Protein infectious particles are proteins called “Prions” that causes brain and neurological diseases in animals and humans. For so many years, scientists classified most foodborne disease causing agents as chemical, viral, bacterial and other organisms but not “protein” on its own. Hence, the knowledge of prion changed all known factoids about science and disease causing agents. In 1982 Stanley Prusiner, a noble prize winner, classified this class of an unknown protein as prions, meaning “protein and infectious” or “infectious protein”, a protein without nucleic acids discovered from scrapie and Creutzfeldt-Jakob disease (CJD) (Prusiner, 1997). In animals, prion causes bovine spongiform encephalopathy (BSE) known as mad cow disease. In the sheep, prion causes a disease known as scrapie (Moeller, 2011). Other forms of prion disease in animals are chronic wasting disease (CWD), transmissible mink encephalopathy, feline spongiform encephalopathy, and ungulate spongiform encephalopathy (CDC, 2012). In humans, prions are associated with diseases such as Creutzfeldt-Jakob disease (CJD), variant Creutzfeldt-Jakob disease (vCJD), Gerstmann-Straussler-Scheinker syndrome, fatal familial insomnia, and Kuru (CDC, 2012).

Kuru in Fore, New Guinea, is another prion version supposedly endemic to Fore culture. Asserting carefully and cautiously; the first remembered cases of Kuru was in 1920, when Kuru was reportedly noticed by Australian administration in New Guinea in 1950s (Mead et al., 2003). The prevalence of Kuru was high in New Guinea because of the Fore mortuary feast, eating part of the brain of the deceased relatives. The feast was never an ancient cultural practice in Fore, New Guinea. The mortuary feast wasintroduced in New Guinea in the late 19th century (Mead et al., 2003).

The incidence of Kuru declined significantly after the ban of the cannibalistic-deceased feast, in 1950’s (Mead et al., 2003). Consequently, there are no incidence of Kuru in individuals born after the late 1950s in New Guinea (Mead et al., 2003). Perhaps, cannibalistic feast did not introduce or cause Kuru. The feast was a very effective medium for spreading the disease from infected remains to living relatives. This theory wassupported by several reports of iatrogenic CJD (from medical procedures, dural grafts, corneal grafts, blood transfusions, etc.) observed in Europe, America, Japan and the other part of the world (Mead et al., 2003). The cause/origin of prion is unknown.

Scrapie, the sheep version of prion has been in existence globally especially in Europe for more than two centuries (Walter, Walsh, Farnsworth, Winkelman & Miller, 2011). Prion prevalence is 1 per million with a lifetime risk of 1 in 50,000 (Mead et al., 2003). Theoretically, the risk factor can be used to extrapolate the possibility of the prevalence of prion prevalence in countries or continents based on the population and exposure risks. Furthermore, most countries in African have very poor medical infrastructures and medical database, and because there is no reliable screening test for prion globally, identification of early detection of prion is very challenging especially in African continent and most developing countries (Belay & Schonberger, 2005).

Unfortunately, prion has a long-time incubation period, sometimes 20 years. The incubation time prior to symptoms or penetrance of the disease is very long because of several factors. One of the factors is the polymorphism effect. Individuals with codon polymorphism at 129 of PRNP has strong susceptible factors to human prion diseases. Homozygosity at PRNP codon 129 is predisposed to iatrogenic and sporadic CJD. Heterozygosity confers resistance by inhibiting homologous protein interaction (Mead et al., 2003). In addition, all humans have normal prion proteins in their brain and cells, whose functions are not yet known. Therefore, the possibility of long intrinsic and extrinsic interactions of the protein with synergistic factors within the body initiating infectious prion particles is a possibility.

Prion infects the brain and neurological protein. It corrupts normal functioning proteins by changing their form and normal activities, therefore, inducing abnormal folding of specific normal cellular proteins, which is known as the prion proteins in the brain. When an animal is infected, the incubation time is about 4 years, therefore, making it very hard to control the disease or eliminate infected animals without killing thousands of animals in the process (Moeller, 2011). In the United Kingdom where 180, 000 incidence of mad cow was reported, 4.4 million cows were killed just to eradicate the presence of the disease and reduce the chances of human infection (Moeller, 2011). Prion disease or transmissible spongiform encephalopathy (TSE) causes neurological spongiform changes with neuronal function loss and loss of the inflammatory response (CDC, 2012).

Thus far, the functions of normal prion proteins are not completely known. The abnormal folding of the prion proteins in the brain are characteristics of the disease. The disease is known to have a progressive and fatal outcome (CDC, 2012). Unfortunately, till date there is no known cure for the disease. Prion is a transmissible protein. It is believed in the scientific community that prion may have originated from feeding herbivores (e.g. cattle) remains of death cattle containing the prion agents. Also, it is clearly understood in the scientific community that prion agents are not destroyed by normal cooking or “well-done” cooking recipe (Moeller, 2011). Thus, making prion a highly temperature resistant protein. Other factoids indicated that the traditional sterilization measures are ineffectual in deactivating prion. In fact, prion can survive autoclave sterilization.

By 2009, 164 people have been killed in Britain by prion and 42 others reported in other places (Moeller, 2011). The figure may not be accurate because there is no robust and reliable tests readily accessible in diagnosing the disease in many countries. The best remedy for this pathogen and disease is preventing infectious animal introduction into the food chain. Furthermore, based on the known cases of prion, many agricultural agencies recommended complete eradication of animal feeding practices or procedures that include animal remains in agricultural feeding-practices. Moreover, in 2009, scientific analysis implicated prion gene as possibly a member of ZIP family metal-ion transporters, promising findings on possible medical intervention on prion disease (Science Daily, 2009). ZIP protein family are zinc transporter and can also transport other metals across cell membranes (Science Daily, 2009).

References

Belay, E. & Schonberger, L. (2005). The public health impact of prion diseases. Annual Reviews Public Health 26. 191–212. doi:10.1146/annurev.publhealth.26.021304.144536. Retrie ved from http://www.cdc.gov/ncidod/dvrd/prions/resources/BelayE_Annu_Rev_Public _Health.pdf

Centers for disease control and prevention (CDC). (2012). Prion disease. Retrieved from http://www.cdc.gov/ncidod/dvrd/prions/

Mead et al. (2003). Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics. www.gs.washington.edu/news/artBalancing Selection at the Prion Protein Gene Consistent with Prehistoric Kurulike Epidemicsicle.pdf

Moeller, D. (2011). Environmental Health (4 ed.). Harvard university press, Cambridge, Massachusetts

Prusiner, (1997). Stanley B. Prusiner – biographical. Retrieved from http://www.nobelprize.org /nobel_prizes/medicine/laureates/1997/prusiner-bio.html

Science Daily. (2009). Evolutionary origins of prion disease gene uncovered. Retrieved from http://www.sciencedaily.com/releases/2009/09/090928131210.htm

Walter, W., Walsh, D., Farnsworth, M., Winkelman, D., & Miller, M. (2011). Soil clay content underlies prion infection odds. Nature Communications, 2 (200). doi:10.1038/ncomms1203