Lecture 20- Nematode Parasites of the Urinary tract, Eye, Skin, and Central Nervous System

What are the two species of Capillaria that affect the urinary tract of dogs and cats?

Capillaria (Pearsonema) plica (dogs, foxes, wolves, coyotes, cats) and Capillaria (Pearsonema) feliscati (cats).

Where does Capillaria (Pearsonema) feliscati primarily reside?

In the urinary bladder of cats.

What is the size range of male and female Capillaria worms?

Males: 13-30mm; Females: 30-60mm

Describe the lifecycle of Capillaria species.

Obligate indirect lifecycle with earthworms as intermediate hosts (IH); rodents and birds may serve as paratenic hosts.

What is the prepatent period for Capillaria infections?

~60 days.

What are the clinical signs of Capillaria infection in dogs and cats?

Usually harmless, but may cause occasional cystitis and difficulty with urination.

How is Capillaria diagnosed?

By observing eggs (~65 x 35μm) in a clean urine catch.

What is the treatment and control method for Capillaria infections?

Treated with ivermectin; controlled with environmental hygiene.

What is the common name for Dioctophyma renale?

The giant red kidney worm.

How large can female Dioctophyma renale grow?

Up to 100 cm long and 1 cm in diameter.

Where do adult Dioctophyma renale worms reside?

In the renal tissues of mammalian definitive hosts.

What are important reservoir hosts for Dioctophyma renale?

Wild canids, bears, mink, raccoons, otters.

Describe the lifecycle of Dioctophyma renale.

Obligate indirect lifecycle with aquatic annelids as IH and crayfish, frogs, or fish as paratenic hosts.

How does Dioctophyma renale infect its host?

Infective larvae penetrate the bowel, develop in the peritoneum, penetrate the kidney, mature into adults, and reproduce.

What is the prepatent period for Dioctophyma renale?

~138 days.

How is Dioctophyma renale diagnosed?

By finding eggs (68 x 44μm) in urine sediment.

What is the primary pathogenic effect of Dioctophyma renale?

Destruction of renal parenchyma, often leaving only the renal capsule intact.

Which kidney does Dioctophyma renale prefer to parasitize?

The right kidney.

What can happen if Dioctophyma renale extends into the ureter?

Blockage and tissue destruction can lead to an inability to remove waste (uraemia).

What are potential severe consequences of Dioctophyma renale infection?

Kidney failure, death, inflammation, adhesions, and peritonitis if free worms enter the peritoneum.

What are the common names for Dracunculus species?

Guinea worm, Fiery Serpent.

Where are human Dracunculus infections found, and what is their current status?

In Africa, where they are near eradication due to international public health efforts.

Where do adult Dracunculus worms reside in North American carnivorous mammals?

In subcutaneous tissues, usually on a limb.

How does a female Dracunculus worm release larvae?

By protruding her uterus and releasing larvae into water.

What animals can Dracunculus insignis opportunistically infect?

Pet dogs and cats.

What are the important reservoir hosts for Dracunculus insignis?

Wild canids, raccoons, otters, and muskrats.

What type of habitat is associated with Dracunculus insignis infections?

Aquatic environments where carnivores frequent.

According to a 2018 review, how many cases of Dracunculus insignis were reported between 1980 and 2018?

62 cases (59 in dogs, 3 in cats)

What percentage of infected dogs were ≤ 3 years old in the 2018 review?

43% of cases

What is the primary diagnostic period for Dracunculus insignis?

December to May

What clinical signs are associated with Dracunculus insignis infection?

Lump, nodule, or dermal swelling, typically on a distal limb.

What type of lifecycle does Dracunculus insignis have?

Obligate indirect lifecycle.

What are the intermediate and paratenic hosts for Dracunculus insignis?

Intermediate host (IH): Free-living aquatic copepods.Paratenic host (PH): Frogs (potentially important).

How do definitive hosts acquire Dracunculus insignis infection?

By ingesting infected copepods (IH) or predating on infected frogs (PH).

What happens after ingestion of Dracunculus insignis larvae?

