesitation to perform invasive procedures such as venipuncture.

The factors responsible for the deaths of eight giant panda neo-nates born at the zoos in Washington, DC, Mexico City and Madrid were evaluated in a study by Montali et al. (1990). Of the eight deaths, six were associated with infections involving frequently identified, ubiquitous organisms such as Escherichia coli, Staphylococcus spp. and Pseudomonas spp. (Fig. 16.6; Plate XIX). The frequency of fatal opportunistic infections in neonatal giant pandas suggests that failure of passive transfer may be a significant problem in this species (Montali et al., 1990).

Neonatal bacterial infections were also the leading cause of death in a study of 17 cubs less than 30 days of age in Chinese giant panda breeding facilities (B. Rideout, unpublished data). The umbilicus appeared to be the primary portal of bacterial entry regardless of whether the cub was mother- or hand-reared. Accidental maternal trauma was the second most common cause of death in this survey, but some traumatised neonates also had evidence of pre-existing bacterial infections.

Figure 16.6. (a) Gross necropsy (liver) of neonate with septicaemia and hepatitis caused by Staphylococcus intermedius. (b) Lungs (L) of a neonate that acquired pneumonia prenatally from a dam with an ascending urogenital tract infection that caused chorioamnionitis. (c) Microscopically the pulmonary alveolar spaces contained inflammatory cells (arrow). Pseudomonas aeruginosa was cultured from the lungs and P. fluorescens from heart blood. (See also Plate XIX.)

Figure 16.6. (a) Gross necropsy (liver) of neonate with septicaemia and hepatitis caused by Staphylococcus intermedius. (b) Lungs (L) of a neonate that acquired pneumonia prenatally from a dam with an ascending urogenital tract infection that caused chorioamnionitis. (c) Microscopically the pulmonary alveolar spaces contained inflammatory cells (arrow). Pseudomonas aeruginosa was cultured from the lungs and P. fluorescens from heart blood. (See also Plate XIX.)

Chronic, subclinical infections in the dam may also compromise the newborn giant panda. Four of the five cubs produced by SB 112 (Ling Ling) at the Smithsonian's National Zoological Park over a six-year interval died of bacterial infections within the first three days after birth (one cub was a stillborn, a twin). Her second cub acquired an infection in utero due to bacterial chorioamnionitis (see Fig. 16.6b). It died three hours postpartum (Montali et al., 1990), presumably due to an ascending infection caused by the dam masturbating during late pregnancy (Bush et al, 1984). SB 112 developed an acute pyelonephritis four months after parturition (Bush et al, 1984), but responded well to treatment and became pregnant again the next breeding season. As all of SB 112's live-born cubs died shortly after birth of sepsis, it is possible that she maintained a chronic, low-grade urogenital tract infection that carried over to all offspring at parturition.

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