Exam 2 Flashcards
Life Cycle of Nematodes
o Eggs in dog/cat poo -> o Hatch in environement -> o L1 -> molt -> o L2 -> molt -> o L3 is infectious o Some nematodes lay live larvae
Diagnosis of Nematodes
o Fecal smear
o Fecal float
o Baermann
o Fecal Sedimentation
Basics of Ascarids & Species in Dogs, Cats & Raccoons
o Common o Large w/ 3 lips o Adults live in small intestine o Some zoonotic o Eggs survive in envir for months
Dogs
• Toxocara canis
• Toxocaris leonina
Cats
• Toxacara cati
• Toxocaris leonina
Raccoons
• Baylisacaris procyonis
Toxocara canis Life Cycle
• Adult worms in intestine mate and produce eggs ->
• pooped into the environment ->
• Larva develops within the egg 4wks to the infectious L3 ->
• Dog ingests larvated egg ->
• Larvae hatches in intestine and enters blood stream ->
• Somatic migration
OR
• Tracheal migration
Somatic Vs Tracheal Migration & Ages
Somatic Migration
• Infective larvae accumulate in tissue
• In dogs older than 3-4 mo
• Becomes a parentenic host
Tracheal Migration • In dogs less than 3-4 mo • Larva enters alveolus -> • Coughed up & swallowed -> • Mature is intestine & produces eggs that are pooped out
Toxocara canis Transmission
Ingest a larvated egg from the environment
Eat an infected paratenic host
Transplacental transmission
o Arrested L3 in the tissues of the dam reactivated and migrate to the placenta during pregnancy > infects pups in utero
o Cause damage & inflammation to lungs
Transmammary transmission
o Arrested L3 in tissues of dam are reactivated and migrate to the mammary gland > ingested by pups in milk
o Go directly to small intestine
Toxocara canis Effects on Host
Small numbers
o mild mucoid enteritis,
o mild diarrhea,
o often asymptomatic
Large numbers
o obstruction or rupture of intestine,
o blockage of bile or pancreatic ducts
Adult worms
o Abdominal distension and discomfort,
o diarrhea or constipation,
o vomiting
Migration through lungs
o Respiratory signs
Toxocara cati Life Cycle & Transmission
Life Cycle
• Same as canis
• Very few do somatic migration
Transmission
• Ingest larvated egg from environment
• Eat infected paratenic host (most)
• Transmammary transmission is possible but ONLY if the queen is infected during lactation
Toxascaris leonine Life Cycle & Transmission
Life Cycle
• Adult worms in intestine mate and produce eggs which are pooped into the environment ->
• Larva develops w/in egg to the infectious stage in 1wk
->
• Cat or dog ingests larvated egg ->
• Larvae hatches out in intestine and molts L4 > L5, adult Does not migrate in dogs and cats
Transmission
• No transmammary or transplacental
Baylisacaris procyonis
- Same lifecycle as toxocara canis
- Can undergo somatic migration in any mammal
- Causes visceral & ocular larval migrans in humans
Visceral & Ocular Larval Migrans Due to Ascarids
Visceral Larval Migrans
• Children under 5yo
• Damage due to immune system against migrating larvae
• Asymptomatic or sever symptoms
Ocular Larval Migrans
• Eosinophilic granuloma surrounding larva in retina
• Can be mistaken for retinoblastoma
Treating Dogs/Puppies for Ascarids
Pyrantel pamoate
• Treat every 2 wks from 2wks old to 3mo
Piperazine
• Labeled for 6wk old pups
Fenbendazole
• Labeled for 6wk old pups
• Treat dams daily from day 42 of gestation to 14d post whelping
Macrocyclic lactones
Treating Cats/Kits for Ascarids
- Don’t treat pregnant queens
* Lactating queens & kittens at 2, 4, 6, 8 wks w/ pyrantel pamoate
Basics of Hookworms & Species
- Small, thin (~1 cm long) worms
- Adults live in the small intestine
- Blood suckers
Ancylostoma
