Exam 2 - more infectious diseases Flashcards
What is the etiology of plague?
Yersinia pestis
What is the reservoir and transmission for plague?
Flea-rodent-flea reservoir
Transmission by ingestion of infected prey / flea bites
Cats highly susceptible
What clinical signs are consistent with plague?
- Bubonic (rodent ingestion)
pyrexia, dehydration, lymphadenopathy, hyperesthesia - Septicemic
hematogenous spread to organs (esp lungs)
fatal within 1-2 days - Pneumonic
How is plague diagnosed?
Sample: Needle aspirates from affected tissues
Gram stain - monomorphic population of gram neg organisms (safety pin morphology)
Serology - 4x increase to confirm
REPORTABLE: submit culture samples and fixed slides
How is plague treated?
Isolate 48-72 hours and handle carefully (zoonotic)
Aminoglycosides (eg. amikacin) DOA
-chloramphenicol if CNS affected
-doxy/fluoroquinolones if aminoglycosides contraindicated
What is the etiology for leptospirosis?
Leptospira interogans sensu lato
What is the reservoir for leptospirosis? How is it transmitted?
Rats/other rodents/water sources
Viable for months in soil saturated by urine
Seen in late summer/early fall
Transmission by urine (and others)
What is the pathogenesis for leptospirosis?
Leptospires penetrate intact mms / abraded, scratched, water-softened skin.
7 day incubation and spread
*Renal colonization (renal tubular epithelial cells) - shedding in urine by 2 weeks post-infection
*Hepatic injury
What clinical signs are associated with leptospirosis infection?
Acute kidney disease
Hematemesis, hematochezia, epistaxis, petechial hemorrhages
Lung injury (‘lepto lungs’) - vasculitis with fluid exudate/pulmonary hemorrhage
How is leptospirosis diagnosed?
*Microscopic agglutination test (MAT)
Lab findings - leukocytosis, thrombocytopenia, azotemia, liver elevation
Imagine - renomegaly, interstitial to nodular alveolar densities
How is leptospirosis treated?
Parenteral ampicillin/amoxicillin (1-2 weeks)
+Doxycycline (PO for 2-3 weeks) to eliminate carrier state
What is the etiology for lyme disease?
Borrelia burgdorferi sensu stricto
Motile spirochete
How is lyme disease transmitted? What time of year does it occur?
Ixodes scapularis
Late spring/early summer infection of new hosts
What is the pathogenesis of lyme disease?
Lives in tick midgut - during blood meal OspC upregulated - movement to salivary glands - skin injection (~48 hours of attachment
Infects synovial tissue - joint fluid inflammation
What is lyme nephritis? What signs are seen? How is it treated?
Glomerulonephritis with immune complex deposition
Leads to protein loss in urine (UPC >5)
Most common in young labs and goldens
Tx as other kidney dz + immune suppression
(methylpred, ACE inhibitors, low dose aspirin, renal diet)
What clinical signs are associated with lyme disease?
Develop 2-5 months after tick bite
Fever, inappetance, polyarthritis (shifting leg lameness), generalized lymphadenopathy
How is lyme disease diagnosed?
4DX or QuantC6 (detects C6 Ab production)
How is lyme disease treated?
Doxycycline for 1 month (should respond in 1-2 days)
amoxicillin alternatively
What abnormality is found in ALL rickettsial diseases?
Thrombocytopenia
How are ALL rickettsial diseases treated?
Doxycycline
How are rickettsial diseases diagnosed? Which is the exception?
4DX
Except R. ricketsii (no in house test)
What is the etiology of CME? Which cells does it infect? What is its vector?
Ehrlichia canis
Monocytes/macros
Rhipicephalus sanguineous
What is the pathogenesis of CME?
Incubation 8-20 days
Acute phase: replication within reticuloendothelial tissues, vasculitis, PLT dysfunction, thrombocytopenia
Subclinical phase: sequestration of E. canis in spleen
Chronic phase (not all dogs): pancytopenia, death d/t hemorrhage and SBIs
What clinical signs are consistent with CME?
