Human Hendra Virus Encephalitis Associated with Equine Outbreak, Australia, 2008

EID Journal Home > Volume 16, Number 2–February 2010

Volume 16, Number 2–February 2010
Research
Human Hendra Virus Encephalitis Associated with Equine Outbreak, Australia, 2008
Elliott G. Playford, Brad McCall, Greg Smith, Vicki Slinko, George Allen, Ina Smith, Frederick Moore, Carmel Taylor, Yu-Hsin Kung, and Hume Field
Author affiliations: Pathology Queensland, Brisbane, Queensland, Australia (E.G. Playford); University of Queensland, Brisbane (E.G. Playford, B. McCall); Forensic and Scientific Services, Brisbane (G. Smith, I. Smith, F. Moore, C. Taylor); Brisbane South Public Health, Brisbane (B. McCall, V. Slinko); Princess Alexandra Hospital, Brisbane (E.G. Playford, G. Allen); and Department of Primary Industries and Fisheries, Brisbane (Y.-H. Kung, H. Field)

Suggested citation for this article

Abstract
A recent Hendra virus outbreak at a veterinary clinic in Brisbane, Queensland, Australia, involved 5 equine and 2 human infections. In contrast to previous outbreaks, infected horses had predominantly encephalitic, rather than respiratory, signs. After an incubation period of 9–16 days, influenza-like illnesses developed in the 2 persons before progressing to encephalitis; 1 died. Both patients were given ribavirin. Basal serum and cerebrospinal fluid levels were 10–13 mg/L after intravenous administration and 6 mg/L after oral administration (isolate 90% inhibitory concentration 64 mg/L). Both patients were exposed to infected horses, 1 during the late incubation period in a horse. The attack rate for veterinary clinic staff exposed to infected horses was 10%. An isolate from this outbreak showed genetic heterogeneity with isolates from a concurrent, but geographically remote, outbreak and from previous outbreaks. Emergence of Hendra virus is a serious medical, veterinary, and public health challenge.

The genus Henipavirus of the family Paramyxoviridae contains 2 recently described viruses, Hendra virus and Nipah virus, whose natural reservoir is fruit bats of the genus Pteropus (1). Hendra virus has caused serious respiratory infections in horses and respiratory and neurologic infections in humans. After 2 Hendra virus outbreaks in 1994, which involved 22 horses and 3 humans (2,3), a total of 7 additional equine infections and 1 human infection were documented up to 2008 (4,5); all occurred in coastal Queensland and northern New South Wales in Australia. Of the 4 persons with documented Hendra virus infection, 2 recovered from influenza-like illnesses (ILIs) (2,5) and 2 died, 1 from respiratory failure (2) and 1 from encephalitis 13 months after initial aseptic meningitis (3). The estimated incubation period in humans of 7–8 days was based on these cases.

The Outbreak
In early July 2008, a veterinary practice (clinic) in Thornlands, Queensland, was quarantined after 2 acutely ill horses were provisionally diagnosed with Hendra virus infection. Four horses eventually died from the infection, and another was humanely killed after it recovered, in accordance with established national veterinary practice (6). In contrast to previous equine outbreaks, horses in this outbreak showed predominantly neurologic (ataxia, head tilt, limb paresis), rather than respiratory, symptoms (1). We report 2 additional human cases of Hendra virus encephalitis, 1 fatal, in veterinary workers associated with this equine outbreak.

Patient 1
A 33-year-old man (equine veterinarian) at the clinic had a 2-day history of an ILI (fever, myalgia, and headache) in mid-July 2008. Clinical examination showed only a fever (38°C); mild neutropenia (0.7 × 109 cells/L) and thrombocytopenia (79 × 109 cells/L); a normal chest radiograph; and negative PCR results for respiratory viruses, including influenza, on a nasopharyngeal aspirate (NPA) specimen. Hendra virus RNA was detected by reverse transcription–PCR (RT-PCR) in serum and NPA specimens. The patient remained clinically well and showed defervescence on day 4 of illness.

By day 5, mild confusion, ataxia, bilateral ptosis, but no other neurologic signs, developed. Magnetic resonance imaging (MRI) showed multifocal (bilateral, cerebral, cortical, right pontine, scattered white matter) hyperintense lesions on T2 flair images associated with evidence of infarction on diffusion weighted images. A cerebrospinal fluid (CSF) sample had a leukocyte count of 4 × 106 cells/L, a protein level of 600 mg/L, and a glucose level of 3.7 mmol/L; Hendra virus RNA was detected by RT-PCR. An electroencephalogram (EEG) showed bilateral high-voltage slow waves but no epileptiform activity. He was treated with intravenous ribavirin (30 mg/kg initial dose, then 15 mg/kg every 6 h for 4 days, and 8 mg/kg every 8 h thereafter); enteric aspirin (100 mg/day); and because of progressive confusion and ataxia, intravenous dexamethasone (4 mg every 6 h).

Suggested Citation for this Article
Playford EG, McCall B, Smith G, Slinko V, Allen G, Smith I, et al. Human Hendra virus encephalitis associated with equine outbreak, Australia. Emerg Infect Dis [serial on the Internet]. 2010 Feb [date cited]. http://www.cdc.gov/EID/content/16/2/219.htm

DOI: 10.3201/eid1602.090552



abrir aquí para acceder al documento CDC EID completo del cual se reproduce un 15%:
http://www.cdc.gov/eid/content/16/2/219.htm