Contents
- Chikungunya_virus: a re-emerging threat_
- Bluetongue virus, climate change and Australia
- Hendra virus, ecological change and a new threat
- The Biosecurity Risk Intelligence Scanning Committee_
Chikungunya virus: a re-emerging threat
Few Australians have heard of chikungunya (pron chick-un-gun-ya).
But over the last few years it has spread around the Indian Ocean infecting millions of people and killing many hundreds.
It is now spreading into Europe. Some Australian mosquitoes are capable of spreading the virus.
Is chikungunya an emerging threat to Australia?
Chikungunya is a vector borne viral disease most commonly spread by the Yellow Fever mosquito (Ae aegypti), which is also responsible for spreading dengue virus.
Both viruses may be transmitted by the Asian tiger mosquito (Ae albopictus). The virus causes a syndrome of rash, fever, joint pain, and headaches, with joint pain being the predominant symptom.
Outbreaks of chikungunya occurred in Africa and Asia in the 1960s to the early 1980s and were relatively rare until outbreaks began in Indonesia in 1999 and the Indian Ocean island of Réunion in 2005.
On Réunion, Chickungunya infected 30% of the population (160,000 cases) causing 237 deaths.
Outbreaks have escalated around the Indian Ocean.
In India more than 1.25 million cases have been reported. In some areas attack rates have reached up to 45%.
There have been 60,000 cases in Sri Lanka with 160 deaths.
The virus is currently causing disease in Indonesia, Malaysia and Singapore
In 2007, the virus spread to the Ravenna district of Italy, purportedly transmitted by Ae albopictus. Two hundred people were infected with one death. The real significance of the outbreak was that the virus was present in local mosquitoes.
New phylogenetic strains have been implicated in a more virulent clinical picture with competent transmission by Ae albopictus.
Australia has had cases of chikungunya in returned travellers. The virus has not established itself in Australian mosquitoes. However, we do have mosquitoes that are capable of transmitting the virus, in particular Ae aegypti and Ae Albopictus (the Asian tiger mosquito).
The mosquito Ae aegypti is currently confined to Queensland and the Torres Strait. In 2004 it appeared in Tennant Creek in the Northern Territory.
In a concerted effort costing over $1 million the mosquito was eradicated from the Northern Territory.
In 2005, the Asian tiger mosquito made its first appearance in Australia on several islands in the Torres Strait. An eradication program is underway in the Torres Strait, although the appearance of new strains of the mosquito indicates new incursions and a considerable challenge ahead.
The Australian Biosecurity Cooperative Research Centre has held forums to consider research priorities for chikungunya virus.
A study of Australian mosquitoes earlier this year confirmed that mosquitoes found in most coastal areas may transmit chikungunya virus.
The CRC recognises chikungunya as an emerging threat.
The Biosecurity Risk Intelligence Scanning Committee (BRISC) will monitor chikungunya spread and provide CRC partners with assessment of risk to Australia and potential research applications to further understand the risk and optimise intervention strategies.
WHO information
(from http://www.searo.who.int/en/Section10/Section2246.htm)
Chikungunya Fever, a re-emerging disease in Asia
Chikungunya fever is a viral illness that is spread by the bite of infected mosquitoes. The disease resembles dengue fever, and is characterised by severe, sometimes persistent, joint pain (arthritis), as well as fever and rash. It is rarely life-threatening. Nevertheless, widespread occurrence of diseases causes substantial morbidity and economic loss
Epidemiology
Epidemics of fever, rash and arthritis, resembling chikungunya fever have been recorded as early as 1824 in India and elsewhere. However, the virus was first isolated between 1952-1953 from both man and mosquitoes during an epidemic of fever that was considered clinically indistinguishable from dengue, in the Tanzania.
Chikungunya fever displays interesting epidemiological profiles: major epidemics appear and disappear cyclically, usually with an inter-epidemic period of 7-8 years and sometimes as long as 20 years. After a long period of absence, outbreaks of CHIK fevers have appeared in Indonesia in 1999.
