Flaviviruses and Encephalitides

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Questions and Answers

What is the primary mode of transmission of EHV-1?

Fomites and indirect contact

Vector-borne transmission through ticks and mosquitoes

Direct contact, nasal secretion, reproductive discharge, placenta or aborted fetus (correct)

Contaminated food and water

What is the most common syndrome caused by EHV-1?

Rhinopneumonitis

Abortion (correct)

Peracute vasculitis

Neurological disease

What is the typical duration of viral incubation for EHV-1?

11-14 days

1-3 days

15-21 days

2-10 days (correct)

What is the primary diagnostic test for EHV-1?

Fluorescent antibody Signup and view all the answers

What is the most common age group affected by EHV-1?

Mares 3-9 months pregnant Signup and view all the answers

What is the primary treatment for EHV-1 infection?

Supportive nursing and NSAIDs to control malaise and fever Signup and view all the answers

What is the characteristic of EHV-1 infection?

Sudden and deadly Signup and view all the answers

Which of the following is NOT a clinical sign of EHV-1 infection?

Diarrhea Signup and view all the answers

What is the significance of EHV-1 subtype 1?

Causes abortion Signup and view all the answers

What is the primary vector for the bird/rodent-mosquito life cycle of Venezuelan Equine Encephalitis?

Cedecci Signup and view all the answers

What is the characteristic of the epizootic form of Venezuelan Equine Encephalitis?

Mutation to subtype I with a change in mammalian pathogenesis Signup and view all the answers

What is the common name for EHV-1?

Abortion storm virus Signup and view all the answers

Which of the following is NOT a common clinical sign of Equine Encephalomyelitis?

Diarrhea Signup and view all the answers

What is the most efficient vector for the transmission of flaviviruses?

Culex spp. Signup and view all the answers

What is the typical duration between infection and the onset of neurologic signs in Equine Encephalomyelitis?

9-11 days Signup and view all the answers

What is the primary diagnostic test for Equine Encephalomyelitis?

Clinical assessment Signup and view all the answers

What is the characteristic of the CSF examination in Eastern Equine Encephalitis?

Neutrophilic pleocytosis Signup and view all the answers

What is the treatment for muscle tremors and fasciculations in West Nile Virus?

Flunixin meglumine 1.1mg/kg, IV, bid Signup and view all the answers

Which of the following is NOT a flavivirus?

Rabies Virus Signup and view all the answers

What is the geographic distribution of West Nile Virus?

Wide geographic distribution Signup and view all the answers

What is the recommended dose of valacyclovir for treating EHV?

30 mg/kg, PO, tid Signup and view all the answers

What is the primary purpose of doxycycline in EHV treatment?

Anti-inflammatory properties Signup and view all the answers

What is the effect of corticosteroids on the immune system in EHV treatment?

Immune system suppression Signup and view all the answers

What is the primary method of diagnosis for EHV?

PCR and isolation of virus from nasopharyngeal swabs and blood samples Signup and view all the answers

Which of the following is NOT a type of Equine Arboviral Encephalomyelitis?

Rabies Signup and view all the answers

What is the mortality rate of Eastern Equine Encephalomyelitis (EEE)?

50-90% Signup and view all the answers

What is the primary purpose of administering antibiotics to horses with EHV infections?

To prevent secondary bacterial infection Signup and view all the answers

Which virus is primarily transmitted by mosquitoes of the Culex (Melanoconion) spp?

MADV Signup and view all the answers

What is the life cycle of alphaviruses between?

Birds and rodents Signup and view all the answers

What is the prognosis for horses that remain standing after EHV infection?

Good Signup and view all the answers

Which of the following is NOT a transmission method of Equine Arboviral Encephalomyelitis?

Direct horse-to-horse Signup and view all the answers

What is the primary difference between EHV-1 and EHV-4?

EHV-1 causes abortion, while EHV-4 causes respiratory disease Signup and view all the answers

What is the purpose of vaccination in Equine Arboviral Encephalomyelitis prevention?

Prevention of viral infection Signup and view all the answers

Which of the following is a characteristic of EHV-3?

