There is no evidence of kuru (or other prion disease) that I am aware of in Mesoamerica. Of course, the historical record is not perfect, but there is little reason to believe a kuru-like illness would have been prevalent in Mesoamerica. To understand why this is the case, let's first talk about what kuru is.

Kuru is a particular type of spongiform encephalopathy caused by abnormal proteins called prions. There are spongiform encephalopathies which can be inherited or through spontaneous mutation (such as Cruetzfeld-Jakob disease), but when we are talking about kuru we are specifically talking about a transmissible form of disease, one that can be passed from person to person. Specifically we are talking a transmissible spongiform encephalopathy (TSE) spread through an oral route, rather than through direct inoculation.

As the rarity of TSEs implies, prion disease is actually somewhat hard to acquire and transmission is dependent on a number of factors including the dose of the exposure and the route (Collinge 1999). Cross-species exposure can also reduce the ability of prions to cause disease; "mad cow" in the UK has resulted in only a couple hundred cases over the course of decades. There are also genotypes which are more and less susceptible to infection. Being exposed to prions via a medical procedure carries the highest transmissibility, with the oral route being much less efficacious at spread disease. Even with the oral route, certain tissues are much more infectious than others.

In the case of kuru, there was no cross-species barrier, but the route was oral which might have prevented or slowed the spread of disease. The specific funerary rituals among the Fore in the eastern highlands of Papua, however, meant highly infectious tissue was consumed. Specifically, the Fore practiced mortuary cannibalism wherein the bodies of recently deceased biological and social relatives were consumed. All body parts (except the gallbladder) were consumed, and the brain was particularly prized (Liberski et al. 2012). In addition, not all member of the Fore participated in mortuary feasting equally. It was primarily adult women who were consuming human tissue, particularly the highly infectious brain, which meant kuru was predominantly an epidemic among women (Lindenbaum 2008).

Among men and older boys, who either did not eat or consumed minimal portions of human flesh, kuru was relatively rare. Less than 2% of all cases occurred in men. In addition, a particular genotype has been identified as being more susceptible to prion disease. Individuals who have two copies of the same amino acid at a certain codon fall ill more quickly, while those who express two different amino acids at that location have protective effects. Heterozygous individuals can have incubation periods that are decades long. The last few cases of kuru occurred in people who were exposed, at minimum, 30-40 years prior to onset of disease, and possible as long as 50+ years prior to showing symptoms. Many of these late cases were heterozygous individuals who had been exposed as children and lived the majority of their lives symptom free (Collinge et al. 2006).

Just to sum up before applying the lessons of kuru to Mesoamerican cannibalism. Kuru is a type of disease caused by an infectious protein. Prion diseases are poorly transmissible through ingestion, but this can be overcome by eating certain tissues which have higher levels of prions and are thus more infectious. Certain genetic profiles can be more or less susceptible to disease, with resistant types taking several decades to manifest symptoms.

Tackling the genetic question first, the pattern of human genomes which are protective against prion disease has led some researchers to suggest heterozygosity was selected for in human evolution through prehistoric prion epidemics which may have been due to cannibalism (Mead et al. 2003). In an area like Mesoamerica where cannibalism has been at least somewhat endemic, perhaps the population has been selected to be genotypically resistant to prion disease? Well... Soldevila et al. (2006) examined the distribution of relevant codons on a continental/regional basis and found variability, but nothing that showed a clear signal that could be teased out from founder effects and other selection pressures.

The pattern of cannibalism in Mesoamerica is more relevant, as it is significantly different from what was practiced by the Fore. The latter group consumed organs and tissue which are particularly pathogenic, whereas in Mesoamerica the practice was to only eat skeletal muscle, with the offal being discarded (Ortiz de Montellano 1978). Bernal Diaz de Castillo alludes to this pattern when wrote that sacrificed Spaniards had their "legs, arms, and other parts of the body being cut up and devoured" while "the entrails alone were thrown to the tigers, lions, otters, and serpents" kept in Motecuhzoma's menagerie. Prions are most prevalent in nerve tissue and the lymphatic system, including in the gastrointestinal tract. While some prion diseases do show pathologic proteins in the muscle, this is not the pattern in human prion diseases (Head at al. 2004).

Furthermore, while Fore mortuary feasts were events which brought together large, disparate groups of people upon the death of a relative, Aztec cannibalism which a much more limited practice focused on war captives. Despite sensationalist Colonial writings about mass consumption and human butcher shops, the actual evidence for cannibalism among the Aztecs is scarce and points to small amounts of flesh consumed at irregular intervals by a small group of people (Isaac 2005). Basically, whereas the Fore had mass consumption of flesh at semi-regular events (death rates being what they were), the only people regularly consuming human flesh in the Mesoamerican Postclassic were elite warriors, with occasional consumption by common foot-soldiers.

Finally, the fact that Aztec cannibalism was largely predicated on capturing enemy warriors in battle means a certain selection pressure away from potentially infectious individuals. The kuru outbreak in Papua is thought to have originated from an individual who died of spontaneous Cruetzfeld-Jakob disease, who was then consumed at a mortuary feast, thereby disseminating the infectious agent into the population. The Fore ritually consumed at least parts of all deceased persons, excepting those with leprosy, dysentary, or yaws. Individuals who died of kuru were not exempt from mortuary feasting and were actually somewhat favored (Liberski et al. 2012). TSEs manifest their effects over time through the accumulation of misfolded proteins in nerve tissue, so the Fore were eating people who literally had high enough levels of prions to have advanced to fatal disease. Mesoamerican soldiers fit enough to take part in battle would, be definition, not have this level of prion accumulation.

Lack of evidence of some sort of kuru-like disease in Mesoamerica does not preclude its existence, and there certainly is a hypothesis that human populations were shaped in the past by cannibalism. The actual practices of cannibalism among the Fore and the Aztecs, however, were significantly different. The pattern of who was consumed, how frequently, and what parts were eaten all differed and all of those factors can affect the transmission of prion disease. While a prion epidemic can't be ruled out in Mesoamerican prehistory, such events should not be thought of as an inevitable result of cannibalism.

---

Collinge 1999 Variant Creutzfeldt-Jakob Disease The Lancet 354(9175), 317-323.

Collinge et al 2006 Kuru in the 21st century—an acquired human prion disease with very long incubation periods. The Lancet, 367(9528), 2068-2074.

Head et al 2004 Peripheral tissue involvement in sporadic, iatrogenic, and variant Cruetzfeld-Jakob disease: An immunohistochemical, quantitative, and biochemical study. American Journal of Pathology 164(1), 143-153.

Liberski et al 2012 Kuru: Genes, cannibals, and neuropathology. Journal Neuropathology & Experimental Neurology 71(2), 92-103.

Lindenbaum 2008 Understanding kuru: the contribution of anthropology and medicine. Philosophical Transactions of the Royal Society 363(1510).

Mead et al 2003 Balancing Selection at the Prion Protein Gene Consistent with Prehistoric Kurulike Epidemics. Science 300(5619).

Ortiz de Montellano 1978 Aztec cannibalism: An ecological necessity? Science 200(4342), 611-617.

Soldevila et al 2006 The prion protein gene in humans revisited: Lessons from a worldwide resequencing study. Genome Research 16(2), 231-239.