Dirofilaria immitis


Dirofilaria immitis, the heartworm or canine heartworm, is a parasitic roundworm. It is a sort of filarial worm, a little string like worm, that causes dirofilariasis. It is spread from the host through the bites of mosquitoes.

The complete host is the dog, however, it can also contaminate felines, wolves, coyotes, jackals, foxes. Also, it can affect different creatures, for example, ferrets, bears, seals, ocean lions and, under uncommon conditions, people.

Dirofilaria immitis is ordinarily called the “heartworm” but the grown-ups regularly dwell in the aspiratory blood vessel framework (lung courses). They may reside in the heart of their host to cause infection.

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Also, a major impact on the health of the creature is a sign of harm to the lung vessels and tissues. Sometimes, grown-up heartworms relocate to the correct heart and even the considerable veins in substantial invasions.

Heartworm contamination may result in genuine infection for the host, with death ordinarily as the aftereffect of congestive heart failure.


Scientific NameDirofilaria immitis

Vernacular Names

English: Heartworm, dog heartworm nematode, canine heartworm nematode.


Canine heartworms were first found in 1856 on the southeast shore of the United States. A disease by a similar operation was then found in felines in the 1920’s.

However, it was not until 1952 that a human contamination by Dirofilaria immitis recorded in America. From that point forward, most analyses of a case have been in the United States and Canada.

Origin Of Dirofilaria Immitis

They are originated from South America, where a disclosure of the canine parasite was first made in 1847. But a report was not distributed until 1875. The primary human case occurred in Brazil in 1887 alongside the principal cat case in 1921.

There is confirmed evidence for the presence of the specialist for a long time. In 1586, Chez Iean Wolfe made a portrait of a “beast” found inside the heart of a horse, later recognized as D. immitis.

Fossil Records Of Dirofilaria Immitis

The fossil record of heartworms or different pathogens is generally poor. Since they frequently live inside their hosts or vectors. They may experience some lifecycle stages far from their hosts, are little and need hard tissues.

This is especially evident for infections, microbes and protozoa. Also, evident for different delicate bodied metazoan parasites, for example, helminths or pitifully sclerotized arthropods.

Body fossils of heartworms are uncommon and normally confined to locales of remarkable fossil conservation. Especially those still connected with the remains of their hosts giving a direct proof of parasitism.

source: www.nature-microscope-photo-video.com

Trademark follows or pathologies in the skeletons of their hosts are more typical. However, they can follow all the more persistently over longer timescales.

On the other hand, the ordered partiality of the offenders isn’t in every case simple to unravel. The fossil record of heartworms viewed on different events with some others focusing especially on marine parasites or earthbound pathogens.

The fossil record can also give guide confirmation to the nearness of parasite. However, they may have affiliations some of which may now end. Also, the effect of heartworms on their hosts is in the topographical past.

Distinctive Features

The distinctive features of Dirofilaria Immitis include an autonomous, motile, some of the time feeding, formative stage in the existing history of a worm or creepy crawlers. Normally experiences transformation or a shed to end up a grown-up.

Heartworms have a few phases of hatchlings. L1 are the microfilaria in the blood of the tainted creature. Also, these are sucked up by the mosquito while it is bolstering. It sheds from an L1 to L2 and again from an L2 to L3 in the mosquito before it can taint a creature.

L3 hatchlings are removed from the mosquito’s mouthparts while the mosquito is bolstering and tunnel through the skin of the host. Inside the host, it sheds twice, from an L3 to an L4. Moreover, after that from an L4 to an L5. The L5 hatchling will turn into the grown-up once it develops.


In spite of the fact that at one time restricted toward the southern United States, heartworm has now spread to almost all areas where its mosquito vector is also present.

Transmission of the heartworms happens in the majority of the United States and the hotter locales of Canada. The most astounding contamination rates are inside 150 miles of the drift from Texas to New Jersey.

