What in the Worm? - Common Internal Parasites in Australian Dogs

From roundworm to hookworm, there are a number of creepy crawlies out there threatening your dog’s health. Caroline Zambrano finds out how to spot them, treat them and stop them from ever coming back.

In modern society, dogs have a more intimate relationship in the family. We pet, kiss, carry them and play with them. We bring them into our home and let them sleep in our beds, which at times doesn’t leave us much room to spread our legs!

We love our dogs and, for that reason, it’s never been more important to protect your family by ensuring your dog is treated for internal parasites, according to Dr Jamie Geddes from Ku-Ring-Gai Veterinary Hospital in Nth Turramurra.

Dogs can suffer from a number of internal parasites, including hookworm, roundworm, whipworm, tapeworm and heartworm – some of which pose a serious health risk to humans. “Dogs need to be wormed regularly for the health of your pet and protection of your family,” Dr Geddes says. “In a small number of cases, the consequences to humans contracting certain internal parasites – known as zoonoses – particularly to a child, can be devastating.”

Faeces of infected dogs harbour the eggs or larvae of internal parasites. “It’s not so long ago people let dogs defecate on sidewalks and didn’t pick it up,” says Dr Geddes. “But people are now much more aware of the public health significance of leaving faeces [on the ground].”

Raising awareness

A recent national study on internal parasites in pets revealed there is not enough awareness and understanding among pet owners of these dangerous bugs and their contagion. “There is a general lack of knowledge amongst pet owners about zoonoses,” says Dr Steven Kopp, lecturer and researcher in clinical parasitology at the University of Queensland. He was referring to an academic article published in 2010 in the Veterinary Journal [183], ‘Intestinal parasites of dogs and cats in Australia: The veterinarian’s perspective and pet owner awareness’.

Dr Kopp says Australian vets have an important role in the community as educators. However, the study found very few vets routinely discuss the zoonotic potential of internal parasites with clients. “This could be due to an over-reliance on anthelmintics [anti-worming medications], which has led to certain complacency about the need to educate pet owners about the risks of zoonoses,” he says.

In total, 59 veterinary clinics, 676 dog owners and 420 cat owners participated in the study. Of the vet clinics, 78 per cent completed the questionnaire. Of the pet owners who participated in the study, 71.3 per cent and 75.5 per cent respectively were aware of zoonoses. The most common source of information for pet owners pertaining to zoonoses was the vet. “Of the 58.8 per cent of owners who stated that vets had educated them about zoonoses, 24.8 per cent had solely been educated by vets,” Dr Kopp says.

Perhaps pet owners are not actively seeking enough information. “Vets have the knowledge and pet owners can learn from them. We need to change everyone’s perception of how we approach worming dogs [and cats],” he adds.

Tackling re-infestation

Anti-worming medications play their role in treating internal parasitic infection, but vets are still witnessing apparent treatment failures. This is usually due to a lack of awareness of basic parasitic life cycles, and is rarely a reflection on the worming product itself, Dr Kopp says.

“It’s important for pet owners to understand the phenomenon of re-infection,” he says. “With many of the popular tick and flea control products, you have a theoretical 30-day barrier to re-infestation. But with worming, your dog will be prone to new infection a week later with most oral wormers – they don’t have a long residual effect.

However, if you understand the life cycle of these parasites, you can look at breaking it by removing faeces in the backyard, for example.”

Treatment schedule

Dr Kopp advocates worming every three months, but the high zoonotic potential of many gastrointestinal parasites could require monthly treatment.

“We also need to reinforce these products with environmental management, such as picking up the faeces from the backyard and washing hands after touching animals,” he says. “It’s very important to educate kids to wash their hands and not allow pets to lick their face.”

Researchers also advise vets to conduct a regular faecal analysis every six months. If pet owners are concerned about being infected with internal parasites, Dr Kopp recommends seeing their GP for testing and treatment.

Common Internal Parasites in Australian Dogs

Hookworms: feed on blood from the lining of the intestines in dogs and cats and can cause anaemia, diarrhoea and weight loss in pets. The worms look like long strings of spaghetti. The eggs pass out of the body in the stool and animals become infected by eating infected eggs or larvae, and even penetration of footpads or skin by larvae. They pose a health risk to humans.

Roundworms: live in the small intestine and the eggs are passed in the stool, appearing like spaghetti.

Signs of infection include poor hair coat, diarrhoea, ill-thrift, pot-bellied appearance, and occasional secondary bacterial pneumonia. In puppies, infection may lead to stunted growth, lung damage and death. They also pose a health risk to humans.

Whipworm: Adults live in the large intestine and eggs are passed in the faeces. Infection is via faecal-oral transmission and more likely to occur where multiple dogs are housed together and have access to faecal material. Eggs do not appear in the faeces until three months post-infection and can survive in the external environment for several years. Worms are usually not seen in the stool. Clinical signs are weight loss and diarrhoea. Heavy infestations may lead to anaemia and bloody diarrhoea.

Tapeworm: lives in the intestine of dogs and cats. They have a small, rice-like appearance found in the stool. Signs of infection are rare since it doesn’t often cause a problem, but it can include a shaggy coat, irritability, diarrhoea or lethargy. Hydatid tapeworms have significant human health implications, causing serious disease related to cyst formation in some organs of the body. The hydatid tapeworm can only be passed on from a sheep so it is paramount to regularly worm dogs that live on a farm.

Heartworm: is contracted through a mosquito bite and can cause heart and lung disease if left untreated. An infected dog can die within a few months. Heartworm may show no sign of infection, but most common symptoms are coughing (sometimes with blood), exercise intolerance, breathing difficulty, weight loss and abdominal fluid.

Giardia: a common protozoan that lives in the small intestine and spreads across humans and animals via the faecal-oral route. Clinical signs are diarrhoea and weight loss. Treatment is with oral medication to all exposed pets.

Cryptosporidium: a protozoan parasite common in dogs, usually occurring younger than six months, and highly infectious. It can start with weight loss and poor appetite and develop into chronic diarrhoea and dehydration, becoming life threatening to dogs and humans with a weakened immune system. Many dogs never show symptoms of infection.

Symptoms of worms in dogs

  • Anorexia
  • Vomiting
  • Diarrhoea
  • Stunted growth
  • Poor body condition
  • Swollen or tender abdomen
  • Dull coat
  • Visible worms in faeces