Hunting has a significant impact on local fauna, not only do cats pose a risk to wildlife, but wildlife also poses a threat to animals from injury and infection. There are several diseases that cats can catch from eating infected prey, many of which are parasitic and rely on an ‘intermediate host’ to pass on the infection. Worms, flukes, bacteria, viruses and protozoa are all able to cause infection in cats from hunting and eating their prey.
Lungworm
Capillaria aerophila and Aelurostrongylus abstrusus are worms that live in the bronchioles and alveolar ducts of the lungs where they lay their eggs. Once they hatch larvae travel to the mouth and are swallowed into the stomach and passed out of the body in the feces. Infection occurs when a cat eats a snail or slug infected or a larger prey (such as a bird or a rodent) that has eaten an infected snail or slug. Cats are often commonly asymptomatic to lungworm infection, but when symptoms do present, they usually include:
- Coughing
- Sneezing
- Nasal discharge
- Shortness of breath
- Lethargy
- Anorexia (loss of appetite)
Diagnosis: Fecal flotation or tracheal wash.
Treatment: Anti-worming medication such as Fenbendazole.
Giant kidney worm
This is a rare type of worm (Dioctophyma renale) to infect cats. Female worms can grow to over 60 cm long and 1 cm wide. The adult female kidney worm lays her eggs in the kidney of her host, which then pass out of the body via the urine. Cats become infected by consuming a paratenic host already infected with worm larvae, (usually a frog or fish). During digestion, larvae inside the prey are released, they penetrate the intestinal lining and into the abdominal cavity. From there they migrate to the kidney where they mature into an adult kidney worm; usually, only one kidney is infected, typically the right. The parasite destroys the kidney parenchyma. Symptoms may not be obvious as the cat’s other kidney can often compensate. Symptoms may include:
- Hematuria (blood in the urine)
- Dysuria (painful urination)
- Enlarged kidney
Diagnosis: Urinalysis
Treatment: Surgical removal of the worm from the kidney.
Bladder worm
Capillariasis is the medical name for infection with the bladder worms, Capillaria plica and Capillaria feliscati. The life cycle isn’t completely understood, but what we do understand is that infected animals (which includes cats) pass worm eggs out via urine and into the environment. From there, earthworms ingest bladder worm larvae in the environment, a cat consumes an infected worm. Infective larvae live in the intestinal wall for a period before migrating to the cat’s bladder. Symptoms are rare, but when they do occur they typically include:
- Frequent urination
- Painful urination
- Bladder infection
- Hematuria (blood in the urine)
Diagnosis: Urinalysis
Treatment: Treatment for bladder worms is generally not recommended unless your cat is experiencing symptoms. Anti-worming medication will be administered if necessary.
Stomach worms
Physaloptera spp are parasitic worms that cats acquire when they ingest an intermediate host which has been infected with the worm. Stomach worms need insects as an intermediate host, including beetles, crickets, and cockroaches. Cats can acquire infection from the ingestion of paratenic hosts (small rodents, mice, reptiles) that have eaten infected insects. Once the prey has been digested adult worms grow in the stomach; usually, only a small number of worms (between 1-3) can be found. Infected cats often remain symptom-free; however, when symptoms are present they include:
- Vomiting (chronic and intermittent)
- Dark tarry feces (melena)
- Heavily-infested cats may develop anemia.
Diagnosis: A diagnosis of stomach worms can be challenging as eggs do not float in fecal flotation solution; cats with heavy infestations may have worms in their vomit. Gastroscopy is the best method of diagnosis. This involves placing a plastic tube with a light and a camera through the throat and into the stomach.
Treatment: Removal of the worms via an endoscope or anti-worming medication.
Tapeworm
Two types of tapeworm can infect cats, only one, Taenia taeniaeformis, is acquired during hunting. Cats become infected after consuming rodents infected with larval tapeworm. Cat owners may notice rice-like segments in their cat’s feces or around his anus. A cat with a heavy infestation may lose weight due to competing with the worm for nutrients.
Diagnosis: Fecal flotation or visual inspection of the feces.
Treatment: Anti-worming medication. The geographical distribution of Taenia taeniaeformis is worldwide.
Roundworm
A common parasitic worm, There are many species of roundworms, the most common to infect cats are Toxocara cati and Toxascaris leonina. Infection can occur when kittens nurse from their mother, by eating cats infected with roundworm cysts in their tissue or from the environment. Symptoms of roundworm include:
- Poor coat condition
- Pot-bellied appearance
- Heavily infested cats (particularly kittens) may vomit worms that are white and spaghetti-like
Diagnosis: Fecal flotation.
Treatment: Anti-worming medication.
