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Tick-Borne Protozoa Flashcards

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1
Q

Hepatozoon infects more than _______ species worldwide

A

300 vertebrates

- amphibians, reptiles, birds, marsupials, mammals

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2
Q

Canine Hepatozoon spp

A

Hepatozoon americanum
- ACH: american canine hepatozoonosis
Hepatozoon canis

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3
Q

Hepatozoon americanum hosts

A

Southern US, South and Central America

  • DH: tick vector (Amblyomma maculatum)
  • IH: canids
  • PH: rodents, rabbits
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4
Q

How do dogs become infected with H. americanum?

A

My ingesting the tick, or by ingesting affected paratenic hosts
- tick does NOT bite the dog!

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5
Q

H. americanum has a(n) _______ life cycle

A

Indirect

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6
Q

What is a requirement for a tick-bite infection?

A

Sporozoites must be in the salivary glands of the tick

- with H. americanum they are in the body of the tick

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7
Q

H. americanum infective stages

A
  • tick vector (DH): ingests canine leukocytes with gamont
  • dog (IH): ingests tick with oocysts or PH with cystozoites
  • -> transplacental not confirmed
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8
Q

H. americanum sites of infection

A
  • tick vector (DH): mature oocysts in hemocoel
  • dog (IH): gamonts in leukocytes, meronts in skeletal muscle and cardiac tissue
  • PH: cystozoites in skeletal and cardiac muscle, kidney, lung
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9
Q

American canine hepatozoonosis - pathology

A
  • neutrophilic leukocystosis (moderate anemia)
  • periosteal bone proliferation (primarily long bones of younger dogs)
  • tissue lesions (onion skin cyst): pyogranulomas occur when merozoites come out of meronts
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10
Q

ACH - clinical signs

A

Occur 4-5 weeks post-infection

  • fever
  • weakness
  • chronic weight loss
  • depression
  • muscle atrophy, pain, gait abnormalities
  • mucopurulent ocular discharge
  • frequent relapses, death 12-24 mos post-infection if untreated*
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11
Q

ACH - presumptive diagnosis

A
  • profound neutrophilia
  • periosteal bone lesions
  • clinical signs, history
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12
Q

ACH - definitive diagnosis

A
  • gamonts in leukocytes
  • muscle biopsy (most likely to find cysts, most invasive)
  • PCR
  • ELISA
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13
Q

Where are gamonts found in ACH?

A

Rarely found, occurrence in less than 0.1% of WBC

- look at buffy coat

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14
Q

Pyogranulomas

A

Rupture of cyst with mature meront –> merozoites released, inflammatory cell infiltration

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15
Q

ACH treatment

A

No effective treatment in eliminating parasites!
Acute cases:
- ponazuril (2 weeks), or combination therapy for 2 weeks plus supportive therapy
Chronic cases:
- decoquinate daily for 2 years
Relapses can occur, sylvatic cycle is efficient

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16
Q

What drugs comprise combination therapy for ACH?

A
  • Trimethoprim-sulfadiazine
  • Clindamycin
  • Pyrimethamine
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17
Q

ACH control

A

Reduce risk of exposure

- tick prevention

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18
Q

Hepatozoon canis

A

Old World only

  • usually subclinical, genetic diversity
  • DH: tick vector (Rhipicephalus sanguineus)
  • IH: canids
  • PH: rodents
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19
Q

How does H. canis differ from H. americanum?

A
  • higher number of WBCs infected
  • meronts are in lymph nodes, bone marrow, spleen
  • meronts look like wheel spoke
  • dogs asymptomatic unless immunocompromised
  • good prognosis with treatment (Imidocarb)
  • PH has monozoic cyst
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20
Q

How does hematology differ with H. canis?

A

Gamonts are commonly found (1005)

- neutrophilia is rare

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21
Q

Histopathology of H. canis

A

Hepatitis, splenitis, pneumonia

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22
Q

Hepatozoon spp. in cats

A

Life cycle poorly understood

  • cysts with meronts in muscle, cardiac tissue
  • 1% of WBC infected (hard to detect)
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23
Q

Cytauxzoon felis

A

North America (southeastern, south central, mid atlantic)

  • DH: tick vector –> Amblyomma americanum, and to a lesser extent Dermacentor variabilis
  • IH: felids
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24
Q

Who is the reservoir for C. felis?

A

Bobcat (Lynx rufus)

