Plasmodium coatneyi

Plasmodium coatneyi is a parasitic species that is an agent of malaria in nonhuman primates. P. coatneyi occurs in Southeast Asia. The natural host of this species is the rhesus macaque (Macaca mulatta) and crab-eating macaque (Macaca fascicularis fascicularis), but there has been no evidence that zoonosis of P. coatneyi can occur through its vector, the female Anopheles mosquito. While P. coatneyi cannot be transmitted to humans, it is similar enough to Plasmodium falciparum to warrant laboratory study as a model species. Plasmodium coatneyi was first discovered in 1961 by Dr. Don Eyles in the Malaysian state of Selangor. Plasmodium coatneyi was isolated from an Anopheles hackeri before being found in its primate host species. This was the first occurrence of acquiring a new form of malaria through its vector instead of an infected host specimen. The sample was first thought to be Plasmodium knowlesi due to the morphological similarities of the two species, but was later identified as separate due to having a tertiary periodicity compared to P. knowlesi’s quartan periodicity. The presence of P. coatneyi in a host was confirmed in 1963 by Dr. Eyles and his team when the protozoan was discovered in a crab-eating monkey found in the same area Selangor and again in a separate crab-eating monkey in the Philippines. The newly discovered species was then named in honor of Dr. G. Robert Coatney, an American malariologist. The life cycle of P. coatneyi takes the complex form representative of the genus Plasmodium. When a female Anopheles mosquito bites a human, a haploid form of the protozoan called a sporozoite is transferred from the salivary glands into the circulatory system of the human. These motile sporozoites are then taken by the circulatory system to the liver, where they invade the liver cells (hepatocytes). During the next 5–16 days, these sporozoites mature and divide by asexual reproduction into schizonts. Schizonts are structures that contain thousands of haploid merozoites, and rupture to release merozoites into the circulatory system. These merozoites then infect the red blood cells (erythrocytes) where they consume the hemoglobin of the red blood cells for energy and become immature, ring stage trophozoites. The trophozoites act as an intermediate stage, from which two forms can be formed. The trophozoites can mature into schizonts and release more merozoites into the circulatory system, or they can differentiate into still haploid gametocytes. The gametocyte is the sexual stage of the life cycle, with female macrogametocytes and male microgametocytes. Sexual reproduction does not occur in the human host. Instead, the gametocytes only fuse to form a diploid zygote when ingested by the female Anopheles. The fertilization takes place in the stomach, where the zygotes can move into the midgut after they differentiate into motile version of the zygote, an ookinetes. Ookinetes then mature into oocytes inside the epithelial tissue of the midgut. Once grown, the oocyte ruptures and releases sporozoites into the salivary glands of the mosquito. The process then repeats itself through the human host if the mosquito lives long enough to infect a human. When infected with P. coatneyi, the host shows the general symptoms of malaria are fever, headache, chills, vomiting, diarrhea, jaundice, joint pain and anemia. These symptoms occur in the form of paroxysmal attacks, which is a sudden increase of these symptoms after a period of remission. This is due to the release of merozoites from schizonts inside the red blood cells. This cyclic cycle occurs every other day when infected with P. coatneyi, a tertiary periodicity. This is compared to the quartan periodicity shown in some other Plasmodium species, such as P. knowlesi which occurs every three days.