Toxascaris leonina
Encyclopedia
Toxascaris leonina is a common parasitic roundworm found in dogs, cats, foxes, and related host species. Toxascaris leonina, or T. leonina, is an ascarid
nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts
of T. leonina include canids (dogs, foxes, etc.) and felines
(cats), while the intermediate hosts are usually rodents, such as mice
or rats
. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.
The egg of the T. leonina is usually more oval than round. The prepatent period for T. leonina is two to three months. The adult worms are usually 3-4 inches long and can be seen in the feces and vomit of the animal.
Toxascaris leonina differs from other Toxocara in that the larvae do not migrate through the lungs; but rather, the entire developmental cycle occurs in the gut.
Infection symptoms are similar to infection by other Toxacara species (T. canis
, T. cati
). It is a common cause of diarrhea in young animals and can cause vomiting as well. Sometimes the worms themselves are vomited up, which can be alarming as they can be quite large with females reaching lengths of up to seven inches. The worms consume the host's food and can lead to lethargy and a classical pot-bellied appearance. Extreme cases of severe infections can lead to pneumonia as the worms migrate, and if there are enough worms the intestine can become obstructed.
). Therefore, when eggs are seen on a fecal flotation exam, or fecal swab, it is not necessary to determine which species is present. Roundworm infections are treated with medication, called "de-wormers", and includes such drugs as fenbendazole
, pyrantel
, milbemycin oxime
, and piperazine
.
To prevent reinfection of parasitic roundworms, it is recommended that anything that the animal has been in contact with should be cleaned thoroughly or replaced, including bedding and kennels. It is also strongly recommended that outside areas where defecation may occur be cleaned, as well as all feces removed daily from outdoor pet runs, crates, and the yard.
, the most common roundworm parasite found in dogs.
Ascarididae
Ascarididae is a family of the large intestinal roundworms. Members of the family are intestinal parasites infect all classes of vertebrates."...
nematode, a worldwide distributed helminth parasite which is in a division of eukaryotic parasites that, unlike external parasites such as lice and fleas, live inside their host. The definitive hosts
Host (biology)
In biology, a host is an organism that harbors a parasite, or a mutual or commensal symbiont, typically providing nourishment and shelter. In botany, a host plant is one that supplies food resources and substrate for certain insects or other fauna...
of T. leonina include canids (dogs, foxes, etc.) and felines
Félines
Félines may refer to the following places in France:* Félines, Ardèche, a commune in the department of Ardèche* Félines, Haute-Loire, a commune in the department of Hérault* Félines-Minervois, a commune in the department of Hérault...
(cats), while the intermediate hosts are usually rodents, such as mice
MICE
-Fiction:*Mice , alien species in The Hitchhiker's Guide to the Galaxy*The Mice -Acronyms:* "Meetings, Incentives, Conferencing, Exhibitions", facilities terminology for events...
or rats
RATS
RATS may refer to:* RATS , Regression Analysis of Time Series, a statistical package* Rough Auditing Tool for Security, a computer program...
. Infection occurs in the definitive host when the animal eats an infected rodent. While T. leonina can occur in either dogs or cats, it is far more frequent in cats.
Life cycle
The life cycle of T. leonina is fairly simple. Eggs are ingested and hatch in the small intestine. The juveniles then penetrate the mucosal lining of the small intestine. After growth and molt, they return to the intestinal lumen and mature. The adult female worm lays eggs which are passed in the feces of the dog. The eggs become infective after 3–6 days in the environment. Rodents are usually the intermediate hosts of T. leonina. The rodent ingests the eggs and, once the eggs are hatched, the larvae migrate through the tissues of the rodent. The definitive host is then infected with this parasite when it eats an infected rodent.The egg of the T. leonina is usually more oval than round. The prepatent period for T. leonina is two to three months. The adult worms are usually 3-4 inches long and can be seen in the feces and vomit of the animal.
Toxascaris leonina differs from other Toxocara in that the larvae do not migrate through the lungs; but rather, the entire developmental cycle occurs in the gut.
