Order classification
The order Parasitiformes (Parasitiformes) is distinguished by a clear internal taxonomy. It comprises two main superfamilies:
- Gamasid mites (Gamasoidae).
- Ixodid ticks (Ixodoidae).
The superfamily of ixodoid ticks is of the greatest interest to medicine; it is subdivided into two important families: ixodid ticks (Ixodidae) and argasid ticks (Argasidae). Representatives of both families are active blood-sucking parasites and vectors of severe vector-borne infections.
Family Ixodid ticks (Ixodidae)
This family includes the best-known vectors that humans encounter in nature. The main representatives and the diseases they transmit are:
- Dermacentor, or pasture tick (Dermacentor pictus, Dermacentor marginatus). Transmits a spectrum of diseases: taiga (tick-borne spring-summer) encephalitis (the pathogen belongs to the family Flaviviridae), tick-borne typhus (pathogen: Rickettsia sibirica), Omsk hemorrhagic fever, and tularemia.
- Castor bean tick (Ixodes ricinus). Acts as a vector for taiga (tick-borne spring-summer) encephalitis, louping ill, Q fever, tick-borne borreliosis (Lyme disease), and tularemia.
- Taiga tick (Ixodes persulcatus). A specific vector of taiga encephalitis, tick-borne borreliosis (Lyme disease), and tularemia pathogens.
Family Argasid ticks (Argasidae)
Representatives of this family have a different biology and often inhabit shelters, burrows, and buildings.
The main representative from the perspective of medical parasitology is Ornithodoros papillipes (Ornithodoros papillipes).
This species is a specific vector of tick-borne relapsing fever (also known as tick-borne spirochetosis). The direct causative agent of this disease is spirochetes belonging to the genus Borrelia.
Briefly: answers to topical questions
What diseases are transmitted by gamasid mites?
Gamasid mites are vectors of rickettsialpox.
- Rickettsialpox is a disease caused by Rickettsia akari; the vector is gamasid mites.
- Vesicular rickettsiosis (rickettsialpox) is an urban-type rickettsiosis; the source of infection is domestic mice, and the vector is gamasid mites.
What are the morphological differences between ixodid and argasid ticks?
Morphological differences between ixodid and argasid ticks involve body shape, position of the capitulum (gnathosoma), presence of a scutum, and other anatomical structures.
| Sign | Family Ixodid ticks (Ixodidae) | Family Argasid ticks (Argasidae) |
|---|---|---|
| Body shape | Oval, narrowed anteriorly | Broad, with margins in the middle part parallel to each other |
| Mouthpart position | Terminal (at the anterior end of the body) | Displaced to the ventral side |
| Scutum | Covers the entire dorsal surface in males, and the anterior part in females | Absent in both females and males |
| Peritremes | Large, round-oval | Small |
| Integument | Yellow-brown coloration, scuta with festoons along the margin | Grayish-brown, tuberculate surface |
What developmental stages does the life cycle of ixodid ticks include?
The life cycle of ixodid ticks includes stages, with transitions between them occurring via molting.
- Egg.
- Larva.
- Nymph — one or more stages.
- Imago — adult tick, sexually mature males and females.
To memorize the "trio" of common infections for the castor bean tick and taiga tick (genus Ixodes), use the mnemonic phrase «En-Bo-Tu» — Encephalitis, Borreliosis, Tularemia.
Class and exam questions
What is the main medical significance of the order Parasitiformes?
This order includes the overwhelming majority of tick species that are vectors of pathogens causing human infectious diseases.
Which families are included in the superfamily Ixodoidea?
The superfamily Ixodoidea includes two families: Ixodidae and Argasidae.
What disease does the settlement tick transmit?
The settlement tick (Ornithodoros papillipes) transmits tick-borne relapsing fever, the causative agents of which are spirochetes of the genus Borrelia.
Which mite species transmit the tick-borne encephalitis virus?
The tick-borne (spring-summer) encephalitis virus is transmitted by ticks of the genus Dermacentor, the castor bean tick (Ixodes ricinus), and the taiga tick (Ixodes persulcatus).
What else to study on this topic
- Morphology and life cycle of ticks of the genus Dermacentor
- Characteristics of spirochetes of the genus Borrelia
- Viruses of the family Flaviviridae and the pathogenesis of encephalitis
- Causative agent of North Asian tick typhus (Rickettsia sibirica)
Master the entire topic in the "Biology" course
This is a summary. The course covers everything tested in classes and exams.
- Complete study guide on "Parasitiform Ticks" and 3,793 more pages of the subject
- Assignments and quizzes after every topic — just like in a colloquium
- AI tutor answers questions on the topic anytime
- 129 video lessons on the subject
Other topics in the "Medical Arachnoentomology" section
Free video lessons: BiologyShort lessons with study notes — no registration required.
Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.