Pythiosis General

Pythium insidiosum

  • Kingdom Stramenipila
  • Oomycete “aquatic fungus”
  • Hyphal elements similar to Fungi
  • Primarily an infectious agent of plants


  • Phycomycosis
  • Florida Horse Leeches
  • Swamp Cancer

Species Infected by Pythium insidiosum

  • Canine Australia, Brazil, Korea, USA and Venezuela
  • Equine Australia, Brazil, Colombia, Costa Rica, New Zealand, New Guinea, USA and Venezuela Feline USA
  • Bovine Brazil, USA and Venezuela
  • Human Australia, New Zealand, Haiti, India Thailand and the USA
  • Bear USA
  • Camel USA

Incidence of Pythiosis in the US

  • 1995-2003 158 cases (all species)
  • 2004 72 cases (all species)
  • 2005 (Jan-Aug) 102 cases (all species)
  • 2010 752 cases (all species)


Clinical Characteristics of Pythiosis

  • Cutaneous Keratinitis Necrosis
  • Subcutaneous Lymphatic Periorbital
  • Arterial Large arteries Aneurysm
  • Intestinal Intestinal tract
  • Systemic Liver Lungs

Feline Pythiosis

Canine Pythiosis

Intestinal pythiosis in canines is often misdiagnosed as lymphoma.

Bovine Pythiosis (Venezuela)

Equine Pythiosis

Chronic Pythiosis Osteo infection

Human pythiosis in the USA

Human Pythiosis, Thailand

Laboratory Diagnosis

  1. Very few laboratories are familiar with P. Insidiosum
  2. Difficult to culture
  3. Difficult to identify in histopath studies
  4. Difficult to identify by clinical presentation

Differential Diagnosis

Pythium insidiosum Oomycete
Conidiobolus coronatus Basidiobolus ranarum
Fungal zygomycetes

Classical treatments used against Pythium insidiosum

  • Surgery ~40%
  • Iodines ~35-40%
  • Amphotericine B <30%
  • Itraconazole <30%

What is Pythium Immunotherapy?

  • Allergy desensitization via Subcutaneous presentation of purified P. insidiosum antigens. Switching of the of the immune response from TH2 (allergic) to TH1 mode (protective and curative)


T helper 2 response T helper 1 response
Eosinophils Mast cells IgE IL5 IL4 Immunotherapy → Macrophages T lymphocytes (cytotoxic?) IFN IL2
Pythium Infection Infection Cleared

Before Immunotherapy

Day 4

Day 8

Day 15

Pythium antibody in Canines participating in Field Trial Training and Competitions

Result #Dogs % of Total
Negative 105 61.4
Borderline 43 25.1
Positive 23 13.5
Total 171 100
* Normal Dogs <1 % Positive ,<5% Borderline, >95% Negative

Pythium Associated Symptoms in Field Trial/Hunt Canines

Blood test Vomiting Diarrhea in Last 12 Months
Negative 7 (6.7%)
Borderline 3 (7.0%)
Positive 13 (26.1%)

Efficacy of Pythium Immunotherapy

Efficacy of Pythium V2 Immunotherapy In Canines

Immunotherapy Treatment Progression





Surgery + Immunotherapy


  • Purified protein extract of P. insidiosum
  • Early treatment increases success rate
  • Use as first option treatment
  • >85% effective in equines, 50% effective in canines
  • Combine with surgical de bulking in chronic cases
  • Pythium insidiosum is endemic in tropical and subtropical regions
  • Differential diagnosis includes subcutaneous mycosis, lymphoma, parasitic and bacterial infections
  • Serologic diagnosis is fast and accurate
  • Itraconazole, Amphotericin B, Iodine and surgery have shown limited success
  • Immunotherapy alone or in conjunction with other therapies demonstrates highest success rate

Lagenidium gigantum

  • Similar to Pythium in class
  • Similar to Pythium in disease characteristics
  • Essentially identical to Pythium in tissue sections
  • Does not respond to Pythium Immunotherapy

Accurate Diagnosis is Essential

  • Clinical presentation is not good enough
  • Histopath examination is not good enough
  • Pythium test alone is not good enough
  • Accurate diagnosis requires blood test for both Pythium and Lagenidium