- asymptomatic

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25
C. felis has a(n) _______ life cycle
Indirect
26
C. felis infective stages
- tick vector (DH): merozoite from infected (feline) RBCs | - cat (IH): sporozoite from infected tick or from blood transfusion
27
C. felis sites of infection
Cat (IH) - merozoites in RBCs - schizonts in macrophages associated with endothelium of lung, liver, lymph node, spleen, bone marrow - multisystemic clinical signs
28
Cytauxzoonosis pathology
- leukopenia, thrombocytopenia, non-regenerative anemia, elevated liver enzymes - progressive illness: multiple organ failure
29
What are the 2 phases of cytauxzoonosis?
- leukocytic (schizont): primary cause of severe clinical disease - erythrocytic (merozoites): RBC hemolysis
30
Cytauxzoonosis clinical signs
- lethargy/depression - icterus - high fever then subnormal - splenomegaly, hepatomegaly - death within 1st week after clinical signs
31
What happens to survivors of cytauxzoonosis?
They become carriers | - rare, 1-2 week recovery
32
When do clinical signs occur with cytauxzoonosis?
1-3 weeks post-infection | - several weeks after tick is gone
33
Cytauxzoonosis diagnosis
- clinical signs - history - merozoites in stained blood smears (round to oval ring, or safety pin in RBC)
34
Schizonts of cytauxzoonosis occur in ______
Macrophages - bone marrow, lymph node, spleen aspirates - impression smears, biopsy material
35
Cytauxzoonosis treatment
No efficacious treatment, poor prognosis - combo of atovaquone + azithromycin (60% survival) - imidocarb dipropionate following pretreatment with atropine or glycopyrrolate
36
Cytauxzoonosis control
- reduce risk exposure - routine on animal tick control - remove ticks immediately!! - -> 2-3 day window?
37
Do cats become infected with cytauxzoon by tick bits or tick ingestion?
Tick bites
38
Babesia hosts
- DH: tick vector (wide range of tick species) - IH: wild and domestic animals (canids), humans - -> piroplasms in RBCs
39
How does infected tick transmit sporozoites in Babesia?
Transmit sporozoites to vertebrate host via tick saliva | - sporozoites invade RBCs --> develop and asexually replicate --> merozoites
40
How does the tick become infected with Babesia?
By biting infected vertebrate - ingests RBCS - gamogony --> sporogony --> sporozoites in salivary glands
41
Babesia canis vogeli
Enzootic in US (esp south) - greyhound kennels DH: tick vector - Rhipicephalus sanguineus, D. variabilis
42
Babesia gibsoni
US - seen in American Staffordshire and pit bull terriers (mainly mechanical via dog fighting) DH: tick vector - R. sanguineus throughout the world, not confirmed in US
43
Babesia conradae
No breed predilection, California | - DH: tick vector is currently unknown
44
Canine babesiosis: transmission to canids in US
Bite from infected tick vector - Rhipicephalus sanguineus - B. canis vogeli - B. gibsoni (outside US) - B conradae: tick unknown
45
Canine babesiosis direct
Animal to animal - dog fights (wounds): B. gibsoni - iatrogenic: B. canis, B. gibsoni - transfusions: B. canis, B. gibsoni - transplacental: B. canis, B. gibsoni?
46
Canine babesiosis - transmission to DH
Blood meal from dog or transovarial transmission
47
Canine babesiosis - pathology
- hemolytic anemia - thrombocytopenia - hemoglobinuria - hemoglobinemia
48
____ Babesia is more pathogenic than _____ Babesia spp
Small; large - B gibsoni > B canis vogeli - co-infections complicate disease
49
Canine babesiosis - clinical signs
Can be subclinical - lethargy, fever, pallor, jaundice - splenomegaly
50
Canine babesiosis diagnosis
- blood smears: fresh, capillary source - antibody testing: negative in acute infection, detects exposure not infection - PCR: useful in early infection, interpret with caution
51
Babesia gibsoni characteristics
Small babesia - single - pleiomorphic: oval, ring form, maltese cross
52
Babesia canis vogeli characteristics
Large babesia - pyriform - often in pairs
53
Babesia conradae is similar to _______
B. gibsoni
54
Canine babesiosis treatment
Reduce parasitemia! - small babesia is more difficult to treat - reservoirs for parasite transmission --> chronic carriers/recrudesce (+ blood donors)
55
Canine babesiosis control
- decrease tick exposure - routine on animal tick control - remove ticks
56
Bovine babesiosis
DH: tick vectors - Rhipicephalus microplus - Rhipicephalus annulatus IH: cattle, other ruminants
57
Is bovine babesiosis eradicated?
Yes, eradicated from US in 1943 via Tick Fever Eradication Program - reportable!
58
Bovine Babesiosis pathology
Disease characterized by fever, hemolytic anemia and severe multisystemic signs - piriform or round parasites seen in RBCs on blood or brain smears
59
Equine piroplasmosis
Babesia caballi and Theileria equi - DH: tick vector (dermacentor, hyalomma, rhipicephalus) - IH: equids (mules, donkeys, horses, zebras) - --> iatrogenic and vertical transmission is possible
60
Is equine piroplasmosis reportable?
Yes | - eradicated in US in 1980, until outbreak in 2008
61
Equine piroplasmosis clinical signs
Theileria equi more severe --> infects both WBC and RBC - acute: fever, inappetence, labored breathing, anemia, jaundice, hemoglobinuria, hemorrhage on conjunctiva, abortion - chronic: subtle signs of chronic infection, splenomegaly
62
Equine piroplasmosis diagnosis
Challenging - antibody testing - PCR
63
Are parasites detectible with chronic Theileria equi?
No | - acute stage you see small pyriform bodies (maltese cross)
64
Feline babesiosis
Worldwide occurance - IH: panthers, cougars - -> no cases in domestic cats - DH: tick species (unknown)
65
Feline babesiosis disease in domestic cats outside US
Anemia, depression, weight loss, GI signs, cardiac pathology - 15-20% mortality, relapses
66
Human babesiosis in US
Babesia microti - DH: tick vector (Ixodes scapularis) - IH: rodent (reservoir), humans are accidental
67
Human babesiosis clinical signs
Asymptomatic or fever, chills, hemolytic anemia, myalgias, hepatomegaly - incubation 1-4 weeks - transfusion transmission

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