What about Worms?

What is the common sense truth about intestinal parasites in dogs and cats in Australia?

Ask yourselves, where do my animals get worms from and what are the effects of using chemicals on my pets and the environment.

Do I need to worry about these things?

This posting arises from queries I field on a daily basis from pet owners wanting to know whether they need to use monthly worming preparations in their cats and dogs.

The short answer is no.

Most products on the market are not going to worry most pets but increasingly I receive reports of animals that get stomach upsets, vomiting and diarrhoea on a periodical basis that coincides with giving monthly tablets or spot on products. There have been reports recently about the onset of aggression in dogs after using certain topical flea products that I feel have some validity and ought to be investigated. Fortunately most of these problems are often shortlived and self limiting but we also need to consider what repeated unnecessary dosing does to them, the environment and to us. Plus, more to the point and in my opinion, they don’t really need it.

Being unable to answer all calls I will outline here what most people want to know and what many vets may have forgotten about endoparasites in cats and dogs.

The key to understanding these issues is knowledge of the lifecycles of the parasites in question and an assessment of individual risk. There are many excellent online references that describe these parasites in detail but they don’t necessarily help you to assess the actual risk to your particular pet.



These are the worms you will most commonly see in puppies and kittens. Roundworms are large worms that can cause serious disease and even death in susceptible, juvenile animals. Eggs ingested from these worms can also cause disease in humans if proper sanitary habits such as hand washing after handling young animals are not observed. In humans these parasites can encyst in organs like the eye and do not mature to adult intestinal worms. These problems occur in unsanitary households and with shared dog/human feeding bowls and practices.images-4

Roundworms are parasites that are dormant in the mother animals’ tissues and cross the placenta before birth of the puppies and via milk in newborn kittens.

The larvae mature after migrating through liver and lungs into large worms inside the intestines and these can kill small animals if the burden is heavy. Fortunately this rarely happens to an alarming extent unless the animals are undernourished, neglected or otherwise compromised by serious environmental parasite contamination. These animals will be coughing, ill thrifty, pot bellied, sorry looking kittens and puppies.

It is very important therefore to guard against roundworm infestation in young animals by using piperazine or another chemical of choice to treat dams and progeny post whelping/queening and fortnightly for a few weeks for optimum results.


It is good practice to continue this monthly to six months of age or beyond. Animals that are older than six months develop resistance to roundworm and it is very rarely a problem in adult animals for two reasons; low exposure risk, unless in a breeding establishment and resistance to the parasite.


The next most common parasite in Victoria in cats and dogs and the most common endoparasite in adult animals is tapeworm.There are two main types of tapeworm in dogs and one in cats.

The most serious is hydatid tapeworm in dogs. The incidence of this disease in Australia is now, fortunately, very low owing to a nationwide education and eradication program in the eighties. This disease also only occurs in dogs that are ingesting raw organs from infested sheep or rabbits that themselves have eaten eggs in the environment from dog faeces. It is a dog/sheep cycle and rabbits and humans and other species (wildlife) can also develop severe cystic disease from ingesting infected dog faeces. This is a disease that anyone living with sheep and feeding sheep offal or fresh wild rabbits to dogs may need to worry about and the rest of us do not. Freezing rabbits or sheep offal before feeding them to dogs will address this problem.


The other tapeworm is more common but less problematic and infests cats and dogs that ingest fleas. Good flea control minimizes this risk. The flea tapeworm is not usually harmful and is easy to see in the faeces of dogs and cats


This parasite occurs in tropical areas of north Australia and is acquired by ingestion of larvae from the environment, skin penetration or via colostrum in suckling puppies. It also has an organ migratory phase and causes anaemia. It can be quite a dangerous disease left untreated in puppies and kittens.images-6

It does not occur in the colder southern areas of Australia but is quite problematic in northern dog communities. The larvae that emerge from infested puppy or kitten faeces can also penetrate human skin and cause skin disease in people. It is easily controlled along with roundworm by adhering to strict hygiene, like picking up after young animals that defecate in the environment. Like many other worms, resistance develops in older animals.