Larvae migrate through the intestinal wall, reach subcutaneous tissues within ~3 weeks, and mature/reproduce in 6-7 weeks.

What host reaction occurs at the end of Dracunculus insignis migration?

Formation of a blister or ulcer at the site of migration tunnel exit.

What triggers female Dracunculus insignis worms to release larvae?

Contact with water, which stimulates the female to protrude her uterus and discharge larvae.

What species does Dracunculus medinensis infect?

Humans residing in Africa.

How does Dracunculus medinensis compare morphologically to other Dracunculus species?

It is morphologically indistinguishable from other species found in humans and animals worldwide.

What is the primary method of treatment for Dracunculus medinensis infection?

Extraction by winding the worm onto a stick.

What complications can arise if the worm breaks during extraction?

Significant host reaction, inflammation, anaphylaxis, and possible death.

What organization is leading the eradication efforts for Dracunculus medinensis?

The World Health Organization (WHO), funded by the Carter Center.

How much has Dracunculus medinensis infection decreased since 1986?

From 3.5 million cases in 21 endemic countries to 126 cases in 30 villages across 4 African countries.

What is the One Health focus for Dracunculus medinensis?

Global eradication of Guinea Worm Disease (GWD).

What discovery in 2016 changed the approach to Dracunculus medinensis eradication?

Recognition that dogs are a competent reservoir host.

What experimental findings supported the role of paratenic hosts in transmission?

Infected copepods were experimentally transmitted to tadpoles and fish, which then infected ferrets as definitive hosts.

How can Dracunculus medinensis transmission be prevented in dogs?

Restricting dogs from eating infected fish entrails.

What are Thelazia worms commonly known as?

Eye worms.

Where do adult Thelazia worms reside in the host?

In the conjunctival and lacrimal sacs.

What species does Thelazia infect?

Dogs, cats, horses, cattle, sheep, and humans.

Match the Thelazia species with their primary hosts:

T. californiensis → ?

T. lacrymalis → ?

T. glucosa → ?

T. callipaeda → ?

T. californiensis: Dogs, cats, people, sheep, deer.

T. lacrymalis: Horses.

T. glucosa: Cattle.

T. callipaeda: People, dogs, cats.

Where is Thelazia distributed?

Cosmopolitan distribution with cases worldwide.

Which Thelazia species affect cattle and horses in North America?

T. glucosa (cattle) and T. lacrymalis (horses).

What countries have canine and human Thelazia infections?

Italy, China, Japan.

What is the taxonomic family of Thelazia?

Spiruidae.

What type of lifecycle does Thelazia have?

Obligate indirect lifecycle.

What are the intermediate hosts for Thelazia?

Flies (Fannia sp.), Musca autumnalis (important for livestock), and Drosophila (fruit flies) in Italy & France.

How do flies contribute to Thelazia transmission?

They feed on lacrimal secretions, ingest eggs, and allow development to L3 larvae within the fly.

How is Thelazia transmitted to the definitive host?

When infected flies return to feed on the host's eyes.

What are the primary clinical signs of Thelazia infection?

Eye irritation, conjunctivitis, and increased tearing (which attracts more flies and enhances transmission).

What class of drugs is used to treat Thelazia infections?

Macrocyclic lactones

How might historical strongyle treatment regimens have reduced Thelazia prevalence in horses?

Routine 8-week ivermectin treatments may have incidentally treated Thelazia infections.

What is the recommended dosage of ivermectin for treating Thelazia?

200 μg/kg once daily (SID).

How can Thelazia be treated topically?

With 1-2 drops of Moxidectin (1%) applied to each eye.

What combination topical treatment is effective for Thelazia?

Moxidectin + Imidacloprid (Advantage Multi).

What is Onchocerca lupi?

An emerging parasitic disease in canines, similar to the parasite responsible for River Blindness in Africa and South America.

Where have cases of Onchocerca lupi been reported in the U.S.?

California, Utah, Nevada, New Mexico, and Oklahoma.

Is Onchocerca lupi zoonotic?

Yes, it is a zoonotic parasite.

Where do adult Onchocerca lupi worms reside in infected dogs?

In ocular nodules and granulomatous masses around the eyeball/conjunctiva.