Acute: bleeding, neuro signs, hyphema, dyspnea, lameness
Chronic: +edema, PU/PD, SBIs
In which rickettsial diseases can morulae be seen?
CGE (E. ewingii) and CGA (A. phago)
Cannot be distinguished!
What are the negative prognostic indicators of CME?
severe leukopenia
severe anemia
increased aPTT
What are the gold standard screening test and confirmatory tests for CME?
IFA (rarely done, 4DX easier)
Confirmation by immunoblot (at least 21 days post-infection) or PCR (4-10 days post-infection)
What is the etiology of CGE? Which cells does it infect? What is its vector?
Ehrlichia ewingii
Neutrophils
Amblyomma americanum
What is the pathogenesis and CS of CGE?
3-4 week incubation
Acute disease only - fever, polyarthritis, thrombocytopenia
What is the etiology of CGA? Which cells does it infect? What is its vector?
Anaplasma phagocytophilum
Neutrophils
Ixodes
What is the pathogenesis and CS of CGA?
Incubation 1-2 weeks
Most dogs not clinical!
Self-limiting febrile illness
What is the etiology of canine cyclic thrombocytopenia? Which cells does it infect? What is its vector?
Anaplasma platys
Platelets
Rhipicephalus sanguineous
When is canine cyclic thrombocytopenia suspected?
Thrombocytopenia with NO other signs
What is the etiology of RMSF? Which cells does it infect? What is its vector?
Rickettsia rickettsii
Endothelial cells
Rhipicephalus / Amblyomma / Dermacenter
Which rickettsial disease is reportable in humans, and in some places dogs?
RMSF
What is the pathogenesis of RMSF?
Transfer of organism in HOURS
Epithelial cell infection - vasculitis - clotting/thrombosis - DIC
What CS are consistent with RMSF?
Fever Retinal hemorrhages Neutrophilic polyarthritis Respiratory / GI signs Edema, petechiation
Describe the life cycle of toxoplasma.
- Infection by ingestion of sporozoites/bradyzoites or transplacental/translactational of tachyzoites
- Rapidly dividing tachyzoites disseminate throughout host (intracellular)
- Bradyzoites encyst in tissues (chronic infection)
- Cat excretes oocysts with sporozoites (2 weeks)
What clinical signs are associated with toxoplasmosis?
Adult cats - self-limiting diarrhea
Kittens/immunosuppressed - disseminated disease
Dogs - neuromuscular dz or disseminated dz (puppies, rapidly fatal)
How is toxoplasma diagnosed?
Serology + CS (many animals are seropositive)
How is toxoplasma treated?
Clindamycin x4 weeks
TMS if CNS infection
Topical steroids for uveitis
Describe the life cycle/pathogenesis of neospora.
Canine ingests feces/undercooked meat (transplacental also)
Acute infection (tachyzoites)
Encysted bradyzoites in muscle and neuro tissue
Sporulated oocysts excreted
What clinical signs are associated with neospora infection?
Puppies (<6 months)
-Ascending paralysis, typically alert/mentally appropriate
Adult dogs
-multifocal CNS involvement
How is neospora diagnosed?
Serology
How is neospora treated?
Clindamycin x4-8 weeks
Treat ALL pups in a litter
What are the etiologies of babesia?
B. canis - dogs, large piroplasm
B. gibsoni - dogs, small piroplasm
B. felis - cats, Africa only
Describe the transmission and pathogenesis of babesia.
Ixodes tick feeds 1-3 days
Sporozoites in tick saliva injected
Attach to RBC and endocytosed
Intracellular replication and RBC rupture
What clinical signs are associated with babesia infection?
Hemolytic anemia (many dogs subclinical) -lethargy, depression, pallor, icterus, hemoglobinuria
DDx for babesia infection?
IMHA
Zinc toxicity
PK/PFK deficiencies
How is babesiosis diagnosed?
