A case of imported rabies in Aotearoa New Zealand

Rabies is a zoonotic encephalitis caused by viral species within the Lyssavirus genus.¹ Rabies virus (RABV; species Lyssavirus rabies) transmitted from dog bites is the most common cause of human rabies.¹ Rabies is not endemic in Aotearoa New Zealand,² and here we describe Aotearoa New Zealand’s first recorded case.³

Case report

A 48-year-old Filipino man presented to hospital with fever, vomiting and inability to swallow food or fluids (day 3 post-symptom onset). There was no history of an animal bite from the patient (while lucid), or his wife. He worked on a commercial cargo ship and had not disembarked since boarding in the Philippines over 7 months earlier. There were reportedly no animals on board. He had a background of type 2 diabetes mellitus, for which he took metformin and gliclazide.

View Table 1, Figure 1–2.

On examination on the day of presentation (day 3 of illness), he was febrile (38.6°C) and anxious. Initial blood tests showed a neutrophilia and normal C-reactive protein. On day 4 he became increasingly agitated and paranoid, necessitating sedation and intubation for ongoing management. Initial CT and MRI brain imaging were unremarkable (Figure 1). CSF analysis demonstrated a lymphocytic pleocytosis. Routine CSF microbiological investigations and autoimmune encephalitis screen were negative. He received empirical broad-spectrum antimicrobials to cover bacterial meningitis and viral encephalitis, and a 5-day course of methylprednisolone (1g/day) for a possible autoimmune cause. On day 5 he developed significant autonomic instability with alternating tachypnoea and apnoea, and episodes of extreme hypertension interspersed with hypotension.

Urine, serum and CSF collected on day 8 were tested with a pan-Lyssavirus genus reverse transcription real-time PCR, which was negative. Day 10 serum was negative for RABV IgG. The patient became progressively obtunded from day 14, with marked hypersalivation (saliva losses exceeding 1L/day). Day 15 serum demonstrated RABV IgG seroconversion. Three saliva samples and a nuchal (nape of neck) skin biopsy collected on days 16–17 all tested positive for Lyssavirus genus RNA by PCR. The detected Lyssavirus was confirmed as RABV by sequencing (Figure 2). His obtundation progressed to absent respiratory drive and multi-organ failure, and he died on day 23 post-symptom onset. The patient was managed with infection prevention and control (IPC) standard precautions, with appropriate personal protective equipment (PPE) used when staff were at risk of contact with infectious bodily fluids.

Discussion

When RABV from saliva of an infected animal contacts non-intact skin (via a bite), it enters peripheral motor nerves and travels to the spinal cord (typical incubation period ~20–90 days).¹ Dorsal root ganglia infection produces inflammation, leading to fever, pruritus and paraesthesia (prodromal phase, ~1–2 days).¹ From the spinal cord, RABV rapidly disseminates within the central nervous system (CNS) to produce an acute neurological phase (~1–4 days) with an encephalitic (agitation, hypersalivation, hydrophobia and autonomic dysfunction) or paralytic clinical picture (muscle weakness, paralysis and drowsiness).¹ Development of symptoms is almost invariably followed by death within 1–2 weeks, which may be extended by ICU care.¹

Following CNS dissemination, the virus spreads outwards via parasympathetic nerves to multiple sites, including skin sensory nerves and salivary glands to facilitate onwards transmission via saliva.¹ Optimal ante-mortem investigations reflect this pathophysiology: saliva specimens (containing excreted virus) and a nuchal skin biopsy (skin nerves close to the CNS) for PCR testing.¹ Our patient evidently lacked prior immunity from rabies immunisation, making paired serology useful in this case for demonstrating RABV IgG seroconversion. Within Aotearoa New Zealand, rabies serology is currently available through Awanui Labs (formerly Labtests), Auckland and Canterbury Health Laboratories, Christchurch.^7,8 Rabies PCR testing is not currently available in Aotearoa New Zealand and can be referred to the Victorian Infectious Diseases Reference Laboratory (VIDRL) in Melbourne, Australia.⁹

The patient developed symptoms after 7 months at sea without shore leave. As demonstrated by this case, the long incubation period, which can extend for several years in rare cases,¹⁰ makes eliciting an animal bite history challenging. This means compatible symptoms and prior travel to a rabies endemic area may be the only clues to the diagnosis. Rabies is highly endemic in the Philippines,⁶ and our patient was likely infected there before embarking.

Rabies is transmitted when infectious bodily fluids (saliva, tears, respiratory secretions) or CNS tissue comes into direct contact with non-intact skin or mucous membranes (eyes, nose or mouth).¹¹ Blood, urine and faeces are deemed non-infectious, and rabies cannot be transmitted via objects/surfaces.¹¹ Standard precautions should be used for care of all patients,¹² and are considered appropriate for the care of patients with suspected or confirmed rabies.^2,11 This means that staff that are likely to come into contact with infectious bodily fluids should wear gowns, goggles, masks and gloves, particularly when performing activities such as intubation and suctioning.¹¹ Post-exposure prophylaxis is only warranted following a direct exposure as described above, or when a contact has been bitten by a case.² Care of a patient with suspected or confirmed rabies can generate anxiety among attending healthcare workers, especially in non-endemic settings. Anxiety can be managed through staff education regarding which bodily fluids are infectious, reinforcing the value of correct standard precautions for all patients and reassurance that standard precautions are effective in preventing rabies transmission and that there has never been a case of human-to-human rabies transmission from a patient to a healthcare worker (human-to-human transmission has only occurred in the setting of organ/tissue transplantation).¹¹