Toxocara Canis in Dogs: Life Cycle and Transmission

Toxocara canis in dogs is a serious issue that affects not only the health of the dog but also its human family. The parasite's life cycle is complex and involves several stages.

Adult Toxocara canis worms live in the dog's intestines and can produce up to 200,000 eggs per day. These eggs can then be shed in the dog's feces.

Dogs can become infected with Toxocara canis through the ingestion of contaminated feces, which can happen when they eat their own feces or the feces of another infected dog.

See what others are reading: Flea Eggs on Dog

Toxocariasis is a widespread disease caused by the larvae of two roundworms, Toxocara canis and Toxocara cati. It's estimated that almost 14% of the United States population is infected.

The larvae of T. canis and T. cati live in the intestines of dogs and cats. Dog and cat intestines are the reservoir for T. canis and T. cati respectively.

T. canis is more commonly responsible for human disease. The eggs of these worms are usually found in the environment through the feces of puppies and lactating dogs.

Human toxocariasis is usually symptom-free, but it can affect young children who have a history of eating soil, exposure to dogs, and those living in poor socioeconomic conditions.

Suggestion: Toxocara Canis Common Name

Toxocara canis in dogs is caused by a parasitic worm that can infect both dogs and humans. Adult T. canis worms are 4 to 6 inches long, stout, and white, and are easily identified.

Puppies are more susceptible to infection because of their migration pattern differences compared to adult dogs. In puppies, the larvae reenter the alveolar blood vessels and travel to the muscles or organs, where they become encysted and their development is arrested.

The female worm produces thousands of eggs per day, which are shed in the feces into the environment. These eggs are undeveloped and not immediately infective, but will become infective in 2 to 4 weeks.

Intriguing read: Dog Flea Eggs Images

The causal agents of toxocariasis are the larvae of Toxocara spp., a type of ascarid roundworm common in mammals.

These larvae are found in the digestive tracts of infected animals, typically dogs and cats.

The dog roundworm, T. canis, is presumed to be the most common cause of toxocariasis in humans.

The cat roundworm, T. cati, is another confirmed zoonotic species that can infect humans.

Readers also liked: Can You Get Kennel Cough from Your Dog

Adult Toxocara canis worms are easily identified, measuring 4 to 6 inches long, stout, and white. They can be found in puppies, with some studies suggesting up to 33% of adult dogs can also be infected.

The life cycle of Toxocara canis begins with adult worms mating in the dog's intestine, producing thousands of eggs per day that are shed in the feces. These eggs are undeveloped and not immediately infective, but become so in 2 to 4 weeks at room temperature.

In puppies, the eggs are ingested by the mother or the puppy itself, and the eggs hatch releasing L3 larvae into the host's intestine. The larvae then penetrate the intestinal wall and travel via the blood to the liver and then to the lungs, where they burst into the alveoli.

Puppies can become infected through the transplacental or transmammary route. The transplacental route occurs when a pregnant dog with encysted larvae passes the larvae to her puppies via the umbilical vein.

A fresh viewpoint: Canine Distemper Symptoms in Puppies

Toxocara canis infects almost all wild and domestic canids, including puppies, who are more likely to have patent infections than older dogs.

Puppies are especially vulnerable to Toxocara canis infections, which is why it's essential to take preventative measures early on.

Paratenic hosts, such as livestock, can also carry the parasite, and consuming undercooked meat, especially liver, can lead to human infections.

Cockroaches and earthworms have been experimentally infected, and could potentially serve as paratenic or transport hosts.

Toxocara canis and T. cati are found globally, but their prevalence is highest in developing countries, where access to proper sanitation and healthcare may be limited.

In developed countries, more infections are detected among people in lower socioeconomic strata, highlighting the importance of socioeconomic factors in the spread of the parasite.

Broaden your view: Ehrlichia Canis Dogs

Toxocara canis infects almost all wild and domestic canids. This includes puppies, who are more likely to have patent infections.

T. cati is found in wild and domestic felids of all ages, but patent infections are slightly more common in kittens.

Paratenic hosts for both species include various mammals and birds. Livestock, such as those that produce beef, lamb, chicken, and duck meat, can be infected.

Cockroaches and earthworms have been experimentally infected, and could potentially serve as paratenic or transport hosts for the parasite.

Toxocara canis and T. cati are found worldwide, but the prevalence of these parasites is highest in developing countries.

The worms are common in domestic dogs and cats, and their distribution is global.

Adult Toxocara spp. measure approximately 4—6 cm long (males) and 6—10 cm long (females).

More infections are detected among people in lower socioeconomic strata in developed countries.

The worms have three "lips" on the anterior end of the worm, a characteristic shared by all ascarids.

Toxocara spp. also possess large, spear-shaped cervical alae, which are broader in T. cati than T. canis.

In neonates and puppies, heavy infections via the transplacental route may result in pneumonia and acute death as early as 10 days of age.

