Mary Allen
Hunde werden nach wie vor häufig mit Parasitenbefall in der Praxis vorgestellt. Wir klären in diesem Beitrag die wichtigsten Fragen und geben Ihnen eine Zusammenfassung zum Thema Parasiten bei Hunden.
Parasites In Dogs: Definitions Of Terms
Endoparasites: Worms and protozoa that live in internal organs such as the intestines, lungs, or heart.
Ectoparasites: Mites, fleas, ticks, etc. that parasitize on the body surface.
Host: Animal (including human) infested with the parasite. The target or final host is the one to which the parasite is best adapted and in which it multiplies. Intermediate hosts are used for further development (e.g. from egg to larva) and distribution. Intermediate hosts thus also act as so-called “vectors”, as transmitters. False hosts are those that are severely damaged by the parasite or in which it cannot (well) reproduce.
A certain amount of time elapses between infection with a parasite and the shedding of contagious (infectious) particles such as eggs. It is of different length for each parasite and is relevant for later diagnostics: The dog can already be infected with parasites, but these are not yet excreting any eggs and cannot be detected in the feces, for example.
Zoonosis: Zoonoses are diseases that can be passed from animals to humans.
Dog Parasites: Why Are They Problematic?
Many dog parasites are also infectious to humans, which is why the dog should not carry any parasites if possible. Healthy adult dogs often show no symptoms even though they are infected. Unfortunately, this often means that they are not regularly treated for parasites. They can be dangerous, especially for young, old, and immunocompromised dogs.
In many places, there is a fairly high density of dogs, so the parasites can spread easily. This applies in particular to animal boarding houses, animal shelters, or larger groups of dogs in one sitting, but also to dog training areas or areas with a high proportion of dog-owning households. In this way, the little pests reliably find new hosts in which they can multiply. Also, foxes carry broadly the same parasites. They also spread them in the city, where the fox is often at home as a culture follower.
An increasing number of dogs traveling and the import of animals from animal welfare projects in southern and eastern Europe have made parasites such as leishmania or heartworms that were previously considered “exotic” visible in German veterinary practices. With increasing heat (climate change), their intermediate hosts such as mosquitoes and ticks are also becoming at home in our latitudes, so these parasites will be able to stay here in the foreseeable future. And: Due to the milder winters, fewer and fewer parasites are taking their typical “winter break”. So the dog must be protected from them all year round.
Dog Parasites: Which Ones Are Important?
Here is a brief explanation of important dog parasites (Of course, this does not claim to be complete.).
Endoparasite Dog
Worms:
Roundworms, hookworms, tapeworms, and whipworms parasitize in the small or large intestines of dogs. Adult animals are usually unproblematic. Puppies in particular suffer from diarrhea and emaciation when the infestation is severe. In addition to the oral ingestion of the eggs or larvae, roundworms, for example, can also be transmitted from the bitch to the puppies in the uterus or with the mother’s milk. The latter also applies to hookworms, the dog can also become infected with them through the skin, which some species can actively pierce.
Attention: A tapeworm in dogs can also be the small fox tapeworm. Infection with it is life-threatening for humans, which is why good prevention is so important for our pets! Due to the fox populations living close to humans, dogs (and also cats) can become infected with this parasite.
However, worms are not only intestinal parasites in dogs: dog lungworms live and multiply in the lungs. Their larvae are coughed up, swallowed, and excreted in the feces. They cause coughing and fever and are particularly dangerous for young animals.
Heartworms parasitize in the heart and pulmonary arteries. They cause breathing problems, coughing, and reduced exercise capacity. They are transmitted by mosquitoes. Up until now, heartworm in dogs has been a travel disease, but its intermediate host is thriving further north.
Protozoa:
Giardia in dogs, such as Cryptosporidium and other protozoa (protozoa), live in the intestine and cause diarrhea of varying severity, which can be short or long-lasting. Puppies are particularly affected, in older dogs the infections often run their course without symptoms. The excreted oocysts (reproduction stages, similar to eggs) are ingested orally, e.g. via feces or the contaminated environment. Giardia treatment is often lengthy, especially in larger groups of dogs.
Leishmania is also a unicellular parasite that attacks the dog’s immune system. They are mainly transmitted by special mosquitoes and have so far mainly been found in southern and central Europe. However, the limit of its spread is shifting further and further north. Leishmaniasis manifests itself in various problems of varying degrees of severity: skin changes and lameness are the most common. Reduced exercise capacity, weight loss, and movement disorders are also common. The disease is chronic and long-term, complex treatment is necessary.
Tick-borne Babesia infects red blood cells (erythrocytes). Up to now, Babesias were also more likely to be found in Mediterranean latitudes, but they are now also native to Central Europe and are also spreading further with us. Depending on the Babesia species with which the dogs are infected and depending on the condition of the dog beforehand (young or old, healthy or already weak), the severity of the course varies. Fever and anemia are common, and vomiting and yellowing of the mucous membranes (icterus) are also possible. Disorders of the respiratory and digestive tract are less common. Babesiosis can be life-threatening!
Anaplasmosis is transmitted by ticks. The pathogen infects cells of the immune system and causes fever. It is detected with a special laboratory test (PCR, polymerase chain reaction) since the detection of antibodies does not reliably indicate an infection.