o A. caninum - dogs in southern US
o A. brasiliense - dogs and cats in southern US
o A. tubaeforme - rare in US cat
Uncinaria stenocephala
o dogs in the N US
ID IN NOTES
Hookworm Life Cycle in Dogs Vs Cats
Dogs
o Adults mate and produce eggs ->
o eggs released into the environment ->
o L1 hatches out of the egg develops to L3 ->
o Dog eats L3 or paretenic host OR L3 penetrates skin ->
o Somatic or Tracheal migration route ->
o become encysted in tissues
or intestinal mucosa ->
o Some molt to L4, then L5 and then to adult to produce eggs
o No transplacental transmission
Cats
o Most L3 goes on tracheal route through lungs to intestine ->
o Molt to L4, then L5 and then to adult to produce eggs
o No larval bank in cats
Hookworm Transmission
o Ingestion of L3
o Penetration of skin by L3
o Ingestion of paratenic hosts
o Transmammary transmission occurs in dogs, and only occurs during acute infection in cats
Hookworm Damage to Host
o Inject anticoagulants into mucosa & suck blood
o Ulcers where worm feeds
Severe cases
• Caused by many Ancylostoma canium
• intestinal hemorrhage
• anemia
Asymptomatic Infection
• Caused by Unicinaria (inefficient bloodsucker)
Peracute Syndrome due to Hookworms
o transmammary transmission to neonatal pups
o Appear healthy in week 1
o deteriorate rapidly by week 2
o Anemia and bloody diarrhea
o Disease precedes egg production
o diagnosis is presumptive
o Treat immediately if suspected (prognosis is poor)
Acute Syndrome due to Hookworms
o sudden exposure to large number of environmental L3
o Anemia
& Diarrhea with blood
o Clinical disease precedes egg shedding by about a week
o Prognosis is good with prompt treatment
Chronic Compensated Syndrome due to Hookworms
o adult dogs with no clinical signs
o Eggs present in feces on routine fecal exams
o May have slightly low RBC or hemoglobin
o Treatment (cure) is challenging
o encysted larva in the larval bank are not affected by routine anthelmintic therapies
Chronic Decompensated Syndrome due to Hookworms
o adult and older dogs with comorbidities
o Profound anemia in emaciated animal
o Eggs detectable on fecal float
o Prognosis can be good if other factors are addressed
o Treatment requires protein administration + anthelmintics
Hookworm Diagnosis & Treatment of pups & adults
Diagnosis
o Clinical signs – anemia +/- bloody Ds
o Fecal float w/ visible strongyle eggs
Treatment
o Puppies – 2, 4, 6, 8 Pyrantel Pamoate
o Prevent transmammary transmission w/ Fenbendazole or high dose ivermectin
o Use Fecal Egg Count Reduction Test to differentiate between “larval leak” and anthelmintic resistance
Fecal Egg Count Reduction Test (FECRT)
o For Hookworm
o Perform fecal egg count using a quantitative fecal float before treatment and 2 weeks after treatment
o Calculate the % difference
o Number of eggs per gram should decrease by at least 95% two weeks after deworming
o If the number of eggs per gram does not decrease by at least 75%, resistance is likely
Hookworm Control/Prevention
o Very hard to kill o Can freeze Ancylostoma eggs o Dispose of poo o Deworm regularly o Fecal floats
Cutaneous Larval Migrans Due to Hookworm
o In humans
o linear tortuous erythematous, intensely pruritic eruption caused by larva that have penetrated skin
o SE & Gulf Coats of US
o People in contact w/ soil
Basics of Heartworm & Geography
- Dirofilaria immitis
- Long, thin white worm
- Adults live in the pulmonary artery
- Dogs, Cats, Ferrets
- Biologically vectored by mosquitoes
- Filarid nematode produces live microfilariae not eggs
Geographic Distribution
o Mostly SE
o Reportable Dz in WA