Heavy burdens with T. canis in pups can produce ill thrift and stunting.

Pups may adopt a straddle-legged posture and a pot-bellied appearance due to abdominal discomfort.

Anorexia, diarrhoea, and vomiting can occur in infected pups, and adult worms may be expelled.

Occasional gastrointestinal obstruction and death may result from heavy T. canis burdens.

In neonates and puppies, heavy infections can lead to pneumonia and acute death as early as 10 days of age due to enteritis and gastrointestinal blockage.

Heavy burdens with T. canis in pups can produce ill thrift, stunting, and abdominal discomfort.

Pups with heavy burdens may adopt a straddle-legged posture and a pot-bellied appearance.

Adult worms may be expelled, causing vomiting and diarrhoea.

Gastrointestinal obstruction and death may result from heavy burdens with T. canis in pups.

Toxascaris leonina infection is usually asymptomatic.

Diagnosis is a crucial step in identifying Toxocara infections in puppies. Detection of thick-shelled eggs on standard faecal flotation can confirm the presence of Toxocara (pitted) or Toxascaris (smooth) eggs.

A positive diagnosis can be made by detecting the eggs on standard faecal flotation with a specific gravity of 1.20. This method is outlined in SOP 1.

In some cases, immature worms may still produce clinical disease in puppies, even if eggs are not detected in the faeces. Treatment and examination of expelled worms are recommended in these situations.

It's essential to note that the absence of eggs in faeces does not rule out infection.

Preventing toxocara canis in dogs requires a multi-faceted approach. Regular deworming is a crucial step in preventing the maturation of larvae. Deworming puppies every 2 weeks up to 12 weeks of age can prevent egg shedding and environmental contamination.

Picking up dog feces is a simple yet effective way to control roundworms. Roundworm eggs are extremely resistant to common disinfectants, including bleach, and can survive for years on surfaces. This is why it's essential to pick up dog feces immediately to prevent contamination.

Covering sandboxes is another important measure to prevent infection. Children's sandboxes can be contaminated with eggs of both T. canis and T. cati, but this can be prevented if the sandbox is covered.

Deworming dogs regularly is also crucial. Deworming puppies at 2, 4, 6, and 8 weeks of age and then monthly, if possible, can help prevent roundworm infection.

Here are three simple points to remember:

By following these simple steps, you can significantly reduce the risk of toxocara canis infection in your dog and prevent the transmission of this disease to humans.

Toxocara canis in dogs has a fascinating developmental biology. Infection begins when embryonated eggs are ingested, and the resistant eggshell breaks down, releasing infective larvae that penetrate the intestinal mucosa.

The larvae can migrate through various tissues, but in canids, they follow a full developmental pathway, migrating through the lungs, trachea, and oesophagus back to the gastrointestinal tract. This unique pathway is not seen in other mammalian species.

Dormant tissue larvae can remain in a host for up to 9 years after infection, and in vitro, they can survive for up to 18 months without any morphological development.

Explore further: What Does Flea Larvae Look like on a Dog

Toxocara canis, a parasite that infects dogs, has a fascinating developmental biology. The infection begins when embryonated eggs are ingested and the larvae emerge, penetrating the intestinal mucosa.

Only canid species, such as dogs, allow the larvae to complete their full developmental pathway. In other mammals, the larvae remain in the tissue-migratory phase without developing.

Take a look at this: Flea Larvae on Dog

Dormant tissue larvae can survive for up to 9 years in a mammalian host. This means that a dog can remain infected for years without showing any symptoms.

The larvae in dogs can be restrained from development, arrested in the tissues until reactivated during the third trimester of pregnancy. This allows the larvae to infect the gestating pups and pass into the colostrum, causing post-natal infection.

In vitro, larvae can survive for up to 18 months without any morphological development. However, they maintain a high metabolic rate and require a regular supply of glucose and amino acids to survive.

The parasites secrete copious quantities of glycoprotein antigens, known as T. canis Excreted-Secreted (TES) products. These products are secreted by cultured larvae and are an important part of the parasite's biology.

The surface coat of the T. canis larva is a carbohydrate-rich glycocalyx, 10 nm in thickness, that plays a primary role in immune evasion.

This fuzzy envelope is detached by a similar distance from the epicuticle and is shed when the parasite is bound by granulocytes or antibodies.

The surface coat is a common feature of nematode organisms, both parasitic and free-living.

Its principal constituent is TES-120, a set of secreted mucins that are thought to be produced from two major glands in the larval body.

The surface coat carries a strong negative charge, binding to cationic stains such as ruthenium red and cationized ferritin, but the identity of this charge group has yet to be determined.

The surface coat mucins are secreted from the oesophageal and secretory glands, with the latter being directly connected to the cuticle by a duct opening at the secretory pore.

If this caught your attention, see: What Food Is Good for Dogs Skin and Coat