Symptoms of infection
Roundworms absorb the nutrients from the animal, which can interfere with digestion and can also damage the lining of the intestine. Animals may not show any outward symptoms of roundworms at all, or in other, usually more severe cases, animals may have diarrhea, vomiting, loss of appetite, experience thinning, dull coats, and in puppies or kittens, can develop distended abdomens, or "pot-belly" appearance.Infection symptoms are similar to infection by other Toxacara species (T. canis
Toxocara canis
Toxocara canis is worldwide distributed helminth parasite of dogs and other canids. T. canis are gonochorists, adult worms measure from 9 to 18 cm, are yellow-white in color, and occur in the intestine of the definitive host. In adult dogs, the infection is usually asymptomatic. By the...
, T. cati
Toxocara cati
Toxocara cati is worldwide distributed parasite of cats and other felids and it is one of the most common nematode of cats. Adult worms are localised in gut of the host. In adult cats, the infection is usually asymptomatic. However, massive infection in juvenile cats can be fatal.-External links:*...
). It is a common cause of diarrhea in young animals and can cause vomiting as well. Sometimes the worms themselves are vomited up, which can be alarming as they can be quite large with females reaching lengths of up to seven inches. The worms consume the host's food and can lead to lethargy and a classical pot-bellied appearance. Extreme cases of severe infections can lead to pneumonia as the worms migrate, and if there are enough worms the intestine can become obstructed.
Prevention and treatment
It is recommended to de-worm all puppies and kittens at 6 weeks and repeat treatment 2–4 weeks after the first treatment. T. leonina roundworm infections are treated with the same medication protocol as the T. canis or T. cati roundworm infections (see ToxocariasisToxocariasis
-History of discovery:Werner described a parasitic nematode in dogs in 1782 which he named Ascaris canis. Johnston determined that what Werner had described was actually a member of the genus Toxocara established by Stiles in 1905. Fữlleborn speculated that T canis larvae might cause granulomatous...
). Therefore, when eggs are seen on a fecal flotation exam, or fecal swab, it is not necessary to determine which species is present. Roundworm infections are treated with medication, called "de-wormers", and includes such drugs as fenbendazole
Fenbendazole
Fenbendazole is a broad spectrum benzimidazole anthelmintic used against gastrointestinal parasites including roundworms, hookworms, whipworms, the taenia species of tapeworms, pinworms, aelurostrongylus, paragonimiasis, strongyles and strongyloides and can be administered to sheep, cattle,...
, pyrantel
Pyrantel
Pyrantel is an antinematodal thiophene. It is often prescribed by veterinarians to treat and prevent the occurrence of intestinal parasites in small animal pets.-Mechanism of Action:Pyrantel is a nicotinic receptor agonist...
, milbemycin oxime
Milbemycin oxime
Milbemycin oxime is a veterinary drug from the group of milbemycins, used as a broad spectrum antiparasitic. It is active against worms , insects and mites ....
, and piperazine
Piperazine
Piperazine is an organic compound that consists of a six-membered ring containing two opposing nitrogen atoms. Piperazine exists as small alkaline deliquescent crystals with a saline taste....
.
To prevent reinfection of parasitic roundworms, it is recommended that anything that the animal has been in contact with should be cleaned thoroughly or replaced, including bedding and kennels. It is also strongly recommended that outside areas where defecation may occur be cleaned, as well as all feces removed daily from outdoor pet runs, crates, and the yard.
Risk to humans
Humans are usually not infected with T. leonina; however, this parasite has been found in humans in a few instances and is a cause of visceral larva migrans in children, though less frequently implicated than is Toxocara canisToxocara canis
Toxocara canis is worldwide distributed helminth parasite of dogs and other canids. T. canis are gonochorists, adult worms measure from 9 to 18 cm, are yellow-white in color, and occur in the intestine of the definitive host. In adult dogs, the infection is usually asymptomatic. By the...
, the most common roundworm parasite found in dogs.
External links
- The Merck Veterinary Manual
- CDC - Guidelines for Veterinarians: Prevention of Zoonotic Transmission of Ascarids and Hookworms of Dogs and Cats
- Emedicine - Toxocariasis
- CDC Parasitic Diseases Division - Toxocariasis
- http://www.cvm.okstate.edu/~users/jcfox/htdocs/clinpara/Toxocara.htm
- Roundworms: Dogs and Puppies from The Pet Health Library
- http://www.cdc.gov/ncidod/dpd/parasites/toxocara/factsht_toxocara.htm