There are other protozoa infections in dogs such as Neospora and Toxoplasma.
Ectoparasites Dog
Although ticks suck blood, they are above all important as carriers of e.g. babesia, anaplasma, and borrelia (tick diseases) and should therefore always be removed quickly. They stay in grass, bushes, and undergrowth.
Mites cause severe itching, dull fur, and dandruff. Some are very contagious from dog to dog or via e.g. blankets and brushes. The clinical picture sometimes resembles that of atopic dermatitis.
A special disease is demodicosis: Demodex mites live in the hair follicles of healthy dogs. How the disease comes about has not yet been finally clarified. The following is certain: In the event of an immune deficiency (due to other illnesses, or stress), the mites will multiply massively. As a result, hair loss, pustules, and redness occur, which can later become infected with bacteria or fungi and then start to itch.
Ear mites in dogs cause severe itching and ear infections. So a dog with ear mites will scratch its ears, rub its head across the ground, and shake. The larvae of the autumn grass mites usually infest dogs from August to October and are often where fallen fruit can be found. They are visible to the naked eye as red dots, often in the crease between the toes or in the ears. Severe itching follows. The event is unproblematic to deal with.
Fleas are widespread, not host-specific, and serve as vectors for e.g. tapeworms. They suck blood and can cause flea saliva allergies. A flea infestation can be recognized by the itching, but skin changes can also occur. In the case of allergies, in particular, these only develop as a result of severe scratching. Fleas are visible to the naked eye, in fur, on roosting sites, etc. Flea droppings show up as dark crumbs. When dissolved in water, it turns red (undigested blood) to distinguish it from dirt, which remains grey.
Lice and biting lice are rarely found in dogs. They cause itching and are transmitted from dog to dog.
Parasites Dog: Diagnosis
Many parasites “give away” themselves through relatively typical symptoms. However, infection in adult dogs can often be symptomless. Then further investigations help:
- Examination of the feces: Provides information about parasites in the gastrointestinal tract.
- Detection of eggs or metabolites of the parasites, depending on the method.
- Skin examination: A thorough examination of the skin and fur with a magnifying glass and a fine comb is necessary if ectoparasites are suspected. A scraping (removal of skin cells with a scalpel) may also be necessary. Live mites and fleas can be seen under a magnifying glass, with a flea comb you can find e.g. flea droppings.
- Adhesive film preparation: A piece of the adhesive film is dabbed onto an area of skin and the adhering material is examined under the microscope. Applies to ectoparasites, but also to the eggs of e.g. tapeworms adhering to the coat.
- Blood test: If there is a suspicion, a blood test is useful to find antibodies against Leishmania, and Babesia or to detect typical changes in the blood in the case of parasite infestation.
- Likewise, parasite detection using PCR (see above).
- Further examinations, such as biopsies or smears, may be necessary (e.g. puncture of a joint or of the bone marrow in leishmaniasis).
Parasites Dog: Treatment
If your dog has caught lodgers, there are usually effective ways to get rid of them. Individual diseases, such as leishmaniasis, can be very difficult or impossible to treat. It is also important to treat the environment as well: If a flea infestation is found, the associated apartment must be thoroughly cleaned and the treatment extends over 6 months, since the eggs, larvae, etc. are extremely resistant. All other pets must also be checked or treated as well, otherwise, the parasites will return within a short time.
We do not recommend using home remedies against ear mites in dogs, especially if an ear infection is already present. It definitely belongs at the vet!
Parasites Dog: Prophylaxis
Regular preventive treatment of the dog against parasites is worthwhile, as it is much less complex and unpleasant than treating infections. There are “spot-on” preparations for dripping onto the skin, pastes, tablets, or collars that you as the owner can easily use.
A distinction can be made between repellents (substances that keep parasites away) and regular preventive treatment. Repellents (collars, spot-on) keep away e.g. fleas and ticks, which do not “taste” the permanently released substance on the skin. In contrast, a gastrointestinal worm pill given regularly will kill the worms present; but it cannot prevent reinfection. Pregnant bitches should be particularly well dewormed so that the puppies do not become infected with hookworms or roundworms.
In the case of intermediate hosts, combating them also helps:
- Ticks should be removed correctly as soon as possible after they are discovered: To do this, grab the tick as close to the skin as possible with tick tweezers and gently twist it until it detaches. Alternatively, hook under the tick hook and turn it as well. Do not pull hard, then the front part of the tick will remain in the skin and can cause inflammation.
- On holiday in the south, take protection against mosquitoes. (Stay indoors at dusk and in the dark, use an insect spray, and attach nets.)
- Fleas transmit dog tapeworms – so the dog should also be protected from fleas.
With larger groups of dogs or breeds, the importance of prophylaxis and hygiene increases again, since parasites can spread even more here.
There are now vaccinations against babesia and leishmania, but they are not yet approved everywhere.
Talk to your vet about which method is best for your dog and how often it should be used!
As the owner, you should wash your hands after every contact with the dog and especially before eating. Also, teach this rule to any children who cuddle with the dog.
Parasite Dog: Conclusion
There are a large number of parasites in dogs. To avoid damage, your dog should be checked regularly and protected against parasites. This is how you protect yourself. Talk to your vet about the best way!