1	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
2	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 Area’s of South & Central Texas Hotspots in Bexar County Classic Signs May Not Be Common Signs
3	Canine Schistosomiasis: Intro Causative Agent – Heterobilharzia americana Life-cycle & Transmission Definitive Hosts Intermediate Hosts Reproduction Signs & Findings DDx, Definitive Dx & Tx
4	Heterobilharzia americana NonHermaphroditic DiGenic Flukes 2 Parasitic Stages 2 Free Living Stages Definitive Hosts Raccoons o Nutria Dogs o Bobcats Wild Canids o Rabbits Adults Infest Mesenteric Veins Female Resides in Gynecophoric Canal Of The Male Sexual Reproduction Phase
5	Canine Schisto: Life Cycle
6	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 àMore Inflammation Results à Less Successful Shedding
7	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
8	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
9	Canine Schisto: Intermediate Hosts Pseudosuccinea (Lymnaea) columella
10	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
11	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
12	Canine Schisto: Geography Disease Range Limited By Environment Tolerance Of Lymnaeid Snails
13	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
14	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
15	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 à Restart Cycle
16	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 à CPLD à Fibrosis Other Organ “Target” Inflammation à Fibrosis Spleen n Pancreas n Stomach n Other
17	Canine Schisto: Clinical Signs
18	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
19	Canine Schisto: Clin Path
20	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
21	Canine Schisto: Pathomechanisms HyperGlobulinemia Chronic Inflammation HypoAlbuminemia PLE o PLN Malnutrition HyperCalcemia Granulomatous Inflam. PTH Related Protein Anemia Blood Loss from GIT Anemia of Inflammatory Disease Azotemia PreRenal/Dehydration Renal Failure/HyperCa
22	Canine Schisto: Differential Dx Problem Based for Each Patient Large Bowel Diarrhea Infiltrative/Neoplastic 1^o Inflammatory 2^o Inflammatory Infectious – Fungal, Bacterial, other Weight Loss Decreased Intake Nutrient Loss (PLE, PLN…) HyperMetabolism – Heart, Neoplasia, Infection, etc
23	Canine Schisto: Differential Dx HyperCalcemia HyperPTH o Addison’s Renal Failure o Neoplasia HyperVit. D Granulomatous Inflammation HyperGlobulinemia Neoplasia o Rickettsial Fungal o Viral Other Chronic Inflammation Elevated Liver Enz. Other Hepatitis o Toxicity Other GI’itis o Trauma Pancreatitis o Neoplasia Etc. HypoAlbuminemia Liver Failure o Starvation Protein Losing Syndrome PLN, PLE, PLD Hemorrhage
24	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
25	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
26	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
27	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
28	Canine Schisto: Case Review YOUR HELP IS NEEDED If You Diagnose any Canine Heterobilharzia americana in the Next 6 Months o 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
29	CANINE SCHISTOSOMIASIS: ?? QUESTIONS ?? Jonathan M. Fradkin, DVM, MS, Diplomate, ACVIM Specialty of Small Animal Internal Medicine San Antonio Veterinary Referral Specialists www.SAVRS.com