Cats Cat looking sneaky under furniture with its grey paws crossed.

Published on July 10th, 2015 | by Debbie Martin


Little-known cat parasites

A cat’s body can provide a bounteous environment for a huge and varied bestiary of parasites. In this article, we’ll explore some of the lesser-known ones. Mercifully, most of the parasites on this list can be found only in the remoter parts of the world. If you happen to be taking your pet overseas, then you might want to discuss with your vet the precautions available against some of these particularly nasty parasites.


This variety of fly is at its most active during late summer, particularly during July and August. Mercifully, the botfly rarely targets cats, preferring instead to target rodents, rabbits, cattle and even humans.

The fly will either directly lay its eggs onto the skin of the host animal, or it will exploit the body of another fly as an intermediary. The female fly is larger than most other flies. She uses this to her advantage and grabs hold of them before laying a clutch of eggs beneath their wings. When the fly lands atop a suitable host (such as a cat), these eggs will sense warmth and then drop from the body of the fly onto the host. From there, they will burrow beneath the animal’s skin and develop into larvae.

This species of parasite is particularly gruesome, largely because infestations are so visibly evidenced. These larvae are large enough to appear as large lumps on the animal’s skin. Hosts literally have maggots burrowed beneath their fur, which must be removed surgically. Infestations of this sort carry with them the risk of a secondary infection.

Platynosomum concinnum (Liver Flukes)

Liver flukes are restricted to tropical climates, such as that of Hawaii and Florida. They live inside water, and typically find their way into land snails before being ingested by frogs and lizards, which act as intermediary hosts. From here, they can be ingested by all manner of predatory mammals, where they will grow to adulthood.

Symptoms can range from vomiting to jaundice and diarrhea. Unfortunately, these symptoms also occur with a number of liver conditions and so a veterinarian must first rule these out before making a definitive diagnosis. Samples of liver tissue must undergo a biopsy where its cells must be examined under a microscope.

Treatment will involve ensuring that the animal receives adequate fluids and nutrition. In severe cases, the animal may need to be hospitalized so that this can occur under controlled conditions. Intravenous vitamin D may need to be administered too, as well as antibiotics to help stave off any secondary infection.

Most infestations of cats occur in feral ones. This is largely because they are forced to hunt their own food. That said, cases have also occurred in domestic ones. Liver fluke infestations can be prevented by identifying whether a cat is susceptible and then treating them with a wormer at regular intervals. If the area poses a particularly grave risk of liver fluke, then the disease can also be prevented by ensuring that the pet is in a allocated safe area and that they stay in that area exclusively – this way they are unlikely to encounter an intermediate host.

Paragonimus kellicotti (lung fluke)

This is a lung fluke that can cause damage to the lungs and possibly even bring about pneumonia. The lung fluke is a tiny creature with a flat brown ovoid body covered in suckers which it uses to attach to its host. It is commonly known as the North American Lung Fluke, though this name is actually something of a misnomer, as the species is more common in Asia. It is most prevalent in areas surrounding the sea, owing mostly to its unique life cycle.

Their life-cycle is quite a complicated one. Its eggs find their way through faeces into the soil and from there they hatch into miracidia – which are early larval forms that are free moving and motile. These miracidia then find their way into the bodies of snails, where they develop into cercaria – which are slightly larger larvae, with a swimming tail. These cercaria then move from snails into the second host. This second host is usually a crustacean such as a crayfish, a crab or a lobster. At this point the fluke will encyst, allowing it to lie in wait until the host is eaten and the cyst along with it.

Most of the time, the animal eating the second host will be a wild amphibious mammal such as an otter. In some rarer instances, it will be a human. It is only very rare that the parasite will find its way into the body of a cat.

Many infestations of this sort are asymptomatic. Some will cause the cat to develop a cough. The cat might also lose energy, becoming noticeably tired. The condition can be diagnosed by finding the eggs in the cat’s vomit or faeces. The location and extent of the infestation in the lungs can then be established using an x-ray. Your vet will then decide whether or not to treat the infestation using one of the many medications available.

Aelurostrongylus abstrusus

This worm is found in Europe, the USA and Australia. The larvae of these worms, like those of the flukes we have already looked at, are thought to develop in snails, before being transferred to voles and mice and then ultimately cats.

Once the parasite has found its way into the cat, it migrates quickly into the lungs, either via the lymphatic system or via the bloodstream. The presence of the Lungworm can cause the host animal to develop a nasty cough – sometimes to the extent that they have difficulty breathing. If you should notice these symptoms, then suffice to say you should take the animal to a vet for examination as soon as possible. Most infestations, however, are asymptomatic.

Felicola subrostratus

This feline louse is part of the mallophaga suborder. Its life cycle is a great deal more easily understood than that of the flukes we have thus far discussed. An adult louse will attach itself to the skin of a cat and lay a clutch of eggs, which will adhere to the animal’s fur using a special secretion. These eggs will then hatch into larvae, which will feed on the animal’s skin over the course of two to three weeks.

All of this causes considerable discomfort to the cat, which may suffer from itchy skin and dandruff. Closer examination might reveal a glimpse of the lice themselves, which are only just visible with the naked eye. They are around a millimetre long, with a yellow body composed of three segments and a triangular head

.Outdoors cat scratching the parasites in its ginger fur


Physaloptera come from a family of parasites known as a nematodes, or, more commonly, roundworms. This particular variety reproduces by burrowing into the lining of the host animal’s stomach. In most cases, this is rodent or a rabbit, though cats, too can contract it.

The worm finds its way into the cat’s body through insects which carry its larvae. Once the cat has eaten the insect, the larvae develop into adult worms which burrow their way into the stomach lining.

Symptoms of an infestation might include a loss in quality of the animal’s coat a lack of appetite or even vomiting. A common side effect of the worm’s presence is gastritis, whereby the cat’s stomach lining becomes inflamed in response to the parasite’s activity.

The presence of the parasite can be established by checking the faeces for its eggs and by endoscopic examination of the stomach. It will then need to be removed via a course of de-worming medication, and in some cases, a program of anti-inflammatory medication, which will help to combat the painful effects of the gastritis.


This is another variety of nematode which is a problem for cats, particularly in California. The worm is commonly known as the ‘eye worm’, as it is active mostly inside an animals’ eyes. It can be found inside the tear glands, tear ducts, or beneath the nictitating membrane (the ‘third eyelid’ found in many species of mammal, reptile and bird). In some instances, the parasite will burrow its way into the eyeball itself.

The worm is transmitted via a species of fly which feeds on animal tears. Consequently, practices which reduce the prevalence of these flies will also reduce the likelihood that a cat will become infested.

Thelazia may be entirely asymptomatic, but it could equally cause a variety of symptoms, among them watery eyes, conjunctivitis and ulcers inside the cornea. Human victims have reported the sensation of something being in their eye and so it is likely that cats might experience a similar discomfort and show excessive attention to their eyes. To establish the presence of the parasite, the vet need only look into the animal’s eye. The worm should be visible as a centimetre-long, quick-moving strand.

Once a diagnosis has been confirmed, the worm can be treated. Since it lives so close to the surface of the skin, Thelazia is one of only a few roundworms which can be treated using topical creams. Your vet will be able to recommend the appropriate one.


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About the Author

Debbie Martin has worked at Beeston Animal Health for over five years, having previously worked as a nurse in equine and small animal practice. Although generally involved with aspects of marketing these days and putting her psychology degree to good use, she still has a great depth of up to date knowledge in all creatures great and small. Debbie lives at home with her partner and two children and spends much of her spare time looking after her horses, dogs and cats or at the home farm with the cows, sheep and turkeys.

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