Zoonotic Helminthiasis

ZOONOTIC HELMINTHIASIS
* Helminth: parasitic worm (Greek)
o Platyhelminthes (flukes, tapeworms)
o Nematodes (roundworms)

* Pathogenic helminths are some of most common parasites
* Worlwide distribution
* Toxocariasis (visceral/ocular larval migrans)
o Toxocara canis, T. cati
* Meningoencephalitis
o Balysascaris procyonis
* Trichinosis
o Trichinella spiralis
* Taeniasis
o Taenia soleum, T. saginata
* Hydatid disease
o Echinococcus granulosus, E. multilocularis

TOXOCARIASIS
* Agent:
o Toxocara canis - roundworm of dogs and cats
o Toxocara cati - roundworm of cats (less frequently involved)
* Other names for diseae:
o visceral larval migrans (VLM)
o ocular larval migrans (OLM)

TOXOCARIASIS
Egg
Adult female - head
* Life cycle:
Epidemiology
* Reservoir:
o dogs, cats, small mammals
* Distribution:
o worldwide, most attention in US and UK
o seroprevalence: 3%; 23% in some groups
* Transmission:
o direct or indirect by ingestion of infective eggs from fecal contamination or contaminated soil
o larvae in contaminated undercooked liver from poultry, beef

Clinical features
* Incubation period:
o children - weeks to months
o OLM may be 2-4 years later
* Symptoms:
o asymptomatic to chronic, mild disease (usually)
o predominantly in young children
o increasingly recognized in adults
o symptoms related to migration of larval stage through tissues
* Symptoms:
o VLM - may persist for year or longer
+ fever
+ anorexia
+ weight loss
+ cough
+ eosinophilia
+ rash
+ hepatosplenomegaly
+ death (rarely) due to severe cardiopulmonary and neurologic manifestations
* Symptoms:
o OLM
+ misdiagnosed as retinoblastoma, leading to surgical enucleation
+ endophthalmitis at entry of larva
+ loss of vision
+ eosinophilia rare
+ visceral manifestation rare
+ occurs in children and adults
Diagnosis
* Direct (fecal) examination no use - larva does not develop into adult, no ova passed in feces
* Antibody detection confirmatory only in presence of clinical signs and history
o EIA (enzyme immunoassay)
+ larval antigen extracts from
# embryonated eggs
# cultured TES (Toxocara excretory-secretory antigens) - preferred
+ 1:32

Treatment
* Supportive treatment
* Anthelmentics - effectiveness uncertain
o DEC (diethylcarbamazine)
o Albendazole
o Mebendazole
* Corticosteroids for severe eye problems

Prevention/Control
* Education, especially pet owners
* Routine examination of pets
* Effective deworming program for puppies and kittens
* Removal of feces from environment
* Routine hygiene after handling pets, soil

TAENIASIS
* Agent:
o Tanea soleum - pork tapeworm
o T. saginata - beef tapeworm
* Other names for disease:
o taeniasis - intestinal infection of either tapeworm in animals or humans
o cystiserciasis; cysticercosis - tissue infection with T. soleum larva

Epidemiology
* Reservoir:
o humans definitive host for both T. saginata and T. soleum
* Occurrence:
o worldwide
o highest in Latin America, Africa, SE Asia, Eastern Europe
o T. soleum rare in US, Canada, UK, but increasingly recognized in immigrants

Epidemiology
* Transmission:
Clinical features
* Incubation period:
o taeniasis - eggs appear in 8-14 weeks
o cystercosis - days to years
* Symptoms:
o Taeniasis
+ mild abdominal symptoms
+ occasionally appendicitis or cholangitis from migrating proglottids
+ passage of proglottids (active or passive)
Clinical features
* Cysticercosis:
TANEIASIS
Diagnosis
* Taeniasis
* Cysticercosis
Treatment
* Taeniasis
o praziquantel
* Cystercosis
o praziquentel if active cystercosis, but only under hospitalization due to acute inflammatory reaction; steroids given to control inflammation
o surgical
+ shunt - ventriculoperitoneal shunt to drain CSF
+ cyst removal
+ endoscopic fenestration (hole in cyst wall)

Prevention/Control
* Education
* Identification and immediate treatment of infected individuals
* Freezing meat at -5ºC (23ºF) for > 4 days effectively kills cysticerci
* Irradiation

Agent
Echinococcus granulosus
E. multilocularis
E. vogeli
E. oligarthrus
Disease
Cystic hydatid disease;
unilocular echinococcosis
Alveolar hydatid disease;
multilocular echinococcosis
Polycystic alveolar disease
Rare in humans

UNILOCULAR ECHINOCOCCOSIS
Hydatid “sand”-protoscolices from fluid aspirate of hydatid cyst
Note: normally invaginated; evaginates in saline (right)

Epidemiology
* Transmission:

Clinical features
* Incubation period: months to years
* Symptoms:
o cysts grow slowly, asymptomatic until noticeable mass effect
o compatible with slow-growing tumor
o symptoms depend on location, size, and number of cysts
o anaphylactoid reaction if cyst ruptures/leaks

MULTILOCULAR ECHINOCOCCOSIS
Epidemiology
Clinical features
POLYCYSTIC ECHINOCOCCOSIS
Clinical features
Diagnosis
Serological diagnosis
Treatment
DIPHYLLOBOTHRIASIS
Epidemiology
* Occurrence:
Clinical features
Diagnosis
Treatment
Prevention and Control
ANISAKIASIS
Epidemiology
* Occurrence:
Clinical features
Diagnosis
* Direct examination:
o parasite coughed up
o Fiber optic exam
o laparotomy
* Radioallergosorbent (skin test) developed but not available commercially

Treatment
* surgical excision
Prevention and control
* Avoid ingestion of raw/undercooked fish
* Heating for 10 minutes @ 140ºF (60ºC)
* Freezing:
o “blast freezing” for 15 hours @ -31ºF (-35ºC)
o regular freezing for 7 days @ -10ºF (-23ºC)
* irradiation
* proper cleaning/evisceration as soon as caught

Zoonotic Helminthiasis.ppt