Equine Zoonoses

Question 1

St. Louis Encephalitis (Flavivirus)

Answer 1

Transmission: Mosquito bite.
CS (human): less than 1% clinically apparent; fever, headache, aseptic meningitis/encephalitis, 7% fatal.
CS (equine): subclinical.

Question 2

West Nile Virus (Flavivirus)

Answer 2

Transmission: Mosquito bite.
CS (human): 20% clinically apparent; fever, headache, sore throat, backache, myalgia, lympadenopathy, severe illness in 1 of 150 cases; high fever, headache, stiff neck, muscle weakness, CNS signs (disorientation, coma, tremors, convulsions, vision loss, numbness, paralysis), death in 1 of 10.
CS (equine): fever, CNS signs (ataxia, facial twitching, muscle twitching, proprioception deficits, behavioral changes, recumbency, convulsions), death.

Question 3

Eastern Equine Encephalitis (Alphavirus)

Answer 3

Transmission: Mosquito bite.
CS (human): fever, headache, vomiting, lethargy, aseptic meningitis/encephalitis, delirium, coma, 33% fatal, persistent brain damage & paralysis.
CS (equine): encephalitis.

Question 4

Western Equine Encephalitis (Alphavirus)

Answer 4

Transmission: Mosquito bite.
CS (human): fever, headache, stiff neck, spastic paralysis, confusion, 3-14% fatal, persistent brain damage, personality changes, spastic paralysis.
CS (equine): encephalitis.

Question 5

Venezeulan Equine Encephalitis (Alphavirus)

Answer 5

Transmission: Mosquito & biting flies (Culicoides).
CS (human): high rate of subclinical infection; fever, headache, stiff neck, nausea, diarrhea, vomiting, encephalitis, fatality <1%.
CS (equine): encephalitis.

Question 6

Equine Hendra Virus (Paramyxovirus)

Answer 6

Transmission: Bat urine, infected horse fluids, tissues, or excretions.
CS (human): cardiopulmonary signs (flu-like symptoms, pneumonitis, respiratory failure, arterial thrombosis, cardiac arrest), fatality 60%.
CS (equine): acute respiratory syndrome, occasional CNS signs, death in 1-3 days.

Question 7

Rabies (Rhabdovirus)

Answer 7

Transmission: Bite from infected bat, raccoon, skunk, fox, dog.
CS (equine): “paralytic” & “dumb” form more common than “furious” form, cardiorespiratory failure & death within 2-5 days (rarely up to 2 weeks).

Question 8

Vesicular Stomatitis (Rhabdovirus, Vesiculovirus)

Answer 8

Transmission: Transcutaneous or transmucosal contamination, bite from sand flies, biting midges, black flies.
CS (human): rare, flu-like symptoms, lasts a few days.
CS (equine): fever, excessive salivation, blister-like lesions in mouth, tongue, lips, nostrils, hooves, lasts 1-2 weeks.

Question 9

Salmonellosis (S. enterica sp enterica, S. typhimurium)

Answer 9

Transmission: Fecal-oral.
CS (human): fever, GI signs (vomiting, diarrhea, abdominal cramps, dehydration).
CS (equine): diarrhea, abortion, septicemia, death (foals).

Question 10

Rattles (Rhodococcus equi)

Answer 10

Transmission: Environmental contamination, inhalation, wound contamination.
CS (human): rare, mostly immunocompromised patients; slowly progressive granulomatous pneumonia, CNS abscesses, lymphadenitis.
CS (equine): foal pneumonia, multifocal ulcerative enterocolitis, pyogranulomatous typhlocolitis, abscesses.

Question 11

Anthrax (Bacillus anthracis)

Answer 11

Transmission: Inhalation/ingestion of spores, contact with abrasion.
CS (human): cutaneous form ulcers most common, GI form from ingestion of infected meat.
CS (equine): septicemic form common; high fever, colic, hemorrhagic enteritis, depression, death in 2-4 days.

Question 12

Brucellosis (B. abortus, B. suis, B. melitensis)

Answer 12

Transmission: Contact with infected lesions.
CS (human): intermittent fever, headache, chills, depression, weakness, arthralgia, myalgia, weight loss, orchitis/epididymitis.
CS (equine): fistulous withers, poll evil, late abortion, arthritis, orchitis.

Question 13

Dermatomycosis (Trichophyton equinum)

Answer 13

Transmission: Direct contact with infected horse or fomite.
CS (human): ringworm lesions.
CS (equine): round, hairless, thickened, scaly lesions.

Question 14

Dermatophilosis (Dermatophilus congolensis)

Answer 14

Transmission: Direct contact or insect bite.
CS (human): pustular desquamative dermatitis.
CS (equine): exudative, crusted skin lesions (“paint-brush” appearance).

Question 15

Sporotrichosis (Sporothrix schenkii)

Answer 15

Transmission: Penetrating inoculation or direct contact with infected wounds, rarely inhalation.
CS (human): ulcerated nodules, painful lymphadenopathy.
CS (equine): ulcerated nodules, ruptured lymphatic chains, distal limbs most common.

Question 16

MRSA (Staph aureus)

Answer 16

Transmission: Nosocomial (hospital-associated) or community-associated.