This parasite has a simple soil to animal lifecycle and occurs by ingesting encapsulated eggs in soil. It occurs Australia wide but uncommonly causes severe disease as it is easily identified as a problem. In areas of heavy soil contamination this can be a serious disease owing to it’s persistence and difficulty of eradication.

It can be indicated by the mucousy, bloody or yellow frothy diarrhoea it produces. A faecal examination will reveal whipworm if present.

You will definitely know if your animal has whipworm as colitis symptoms will recur and you may need to use regular prevention if the property is contaminated.


This is a parasite that has successfully established itself if cooler climates of Australia after having been largely a tropical disease.

It is transmitted via bite from a mosquito  that has bitten an infested dog. It can only be transmitted in this manner and only a couple of mosquito species of the many hundreds are capable of transmission.

This reduces the risk of infestation quite considerably, coupled with the fact that it is a very slow disease to develop with many opportunities for the lifecycle to be arrested in robustly healthy dogs or diagnosed early and treated with the range of products now available.

You can check what the prevalence of heartworm is in your area of Australia by visiting disease watchdog

The incidence of heartworm is almost non existent in most regions these days largely because many animals have been taking preventatives for over twenty years and the reservoir of infestation has largely disappeared. Many areas of Australia have never even had a case of heartworm diagnosed.


This worm is a potential problem for cats that hunt and eat birds, rodents and snails that may carry this parasite if they themselves have picked up eggs from cat faeces. Coughing cats should be examined for possible lungworm infestation and moxidectin can treat this disease. It is not common and can be treated or prevented in susceptible cats. Your veterinarian can help determine if this is necessary.


Parasitology was well taught to veterinary undergraduates at Melbourne University in my day and whilst the emphasis was on production animals there was thorough information given about all parasites affecting all domestic species in Australia.

I wonder what Drs Rickard and Arundel, amongst others, are thinking nowadays about the apparent lack of regard in general veterinary practice for the fact that dogs and cats should not ever need ongoing monthly worming treatments with ivermectins, selamectins, moxidectins and their various derivatives. There is an abundance of convenience products available these days that arose originally from the market for monthly heartworm preventatives twenty years ago.

The best thing about these new products is that they can act as treatments as well as preventatives and using them once or twice a year can be a good and practical alternative to using them every month.

We used to be quite concerned about anthelmintic resistance and how we could best preserve efficacy of intestinal worming treatments in food animals by rotating the chemicals to reduce the emergence of resistant strains. Whilst it is accepted that production animals will always have a low level of parasitism it is kept to a healthy minimum by these and other sensible, management practices. In contrast, our domestic pets, cats and dogs and to a lesser extent birds and exotics have always been considered to be most healthy with a zero parasite burden. Parasites occupy a niche in the natural world and arguably cannot be totally eliminated. A healthy balance is what is needed.


In fact, most cats and dogs generally do have a near zero parasite burden depending on where they live and how they are fed and yet we are still encouraged to religiously administer the once a month chemical cocktails that we would never consider taking ourselves.

Convenience rules our world.

After nearly thirty years of feeding these monthly to our dogs, the heartworm and other parasite incidence has understandably declined but who really knows what the environmental impact on soil ecology, our households, our pets or other organisms may ultimately be.

It is no secret that animals that are fed raw meaty bones and evolutionary diets are more likely to have robust immune systems especially if these animals are not vaccinated every year nor subjected to repeated chemical products.

This innate repulsion of parasites is aided by the addition of things like garlic, tumeric, ginger and leafy greens to the diet. Pomegranate is also a vermifuge, as is pumpkin, amongst other foods.images-8

It must also be emphasized that veterinarians have always being trying to offer the best advice for the general population but the types of commercial products being offered to us now are more complicated and generic than before. There are no single animals that are prone to all of these parasites. A frustrating thing about being a veterinarian these days is that the single ingredient compounds that target specific parasites are almost impossible to find in favour of the ubiquitous, broad spectrum. This makes it more difficult to appropriately target single cases of risk and why many of us are choosing to use naturopathic medicines and sensible practices that are individualized.


Nevertheless, all veterinarians have had the training to understand the lifecycles and risk factors of animal parasites and your own individual circumstances. The best thing to do is to ask them whether they think that you need to give these monthly products to your animals every month and why.


Leave a Reply