THE MOST COMMON PARASITES IN DOGS
HOW DO THEY AFFECT YOUR DOG’S HEALTH AND SOMETIMES THAT OF YOUR FAMILY?
HOW DO THEY AFFECT YOUR DOG’S HEALTH AND SOMETIMES THAT OF YOUR FAMILY?
Lungworms are small worms that live in the blood vessels of the lungs. The larvae pass through the walls of the lungs, are coughed up and passed out via the faeces. They enter a slug or snail and the dog is infested by swallowing this, or by swallowing larvae left in a slime trail.
Young dogs (under 18 months) are most at risk of infestation.
Lungworm infestation causes respiratory signs such as coughing and tiredness at exercise. Infestation may also cause blood clotting problems, leading to a wide range of signs associated with bleeding. Most worryingly, in more than 10% of cases, lungworm can cause death.1
Roundworms are the most common type of parasitic worm found inside our pets: up to 30% of dogs and 70% of puppies are infested with Toxocara canis.1,2
Roundworms are highly prolific and females can lay up to 300 000 eggs per day. Infested dogs shed these microscopic eggs via their droppings into the environment, where they become infective after 2 to 3 weeks. The eggs can stay alive and remain infective for up to 5 years, as they are resistant to hot and cold temperatures, as well as disinfectants. Other dogs become infested as they swallow these eggs when they sniff or lick soil or other substances soiled by faeces. Dogs may also get infested if they eat rodents or other small mammals that can carry roundworm larvae.
Puppies can be infested with roundworms from birth as the mother can pass worms to her puppies during pregnancy, and via her milk when nursing.
Adult roundworms live in the dog's intestines and many dogs do not show any sign of illness. However, dogs that have a major infestation, particularly puppies, can show digestive signs such as a potbelly, diarrhoea and vomiting. They may also have respiratory signs as the immature worms pass through their lungs, leading to coughing and pneumonia.
Similarly to roundworms, hookworms are parasites that live in the dog’s digestive system. The hookworm attaches to the lining of the dog’s intestinal wall and feeds on tissue and blood. Its eggs are laid in the dog’s digestive tract and pass into the environment via the faeces.
Larvae hatch out from hookworm eggs after about 10 days and live in the soil. These larvae can infest your dog by means of contact and penetration of the skin or through swallowing after sniffing or licking contaminated areas.
Through their feeding activity, hookworms cause internal blood loss. They are a serious threat to dogs, especially to young puppies as they can induce bloody diarrhoea and severe anaemia which sometimes leads to death. In older dogs the blood loss may be more chronic, and the dog may additionally lose weight.
Whipworms live in the dog’s large intestine.
Whipworms are named for their characteristic whip-shaped body. The body is composed of a thin end (the lash of the whip) and a thick end (the handle). They attach themselves to the walls of the large intestine and feed on blood.
Your dog may become infested with whipworms by swallowing infective eggs in soil or other substances contaminated by dog faeces. These eggs are particularly resistant in the environment, surviving for at least 5 years. An infestation can happen any time your dog sniffs the ground, roots in the dirt, or plays with toys that have been in contact with contaminated soil.
Dogs infested with a few whipworms may not show any sign of infestation. However, a severe whipworm infestation will cause bloody diarrhoea and severe anaemia, and could lead to death in the absence of treatment. Chronic infestation causes progressive weight loss.
Heartworms are not generally found in the UK or Ireland. However, they may be a risk for any dog that travels abroad.
Heartworms are an emerging risk for dogs throughout southern and eastern European countries.1 Climate changes are favourable to these parasites as heartworms are transmitted by mosquitoes.
Once mature, heartworms live in the heart and large blood vessels of the lungs. Adult heartworms can measure up to 30 cm in length.
Heartworm larvae deposited by the feeding mosquito migrate in 5-6 months to the heart chambers or into the vessels of the lungs. Once matured, those worms affect the blood flow. The right side of the heart has to work much harder to push blood towards the vessels, which progressively causes heart failure.
Clinical signs of heart or lung problems are commonly present and these symptoms develop and progress slowly over weeks or months. Initially your dog will tire easily, show shortness of breath or coughing after exercise. In the later stages coughing and fatigue will be observed at rest as well. If left untreated, heartworm disease can be fatal.
Ticks are the second most common external parasites to affect your dog. Indeed, a recent UK study found 1 in 3 dogs infested with ticks.1 They are most abundant from spring to autumn but are active all year round. Because of climate change, increase in deer populations (which host ticks) and travelling pets, ticks remain active for longer periods, their numbers are increasing, and new tick species and tick-borne diseases are appearing where previously they were not present.2,3
Ticks are found on vegetation and cling on to our pets as they brush past. It is very difficult to prevent a dog’s exposure to ticks. Ticks can attach to your dog when he or she goes with you on walks in the countryside, parks or woods.
There are a number of different ticks which can affect our pets. Some are more common in different parts of the UK and in other countries, so if you travel with your dog please consult your vet about risks in the places you are visiting.
They pierce the dog’s skin and suck their blood over several days. This can cause irritation, painful abscesses and anaemia in small animals.
However, ticks are a particular concern because they transmit infectious diseases, some of which can be fatal:
Fleas are a year round problem and the most common external parasites to affect our dogs.The adult fleas found on our pets represent only 5% of the flea population. The rest are lurking as eggs, larvae and pupae (cocoons containing pre-emerged fleas) in the environment. This may be outside in the garden, park or woods or may be within our homes either in carpets, between floorboards, in sofas, or in your pet’s bedding.
In the environment eggs hatch to larvae and then develop to pupae (cocoons containing pre-emerged fleas). When your cat passes by, this stimulates the young adult fleas to emerge from their cocoons and jump onto your pet. But beware, pre-emerged fleas in cocoons can stay alive for 10 months or more!
Fleas are prolific breeders, and flea numbers can explode in the warm spring and summer months when one female flea is able to become 1,000 fleas in just 21 days. But that’s not to say that fleas are only a problem in warmer weather. Milder, wetter winters and heated homes allow these parasites to thrive throughout the year.
You might think you have cleared a flea infestation after treating your pet, only to see new fleas appearing in the weeks after administering the treatment. This is actually normal, as flea products do not repel fleas and re-infestation of your dog is due to the continued emergence of adult fleas from cocoons in the infested environment. As fleas readily survive both indoors and outdoors and there are many possible sources of flea eggs, including wild and feral animals, or just untreated neighbouring cats and dogs, the source of new fleas is a never-ending story.
To really get rid of fleas, you have to disrupt their life cycle – adult fleas must be killed before they can start laying eggs. Regular treatment of your pet will help to control the reservoir of adult and immature stages of the flea lifecycle in your home. But, if your house is heavily infested, it is recommended to use a home environmental spray.
Fleas can cause itching and scratching when they bite our dogs to feed on blood. Some dogs can develop Flea Allergy Dermatitis, an allergic reaction to flea saliva resulting in intense itching, scratching, hair loss and skin thickening, which can be very distressing.
Puppies can become anaemic due to the amount of blood sucked out by fleas when feeding - as their bodies are so small they are unable to tolerate this amount of blood loss. Fleas also transmit the main tapeworm species that infests dogs and cats.