parasites of dogs/cats: ascarids Flashcards
Family Ascaridae
-Ascarids (roundworms)
includes Toxascaris leonina, toxocara canis, toxocara cati, Baylisascaris spp
Toxascaris leonina characteristics
-Egg: thick smooth shell, single cell
-called northern roundworm
-presence of alae
-3 lips
-no caudal projection on male
-eggs in female
Toxascaris leonina lifecycle
PP: 1-4wks
1. eggs in environment through L1-L3 stages
PPP: 8-10weeks
2. L3 eggs ingested by dog or cat (DH) or a paratenic host
3. Migrate out of GI (mucosal migration) where they develop outside and then re-enter GI as adults
4. Adult release eggs in feces into environment
Toxascaris leonina diagnosis
-fecal flotation, coproantigen, coproPCR
-large adult worms in vomit or stool
Toxascaris leonina clinical signs
-often asymptomatic
- pot belly
- poor growth
-staring coat
-diarrhea
-respiratory signs
-seizures and death (rare)
Toxascaris leonina epidemiology
-common in dogs in western Canada
-found in dogs, cats, wildlife (lynx)
-higher prevalence in young
-wide range of vertebrate paratenic hosts
-not zoonotic
-eggs survive months to yrs in environment (freeze tolerant)
-global distribution including north of 60N
Toxocara canis characteristics
Eggs: shed egg has rough outer shell (need heat, bleach to kill); larvated eggs also have rough shell and presence of larvae
Adult: long skinny alae, 3 lips, caudal projection in male tail, eggs in female worms
Toxocara canis life cycle in young pups (less than 3 months)
PP: 2-8 weeks
1. Eggs in environment (move from single egg, to L1-L3 larvae)
PPP: 4-5weeks
2. Eggs ingested. Undergo Hepatotracheal migration (start in GI tract–>liver–> R heart –>lung –> coughed up and swallowed back down into GI)
3. Adults in GI
4. Eggs released into environment
Toxocara canis life cycle in older (6mths) pregnant dogs
1.Eggs ingested by dog
2. Somatic migration = cysts (movement into the tissues- muscles, kidney, mammary glands)
3. Hypobiotic somatic Larvae in tissues will activate in late pregnancy and move across placenta into fetal liver
4. After puppies born, larvae undergo hepatotracheal migration within and can lead to eggs being shed at 2-3wks old.
**Transmammary infection only occurs in females newly infected late in pregnancy (because the larvae must undergo somatic migration at the time of feeding)
Age intensity curve
Toxocara canis diagnosis
-fecal flotation, coproantigen, coproPCR
-large adult worms in vomit and stool
Toxocara canis life cycle involving a paratenic host
PP: 2-8wks
1. eggs in environment
2. Paratenic host ingests eggs with L3 larvae that enter tissues
PPP: 4 weeks
3. Dog ingests the paratenic host
4. Larvae undergo mucosal migration (exits the GI to feed, then move back inside GI as adults)
5. Adult releases eggs in feces
Toxocara canis clinical signs
-often asymptomatic
-pot belly
-poor growth
-staring coat
-diarrhea
-resp signs
-seizures and death (rare)
Toxocara canis epidemiology
-common in dogs in canada
-global distribution except far north
-canid DH
-prevalence highest in young
-wide range of paratenic hosts (including humans)
-eggs survive months to yrs in environment
Toxocara cati characteristics
-broad arrowhead alae
-Egg: thick rough shell, single cell (similar to canis spp, need genetic testing to tell difference)
Toxocara cati lifecycle
PP: 2-4wks
1.Eggs in environment
PPP: 8 weeks
2. ingested by cat, undergoes hepato-tracheal migration (GI ->liver -> R heart -> lung –>coughed up and swallowed to GI)
3.Adults in GI
4. Eggs released in feces
Toxocara cati life cycle adult/pregnancy
- Eggs ingested by cats
- Somatic migration of larvae to the tissues
3.Larvae shed in milk through lactation
**occurs when female infected in late pregnancy or early lactation
Somatic migration
GI tract -> liver -> R heart -> lung -> muscle or other organs such as brain or eyes
Why does toxocara cati not undergo transplacental migration?
