One Health - Sociology

The sociology of the one heath concept for malaria is built around human social behavior in the context of the disease's zoonotic nature. Of the five species of Plasmodium that can infect man (P.malariae, P.ovale, P.falciparum, P.vivax and P. knowlesi), P.knowlesi is a natural pathogen of long tailed and pig tailed macaques in South East Asia and hence considered a zoonosis. (CDC, 2013).  There are numerous reports of the other Plasmodium species arising in the great apes and engulfing an ecological niche created by the movement of humans.

(Singh, 2013)

 Although wild macaques are the original hosts of P.knowlesi, increased human depredations in forest areas has led to human infections. Some scientists theorize that in such an ecological mosaic such as the one that exists in SouthEast Asia, an increase in human interference could force a pathogenic species such as P.knowlesi to switch to humans as its preferred host. (Lee et al.,2011)

Since P.knowlesi multiplies every 24 hrs, cases of infection progress rapidly, often being fatal. The parasite resembles P.malariae (more benign) and is misdiagnosed as such, when diagnosis is based on microscopy. (Cox-Singh et al., 2008) Visitors entering endemic zones are at the highest risks.

 Spread of the disease is influenced by many cultural factors as well. Due to population booms, much more of the forest land has been cleared for agricultural use, driving people and their animals to the edges of forests. People living in such close proximity to the jungle tend to enter it to forage for food, to gather firewood etc, where they encounter the infected mosquitoes.

There are two transmission cycles that ought to be addressed : (1) between macaques and (2) between humans and macaques. The latter occurs in the ecological mosaic where a vector that can bite both primates exists, which can transmit the parasite (Singh,2013; Thrusfield, 2007). Studies of this sort have involved entomologists, landscape epidemiologists, veterinarians etc. The conclusion that was reached was that the disease is transmitted to humans by mosquitoes that normally feed on animals and that human to human transmission does not seem to occur with the same vectors. It is exceedingly interesting to note that no urban outbreaks of P.knowlesi has occurred.

Management of such a zoonotic pathogen requires coordinated, consistent action from health professionals, scientists and the government, which is the basis of One Health. Further epidemiological studies are warranted. These must look at infection rates, describe intrinsic and extrinsic determinants,  notify nosogenic territories, predict persistence and patterns of the disease. Surveillance must be undertaken by governmental agencies and health organizations. Trips into deep jungles by tourists, naturalists intent on discovering new species, military personnel undergoing jungle training and others must be kept to a minimum.

References :

1. Cox-Singh J, Davis TM, Lee KS, et al. Plasmodium knowlesi malaria in humans is widely distributed and potentially life threatening. Clin Infect Dis2008;46:165-171.

2. Lee KS, Divis PC, Zakaria SK, et al. Plasmodium knowlesi: reservoir hosts and tracking the emergence in humans and macaques. PLoS Pathog2011;7:e1002015.

3. Singh B, Daneshvar C. Human infections and detection of Plasmodium knowlesi. Clin Microbiol Rev 2013;26:165-184.

4. Thrusfield, M. V. "7 : The Ecology of Disease." Veterinary Epidemiology. 3rd ed. N.p.: Blackwell, 2007. 116-36. Print.

5.  Day MJ. One health: the importance of companion animal vector-borne diseases. Parasit Vectors 2011;4:49.

6. http://www.cdc.gov/malaria/about/biology/parasites.html