1. A Brief Review of Ticks and Tick-Borne Diseases
A Brief Review of Ticks and Tick-Borne Diseases ...with a little radiology
Billy MacDonald

2. Ticks
Class Arachnida
closely related to mites

3. Ticks Class Arachnida obligate blood-feeding ectoparasites
closely related to mites
obligate blood-feeding ectoparasites
vectors

4. Ticks of Veterinary Importance
Ixodidae
Argasidae
sclerotized dorsal shield
“hard ticks”
unsclerotized
“soft ticks”

5. Ticks of Veterinary Importance
Ixodidae
Argasidae
sclerotized dorsal shield
“hard ticks”
sexually dimorphic
females larger
male scutum covers dorsum
unsclerotized
“soft ticks”
little sexual dimorphism

6. Ticks of Veterinary Importance
Ixodidae
Argasidae
primarily off host
“sit-and-wait”
mate on host
require days to complete engorgement
live outdoors
live in close proximity to host
mate off host
require mins - hrs to feed and feed repeatedly
live in dwelling/sleeping places of hosts

7. Tick Pathogenesis
anemia
heavy infestations

8. Tick Pathogenesis anemia dermatosis
inflammation, swelling, itching, ulceration from tick’s saliva and mouthparts

9. Tick Pathogenesis anemia dermatosis paralysis
neurotoxin present in saliva of some species
Dermacentor sp.

10. Tick Pathogenesis anemia dermatosis paralysis vector-borne diseases
viral, bacterial, and protozoal

11. Tick-borne Viral Diseases
Colorado tick fever
rodents Dermacentor human

12. Tick-borne Viral Diseases
Colorado tick fever
rodents Dermacentor human
tick-borne encephalitis
humans, cattle, horses, dogs

13. Tick-borne Viral Diseases
Colorado tick fever
rodents Dermacentor human
tick-borne encephalitis
humans, cattle, horses, dogs
African swine fever
wild suids Ornithodorus pig

14. Tick-borne Rickettsial Diseases
Rickettsia rickettsii
RMSF
rabbits, rodents Dermacentor dogs, humans

15. Tick-borne Rickettsial Diseases
Rickettsia rickettsii
Anaplasma sp.
bovine anaplasmosis: cattle Dermacentor
canine anaplasmosis: rodents, ruminants, dogs Ixodes

16. Tick-borne Rickettsial Diseases
Rickettsia rickettsii
Anaplasma sp.
Ehrlichia sp.
canine ehrlichiosis
dogs, white-tail deer Rhipicephalus

17. Tick-borne Rickettsial Diseases
Rickettsia rickettsii
Anaplasma sp.
Ehrlichia sp.
obligate intracellular parasites

18. Tick-borne Rickettsial Diseases
Rickettsia rickettsii
Anaplasma sp.
Ehrlichia sp.
Coxiella burnetti...no longer grouped with Rickettsia
Q fever
obligate intracellular parasites

19. Tick-borne Bacterial Diseases
Borrelia sp.
Lyme disease
bovine borreliosis
avian spirochetosis

20. Tick-borne Bacterial Diseases
Borrelia sp.
Mycoplasma haemocanis
canine hemoplasmosis
dogs Rhipicephalus

21. Tick-borne Bacterial Diseases
Borrelia sp.
Mycoplasma haemocanis
Francisella tularensis
tularemia
rabbits various ticks humans, dogs

22. Tick-borne Protozoal Diseases
Hepatozoon canis
Rhipicephalus dog

23. Tick-borne Protozoal Diseases
Hepatozoon canis
Babesia sp.
bovine, canine, feline babesiosis, equine piroplasmosis
Rhipicephalus

24. Tick-borne Protozoal Diseases
Hepatozoon canis
Babesia sp.
Cytauxzoon felis
wild felids Dermacentor cats

25. Lyme Disease...a closer look
Ixodes pacificus
Ixodes scapularis

26. Lyme Disease...a closer look
etiologic agent: Borrelia burgdorferi
white-footed deer mouse
Ixodes sp.
humans, dogs, cattle, horses

27. clinical signs...in dogs fever, anorexia, malaise lymphadenomegaly
shifting leg lameness
sudden onset
painful articular swelling
*nonerosive polyarthritis
pathologic changes in the joints are progressive
rarely: renal disease (glomerulonephritis), neurological disease

28. diagnosis clinical lab findings serology Isolation
inflammatory changes in synovial fluid
serology
ELISA detects antibodies to B. burgdorferi
Isolation
culture is most definitive...but also most difficult due to limited number of organisms present
PCR

29. treatment antibiotic therapy vaccines
for arthritis: doxycycline, amoxicillin, azithromycin
for neurological manifestations: cefotaxime, chloramphenicol
vaccines

30. Hepatozoonosis...a closer look
etiologic agent:
Hepatozoon canis...an intracellular parasite in various tissues
transmitted via ingestion of infected tick (Rhipicephalus sanguineous)

31. dog ingests tick

32. dog ingests tick
sporozoites in GI tract
circulation
striated muscle

33. dog ingests tick
sporozoites in GI tract
circulation
striated muscle
“onion skin” cyst in skeletal muscle

34. dog ingests tick
sporozoites in GI tract
circulation
striated muscle
“onion skin” cyst in skeletal muscle
asexual reprod. (merogony)
merozoites released into
surrounding tissues
severe inflamm. reaction
neutrophilic granuloma formation
~ 4 weeks...parasite infected neutrophils
(gamonts) present in peripheral blood

35. Hepatozoonosis...a closer look
etiologic agent:
Hepatozoon canis...an intracellular parasite in various tissues
transmitted via ingestion of infected tick (Rhipicephalus sanguineous)
clinical signs:
fever, anorexia, weight loss, diarrhea...wax and wane
diagnosis:
CBC, Biochem.: non-specific inflammation
UA: +/- proteinuria
muscle biopsy for definitive diagnosis
treatment:
symptomatic: NSAIDs

36. Hepatozoonosis via radiology?
Periosteal proliferation on the femur, tibia, pelvis and
lumbar vertebrae of a dog infected with H. canis

37. Hepatozoonosis via radiology?
Periosteal proliferation on the femur, tibia, pelvis and
lumbar vertebrae of a dog infected with H. canis
...lesions resemble HO

38. Hepatozoonosis via radiology?
Periosteal proliferation on the femur
of a dog infected with H. canis

39. Hepatozoonosis via Bone Scan
Skeletal lesions in a dog infected with H. canis (americanum)

40. References
Craig, T.M Hepatozoonosis, pp , In: Infectious Diseases of the Dog and Cat, 2nd Edition; Craig E. Greene (Ed), W.B. Saunders, Pennsylvania.
Greiner, E.C Diagnosis of arthropod parasites, pp , In: Veterinary Clinical Parasitology, 7th Edition; Anne M. Zajak and Gary A. Conboy (Eds), Blackwell Publishing, Iowa.
Holman, P.J., and K.F. Snowden Canine hepatozoonosis and babesiosis, and feline cytauxzoonosis. Vet Clin Small Anim 39:
Little, S.E Vector-borne diseases, pp , In: Georgis’ Parasitology for Veterinarians, 9th Edition; Dwight D. Bowman (Ed), Saunders Publishing, Missouri.
Panciera, R.J., Mathew, J.S., Ewing, S.A., Cummings, C.A., Drost, W.T., and A.A. Kocan Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Vet Pathol 37:
Shaw, D. and S. Ihle Joint diseases, pp , In: Small Animal Internal Medicine; Shaw, D. and S. Ihle (Eds), Blackwell Publishing, Iowa.

41. Questions??