Dog parasites: What you should know

Ticks attach to mammals and birds using strong mouthparts to feed of the animals’ blood. Ticks are most active when it is warm and can often be found in vegetation like forests or meadows.
 

Especially dogs and owners who are frequently outdoors are in danger of tick exposure.

Like ticks, fleas feed on blood and are found on mammals and birds. The source of fleas seems like a never-ending story: They easily survive indoors and outdoors and there are many routes of flea egg transmission. These include contact to wild and feral animals - or just untreated cats and dogs in the neighborhood - and more.

Fleas will bite not only dogs but also other pets and humans. This can cause irritation and transmit diseases.

Mites are tiny, eight-legged organisms, and some species like Sarcoptes scabiei or demodex affect both dogs and people.
 

Because mites burrow within the skin, they do not readily move off dogs to find new hosts. Direct contact with infested dogs, however, runs the risk of transfer of mites to humans and the transmission of disease.

Roundworms are the most common type of parasitic worm found inside of pets. They live in the intestines. Dogs get infested by swallowing roundworm eggs when they sniff or lick contaminated soil, by eating infested raw meat, or through transmission from mother to pup.

Many dogs who have roundworms do not show signs of illness. However, a major infestation can show digestive signs such as a potbelly, diarrhea and vomiting. Even the lungs can be affected.

Hookworms live in the intestines of dogs and shed eggs into the environment via the faeces. Their larvae hatch outside and infect dogs who accidently ingest them. Larvae of some hookworm species present in warm climates can penetrate the skin and find their way to the gut.
 

Hookworms can also infect people. Although they do not mature in humans, the body responds with inflammation.

Heartworm disease is caused by the parasitic worm Dirofilaria immitis which is transmitted by mosquitos. In dogs, it affects the circulatory and respiratory systems. It can start with a mild persistent cough and reluctance to exercise and can progress to heart failure.
 

Heartworm disease is endemic in countries on every continent except Antarctica. Climate change increases the prevalence of mosquitos and therefore heartworm disease.

Eyeworms, or Thelazia callipaeda, are small white worms that infest a number of mammals, including dogs. They live on the surface of the eyes. A certain fruit fly acts as intermediate host, transmitting the parasite while feeding on tears of pets (yes, you heard that right!).
 

Eyeworms cause inflammation and ulcers. In severe forms, perforation and blindness may occur. However, they can be prevented and treated.

Whipworms attach themselves to the walls of a dog's large intestine and feed on blood. Dogs become infested by swallowing infective eggs while sniffing the ground, rooting in the dirt, or playing with toys that have been in contact with contaminated soil. Some dogs show no sign of infestation.
 

However, a severe whipworm infestation will cause bloody diarrhea and severe anaemia, and could lead to death in the absence of treatment.

Lungworms are small worms that live in the blood vessels of the lungs. Their intermediate hosts are slugs and snails. Dogs – especially young ones – are at risk of getting infected by eating the infested slugs or snails.
 

Lungworm infestation causes respiratory signs such as coughing and tiredness at exercise. It may also cause blood clotting problems, leading to a wide range of signs associated with bleeding. Lungworms can be fatal.