Small Animal Parasites (need to know)

Nematodes

GI- Toxocara spp., Ancylostoma spp., Trichuris spp.

Circulatory- Dirifilaria sp.

Respiratory- Eucoleus sp.

Urogenital- Dioctophyma sp.

Toxocara canis life cycle

Eggs passed, ingested by host, egg hatches (larva enters blood), larva migrates (lungs, cross placenta, mammary glands)

Toxocara canis typical location

Small intestine

Toxocara canis prepatent period

21-35 days

Toxocara cati prepatent period

8 weeks

Ways toxocara cati infect

Eggs ingested or paratenic host eaten (mouse)

Toxocara canis egg

Toxocara cati egg

Toxascaris leonina egg

Human aberrant host infection (roundworm)

Ingestion of eggs- contaminated soil or eggs on hair (petting dogs/puppies)

Human aberrant host larva locations (roundworm)

Hepatic, cardiac (can be fatal and can cause cardiac arrhythmia), pulmonary, ocular (vision problems, blindness)

Hookworms

Ancylostoma caninum, Ancylostoma tubaeforme (feline), Ancylostoma braziliense (canine and feline), uncinaria stenocephala (canine)

Locations of hookworms

Small intestine- attaches to mucosa (cuts into tissue, blood feeders- secrete anticoagulant), changes during sites (continued hemorrhage)

Life cycle of hookworms

Female and male adjacent attachment sites (continuous copulation and egg production), eggs pass (embryonate- hatch to L1, L2 to L3- L3 infective), ingested/skin penetration- migrates through tissues (lungs- coughed up and swallowed), intestines (maturation)

Hookworms transmission

Ingestion, penetration,transplacental, transmammary

Hookworms zoonotic potential

Cutaneous larval migrations (creeping eruption, ground itch)

Human aberrant host (Ancylostoma braziliense)- L3 skin penetration from contaminated soil, migration only (life cycle not completed)

Hookworm egg

Trichuris vulpis

Whipworm

Anterior (head)- thin section; posterior (reproduction)- thick section, visible in bowel lumen

Feed on blood

Trichuris vulpis location

Cecum/colon- head threads through mucosa and perforates small vessels

Trchuris vulpis eggs

Passed q3 days, matures to L1/L2 stage (infective), extremely resistant (viable for years)

Trichuris vulpis life cycle

Adult in cecum/colon (eggs passed q3 days), larvates in environment, eggs ingested (hatches), matures (small/large intestine), attaches (cecum/colon)

Trichuris vulpis transmission

Ingestion of eggs (viable for years)

Trichuris vulpis diagnosis

Fecal floatation (longer term, don’t float well)

Trichuris vulpis egg

Dirofilaria immitus hosts

Canine- definitive host

Feline/ferret- non infection source

Human- incidental host

Heartworm location

Right ventricle/pulmonary arteries (adults, reproductive in canine)

Aberrant sites- subcutaneous, eyes, CNS, lungs

Heartworm microfilariae

Baby worms, no eggs

Heartworm life cycle

Adults (copulate), microfilaria (float in blood), intermediate host (female mosquito- matures and takes blood meal where larva enters the puncture site), migration (larval development- L4 to L5; heart; aberrant sites)

Heartworm prepatent period

6 months

Heartworm transmission

Intermediate host- mosquito (>30 species)

Heartworm diagnosis

Must differentiate from Acanthocheilonema reconditum (Knott’s test- blunt head hooked tail, not features of heartworm), ELISA (antigen/antibody)

Microfilariae identification- evaluate Buffy coat of hematocrit tube, modified Knott’s test (2% formalin/centrifuge), blood saline prep (microfilaremic)

Dirofilaria immitus

Eucoleus host

Canine and feline

Eucoleus location

Large airways (treaded through mucosa), nasal cavity/frontal sinus

Eucoleus life cycle

Eggs laid in mucosa (slowly enter lumen), coughed up, swallowed (passed in feces), larva become infectious- still within egg (~40 days), egg ingested (hatch in small bowel, penetrate/enter vessels), migrate to lungs (penetrate into alveoli, migrate to large airways)

Eucoleus prepatent period

~40 days

Eucoleus transmission

Ingestion of ova

Eucoleus diagnosis

Fecal flotation, sputum smear (maybe if coughed up), similar to Trichuris spp. (slightly smaller, more barrel shaped, lighter color, rough surface)

Eucoleus zoonotic potential

Eucoleus aerophilus (especially), ingestion of infective ova

Eucoleus spp. egg

A & B

Dioctophyma renale (kidney worm)

Largest parasitic nematode, canine host

Dioctophyma renale location

Usually right kidney, aberrant sites (peritoneum)

Dioctophyma renale life cycle

Eggs in urine (embryonate in water), intermediate host (annelid worm, mature to infective), worn might be eaten by paratenic host, definitive host (eats paratenic/intermediate)

Dioctophyma renale prepatent period

~18 weeks

Dioctophyma renale diagnosis

Urine sediment

Dioctophyma renale zoonotic potential

Human- incidental host, ingest paratenic host (undercooked)

Dioctophyma renale egg

Pearsonema spp. egg

Cestodes

True tapeworms- Dipylidium caninum, Taenia spp., Echinococcus spp.

Pseudotapeworms- Spirometra sp.

