Lung Flukes in Dogs

Although many pets show no signs of infection, in some cases a deep, chronic cough may develop, leading to other symptoms such as lethargy and anorexia. In severe cases of cysts, bursting pneumothorax may occur. 

Lung flukes in dogs can be effectively managed. It is essential that if your pet is suffering from a chronic cough that he be seen by his veterinarian.

Adult flukes affect the lungs of dogs following ingestion of infected snails, crayfish or crabs. The two types of fluke Paragonimus and Paragonimus westermani are most commonly found in China, Southeast Asia and North America. It is thought that up to 80% of freshwater crabs in Asia are infected with this parasite which can be killed with thorough cooking.

The symptoms may vary depending on the severity of the infection. Some pets may remain asymptomatic. Others may present with respiratory signs such as:

• Chronic coughing
• Dyspnea
• Bronchiectasis
• Hemoptysis
• Lethargy
• Anorexia
• Emphysema 
• Pain

In some cases, when the parasite travels to the spinal cord, paralysis may occur.

Types

Paragonimus kellicotti –These can be tolerated by dogs in small amounts;  in heavy infections or when cysts rupture, severe respiratory symptoms may present

Paragonimus westermani – This form can cause severe coughing, often with the presence of blood which may cause tuberculosis to be suspected

Pets who have access to raw seafood, or are more likely to roam may be at higher risk of contracting this disease

The eggs of this parasite mature in water and penetrate intermediate hosts, either snails or crustaceans. When the dog ingests the host the fluke emerges and penetrates the gut, travelling through the diaphragm to the lungs and causing an inflammatory response, forming a fibrous cyst in the lung tissue. From here, eggs are passed through the bronchiole, travelling up the esophagus when the host coughs and are then swallowed, passing out in the feces.  

These adult flukes appear reddish brown, are fleshy, and often reside in pairs in the cysts. They have been known to live for up to 20 year in humans.

Your veterinarian will perform a full clinical examination of your pet and discuss his clinical history and recent behaviour with you. If your rabbit has been suffering from a chronic cough the veterinarian will listen carefully to your dog’s lungs during respiration and expiration. As there a range of chronic conditions that can cause similar symptoms a number of tests may be required. Your veterinarian may choose to do the following diagnostic tests: 

Radiography of your pet’s thorax 

Your pet may require sedation for this procedure to be performed. Your veterinarian may be able to visualise signs of infection due to cysts formed in the lungs that may appear as consolidation or calcifying nodules, particularly in severe, heavy infections. Radiographs will also rule out chronic heart disease or other cardiovascular diseases that may have presented with a deep, chronic cough.

Tracheal wash 

This may show signs of eggs under microscopic investigation. These eggs are very distinctive in size and shape. 

Fecal flotation test

This will be done with a small amount of stool sample from your pet, you may be asked to collect this from home. This may show evidence of infection through visible eggs. 

Hematology, biochemistry, and ultrasound may also be ordered.

There are two main medications considered effective in the treatment of lung flukes in dogs which are able to reduce clinical signs and improve the chest visibly on radiographic investigation. These are fenbendazole and praziquantel. Your pet will likely be prescribed medication for treatment at home for this condition.

Following treatment, your veterinarian may ask you to bring in a stool sample from your dog to check for eggs in the feces. She may also request another blood test to ensure signs of infection such as eosinophilia are gone. 

As this condition has the potential to be passed onto other pets, care should be taken with the infected feces. Furthermore, ensure your dog remains on your property until treatment is complete. To prevent re-infection, monitoring of your dog in environments where access to wildlife may occur, particularly around freshwater, is essential. As this infection is often caused by the ingestion of raw meat ensure that any meat offered to your companion is well-cooked.