Equine Respiratory Diseases

Question 1

what are some viruses associated with equine upper respiratory tract disease?

Answer 1

herpesvirus
influenza virus
rhinoviruses
equine arteritis virus

Question 2

what viruses are most clinically significant of those that cause equine upper respiratory tract disease?

Answer 2

equine herpes types 1 and 4 (EHV-1, EHV-4)
equine influenza virus

Question 3

who does respiratory infection by equine herpes virus types 1 and 4 primarily affect?

Answer 3

young horses: less than 2 years old

Question 4

what do equine herpes virus types 1 and 4 cause?

Answer 4

typically mild, transient, or subclinical
spreads rapidly in susceptible populations

Question 5

what do more severe forms of equine herpes virus type 1 and 4 cause?

Answer 5

EHV-4: respiratory infections
EHV-1: severe sequelae (abortion, neonatal death, myeloencephalopathy)

Question 6

what percent of horses have latent herpes viruses?

Answer 6

up to 60% of infected horses

Question 7

how can you confirm infection by herpes viruses?

Answer 7

virus isolation
polymerase chain reaction
immunofluorescent detection of viral antigen
serology

Question 8

what does herpes virus infection in equine/rhinopneumonitis do?

Answer 8

cytolytic destruction and cell loss
vigorous inflammatory response with infiltration of mononuclear cells follows
viremic viral spread
infection of vascular endothelial cells may occur

Question 9

how do horses with equine herpes virus infection/rhinopneumonitis present?

Answer 9

rhinitis
pyrexia
submandibular lympathadenopathy
conjunctivitis

Question 10

what are the complications of equine herpes virus infection/rhinopneumonitis?

Answer 10

late term abortion
EHV-1: mortality in infected foals almost 100%
EHV-1: myeloencephalopathy potentially (vasculitis within small vessels of central nervous system): poor prognosis

Question 11

what is the goal of vaccination for equine herpes viruses?

Answer 11

herd preventative
lessen respiratory disease severity and reduce spread
prevent late term abortions and provide suckling foals with passive antibody during first months of life

Question 12

what causes equine influenza?

Answer 12

type A influenza virus: surface hemagglutinin antigens (HA) and neuraminidase (NA) as either H7N7 or H3N3

Question 13

what does aerosol infection of equine influenza involve?

Answer 13

ciliated respiratory epithelium: upper respiratory infection

Question 14

who do type A influenza viruses infect?

Answer 14

birds
swine
horses
humans
other mammals

Question 15

what viruses serve as the reservoir for all type A influenza virus subtypes?

Answer 15

avian viruses in aquatic birds

Question 16

how do influenza viruses infect?

Answer 16

aerosol route
infects ciliated epithelial cells: deciliation and loss of mucociliary protection

Question 17

what is the incubation period of influenza viruses?

Answer 17

1-2 days

Question 18

what bacteria commonly causes pneumonia in adult equines?

Answer 18

Streptococcus equi subspecies zooepidemicus
beta-hemolytic strep that is a normal part of equine pharyngeal flora

Question 19

what are some other bacteria that may be involved in adult equine pneumonia (not Streptococcus equi subspecies zooepidemicus)?

Answer 19

Pasteurella spp
Escherichia coli
Klebsiella spp
Enterobacter spp
Pseudomonas spp

Question 20

how do Streptococcus zooepidemicus organisms reach the lower respiratory tract?

Answer 20

inhalation
aspiration
hematogenous spread
when normal defense mechanisms are compromised

Question 21

are mycoplasma known to be primary pathogens in equine respiratory disease?

Answer 21

no

Question 22

what is pleuropneumonia associated with in equines?

Answer 22

stressful event: viral disease or extended transportation (elevated environmental temperature and increased aerosolized bacteria)

Question 23

what organisms are often included in equine pleuropneumonia?

Answer 23

Streptococcus zooepidemicus
Pasteurella spp
Actinobacillus spp
E. coli
Klebsiella pneumoniae
mixed: anaerobic Bacteroides spp and Clostridium spp

Question 24

is pleural effusion often associated with equine pneumonia?

Answer 24

yes: increased permeability of capillaries in visceral pleura

Question 25

what do horses with equine pleuropneumonia present with?

Answer 25

fever anorexia weight loss depression cough respiratory distress possibly limb edema

Question 26

what is the pathogenesis of equine pleuropneumonia?

Answer 26

pleural effusion, starts sterile, then bacterial invasion fibrin deposits

Question 27

how can progression of sterile pleural effusion to a septic pleuritis be prevented?

Answer 27

diligent assessment of pleural effusion via ultrasound and percussion antimicrobial therapy to prevent bacterial colonization

Question 28

at what age is foal pneumonia common?

Answer 28

1-6 months

Question 29

what are the most common bacterial agents in foal pneumonia, and the less common ones?

