Block 3 Flashcards
(171 cards)
Definitive Host (DH)
a host in which the parasite develops to mature stage
Intermediate Host (IH)
a host in which a parasite develops to the infective stage of the DH
Paratenic Host (PH)
a host not necessary for the development of the parasite (enhances the chance that the parasite life cycle will be complete)
• biological vector
o host in which a protozoan parasite develops through either asexual or sexual multiplication
o transmits parasite via
mouth parts after biting a DH
feces deposited on DH as it is feeding
Infection
when endoparasites infect the host INTERNALLY
infestation
when ectoparasites attach to OR occupy the host
Self-limiting Infections
Development of species or strain specific immunity
- Parasite is eliminated
- Protection from subsequent infection
Prepatent Period (PPP)
Time from infection to when eggs, cysts, and larvae appear in body fluids or excretions from the DH.
Spirocerca lupi
o esophageal worm
o FH: dogs, wolves, lions, (L3); IH: dung beetles (egg with L1) ; PH: chickens, birds and lizards
o Site: stomach to esophagus, migrating though the thoracic aorta possibly leaving lesions.
o Size: adults, pink/red 8cm. eggs small+elongated 30-35 um
Toxocara canis
o common: roundworm, ascarid
o FH: dogs ZOONOSIS ; PH: rodents
o Modes of infection: per os (eggs L2), transmammary (L3), transplacental (prenatal)(L3)
o Site: Small intestine
o Size: large white 10-15cm. eggs dark brown, round 85x75 um
Toxocara cati
o common name: common round worm/ascarid
o FH: cats PH: rodents
o Modes of infection: transmammary, per os (egg L2), paretenic hosts.
o Site: small intestine
o Size: large, white 4-10cm. eggs 60x80um round and thick shelled
Toxascaris leonia
). Eggs reach infective stage in about a week. Eggs hatch in the stomach and L enter the mucosa of small intestine (develop and molt then return to lumen of the intestine to mature). If eggs are ingested by rodents, they hatch and encyst as infective arrested larva (no placental or mammary gland transmission. Prepatent period is 2-21/2 months!
Ancylostoma caninum
o common name: hookworm
o FH: dogs, foxes; PH:rodents
o modes of infection: percutaneous, per os, paratenic hosts, transplacental, transmammary. (L3)
o Site: small intestine
Diphyllobothrium and Spirpmetra (Diphyllobthriidae)
- Copepods as first intermediate host
- Dog eats fish, amphibian, or reptile as a second intermediate host
- Eggs contain first stage larva = Oncosphere
- Second larva = Proceroid, in the body cavity or tissue of the first intermediate host.
- Third larva = Plerocercoid, in the second intermediate host
- Definitive Host = ingested the plerocercoids (aquatic food chain)
- - Most digested but left the scolex and the neck
Treatment: Praziquantel
Taenia Identification
- 10-100 cm in length
- Non-retractable rostellum with two rows of hooks (hooks use for firm attachment in theDigestive Tract
- Rectangular segments
Taenia Life Cycle
- Definitive Host = Gravid segments
- Eggs = Onchospheres,
- Ingestion of the intermediate host, the eggs hatch to give hexacanth embryo (spines on the surface)
- Hexacanth embryo migrates to the liver and both of the skeletal and cardiac muscle
- Second-stage larva infective to the definitive host (must eat the immediate host/rabbits)
- Scolex attaches to the small intestine and begins to bud off segments
- Second stage larva (found in the intermediate host) can include:
1. Cysticerus (Single bladder with one scolices, T. hydratigena)
2. Strobilocercus (elongated segment in the intermediate host, infection of a long time, T. taeniaformis = feline)
3. Coenurus (Single bladder with many scolices, T. serialis)
4. Hydatid (Formed by Echinococcus it can be either unilocular or alveolar) - Cysts (juvenile) is more infective stage than adults
Taenia hydratigena
Mammal host needed for the intermediate host of Cysticercosis. Taenia hydratigena (canine), the infective stage is the cysticercus migrates through the liver and encysts
Traumatic hepatitis
(condemnation of infected livers by meat inspectors)
Taenia ovis
Canine, Cysticerus infects the cardiac and skeletal muscles of sheep
Taenia pisiformis
Cysticerus is found in the liver and the peritoneal cavity of rabbits
Taenia saginata
Human, cysticerus found in the striated muscles of cattle, no hooks Eating beef, because it has no hooks, the human being cannot act like intermediate host)
Taenia solium
Human, people become infected by eating undercooked pork containing cysticerci (containing ones’ fingers with the infected feces)
Person feces containing eggs that can reach the mouth (lapse in personal hygiene)
Taenia taeniaformis
Strobilocercus larva of the cat (definitive host)
Taenia multiceps:
Sheep, goats, cattle causes coenurosis (intermediate host because of present of conurosis)
Cysts invade cranial cavity
Neurological Signs (Blindness, incoordination, walking in circles)
Many canids (definitive host)