Cat worm infections, the infection of cats (Felidae) with parasitic worms, occur frequently. Most worm species occur worldwide in both domestic and other cats, but there are regional, species and lifestyle differences in the frequency of infestation. According to the classification of the corresponding parasites in the zoological system, infections can be divided into those caused by nematode and flatworms - in the case of the latter, mainly cestoda and trematoda - while other strains are of no veterinary significance. While threadworms usually do not require an intermediate host for their reproduction, the development cycle of flatworms always proceeds via alternate hosts.
As predators, cats are the final host for most worms. As so-called endoparasites ("internal parasites"), the worms colonize various internal organs, but usually cause no or only minor symptoms of disease. The infection therefore does not necessarily have to manifest itself in a worm infection (helminthosis). For most parasites, infection can be detected by examining feces for eggs or larvae. Some worms found in cats can also be transmitted to humans and are therefore zoonotic pathogens. Of greater importance here are the feline toxocara mystax and the fox tapeworm. Especially such worm infections should be controlled by regular deworming of cats living in close contact with humans.
Threadworm infections In cats, various representatives of the nematodes (Nematoda) parasitize, especially roundworms, hookworms, lungworms, hairworms and stomach worms. Co-infections by coccidia are common, especially in kittens.
Roundworm infestation
The most common roundworm in most cats is toxocara mystax (syn. toxocara cati), infestation with toxascaris leonina is less common. Only in ocelots in Texas was T. leonina detectable in every animal, making it the most common parasite,Pence, D.B. et al. (2003). "Helminths of the ocelot from southern Texas". J Wildl Dis. 39: 683–689. PMID 14567231. and in bobcats in Nebraska it was observed almost as often as T. mystax. Both species of roundworm occur worldwide and roundworm infestation is a very common endoparasitosis. The adult roundworms, up to 10 cm long, live in the small intestine. The female worms produce a large number of eggs, which are released into the environment with the feces. The infective larvae develop in the eggs after about four weeks.
Infection is always peroral and can occur in three ways:
via ingestion with larvae of infected transport hosts, from the mother cat to her pups via the mother's milk (only with T. mystax) or as a filth infection by ingestion of larval eggs.
In principle, roundworms do not require intermediate hosts. Nevertheless, infection via transport hosts such as rodents is the most common route of infection in adult cats. The larvae migrate in the transport host through the intestinal wall into the muscles or internal organs. In the cat, they are released during digestion. In the case of a filth infection, the cat itself ingests larval eggs. The larvae are released in the stomach, pierce the stomach or small intestine wall, and enter the lungs via the bloodstream. From here they are coughed up and, by swallowing the sputum, re-enter the small intestine where they molt into adult worms. In T. mystax, as in the transport hosts, the larvae may also migrate via the bloodstream to other organs (including the mammary gland) where they enter a dormant stage in encapsulated nodules. The hormonally triggered mobilization of these dormant larvae in the mammary gland at the end of gestation is the basis of the third route of infection, which is the most common in kittens. The larvae excreted via the milk enter the intestine of the kittens and subsequently behave as in the case of infection via transport hosts.
In general, the infestation with roundworms in cats remains asymptomatic. Only in the case of a more severe infestation - especially in kittens - unspecific symptoms such as mushy feces and, as a result of a nutrient deficiency, shaggy fur, hair loss, emaciation and dehydration occur. A massive infestation can also lead to growth disorders of the skeleton with deformation of the bones and distended joints in young animals. Very rarely, ileus occurs due to the accumulation of worms or peritonitis due to worms piercing the intestinal wall. In these cases, severe general disturbances ("acute abdomen") occur.
In the case of worms in vomit, the diagnosis can already be made without special examinations. A roundworm infestation can be detected with relative certainty by microscopic detection of the eggs extracted from the feces using the flotation method.
Hookworm infestation Hookworms are common in cats, especially ancylostoma tubaeforme. In contrast, other hookworms such as ancylostoma caninum (main host: dogs) and uncinaria stenocephala (main host: foxes) are observed much less frequently in cats. Hookworms are up to 1.5 cm long and are small intestinal parasites. The larvae of these hookworms are either ingested by eating transport hosts (rodents) or bore through the skin of the cat (percutaneous infection).
Infection with hookworms often remains asymptomatic in cats. In more severe infestations, they can cause emaciation, anemia or diarrhea. As with roundworms, the infection is detected by detecting the eggs in the feces using a flotation method. They are oval, smaller than roundworm eggs (about 60×40 μm in size) and furrowed stages are already visible inside when the eggs are laid.
Gastric worm infestation (ollulanosis) Gastric worms (especially ollulanus tricuspis) are up to one centimeter long and colonize the gastric mucosa, where they nestle in its mucus layer or in the openings of the gastric glands. The entire development of O. tricuspis takes place in the cat's stomach, and the larvae shed by the females develop into the adult worms within the same animal. Other animals become infected by eating vomit from infested cats.
