Tick-Borne Protozoa Flashcards
Hepatozoon infects more than _______ species worldwide
300 vertebrates
- amphibians, reptiles, birds, marsupials, mammals
Canine Hepatozoon spp
Hepatozoon americanum
- ACH: american canine hepatozoonosis
Hepatozoon canis
Hepatozoon americanum hosts
Southern US, South and Central America
- DH: tick vector (Amblyomma maculatum)
- IH: canids
- PH: rodents, rabbits
How do dogs become infected with H. americanum?
My ingesting the tick, or by ingesting affected paratenic hosts
- tick does NOT bite the dog!
H. americanum has a(n) _______ life cycle
Indirect
What is a requirement for a tick-bite infection?
Sporozoites must be in the salivary glands of the tick
- with H. americanum they are in the body of the tick
H. americanum infective stages
- tick vector (DH): ingests canine leukocytes with gamont
- dog (IH): ingests tick with oocysts or PH with cystozoites
- -> transplacental not confirmed
H. americanum sites of infection
- 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
American canine hepatozoonosis - pathology
- 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
ACH - clinical signs
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*
ACH - presumptive diagnosis
- profound neutrophilia
- periosteal bone lesions
- clinical signs, history
ACH - definitive diagnosis
- gamonts in leukocytes
- muscle biopsy (most likely to find cysts, most invasive)
- PCR
- ELISA
Where are gamonts found in ACH?
Rarely found, occurrence in less than 0.1% of WBC
- look at buffy coat
Pyogranulomas
Rupture of cyst with mature meront –> merozoites released, inflammatory cell infiltration
ACH treatment
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
What drugs comprise combination therapy for ACH?
- Trimethoprim-sulfadiazine
- Clindamycin
- Pyrimethamine
ACH control
Reduce risk of exposure
- tick prevention
Hepatozoon canis
Old World only
- usually subclinical, genetic diversity
- DH: tick vector (Rhipicephalus sanguineus)
- IH: canids
- PH: rodents
How does H. canis differ from H. americanum?
- 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
How does hematology differ with H. canis?
Gamonts are commonly found (1005)
- neutrophilia is rare
Histopathology of H. canis
Hepatitis, splenitis, pneumonia
Hepatozoon spp. in cats
Life cycle poorly understood
- cysts with meronts in muscle, cardiac tissue
- 1% of WBC infected (hard to detect)
Cytauxzoon felis
North America (southeastern, south central, mid atlantic)
- DH: tick vector –> Amblyomma americanum, and to a lesser extent Dermacentor variabilis
- IH: felids
Who is the reservoir for C. felis?
Bobcat (Lynx rufus)
- asymptomatic
C. felis has a(n) _______ life cycle
Indirect
C. felis infective stages
- tick vector (DH): merozoite from infected (feline) RBCs
- cat (IH): sporozoite from infected tick or from blood transfusion
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
Cytauxzoonosis pathology
- leukopenia, thrombocytopenia, non-regenerative anemia, elevated liver enzymes
- progressive illness: multiple organ failure
What are the 2 phases of cytauxzoonosis?
- leukocytic (schizont): primary cause of severe clinical disease
- erythrocytic (merozoites): RBC hemolysis
Cytauxzoonosis clinical signs
- lethargy/depression
- icterus
- high fever then subnormal
- splenomegaly, hepatomegaly
- death within 1st week after clinical signs
What happens to survivors of cytauxzoonosis?
They become carriers
- rare, 1-2 week recovery
When do clinical signs occur with cytauxzoonosis?
1-3 weeks post-infection
- several weeks after tick is gone
Cytauxzoonosis diagnosis
- clinical signs
- history
- merozoites in stained blood smears (round to oval ring, or safety pin in RBC)
Schizonts of cytauxzoonosis occur in ______
Macrophages
- bone marrow, lymph node, spleen aspirates
- impression smears, biopsy material
Cytauxzoonosis treatment
No efficacious treatment, poor prognosis
- combo of atovaquone + azithromycin (60% survival)
- imidocarb dipropionate following pretreatment with atropine or glycopyrrolate
Cytauxzoonosis control
- reduce risk exposure
- routine on animal tick control
- remove ticks immediately!!
- -> 2-3 day window?
Do cats become infected with cytauxzoon by tick bits or tick ingestion?
Tick bites
Babesia hosts
- DH: tick vector (wide range of tick species)
- IH: wild and domestic animals (canids), humans
- -> piroplasms in RBCs
How does infected tick transmit sporozoites in Babesia?
Transmit sporozoites to vertebrate host via tick saliva
- sporozoites invade RBCs –> develop and asexually replicate –> merozoites
How does the tick become infected with Babesia?
By biting infected vertebrate
- ingests RBCS
- gamogony –> sporogony –> sporozoites in salivary glands
Babesia canis vogeli
Enzootic in US (esp south)
- greyhound kennels
DH: tick vector
- Rhipicephalus sanguineus, D. variabilis
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
Babesia conradae
No breed predilection, California
- DH: tick vector is currently unknown
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
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?
Canine babesiosis - transmission to DH
Blood meal from dog or transovarial transmission
Canine babesiosis - pathology
- hemolytic anemia
- thrombocytopenia
- hemoglobinuria
- hemoglobinemia
____ Babesia is more pathogenic than _____ Babesia spp
Small; large
- B gibsoni > B canis vogeli
- co-infections complicate disease
Canine babesiosis - clinical signs
Can be subclinical
- lethargy, fever, pallor, jaundice
- splenomegaly
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
Babesia gibsoni characteristics
Small babesia
- single
- pleiomorphic: oval, ring form, maltese cross
Babesia canis vogeli characteristics
Large babesia
- pyriform
- often in pairs
Babesia conradae is similar to _______
B. gibsoni
Canine babesiosis treatment
Reduce parasitemia!
- small babesia is more difficult to treat
- reservoirs for parasite transmission –> chronic carriers/recrudesce (+ blood donors)
Canine babesiosis control
- decrease tick exposure
- routine on animal tick control
- remove ticks
Bovine babesiosis
DH: tick vectors
- Rhipicephalus microplus
- Rhipicephalus annulatus
IH: cattle, other ruminants
Is bovine babesiosis eradicated?
Yes, eradicated from US in 1943 via Tick Fever Eradication Program
- reportable!
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
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
Is equine piroplasmosis reportable?
Yes
- eradicated in US in 1980, until outbreak in 2008
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
Equine piroplasmosis diagnosis
Challenging
- antibody testing
- PCR
Are parasites detectible with chronic Theileria equi?
No
- acute stage you see small pyriform bodies (maltese cross)
Feline babesiosis
Worldwide occurance
- IH: panthers, cougars
- -> no cases in domestic cats
- DH: tick species (unknown)
Feline babesiosis disease in domestic cats outside US
Anemia, depression, weight loss, GI signs, cardiac pathology
- 15-20% mortality, relapses
Human babesiosis in US
Babesia microti
- DH: tick vector (Ixodes scapularis)
- IH: rodent (reservoir), humans are accidental
Human babesiosis clinical signs
Asymptomatic or fever, chills, hemolytic anemia, myalgias, hepatomegaly
- incubation 1-4 weeks
- transfusion transmission
