Vector Borne Diseases in Small Animals

What is the causative agent of granulocytic ehrlichiosis?

Anaplasma phagocytophilum

What is the cell tropism of anaplasma phagocytophilum?

Granulocytes

What are the hosts for anaplasma phagocytophilum?

Variety of animals including canines and humans

Where can anaplasma phagocytophilum be found? ands what can it co-infect with do to the ixodes tick vector?

Northeastern USA, CA, WI, MN, Europe, Asia, Africa

Co-infections with Borrelia burgdorferi (lyme dz)

What type of disease is granulocytic ehrlichiosis?

Primarily acute disease causing polyarthritis, fever, lethargy, inappetence, etc

Subclinical infections possible

How to diagnose granulocytic ehrlichiosis

Difficult

± morula

± Antibody tests: IFA, ELISA, Snap 4DX

± PCR

What is your top differential?

Anaplasma phagocytophilum: Granulocytic Ehrlichiosis

What are the top 3 causative agents for monocytic ehrlichiosis?

E. canis, E. chaffeensis, E. ewingii (IMHA and ITP)

Big 3, all cross-react

What is another causative agent of monocytic ehrlichiosis that is similar to E.canis?

Neorickettsia risticii var. atypicalis: Bats, swallows natural reservoirs. snails and insect trematodes vectors

What is your top differential?

Monocytic ehrlichiosis

What is the most common causative agent of monocytic ehrlichiosis?

E. canis

World-wide, mild to severe clinical disease, acute, subclinical, and chronic

How does E. canis migrate?

Infected monocytes

Marginate and migrate into endothelial tissues

Vasculitis

Liver, spleen, bone marrow, LNs, lung, kidney, and CNS

How does the acute form of E. canis present?

1-3 weeks after infection

2-4 week duration

Most immunocompetent animals survive

How does the subclinical form of E. canis present?

Months to years

Can be cleared by some animals

How does the chronic form of E. canis present?

Often immune mediated diseases

What are acute clinical signs of E. canis?

***Anemia

***Thrombocytopenia

***Fever

Oculo-nasal discharge

Anorexia

Dyspnea

± evidence of ticks

Lymphadenopathy

Epistaxis/petechia

Weight loss

What are the subclinical signs of E. canis?

None!!

± ticks found on the body

What are the chronic clinical signs of E. canis?

LOTS!!

Azotemia/AKI/CKD, Proteinuria

Splenomegaly

Neurological signs etc

How does ehrlichia affect the kidneys?

Monitor renal values early and frequently

112% MORE likely to have CKD: SDMA, CBC/CHEM/UA

What will we see on bloodwork for ehrlichia?

Variable

Regen or non regen anemia

Thrombocytopenia

Leukopenia followed by a leukocytosis

What are some neurologic manifestations of ehrlichia?

Depression

Pain

Ataxia

Vestibular

cerebellar

Paresis

Nystagmus

Seizures

What are some opthalmologic manifestations of ehrlichia?

**Tortuous retinal vessels

Perivascular retinal infiltrates

**Retinal hemorrhage

Anterior uveitis

Exudative retinal detachment

What are the challenges to the diagnosis of ehrlichia?

False negatives

Need time to seroconvert

How to diagnose ehrlichia?

C/S, CBC, blood smear

AB tests: Snap 4DX, IFA, Serology, western immunoblot

PCR

What are the dilemmas of diagnosis ehrlichia?

Antibody tests are not diagnostic due to cross reactivity, false positives, and false negatives

When can you make a presumptive diagnosis of ehrlichia?

Clinical animal with a positive serology —> start therapy!

What is treatment for ehrlichia?

Supportive care (fluids, possible transfusion)

Antimicrobial therapy

What is the antimicrobial therapy for ehrlichia?

Doxycycline 10 mg/kg PO q 24 hrs for 28 days

Minocycline

Oxytetracycline

Monitoring after treatment ehrlichia

Antibody titers (± negative)

PCR ( 2 weeks after tx cessation, if + —> continue tx for 4 more weeks, if - —> recehck PCR in 8 weeks)

Resolution of clinical signs (thrombocytopenia, hypergamaglobulinemia)

What is the prognosis for ehrlichia?

Acute disease —> good with treatment

Chronic disease —> variable to guarded

What are additional considerations of ehrlichia?

Co-infections with bartonella, anaplasma, borrelia, and babesia

How to prevent ehrlichia?

Tick control!! especially in endemic areas

What is the causative agent of Salmon Poisoning Disease?

Neorickettsia helminthoeca, intracellular bacteria of a trematode (N. salmincola)

What is the essential intermediate host for Nanophyetus salmincola transmission cycle?

Snail

What are the clinical signs of Salmon Poisoning disease?

