Parasitic pneumonitis

Parasitic Pneumonitis, caused by Parascaris equorum or Dictyocaulus arnfieldi, affects foals and horses, with respiratory signs like exercise intolerance and coughing. P. equorum typically infects foals early in life orally, migrating through the liver and lungs en route to the gastrointestinal tract, leading to verminous pneumonia and "summer colds." Gastrointestinal infection may cause unthriftiness, colic, obstruction, or perforation. Due to widespread persistent environmental contamination and the ability of this parasite to cause pathology during its prepatent period, it is important to preemptively treat foals at risk for infection.

Parasitic Pneumonitis is a condition that can affect foals and adult horses, caused by Parascaris equorum or adults of Dictyocaulus arnfieldi. Clinical signs include exercise intolerance, coughing, nasal discharge, fever, and depression, especially in cases of secondary bacterial infection. P. equorum is common in foals, while D. arnfieldi affects horses of any age, requiring a donkey as a primary host to complete its life cycle.

Clinical Findings:

Foals with parasitic pneumonia exhibit chronic coughing, mucoid or mucopurulent nasal discharge, respiratory distress, and poor body condition. Auscultation reveals abnormal lung sounds and crackles. Signs of intestinal infection such as colic may also be present.

Diagnosis:

Hematological tests show an inflammatory response with mature neutrophilia, hyperfibrinogenemia, and hyperglobulinemia. Thoracic radiography and ultrasound are useful for diagnosis. Cytological analysis of tracheobronchial aspirate reveals eosinophilia. Fecal flotation detects parasite eggs.

Treatment:

Severely hypoxemic patients may require oxygen. Fenbendazole (5 mg/kg) is used to treat P. equorum, with the dose increased to 10 mg/kg after 24 hours if there are no complications. Pyrantel pamoate (6.6 mg/kg) or ivermectin (200 μg/kg) can also be used. D. arnfieldi is treated with ivermectin or moxidectin in adult horses.

Prognosis:

Recovery is excellent with proper treatment. Emphasis is placed on the need for thorough deworming, including donkeys and mules, as they are a source of environmental contamination.

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References:

• Reed, SM. Equine Internal Medicine. Elsevier. 4th ed. 2018. 

• Sellon, DC. Equine Infectious Diseases. Elsevier. 2nd ed. 2014. 

• Zachary, JF. Pathologic Basis of Veterinary Disease. 6th ed. Elsevier. 2017.

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RECOMMENDED LINKS:

• Parasitic Pneumonia Overview. ScienceDirect.

• A Guide to the Treatment and Control of Equine Gastrointestinal Parasite Infections. European Scientific Counsel Companion Animal Parasites. 

• AAEP Parasite Control Guidelines. American Association of Equine Practitioners.