Veterinary Parasitology CH4 P1 - Nematodes of Dogs and Cats

Part 1 of study material for Chapter 4 of Diagnostic Parasitology for Veterinary Technicians. For class BIO225 at MWCC.

Spirocerca lupi

Esophageal worm - "Coiled tail"

• Found: In tropical regions, sometimes Southern U.S.

• Affects: Cats and dogs

• Paperclip shaped egg; bright red/pink 3-7cm adult worms

• Cause of infection: swallowing eggs

• Found in fecal flotation or vomit

• Causes nodules or granulomas in esophagus or stomach

• Symptoms: trouble swallowing, regurgitation, hypersalivation

• Prepatent period: 6 months

Physaloptera sp.

Stomach worms - "Bladder wing"

• Found: Worldwide​

• Affects: Cats and dogs​

• Thick-shelled larvated egg; Creamy white, 1.3-4.8 cm adults; Ovoviviparous​

• Found on fecal flotation if solution has SG > 1.25 (most clinics use 1.2-1.25)​

• Can be seen in vomit; often mistaken for ascarids if seen grossly — must examine eggs​

• Stomach or small intestine; suck blood from mucosal surface​

• Cause of infection: Ingestion of eggs​

• Symptoms: Vomiting, anorexia, dark stool​

• Prepatent period: 56-83 days

Ollulanus tricuspis

"Small cat hair"

• Found: Worldwide​

• Affects: Felines only​

• Trichostrongyle​

• Symptoms: Chronic vomiting​

• Found in vomit flotation or smears​

• Adults only 1mm long; have three tail processes​

• Larviparous — release third stage larvae that are immediately infective​

• Can be ingested in vomit

Toxocara canis, T. cati, Toxoscaris. leonina

• Roundworms - "Arrowhead"

• Found: Worldwide​

• Affects: Canines and felines​

• Cause of infection: Ingestion of larvated eggs​

• Adults 3-18 cm, usually coiled in feces or "spaghetti vomit"​

• Symptoms: Vomiting, diarrhea, constipation, bowel obstruction, "pot-belly"​

• Does not attach, undulates to stay in the intestine​

• Oviparous; single cell egg released; larvae develop on ground to L2 and ingested​

• L2 released from eggs and migrate to host lung, coughed up and swallowed​

• Adults mature in host small intestine; dormant in adult female host- become active due to pregnancy hormones of host​

• T. canis can cross placenta and milk and can infect babies; also zoonotic​

• Treatment: vermifuge (piperazine or pyrantel) — paralyzes adults, pass in feces​

• Treatment: vermicide - (thiabendazole or mebendazole) —kills parasite in host and broken down

Baylisascaris procyonis

Raccoon roundworm

• Found: North America (MS-OH basin)

• Affects: Raccoon host but can parasitize many species

• Cause of infection: Ingestion of eggs

• Egg similar to T. canis but slightly smaller​

• Symptoms: Can cause bowel obstruction in raccoon or dog​

• Zoonotic infection can lead to neurologic larva migrans

Ancylostoma caninum, A. tubaeform, A. braziliense, Uncinaria stenocephala

Hookworm

• Ancylostoma: worldwide, Uncinaria: N. America​

• Ancylostoma: curved mouth; Uncinaria: hooked nose​

• A. caninum: dog, A. tubaeform: cat, A. braziliense: cat and dog​, Uncinaria: dog only​

• Cause of infection: Ingestion of eggs or through skin​

• Attach to mucosa of small intestine, feed on blood, secrete anticoagulants​

• Ancylostoma: three pairs of ventral teeth​

• Symptoms: anemia, dark tarry stool, especially kittens and puppies​

• Can spread through placenta and milk​

• Oviparous: morulated egg released in feces, develop into L1 in environment​

• L1 hatch, grow and molt into L2, grow and molt into infective L3​

• Migrate to lungs, coughed up, swallowed ​

• Matures in small intestine​

• Prevention: Interceptor and Heartgard Plus ​

• Treatment: mebendazole or fenbendazole

Strongyloides stercoralis, S. tumefaciens

Threadworms - "Round-like shape"

