Jonathan M' Fradkin, DVM, MS, Diplomate, ACVIM

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SCHISTOSOMIASIS A ZEBRA IN OUR NEIGHBORHOOD

• Jonathan M. Fradkin, DVM, MS, Diplomate, ACVIM
• Specialty of Small Animal Internal Medicine
• San Antonio Veterinary Referral Specialists
• www.SAVRS.com

Presented VMABC Seminar, October 20005
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Canine Schistosomiasis Why?

• Canine Blood Flukes Reported Rare to Uncommon
• Why Spend Time Discussing It
• Rare to Uncommon May Mean Under-Diagnosed
• Fairly Common in Some Areas of South Central
  Texas
• Hotspots in Bexar County
• Classic Signs May Not Be Common Signs

Identification of More Cases will Allow Better
Description of the Disease
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Canine Schistosomiasis Intro

• Causative Agent Heterobilharzia americana
• Life-cycle Transmission
• Definitive Hosts
• Intermediate Hosts
• Reproduction
• Signs Findings
• DDx, Definitive Dx Tx

H..americana 2-4 mm long Male Female
Adults Image from U Penn Vet. Parasit. Dept.
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Heterobilharzia americana

• NonHermaphroditic DiGenic Flukes
• 2 Parasitic Stages
• 2 Free Living Stages
• Definitive Hosts
• Raccoons ? Nutria
• Dogs ? Bobcats
• Wild Canids ? Rabbits
• Adults Infest Mesenteric Veins
• Female Resides in Gynecophoric Canal Of The Male
• Sexual Reproduction Phase

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Canine Schisto Life Cycle
Fluke 1st Parasitic Stage of Mammal
Miricidia 1st Free Living
Cercariae 2nd Free Living
Sporocysts 2nd Parasitic Stage of Snail
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Canine Schisto Egg Miracidia

• Released from Adult Female Into Mesenteric Venous
  Bloodstream
• Final Oviposition in Enteric Venules
• Aberrant Ova May Disseminate Widely via
  Hematogenous Spread
• More Chronic Egg Presence ?More Inflammation
  Results ?
• Less Successful Shedding

Illustration from Slaughter et al, Compendium,
1988
Image from NCSU CVM, Dr. Flowers
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Canine Schisto Miracidia

• Eggs Hatch About 30 Minutes After Release of
  Stool in Moist Environment
• Ciliated Miracidia Live Free Prior to Infection
  of Lymnaeid Snail Intermediate Host

Image from NCSU CVM Dr. Flowers
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Canine Schisto Intermediate Hosts

• Lymnaeid Snails
• Small 1 cm Long
• Right Handed
• Dark or Black in Life
• Turn White in Death
• Activity Dependent on Environmental Conditions
• Pseudosuccinea (Lymnaea) columella
• Lymnaea (Fossaria) cubensis

• Amphibious Snails
• Semi-Aquatic
• Snail Range Disease Spread

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Canine Schisto Intermediate Hosts
4 mm

• Pseudosuccinea (Lymnaea) columella

• Lymnaea (Fossaria) cubensis

• Most Active and Reproductive in Cool Moist
  Weather
• October to May in Brazos Surrounding Counties
  
• Probably Similar in Bexar County South Texas

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Canine Schisto Intermediate Hosts

• Motile Miracidia Penetrate the Snail
• Differentiate Into Sporocysts
• Individual Mother Sporocysts Produce Daughter
  Sporocysts
• Asexual Reproduction Produces Numerous
  Fork-Tail Motile Cercaria
• Free Living Cercaria Emerge From Snail

Sporocyst Stage Asexual Reproduction Takes
Minimum 25-30 Days
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Canine Schisto Host Infection

• Dog Steps In Wet Puddle or Contaminated Grass
• Cercaria Penetrate the Skin Tail Breaks Off
• Immature Schistosome Migrate to Mesenteric
  Vessels Mature
• 40 day Migration/Maturation

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Canine Schisto Geography

• Disease Range Limited By Environment Tolerance Of
  Lymnaeid Snails

R
1
R
R
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Canine Schisto Classic Case

• The Classic Case Description in the Literature
  is Either that of the First Case Presentation OR
  that of the Most Common Clinical Presentation,
  Rarely Both. Curtis Dewey
• ( possibly taken from A.D. DeLahunta)
• Dermatitis, Chronic Hemorrhagic Diarrhea, Weight
  Loss to Cachexia
• Hyperglobulinemia, Hypoalbuminemia, Anemia,
  Eosinophilia

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Canine Schisto Mammalian Parasite

• Cercaria Penetrate Skin Transform to Immature
  Form Schistosomulum
• Schistosomulum Migrates to Lungs
• Penetrates Tissue to Pulmonary Capillaries
• Inflammation And Cough
• Carried from Pulmonary Capillaries to Systemic
  Circulation to Portal Circulation
• Adults Localize in Mesenteric Veins
• Adapt Host Ag - Little Inflammatory Stimulus

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Canine Schisto Mammalian Parasite

• Miracidial Ova Released into Circulation
• Adhere to Embed in Venule-Capillary Walls of
  Intestinal Tract
• Enter Wall of Intestinal Tract
• Some Transit Thru To Lumen
• Some Localize, Incite Granulomatous Inflammation,
  Enteritis
• Less Likely to Survive to be Shed
• Eggs Successfully Expelled Into Intestine Lumen
  are Shed in Feces ? Restart Cycle

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Canine Schisto Mammalian Parasite

• Eggs Not Successfully Shed to Lumen
• Localized Inflammatory Response- Enteritis
• Eggs which Never Adhere in Intestinal Venules
  Aberrant Flow
• Carried Past Intestine By Circulatory System
• Seed Out in Portal System and Liver
• Incite Granulomatous Hepatitis ? CPLD ? Fibrosis
• Other Organ Target Inflammation ? Fibrosis
• Spleen ? Pancreas ? Stomach ? Other