No transplacental most likely due to a mechanism preventing it
Why does infection need to occur later in pregnancy for infection?
Because somatic migration must occur at the time of feeding the kittens.
*somatic migration happens ~3wks, so later infection was occur for feeding and migration to line up properly
Toxocara cati life cycle with paratenic host
PP: 2-4 weks
1. Eggs in environment
2. ingested by paratenic host
PPP:6 wks
3. Cat ingests paratenic host where L3 larvae undergoes mucosal migration
4. Adults in GI tract
5. Adults release eggs in feces
Toxocara cati diagnosis
-fecal float, coproantigen, coproPCR
-large adult worms in stool or vomit
Toxocara cati clinical signs
-often asymptomatic; less severe than T. canis
-pot belly
-poor growth and coats
-diarrhea
-seizures and death (rare)
Toxocara cati epidemiology
-most common parasite in cats in canada
-global distribution
-felid DH
-prevalence highest in young
-wide range or paratenic host (including humans)
-eggs survive months to yrs in environment
Toxocara cati/canis lifecycle involving humans
Infected by visceral, ocular, neural, occult larval migration by either the DH feces or paratenic hosts
**often seen in gardeners, children in sand boxes
Baylisascaris procyonis hosts
-dogs as DH, PH, and mechanical transport host
-causes larval migrans in a range of vertebrate PH (includes dogs and people)
Baylisascaris procyonis characteristics
Eggs: smaller, darker, single cells
**differentiated by fecal float, coproantigen, coproPCR
Baylisascaris procyonis direct lifecycle
- Raccoons ingest eggs with L3 larvae
- Release eggs in environment (2 weeks)
- DH ingest eggs with L3 larvae
Baylisascaris procyonis indirect lifecycle
- Raccoons ingest paratenic hosts with eggs of L3 larvae
- Release eggs into environment through feces (2 weeks)
- PH ingest eggs with L3 larvae
- DH ingests paratenic hosts
**Issues with L3 larvae of Baylisascaris procyonis in Paratenic hosts
-often fatal,
-Dead end host
-L3 larvae enter the brain and cause neurological issues
-no treatment
-diagnosis: clinical signs, histology, serology
Baylisascaris procyonis epidemiology
-present where raccoons are
>southern half of Western provinces, Ontarion, Quebec, maritime provinces
-very rare in dogs
-highly variable infection rate
**Baylisascaris procyonis dog definitive host
-not bad for this dog
-source of eggs in environment
- diagnose: single celled eggs in fresh feces
-Treatment: normal antihelminthic
Baylisascaris procyonis mechanical transport host
-not bad for the dog
-spread of eggs in environment
-diagnose: larvated eggs in fresh feces
-Treatment: none
Control of parasites in dogs and cats
- administer anthelmintic treatment at 2,4,6,8 weeks of age followed by monthly treatments to the age of 6 months
- can synchronize with vaccination
- treat nursing females at 2 weeks post partum
- conduct fecal exams 2-4 times during first yr of life, 1-2 times per yr in adults
- Adults: treat high risk pets and pets with positive fecal tests
What animals are considered high risk?
-young; under 6mths
-highly exposed: dog parks, outdoor access, scavengers, hunters, raw food diets, coprophagic
-highly susceptible: immunocompromised, pregnant, nursing
-animals in high risk households or occupations (service animals)
-clinically ill animals
When should high risk animals be tested for ascarids?
-test at least twice a yr
-treat at least 3-4 times a yr
How to prevent parasites?
-disposal of feces
-prevent predatory or scavenging behaviour
-avoid raw food
-spay females
-avoid soil (gloves)
-wash hands
-cook meat
-wash and cook vegetables
-cover sandboxes
