Verminous pneumonia is an inflammatory condition of the lungs and lower airways caused by parasitic worms, often called lungworms. This disease affects a wide variety of animals globally, including domestic species like cattle, sheep, dogs, and cats, as well as wild animals. The parasites trigger inflammation in the respiratory tract, leading to various respiratory problems. The severity of the illness depends on the worm species, the number of parasites, and the animal’s overall health and age.
Causes and Transmission of Lungworms
The cause of verminous pneumonia is infection by parasitic nematodes, or roundworms, that live in the respiratory system. The specific worm species varies by the host animal. For instance, cattle are affected by Dictyocaulus viviparus, cats by Aelurostrongylus abstrusus, dogs by Crenosoma vulpis, and pigs by Metastrongylus apri.
Transmission occurs through direct or indirect life cycles. In a direct life cycle, such as that of Dictyocaulus in cattle, infective larvae are passed in feces onto pasture. Other animals become infected by ingesting these larvae while grazing. The larvae then migrate from the intestines to the lungs, where they mature into adults.
An indirect life cycle requires an intermediate host. For example, the lungworms affecting cats and dogs use slugs and snails as intermediate hosts. Adult worms in the lungs lay eggs that hatch into larvae, which are coughed up, swallowed, and passed in the feces.
Slugs or snails ingest these larvae, which develop into an infective stage. A dog or cat becomes infected by eating the infected slug or snail. Infection can also occur by eating a transport host, like a bird or rodent, that has consumed the mollusk.
Clinical Signs and Affected Species
The impact of the infection is often more pronounced in younger animals. Their developing immune systems and smaller airways make them more vulnerable to obstruction and severe disease.
The most common clinical sign is a persistent cough that may worsen with activity. As the condition progresses, other signs can appear, including:
- Difficulty breathing (dyspnea) or rapid breathing (tachypnea)
- Nasal discharge
- Decreased appetite and weight loss
- General lethargy or reduced performance
- Rapid, shallow breathing known as “thumping” in pigs
The inflammation caused by the worms, eggs, and larvae can damage lung tissue. This may lead to complications such as pulmonary edema or secondary bacterial infections, which worsen the animal’s condition.
Diagnostic Process
A diagnosis starts with a physical examination and a detailed history of the animal’s environment and behaviors. A veterinarian will assess risk factors like pasture access for livestock or hunting by pets. Listening to the lungs with a stethoscope may reveal abnormal sounds consistent with pneumonia.
The most definitive method is a fecal analysis using the Baermann technique, which recovers live larvae from a stool sample. The sample is suspended in water, allowing larvae to sink for collection and microscopic identification. Because larvae are not shed continuously, multiple samples collected over several days may be necessary.
Imaging techniques like chest X-rays can provide supporting evidence by revealing inflammation patterns in the lungs. More invasive procedures, such as a transtracheal wash or bronchoalveolar lavage, collect fluid directly from the airways. This fluid can be examined for larvae, eggs, or specific inflammatory cells.
Management and Prevention Strategies
Treatment for verminous pneumonia involves anthelmintic drugs, or dewormers, to eliminate worms and larvae from the lungs. A veterinarian selects a drug based on the animal species and suspected parasite. Common effective classes include macrocyclic lactones (ivermectin, moxidectin) and benzimidazoles (fenbendazole, albendazole).
Supportive care is also important for recovery. This may include anti-inflammatory medications to reduce lung inflammation and antibiotics if a secondary bacterial infection develops. Resting the animal during treatment is advised to reduce strain on its respiratory system.
Prevention focuses on interrupting the parasite’s life cycle. Key strategies include:
- Implementing a strategic deworming program for grazing animals, especially during high-risk seasons.
- Using pasture management techniques, such as rotating grazing areas, to reduce larval concentration.
- Discouraging pets from eating potential intermediate hosts like snails and slugs.
- Maintaining good hygiene by promptly removing feces from yards.
- Using preventative deworming products for pets in high-risk areas.