Parasitology. Nematodes

Intro. Nematodes. Infective in Egg Stage. Infective in Larval Stage. Tissue Nematodes

Mutualism

interaction between two or more species where each species has a net benefit (+, +)

Commensalism

association between two organisms where one benefits and the other derives neither benefit nor harm (+, 0)

Symbiosis

close union of two dissimilar organisms (living together in intimate association)

Parasitism

relationship between species where one organism (parasite) lives on or in another organism (host) causing it some harm and is adapted structurally to this way of life (+, -)

Facultative Parasite

may resort to a parasitic lifestyle but does not rely on host for completion of life cycle

Obligatory Parasite

cannot complete its life cycle without relationship with suitable host

Endo-parasite

parasite that lives within a host and causes an infection

Ecto-parasite

parasite that lives on a host and causes an infestation

Definitive Host

supports the adult or sexually reproductive stage necessary for parasite survival

Intermediate Host

supports the immature or non-sexual reproductive forms that are necessary for parasite survival.

Transfer Host

can move or relocate parasite stages from one location to another

Vector Host

transfers parasite to the next host. acts as a definitive or intermediate host

Reservoir Host

serves as a source of infection and potential reinfection of humans. sustains a parasite within a population/ecosystem

Exposure

being in contact with an infectious organism

Colonization

presence of infectious agent on/in a body surface without causing disease in the person

Infection

invasion and growth of infectious agents germs on/in the body

Sign

any objective evidence of disease that can be observed by others (e.g. rash fever, pulse, lump)

Symptom

subjective evidence of disease only apparent to the patient (e.g. back pain or fatigue)

Incubation Period

period between exposure to infection and the appearance of the first signs and symptoms

Latency

time from infection to infectiousness (being able to pass the infection)

Infection

first step; occurs when infectious agents that may cause disease enter the body (invasion) and begin to multiply. transitions to disease when cells are damaged

Disease

characterized by signs and symptoms of an illness and tissue damage leading to pathological features/conditions

Infectivity

ability of an organism to establish an infection

Invasiveness

ability of an organism to spread to adjacent or distant tissues

Pathogenicity

ability to produce substances that damage tissues

Parasite Virulence

ability of a parasite to cause disease and tissue damage to host

Host Resistance

ability of an organism to limit growth, reproduction, or survival of invading parasite

Eosinophilia

increased production of eosinophils (a white blood cell) that is part of host defence against parasitic infections

Erythropoiesis

increased production of red blood cells due to anemia caused by parasite feeding

Neoplasia

uncontrolled proliferation of cells due to excessive parasite induced tissue damage and repair

Toxocara canis/cati

Dog/Cat Roundworm

Enterobius vermicularis

Pinworm

Pinworm Life Cycle (normal)

ingestion of eggs

eggs hatch in small intestine

mature in large intestine

lay eggs on anus

contaminate fingers

Pinworm Life Cycle (abnormal)

migrate to appendix or vagina → uterus → fallopian tubes

Pinworm Epidemiology

cold climates, young children, group infections

Pinworm Transmission

direct (anus → fingers → mouth) or indirect (airborne eggs and fomites)

Pinworm Pathology

pinpoint necrosis (large intestine)

benign tumors and itching (perianal area)

appendicitis (appendix)

vaginitis (vagina)

scarring and salpingitis (fallopian tubes)

irritability, insomnia, convulsions (toxic metabolites)

Pinworm Diagnosis

anal swab with Q-tip (eggs)

scotch tape test (eggs)

worms in feces (mature parasites)

Pinworm Treatment

mebendazole - has to be repeated after 3 weeks

Pinworm Prevention

personal hygiene

mass chemotherapy (group treatment)

detergent

sunlight/UV light

Trichuris trichiura

Whipworm

Whipworm Life Cycle

eggs are ingested

hatch in small intestine

migrate to rectal area

attach into gut wall

eggs in feces

Whipworm Epidemiology

young children, night soil as fertilizer, warm climate with rain (southeastern U.S.)

Whipworm Pathology

tissue injury necrosis (intestine)

hemorrhage (intestine)

bacterial infection (intestine)

pain (intestine)

loss of appetite

Whipworm Pathology (heavy infection)

anemia

dysentery (diarrhea but with blood)

fever

rectal prolapse

Whipworm Diagnosis

fecal smear (eggs)

protoscopic exam (mature worms)

colonoscopy (mature worms)

Whipworm Treatment

mebendazole

Whipworm Prevention

sanitary disposal of night soil

personal hygiene

Ascaris lumbricoides

Giant Roundworm

Giant Roundworm Life Cycle

ingest eggs

hatch in small intestine

migrate to lungs

larva are coughed up and swallowed

mature in small intestine

lay eggs

Giant Roundworm Epidemiology

warm moist climate (southeastern U.S.)

