Dirofilaria immitis is a parasitic organism that feeds exclusively on the blood of its host.  In addition to its obvious interaction with its host’s such as dogs, cats, foxes, or even humans to name a few, Dirofilaria immitis also has close ties to the mosquito.  The mosquito serves as an intermediate host so without this important interaction, the parasite would not be able to complete its life cycle.  The interaction with the mosquito can be classified as commensal because the microfilaria, which eventually develop into the parasitic worm Dirofilaria immitis, are allowed to feed and grow inside the mosquitoes gut without causing any harm to the mosquito. 

Looking closer at how Dirofilaria immitis interacts with its host, we can see the parasitic relationship that affects the host species.  When the microfilaria carrying mosquito bites the dog (host in this example), the microfilaria are released into the dogs bloodstream where they grow and develop into mature male and female worms.  These mature worms reside in the heart, blood vessels, and lungs on the host, which makes sense because this is where the most blood is flowing.

Another important interaction that takes place is between Dirofilaria immitis’s bacterial endosymbiont Wolbachia and the host organism.  Wolbachia play an important role in the interaction with the host organism because they regulate the host’s immune response (Simon 2007).

In a study done on dogs in Italy, it was found that all the dogs that were infected with Dirofilaria immitis had significant total anti-Wolbachia surface protein IgG (Immunoglobulin G) levels compared to those of uninfected dogs (Kramer 2005).

Dirofilaria immitis can affect humans, but it is very unlikely due to the human immune response to the parasite.  Humans act as aberrant or dead end hosts, meaning they may become infected from the bite of an infected mosquito, but most often the microfilaria do not develop because they cannot reach sexual maturity (Johnstone 2000).