Helminth

Tapeworms include

Taenia solium, T. saginata, Dipylidium caninum

Roundworms include

Baylisascaris procyonis, Toxocara, Ancylostoma

Taenia saginata is known as

Beef Tapeworm

Taenia solium is known as

pork tapeworm

Definitive host

harbors adult/sexually mature stage of parasite

Intermediate host:

harbors immature stage of parasite

Taeniasis

infection of intestinal lumen with adult Taenia species tapeworms

Cysticercosis:

infection of tissues with larval cysts/cysticerci

Maintenance & Transmission Of T. saginata

cycle between humans & cattle.

Taeniasis in humans Transmission

Humans infected by eating raw or undercooked beef containing cysticerci.

Cysticerci develop into adult worms in human intestinal lumen.

Tapeworm eggs or proglottids passed in stool.

Cysticercosis in cattle Transmission

Cattle infected by consuming food or water contaminated with human tapeworm eggs

Eggs hatch & develop into cysticerci.

Intervention Points to Prevent T. saginata

EDUCATION

T. Solium Cycle Between Swine & Humans- Transmission

Eggs or gravid proglottids in feces passed into environment

Embryonated eggs/gravid proglottids ingested by normal intermediate host (swine)

Oncospheres hatch, penetrate intestnal wall and circulate to musculature

Oncospheres develop into cysticerci

Humans acquire intestinal tapeworm infection via consumption of cysticerci in meat

Cysticercosis in Humans: infection with larval stage of T. solium

Humans= accidental intermediate host

infected by ingestion of eggs

Swine= natural intermediate host

Humans= definitive host 

Cysticercosis in Humans: caused by T. solium Source of infection

taeniasis passes eggs/proglottids in feces

Ingesting food/water contaminated with feces containing eggs/proglottids o Person–to–person spread due to poor hand hygiene practices o Autoinfection: person with taeniasis infects self by ingesting eggs

Cysticercosis eggs hatch and cysts develop where in humans?

brain (neuro-cysticercosis), eyes (ocular cysticercosis) & subcutaneous tissues

One Health Intervention Points to Prevent T. solium- humans

Inspect Pork and cook meat to internal temperature of 165F

Screen humans

Proper waste management

Proper hygiene- handwashing, surveillance

One Health Intervention Points to Prevent T. solium- Swine Cysticercosis

Proper Animal Husbandry- educate farmers, avoid exposure to feed/water

Commercial Vaccine TSOL18 against T/ solium combined with Anthelminitc treatment with Oxfendazole

Taenia solium can cause neuro-cysticercosis in humans. T solium is not endemic in Canada or US but neuro-cysticercosis are reported in those countries. What is most likely source of infection?

Person with Taeniasis who acquired infection living/traveling in endemic Countries.. EGGS= infective stage 

Dipylidium caninum is known as

Flea Tapeworm

Dipylidium caninum (Flea tapeworm) Hosts

Definitive hosts : dogs & cats

Intermediate host : dog or cat flea (Ctenocephalides spp.)

Dipylidium caninum (Flea tapeworm) Transmission

dogs & cats are infected by ingesting infected fleas.

Dipylidium caninum (Flea tapeworm) Prevention

flea control, deworm based on risk.

Dipylidium caninum (Flea tapeworm) Clinical Manifestation

most pets are asymptomatic, may show pruritis, mild GIT disturbance, pass proglottids.

Infections in humans : accidental ingestion of infected fleas carried by dogs & cats. Human infections are rare seen in children.

What is Larva Migrans

Condition where larval worms migrate through various parts of the body of an animal or human 

Forms of Larva Migrans

Cutaneous larva migrans (CLM): larval worms migrate through the skin.

Visceral larva migrans (VLM): larval worms migrate through internal organs.

Ocular larva migrans (OLM): larval worms invade the eyes.

Neural larva migrans: larval worms migrate in the CNS

Larval migrans Causative agents

Baylisascaris procyonis: causes visceral, ocular & neural larva migrans

Toxocara canis & T. cati: mostly cause visceral & ocular larva migrans

Ancylostoma & other zoonotic hookworms mostly cause CLM.

Maintenance of Agents of Larva Migrans

Nonhuman animal vertebrate host and o External environment: essential for development of the agent (embryonation of eggs to become infective).

Baylisascaris procyonis causes and risks

ocular, visceral or neural larva migrans

Playing in dirt is risk factor for infection.

Baylisascariasis Hosts, Maintenance & Transmission

Racoons-reservoir & definitive host.

dogs-definitive host

Embryonation of eggs takes place in external environment.

Humans= accidental hosts by ingesting embryonated eggs with larva, hatch in gut & migrate to viscera, CNS, or eyes

Prevention & Control Of B. procyonis Targeting Source

Reduce environment contamination by identifying, decontaminating & removing racoon latrines near homes.

Discourage racoons by making home environment unsuitable for them

Prevention in other definitive hosts by routine deworming of dogs & exotic species e.g. kinkajous

Preventing Human Exposure

Educate the public about risks of the parasite and practice biosecurity and hygiene 

Visceral & Ocular Larval Migrans-main causative agent and main reservoir host

Toxocara canis- Dogs

Toxocara cati-less extent with cats as reservoir 

Visceral & Ocular Larval Migrans Toxocara canis cause

ocular larva migran

Whar is Essential for maintenance in nature of Visceral and Ocular Larval migrans

External environment & nonhuman animal vertebrate host

Maintenance & Transmission Of Toxocara canis

 Unembryonated eggs take 1 – 3 weeks to become infective in external environment.

Humans=accidental dead-end hosts-infected by ingesting eggs on dirty hands or contaminated food/water- larvae migrate to viscera or eyes.

Diagnosis, Prevention/Control of Toxocara in Animals

Detection of eggs in stool using microscopy

Control- deworming: puppies 3 weeks – 3 months; Kittens 2 – 6 months

Young animals shed high load of eggs with high risk of human infection

Remove dog & cat feces (within 1 week)

 Restrict cats & dogs from children's playgrounds

Zoonotic Hookworms That Cause CLM are cuased by larval stages include

Ancylostoma braziliense: cats are the main reservoir

Ancylostoma caninum: dogs are the main reservoir

Ancylostoma ceylanicum

Maintenance & Transmission Of Ancylostoma

Cats & dogs shed eggs in feces in environment

Eggs hatch & larvae molt into infective stage.

Infective larvae penetrate exposed human skin=accidental & dead-end hosts

Risk Factors for CLM

US east coast.

Areas with free roaming dogs & cats

Beaches- endemic areas Caribbean, South America

Prevention Of Cutaneous Larva Migrans

deworm cats and dogs & dispose of feces

Avoid skin contact with contaminated soil/sand