News that a worm once considered a rare occurrence in Australia has been discovered in more than 60 per cent of wild dogs in parts of the country should not be a reason for domestic and working dog owners to panic, according to a Charles Sturt University researcher.
While he doesn’t believe domestic dogs are infected to a similar extent as their wild counterparts, saying the veterinary fraternity would be aware of it, the scientist says further research is needed to be sure, and is sounding a precautionary warning for dog owners to be on the lookout for tongue worms in the nasal cavities of their animals.
And while most of the research has taken place in southern New South Wales and the Victorian High Country, it was a jar of worms that had crawled out of the nose of a wild dog shot in the Roma district a dozen or more years ago that alerted scientists to the possibility of higher infection rates than previously thought.
A conversation with a colleague, Dr Shokoofeh Shamsi, about research on tongue worms in Iran, prompted CSU senior research fellow in parasitology, Dr David Jenkins to recall the unidentified worm specimens he had been sent from Lee Allan in Queensland.
He put them under a microscope and identified them, which led to a 2015 study that found 60 per cent of wild dogs and about 15 per cent of foxes in areas of New South Wales and the ACT were infected with the adult stage of the Linguatula serrata parasite, which causes considerable damage to the lining tissues of dog’s noses.
The study, undertaken with Dr Shamsi and honours students Kate McSpadden and Sara Baker, also found the intermediate stage of the parasite infecting lymph nodes in up to 20 per cent of cattle examined in areas where wild dogs would also be living.
“Wild dogs were most commonly infected with up to 17 parasites removed from a single animal,” Dr Jenkins said. “To say that this is a significant finding would be an understatement.”
While only 37 dogs were tested for the parasite, 25 were infected, “an alarmingly high number”, especially as Australia was thought to be virtually free from the worm.
Tongue worms, considered a problem in places such as Africa, China and the Middle East, had been reported only 10 times in the last 200 years in Australia, and were not registering on alert radars before this study.
“This recent study, however, now clearly demonstrates that tongue worm is common in Australian wildlife so we need to start being on the look-out for it in our pet dogs as well,” Dr Jenkins said.
The adult worms have large hooks that damage the nasal mucosa and cause sneezing, breathing difficulties, restlessness, increased nasal secretions, nose rubbing, snoring and blood-stained nasal discharge.
Dr Jenkins is also keen to examine the animals that wild dogs most commonly eat – wallabies and rabbits – to see if they also act as an intermediate host containing the nymphal stage of the parasite.
The worms can’t be passed from infected wild dogs to domestic dogs – they have to go into grass-eating animals first – but if working dogs are eating rabbits that haven’t been gutted, or feeding on wallaby carcases, Dr Jenkins said there was a chance worms could be picked up that way.
There is currently no recommended treatment for either the adult or the nymphal stages and the adults can survive for up to 15 months in the nose of an infected animal.
Dr Jenkins is keen to hear from anyone who has a dog often rubbing its nose and seeming agitated, and can be contacted at firstname.lastname@example.org.
Dog density of concern
The Traprock Wild Dog Group in southern Queensland is one of those reacting with concern to news that tongue worms are present in wild dogs in much greater numbers than previously thought.
Spokesman Bruce McLeish said dog owners in fringe urban areas such as his location could probably consider themselves at risk of infection through an intermediate host because of the close proximity of wild dogs, in ever-growing numbers.
Bruce and his wife Angela are seeing what they describe as an “explosion” in dog numbers, saying they have caught 15 wild dogs, 10 of them bitches, on their 2800ha property between Warwick and Inglewood since January.
“If you do your sums, if each of those 10 bitches had three surviving bitch pups, and they had 10 bitches, that multiplies to 40.
“Within four years that’s 2600, without counting the male dogs.
“That’s why we’re where we are now. Once upon a time, wild dogs were taken out of the landscape consistently but they’re not now.
“This news of tongue worms is like hydatids. It’s another thing that reinforces to the government that we’ve got to get wild dogs under control,” he said.