7 Flashcards
What is a parasitism
Intimate and obligatory and symbiotic relationship between two organisms of different species
In what way is the parasite dependent on a host
Metabolically and physiologically
Example of a short term and a permanent parasite
Mosquito and tapeworm
How common is parasite
50%
What are true parasite
Protozoans (single celled )
Success of parasite dined in terms of:
Prevalence in host
Number of host species available
Geographic range
Number of offspring
Available routes of transmission
What is giardia lamblia history
Documented as first true pathogen in 1900
Leeuwenhoek 1681
Most frequently identified intestinal parasite worldwide
Symptoms of g. Lamblia
Asymptomatic (carriers)
Acute guardian: diarrhea, WL, abdominal discomfort, nausea, vomiting
Retardation of growth and development in young children (failure to thrive)
What is the prevalence of giardia lamblia
Most common infection of intestinal tract
-2-5 in industrialized world 20-30% in developing world
-prevelnace rises in infancy and childhood and declines in adolescence
-travellers and immunocporised
-water/outdoor activities
Life cycle of gardia lamblia
Excystation
Trophozoites in small intestines
Longitudinal binary fission
Encystation
Cysts shed with faeces
how is g.lamblia diagnosed
MICROSCOPY (stool exam)
* cysts concentrated by flotation and
identified using bright-field
microscopy
immunofluorecence microscopy
using fluorochrome-conjugated
mAb’s that bind to cyst wall
Immunological Testing
* detection of Giardia-specific antigens in
faeces (eg. ELISA)
treatment of Glamblia
Nitroimidazole derivatives
- metronidazole and tinidazole are the
drugs of choice; 2 g (single dose) daily
for 3 days
how to control g.lamblia out break with water treatemtn
Nitroimidazole derivatives
- metronidazole and tinidazole are the
drugs of choice; 2 g (single dose) daily
for 3 days
PUBLIC HEALTH EDUCATION of g.lamnlia
increase awareness of person-to-person transmission;
improve hygienic practices (e.g., daycares)
* food-borne infections (food handlers, wash produce)
* backpackers drinking raw surface water are at risk
(portable filters, boil water)
* Advice to travelers (avoid tap water, peeled fruits)
Trichomonas vaginalis
most common sexually transmitted disease worldwide (200 million cases)
Transmitted through mucous membrane contact
(no resistant cyst stage)
Trichomonas vaginalis - Symptoms
40-50% asymptomatic carriage
* Vaginitis (trichomoniasis) with itching, foul-smelling,
sometimes frothy discharge
* May increase susceptibility to cervical cancer and HIV infection
* Infection during pregnancy may result in premature delivery and
low birth weight
* Males usually asymptomatic; occasionally urethritis, prostatitis
Trichomonas vaginalis - Diagnosis
Microscopy (wet mounts) to identify trichomonads in vaginal or urethral discharge
Vary greatly in size
(10-30µm)
Trichomonas vaginalis - Treatment
metronidazole and tinidazole are drugs of
choice
* To avoid re-infection, testing and treatment
of partners is important
Toxoplasma gondii
Recognized as a human pathogen in early 1900’s
* Very high seroprevalence in humans worldwide
* Large number of mammals and birds act as
intermediate hosts
* cats are the only definitive hosts (shed oocysts)
Toxoplasma gondii- Transmission
- Ingestion of sporulated oocysts (10-12 µm)
- contaminated soil/sand
- contaminated fruits and vegetables
- waterborne outbreaks (Victoria, B.C., 1995) - Ingestion of tissue cysts
- raw or poorly cooked meat - Congenital infection of fetus
- infection acquired during pregnancy (most severe if
acquired in first trimester)
Symptoms of toxoplasmosis
- Immunocompetent host
90% asymptomatic, lymphadenopathy, headaches,
muscle aches, fever, malaise - Immunocompromised host
encephalitis, myocarditis, pneumonia
(AIDS-defining disease) - Congenital infection
hepatosplenomegaly, mental retardation,
retinochoroiditis, hydrocephalus
Treatment of toxoplasmosis
Diagnosis based on serological assays
* Immunocompetent patients normally don’t require
treatment unless symptoms become severe or
chronic
* Immunocompromised patients require prompt
treatment with a combination of pyrimethamine and