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Canine Schisto Clinical Signs
Voluminous, mucoid, tenesmus, urgency,
flatulence Intermittent soft stool
Oculonasal Discharge
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Canine Schisto Clinical Signs

• Most Common Clinical Signs Were
• Weight Loss
• Nonspecific Lethargy or Depression
• Classically Reported Hematochezia Only Seen in
  only 2 of Most Recent 7 Cases Reviewed

Are Different Signs More Common? Different Signs
Commonly Result in Referral?
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Canine Schisto Clin Path
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Canine Schisto Pathomechanisms

• Pruritis Penetration of Cercaria Causes
  Dermatitis (similar to Human Disease)?
• Reported in Early Papers not Since
• Cough Migration of Immature Schistosomula
  Through Lungs Causes Inflammation? Aberrant Egg
  Deposition In Pulmonary Vessels Causes
  Inflammation?
• Reported in Early Papers not Since
• Diarrhea (any type) Inflammatory Enteritis from
  Ova Transit to Lumen
• Inflammation from Granulomas - Trapped Ova

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Canine Schisto Pathomechanisms

• HyperGlobulinemia
• Chronic Inflammation
• HypoAlbuminemia
• PLE ? PLN
• Malnutrition
• HyperCalcemia
• Granulomatous Inflam.
• PTH Related Protein

• Anemia
• Blood Loss from GIT
• Anemia of Inflammatory Disease
• Azotemia
• PreRenal/Dehydration
• Renal Failure/HyperCa

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Canine Schisto Differential Dx

• Problem Based for Each Patient
• Large Bowel Diarrhea
• Infiltrative/Neoplastic
• 1o Inflammatory
• 2o Inflammatory
• Infectious Fungal, Bacterial, other
• Weight Loss
• Decreased Intake
• Nutrient Loss (PLE, PLN)
• HyperMetabolism Heart, Neoplasia, Infection,
  etc

Image courtesy NCSU CVM, Dr. Flowers
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Canine Schisto Differential Dx

• HyperCalcemia
• HyperPTH ? Addisons
• Renal Failure ? Neoplasia
• HyperVit. D
• Granulomatous Inflammation
• HyperGlobulinemia
• Neoplasia ? Rickettsial
• Fungal ? Viral
• Other Chronic Inflammation

• Elevated Liver Enz.
• Other Hepatitis ? Toxicity
• Other GIitis ? Trauma
• Pancreatitis ? Neoplasia
• Etc.
• HypoAlbuminemia
• Liver Failure ? Starvation
• Protein Losing Syndrome
• PLN, PLE, PLD
• Hemorrhage

MUST ADDRESS PROBLEM LIST AND DIFFERENTIALS
POTENTIALLY MULTIFACTORIAL DISEASE
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Canine Schisto Diagnosis

• Classic Suspect If
• Typical Signs
• Access to Water (Pond, Stream, Tank)
• Water Loving Breed
• Current
• Include In Differentials List if Appropriate
• Routine Testing if on Differentials List

• Diagnostic Testing
• Direct Fecal Exam
• Fecal Sedimentation
• Miracidia Hatching
• TVMDL Request
• Fecal Sedimentation R/O Heterobilharzia - 10
  Dr. Ronald will Run All Appropriate Tests
• (From Above List)
• Biopsy Histopathology
• ELISA CAA test
• Not Readily Available

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Canine Schisto Treatment

• Sample 15 kg Dog
• Fenbendazole 40/mg/kg qDaily x 10 d
• Panacur Liquid, 100 mg/ml x 10 6ml Doses 5.44
• Panacur C Granules, 10 x 600 mg Doses 11.20
• Praziquantel 20 mg/kg TID x 1 day (300 mg/dose)
• 9 Droncit K9 Pills (2.52/tab) x 3 doses
  68.04
• 2 Human Capsules (600mg) Recompounded to
  Chewables divided into 3 doses 50-60
• 4.5 Drontal Plus Medium tabs (5.98/tab) x 3
  doses (5.98/t) 80.73

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Canine Schisto Treatment

• Sample 15 kg Dog
• Praziquantel 25 mg/kg BID x 3 days or TID for 2
  days (375 mg/dose)
• 11 Droncit K9 Pills x 6 doses 136.08
• 4 Human Praziquantel Capsules Recompounded
  divided into 6 doses 110-120
• 5.5 Drontal Plus Medium tabs x 6 doses 197.34
• Drontal Plus at Label Dose Listed on VIN
• Dose Recommendation Unclear If Increase Pill
  Count to Meet Individual Mg/Kg Dose
  Recommendations Cost Much Higher

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Heterobilharzia Zoonosis

• "Swamp Itch" or Swimmer's Itch
• People can be Infested with Cercaria
• Penetrate Skin Then Die
• Elicit Hypersensitivity Reaction
• Signs Generally Worse with Subsequent Exposure

Image from NCSU CVM, Dr. Flowers
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Canine Schisto Case Review

• YOUR HELP IS NEEDED
• If You Diagnose any Canine Heterobilharzia
  americana
• in the Next 6 Months ? In the Last Year
• Please Notify Me Obtain Authorization from
  Client for Case to be Reviewed
• With Assistance, More Cases and More Real World
  Cases can Be Reviewed
• Additional Information Should Help Us Our
  Patients

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CANINE SCHISTOSOMIASIS ?? QUESTIONS ??

• Jonathan M. Fradkin, DVM, MS, Diplomate, ACVIM
• Specialty of Small Animal Internal Medicine
• San Antonio Veterinary Referral Specialists
• www.SAVRS.com