Intestinal flukes
Alaria alata and other Alaria flukes are flatworms that infect the intestinal tract of cats. They need two intermediate hosts to mature, firstly the snail, and then a tadpole. Cats become infected either by ingestion of a snail, frog or a transport (paratenic) hosts such as birds who have eaten snails or tadpoles infected with the larvae of the fluke. Infection with Alaria flukes usually produces few symptoms in cats.
Diagnosis: Fecal flotation.
Treatment: Praziquantel is the treatment of choice for intestinal flukes.
Pancreatic flukes
The natural host of Eurytrema procyonis is the raccoon; however, they have been known to infect the pancreatic, bile ducts and gallbladder of cats. As with many other worms and flukes listed in this article, snails are the first host to become infected when they consume fluke eggs in the environment. Sporocysts are then expelled from the snail into the environment where grasshoppers consume them. Cats become infected when they consume grasshoppers, the immature flukes, which travel from the gut to the pancreas where they reach maturation before laying their eggs which are passed down the pancreatic duct into the intestine and out via the feces. Not all cats infected with pancreatic flukes display symptoms. It has been hypothesised that large numbers of flukes can lead to pancreatic insufficiency. Pancreatic atrophy and fibrosis can occur, which lead to weight loss and intermittent vomiting.
Diagnosis: Fecal flotation.
Treatment: Praziquantel.
Lung flukes
Paragonimus kellicotti is the most common lung fluke to infect cats. Flukes lay eggs in water and soon hatch into the miracidium form (free-swimming) where they infect snails. Inside the snails, they develop into a cercaria (a second free-swimming larval stage) before leaving the snail and infecting their second intermediate host, crustaceans. Inside the crustacean, they form cysts. Infection in cats occurs when he eats a crustacean infected with lung fluke cysts. The prey breaks down, and the young flukes penetrate the gut wall and migrate to the lungs. Adult flukes lay eggs that pass out of the lungs and are swallowed. From there they enter the stomach and out of the body via the feces. Many cats infected with lung flukes remain symptomatic. Cats with heavy infestations may develop a cough.
Diagnosis: Fecal flotation.
Treatment: Albendazole.
Liver flukes
Opisthorchis felineus is a fluke that infects cats in much the same way as the other flukes listed above. Eggs in the water hatch into the miracidium form (free-swimming) which infects passing snails. Once in the snail, they undergo further developmental changes, leaving the snail as cercaria (a second free-swimming larval stage) and infecting fish, frogs or lizards. Cats become infected when they eat an infected fish or reptile. Once inside the cat, the prey breaks down, and the adult flukes pass through the stomach and to the bile duct and liver. Cats with low numbers may be asymptomatic; a heavy infestation may produce the following symptoms:
- Enlarged liver
- Jaundice (yellow gums)
- Flukes can cause a blockage at the head of the pancreas resulting in exocrine pancreatic insufficiency which can produce greasy feces
- Vomiting
- Diarrhea
- Weight loss
- Lethargy
Diagnosis: Examination of the feces for eggs as well as tissue and fluid samples from the liver.
Treatment: Praziquantel to kill the flukes and supportive care.
Toxoplasmosis
A parasitic disease caused by a single-celled parasite Toxoplasma gondii. This infection is of importance to people because of the potential damage it can cause to an unborn baby if a person becomes infected for the first time during pregnancy. Cats become infected when they consume prey or raw meat containing tissue cysts or ingest cysts from feces. Most cats are asymptomatic to toxoplasmosis unless they are immunocompromised. When symptoms are present they are nonspecific and include:
- Lethargy
- Loss of appetite
- Fever
Diagnosis: Fecal flotation or a blood test to look for antibodies.
Treatment: Treating toxoplasmosis is not necessary unless the cat is displaying symptoms or people in the household are at risk. In which case your veterinarian will prescribe antibiotics.
Coccidiosis
The species of coccidia to affect cats are Isospora felis and Isospora rivolta which inhabit the gastrointestinal tract in cats. Oocysts are shed in the feces of infected animals, and cats acquire the infection when they hunt and consume a rat that has picked up a sporulated (infective) oocyst. Most cats don’t display symptoms of disease with coccidiosis, kittens under six months of age, stressed cats and cats with weakened immune systems are at the highest risk of developing symptoms. These may include:
- Vomiting
- Diarrhea
- Anorexia (loss of appetite)
- Dehydration
Diagnosis: Fecal flotation.
Treatment: It is not possible to kill the parasite, but medication can inhibit coccidial reproduction. A severely dehydrated cat may also need fluids. The geographical distribution of coccidia is worldwide. Part 2: Diseases cats can catch from hunting
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