11 Superfamily Filarioididae

What is the collective name for members of the Superfamily FILARIOIDIDAE?

Filarial worms

In which anatomical locations are adult filarial worms typically found?

Body cavities, blood, lymph, or subcutaneous and connective tissues.

FILARIOIDIDAE members are _____, meaning they require an intermediate host to complete their life cycle.

Heteroxenous

What type of organism serves as the intermediate host (IH) for all members of Superfamily FILARIOIDIDAE?

A blood-sucking arthropod.

Filarial females are often _____, giving birth to L1 larvae instead of laying eggs.

Larviparous

What is the specific name for the L1 stage of filarial worms?

Microfilaria

What is the infective larval stage for all members of FILARIOIDIDAE?

L3

Where specifically is the infective L3 stage found within the intermediate host?

The proboscis.

Which three families belong to the Superfamily FILARIOIDIDAE?

FILARIIDAE, SETARIIDAE, and ONCHOCERCIDAE.

What is the common name for Dirofilaria immitis?

Canine Heartworm

What are the definitive hosts for Dirofilaria immitis?

Dogs, cats, and wild canids.

Which mosquito genera serve as intermediate hosts for D. immitis?

Aedes, Culex, and Anopheles.

Where are the mature adult heartworms primarily located in the definitive host?

The pulmonary artery and right ventricle.

What is the average length of a female adult D. immitis?

Approximately 30\text{ cm}.

What is the average length of a male adult D. immitis?

Less than 15\text{ cm}.

What morphological feature distinguishes male adult D. immitis from females?

A coiled tail.

How does the width of a D. immitis microfilaria compare to a Red Blood Cell (RBC)?

It is almost as thick as an RBC.

Which diagnostic test for microfilaria is best performed between 16:00 and 20:00 hours?

Modified Knott’s Method

At what age can microfilaria first be detected in a dog's blood?

As early as 6 months old.

During the D. immitis life cycle in the mosquito, where does the 'Sausage stage' develop?

The Malpighian tubules.

How long does the L1 stage of D. immitis stay in the mosquito gut before migrating?

24 hours

After infection of the definitive host, where do L3 heartworms migrate to molt into L4 and L5?

Subcutaneous or subserosal tissues in the thorax or abdomen.

What term describes the compensatory increase in the size of the right ventricular wall in heartworm patients?

Right Ventricular Hypertrophy

How does right-sided heart failure lead to chronic liver failure in dirofilariasis?

Venous backflow causes deoxygenated blood to congest in the liver.

What is 'Progressive Proliferative Endarteritis' in the context of heartworm disease?

Inflammation of the arterial linings caused by mechanical trauma or worm excretions.

Which condition involves heartworms interfering with the tricuspid valve closure?

Caval Syndrome

What is the primary cause of ascites in a dog with dirofilariasis?

Chronic liver disease (secondary to right-sided heart failure).

What are the hallmarks of Caval Syndrome in canine patients?

Severe lethargy, hemoglobinemia, and hemoglobinuria.

Clinical signs such as cough, exercise intolerance, and abnormal lung sounds indicate a _____ heartworm infection.

Moderate

What is the endosymbiotic bacteria that lives inside D. immitis?

Wolbachia pipientis

Why is doxycycline included in heartworm treatment protocols?

To eradicate Wolbachia, causing heartworms to become sterile and reducing post-death pathology.

Which drug is used as an adulticide for D. immitis and where is it injected?

Melarsomine; deep IM in the epaxial lumbar muscles (between L3 and L5).

What class of drugs is used for monthly heartworm prevention?

Macrocyclic lactones

How is heartworm extracted from patients with Caval Syndrome?

Manual extraction using forceps via the jugular vein.

Which diagnostic method is considered the most sensitive for identifying microfilaria and distinguishing species?

Knott’s Method

What does a heartworm Antigen (Ag) test kit specifically detect?

Antigens released by adult female heartworms.

Which staining agent helps distinguish D. immitis from D. repens and Dipetalonema reconditum?

Methylene blue

What is the average length of D. immitis microfilaria?

310\text{ }\mu\text{m}

How does the tail shape of D. immitis microfilaria differ from Dipetalonema reconditum?

D. immitis has a straight tail, while D. reconditum may have a 'button-hook' shape.

How does the movement of D. immitis microfilaria on a slide differ from D. reconditum?

D. immitis undulates in one spot, whereas D. reconditum moves across the slide.

What is the average width of Dipetalonema reconditum microfilaria?

4.7–5.8\text{ }\mu\text{m} (almost half an RBC width).

Besides dogs, what is a primary definitive host for the 'Asian filarial worm' Brugia malayi?

Humans

What condition is caused by the occlusion of lymphatic vessels by Brugia malayi or Wuchereria bancrofti?

Elephantiasis (lymphatic filariasis)

What is the common name for Loa loa?

African eyeworm

Which fly serves as the intermediate host for Loa loa?

Chrysops

What are two characteristic clinical signs of ocular loiasis?

Calabar swelling and presence of worms in the eye conjunctiva.

In terms of reproduction, how does Parafilaria differ from Dirofilaria?

Parafilaria is oviparous (lays eggs), whereas Dirofilaria is larviparous.

What fly genus is the intermediate host for Parafilaria spp.?

Musca

What clinical lesion is characteristic of Parafilaria infection in cattle?

Hemorrhagic subcutaneous nodules with fistulous tracts.

Which fialrial worm is found in the lymph nodes and vessels of man and other primates?

Wuchereria bancrofti

What is the diagnostic indicator for Parafilaria seen in blood from subcutaneous nodules?

Eggs containing microfilaria (L1).

Name four specific macrocyclic lactones approved for heartworm prevention.

Ivermectin, milbemycin, selamectin, and moxidectin.

What is the primary purpose of 'exercise restriction' during heartworm treatment?

To minimize cardiopulmonary complications as heartworms die.

What morphology does a 'sheathed' microfilaria describe, such as in Loa loa?

The L1 larva remains within a protective envelope or sheath.

True or False: A negative microfilaria test definitively rules out adult heartworms in the heart.

False (antigen tests are often needed to detect adults without circulating microfilaria).

In heartworm pathogenesis, what causes 'syncope'?

Temporary loss of consciousness due to reduced blood flow to the brain.

Where are the adult worms of Parafilaria bovicola located?

Subcutaneous and intramuscular tissues.

Which filarial worm family includes Setaria and Stephanofilaria?

Family SETARIIDAE

What is the typical body width of D. immitis microfilaria?

6.7–7.0\text{ }\mu\text{m}

Which condition results in 'decreased oxygenation of tissues' due to arterial damage and vasoconstriction?

Progressive proliferative endarteritis