PCR
How is babesiosis treated?
B. canis - Imidocarb (SLUD side effects)
B. gibsoni - Azithromycin
Describe the transmission and pathogenesis of cytauxzoon.
Felid host
Transmitted by Amblyomma ticks
Phase 1: tissue phase
-Merozoites inoculated via ticks, invade mononuclear cells, infected macros occlude vessels, multi-organ failure
Phase 2: erythrocytic phase
-Merozoites infect RBCs (piroplasm), destruction and phagocytosis of RBCs
What clinical signs are associated with cytauxzoon?
Weakness, anorexia, fever
Icterus, pallor
Dyspnea
CNS signs
RAPID course (<7 days) and high fatality
How is cytauxzoon diagnosed?
PCR
How is cytauxzoon treated? What is the survival rate?
Atovaquone + azithromycin
60% survival
Which species of hepatozoon is found in America? How is it transmitted?
H. americanum
Amblyomma maculatum - ticks ingested by dogs
Describe the transmission and pathogenesis of hepatozoon.
Dog ingests tick
Sporozoites released and penetrate gut
Invade mononuclear cells - organ dissemination
Infection of skeletal and cardiac muscle
Pyogranulomatous myositis +/- periosteal reaction (puppies)
What clinical signs are associated with hepatozoon infection?
Fever, progressive weight loss with good appetite
Hyperesthesia and pain, rear limb ataxia
Ocular discharge
PU/PD
How is hepatozoon diagnosed?
Histo, PCR, serology
Marked leukocytosis and neutrophilia
What ddx should be considered for hepatozoon-associated periosteal bony changes in puppies?
Hypertrophic osteodystrophy
How is hepatozoon treated?
TMS + clindamycin + pyrimethane (x2 weeks)
Docoquinate (x2 years) to decrease relapses
*NO tx eliminates tissue phase
Describe the life cycle and pathogenesis of leishmaniasis
Promastigotes in female sandfly gut injected into host
Amastigotes infect macrophages
Dissemination to hemolymphatics
Sandfly ingests amastigotes in blood
What clinical presentations are associated with leishmaniasis?
- May clear organisms and become resistant
- Asymptomatic carriers
- Progressive immunosuppression (T-lymphoid) and immune-complex deposition
lymphadenopathy, splenomegaly
generalized skin lesions, NON pruritic
polyarthritis, GN, vasculitis, uveitis
How is leishmania diagnosed?
PCR
How is leishmania treated and prevented?
Pentavalent antimonials (eg. allopurinol) *relapse very common, often tx lifelong K9 advantix repels sandflies
What is the etiology of Chagas disease?
Trypanosoma cruzi
Describe the pathogenesis of Chagas/trypanosoma
Kissing bug defecates into bite wound
Trypomastigote (blood form) enters host and disseminates hematogenously
Infects macrophages (amastigote)
Migration to cardiac and skeletal muscle
2-3 weeks, trypomastigotes rupture from host cells
Progressive myocardial degeneration (DCM)
What clinical signs are associated with Chagas/trypanosoma?
Acute disease: myocarditis (R sided failure with ascites/pleural effusion)
Chronic disease: DCM
How is trypanosoma infection diagnosed?
Cytology, serology, PCR
How is Chagas/trypanosoma treated?
Anti-parasitics (eg nifurtimox / benzinidazole)
*Does not stop DCM!
Poor prognosis, 1-5 years
Which systemic mycosis is reportable in Minnesota?
Blastomycosis
Which species does blastomyces infect?
Dogs and humans
Describe the pathogenesis of blastomyces
Saprophytic mycelial form in environment - makes spores
Inhalation of spores
Body temp triggers transformation into yeast
Incubation 1-3 months
Asexual repro in body and dissemination via vessels and lymphatics
What are the common sites of infection for blastomyces, and which CS are expected?
Lungs (primary), eyes, skin, bone
Pyrexia, anorexia, weight loss, lymphadenopathy
Mycotic pneumonia
How is blastomycosis diagnosed?
