Indirectly Transmitted Coccidia and Tick-Borne Diseases

Comprehensive vocabulary flashcards covering indirectly transmitted coccidia, tick-borne protozoa, and rickettsial diseases in various livestock and companion animals based on Professor T. Hove's lecture notes.

Tachyzoites

Rapidly replicating merozoites that cause massive tissue destruction during the acute phase of infection when host immunity is low.

Bradyzoites

Slowly replicating merozoites found within tissue cysts that predominate when host immunity is competent, leading to asymptomatic or latent infections.

Definitive Host (DH)

The host in which gametogony, zygote, and oocyst formation occur at the intestinal level; for Toxoplasma gondii, these are felids.

Intermediate Host (IH)

The host in which extra-intestinal infection occurs and asexual replication (schizogony/merogony) takes place in various tissues.

Toxoplasma gondii

An indirectly transmitted coccidian in the Family Sarcocystidae that infects any nucleated cell of warm-blooded animals, including humans.

Neospora caninum

A parasite closely related to T. gondii, first described in 1989, where canids serve as the definitive hosts and cattle are common intermediate hosts affected by abortion.

Sarcocysts

Thick-walled bradyzoite cysts belonging to the genus Sarcocystis, found in the heart, skeletal muscle, or neural tissue of the intermediate host.

Besnoitiosis

An emerging disease characterized by a chronic ‘elephant skin appearance’ caused by Besnoitia spp. replicating in fibroblasts and endothelial cells.

Piroplasms

Intraerythrocytic pleomorphic merozoites of the genus Babesia, categorized as large or small based on whether their size is greater or less than the red blood cell radius ($3.00\,\mu m$).

Babesia bigemina

The cause of Redwater in Zimbabwe; a large Babesia species where paired piroplasms are positioned at an acute angle to one another.

Babesia bovis

The cause of cerebral babesiosis; a small Babesia species where paired piroplasms are generally annular and positioned at an obtuse angle to one another.

Schizogony/Merogony

The asexual multiplication phase of apicomplexan protozoa, such as Theileria or Babesia, occurring within host cells like lymphocytes or erythrocytes.

January Disease

A syndrome of theileriosis in Zimbabwe caused by cattle-derived Theileria parva bovis, primarily transmitted by Rhipicephalus appendiculatus.

Corridor Disease

A severe form of theileriosis caused by buffalo-derived Theileria parva transmitted to cattle via Rhipicephalus ticks.

Koch’s Blue Bodies

Schizonts of Theileria parva found in the cytoplasm of lymphocytes or appearing 'free' in stained lymph node aspirate smears.

Gallsickness

The common name for bovine anaplasmosis, a tick-borne rickettsial infection caused by Anaplasma marginale leading to fever and progressive anaemia.

Heartwater

A tick-borne rickettsial disease caused by Ehrlichia ruminantium, named for the characteristic hydropericardium (effusion into the heart sac) found in affected ruminants.

Morula

A cluster or colony of rickettsial elementary bodies found within the cytoplasm of host cells, such as vascular endothelial cells or monocytes.

Tropical Canine Pancytopaenia

A synonym for canine ehrlichiosis caused by Ehrlichia canis, which replicates within the cytoplasm of monocytes.

Feline Infectious Anaemia

A condition caused by Mycoplasma haemofelis (Haemobartonella felis) in stressed or immunocompromised cats, resulting in severe haemolytic anaemia and jaundice.

Aegyptianellosis

A tick-transmitted rickettsiosis of domestic and wild birds caused by Aegyptianella pullorum, which infects erythrocytes.

Avian Borreliosis

A disease of poultry caused by the spirochaete Borrelia anserina, typically transmitted transovarially and trans-stadially by Argas ticks.

Exoerythrocytic Schizonts

Parasite stages that develop in tissue cells, such as liver cells, before invading red blood cells, as seen in Plasmodium (avian malaria).

Haemozoin

A yellow to black malaria pigment found within intra-erythrocytic organisms or tissues of birds infected with Plasmodium.

Synergism

The pharmacological phenomenon where the combined action of two or more drugs, such as those used for canine babesiosis, is greater than the sum of their separate effects.