1. HORSES: Venezuelan equine encephalomyelitis (VEE) (genus: ALPHAVIRUS, family: TOGAVIRIDAE)

Question 1

disease

Answer 1

acute mosquito-borne disease

Question 2

caused by

Answer 2

Alphavirus

Question 3

characterized by

Answer 3

fever, neurological signs and death

Question 4

pathogen

Answer 4

genus: alphavirus, family: togaviridae, RNA virus

Question 5

subtypes?

Answer 5

6 subtypes: 1-6 > epizootic (or epidemic) and enzootic (or endemic) groups, subtype 1 subdivided to 5 serovers: AB to F

Question 6

environment?

Answer 6

stable at pH 7-8, inactivated quickly by acidic pH

Question 7

susceptible ?

Answer 7

-radiant sunlight, moist or dry heat and drying

-likes cool, moist and dark

Question 8

subtype: 1-A, 1-B, 1-C. cycle, disease, transmission, natural reservoir

Answer 8

-cycle: epizootic/epidemic

-disease: horses, humans

-tranmission: many mosquito species

-natural reservoir: unknown

> horses and donkeys act as amplifiers

Question 9

subtype: 1-D, 1-E, 1-F AND 2-6. cycle, disease, transmission, natural reservoir
(epizootic/epidemic subtype 1-AB and 1-C VEE strains arise from genetic mutation of enzootic subtype 1-D strains)

Answer 9

-cycle: enzootic/endemic

-disease: humans

-transmission: mosquitoes CULEX spp.

-natural reservoir: rodents (living in swamps and forests)

Question 10

HR

Answer 10

1. equids!
   -horses, cattle, swine dogs, chickens, cotton rats, opossums, gray foxes, bats, wild birds-infection

Question 11

zoonotic?

Answer 11

YES

Question 12

M & M

Answer 12

-EPIdemic (EPIzootic) VEEV
>morbidity: 10-100%
>mortality 38-90 %

-ENdemic (ENzootic)
>usually no serious dz or deaths in horses
>1990s outbreak mortality 30-50%
-humans: morb-more 10% mort. less or same as 1%

Question 13

distribution

Answer 13

-ENzootic: Mexico, South and Central America

-EPIzootic (EPIdemic): South and Central America

> no outbreaks in 2017-2020!!

> outbreaks 2021 Panama, Brazil

Question 14

EPIzootic transmission- who is primary vector-vertebrate host and dead-end hosts?
(EPIzootic= tauti leviää nopeasti ja laajasti eläinten populaatiossa)

Answer 14

-primary vector: multiple mosquito species

-vertebrate hosts: horses

-dead-end hosts: humans

other species naturally infected but not amplifiers

> PRINCIPAL AMPLIFYING HOSTS: horses, donkey

Question 15

ENzootic transmission: primary vector-vertebrate host and dead-end host ? (ENzootic=tauti esiintyy jatkuvasti ja suhteellisen tasaisesti eläinpop)

Answer 15

-primary vector: CULEX (Melanoconion) species

-vertebrate host: rodents (who live near swamps and rain forests)

-dead end hosts: humans

Question 16

dead end host in epizootic (epidemic) and enzootic (endemic) transmission?

Answer 16

HUMANS

Question 17

transmission?

Answer 17

-excretion: body fluids=EPIdemic (1A-C)

-vectors: mosquitoes
>occasionally direct contact and aerosols

-route: insect bites

NB! VEEV can cross placenta in pregnant women !!!!

Question 18

IP horses

Answer 18

1-5 days

Question 19

who are most sus to EPIdemic VEE?

Answer 19

HORSES

Question 20

clinical signs: epidemic horses

Answer 20

-fever, anorexia, depression
-flaccid lips, droopy eyelids and ears
-incoordination, blindness

• neurological signs appear on day 5

Question 21

mortality in horses

Answer 21

50-90%

Question 22

horses clinical sign IN UTERO TRANSMISSION

Answer 22

abortion and stillbirth

Question 23

clinical signs: enzootic horses

Answer 23

subclinical or mild, nonspecific signs

Question 24

IP humans

Answer 24

1-6 days

Question 25

clinical signs: humans

Answer 25

-usually acute, often mild, systemic illness -fever, chills, headache, myalgia: coughing, vomiting, diarrhea

Question 26

CNS signs humans

Answer 26

-encephalitis in 4% kids -less 1% symptomatic adults

Question 27

clinical signs: pregnant human

Answer 27

fetal encephalitis, placental damage, abortion/stillbirth, congenital dz

Question 28

deaths in humans?

Answer 28

rare

Question 29

humans recovery

Answer 29

2 weeks

Question 30

PM horses

Answer 30

-nonspecific -equids may have no lesions in CNS, or there may be extensive necrosis with hemorrhages -may be some extracranial lesions are too variable to be diagnostically useful >PANCREAS, LIVER, HEART

Question 31

DDx

Answer 31

-EEE, WEE (eastern or western equine encephalomyelitis) -japanese encephalitis -west nile fever -rabies -tetanus -african horse sickness -bacterial meningitis -toxins

Question 32

diagnosis material

Answer 32

-blood -brain -pancreas

Question 33

diagnosis: in lab

Answer 33

-virus isolation -PCR -Serology: 1.PNR=Plaque Reduction Neutralisation 2. ELISA 3. CF=Complement fixation 4. HI=Haemagglutination Inhibiton

Question 34

prevention and control

Answer 34

-quarantine and restriction of movements -vector control -VACCINATION: >Attenuated (strain TC-83) >Inactivated (strain TC-83)

Question 34

Tx?

Answer 34

-no -only TLC (Tender Loving Care)

Question 35

can be used as

Answer 35

BIOLOGICAL WEAPON-aerosolized VEEV

Question 36

clinical signs: horses: pic> horse showing classic ''.......'' due to lack of coordination from viral encephalitis infection such as VEE

Answer 36

''leaning stance''

Question 37

IP: humans: highly variable (mostly 1-6d) can be long as

Answer 37

21-180 days > depending primarily susceptibility of animal

Question 38

PM: brain of horse suffering from VEE showing

Answer 38

massive hemorrhaging of brain from head trauma that occurred during seizures > this is not direct result of virus but secondary head trauma from encephalitis complications

Question 39

diagnosis of VEE virus infection in equids requires

Answer 39

-demonstration of specific antibodies in paired serum samples collected in acute and convalescent (recovery) PHASES: o PRN antibodies appear within 5–7 days after infection o CF antibodies within 6–9 days after infection o HI antibodies within 6–7 days after infection

Question 40

PHASES of VEE

Answer 40

1. acute phase 2. convalescent phase