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Disease Information

Current information on infectious diseases of horses is listed here. More information may be available at the office of your state veterinarian.


To learn more about how certain diseases are transmitted, see

Iatrogenic vs Natural Transmission

Domestic Diseases

Anthrax (Bacillus anthracis)

Anthrax in Horses, UKY

Overview of Anthrax, Merck Vet Manual

Anthrax, OIE

Blastomycosis (Blastomyces dermatitidis

Systemic blastomycosis in a horse, Journal of Veterinary Diagnostic Investigation

Botulism (Clostridium botulinum, types A, B, C, D) 

Botulism, AAEP

Botulism: A Deadly Disease That Can Affect Your Horse, UKY

Brucellosis (Brucella abortus) 

Brucellosis in the Horse, Bell Equine

Clostridial Enteritis (Clostridium perfringens, Clostridium difficile)

Clostridial Diarrhea in Adult Horses, AAEP


Coronavirus Owner Factsheet

Equine Coronavirus and COVID-19

Dermatophilosis or Streptothricosis (Dermatophilus congolensis

Overview of Dermatophytosis, Merck Vet Manual

Eastern Equine Encephalitis (Eastern equine encephalomyelitis)

EEE Owner Factsheet

Arboviruses, AAEP

Arbovirus Education 

Equine herpesvirus 1 & 4 related diseases (equine herpesvirus 1 & 4, equine rhinopneumonitis virus)

EHV Owner Factsheet 

EHM Owner Factsheet (EHV neurologic disease)

Equine Herpesvirus Resources, AAEP

IDOHC EHM Guidance Document, USAHA

Equine infectious anemia (Equine infectious anemia virus) 

EIA Owner Factsheet

EIA AAEP Guidelines

Equine Infectious Anemia (EIA) Factsheet, APHIS

USDA/APHIS Annual Report: EIA 2019

Equine influenza (A/Equine/1/Prague 56 [H7N7] and A/Equine/2/Miami 63 [H3N8] 

Equine Influenza Owner Factsheet

Equine Influenza Virus, AAEP


Equine Parvovirus-hepatitis Virus (EqPV-H)

Equine Parvovirus Factsheet 

Equine piroplasmosis (Theileria equi, Babesia caballi, T. haneyi

EP Owner Factsheet

Equine Piroplasmosis Factsheet, APHIS

Theileriosis, OIE

Equine Protozoal Myeloencephalitis (Sarcocystis neurona)

Equine Protozoal Myeloencephalitis, AAEP

EPM Owner Factsheet

Equine pythiosis (Pythium insidiosum

Equine Pythiosis, MSU

Equine viral arteritis (equine arteritis virus) 

Equine Viral Arteritis, AAEP

Leishmaniasis (Leishmania siamensis

Leishmaniasis, HorseDVM


Leptospirosis Guidelines, AAEP
Leptospirosis in Horses, Merck Vet Manual

Lyme Disease

Lyme Disease Owner Factsheet


Mange (Demodex equi, Psoroptes equi

Mange in Horses, Merck Vet Manual

Nocardioform Placentitis 

Nocardioform Placentitis Guidelines, AAEP

Pigeon Fever (Ulcerative lymphangitis) 

Pigeon Fever Factsheet

Pigeon Fever, AAEP

Potomac Horse Fever or Equine Neorickettsiosis 

Potomac Horse Fever Factsheet 

Potomac Horse Fever, AAEP

Rabies (Rabies virus) 

Rabies Owner Factsheet

Rabies, AAEP

Overview of Rabies, Merck Vet Manual

Rhodococcus equi

Rhodococcus equi, AAEP

Ringworm (Microsporum equinum, M. gypseum, T. equinum

Overview of Dermatophytoses, Merck

Salmonellosis (various Group A, B, and C salmonellae) 

Salmonellosis, AAEP

Strangles (Streptococcus equi var. equi

Strangles Owner Factsheet

Streptococcus equi var. equi, AAEP

Vesicular stomatitis (Vesicular stomatitis virus, subtypes New Jersey and Indiana) 

Vesicular Stomatitis Owner Factsheet

Vesicular Stomatitis, AAEP

USDA/APHIS VSV Information

West Nile encephalitis (West Nile virus) 

WNV Owner Factsheet 

West Nile Virus, AAEP

West Nile Virus, APHIS

Western Equine Encephalomyelitis (Western equine encephalomyelitis virus) 

WEE Owner Factsheet

Arboviruses, AAEP

Foreign Diseases

African horse sickness (African horse sickness virus)

African Horse Sickness Owner Factsheet

OIE information

Contagious Equine Metritis (Taylorella equigenitalis)

AAEP CEM Guidelines

APHIS information

Dourine (Trypanosoma equiperdum)

OIE Information

Equine piroplasmosis (T. equi, B. caballi, T. haneyi)

EP Owner Factsheet

Equine Piroplasmosis Factsheet, APHIS

Theileriosis, OIE

Epizootic Lymphangitis 
Epizootic Lymphangitis Factsheet

Glanders (Burkholderia mallei)

AAEP Guidelines

Glanders Owner Factsheet

Hendra (Equine Morbilivirus)

OIE Information

Surra (Trypanosoma evansi)

OIE Information

Venezuelan equine encephalomyelitis (virus subtypes 1AB, 1C, 1E)

OIE Information

AAEP arbovirues