Macacine alphaherpesvirus 1

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Background

  • Also known as macacine herpesvirus 1, macacine alphaherpesvirus 1, cercopithecine herpesvirus 1, CHV-1), herpes B virus, monkey B virus, herpesvirus simiae and herpesvirus B

History

  • First described in 19331, named 'B' for the first patient's initial

Microbiology

  • Double-stranded DNA virus
  • Alphaherpesvirus, in the same family as HSV

Epidemiology

  • 50 documented cases worldwide, in people who handle macaques or their lab samples

Pathophysiology

  • Virus replicates locally at the site of inoculation, then spreads from peripheral nerves to spinal cord to brainstem to brain

Clinical Manifestations

  • Typically via bite or scratch of macaque monkey
    • Asymptomatic or similar presentation to HSV in the monkey
    • Seroprevalence reaches 100% in some populations of macaques
  • Incubation period 5 to 21 days (range 2 days to 5 weeks)
  • Three clinical forms:
    • Flu-like illness followed by CNS symptoms
    • Local symptoms (itching, tingling, numbness, or pain) at the inoculation site, with or without vesicular rash and regional lymphadenopathy
    • Peripheral or central nervous system symptoms, with meningismus, vomiting, confusion, cranial nerve palsies
    • There has been a single case of reactivation 10 years after last macaque exposure2
  • Eventually progresses to global encephalitis, seizures, paralysis, and respiratory failure
  • Mortality 70-80% if untreated

Diagnosis

  • Serology, with acute and convalescent (3 to 6 weeks) titres, looking for a 4-fold rise
    • Seroconversion may be delayed if on acyclovir, so should be repeated at 12 weeks
    • Done at NML or sent out to Georgia State University
  • Viral culture is possible but not done routinely
  • PCR is available for swab, tissue, blood, and CSF
    • Sent out to Georgia State University
    • In autopsy, send right and left trigeminal ganglia or the sacral dorsal root ganglia

Management

Initial management

  • Local wound irrigation, flushing for 15 minutes
  • Assess risk:
    • Source of exposure: must be a macaque, as there are no other known hosts. Captive macaques have up to 100% seropositivity, depending on age.
    • First aid: risk decreases with flushing for 15 minutes
    • Type of wound: risk is higher with deeper wounds (e.g. bites) and larger area, as well as with high-risk areas (head, neck, or torso)
  • Consider sending wound swab and baseline serology
    • CDC recommends against routine swabbing
    • Contact the lab, especially if you will be sending PCR

Treatment of diagnosed infection

  • Acyclovir 12.5 to 15 mg/kg IV q8h
  • Alternative: ganciclovir 5 mg/kg IV q12h
  • Duration at least 2 weeks and until resolution of symptoms and 2 negative cultures

Postexposure prophylaxis

  • Recommended for everyone with skin or mucosal exposure to a captive macaque, and there was inadequate cleaning (deep puncture bites are assumed to not be adequately cleaned)
    • Should be started within hours
    • First-line treatment: valacyclovir 1 g po tid
    • Alternatives: acyclovir 800 mg po 5 times daily, or famciclovir 500 mg po 5 times daily
    • Continue for 2 weeks (some recommend up to 5 weeks, the longest known incubation period)

References

  1. ^  F. P. Gay, M. Holden. Isolation of a Herpes Virus from Several Cases of Epidemic Encephalitis.. Experimental Biology and Medicine. 1933;30(8):1051-1053. doi:10.3181/00379727-30-6788.
  2. ^  Joshua Fierer. Herpes B Virus Encephalomyelitis Presenting as Ophthalmic Zoster. Annals of Internal Medicine. 1973;79(2):225. doi:10.7326/0003-4819-79-2-225.