It is a venereal disease Signup and view all the answers

What is the purpose of vaccinating horses at 5, 7, and 9 months of gestation?

To prevent EHV-1 infection Signup and view all the answers

What is the typical age range of horses affected by EHV-4?

Foals to 3 years old Signup and view all the answers

What is the common finding in the complete blood count (CBC) of horses infected with EHV-5?

Neutrophilic leukocytosis Signup and view all the answers

What is the purpose of the virus-specific PCR test in the diagnosis of EHV-5?

To detect the presence of EHV-5 Signup and view all the answers

What is the prognosis for survival in horses infected with EHV-5?

Approximately 50% Signup and view all the answers

What is the role of EHV-2 in the development of Rhodococcal infection?

It acts as a forerunner that leads to Rhodococcal infection Signup and view all the answers

Study Notes

Equine Encephalomyelitis

Equine Encephalomyelitis is a group of diseases caused by viruses transmitted by mosquitoes, including Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), Venezuelan Equine Encephalitis (VEE), and West Nile Virus (WNV).

Eastern Equine Encephalitis (EEE)

Mosquito-borne disease with a mortality rate of 50-90%
Caused by an alphavirus
Transmitted by mosquitoes, not horse-horse or horse-human
Sylvatic cycle between passerine birds and Culiseta melanura

Venezuelan Equine Encephalitis (VEE)

Mosquito-borne disease with a mortality rate of 50-75%
Caused by an alphavirus
Has two life cycles: enzootic and epizootic
Enzootic cycle involves mosquitoes (subgenus Melanoconion/C. spp)
Epizootic cycle involves several bridge vectors, with horse infection becoming a predominant feature

West Nile Virus (WNV)

Mosquito-borne disease with a wide geographic distribution
Caused by a flavivirus
Has a mortality rate of 35-45%
Transmitted by mosquitoes, not horse-horse or horse-human

Clinical Signs

Neurologic signs occur 9-11 days after infection
Quiet and depressed
Ataxia, wandering, impaired vision, reduced reflexes, circling, inability to swallow, drooling, fever
Paralysis usually followed by death 2-3 days after onset of signs

Diagnosis

Clinical assessment
CSF examination with neutrophilic pleocytosis (count > 50%)
IgM capture ELISA (85-90%); neutralizing antibodies (IgG) are the gold standard
PCR - midbrain and brain stem

Treatment

Supportive nursing care
Management of pain and inflammation
For WNV, flunixin meglumine 1.1mg/kg, IV, bid to prevent muscle tremors and fasciculations

Prevention

Equine viral diseases vaccination
Prevent exposure to other horses attending shows or other equine events

Equine Herpes Virus (EHV)

Species-specific virus with three subfamilies: alpha, beta, and gamma
9 documented strains, but only 5 affect domestic horses
Only EHV1, EHV3, and EHV4 commonly cause diseases in horses

EHV-1 (α)

Subtype 1 of EHV1
Causes rhinopneumonitis (respiratory form), abortion, birth of weak foals, peracute vasculitis, and neurological disorders
Most important viral cause of abortion in horses
Can be sudden and deadly
High temperature, "fulminating" respiratory disease

EHV-3 (γ)

Venereal disease
Equine Coital Exanthema
Rare but important
Self-limiting
Characteristic lesions on genitalia of stallions and mares

EHV-4 (α)

Subtype 2 of EHV1
Respiratory infection only ("Rhino"); rhinopharyngitis and rhinotracheitis
Non-fatal, rarely results in abortion
Severe, widespread outbreaks in young horses; foals → 3 years old in training

EHV-2 and EHV-5 (γ)

"Ubiquitous" but rarely causes disease
Found in nearly 100% of healthy foals
Can cause problems in the following diseases:
- EHV2 - Herpetic keratoconjunctivitis in young foals; may act as a forerunner that leads to Rhodococcal infection (through immune suppression)
- EHV5 – equine multinodular pulmonary fibrosis (EMPF); in middle-aged horses

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Description

This quiz covers the transmission and life cycle of flaviviruses, including VEE and WNV, and their role in causing encephalitides. It also explores the role of vectors and hosts in the spread of these diseases.