Chikungunya in Asia (1960-1982)
Between 1960 and 1982, outbreaks of chikungunya fever were reported from Africa and Asia. In Asia, virus strains have been isolated in Bangkok in 1960s; various parts of India including Vellore, Calcutta and Maharashtra in 1964; in Sri Lanka in 1969; Vietnam in 1975; Myanmar in 1975 and Indonesia in 1982.
Recent occurrences of chikungunya fever
After an interval of more than 20 years, chikungunya fever has been reported from several countries including India, and various Indian Ocean islands including Comoros, Mauritius, Réunion and Seychelles.
Chikungunya fever in India
Till 10 October 2006, 151 districts of eight states/provinces of India have been affected by chikungunya fever. The affected states are Andhra Pradesh, Andaman & Nicobar Islands, Tamil Nadu, Karnataka, Maharashtra, Gujarat, Madhya Pradesh, Kerala and Delhi.
More than 1.25 million cases have been reported from the country with 752,245 cases from Karnataka and 258,998 from Maharashtra provinces. In some areas attack rates have reached up to 45%.
Chikungunya and dengue fevers
The clinical manifestations of chikungunya fever have to be distinguished from dengue fever. Co-occurrence of both fevers has been recently observed in Maharashtra state of India thus highlighting the importance of strong clinical suspicion and efficient laboratory support.
Laboratory Diagnosis
The clinical manifestations of chikungunya fever resemble those of dengue fever. Laboratory diagnosis is critical to establish the cause of diagnosis and initiate specific public health response.
Treatment, prevention and control
Treatment
Chikungunya fever is not a life threatening infection. Symptomatic treatment for mitigating pain and fever using anti-inflammatory drugs along with rest usually suffices. While recovery from chikungunya is the expected outcome, convalescence can be prolonged (up to a year or more), and persistent joint pain may require analgesic (pain medication) and long-term anti-inflammatory therapy.
Prevention and control
No vaccine is available against this virus infection. Prevention is entirely dependent upon taking steps to avoid mosquito bites and elimination of mosquito breeding sites.
Role of public health authorities
§ National programme for prevention and control of vector borne diseases should be strengthened and efficiently implemented with multisectoral coordination
§ Legislations for elimination of domestic/peridomestic mosquitogenic sites should be effectively enforced
§ Communities must be made aware of the disease and their active cooperation in prevention and control measures elicited.
Bluetongue virus, climate change and Australia
Every year Australia exports livestock to the value of $600 million.
Access to the markets is dependent upon our national disease status and our ability to demonstrate that the livestock are free from defined diseases. One of these diseases that is increasing in importance is bluetongue.
Spread by biting midges, bluetongue can kill up to 70% of infected sheep. It causes milder disease in cattle.
We don’t have bluetongue disease in Australia’s national sheep flock.
We do have the virus, and the midges that spread it, but fortunately not in sheep growing areas. The midges prefer a warm wet climate and the Great Dividing Range generally separates the midges on the coast from the sheep in the hotter dryer hinterland.
However in Europe, bluetongue has recently spread from the warm wet Mediterranean to the cooler climate of England. Is this a warning for Australia?
Every year Australia exports livestock to the value of $600 million.
Access to the markets is dependent upon our national disease status and our ability to demonstrate that the livestock are free from defined diseases.
Bluetongue is caused by the bluetongue virus.
The virus is spread by a number of species of biting midge.
Bluetongue virus causes serious disease in livestock, particularly sheep. Bluetongue virus has been isolated in many tropical, subtropical and temperate zones and 24 different strains have been identified.
Bluetongue has been observed in Australia, the USA, Africa, the Middle East, Asia and Europe. It is seasonal in the affected countries, subsiding when temperatures drop and hard frosts kill the adult midge vectors.
Bluetongue has been spreading northward in Europe since October 1998, perhaps as a result of global warming, which may promote viral survival and vector longevity during milder winters.
A significant contribution to the northward spread of bluetongue disease has been the ability of different midge species to acquire and transmit the virus. The original midge vector was limited to North Africa and the Mediterranean.
Movement into a new host midge has given the virus the opportunity to spread far more rapidly and widely taking advantage also of global warming.
In August 2006, cases of bluetongue were found in the Netherlands, then Belgium, Germany, and Luxembourg. In 2007, cases of bluetongue were found in the Czech Republic, the UK, Scandinavia and Switzerland. Many of these cases were caused by bluetongue virus strain (serotype) 8.
A puzzling aspect of the spread of bluetongue 8 in northern Europe is the overwintering of the virus. Animals will recover between the end of the midge season in fall and the beginning in spring. So the virus must be surviving either in overwintering midges or infected animals. This is a disturbing change in the pattern of the disease.
Bluetongue virus types 1, 3, 9, 15, 16, 20, 21 and 23 had previously been isolated in Northern Australia cattle. Just recently, type 7 has been isolated.
A combination of climatic, geographical, virus and vector monitoring data that have been gathered over more than 25 years, have allowed Australian veterinary authorities to establish and delineate bluetongue virus free zones, and zones of risk in accordance with international (OIE) guidelines. These zones are now promoted to trading partners to facilitate trade.
The changes in bluetongue in Europe serve as a warning.
With climate change, the distribution of the insect vectors could change in Australia, thus altering the geographical spread of the disease.
The new strains of bluetongue virus also have the potential to replicate in different vectors and behave differently in hosts.
These factors could substantially change the risk profile of bluetongue in Australia.
The Biosecurity Risk Intelligence Scanning Committee (BRISC) will work with partners in collecting and integrating information on bluetongue viruses from Australia and overseas to assess the changing risks the new strains and vectors present to Australia. The analysis will also identify information gaps and research priorities.
Hendra virus, ecological change and a new threat
Today’s wildlife diseases can also become livestock and human disease issues.
The history of the Hendra/Nipah virus complex tragically serves as a reminder that all emerging disease issues need to be taken very seriously.
Hendra virus first emerged in 1994 in Queensland. It caused pneumonia-like illness killing 14 horses and their trainer.
A thousand kilometres away a different kind of illness, one with mainly neurological symptoms killed two horses. The horse owner also became sick, then appeared to get well, but a year later died of encephalitis. The cause of this outbreak was found also to be Hendra virus.
A long hunt for the carrier animal ended when flying foxes were found to be the vector. Subsequently bats were also found to be carrying a rabies-related virus, Australian bat lyssavirus.
There have been nine outbreaks of Hendra affecting horses since. The most recent in August this year, took another human life, that of a veterinary surgeon.
A closely related virus, Nipah emerged in Malaysia in 1999 and led to 105 deaths and the culling of a million pigs.
Bats carry many viruses and have been doing so for years. Sixty species of bats exist between Africa and Australia in series of overlapping territories. Most have evidence of carriage of similar viruses. Why the viruses are emerging now is a key question.
Hendra virus is just one of a number of new lethal viruses emerging from bats in Africa, Asia and Australia. These include Ebola, SARS, Hendra and Nipah.
Bats don’t get sick from most of these viruses but other animals such as the horse not only become sick but enable the virus to replicate to large viral loads enabling transmission to other species.
The bat populations in suburban Brisbane are increasing but overall the bat populations in Australia are decreasing rapidly. For millions of years flying foxes have relied on flowering eucalypts and native fruit trees for food and now these forests and coastal swamplands are being destroyed.
As the flying fox habitat is destroyed the bats get stressed and hungry, their immune system gets weaker, their virus load goes up and a lot of virus spills out in their urine and saliva.
The bats come into the urban areas looking for food.
