TABLE OF CONTENTS
Order Piroplasmida (Piroplasmorina)
Order Piroplasmida (Piroplasmorina) comprises a group of obligate intracellular protozoan parasites that infect the blood cells of vertebrates and are primarily transmitted by ticks. This order includes several medically and veterinary important genera, such as Babesia, Theileria, and Cytauxzoon, which are responsible for significant diseases in domestic and wild animals.
This article covers the taxonomical classification, general characteristics, and families of Order Piroplasmida, providing concise veterinary notes for students and professionals.
Taxonomical Classification
- Domain: Eukaryota
- Kingdom: Protista
- Phylum: Apicomplexa
- Class: Sporozoa
- Order: Piroplasmida (Piroplasmorina)
- Families: Babesiidae, Theileriidae
- Important Genera: Babesia, Theileria, Cytauxzoon
Piroplasms
The members of the order Piroplasmida (Piroplasmorina) are commonly referred to as piroplasms. They are blood cell parasites of vertebrates. The majority parasitize erythrocytes, while some species occur in leukocytes and other blood cells.
It is believed that these members are descendants of Plasmodium, but they are smaller than the latter. They may be pyriform, round, amoeboid, or rod-shaped, depending on the genus.
The apical complex is present in some stages of the parasites, but not all of its structures may be found. For example, Theileria has rhoptries, micronemes, and subpellicular microtubules, whereas Babesia possesses polar rings, subpellicular microtubules, and micronemes, but the conoid is absent. Therefore, piroplasms have a reduced apical complex.
These members do not form the pigment hemozoin from host cell hemoglobin. They have no flagella or cilia; hence, locomotion occurs by body flexion and gliding.
Piroplasms are heteroxenous parasites. In their life cycle, asexual reproduction occurs in the vertebrate host, while sexual reproduction occurs in the tick vector. The mode of transmission is by inoculation. They do not produce spores or oocysts.
Scientists Theobald Smith and Kilborne (1893) demonstrated that ticks were involved in the transmission of Babesia. This was the first report (a milestone in parasitology) demonstrating that arthropods were involved in the transmission of pathogenic organisms.
Families in the Order Piroplasmida
There are two families in this order:
- Babesiidae
- Theileriidae
