|Cluster of adult worms|
Toxocara mystax (Zeder, 1800)
Toxocara cati, also known as the feline roundworm, is parasite of cats and other felids. It is one of the most common nematodes of cats, infecting both wild and domestic felids worldwide. Adult worms are localised in the gut of the host. In adult cats, the infection – which is called toxocariasis – is usually asymptomatic. However, massive infection in juvenile cats can be fatal.
Feline roundworms are brownish-yellow to cream colored to pink and may be up to 10 cm in length. Adults have short, wide cervical alae giving their anterior ends the distinct appearance of an arrow (hence their name, toxo, meaning arrow, and cara meaning head). Eggs are pitted ovals with a width of 65 μm and a length of about 75 μm making them invisible to the human eye. The larvae are so small that they are easily transmitted from an adult female to her nursing kittens through her milk.
Wild felids can become infected from a variety of sources; the primary source is infected fecal matter. The eggs of the roundworm become infective in three to four weeks after being passed out in fecal matter. Contact with the soil, licking fur near feet, and eating a host animal (such as rodents) can also lead to infection of the felines. The consumption of infected carrion also leads to contraction of the parasites, which is some of the food that members of Felidae consume. The eggs hatch in the intestines and the larvae are then released into the cat’s digestive tract. The larvae are capable of migrating through the tissues and are found in the liver, lungs, tracheal washings and muscles as well as in the digestive tract. From there, they move up to the trachea where they are swallowed causing hacking and other problems. The larvae can also move throughout the body and cause more damage to the infected individuals. The worms can even go into the mother’s milk and infect the young.
There are numerous clinical signs when dealing with Feline Roundworm. Some clinical signs that can be detected easily are vomiting, decreased appetite, and poor growth. Like many diseases, changes in behavior can also attribute as a symptom of any individuals infected with roundworms. The decreased appetite will result in individuals appear scrawny, mangy, and sickly. The poor growth and decreased appetite is exceptionally detrimental to kittens, as the appetite loss and poor growth will ultimately lead to mortality since this time of growth for kittens is very important. The mortality of kittens will lead to continual decrease of the population as there will be fewer kittens to replace adult mortality. Additional clinical signs that can be identified at closer examination include pot bellied appearance, abdominal discomfort, and diarrhea. Those with a small number of worms, however, may not show the clinical signs of being infected with worms resulting in it being hard to determine if individuals have roundworms.
Little research has been done as far as identifying the roundworm in wild felid populations. Possible detection methods for discovering feline roundworm include noting changes in behavior. The change in behavior can be identified through from eyewitness accounts. As change in behavior can include a lack of fear towards humans, eyewitness accounts can be imperative for identifying round worm. Felids especially are hard to detect for roundworm as they are naturally loners by nature (with the exception of the lion, who forms prides) and are cryptic by nature. Another method to help determine the possibility of roundworm infection is transect studies. The studies implement individuals walking along transects and spotting animals and noting for any unusual behavior within animals of populations. The transect studies, however, need suspicion of infection in order to be implemented. To that end, many DNR (Department of Natural Resources) and other wildlife organizations (such as the US Geological Survey) allow people to provide information regarding suspicion of infection. These organizations will then have people fill out a sheet detailing the mortality event.
For organizations such as the DNR, reporting individuals that have been viewed aids in the detection of individuals infected by roundworm. The contacted DNR will then proceed with the proper procedures to work on dealing with the possibility of roundworm infestation in the area. Many agencies use fecal matter testing and studies to identify the presence of parasites within a population. Agencies take the fecal matter of a suspected population and test the contents for the presence of eggs or remains of adults. Many parasites often pass their eggs through the animal’s fecal matter. Identification is paramount to reduce the chance of disease or mortality. Soil samples around the fecal matter are also taken and tested in order to ensure that there is an active roundworm population. Road kill samples also prove to be a way to detect individuals who are infected with roundworm. This is due to animals often acting differently when diseased, as shown from canine distemper, which over time, causes changes in behavior such as losing the fear of humans, becoming unnaturally aggressive, and wandering aimlessly. These samples can be recovered and then examine for the possibility of roundworm.
Treatment for Toxocara cati infections in cats is rather simple. There are a number of de-worming medications that will kill the adult worms; however, most drugs are ineffective against the immature parasites. Consequently, infected cats will usually need multiple doses administered in two or three week intervals in order to fully eradicate the worms.
T. cati infection in humans
It is possible for Toxocara cati to be transmitted to humans, usually as a consequence of humans consuming the larval stage of the parasite and results in a condition known as toxocariasis. Typically, this happens when an individual pets an infected cat, picks up the parasite off of the fur and touches their face before washing their hands. The larvae migrate through the viscera in humans. Depending on the location and number of the larva in the human host, the disease can either be asymptomatic or cause conditions such as fever, cough, pneumonia, and vision loss.
The two more severe forms of the disease are visceral toxocariasis and ocular toxocariasis. Visceral toxocariasis typically occurs in children, but can infect persons of any age. Signs and symptoms can include fever, wheezing, hepatomegaly, abdominal pain, anorexia, or skin reaction. Rarely, the migrating larvae can cause eosinophilic meningitis or encephalitis, myelitis, optic neuritis, radiculitis, cranial nerve palsy, or myocarditis. In lab findings, there is almost always a marked peripheral eosinophilia and often, anemia and a hypergammaglobulinemia.
Ocular toxocariasis typically occurs in 5 to 10-year-olds resulting in significant damage to the eye. Usually, only one eye is affected and manifestations can include strabismus, decreased vision, and leukocoria. Eye exam may show a subretinal granulomatous mass or posterior pole granuloma. Even in relatively healthy people, the roundworm larvae infect organs such as the liver, lungs, eyes or brain and cause severe symptoms, such as:
- loss of appetite or weight loss
- skin rashes
- wheezing or breathing difficulties
- seizures (fits)
- blurred or cloudy vision, usually only affecting one eye
- a very red and painful eye
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|Wikimedia Commons has media related to Toxocara cati.|
- Roundworms: Cats and Kittens from The Pet Health Library
- CDC podcast on Toxocariasis