Rads are variable -Diffuse interstitial miliary (classic) -Alveolar (ddx aspiration pneumonia) -Mass pattern (ddx neoplasia) Cytology: broad-based budding Antigen testing (urine sample)
How is blastomycosis treated?
Itraconazole (microencapsulated) for 6 months
NSAIDS and gluocorticoids for first few days
What is the prognosis for blastomycosis and what are the poor prognostic indicators?
25% mortality, 20% relapse within first year PPI: -severe pulmonary involvement -CNS involvement -more than 3 body systems involved
Where is histoplasma found? What species does it infect?
Warm, humid environments (SE)
Humans, dogs, cats
Describe the pathogenesis of histoplasma
Saprophytic mycelial form Spore formed - ingested or inhaled Incubation ~2 weeks Yeast conversion in body Phagocytized by mononuclear cells Disseminates via vessels and lymphatics
What are the common sites of infection for histoplasma, and which CS are expected?
Lungs or intestine (primary), spleen, liver, LNs, eyes, BM, adrenals Subclinical infection common Pyrexia, anorexia, weight loss Mycotic pneumonia Diarrhea (rare in cats)
How is histoplasma diagnosed?
Diffuse interstitial miliary lung pattern
Intestines may be thickened, friable, hemorrhagic
Cytology - small, round yeast found intracellular (macros and neutrophils)
How is histoplasma treated?
Itraconazole +/- amphotericin B 4-6 months
Steroids NOT recommended
What is the prognosis for histoplasma and what are the poor prognostic indicators?
Good for localized respiratory
Poor to fair for disseminated
PPI: BNS, ocular, or bone involvement
Where is coccidioidomycosis found? Which species does it infect?
SW states (valley fever), rainfall followed by draught Dogs more often than cats
Describe the pathogenesis of coccidioidomycosis.
Saprophytic mycelial form
Infective spores (arthoconidia) inhaled)
Incubation 1-3 weeks
Conversion to spherule, releases endospores
What clinical signs are consistent with coccidioidomycosis?
Most cases subclinical or mild respiratory
Pregnancy/immunosuppression/massive exposure leads to severe pulmonary infection
-pulmonary abscesses, fibrosis, bronchiectasis
-hilar lymphadenopathy
-osteomyelitis (ddx osteosarcoma)
Skin lesions common in cats (relatively immune)
How is coccidioidomycosis diagnosed?
Tube precipitation test (IgM) - 2-3 weeks post-exp
Complement fixation Abs (IgG) - 4-6 weeks post-exp
How is coccidioidomycosis treated?
Any azole for 12 months (frequent relapses off therapy, may need lifelong tx)
What is the prognosis for coccidioidomycosis?
Good for local respiratory
Poor to fair for disseminated
Where is cryptococcus found? What species does it infect?
Ubiquitous and worldwide, common in bird droppings
Cats more than dogs
What clinical signs are consistent with cryptococcosis?
Nasal/facial deformities in cats (ddx neoplasia)
CNS signs most common in dogs
How is cryptococcus diagnosed?
Cytology - thick capsule
How is cryptococcus treated? How is tx monitored?
Itraconazole
- fluconazole for CNS dz
- amphotericin B if unresponsive
Ag agglutination test (serum or CSF) for monitoring
-tx until titer negative (6-18 months) or forever if FeLV+
What is the prognosis for cryptococcus? What is a favorable indicator?
Good to excellent, except if CNS dz
Decrease in titer 10x over 2 months = favorable
What breed develops SYSTEMIC aspergillosis?
German Shepherds
What is the pathogenesis for systemic aspergillosis?
Inhaled then hematogenously spread
Branching fungal hyphae
Multiorgan infiltrate
How is systemic aspergillosis diagnosed?
Cytology
Serum and urine Ag test
How is systemic aspergillosis treated? What is the prognosis?
Azoles, amphotericin B
Grave prognosis - no cure, 0-25 months
