Chapter 9: Apicomplexa—Malaria, Babesia, and Theileria (Vocabulary Flashcards)

Vocabulary-style flashcards covering Plasmodium malaria biology, disease features, and related genera Babesia and Theileria.

Plasmodium spp.

Genus of Apicomplexan parasites that cause malaria in humans; transmitted by Anopheles mosquitoes; life cycle includes sporozoites, merozoites, and gametocytes.

Malaria

Disease caused by Plasmodium spp.; characterized by fever, anemia, and organ damage; transmitted by Anopheles mosquitoes.

Definitive host

Host in which the sexual cycle occurs; for malaria, the Anopheles mosquito.

Intermediate host

Vertebrate host (mammals, birds, or reptiles) in which asexual replication occurs during the Plasmodium life cycle.

Vector (in malaria context)

Anopheles mosquito that transmits Plasmodium sporozoites to hosts.

Sporozoite

Infective stage transmitted by mosquito bite; travels to the liver to initiate hepatic schizogony.

Merozoite

Form released from liver or red blood cell schizonts that invades red blood cells.

Schizogony

Asexual replication producing multiple merozoites within liver cells or red blood cells.

Ring stage

Early trophozoite inside an erythrocyte with a ring-like appearance and a large food vacuole.

Gametocyte

Sexual stage formed in red blood cells; taken up by mosquitoes to continue the life cycle.

Gametogony

Sexual development of Plasmodium in the mosquito gut, leading to zygote and ookinete formation.

Ookinete

Motile zygote in the mosquito gut that penetrates the gut wall to form an oocyst.

Oocyst

Encapsulated parasite stage in the mosquito that releases sporozoites for transmission.

Hypnozoite

Dormant liver stage of certain Plasmodium species that can relapse after months or years.

P. falciparum

Most virulent human malaria parasite; causes high parasite load, multiple RBC infection, and cytoadherence with vascular sequestration.

RBC knobs

Surface knobs on infected red blood cells that promote cytoadherence to blood vessels.

Cytoadherence

Adherence of infected red blood cells to vascular endothelium, contributing to sequestration and disease severity.

Sickle cell trait and malaria resistance

Presence of hemoglobin S provides partial protection against severe P. falciparum malaria.

Endemic malaria

Stable, ongoing malaria transmission with predictable patterns.

Unstable malaria

Erratic malaria transmission with potential outbreaks and higher risk of mortality.

Hypnozoite (clinical relevance)

Dormant liver stage (P. vivax/ovale) that can cause relapses of malaria.

Sources of malaria in the United States

Imported cases from travelers/immigrants; transfusion- or donor-derived cases; occasional autochthonous cases.

Babesia spp.

Genus of tick-borne Apicomplexa causing babesiosis; parasites invade red blood cells like malaria parasites.

Babesia canis

Causative agent of canine babesiosis; causes hemolytic anemia in dogs.

Texas red-water fever

Cattle babesiosis caused by Babesia bigemina/bovis; transmitted by Boophilus annulatus; marked by hemoglobinuria (red urine).

Boophilus annulatus

Cattle tick vector for babesiosis; transmits Babesia spp. to cattle.

Transovarial transmission

Vertical transmission of pathogens from an infected female tick to its offspring.

Life cycle of Babesia

In mammals: merozoites invade RBCs and proliferate; in ticks: sexual reproduction occurs, producing sporozoites that reinfect hosts.

Zoonotic babesiosis increasing in the US

Rising human babesiosis cases due to expanding tick vectors and exposure; often caused by Babesia microti.

Theileria parva

Parasite causing East Coast Fever in cattle; transmitted by ticks.

East Coast Fever

Theileria parva infection in cattle; severe disease with high mortality, primarily in Africa.

Vector for East Coast Fever

Ticks of the genus Rhipicephalus, especially Rhipicephalus appendiculatus.

Animals affected by East Coast Fever

Domestic cattle (bovids) principally in Africa; other bovids can be affected.