It is well known that hunting has a huge impact on local flora but not only do cats pose a risk to wildlife, wildlife pose a risk to animals from injury and infection. There are a number of diseases which cats can catch from eating infected prey, many of which are parasitic and rely on an 'intermediate host' to pass on infection. Worms, flukes, bacteria, viruses and protozoa are all able to cause infection in cats from hunting and eating their prey.
Many of the diseases cats can catch while hunting pose a serious threat to people as a number of them are zoonotic, meaning they can be passed on from your cat to you.This article became way longer than expected, so in part two, I will cover bacterial and viral infections cats can catch as a result of hunting.
Capillaria aerophila and Aelurostrongylus abstrusus are worms live in the the bronchioles and alveolar ducts of the lungs where they lay their eggs, once hatched 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 often commonly asymptomatic to lungworm infection, but when symptoms do present, they usually include:
- Nasal discharge
- Shortness of breath
- Anorexia (loss of appetite)
Diagnosis is made by finding eggs or feces in a stool or tracheal wash sample.
Lungworms are treated with a worming medication such as Fenbendazole.
Giant kidney worm:
This is a rare type of worm (Dioctophyma renale) to infect cats. Female worms can 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 are then urinated out. Cats become infected by consuming a paratenic host already infected with worm larvae, (usually a frog or fish). Inside the cat the larvae inside the prey are released upon digestion and then 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 kidney parenchyma is destroyed by the parasitic worm.
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 may be made by finding worms in the cat's urine.
Treatment is surgical removal of the worm from the kidney.
The geographical distribution of this worm is in North and South America and occasionally Europe.
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 is known is that infected animals (including cats) pass worm eggs out via the urine and into the environment. The earthworm may ingest the worms where they continue to develop, the worm is then consumed by a cat where it takes up in 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 of bladder worms is based on finding eggs in the cat's urine.
Treatment is generally not recommended unless your cat is experiencing symptoms. Anti-worming medication will be administered if necessary.
Capillaria can be found in North America, Europe, Asia and Africa.
Physaloptera spp are parasitic worms which 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, cockroaches. Cats can acquire infection from 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 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 may either be removal of the worms via endoscope or anti-worming medication.
The geographical distribution of Physaloptera spp is worldwide.
There are two types of tapeworm which 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 your 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 is made by finding tapeworm segments or eggs in the cat's feces.
Treatment is routine worming medication.
The geographical distribution of Taenia taeniaeformis is worldwide.
An extremely common worm to infect cats is the roundworm. There are many species of roundworm, 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 which are white and spaghetti like in appearance
Diagnosis of roundworm is made via examination of the feces for the presence of roundworm eggs.
Treatment is routine worming medication.
Roundworms are found throughout the world.
Alaria alata and other Alaria flukes are flatworms which 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 is made by finding eggs in fecal samples.
Praziquantel is the treatment of choice for intestinal flukes.
Global distribution varies depending on the type of fluke involved. But is generally found in North America and in other temperate regions.
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 they are consumed by grasshoppers. 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 with display symptoms. It has been suggested 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 is usually made by finding eggs in fecal flotation.
Treatment is administration of Praziquantel.
The geographical distribution of Eurytrema procyonis is North America and Asia.
Paragonimus kellicotti is the most common lung fluke to infect cats. The life cycle is quite complex, but to break it down, eggs are laid 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. A cat becomes infected 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. Eggs are laid by adult flukes which are passed out of the lung and 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 is made by isolating eggs in the cat's feces.
Treatment is administration of Albendazole.
The geographical distribution of lung flukes is North America.
Opisthorchis felineus is a fluke which 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 infect 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.
Low numbers may nor produce symptoms at all, however 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
- Weight loss
Diagnosis is made by examination of the feces for eggs as well as tissue and fluid samples from the liver.
Treatment is Praziquantel to kill the flukes and supportive care.
Opisthorchis felineus can be found in parts of continental Europe.
This is another infection 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 ingesting cysts from feces.
Most cats remain symptomatic to toxoplasmosis unless they are immunocompromised, when symptoms are present they are nonspecific and include:
- Loss of appetite
Diagnosis is based on finding oocysts in the cat's feces or a blood test to look for antibodies.
Treatment is often not necessary unless the cat is displaying symptoms or people in the household are at risk. In which case antibiotics will be prescribed.
The geographical distribution of toxoplasmosis is worldwide.
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 become infected when they hunt and consume a rat who has picked up a sporulated (infective) oocyst.
Most cats don't display symptoms of disease with coccidiosis, kittens under 6 months of age, stressed cats and cats with weakened immune systems are at the highest risk of developing symptoms. These may include:
- Anorexia (loss of appetite)
Diagnosis is made by routine fecal examination for oocysts.
It is not possible to kill the parasite, but medication can be given to inhibit coccidial reproduction. A severely dehydrated cat may also need fluids.
The geographical distribution of coccidia is worldwide.