• Found: Worldwide​

• Affects: Dogs, cats and humans​

• Cause of infection: Skin infection or placenta or milk passage​

• Symptoms: diarrhea, especially in puppies, zoonotic​

• Parthenogenesis: female produces viable ova without fertilization​

• No parasitic males​

• Adults found in small intestine ​

• Adult female has cylindrical esophagus​

• Larvated eggs released but hatch in host intestine releasing L1 often found in feces​

• Larvae have rhabditiform esophagus​

• L1 are free-living in environment, L3 are infective​

• Prepatent period: 8-14 days

Trichuris vulpis, T. campanula

Canine whipworm, Cat whipworm - "Hair tail"

• Found: Worldwide (Trichuris vulpis/canine whipworm common in USA)

• Adults attach to wall of cecum and colon of dog, suck blood​

• Elongated, trichurid egg, single cell, bipolar plugs visible​

• Prepatent period: 70-90 days​

• Eggs only released every third day​

• Found in feces but heavy and don't float well; fecal centrifugation preferred​

• Eggs hatch in environment, grow into L1​

• Only pass by ingestion of egg​

• Symptoms: Diarrhea, anemia, mucus-coated stool​

• Resistant, needs follow up treatment to kill all adults​

• Not zoonotic

Dirofilaria immitis

Heartworm - "Dread thread"

• Found: Warm climates worldwide

• Affects: Dogs, cats, ferrets, humans (incidental only)

• Definitive host: Dog​

• Intermediate host: Female mosquito​

• Adults found in right ventricle and pulmonary arteries of dog​

• Commonly found in aberrant sites: brain, eye, skin​

• Prepatent period: 6 months​

• Larviparous: microfilariae released into host bloodstream, picked up by female mosquito​

• Molt into L2 and L3 in mosquito digestive tract​

• L3 passed into dog by mosquito, mold into L4, L5, adults in heart

Aelurostrongylus abstrusus

Feline lung worm

• Affects: Cats only​

• Found: Worldwide​

• Cause of infection: Ingestion of larvae (360mm long)​

• Adults live in respiratory bronchioles​

• Larvated eggs​

• S-shaped curve and dorsal spine on larvae​

• Larvae present in fecal or tracheal wash​

• Prepatent period: 30 days

Oslerus osleri

• Unique in that L1 phase is infective

• No outside development is necessary​

• Dogs are definitive host​

• Cause of infection: Ingestion of larvae 232-266 um, often from mom to puppies via the mouth​

• Adults found at the bifurcation of trachea in nodules​

• Prepatent period: 10 weeks

Dioctophyma renale

Canine giant kidney worm

• Adults found in right kidney​

• Found: In North America and Europe​

• Cause of infection: Ingestion of larvae in annelid worm (ringed worms including earthworms and leeches) - can go through fish or frogs as paratenic hosts​

• Parasite eats through the parenchyma of kidney, leaving only capsule behind​

• Largest nematode. Males 30-40cm, Females can be 1m​

• Barrel shaped bipolar yellow brown egg found in urine sediment​

• Can "wander" into peritoneal cavity

Pearsonema plica (dog), Pearsonema feliscati (cat)

Bladder worm

• Adults found in bladder ​

• Larvae get into Earthworms​

• Definitive host ingests worms​

• Eggs can be confused with whipworms​

• Bipolar flattened plugs

Rhabditis strongyloides

• Facultative parasites — usually live in soil​

• L1 larvae get in through skin — red, crusty, loss of hair where inflamed​

• Larvae can be seen on skin scraping, even on cattle​

• L1 can look like microfilariae of D. immitis if taken from a bloody skin scraping

Dracunculus insignis

Guinea worm - "Small dragon"

• Adult found in subcutaneous tissues of dog​

• Female 120cm; Male 2-3cm​

• Female produces draining ulcer on dog's skin; end of female comes out of ulcer​

• When she comes in contact with water, uterus prolapses and releasing L1 in water​

• L1 ingested by microscopic crustaceans (copepods) as intermediate host and molt to L3​

• Dogs infected by drinking water with these crustaceans​

• Female must be surgically removed​

• L1 must be differentiated from D. immitis and R. strongyloides

Thelazia californiensis

Eyeworm - "Nipple saliva"

• Found: In North America​

• Adults found in conjunctiva and lacrical duct​

• Larvae passed by face fly, Musca autunmalis​

• Surgically removed from eye