Equine Zoonoses

Question 1

Which equine flavivirus that is maintained in Passerine birds and transmitted by mosquito bite, and horses are considered “dead end” hosts of this virus. Many of the cases are clustered in low socioeconomic areas and old neighborhoods?

Answer 1

St. Louis Encephalitis

Question 2

T/F: Most human infections of St. Louis Encephalitis are clinically apparent with meningitis or encephalitis, most of which turn out to be fatal; however, animal cases are subclinical.

Answer 2

false – less than 1% of human cases are clinically apparent. Clinical disease would consist of fever, headache, aseptic meningitis, or encephalitis. Only 7% of those cases are fatal. It is true that animal cases are subclinical.

Question 3

How can we do surveillance on and control the arboviruses (SLE, WNV, EEE, WEE, etc.)?

Answer 3

surveillance:
serological monitoring in sentinel chickens

control:
eliminate mosquito breeding areas
do outdoor activities during times when mosq arent as active (dusk and dawn)
use insect repellent
put screens on windows
put fans in horse barns and turn off the lights at night

Question 4

This flavirvirus originated in 1999 in NYC at the Bronx Zoo, where penguins were dying. The virus spread across the US in 5 years. The virus is maintained in birds and is acquired from mosquitoes OR blood transfusions and organ transplants.

Answer 4

west nile virus

Question 5

Describe the human symptoms of a west nile virus infection.

Answer 5

most (80%) infections are asymptomatic
20% have flu-like symptoms
It is rare to get severe disease and/or the neuroinvasive form which is fatal.
Infections are most common in older people (when the immune system is not as good as it used to be).

Question 6

Describe the symptoms of horses infected by west nile virus?

Answer 6

fever and encephalomyelitis
ataxia, twitching of muzzle, twitching neck, shoulder, and pectoral muscles.

Question 7

Besides humans and horses, what other species can be affected by west nile virus?

Answer 7

birds*
goats, sheep, dogs, llamas, reptiles, and bears

Question 8

This alphavirus has a cycle between Passerine birds and waterfowl and mosquitoes, but overflows into human and equine populations. Infection occurs in late summer and early fall and it is associated with fresh water swamps where mosquito populations are higher.

Answer 8

eastern equine encephalitis

Question 9

This virus causes clinical disease in humans with symptoms of fever, headache, vomiting, lethargy, aseptic meningitis, or encephalitis, delirium, and coma. 1/3 of the cases are fatal, with younger and older people being most susceptible.

Answer 9

eastern equine encephalitis

Question 10

What are the affected of animals infected with EASTERN equine encephalitis virus?

Answer 10

encephalitis

Question 11

This alphavirus is endemic in the rural west and infections occur mostly during the summer. The virus is maintained in Passerine birds and transmitted by mosquito bites.

Answer 11

western equine encephalitis virus

Question 12

Man is considered an accidental host for WESTERN equine encephalitis virus. What are the symptoms of human infection?

Answer 12

fever, stiff neck, spastic paralysis, mental confusion

Few cases are fatal (3-14%); young adults and children are most affected.

Question 13

This alphavirus has 2 strains – epidemic and endemic. It is prevalent in tropical and subtropical america (mexico, south of mexico). When outbreaks occur, they usually span over long periods of time.

Answer 13

Venezuelan equine encephalitis

Question 14

What is the reservoir for the endemic strain of VEE?
What about the epidemic strain?

Answer 14

endemic – rodents and mosquitoes
epidemic – horses and mosquitoes

Question 15

What is the biggest difference between EEE and WEE versus VEE?

Answer 15

birds are NOT a part of the cycle for VEE.
Man gets the infection directly from mosquitoes that are feeding off of infected equines.
Direct human-to-human transmission as well as human to mosquito transmission are also possible.

Question 16

What are the symptoms of human VEE infection – discuss the type of infection and fatality rate?

Answer 16

subclinical disease is high
clinical disease would be flu-like symptoms and encephalitis.
fatality is LOW.

Question 17

This Henipavirus/Paramyxovirus is only found in Australia. It is maintained in fruit-eating bats. Horses become infected with this virus by eating material contaminated with bat urine. Humans get exposed by body fluids of infected horses.

Answer 17

equine hendra virus

Question 18

what are the symptoms of a horse that is infected with equine hendra virus?

Answer 18

acute respiratory syndrome and death in 1-3 days

Question 19

what are the symptoms of a human with equine hendra virus?

Answer 19

flu-like symptoms that progress to pneumonitis, resp failure, renal failure, arterial thrombosis, and cardiac arrest.
That being said, the fatality rate is 60%.

Question 20

what is the public health significance of equine hendra virus?

Answer 20

is maintains itself in the bat population and spreads t horses accidentially.
humans cant get it directly from the bat, but do acquire it from horses.

Question 21

what is the main control/prevention measure for equine hendra virus?

Answer 21

vaccination

Question 22

This virus has several strains maintained in specific species – fox (TX), skunk (Central US), raccoon (NY), and bat (US). This virus should be considered as a differential for all cases of acute encephalitis or undifferentiated neuro dz. Affected animals die with 2-5 days of onset of clinical signs. The primary control method for this virus is vaccination and removal of wildlife.

Answer 22

rabies

Question 23

Which form of rabies is most common in horses?

Answer 23

“paralytic” or “dumb” form in horses.

furious form more common in other species

Question 24

T/F: raccoon rabies is not of risk to opossums, groundhogs, and beavers.

Answer 24

false

Question 25

This reportable rhabdovirus is found mostly during the warm months in southwest US – AZ, CO, NM, and UT.
It is transmitted transcutaneously or transmucosally by sand flies, biting midges, and black flies.

Answer 25

Vesicular stomatitis

Question 26

What are the symptoms of vesicular stomatitis in horses?

Answer 26

there is a very short incubation period (2-4 days) where fever, excess salivation, and blister-like lesions in mouth, tongue, lips, nostrils, and hooves (causes lameness).
animals will recover within 1-2 weeks.

Question 27

T/F: if humans become infected with vesicular stomatitis virus, most cases are fatal.

Answer 27

false – it is rare in humans and incubation is 1-2 days. thereafter, flu-like symptoms occur and only last for a few days.

Question 28

how can we prevent vesicular stomatitis virus?

Answer 28

wear protective clothing and gloves

Question 29

This disease is responsible for nosocomial outbreaks in vet hospitals in the US. Zoonotic transmission is through fecal-oral route and requires high number of organism to cause clinical disease in a health adult. However, concurrent disease, antibiotic usage, and immunosuppression would increase risk and lower the amount of org req to cause disease.

Answer 29

salmonellosis

Question 30

What are the clinical signs of salmonellosis in horses?

Answer 30

diarrhea, abortion, septicemia, and death (esp in foals).
healthy carriers - intermittent shedding and only dev symptoms when stressed.

Question 31

how do humans get salmonellosis and what are the clinical signs?

Answer 31

direct contamination from sick horses
symptoms – fever, v/d, abd. cramps, dehydration

Question 32

what is the bets control/prevention measure for salmonellosis?

Answer 32

personal hygeine, barrier protection, and disinfecting contaminated instruments

Question 33

This organism is found in the soil (esp where livestock graze) and is an opportunistic pathogen of severely compromised patients. It causes lung abscesses and pneumonia in humans and horses

Answer 33

rhodococcus equi

Question 34

__________, caused by bacillus anthracis and most cases occur in warm, dry months like july-sept. Transmission occurs through the spore-form of the organism (occurs when vegetative form is exp. to air). which are infective through inhalation, ingestion, or contact with abrasion.

Answer 34

anthrax

Question 35

Differentiate the clinical signs of anthrax in horses vs humans

Answer 35

horses – septicemia with high fever, colic, enteritis + hemorrhage, depression, and death within 2-4 days

human – ulcer with black dead tissue (cutaneous form), pulmonary anthrax (inhalation), or GI form (infected meat)

Question 36

what is the treatment for anthrax and the best prevention strategies?

Answer 36

tx: penicillin
prev: vaccination of animals in endemic areas, barrier precautions (impermeable gloves, boots, clothes)

Question 37

Horses are accidental hosts for this organism/disease and infection usually occurs when horses share a pasture with cattle/swine. Zoonotic transmission is not high risk. Clinical signs in horses are fistulous withers, poll evil, or fistulous bursitis. Humans can get infected from horses through exposure of open lesion.

Answer 37

brucellosis / brucella abortus, brucella melitensis

Question 38

T/F: horses may not show signs of brucellosis infection for as long as 2 years post-exposure and may present with late abortion, arthritis, and orchitis.

Answer 38

true

Question 39

what is the treatment for brucellosis?

Answer 39

rifampin and doxy for 6 weeks

Question 40

This disease is caused by direct contact with horses or fomites (blankets, equipment, etc.). The lesions are round and hairless and skin has scales. In humans, it looks like ringworm lesions.

Answer 40

dermatomycosis
caused by trichophyton equinum*, T. mentagrophytes, and microsporum equinum

Question 41

what is the best prevention for dermatomycosis?

Answer 41

barrier protection (gloves, gowns)
disinfect or dispose of infected grooming tools and other items.

Question 42

The clinical signs of this disease in horses are:
rain rot are “paint brush” clumps of hair cemented together with exudate. In humans, it is pustular desquamative dermatitis.

Answer 42

dermatophilosis
agent: dermatophilus congolensis

Question 43

what is the transmission of dermatophilus congolensis?

Answer 43

direct or mechanical insect vector

Question 44

What is MRSA and why are we concerned about it?

Answer 44

MRSA stands for methicillin resistant staph aureus. We are concerned about this because resistance is mediated by a gene (mecA) that does not allow for binding of B-lactams to the bacterial cell wall.