~7 days after ingestion of fish can be variable

Enteritis and lymphadenopathy (monocyte infiltration)

Fever

Vomiting

Diarrhea

Thrombocytopenia 90% of cases

>90% fatal (6-10 days) if not treated

What 2 things do we have to treat in Salmon disease poisoning?

Bacteria and trematode

What is the treatment and prevention of salmon disease poisoning?

Hospitalization, fluids, transfusions

Doxycycline and Fenbendazole

What is Babesiosis?

Intracellular protozoan parasite of RBC’s

Babesia canis, B. gibsoni, B. felis, B. leo most common

What are the vectors for Babesiosis?

Ixodid ticks- Haemophysalis spp.

Rhipicephalus sanguineus

Dermacentor reticulatus

Transfusion (dog bites) or transplacental

How can babesia be presented?

Variable

Peracute

Acute

Subclinical infection

Chronic

What are clinical signs of babesiosis?

Fever (uncommon in cats)

Anorexia

Lethargy

**Anemia

**Icterus (uncommon in cats)

** ± agglutination

Hemoglobinuria

Hepatosplenomegaly

Rough haircoat

What other disease do the clinical signs of babesiosis resemble?

IMHA

What are some complications of babesia infection?

Severe hemolytic anemia/hemolytic crisis

Hypotensive shock

Secondary IMHA can develop

DIC can develop

Metabolic acidosis

Renal disease

Which babesia species affects greyhounds more severely?

B. canis

Which babesia species affects pitbulls more severely?

B. gibsoni

How do you diagnose babesia?

Intraerythrocytic trophozoites on a blood smear

Giemsa, Romanowsky, Field’s, and modified Wright’s stains

IFA and serology available

PCR

How do we treat B. canis?

Imidicarb diproprionate 12% at 5-6.6 mg/kg SC once, repeated in 2-3 weeks

Pretreat with atropine or glycopyrollate to prevent SLUD

Together with clindamycin, metronidazole, and doxy triple therapy for 90 days

How do we treat B. gibsoni?

Atovaquone 13.5 mg/kg PO q8 (with a fatty meal) and azithromycin 10 mg/kg PO q24 in combination for 10 days

What is the prognosis for babesia infection?

Remain subclincially infected and can suffer relapses and act as a disease reservoir

Because of the subclincal prognosis for babesia infections what do we have to be careful of?

Splenectomy —> spleen is protecting from relapse

Dog fighting —> (blood transfusion)

Blood donation

What is the causative agent of Cytauxzoonosis?

Cytauxzoon felis, a protozoal organism

How is cytauxzoon felis transmitted?

Via the tick vector dermacentor variabilis and possibly amblyomma americanum

What is the intermediate host of cytauxzoon felis?

Bobcats

70% prevalence

When are most cases of cytauxzoonosis diagnosed?

More than 90% of cases are diagnosed between april and september

indoor and outdoor cats

What are the clinical signs of cytauxzoonosis?

Fever, lethargy, anorexia, pancytopenia, regenerative anemia

Obstruction of small vessels with schizont-laden macrophages, results in ischemia and thrombosis

How do cats typically present at end stages of cytauxzoonosis?

Dyspneic, moribund, hypothermic, neurologic

Commonly die within 5-7 days after clinical signs begin —> poor/grave prognosis, most die without treatment

How can we diagnose cytauxzoonosis?

Blood smear, FNA of spleen, LN cytology —> perform all 3 increases likelihood of finding bug

Histopath

PCR

What is your top differential?

Cytauxzoonosis

What is the treatment for cytauxzoonosis?

Heparin (minimize blood clots) at 100-300 U/kg SQ q8 hours

Imidocarb dipropionate at 2 mg/kg IM q every 2 weeks

Atovaquone and azithromycin combo therapy for 10 days with aggressive supportive care

Minimize stress

Strict tick control if survive

What type of organism is borrelia burgdorferi? (lyme dz)

Gram negative spirochetes

How is borrelia burgdorferi transmitted?

Ixodes ticks

What are uncommon clinical signs of lyme disease?

arthritis and nephritis

Do all lyme infected animals develop clinical disease?

Most don’t!

What are common clinical signs of lyme disease that get better with antimicrobial therapy?

Acute polyarthritis

Lameness

Fever

Anorexia

Regional lymphadenopathy

What is the most serious complication and least common clinical manifestation of lyme disease?

Lyme nephritis

How can we diagnose lyme disease?

Normal radiographs, CBC, CHEM

Commonly abnormal synovial fluid when acute

Non-degenerate neutrophils in multiple joints

Top differential?

Lyme disease —> non-degenerate neutrophils

What can be a difficulty with diagnosing lyme disease?

Vaccinated dogs remain seropositive for years (IFA or ELISA not good)

Western immunoblot good for differentiating infected from vaccinating but not widely available

What is a good test for diagnosing lyme disease?

