Tuesday, July 29, 2014

Why pet food and water bowls should be washed regularly

Tawny frogmouths. They're cute, but they're increasingly seen with rat lungworm -
a parasite that can infect companion animals and people too. (NB people don't catch it
FROM tawnys...read on).

SAT had a brief hiatus yesterday as we were recovering from a three-day continuing education adventure (two days with medicos at the Zoonoses conference backed up with a day of oncology with Dr Sandra Nguyen at the Animal Referral Hospital). It was one of those weekends where one might be moved to utter the phrases “this is awesome” and “my brain hurts” in the same conversation (probably with oneself after three days of lectures).

Over the next weeks I will be sharing some things I learned, in no particular order, as one thing emphasised in the Zoonoses conference is the need to share information.

(And for anyone who might not know, “zoonoses” are diseases that can be shared between humans and animals. Rabies would be a good example, but so would Q-fever). By the way, the sharing can go in both directions.

Dr Derek Spielman, a lecturer in pathology at the University of Sydney and also a wildlife vet, talked about angiostrongylosis, a condition caused by the nematode parasite Angiostrongylus cantonensis (known as the rat lungworm).

This causes very nasty, horrible disease in humans, wildlife and companion animals. You may remember some years ago a young gentleman was hospitalised with a bizarre parasite after being dared to eat a slug (well, it wasn’t the daring that caused his predicament – it was acting on the dare)(read the story here).

(To me the most interesting thing about this case is that it wasn’t the FIRST TIME someone had contracted the disease from a dare – which makes me think that the Department of Health should be looking into the epidemiology of dares as I imagine they’re also a risk factor for other conditions like trauma as well – but I digress).

The definitive host for the rat lungworm is, as you might guess, the lung of the rat.

They sit in the rat lungs, lay their eggs in the blood, and then these eggs (L1) pop off into the airways, up the trachea (windpipe) and get swallowed where they are digested and escape into faeces. The ova in faeces are very active and as soon as a snail or slug comes along they are able by various mechanisms I won’t discuss here to penetrate the foot of the snail. Within the snail they moult a couple of times, first into L2 and then into L3 stages, and then these are meant to be ingested again by rats.

Once ingested the L3 larvae penetrate the intestinal wall of the host, spreading via the blood and lymphatic system to the brain and spinal cord where they mature into L4 and L5s before heading back into the venous system and into the pulmonary vessels. But in people and other accidental hosts, the combined effects of movement (basically the larvae munch along their path) and inflammation leads to neurological signs, characterised by marked pain and meningitis in humans and animals if they’re unfortunate enough to become “aberrant hosts”.

In Australia, most non-dare related infections are associated with either babies or toddlers that pick up slugs and snails and eat them, or eating unwashed salad vegetables (be particularly careful with back garden and organically grown fruit and vegies where molluscicides aren’t used). 

Sanchez enjoys a salad. Never mind the pirate hat.
[A note for the cavy enthusiasts: guinea pigs aren't particularly susceptible to clinical disease, but as hell-bent salad eaters this might be something they've had to evolve? (As an aside within an aside, I learned that the oncology drug l'asparaginase was first isolated from guinea pig serum, and later from E. coli carried by guinea pigs). I prefer to wash their vegies regardless.]

There is also a potential to ingest the parasite in poorly cooked prawns from South-east Asia (another reason we should be doing all we can to promote biosecurity not only here but overseas – the incursion of an exotic slug in one country can have health implications internationally).

But Dr Spielman also added that pet owners should be very careful when feeding pets outside, as slugs and snails are attracted to pet food.

Dog and cat food bowls should NEVER be left out where they can be exposed to snails or slugs – dogs and cats will often ingest slugs with the food, but as veterinarian and rat lungworm expert Ken Mason added, they will often also just eat slugs and snails that happen to be in the vicinity. Rather like you and I might eat an olive if we see one.

Possums are attracted to pet food left outside. If that pet food is attracting slugs or snails, there is potential for transmission of rat lungworm.
Dog and cat food is also a temptation for local wildlife so should not be left out overnight, as possums and birds are also susceptible. In fact, there is an increasing number of cases in wildlife which may indicate greater spread of the disease. Wildlife infections are a concern in their own right, but Dr Spielman also argues that wildlife are important sentinels of zoonotic disease (you can read more here).

It has not been proven but there is speculation that some infective larvae might be present in slug and snail trails. Pet food and water bowls should be cleaned daily to minimise the risk.

In other news…

Mick sent us this link on organising care for your pets in the event of your death. It might seem like a bit of a downer to talk about but I’d much rather be prepared than not – just in case. (It would be nice to have $12 million to leave them, like Trouble’s owner – but that certainly upset a few human relatives left behind).

Rachel sent in this link about a chihuahua, born without forelimbs, who is getting around using a set of custom-made wheels. Most dog wheelchairs are made for larger dogs, so the vets have had to use toys to improvise. Surely there’s an engineering student out there willing to have a crack at it?