How is Onchocerca lupi transmitted?

Through the bite of Black Flies (Simulium sp.).

What are the treatment options for Onchocerca lupi?

Surgical removal of the mass; enucleation in severe cases.

How can Onchocerca lupi microfilariae be detected?

Through skin biopsies of the ears, nose, intrascapular, periocular, and umbilical areas.

What did a 2021 case series in New Mexico reveal about Onchocerca lupi?

Among 125 pet dogs, large black dogs were at greater risk, suggesting that vectors are attracted to darker colors.

What preventive measure may help with Onchocerca lupi transmission?

Canine heartworm (CHW) prophylaxis.

What is the natural definitive host of Parelaphostrongylus tenuis?

White-tailed deer.

How does Parelaphostrongylus tenuis affect its natural host?

It is generally nonpathogenic in white-tailed deer.

What type of parasite is Parelaphostrongylus tenuis?

A metastrongyloid parasite with an obligate indirect life cycle.

In which species does Parelaphostrongylus tenuis cause significant morbidity and mortality?

Moose and elk.

Why is Parelaphostrongylus tenuis a significant veterinary health issue?

It causes severe disease in camelid production.

What early signs are noticed in affected animals?

Lateral recumbency, dysorexia, and ADR (Ain't Doing Right).

What are the neurological signs of Parelaphostrongylus tenuis infection?

Ataxia, head tilt, circling, and paraparesis in advanced disease.

What is the seasonal epidemiology of Parelaphostrongylus tenuis?

- Infective larvae are acquired in summer.

Clinical signs appear during fall to early winter.

This pattern aligns with deer activity on pastures.

How susceptible are cows to Parelaphostrongylus tenuis?

Cows appear to be refractory; only two cases have been described.

Can horses be infected with Parelaphostrongylus tenuis?

Occasionally, with age being a potential variable in susceptibility.

What is the prognosis for goats infected with Parelaphostrongylus tenuis?

Disease is often transient, and goats may recover.

What is the prognosis for camelids infected with Parelaphostrongylus tenuis?

Poor prognosis due to late detection in the clinical course.

Why is diagnosis of Parelaphostrongylus tenuis challenging?

There is no available serologic test.

How is Parelaphostrongylus tenuis diagnosed antemortem?

By exclusion, based on clinical signs and diagnostic testing.

What components make up the complete diagnostic database for Parelaphostrongylus tenuis?

Signalment

History (onset, progression)

CBC, chemistry panel

CSF analysis (protein, RBC count)

Creatine kinase (to assess myopathy)

CT scan, diagnostic imaging

What is the definitive diagnosis for Parelaphostrongylus tenuis?

Necropsy.

What is the primary antiparasitic treatment for Parelaphostrongylus tenuis?

Fenbendazole (FBZ) at 20-50 mg/kg SID for 5 days.

What adjunctive treatments help manage Parelaphostrongylus tenuis infection?

Flunixin meglumine (1 mg/kg BID for 5 days) for pain management

DMSO or prednisolone for anti-inflammatory effects (crosses blood-brain barrier)

Why is ivermectin (IVM) not effective against Parelaphostrongylus tenuis?

It does not cross the blood-brain barrier, making it ineffective for CNS infections

What is the prognosis for Parelaphostrongylus tenuis infections?

10-20% mortality in animals unable to stand

75-85% survival in animals able to stand unassisted

How can Parelaphostrongylus tenuis infection be prevented?

Limiting contact with white-tailed deer

Using gravel/limestone barriers to prevent snail-slug migration

Improving pasture drainage

What is a potential downside of prophylactic ivermectin treatment for Parelaphostrongylus tenuis?

It may facilitate resistance in Haemonchus populations.

What type of parasite is Halicephalobus gingivalis?

A free-living, saprophytic nematode.

Where does Halicephalobus gingivalis naturally reside?

In decaying organic matter, mulch, and manure piles.

What is Halicephalobus gingivalis closely related to?

Strongyloides.

What reproductive characteristic is unique to Halicephalobus gingivalis?

Only female worms are found in tissues, suggesting parthenogenesis.