The answers to the clinical case study are the following:
What is the identification of the parasite seen in the image? The identification of the parasite eggs in the image is that of the lung fluke. This patient has paragonimiasis. In this case, given the geographical location, the species is Paragonimis kellocotti or the North American Lung Fluke. Geographical locations known to harbor this fluke are the rivers in Missouri, Arkansas, and Colorado as well as rivers in within the Mississippi basin. Cases in Montreal/Canada, Iowa, and Michigan have been documented as well.
What other species is related, much better known, and produces a similar pulmonary infection but is more common in Asian countries? Most of us are more familiar with Paragonimis westermani which is prevalent in eastern Asian countries. There are other various species found throughout other Asian countries. It is associated with the consumption of raw or undercooked crustaceans such as crabs or crayfish. Some other species outside of Asia associated with paragonimiasis include P. africanus found in Africa, P. mexicanus found in Central and South America
What are the symptoms of this parasitic infection many times confused with? Humans with paragonimiasis usually present with fever and cough, which, together with the presentation of hemoptysis, can be misdiagnosed as tuberculosis. Initial signs may be diarrhea and abdominal pain. Physicians should consider the possibility of paragonimiasis among patients who present with cough, fever, hemoptysis, and eosinophilia. Also, a CT finding specific to an infection is a nodule with a line of opacification that is a result of worm tracking.
It’s important to note that the eggs can be detected in the stool but this is a rare occurrence and actually sputum specimens for analysis are the specimen of choice to detect the eggs. However the lack of sensitivity in detecting the eggs in the sputum makes this not an ideal method of diagnosing the illness. Serological methods are best employed.
What is the treatment of choice for this parasitic infection? Praziquantel is the drug of choice in treating cases of paragonimiasis.
What complications can occur due to an infection with this parasite? The parasite is most known for its pulmonary symptoms that many times mimic the symptoms of an active case of tuberculosis. Complications include pleural effusion, lymphadenopathy and pneumothorax. P. kellicotti worms can also migrate to other areas of the body such as striated muscle, liver, spleen, intestinal wall and the brain. Though the life cycle can not be completed in these cases, the worms can cause complications depending on the organ involved. This is especially true if the flukes make their way to the brain which can result in neurological symptoms such as headaches, visual disturbances and/or seizures.
The importance of a clinical history cannot be overstated. A patient presenting with pulmonary symptoms, hemoptysis, and a history of consuming raw or undercooked crayfish in North America should have an infection with Paragonimus kellicotti be part of the diagnostic workup. This is especially true in a patient with a history of vacationing/whitewater rafting in one of the rivers known to be endemic for Paragonimus kellicotti.