Aussie virus linked to rabies

by Chris Griffith
Published 17 Nov 1996 in The Sunday Mail


my face


The lyssavirus that killed a 39-year-old Rockhampton woman late on Friday is a brand new form of a very old disease around since the days of the ancient Greek empire.

Lyssavirus is not just one disease, rather seven closely related viruses that attack the nervous system and the brain and cause encephalitis, the most infamous being rabies.

All except the new Australian strain and rabies are confined to Africa. Rabies itself is found in all continents except Australia and Antarctica.

The transmission of the different forms of lyssavirus are similar.

Over the last 50 years, the source of rabies has changed from domesticated animals such as dogs to wildlife, to principally raccoons, skunks, foxes, and bats.

There is wide discrepancy among scientists as to the numbers of rabies deaths world-wide each year. Figures range from 700 to 1,000 to between 40,000 to 100,000, according to the Center for Disease Control and Prevention at Atlanta, Georgia.

The centre says millions are treated for rabies exposure every year - primarily in developing countries.

Unfortunately the much-maligned flying fox, or fruit bat, is responsible for spreading many different strains of lyssavirus.

A flying fox can fly long distances while harbouring the virus in its salivary glands without any fatal infection to itself.

It is therefore not surprising that flying foxes have been detected as carriers of other lethal virus such as equine morbillivirus, which in 1994 killed Brisbane horse trainer Vic Rail and 14 horses, and more recently Mackay horse breeder Mark Preston.

Apart from rabies and the unnamed Australian strain, the other forms of lyssavirus include Lagos bat, first isolated in 1956 from the brain of a Nigerian fruit bat at Lagos Island. Ten cases have been identified, but no known human deaths.

Mokola, first isolated in Nigeria in 1968, resulted in two human infections, and Duvenhage, also transmitted by bats, caused one human death in South Africa.

The final two forms of lyssavirus are European bat Lyssavirus 1 and 2, found in Europe and Switzerland. Both have caused human deaths. The second form was isolated in Finland in a bat biologist who had died of rabies.

Despite Friday's death in Rockhampton, Queensland Health is warning against any belief that the virus is in the league of rabies.

Queensland chief Health Officer Diana said the virus was identified in fruit bats in May while scientists were examining the same bats for equine morbilivirus.

Symptoms of the new strain in humans included numbness and weakness in limbs after being scratched or bitten, vomiting, headaches, and fever.

Despite pleas for calm, health authorities are taking no risks.

State Health Minister Mike Horan says people should avoid flying foxes, wear gloves when handling them, and wash any fruit picked from gardens where flying foxes have visited.

Dr Lange said large quantities of rabies vaccine had already been flown to Australia, and between 30-40 people including flying-fox handlers have been vaccinated so far.

She said the Centre for Disease Control researchers in Atlanta had already found that the standard rabies vaccine "gave a significant degree of protection" against the new strain.

"Another 30-40 people across Queensland and Northern NSW who have had expose to flying foxes are being tested, and may require vaccine depending on the results."

This treatment is not cheap.

A course of rabies immunoglobulin and five doses of vaccine over 4 weeks typically exceeds US $1,000.

In New Hampshire in the US recently, the discovery of a kitten with rabies led to 650 people being treated for an estimated US $1.5 million.

The bill to US authorities for controlling rabies deaths to an average of one or two per year is between US $230 million and US $1 billion annually.

The full extent and cost of any program to eliminate the Australian strain is unknown.

Already two task forces have been set up - a Commonwealth group which is examining both the equine morbillivirus and lyssavirus outbreaks, and a Queensland task force headed by Dr Lange.

The state task force includes Dr Tony Allworth, the director of infectious diseases at the Royal Brisbane Hospital, epidemiologists, Queensland health officials, Department of Primary Industry representatives, and members of the national task force.

Dr Lange said the state committee would meet tomorrow to organise the distribution of vaccine, examine costs, and would prepare a paper for Commonwealth authorities on priorities for research.

Strategies to target high risk groups such as flying fox handlers, animal laboratory personnel, horticultural workers, and veterinarians would be developed.

If the rabies strain of lyssavirus is any guide, nothing can be taken for granted.

US authorities say transmission is possible in caves with thousands of bats with rabies in their saliva - without any direct contact between bat and human through "aerosol" transmission.

And the incubation period can be from 6 days up to seven years - due to the varying ability of the virus to replicate, and its slow spread along nerves.