C6 Peptide Assay - in Idexx 3DX and 4DX snap test

Recommended to screen all healthy dogs in endemic areas for AB and if positive to screen for proteinuria

What is the most common treatment for lyme disease?

Doxycycline 10 mg/kg PO q12 for 30 days —> good for co-infections too

What are some other treatments for lyme disease besides doxy?

Amoxicillin, Azithromycin, Cefovecin, ± pain control

In acute cases clinical improvement should be seen within 24-48 hrs

What is the treatment for a lyme disease patient with lyme nephritis/glomerulonephropathy?

Worsening polyarthritis, glomerulonephritis, and cardiac abnormalities

Immunosuppressive drugs (Mycophenolate ± others)

Check IRIS for updates

What is the best prevention for lyme disease?

Tick control!!

Should you vaccinate for lyme disease?

In endemic areas, booster vaccine

Don’t vaccinate if proteinuric or very sick

Worsens lyme nephritis

What type of organism is Rickettsia rickettsii?

Gram negative obligate intracellular parasite

What ticks are correlated with rocky mountain spotted fever?

Dermacentor and Rhipicephalus

Where does rickettsia rickettsii replicate?

Endothelial cells of capillaries after 2-14 day incubation

Causes extravasation of fluid and blood into extravascular space

What is the subclinical presentation of RMSF in dogs?

May not show signs of disease and recover quickly

What is the acute presentation of RMSF in dogs?

Loss of appetite, fever, depression, edema

Neurological signs

Anemia, drop of platelets and rise of liver enzymes

What is the prognosis for RMSF?

Subclinical or acute

Get it and get better or die

What are the clinical signs of RMSF?

Fever

Petechia and ecchymosis

Testicular inflammation

Scleral injection

Retinal hemorrhage

Anterior uveitis

Mucopurulent oculo-nasal discharge

Neurological signs

Polyarthritis

Lymphadenopathy

What tick species is mainly responsible for transmission of RMSF in the eastern USA?

American dog tick (Dermacentor variabilis)

What tick species is mainly responsible for transmission of RMSF in the western USA?

The wood tick (Dermacentor andersoni) and Rhipicephalus

What is a concern for RMSF transmission?

Climate change causes ticks to move locations and prevalence increasing

What would we see on the bloodwork of a patient with RMSF?

Leukopenia followed by leukocytosis

Thrombocytopenia

Can be anemic

can progress to DIC

How to diagnose RMSF?

Presumptive —> History, C/S, CBC, response to therapy

Paired serum samples —> high IgG titer suggestive of exposure within the last tick season, positive IgM titer indicates a more recent exposure

PCR

Goal to do both PCR and serology!

What is the treatment for RMSF?

**Doxycycline 5-10 mg/kg q12 for 21 days

Enrofloxacin, tetracycline, chloramphenicol if < 6 mo old

Can be fatal if untreated

Prognosis good with treatment < 5 % die

What is the causative agent of Bartonella?

Bartonella vinsonii subsp berkhoffii and B. henselae

Over 20 sp and subsp

What are involved in the transmission of Bartonella?

Fleas and ticks

Rhipicephalus

Sand flys and lice

How does bartonella invade the body?

Invades erythrocytes and endothelial cells

0% dogs

7.4% cats

What is cat scratch disease?

Bartonella

B. henselae via bite/scratch

Where does cat scratch disease come from?

B. henselae in flea dirt —> bartonella can live for 9 days in flea dirt

What is the common species causative agent of canine bartonellosis?

Bartonella vinsonii subsp berkhoffii

What are the common clinical signs of canine bartonellosis?

Splenomegaly common

Endocarditis

Granulomatous lymphadenitis, rhinitis, panniculitis

Hepatitis

Fever

Intermittent lameness

CNS signs

Hypoglycemia in young dogs

What happens with chronic bartonells infections?

Can be well tolerated for years

Manifest when stressed, at parturition, or if co-infected

What is the diagnosis for bartonellosis?

Blood or tissue culture (difficult)

**PCR —> BAPGM at NCSU

Serology > 1:64 titer

What is the treatment for bartonella?

Doxycycline/fluoroquinolone combo tx 4-6 weeks

Can gain resistance really fast!!! new reports all resistant

Rifampin if unresponsive

Aminoglycoside if unresponsive —> in house ICU w frequent renal monitoring (aminoglycoside can be nephrotoxic)

What are the clinical signs of hepatozoonosis?

Fever

Weight loss

Muscle atrophy

Mucopurulent ocular dc

Generalized stiff gait and hindlimb paresis

Extensive periosteal bone proliferation

Top differential?

Hepatozoonosis

How is hepatozoon canis transmitted?

Transmission by INGESTING brown dog tick (rhipicephalus sanguineus)