Opisthorchis Felineus Infection in Cats
The cat liver fluke, also known as Opisthorchis felineus, is a trematode parasite that lives in water. It hitches a ride with an intermediate host, typically the land snail, which is then ingested by another intermediate host, such as the lizard and frog. It is at this point that a cat will eat the host (i.e., the lizard), becoming infected with the organism. The fluke makes its way into the biliary tract and liver, leading to a diseased state.
Liver fluke infection occurs most in cats in Florida, Hawaii, and other tropical and subtropical areas. Approximately 15 to 85 percent of cats with access to intermediate hosts are infected in endemic areas (areas in which this trematode parasite occurs naturally). The typical patient is a young feral cat between the ages of 6 to 24 months with access to local wild life.
Symptoms and Types
The severity of symptoms depend on the severity of infection. However, most infested cats remain asymptomatic. Otherwise, your cat may display one or more of the following symptoms:
- Loss of appetite (anorexia)
- Emaciation/ severe weight loss
- Mucoid diarrhea
- Enlarged liver
- Abdominal distention
- Generalized disability
The life cycle of O. felineus requires two intermediate hosts living in a tropical or subtropical climate. The life cycle is cyclical, with the embryonated eggs passing from an infected cat through its feces. The infected feces is then ingested by the first intermediate host, a land snail. The larvae hatch in the snail, penetrating the host’s tissue and developing sporocysts, a sac like larval stage. The mature daughter sporocysts emerge from the snail and are thereafter ingested by a second intermediate host, usually an anole lizard (but also skinks, geckos, frogs, and toads). They then enter the second host’s bile ducts, where they reside until the host is ingested by a cat.
Infection takes place when the Cercariae are released in the upper digestive tract of the cat and they migrate to the bile ducts (ducts of the liver) and gallbladder, where they mature and shed eggs within eight weeks.
Risk factors for infection are living in a tropical or subtropical climate in which the appropriate intermediate hosts reside, access to an outdoor or indoor/outdoor environment, successful hunting skills, and consumption of an infected intermediate host.
You will need to give a thorough history of your cat’s health, onset of symptoms, and lifestyle behaviors, such as whether your cat is allowed outdoor access. This disease is differentiated from others that might have similar symptoms by taking fluid and tissue samples from the liver or bile for laboratory analysis. It can also be definitively diagnosed from a microscopic examination of biopsied liver tissue, as well as by discovery of eggs in the feces.
If your cat is severely ill, it will need to be hospitalized so that it can be fed and hydrated intravenously, as well as medicated with drugs that will clear the body of the liver fluke parasite. For very ill cats, vitamin D will be administered through the intravenous fluid to promote recovery. Additional medications may also be prescribed. Antibiotics may be required for preventing opportunistic infections, prednisone can be given for lessening the severity of inflammation, and anthelmintic (drugs that kill parasitic worms) substances, such as praziquantel, can be given to kill the trematode spores, either intravenously, or by mouth if your cat is being treated on an outpatient basis.
Living and Management
Your veterinarian will want to examine your cat from time to time to check clinical signs such as liver enzymes and fecal sedimentation. You should also watch for signs such as loss of appetite, body condition and weight. In most patients that have been given appropriate treatment in time, before severe damage may have occurred to the liver or gallbladder, an uncomplicated recovery is expected.
- Restrict outdoor access
- Medication to prevent infestation may be required for outdoor cats every three months in endemic, tropical climates
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