O. tricuspis rarely causes clinical manifestations in domestic cats. A more severe infestation is manifested by occasional vomiting. Other cats, on the other hand, may show more severe clinical pictures with a reluctance to eat, emaciation and dehydration. Infection can be detected by detecting the worms in gastric lavage samples or vomit. Because O. tricuspis is viviparous (larviparous), worm eggs are not detectable in feces and larvae are only exceptionally detectable.Hargis, A.M. et al. (1983). "Ollulanus tricuspis found by fecal flotation in a cat with diarrhea". J. Am. Vet. Med. Assoc. 182: 1122–1123.
Lungworm infestation (aelurostrongylosis) The lungworm aelurostrongylus abstrusus is up to one centimeter long and colonizes the lungs, more precisely the small bronchi and alveoli. Unlike the previously discussed nematodes, lungworms require an intermediate host for their development. The female worms lay eggs from which the larva L1 hatches while still in the airways. This is coughed up, swallowed and, after passing through the gastrointestinal tract, reaches the outside world via the feces. Here, the larvae are infectious in moist environments for up to six months. They penetrate various snails, which serve as intermediate hosts, and develop in them via larva L2 to larva L3. In most cases, however, cats do not become infected by eating snails, but via transport hosts such as amphibians, reptiles, birds and rodents that have previously ingested these snails. After ingestion, the larva bores through the stomach or intestinal wall of the cat and reaches the lungs via the bloodstream. The prepatency period - the time from infection to excretion of the first larvae - is about six weeks.
Lungworm infestation rarely causes symptoms of disease in cats, it is considered self-healing. Only in the case of massive infestation or disturbances of the defense system can respiratory symptoms such as coughing, difficult breathing, sneezing, eye and nasal discharge as well as a reluctance to eat, emaciation and listlessness occur. Very rarely, sudden deaths occur when particularly large numbers of larvae hatch in the airways. Lungworm infestation is established by detection of the larvae, which can be up to 400 μm long, in the faeces by means of the larval emigration method, although they are excreted irregularly in the faeces. More conclusive is detection in lung lavage samples or lung biopsies.Dürr, Binke (2009). "Feinnadelaspiration der Lunge bei zwei Katzen mit Aelurostrongylus-abstrusus-Infektion". Kleintierpraxis. 54: 88–92.
Hairworm infestation Hairworms (Capillaria ssp.) are very thin, 0.7 to 8 cm long nematodes.
Hairworms are most commonly found as parasites in the gastrointestinal tract in cats, for example capillaria putorii. They are considered to cause little disease, but occasionally cause vomiting and diarrhea and, rarely, peptic ulcer disease with anemia.Curtsinger, D. K. et al. (1993). "Gastritis caused by Aonchotheca putorii in a domestic cat". J Am Vet Med Assoc. 203: 1153–1154. PMID 8244862. The eggs of gastrointestinal hairworms are oval, about 60-70 × 35-40 μm in size, and can be detected by flotation techniques.
The lung hairworm (capillaria aerophila) is widespread in wild animals such as hedgehogs or foxes, but very rare in cats. The 25 to 35 mm long worm colonizes the airways. As with roundworms and lungworms, the eggs are coughed up, swallowed and excreted in the feces. Earthworms serve as intermediate hosts, but the parasite is mostly transmitted to cats via intermediate transport hosts. The lung hairworm rarely causes symptoms of disease, only in more severe infestations bronchitis with cough occurs - mostly as a result of accompanying bacterial infections. Detection can be done by fecal examination for eggs or examination of lung lavage samples.
The urinary bladder hairworms (capillaria plica and capillaria feliscati) colonize the urinary bladder. The eggs are excreted in the urine; consequently, detection of infection is only possible from urine sediment. Urinary bladder hairworms can cause cystitis with urinary dysfunction, and in more severe infestations, anemia.
The liver hairworm (capillaria hepatica) parasitizes in the liver and can cause fatigue, vomiting, increased thirst and urination, and jaundice. Infestation can only be diagnosed on the basis of a liver biopsy followed by fine tissue examination of the tissue sample.
Trichinella infestation (trichinosis) Infestation with trichinella (especially trichinella spiralis) is very rare in cats in Central Europe. Trichinae occur worldwide and have no developmental phase in the outside world. Infection occurs through ingestion of larval meat. The larvae bore into the wall of the small intestine where they develop into adult worms. The larvae released by the females enter the skeletal muscles via lymph or blood, where as a holding stage they are the source of infection for other carnivorous and omnivorous animals.
A small infestation of trichinae does not cause any symptoms in the cat. In the case of a pronounced infestation, general disturbances, vomiting and bloody diarrhea may initially occur during the intestinal colonization phase, as in humans (→ trichinosis). Rarely, however, cats develop muscle weakness, gait disturbances, respiratory problems and fever due to myositis caused by the larvae that have migrated into the muscles.
Heartworm infestation (dirofilariosis)