Life Cycle of Dirofilaria
o Adults in pulmonary artery mate and produce microfilaria ->
o Microfilaria in blood are picked up by mosquito when it feeds on dog
->
o Microfilaria develop in mosquito to L3 ->
o Mosquito bites dog and deposits L3 on the skin, ->
o Moves into bite wound ->
o Molts to L4 in the skin in the first few days after the bite
->
o L4s migrate through tissues for ~2 months
->
o L5s enter circulation and are carried to pulmonary arteries
->
o Finish maturation to adult and mate in pulmonary arteries (takes about 4 months to mature)
->
o Microfilaria appear in blood 6 months after infection of the dog
Pathology in Dogs due to Dirofilaria
o Severity depends on # of worms, immune status, infection duration, host activity level
o Trauma & damage from worm Ags & excretions of arteries & heart
Caval Syndrome
• Worms fill right atrium and ventricle -> tricuspid valve insufficiency + pulmonary hypertension
• Acute severe lethargy + hemoglobinemia and hemoglobinuria
• Fatal if not treated surgically within 1-2 days
Clinical Signs of Dirofilaria in Dogs
o Signs start when microfilaria in blood o Exercise intolerance and lethargy o Syncope- fainting from lack of blood flow to brain o Soft cough o Acute respiratory distress o Sudden unexpected death
Dirofilaria Diagnosis in Dogs
Blood Ag test (SNAP)
• Detects uterine protein so female worm must be present
• Dogs develop immune complex -> false (-)
Microscopic exam
• Direct blood smear -> worms wiggle
• Knott’s test -> mix blood w/ formalin -> centrifuge -> methylene blue + pellet
Radiograph or echo of heart
Differentiating between Dirofilaria & Acanthocheilonema on Micro Exam
Dirofilaria • Pathogenic • High numbers • Wiggly w/o actually moving • Longer
Acanthocheilonema • Non-pathogenic • Very few • Wiggle moves them • Shorter
Wolbachia
o Symbiotic bacteria that Dirofilaria carries
o Killing bacteria can incapacitate worm
o Must kill bacteria to prevent bacterial infection around dead worms
Treatment of Dirofilaria in Dogs
o Complex
o Strict exercise restriction
o Surgical removal for caval syndrome
Macrocyclic Lactones - moxidectin
• Kills microfilaira & L3 & young L4
Doxycycline
• Kills Wolbachia & prevents secondary inflammation
Melarsomine
• Kills adults & late stage L5
If stable upon diagnosis
• Doxycycline & moxidectin for 2 mo –>
• After 2mo start melarsomine
Prevention of Dirofilaria in Dogs
Test all dogs >7MO yearly
Macrocyclic lactones
• ivermectin,
• selamectin,
• moxidectin
Mosquito repellent
• Pyrethrins
• Neonicotinoids
Dirofilaria immitis in Cats Vs Dogs
Dogs • 30-250 worms • Microfilariae usually present • Large numbers required to cause pathology • Usually easily diagnosed
Cats • 1-3 worms • Microfilariae usually absent • Often fatal • Difficult to diagnose
Heartworm Associated Respiratory Dz in Cats Basics & Treatment
o Pathology in lungs due to migration of worms
o Cough, dyspnea, wheezing
o Very little cardiac issue
Treatment
• Only treat if cat is clinically affected
• Glucocorticoids ONLY
• Reduces immune response -> reduces clinical issue
Diagnosis of Heartworm Associated Respiratory Dz in Cats
Ag test
• Must have at least one female worm to test (+)
Ab test
• Can detect female & male worms
• Only indicates exposure not infection
Ollulanus; basics & transmission
- Cat stomach worm
- Tiny! < 1 mm long
- Usually feral cats and catteries
Transmission:
• Direct by ingestion of larvae or adults in vomitus (NO fecal transmission)
• Internal autoinfection - Entire life cycle can occur in the stomach -> number of worms keeps increasing!
