A Brief Review of Ticks and Tick-Borne Diseases

Billy MacDonald ...with a little radiology

Ticks • Class Arachnida – closely related to mites

Ticks • • Class Arachnida – closely related to mites obligate blood-feeding ectoparasites – vectors

Ticks of Veterinary Importance •

Ixodidae

sclerotized dorsal shield – “hard ticks” •

Argasidae

unsclerotized – “soft ticks”

Ticks of Veterinary Importance • •

Ixodidae

sclerotized dorsal shield – “hard ticks” sexually dimorphic – – females larger male scutum covers dorsum • •

Argasidae

unsclerotized – “soft ticks” little sexual dimorphism

Ticks of Veterinary Importance • • • •

Ixodidae

primarily off host – “sit-and-wait” mate on host require days to complete engorgement live outdoors • • • •

Argasidae

live in close proximity to host mate off host require mins - hrs to feed and feed repeatedly live in dwelling/sleeping places of hosts

Tick Pathogenesis • anemia – heavy infestations

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

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

Tick Pathogenesis • • • • anemia dermatosis paralysis vector-borne diseases – viral, bacterial, and protozoal

Tick-borne Viral Diseases • Colorado tick fever rodents Dermacentor human

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

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

Tick-borne Rickettsial Diseases •

Rickettsia rickettsii

RMSF rabbits, rodents Dermacentor dogs, humans

Tick-borne Rickettsial Diseases • •

Rickettsia rickettsii

Anaplasma sp.

bovine anaplasmosis: cattle Dermacentor canine anaplasmosis: rodents, ruminants, dogs Ixodes

Tick-borne Rickettsial Diseases • • •

Rickettsia rickettsii

Anaplasma sp.

Ehrlichia sp.

canine ehrlichiosis dogs, white-tail deer Rhipicephalus

Tick-borne Rickettsial Diseases • • •

Rickettsia rickettsii

Anaplasma sp.

Ehrlichia sp.

obligate intracellular parasites

Tick-borne Rickettsial Diseases • • •

Rickettsia rickettsii

Anaplasma sp.

Ehrlichia sp.

obligate intracellular parasites • Coxiella burnetti...no longer grouped with Rickettsia – Q fever

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

Tick-borne Bacterial Diseases • • Borrelia sp.

Mycoplasma haemocanis

canine hemoplasmosis dogs Rhipicephalus

Tick-borne Bacterial Diseases • • • Borrelia sp.

Mycoplasma haemocanis Francisella tularensis

tularemia rabbits various ticks humans, dogs

Tick-borne Protozoal Diseases •

Hepatozoon canis

Rhipicephalus dog

Tick-borne Protozoal Diseases • •

Hepatozoon canis

Babesia sp.

bovine, canine, feline babesiosis, equine piroplasmosis

Rhipicephalus

Tick-borne Protozoal Diseases • • •

Hepatozoon canis

Babesia sp.

Cytauxzoon felis

wild felids Dermacentor cats

Lyme Disease...a closer look

Ixodes pacificus Ixodes scapularis

Ixodes sp.

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

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

diagnosis • • • clinical lab findings – 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

treatment • • antibiotic therapy – for arthritis: doxycycline, amoxicillin, azithromycin – for neurological manifestations: cefotaxime, chloramphenicol vaccines

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

dog ingests tick

dog ingests tick sporozoites in GI tract circulation striated muscle

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

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

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

Hepatozoonosis via radiology?

Periosteal proliferation on the femur, tibia, pelvis and lumbar vertebrae of a dog infected with H. canis

Hepatozoonosis via radiology?

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

Hepatozoonosis via radiology?

Periosteal proliferation on the femur of a dog infected with H. canis

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

References • • • • • • Craig, T.M. 1998. Hepatozoonosis, pp 458-465, In: Infectious Diseases of the Dog and Cat, 2 nd Edition; Craig E. Greene (Ed), W.B. Saunders, Pennsylvania.

Greiner, E.C. 2006. Diagnosis of arthropod parasites, pp 185-263, In: Veterinary Clinical Parasitology, 7 th Edition; Anne M. Zajak and Gary A. Conboy (Eds), Blackwell Publishing, Iowa.

Holman, P.J., and K.F. Snowden. 2009. Canine hepatozoonosis and babesiosis, and feline cytauxzoonosis. Vet Clin Small Anim 39: 1035-53.

Little, S.E. 2009. Vector-borne diseases, pp 240-253, In: Georgis’ Parasitology for Veterinarians, 9 th 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. 2000. Skeletal lesions of canine hepatozoonosis caused by Hepatozoon americanum. Vet Pathol 37: 225-230.

Shaw, D. and S. Ihle. 2006. Joint diseases, pp 439-450, In: Small Animal Internal Medicine; Shaw, D. and S. Ihle (Eds), Blackwell Publishing, Iowa.

Questions??