Worms in Dogs: An Overview of Different Types  

Intestinal Worms in Dogs: An Overview 

Most worm types that infect dogs colonize their intestines. Below is a brief introduction to the different kinds and ways of transmission: 

Roundworms 

Roundworms (Toxocara canis) are among the intestinal worms that live in the dog’s small intestine and feed off the semi-digested food there. 

Transmission occurs orally by the dog ingesting worm eggs. A sniff of an infected fellow canine can suffice. Furthermore, contamination through objects or soil is possible. In the latter, eggs can survive up to four years under cool, moist conditions. 

Once the roundworm eggs make it to the dog’s intestines, larvae hatch from the eggs. Roundworm females can lay up to 200,000 eggs a day. These are released with the undigested food remnants into the large intestine and then excreted by the dog through its stool. 

Hookworms 

Hookworms (Uncinaria stenocephala or Ancylostoma caninum) are also part of the intestinal worm group. They attach themselves to the dog’s intestines and feed on its blood. The eggs are, likewise, excreted with the stool. 

Infectious larvae usually enter the dog’s body orally, either directly or through consuming infected intermediate hosts that the dog eats. However, hookworms can also actively penetrate the skin, causing itchy skin inflammations. Additionally, transmission to puppy litters can occur through the mother’s milk. 

Whipworms 

Whipworms (Trichuris vulpis) too, count as intestinal worms. Specifically, they live in the infected dogs’ large intestines, feeding on their host’s blood. 

While not as common as roundworms and tapeworms, whipworms can still be found in certain regions. Infected dogs release eggs of the parasite through their stools, which can remain infectious for several years. 

The larvae are ingested orally. In the intestines, they hatch from their eggs and burrow into the intestinal mucosa. 

Tapeworms 

Tapeworms are probably the best-known worms in dogs, also living in their small intestines. Like a chain, tapeworms consist of individual segments (proglottids). 

New “chain links” are continuously formed in the tapeworm’s neck region. Conversely, mature proglottids are lost at the end, which can contain up to 100,000 eggs, depending on the type of worm. 

These terminal segments are either excreted with the stool or actively migrate out of the intestines, leading to itching in the anal area for your pooch, and possibly causing affected animals to partake in “scooting”. This is when a dog drags its rear on the ground to alleviate the itch. 

The most common types of tapeworms are: 

• the cucumber seed tapeworm (Dipylidium caninum) 
• the small fox tapeworm and dog tapeworm (Echinococcus multilocularis and granulosus) 
• Taenia spp. 
• Mesocestoides spp. 

Heartworms in Dogs 

Not all worms in dogs live in the intestines and spread via their feces. Heartworms (Dirofilaria immitis), or more precisely their larvae, are transferred to dogs by infected mosquitoes during a blood meal. 

Under the skin, the larvae (microfilariae) continue to develop and move into the dog’s blood vessels. Once in the blood, the larvae grow into “adult” worms (macrofilariae), eventually setting up home in the pulmonary artery and the heart. 

The heartworm disease is more commonly found in Mediterranean countries and North America. However, due to holidays or the import of animals from abroad, infections are increasingly being reported in other regions. 

Lungworms in Dogs 

Lungworms (Angiostrongylus vasorum and Crenosoma vulpis) are spread through snails to our dogs. The snail acts as an intermediary host, where part of the lungworms’ development takes place. 

If the dog ingests an infected snail, the larvae make their way into the intestines. They then migrate through blood and lymphatic vessels to the bronchi, trachea, and pulmonary artery. 

The adult worms lay eggs there, which the dog coughs up and often swallows again. These larvae are subsequently excreted through the stools and, once outside, can infect new snails – and the cycle begins anew. 

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Symptoms: What Are Signs Your Dog Has Worms? 

Regardless of the type of worm, symptoms usually only appear when the worms proliferate massively in the dog’s body, often showing unspecific signs like poor overall condition and weakness. 

Other important signs of an infection with intestinal worms include: 

• Weight loss 
• Vomiting 
• Diarrhoea 
• Anaemia 
• Blockages in intestinal and bile ducts (This could even result in deaths!) 

Heart and lungworms tend to cause different problems: 

• Coughing 
• Difficulty breathing 
• In advanced stages: increased tendency to bleed 
• Sudden deaths can occur if the worms block larger vessels. 

Diagnosis: How Can I Detect Worms in My Dog? 

Aside from heartworms, all worm types can be identified by examining stool samples. However, eggs or larvae are not shed with every bowel movement. Therefore, it is recommended to collect samples over three consecutive days. These are then examined either in a lab or directly by the vet. 

To diagnose heartworms, a vet must take a blood sample from the dog, where the larvae (microfilariae) are detected. Nowadays, there are also quick tests for a specific protein that female worms release into the dog’s bloodstream. 

Treatment: How to Treat Your Dog if It Has Worms? 

Various medications are available for treating worm infestations. Depending on the type of worm, your dog might need treatment over an extended period. 

Deworming agents come in the form of tablets, pastes, and even as spot-ons. They are available from the vet and are not sold over the counter. 

With heartworm disease, unfortunately, treatment isn’t as straightforward. The process is complicated and associated with many side effects. Due to potential thromboses and other complications that can lead to deaths, treatment should be conducted only by specialized vets. 

Prophylaxis: Can I Prevent Worms in Dogs? 

The bad news first: even the best hygiene and high-quality food cannot prevent worm infestations. However, a severe infestation can be avoided. 

Vets, therefore, recommend checking your dog’s stool for parasites at least four times a year. A preventative deworming done on a similar schedule may also be sensible. 

As ever, heartworms are the exception. While options against mature worms are limited, good prophylaxis against the larvae is possible. At-risk dogs are treated starting a month before potential transmission, and this is repeated every four weeks until one month after the last possible exposure. In addition, your pooch could also be protected from mosquito bites with a special collar.