Ollulanus; clinical signs, diagnosis, treatment
clinical signs
• Heavy burdens- chronic gastritis and vomiting
• Can result in emaciation and death if left untreated
Diagnosis
• Demonstrate tiny worms in fresh (nonrefrigerated) vomitus by Baermann
• Endoscopy
Treatment
• 5 day course of fenbendazole
• Tetramisole
Physaloptera; basics & life cycle
- Stomach worm of dogs and cats
- Stout white worms up to 6 cm long
- Most common in the midwest
Life Cycle
• Larvated egg shed in feces
->
• L3 develops in beetles/crickets (Required intermediate host)
->
• Intermediate host can be eaten by birds or rodents (paratenic host)
->
• Paratenic or intermediate host eaten by cat/dog
Physaloptera; clinical signs, diagnosis, treatment
clinical signs
• Chronic gastritis
• Chronic vomiting (even if only 1-3 worms)
Diagnosis • Fecal floats often don’t work • Direct smear better for finding eggs • Adults in vomitus • Endoscopy
Treatment
• Pyrantel pamoate
• Fenbendazole
Strongyloides; basics & life cycle
- Threadworm in small intestine
- Very small- 2 mm long
Life Cycle
• Adults live in small intestine
• Larvae in feces
• Can have entire cycle in environment
Strongyloides; transmission & clinical signs
Transmission • L3 penetrates skin • L3 ingestion • Internal autoinfection • Propagation of infectious L3 by environmental stages leads to highly contaminated environments
Clinical Signs
• Usually asymptomatic
• puppies and kittens are highly susceptible
• Dermatitis due to L3 penetration
• Bronchopneumonia due to lung migrations
• Adults in intestine = watery diarrhea, dehydration
• immunosuppression -> hyperinfection -> emaciation and death
Strongyloides; diagnosis, treatment, control
Diagnosis
• Fecal float to look for larva in feces
• Baermann of fresh fecal samples for larvae
Treatment
• Ivermectin
• Fenbendazole
Control
• Dry environment
• Potentially zoonotic- can be transmitted from dogs to humans
Trichuris Whipworm; basics & life cycle
- Whip-shaped worm in large intestine of dog and cat
- Thin hairlike anterior end embeds in the large intestinal mucosa
Life Cycle
• Ingestion of larvated egg from environment ->
• Eggs shed in feces ->
• larvate in environment
->
• Takes about 1 month in environment to become infectious ->
• Eggs are extremely environmentally resistant for years ->
• Eggs hatch when eaten ->
• larvae develop to adults in intestine
Trichuris Whipworm; clinical signs, treatment, control
clinical signs
• Usually asymptomatic
• Large numbers can cause bloody diarrhea, weight loss, dehydration
• Older dogs tend to have higher burdens
Treatment
• Fenbendazole
• Macrocyclic lactones- milbemycin, moxidectin
• Larva are not susceptible to anthelmintics
• Must treat every month for 3 months
Control
• Difficult
• Eggs survive in environment for a long time
• separate dogs from eggs
• Monthly heartworm preventive labeled for Trichuris
Trichuris Whipworm; Diagnosis
Fecal float
o Beautiful eggs in fecal floats- the fecal jewel
o Floats well but egg output is often low
Antigen ELISA
o used If no eggs on float
Oslerus osleri; basics, life cycle
- Dog lungworm
- Found in nodules at the bifurcation of the trachea
Life Cycle • Female worm deposits egg in trachea -> • hatches immediately -> • L1 coughed up and swallowed -> • infectious L1 larvae are shed in feces
Oslerus osleri; transmission, clinical signs
Transmission
• Direct transmission by ingestion of feces
• Nursing pups when dam licks them and L1 transferred via sputum
Clinical signs
• Hard dry cough brought on by cold or exercise
• Nodules can eventually obstruct air passages
Oslerus osleri; diagnosis, treatment
Diagnosis
• Bronchoscopy- nodules are pathognomonic
• Tracheal wash
• Fecal floatation: look for larvae in feces
Treatment • Difficult • goal is to reduce nodule size and clinical signs • cure is not often achieved • Fenbendazole • Ivermectin
Aelurostrongylus; basics, life cycle
- Cat lungworm
- Relatively common
- Found in lung parenchyma
Life Cycle
• L1 shed in feces (not infectious)
->
• L3 develops in snail/slug
(Required intermediate host) ->
• Intermediate host eaten by birds/rodents/reptiles (paratenic host)
->
• Paratenic or intermediate host eaten by cat
Aelurostrongylus; clinical signs
Asymptomatic
Moderate:
o coughing and anorexia
Severe:
o coughing, panting, shortness of breath, death
Aelurostrongylus; diagnosis & treatment
Diagnosis:
• Fecal float to find larvae in feces
• Baermann to look for L1 larvae in feces
Treatment
• Fenbendazole
• Ivermectin, selamectin- 2 treatments one month apart