But, along the Mississippi River and its major tributaries. It has also seen in South America, southern Europe, Southeast Asia, the Middle East, Australia, Korea, and Japan.


Dirofilaria immitis is a cylindrical-shaped, slim white worm. As a nematode, it has fingernail skin with three main external layers made of collagen and different mixes.

The external layers are non-cellular and are emitted by the epidermis. The fingernail skin layer ensures the nematodes so they can attack the stomach related tracts of creatures.

Nematodes have longitudinal muscles along the body divider. The muscles are diagonally organized in groups. Dorsal, ventral and longitudinal nerve ropes are associated with the primary body of the muscle.

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Both genders are unique. The grown-up male, estimating 12-16 cm, is littler than the grown-up female, which is 25-30 cm. The male has a back-end spirally wound and a tail with numerous alae.

These are the thickenings of the fingernail skin. The female back is straight. Both genders have a mouth, a filariform esophagus, butt-centric pore, excretory pore and a nerve ring.

The male has an original vesicle and testis while the female bears an ovary and oviduct. The hatchlings, called microfilariae, are 307-322 micrometers in length and 6.7-7.1 micrometers wide.

They have a straight back end paying little heed to the sex and a decreased front end. They have no cephalic snare and are not ensheathed.

Range length: 12 to 30 cm.

Other Physical Features: ectothermic; heterothermic; bilateral symmetry

Sexual Dimorphism: female larger; sexes shaped differently


The mosquito ingests Dirofilaria immitis hatchlings, microfilariae (first stage adolescent, L1), after a blood meal from an or another tainted host. Hatchlings are then passed back to canines where they form into grown-ups.


Dirofilaria immitis is present in numerous tropical, subtropical and calm districts of the world. Especially sticky regions and stream valleys where ecological conditions harbor the reproducing of mosquito vectors.

Food Habits

The middle host may have a place with a few types of mosquitos, for example, the Aedes, Anopholes, and Culex. The essential authoritative host of D. immitis is the dog.

But, other unusual authoritative hosts are felines, fox, coyote, wolf, ocean lions, harbor seals, research center ferrets, ponies, bears, raccoons, wolverines, muskrats and red pandas. Hatchlings don’t develop to grown-ups in people.

Life Span Of Dirofilaria Immitis

The grown-ups can stay in the heart for up to 7 years. Microfilariae can stay in the course of the mosquito for up to 2 years. In people, the parasites cannot achieve the grown-up stages and stay in the larval stages.

source: www.bioweb.uwlax.edu

No microfilariae are ever present in the blood of people on the grounds that the parasites can never completely create to shed the microfilariae into the blood.

Behavior Of Dirofilaria Immitis

Nematodes inside the Secernentea have phasmids, which are unicellular organs. Phasmids also function as chemoreceptors. Females may create pheromones to pull in males.

Nematodes have papillae, setae and amphids as the fundamental sense organs. Setae distinguish movement (mechanoreceptors), while amphids identify synthetics (chemoreceptors).


Known Hazards

Since people often keep cats and dogs as pets, heartworm diseases are of significance to veterinarians. In heavy contaminations of cats and dogs, the worms can cause circulatory pain and can even cause deaths in them.

Once in a while, heartworms can taint people unintentionally and start to create knobs in the lungs or different subcutaneous tissue.

Fun Facts

Apart from all the hazards, there are also some fun facts about the Dirofilaria Immitis:

fun facts

Although, these fun facts are quite interesting yet there are some dangers as well.


  1. www.eol.org
  2. www.invasives.org.za
  3. www.web.stanford.edu
  4. www.dallasmetropaws.com
  5. www.researchgate.net
  6. www.heartwormsociety.org

Amna Shaheen

I have done Bachelors in Computer Software Engineering from Foundation University in 2017. Now, I am doing MS in Project Management and I am a blogger at TapeDaily. I am very passionate about plants and animals. I like to study about them, so I write blogs that are related to plants and animals.

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