Ross River Fever and other viruses


The eastern saltmarsh mosquito – image Wikimedia CC

There is an ongoing household discussion here about the sliding screen door, which, if left open, exposes us to mosquitos, potentially carrying Ross River Fever. (It’s tempting to leave the door open so the dog, who lacks an opposable thumb, can get in and out at will. Ed)

Of course, we could just as soon be bitten when outside for a multitude of reasons (gardening, watering, chopping firewood, walking the dog at dusk). Nevertheless, I can tell if the screen door has been left open for a period as mosquitos the size of bees invade my study. It seems mine is the sort of blood to which mosquitos are attracted. I found that out big time on our caravanning adventures in the Northern Territory and Western Australia. If your blood group is type O or you are mosquito-prone, this article might be of interest.

North Queensland, the Territory and the Kimberley are among the places where one is most likely to be bitten by a mosquito carrying Ross River Virus (RRV). This is a disease for which there is no vaccine and no cure. And, despite common perceptions that it is a tropical disease, RRV can occur anywhere in Australia. An article in our local paper in early May revealed 121 cases were reported in the Darling Downs Health region in the March quarter. This is considerably higher than the norm (67 cases a year).

Condamine Medical Centre Dr Lynton Hudson told the Warwick Daily News his concern about Ross River Fever was that some patients may not come in for a physical consult due to COVID-19 fears.

As you’d expect, several years of drought followed by a late wet season, contributed to increased numbers of the southern saltmarsh mosquito, the type most likely to carry the virus. Complicating this year’s cycle is a mild autumn, which means mosquitos are still out and about, particularly at dawn and dusk.

As it happens, a member of our inner circle has recently been diagnosed with RRV, which started with a hives-like rash and a temperature. Fearing something dreadful like Lupus, she went to the local GP who, after some tests, diagnosed Ross River Fever. Stage two of the disease is swollen joints accompanied by arthritic pain and fatigue.

The condition is also called polyepidemic arthritis. Our friend was confined to bed for a few days until the anti-inflammatory medication started to kick in. She told me the arthritic pain was most intense in her knees, feet and ankles. The arthritis extended to her right wrist and finger joints, making it difficult to grip and lift when carrying out domestic chores like cooking

“I also felt extremely fatigued – so if I overdo it in the garden or something, I pay for it the next day.”  

Her GP said there was not much she could do but ‘ride it out’ – easy to say when you are not the one home schooling three kids.

Every year, 3,000 Australians will develop RRV symptoms, which can last from six weeks to three months or longer and leaves patients with a risk of relapse or recurrence. RRV was first discovered in 1959 and named after the Ross River, which runs through Townsville. While people are more at risk of developing RRV if they live in humid regions around rivers, lakes and marshlands, the disease can be found anywhere in Australia. Some large marsupials, including kangaroos, act as an intermediary host.

Depending on weather cycles (drought followed by floods will do it), some years are worse than others. In 2014-2015, RRV cases more than doubled to 6,371.

Ross River Fever is one of a half-dozen viruses carried and spread by mosquitos, including Dengue Fever, Barmah Forest Virus and the lesser known Japanese Encephalitis.

Although RRV is not fatal or contagious, it is one of many notifiable diseases in Australia, with each State and Territory having its own parameters around notification. Included on the list is the bat-borne Lyssa virus, which can be caught by someone who is bitten or scratched by an infected bat.

There is no vaccine for RRV and unlikely to be one in the medium-term as the world’s scientists and epidemiologists are focused on finding a vaccine for COVID-19. Nor is there a vaccine for the mosquito-borne tropical disease, malaria. Mainland Australia is free of the disease; nevertheless 437 malaria cases were reported between 2012-13 and 2016-17. Cases were linked to people returning from a malaria-prone region.

Now that we are all in a state of heightened awareness about infectious diseases, we should perhaps remind ourselves of those not yet eradicated. Tuberculosis is one such illness – prevalent in third-world countries but contained in Australia to fewer than five cases in every 100,000 people. Tuberculosis or TB is primarily a disease of the lungs, although it can be systemic. It can be treated with medication, but patients need to be isolated, as it is extremely contagious.

While Australia aspires to a pre-elimination tally of one person per 100,000 by 2035, the incidence of TB is six times higher in the Indigenous Australian population. Legitimate cross border movements between PNG and the Torres Strait by traditional inhabitants unavoidably pose some risk of TB spreading in the Torres Strait Protected Zone.

Now that you are all feeling psychologically contaminated, the good news is the pre-elimination TB target (1 case per 100,000 by 2035), has already been met in the Australian-born population, who represent 72% of the total. A report by the Department of Health states that the incidence of TB has been ‘low and stable’ since 1986.

The point is, now that so much research capability is being focused on a COVD-19 vaccine (or cure), there a danger of being distracted from developing vaccines for other viruses, which, if not life-threatening, impose a serious burden on the lives of those afflicted.

The report, Mosquito- Borne Diseases in Queensland 2012-2017, may not appeal as bed-time reading in this time of heightened awareness of human frailties. So I will save you the chore and summarise a few statistics. For example, almost 14,000 people picked up RRV in the five years from 2012-13 and 2016-17.  There were 3,986 reported cases of Barham Forest Virus, one of a small group of Alphaviruses including RRV and Dengue. There were 1,895 cases of Dengue fever in the same five-year period. Dengue is like a form of the flu. Most people recover in a week and fatalities are rare. In Australia, Dengue is confined to Far North Queensland, so cases diagnosed elsewhere are usually traced to a recent visit to FNQ or places where the disease is prevalent (Africa and South America). As for Japanese Encephalitis, which I referred to at the start, only three cases were recorded between 2012 and 2017.

As has been the case with COVID-19, we look to New Zealand for an intelligent response. The NZ Department of Health identified the RRV-carrying southern saltmarsh mosquito as a threat back in 1998. Over the next 11 years, with the help of the Ministry of Agriculture and Fisheries, the imported mosquito species was eradicated from New Zealand. I feel safe in using the word ‘consequently’ to report that there have been no reported cases of Ross River Virus acquired within New Zealand since September 2006.

New Zealand scored a world first by snuffing out the little Aussie biter and RRV over a decade, possibly because there are no kangaroos to act as incubators. Having said that, did you know there are two species of wallaby in NZ (Kawau Island, Rotorua and southern Canterbury)? Anyway, I reckon Australia should send a delegation to talk to the people who eliminated the saltmarsh mozzie. Like, tell us how to do it, Bro. (If that’s the case, the kangaroos should start feeling pretty nervous. Ed)

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