Roundworm—Dirofilaria causes Heartworm which is a form of Filariasis. Filariasis, is defined as disease caused by the presence of filariae in the tissues of the body and is caused by nematodes (roundworms) that inhabit the blood, lymphatics and subcutaneous tissues.

Eight main species of roundworms infect humans but most of these do not end up in the heart like Dirofilaria. These are Dipetalonema does not affect humans, but Wuchereria bancrofti and Brugia malayi cause lymphatic Filariasis (also known as elephantiasis), and Onchocerca volvulus causes onchocerciasis (river blindness).  The other five species are Loa loa, Mansonella perstans, M. streptocerca, M. ozzardi, and Brugia timori.  (The last species also causes lymphatic filariasis.)

To diagnose one of these types of worms you can use blood tests, antigen testing, other lab tests like ELISA, or you can determine which species it is by identifying the adults.    

Symptoms include painful swellings under the skin, lymph duct inflammation, enlarged and painful testicles and fever. Heartworm symptoms include fatigue after exercise; cough and ascites (build up of fluid in the abdomen). Heartworm is passed by mosquitoes and the black fly Simulium.

Diagnosis of Dirofilaria: The doctor takes a blood sample and does a smear and stain of that to look for the immature forms of heartworm. There is also a blood SNAP test which looks a lot like a pregnancy test. The dot turns blue in two places if the animal or human has heartworm. Like this:

Roundworm-Dirofilaria (Heartworm) 1

The heartworm SNAP test

Or you can look at some blood under a microscope with some dye on a special filter and see the mircrofilaria:

The heartworm lifecycle:

Roundworm-Dirofilaria (Heartworm) 2

Heartworm lifecycle

Treatment of heartworm (if heartworm doesn’t kill the animal first) is with diethylcarbamazine or Ivermectin. Prevention is really important and it’s also really important to get your dog tested for heartworm BEFORE giving it the preventative because if the wormer or preventative kills the worms off too quickly, the animal may have an anaphylactic reaction and die. It’s a bad deal. 

Reference: