HELMINTHS AND HYPEROSTOSES: USING SPATIAL EPIDEMIOLOGY TO MODEL CLIMATOLOGICAL RISK FACTORS AND BIOLOGICAL ADAPTATION TO TERRESTRIAL PARASITIC INFECTION IN THE PREHISTORIC PERUVIAN ANDES

Cribra orbitalia (CO) and porotic hyperostosis (PH) are cranial porosities in human skulls that are considered to be markers of childhood iron-deficiency anemia caused by parasitic infection, malnutrition, chronic disease, or any combination of these etiologies. The presence of these lesions, when healed, indicates an individual survived their illness, while lesions that are active at the time of death suggest that infection contributed to mortality. Recent bioarchaeological studies suggest that these lesions in prehistoric Andean skeletal populations are more associated with environmental risks such as parasitic infection than dietary malnutrition (Blom et al. 2005; Turner and Armelagos 2012). Soil-transmitted helminths such as Trichuris trichuira (whipworm), Ascaris lumbricoides (roundworm), and Necator americanus and Ancylostoma duodenal (hookworm) have been documented in ancient and modern Peru, and are known to cause hemolytic anemia, which can contribute to bony hyperostoses. These terrestrial worms are typically transmitted through feces-contaminated soil, so barefoot children are often infected more than adults. Soil-transmitted helminths thrive in moist, warm, shady environments in either sandy loam or clay soil.

This study takes a spatial epidemiological approach to mapping published and new CO and PH prevalence data for skeletal samples with known provenience throughout the southern Andes. Using GIS, the author analyzes the spatial distribution of hyperostoses and investigates relationships between hyperstosis hot-spots and regions that are highly suitable for helminths, based on mean annual temperature, precipitation, shade, and soil type. This study further clarifies risk factors for morbidities resulting in hyperostoses and the nature of human biological adaptation to infection by soil-dwelling worms.