It is possible also that the flying foxes are protecting their ecological niche. When the balance of their environment is disturbed the virus is their biological weapon to preserve their space. It is a fight for survival.
Five horses died in the last outbreak in August. They had a different clinical picture to previous Hendra-affected horses. The virus from those horses has been shown by the CSIRO Australian Animal Health Laboratory to be a new strain of Hendra. The virus has new variants some more virulent than others. Environmental change is not only causing ancient viruses to emerge, it is putting pressure on them to adapt to be stronger and more lethal.
Nipah
At least eight more outbreaks of Nipah virus have occurred since 1998, all in Bangladesh and neighbouring parts of India.
Originally Nipah caused encephalitis in people. However, in the more recent cases the disease has been respiratory and there has been evidence of human to human transmission.
It is increasingly clear that Hendra virus and Nipah virus are closely related and could be regarded as the Hendra-Nipah complex.
The Biosecurity Risk Intelligence Scanning Committee (BRISC) will look at the ecology of both viruses, and specifically the connections between environmental events and disease emergence.
BRISC will ask the question: what does this mean for other species and in particular what are the implications for humans?
The Biosecurity Risk Intelligence Scanning Committee
In today’s biosecurity world, information is a key commodity…but we have too much of it!
That’s why Australia needs the Biosecurity Risk Intelligence Scanning Committee. It will through the noise to identify the underlying trends in emerging diseases, allowing policy makers and researchers to respond rapidly to developing threats.
There are 7.3 billion searches of 25 billion web pages per month in the US alone; 10 hours of footage per minute uploaded to YouTube. But how is this relevant to biosecurity?
At a time when we need to be prepared to expect the unexpected, as well as to be better prepared to deal with known diseases, the need to extract and synthesise information is greater than ever.
And we need to find better ways to get the right information to the right people in a timely manner to allow them to make the best evidence-based decisions.
The risks associated with disease emergence are increasing. The factors associated with the increasing risk are complex and include climate change, increasing population density, and increased global travel and product movement. Indeed, there is data that suggests that since 1940 there has been a steady increase in new disease events.
Vast amounts of information are already available, more than any one person can manage. The digital age has seen to that. How can we more effectively sift and use this information to be better prepared to respond to disease outbreaks?
The Australian Biosecurity CRC partners represent the broad church of organisations involved in wildlife, livestock and human disease issues in Australia. They have expressed a strong interest in improved forecasting and risk assessment. In response, we are announcing today BRISC – the Biosecurity Risk Intelligence Scanning Committee.
BRISC will directly address the information overload dilemma. A senior project officer working for BRISC will scan the broader biosecurity milieu to identify changes in the national and international environment that will alter the emerging disease risk profile.
BRISC will produce monthly bulletins that integrate, analyse and inform busy professionals and disease managers in the biosecurity sector about these environmental changes. This information will help the Biosecurity CRC identify research questions, determine priorities and identify emerging issues and trends. These bulletins may also help partner organisations respond in the most appropriate manner.
In addition to scanning, BRISC will undertake specific risk assessments addressing emerging disease issues that may affect Australia. A salient example is chikungunya . This is caused by a virus that has caused a large outbreak of disease in the Indian Ocean rim and which has now spread around the Indian Ocean rim and threatens Australia.
Another example is Nipah virus, a virus present in South-East Asia carried by bats that is closely related to Hendra virus.
A further disease which is changing and is of great importance to the livestock industry is bluetongue. Climate change is already affecting the patterns of this disease in Northern Europe.
A structured assessment of the risk of introduction of diseases such as chikungunya, Nipah and bluetongue into Australia is important to Australia. Such assessments will identify research priorities and better prepare our country for disease incursions
Professor John Edwards from Murdoch University, an eminent epidemiologist has agreed to chair the committee which is comprised of people with a range of public health, animal health and wildlife disease expertise.
BRISC will be operational by October 2008. We look forward to working with the committee to improve the management of emerging infectious disease risks to Australia and our region.