Unarmed scolex

No hooks

Dipylidium caninum hosts

Definitive- canine and feline

Intermediate host- flea/louse

Dipylidium caninum life cycle

Indirect

Proglottid passed/disintegrates (eggs released), ingested by intermediate larva- egg hatches (hexacanth in hemocoel, matures to cysticercoid), definitive eats intermediate (by biting themselves and accidentally eating the flea)- matures to adult, attaches to small intestine (armed scolex)

Dipylidium caninum diagnosis

Fecal floatation, segment squash

Dipylidium caninum zoonotic

Ingestion of egg

Dipylidium caninum egg

Taenia pisiformis hosts

Definitive- canine

Intermediate- usually rabbit

Taenia pisiformis life cycle

Indirect

Proglottid passed/disintegrates (eggs released), ingested by intermediate larva- egg hatches (hexacanth in portal veins- migrates to viscera, matures to cysticercus- Cysticercus pisiformis), definitive eats intermediate- matures to adult, attaches to small intestine (armed scolex)

Taenia pisiformis diagnosis

Fecal floatation, segment squash

Taenia hydatigena hosts

Definitive- canine

Intermediate- ruminants

Taenia hydatigena life cycle

Indirect

Proglottid passed/disintegrates (eggs released), ingested by intermediate larva (eating grass with eggs)- egg hatches (hexacanth in portal veins- migrates to viscera, matures to cysticercus- Cysticercus tenuicollis), definitive eats intermediate- matures to adult, attaches to small intestine (armed scolex)

Taenia hydatigena diagnosis

Fecal floatation, segment squash

Taenia ovis hosts

Definitive- canine

Intermediate- ruminants

Taenia ovis life cycle

Indirect

Proglottid passed/disintegrates (eggs released), ingested by intermediate larva- egg hatches (hexacanth in portal veins- migrates to skeletal muscle, matures to cysticercus- Cysticercus ovis), definitive eats intermediate- matures to adult, attaches to small intestine (armed scolex)

Taenia ovis diagnosis

Fecal floatation, segment squash

Taenia pisiformis egg

Taenia hydatigena egg

Taenia ovis egg

Hydatid tapeworms

Reportable to federal government (Echinococcus)

Echinococcus granulosus hosts

Definitive- canine

Intermediate- any kind of herbivore (sheep!), human

Echinococcus granulosus life cycle

Indirect

Proglottid/eggs passed, ingested by intermediate host, egg hatches, larva forms- hydatid cyst in organs (uniocular- 1 big chamber, multiple protoscolices), definitive eats hydatid cyst- 1 protoscolex (1 adult, attaches to small intestine, armed scolex)

Echinococcus zoonotic potential

Extreme (ingest eggs), reportable

Protoscolices

Before scolex (head)

Echinococcus multilocularis hosts

Definitive- feline, fox

Intermediate- small rodents, human

Echinococcus multilocularis life cycle

Indirect

Proglottid/eggs passed, ingested by intermediate host, egg hatches, larva forms- hydatid cyst in organs (multilocular, multiple protoscolices, very invasive- they go everywhere), definitive eats hydatid cyst- 1 protoscolex (1 adult, attaches to small intestine, armed scolex)

Echinococcus spp. diagnosis

In definitive host

Eggs on fecal floatation (taeniid eggs, not definitive), adult identification (only way to know)- from GI tract, purge and then go through it work a fine tooth comb, ELISA

Echinococcus spp. prevention

Essential

Vaccinate sheep, treat at risk dogs (around dead sheep or those who’ve had it before), no risky feeding

Echinococcus spp.

Echinococcus spp. egg

Spirometra spp. hosts

Definitive- canine, feline

Intermediate- aquatic crustacean (copepod); fish, reptile, frog

Spirometra spp. life cycle

Indirect

Unembryonated eggs passed (embryonate in environment, hatch in water- coracidia released), ingested by copepod (develops to procercoid), ingested by fish/reptile/amphibian (develops to plerocercoid), ingested by definitive

Spirometra spp. diagnosis

Fecal floatation, operculated egg (like fluke egg)

Spirometra spp. zoonotic potential

Human ingestion- undercooked fish, copepods in water

Sparganosis- many tissues (can be anywhere, larval stage, >20 years inside abnormal host)

Spirometra spp. egg

Spirometra spp.

Trematodes

GI- Nanophyetus salmincola

Respiratory- Paragonimus kellicotti

Nanophyetus salmincola (salmon poisoning fluke) hosts

Definitive- canine, other carnivores

1st intermediate- fresh water snail

2nd intermediate- salmon

Nanophyetus salmincola

Smallest fluke (0.5-1.1 mm), essentially non-pathogenic (Rickettsial vector- carried by fluke, salmon poisoning)

Nanophyetus salmincola life cycle

Indirect

Adult in small intestine, egg passed, hatches (Miracidium), entry into snail, mature to cercaria (released into water), penetrate into salmonid fish (mature to metacercaria), fish eaten by definitive, matures to adult

Nanophyetus salmincola diagnosis

Fecal floatation

Nanophyetus salmincola zoonotic

Ingestion of undercooked fish

Nanophyetus salmincola egg

Paragonimus kellicotti (lung fluke) hosts

Definitive- canine/feline (carnivores)

Intermediate- operculated snail (1st), crustaceans (2nd, crayfish)

Paragonimus kellicotti pathology

Pulmonary damage (cystic nodules)

Paragonimus kellicotti diagnosis

Fecal floatation, fecal sedimentation (eggs will sink), transtracheal wash, radiography

Paragonimus kellicotti life cycle

Indirect

Eggs coughed up and swallowed (by definitive), eggs hatch, miracidium, penetrates snail, matures to cercaria, exits snail, infects crustacean, encysts in tissues, crustacean eaten by definitive, digestive enzymes breakdown, immature flukes released, migrate to lungs

Paragonimus kellicotti zoonotic

Ingest undercooked crustacean

Paragonimus kellicotti egg

Protozoa

GI- Giardia spp., Cystoisospora spp., Toxoplasma gondii

Circulatory- Babesia canis, Cytauxzoan felis

Giardia duodenalis species complex

A-G