Standard growth and diarrhea-associated growth faltering in infant rhesus macaques

Growth charts for captive infant rhesus macaques were unchanged for 30 years while diet, husbandry, and social housing strategies evolved onward. The Oregon National Primate Research Center published updated standard growth charts for infant rhesus macaques raised in outdoor social housing, and the methods are available to other research breeding centers to make their own standard growth charts. The standard growth of healthy infant rhesus macaques is a tool to facilitate identification and early intervention of infants at risk for growth faltering. In addition to our growth charts, our publication in the American Journal of Primatology showed a strong association between diarrheal disease and growth faltering of infant rhesus macaques between 5 and 12 months old, a critical point in life for infants weaned from their dam’s breast milk. Often diarrhea is difficult to track in outdoor group-housed infants, and the disease may appear subclinical, impeding clinical intervention until only after dehydration signs are visible. We established the growth faltering infant program to identify infants at semi-annual physical exams using the standard growth charts. Colony managers and veterinarians intervene diarrhea and growth falter early, and, after body weight recovery, infants return to their outdoor social group. We hope collaborations with other rhesus macaque colony managers and veterinarians will lead to refinements of growth standards for widespread use. Our current growth standards and growth faltering cut-offs are described as formulas in the following table.

Infant growth forumlas (a)
Housing TypeGroupStandard (50th percentile)Growth faltering cut-off (3rd percentile)
Open-earthFemalesWeight = 4.0 × age + 471Weight = 4.0 × age + 160
Open-earthMalesWeight = 4.1 × age + 502Weight = 4.1 × age + 191
Sealed-concreteFemalesWeight = 4.4 × age + 432Weight = 4.4 × age + 122
Sealed-concreteMalesWeight = 4.7 × age + 461Weight = 4.7 × age + 150

a. Growth is defined by weight in grams as a function of age in days. These formulas were derived using weight records of infants up to 1 year of age. Growth faltering cut-off weights were associated with diarrheal disease in infants aged between 5 and 12 months.

Reference: Haertel et al. 2018. Standard growth and diarrhea-associated growth faltering in captive infant rhesus macaques (Macaca mulatta). American Journal of Primatology 80(9): e22923.

Improving rhesus infant growth velocity and reducing enteric disease with campylobacter vaccination

In humans, symptomatic and asymptomatic Campylobacter infections reduce growth of children in the poorest environments, and campylobacter is highly prevalent in the rhesus colony at Oregon National Primate Research Center. We hypothesized growth trajectories and clinical outcomes of rhesus macaque infants would improve if given a campylobacter vaccination. We are measuring infants longitudinally up to 1.5 years old and collecting microbiome and histology samples. In preliminary results, we have found campylobacter diarrheal disease incidence in infant rhesus was significantly reduced in breeding groups given the campylobacter vaccine.