A lung fluke named Paragonimus westermani which is otherwise called the Oriental lung fluke and another species Paragonimus kellicotti, called the North American lung fluke, are commonly found in dogs. Both spend their adult stage inside cysts that are usually formed in the lungs, even though they are occasionally found in other organs too, including the brain.
P.westermani is more prevalent in Southeast Asia, China and South America and they are often transmitted to dogs as well as humans by the consumption of uncooked crabmeat and crayfish. The North American lung fluke mainly occur in otters, minks, skunks and occasionally in dogs in North America, but they affect millions of people elsewhere.
The cysts in the lungs release eggs periodically, and they get coughed up by the dogs and often get swallowed again to be excreted in the feces. For the life cycle to continue, the larvae should find its intermediate hosts snails and finally shellfish such as crabs and crayfish. When dogs eat these fluke infested crustaceans they get infected. After spending their juvenile life in the intestine, the flukes migrate to the dog’s lungs and get ensconced in cysts.
Dogs infected with lung flukes show symptoms such as chronic, intermittent cough, lethargy and weakness that steadily increase. Infected dogs, as well as humans, may eventually succumb to lung fluke infection if no treatment is given.
The infestation is diagnosed when the eggs of the lung flukes are found in the feces or mucous coughed up by the animal. It may be possible to locate the cysts in the lungs through X-ray examination. Lung fluke infection can be successfully treated with several drugs. However, preventing the dog from eating uncooked shellfish will help avoid the infection.