Toxocariasis in dogs

What is toxocariasis?
Toxocariasis in dog is a parasitic disease caused Toxocara canis which is the most common parasite in digestive tract of dogs. It is a zoonotic disease, that is the parasite can spread from dog to man and so has great public health importance.
Toxocara canis is a nematode and it is round in structure having pitted albuminous layer and can grow up to 18cms in length. It is found in dogs and foxes.

Which dogs are more susceptible to toxocariasis?
Dogs of all ages and breeds can be infected by Toxocara canis. Puppies pose the greatest risk of spreading the infection to humans.

How does transmission of toxocariasis in dogs take place?
Transmission of toxocariasis in dogs by eating rodents, earthworms, cockroaches, rabbits and also by environment contaminated by Toxocara eggs. Pups get the infection from their infected mother through placenta, milk. Flies also spreads toxocariasis by acting as a mechanical vector.

How does dog transmits toxocariasis in man?
Toxocariasis is transmitted to man by ingestion of infective eggs through contaminated soil and faeces because Toxocara canis eggs accumulate in large numbers in the soil where infected dogs deposit feces and contaminate the enviroment. Toxocara eggs are also found on surfaces or foods through flies feeding on faeces. Man also become infected by eating undercooked chicken, sheep or rabbit.

Life cycle of Toxocara canis
Life cycle of Toxocara canis is complicated. Adult Toxocara canis present on the small intestine of dogs shed large number of eggs in the faeces into the environment. Eggs become infective after several weeks in the environment and during this period molting of the egg from first to second and possibly third stage larva take place. Transmission of eggs in dogs take place after ingestion of infected accidental hosts like rodents, earthworms, cockroaches, rabbits, chickens or sheep. After ingestion by the dogs larva enters the body and develop directly into adult worms in most cases. Sometimes larva dormant in the dogs body for several years.
In pregnant or lactating dogs the larva migrate to the uterus or udder.. The larva is activated and migrate across the placenta to the foetus. Larvae can also enter the bitch mammary tissues and the puppies can become infected through the milk. Migration of larva also take place to the intestine of newborn and they develop to produce eggs at about 2.5 weeks. Bitch become reinfected while cleaning the anus of her pups. The highest number of eggs are produced by the pups. After shedding in the environment eggs become infective within 10 - 21 days.

What are the signs and symptoms of toxocariasis in dog?
The dog show signs of unthriftiness, dullness, pale mucous membrane, rough and harsh body coat, emaciation, anaemia, diarrhoea and constipation. The worms absorb the nutrition from what the dog eats and can damage the intestinal lining. The dog reluctant to move, groan when touched or lifted and is either pot-bellied or the abdomen is tucked up. Due to irritation of intestinal mucosa by mature worms vomiting is seen. Cough, nasal discharge, noisy breathing may be seen in pups due to the migration of the larvae through the respiratory system.In pups nervous symptoms are shown known as “ascaris toxaemia”. Death may occur due to obstruction of intestine by the worms and also due to ulceration and perforation of the intestinal wall.

What are the signs and symptoms of toxocariasis in man?
Three syndromes of Toxocara infection are generally seen in man
Covert toxocariasis: Signs and symptoms of covert toxocariasis in man are coughing, fever, abdominal pain, headaches, difficulty in sleeping and behavioral problems
Visceral larva migrants: It occurs when the larvae enters larvae enters the internal organs of man and causes inflammation. The signs and symptoms observed in man are loss of weight, loss of appetite, headache, abdominal pain, bronchospasm, fatigue, nausea and occasionally, seizures.
Ocular larva migrants: It occurs by migration of larva into the posterior segment of the eye and occurs usually in older children and young adults. The signs and symptoms observed are decreased vision, red eye white pupil, fixed pupil, retinal fibrosis, retinal detachment, inflammation of the eye tissues, unilateral visual loss.

Diagnosis of Toxoplasma canis

Diagnosis is done by the following:
(a) Clinical signs and symptoms like pale mucous membrane, pot-bellied or tucked up abdomen

etc
(c) Presence of adult worms usually 3-4 inches long upto 7 inches in faeces or in dogs vomit
(b) Faecal examination- Presence of brown and pitted Toxocara canis eggs when observed under

microscope.

Treatment of toxocariasis in dogs:
(a) Piperazine adipate- Dose of 100mg per kg is highly effective against adult worms
Dose of 200mg/kg b.wt removes immature worms from 1-2 weeks of
age puppies
(b) Diethyl carbamazine- Dose rate of 50 mg/kg is highly effective in a single dose
(c) Pyrantel- Dose rate of 7.5mg/kg b.wt
(d) Benzimidazole compounds- dose rate of 10-15 mg/kg
(e) Ivermectin- Dose rate of 200 mg (total dose)

How to control toxocariasis in dogs?
Toxocariasis can be controlled in dogs by the following:
(a) Deworm the bitches regularly because dormant larvae is present in her tissues for many

years and transmit to the pups
(b) Deworm the puppies within 2 weeks of birth and then repeat at 4, 6, and 8 weeks of age,
(c) Floors in the kennels should be impervious so that its easy to clean.
(d) Good hygienic measures should be taken in the kennel
(e) Keep food and water containers and bedding clean
(f) Rodent population should be controlled
(g) While purchasing a new pup obtain the deworming history from the owner
(h) Do not allow dogs to ingest soil or anything that is contaminated with infective eggs

How to control and prevent toxocariasis in man from dog?
(a) Wash your hands with water and antiseptic soap after handling a dog.
(b) Do not eat undercooked chicken, sheep or rabbit.
(c) Wash vegetables thoroughly with water before eating
(d) Take your dog to a vet and give regular deworming programme

What to do if your house has Toxocara canis eggs?
Toxocara eggs can remain infectious for years.Disinfect premises, cage or kennel and all contaminated objects with bleach solution. Mop the area with a 20% bleach solution (1 part bleach to 4 parts of water) to kill the eggs.

5 comments:

  1. Very useful information. Toxocara larvae could also cause cronic urticaria (hives or rash) in man and it could only be diagnosed by toxocara antibody IgG (serum) test.

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