Answer 29

most common: Streptococcus zooepidemicus and Rhodococcus equi Actinobacillus spp, Bordatella bronchiseptica, Escherichia coli, Klebsiella pneumoniae, Pasteurella spp, Pseudomonas spp anaerobic agents are uncommonly involved

Question 30

what is Rhodococcus equi?

Answer 30

gram positive pleomorphic coccobacillus that is facultative intracellular pathogen of equine macrophages

Question 31

how does Rhodococcus equi survive?

Answer 31

inhibits phagosome-lysosome fusion of alveolar macrophages: survives and replicates inside

Question 32

what signs do foals develop with Rhodococcus equi?

Answer 32

fever elevated respiratory rate hyperfibrinogenemia cough other body systems may be infected: abscesses, enteritis, septic arthritis, polysynovitis

Question 33

what is Strangles?

Answer 33

acute contagious disease of horses characterized by inflammation of the upper respiratory tract with abscessation of submandibular lymph nodes

Question 34

how does Streptococcus equi work?

Answer 34

enters via mouth or nose and attaches to tonsillar epithelial cells, to subepithelial follicles and then to mandibular and pharyngeal lymph nodes can spread further

Question 35

how does Streptococcus equi evade killing?

Answer 35

antiphagocytic surface factors prevent neutrophil phagocytosis and killing

Question 36

what is purpura hemorrhagica?

Answer 36

immune mediated necrotizing vasculitis resulting in subcutaneous edema after streptococcal infection (rare but very serious)

Question 37

what does disease of the paranasal sinuses in horses occur from?

Answer 37

extension of rhinitis into the sinuses, by extension of tooth abscesses, and due to neoplasia

Question 38

what is equine progressive ethmoid hematoma?

Answer 38

benign slowly enlarging encapsulated hemorrhagic mass in mucosa of equine ethmoid turbinates

Question 39

what are guttural pouches in horses?

Answer 39

diverticulum of the auditory canal that communicates with the pharynx via a slit-like opening

Question 40

what causes equine parasitic airway disease?

Answer 40

Dictyocaulus arnfieldi

Question 41

who does Dictyocaulus arnfieldi infect?

Answer 41

horses donkeys mules zebras

Question 42

who is airway inflammation common in?

Answer 42

young equine athletes

Question 43

what is recurrent airway obstruction caused by?

Answer 43

prolonged and debilitating inflammatory response to inhaled organic dusts

Question 44

what are the clinical signs of recurrent airway infection?

Answer 44

elevated respiratory rate and accentuated expiration

Question 45

what viruses may cause pneumonia in foals?

Answer 45

adenoviruses

Question 46

what percent of adult horses have been exposed to equine herpes virus 1 or 4?

Answer 46

90%

Question 47

fetuses infected with EHV-1 during late gestation _____________________________________

Answer 47

may be born alive, but mortality of congenitally infected foals is nearly 100%

Question 48

what are some sequelae of equine influenza?

Answer 48

chronic pharyngitis sinusitis chronic bronchiolotis airway hyperreactivity

Question 49

what is pleuropneumonia associated with?

Answer 49

stressful event viral disease extended transportation

Question 50

what do the organisms involved in equine pleuropneumonia suggest?

Answer 50

that aspiration of pharyngeal secretions likely occurs

Question 51

what happens with fibroblasts in pleuropneumonia?

Answer 51

invade during organization phase and produce restrictive membrane

Question 52

what is thought to predispose foals to pneumonia?

Answer 52

not respiratory viruses overcrowding parasitism poor nutrition heat stress congenital immunodeficiency

Question 53

what does Rhodococcus equi cause in foals?

Answer 53

chronic pyogranulomatous pneumonia

Question 54

what conditions favor multiplication of Rhodococcus equi?

Answer 54

dry, dusty

Question 55

what does survival and replication of Rhodococcus equi in macrophages result in?

Answer 55

abscess formation

Question 56

what does Actinobacillus equuli do?

Answer 56

septicemia and septic arthritis in foals

Question 57

what does localized inflammation from Streptococcus equi cause?

Answer 57

pharyngitis difficulty swallowing anorexia depression

Question 58

what can inspisated pus from strangles cause?

Answer 58

chondroids in guttural pouches with bacteria

Question 59

what can result in serious disease with strangles?

Answer 59

metastatic absessation in abdominal or thoracic lymph nodes

Question 60

what does immune-mediated necrotizing vasculitis occasionally follow?

Answer 60

streptococcal infections immune complexes involving IgA and IgM and streptococcal antigens implicated

Question 61

why does disease of the paranasal sinuses in horses occur?

Answer 61

extension of rhinitis into sinuses extension of tooth abscesses neoplasia

Question 62

what is guttural pouch mycosis?

Answer 62

mycotic plaques on pouch wall

Question 63

what is the most important respiratory tract evaluation in uncomplicated inflammatory airway disease?

Answer 63

transtracheal aspirate or bronchoalveolar lavage

Question 64

what suggests an allergic response to mold species in the stable environment in recurrent airway obstruction?

Answer 64

elevated levels of IgE in bronchoalveolar lavage fluid