These larva can survive for up to nine months in shallow water, where they are swallowed by grazing animals. After they are swallowed the larva bore into the wall of the small intestine and travel to the lungs through the lymph vessels. After a third molt, the larvae make another trip through the lymph system to the heart and then back to the lungs through the blood. Adults develop in the lungs 18 days after infection and they will produce eggs in 3 to 5 weeks. Coughing is the most common symptom, beginning about 30 days after infection.
Severe infestations can cause pneumonia and suffocation.
Since lungworm eggs hatch before being passed in the feces the eggs generally are not seen by the flotation method. Eggs may be present in the mucous discharge from the nose or be coughed out through the mouth. To see the larva, float a few fecal pellets on the surface of water in a small glass container. After a minute or two hold the container up to a strong light and the 1 mm sickle-shaped larva can be seen with the naked eye as they swim out and fall through the water. After a few hours draw out some of the water place it on a slide and observe the larvae under low power.