areas that use night soil as fertilize

pigs are common reservoir hosts

Giant Roundworm Pathology (lungs)

petechial hemorrhage

sero-cellular exudate

allergic reaction to molting fluid

cough/asthma-like symptoms

Loeffler syndrome

Giant Roundworm Pathology (small intestine)

no tissue invasion

feeds on intestinal contents (not on tissue)

moves against peristaltic movement

Giant Roundworm Pathology (abnormal)

intestinal obstruction

appendicitis

gut penetration

Giant Roundworm Pathology (abnormal migration)

pancreatic duct

bile duct

esophagus or trachea

mouth

ears

Giant Roundworm Diagnosis

fecal smear (eggs)

Giant Roundworm Treatment

albendazole

Giant Roundworm Prevention

sanitation of night soil, washing food, personal hygiene

Enterobius vermicularis (Life Cycle)

Trichuris trichiura (Life Cycle)

Ascaris lumbricoides (Life Cycle)

When is pinworm infective?

egg stage

When is whipworm infective?

egg stage

When is giant roundworm infective?

egg stage

Ancylostoma duodenale

Hookworm (Old World)

Necator americanus

Hookworm (New World)

Main difference between necator americanus and ancylostoma duodenale

necator has lunar cutting plates

duodenale has fangs/teeth

Hookworm Life Cycle

eggs in soil

hatch as rhabditiform larvae

revert to filariform larvae

attach through skin

migrate to lungs

coughed up and swallowed

mature in small intestine

Hookworm Epidemiology

tropics, subtropics, temperate climates; all ages are susceptible; mixing due to population migration

Ancylostoma duodenale History

spread through silk road (Europe-Asia)

Necator Americanus History

spread through slavery (Africa-Americas/Europe-Asia)

Human Hookworm - Skin Penetration

itching (puritis)

swelling (edema)

“ground itch“

redness (erythema)

papule/vesicle.lesion

Human Hookworm - Larval Migration

“break out“ of blood vessels (circulation)

petechial hemorrhage (lungs)

attachment/reattachment damage (small intestine)

Human Hookworm - Pathology

anemia

iron deficiency

pica

Human Hookworm - Diagnosis

eggs in stool

Human Hookworm - Treatment

albendazole (reinfection likely)

Human Hookworm - Prevention

sanitation/disposal of feces

proper treatment of night soil

personal hygiene

shoes

Ancylostoma canium

Hookworm (Dog)

Ancylostoma braziliense

Hookworm (cat)

Animal Hookworm - Pathology

serpiginous tunnels

inflammation and damage from migration

cutaneous larva migrans

Animal Hookworm - Diagnosis

observation

Animal Hookworm - Treatment

albendazole

mebendazole

ivermectin

thiabendazole

anti-itch and anti-inflammatory creams

resolve in 4-5 weeks without treatment

Animal Hookworm - Prevention

no pets in sandboxes/beach

care when working in animal quarters

plastic cloth when working in crawl spaces under houses

When is hookworm infective?

larval stage

Ancylostoma duodenale and Necator americanus (Life Cycle)

Ancylostoma braziliense and Ancylostoma canium (Life Cycle)

What can hookworm be used for?

to treat allergies; gives immune system something to react to and dampens inflammation response

Trichinella spiralis

Pork Roundworm

Pork Roundworm Life Cycle

consumption of contaminated, undercooked meat

larvae mature in small intestine

attach to mucosa and produce larvae (viviparous)

larvae enter circulation

larvae encyst in muscle

Where do pork roundworm larvae prefer to burrow?

well oxygenated muscle (diaphragm, tongue, eye muscles, intercostal)

Pork Roundworm Epidemiology

maintenance cycles

large gatherings with uninspected meat

undercooked meat

Pork Roundworm Pathology (stage 1)

1-10 days after infection

ingestion of larvae and maturation

necrosis

panmucosal inflammation

vomiting

nausea

diarrhea

fever

Pork Roundworm Pathology (stage 2)

7-14 days after infection

adults are expelled and larvae migrate to muscle

small capillary hemorrhage (fingernails)

bilateral ocular edema (primary sign)

hyper eosinophilia

Pork Roundworm Pathology (stage 3)

3 weeks after infection

larval encystment

muscle inflammation (myositis)

muscle pain (myalgia)

degeneration of muscle fibers

Pork Roundworm Pathology (stage 4)

calcification of larvae

symptomless

Pork Roundworm Diagnosis

history of eating pork, bear, boar

ocular edema (10-14 days post-infection)

muscle biopsy (21 days post-infection)

serology (antibodies)

Pork Roundworm Treatment

early diagnosis → albendazole or mebendazole

supportive care and anti-inflammatory drugs

treatment is often not necessary

Pork Roundworm Prevention

freeze/cook pork

remove rodents from pig farms

cook garbage before feeding to pigs

Which animals are part of T. spirals domestic cycle?

pigs and rats through cannibalism/food scraps

Which animals are part of T. spirals sylvatic cycle?

bears, wild boars, and rats through scavenging/predation