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Infective entities in Apicomplexans
Sporozoites
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Develops within the oocyst and contains sporozoites
sporocyst
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Motile stage formed from asexual reproduction within the host cell
Merozoite
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Merozoite with slow growth & replication
bradyzoites
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Merozoite with rapid growth & replication
tachyzoite
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These circulate in the blood and are vector-born
Hemoprotozoans
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Hemoprotozoan life cycle
- 1. Sporozoites excyst from sporocyst and invade cells
- 2. Under asexual reproduction forming merozoites
- 3. merozoites leave cells and invade new cells
- 4. eventually form gametocytes
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Microgametocytes are
male
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macrogametocytes are
female
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Apicomplexan characteristics
- obligatory intracellular
- multiply through strict sequence of asexual & sexual reproduction
- have direct or indirect life cycles
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Amblyomma americanum is definitive host
Cytauxzoon felis
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Cytauxzoon felis transmission
- Adult tick transmits sporozoite to intermediate host
- Asexual reproduction in monocytes (1-2 rounds)
- Monocytes rupture, releasing merozoites
- Merozoites infect RBCs - ring stage
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Causes obstruction of vessels, splenic congestion, and pulmonary edema/congestion
Cytauxzoon felis
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Sudden onset anemia, icterus, bile stasis
Cytauxzoon felis
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Cytauxzoon felis is distributed in
south-central US
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Seasonality of Cytauxzoon felis
Peaks in spring- early summer, declines over summer, increases again in the fall
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Best tissue aspirates for Cytauxzoon felis
Spleen/Lung
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Definitive host for Hepatozoon americanum
Amblyomma maculatum
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Hepatozoon americanum direct or indirect life cycle?
Indirect
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Intermediate host for Hepatozoon americanum
canids
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Life cycle of Hepatozoon americanum
- 1. Ticks ingest gamonts (gametocytes)
- 2. Sexual reproduction forming oocysts
- 3. Canid eats tick
- 4. Sporozoites enter host's tissue
- 5. Asexual reproduction to merozoites
- 6. eventually enter leukocytes
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Paratenic host for Hepatozoon americanum
small mammals
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What happens when small mammals eat a tick infected with Hepatozoon americanum?
It enters cells and forms a cystozoite
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This causes periosteal proliferation of long bones
Hepatozoon americanum
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Causes nonregenerative anemia with profound neutrophillic leukocytosis
Hepatozoon americanum
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Lameness, muscle atrophy, painful
mucopurulent ocular discharge
Hepatozoon americanum
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Pathoneumonic onion skin lesion on muscle biopsy
Hepatozoon americanum
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Definitive host(s) for Hepatozoon canis
- Rhipcephalus sanguineus
- Amblyomma sp
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Infects neutrophils and causes mild disease or might be clinically normal
Hepatozoon canis
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Is a blood smear adequate for Hepatozoon americanum?
Not unless the organism is circulating in the blood
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Is a blood smear adequate for Hepatozoon canis?
Yes, it infects all of the neutrophils
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Definitive host for Babesia
Ixodid ticks
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Life Cycle of Babesia spp
- 1. Sporozoites transmitted through blood feeding
- 2. Invade RBCs, undergo asexual reproduction
- 3. Merozoite invades new blood cells
- 4. Form gamonts which are ingested by tick
- 5. Form zygote within tick which forms oocyst
- 6. Sporozoites develop within oocyst
- 7. Sporozoites go to salivary gland of tick
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Transmission of Babesia spp
- Ticks
- Direct animal to animal - dog fights
- transplacental
- transfer of blood
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Transmitted by Rhipcephalus sanguineus
Babesia canis vogeli
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Babesia spp - Puppies are more severely affected than adults
Babesia canis vogeli
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Babesia very common in greyhounds
Babesia canis vogeli
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Babesia spp very common in fighting dogs
Babesia gibsoni
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Causes sick dog syndrome
Canine Babesiosis
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Clinical signs of Canine Babesiosis
- hemolytic anemia, ischemic tissue injury
- hypotensive shock syndrome
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Clinical findings for Canine Babesiosis
- Thrombocytopenia (decreased platelets)
- anemia
- hyperglobinuria
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Detection method of choice for Canine Babesiosis
PCR
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Treatment outcomes for Canine Babesiosis
- Complete cure
- subclinical carrier
- partial recovery (anemia remains)
- relapse
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Bovine Babesiosis species of importance
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Transmission of bovine babesiosis
- Rhipicephalus annulatus
- Rhipicephalus microplus
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Is B. bovis or B. bigemina more pathogenic?
B. bovis
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Babesia caballi & Babesia equi transmit
Equine piroplasmosis
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Transmission with B. caballi
Transovarial
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Transmission with B. equi
Transstadial
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Ticks involved in Equine Piroplasmosis
- Amblyomma cajennense
- Dermacentor nitens
- Dermacentor variabilis
- R. microplus
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Transmission outside of Texas is
iatrogenic
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Test of choice for Equine piroplasmosis
Serology
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