sulfadiazine
* Congenital infections:
– Mother/fetus can be treated to reduce incidence and
severity of fetal infection
– Infected newborns can also be treated to minimize
sequelae
Malaria -Transmission
Anopheline mosquitoes (vectors)
* Blood transfusion / shared needles
* Congenital infection
* “Airport malaria
Symptoms of Malari
- Spiking fever and chills
- Flu-like symptoms (myalgias, headaches,
abdominal pain, malaise) - Severe symptoms (P. falciparum)
seizures, coma, renal failure, respiratory
failure
Malaria prophylaxis and treatment
- Chloroquine and mefloquine are drugs of
choice for prevention and treatment - drug resistance is a serious problem
Control of Malaria
Largely a man-made disease (clearing of
forests, building of irrigation canals)
* Eradication or control of mosquitoes
(resistance to insecticides)
* Protection against mosquito bites
– Avoid rural areas at night
– Long-sleeved shirts/long pants
– Insect repellent
– Bed netting
Cryptosporidium spp
recognized as human pathogen (1976)
* reported in humans worldwide
* The most common symptom of cryptosporidiosis is
watery diarrhea; other symptoms include dehydration,
weight loss, abdominal pain, fever, nausea, vomiting
* chronic, debilitating, and potentially life-threatening
symptoms in immunocompromised
Life cycle – Cryptosporidium
complex life cycle including both sexual and asexual phases (oocysts 4-6 µ)
obligate intracellular protozoan which infects the intestinal epithelial cells of the host (typically in small intestine)
Transmission - Cryptosporidium
WATER
* numerically the most important mode of
transmission (contaminated drinking water)
* recently numerous outbreaks associated with
water parks/pools
Transmission - C. parvum
PERSON-TO-PERSON
* ingestion of oocysts due to poor hygiene
(e.g., day cares, institutionalized patients)
AUTOINFECTION
* thin-walled oocysts are released into the lumen
and cause autoinfection
* responsible for chronic and life-threatening
disease in immunocompromised
ZOONOTIC
* cattle serve as important
reservoir hosts
* calves with diarrhea can excrete up to 1010
oocysts/day
* environmental contamination; veterinary
personnel and animal handlers at increased risk
(petting zoo visitors)
Diagnosis - C. parvum
MICROSCOPY
* oocyst shedding intermittent;
multiple stools examined
* concentration methods can be used
when low oocyst shedding
* wet-mounts or permanent stains are
used (acid-fast)
* Fluorescein-labelled IgG mAb is
used in immunofluorescence
microscopy
Control - C. parvum
PUBLIC HEALTH EDUCATION
* in endemic areas, avoid drinking tap water/ice cubes,
raw fruits and vegetables unless you can peel them
* immunocompromised patients should consider
bottled water
* exposure to temperatures above 60°C and below
-20°C will kill oocysts
because crypto is spread person-to-person,
handwashing helps prevent infection
- precautions are required when caring for
patients with crypto diarrhea; lack of
effective disinfectants against oocysts
(nosocomial infections)
Cyclospora cayetanensis
Identified as a coccidian protozoan parasite and
named in 1993
* Cases reported in North, Central, South America,
Caribbean, S.E. Asia, Europe, UK, India, Africa
* Endemic countries include Nepal, Haiti, Peru,
and Guatemala
Cyclosporiasis - Symptoms
Low infectious dose
* Incubation period approximately 1 week
* Profuse and prolonged diarrhea
* Abdominal pain, nausea, vomiting, fatigue,
fever, loss of appetite
* Effectively treated with bactrim
(trimethoprim-sulfamethoxazole)
Cyclosporiasis - Diagnosis
microscopic examination of wet mount
stool for oocysts (brightfield, differential
interference contrast, autofluorescence)
* staining methods (e.g. acid-fast)
Cyclosporiasis - Transmission
Person-to-person transmission unlikely
* Zoonotic transmission unlikely
* Most earlier outbreaks were waterborne
* 90-99% of cases in U.S. are foodborne
* Numerous foodborne outbreaks in recent years
Enterobius vermicularis
Prevalent world wide
* Highest incidence in school-age children
* Up to 50% of children in North America
* More of a nuisance than a health problem
* Eggs ingested (faecal-oral route)
Pinworm - Symptoms
Mild infection of caecum/colon
* May cause itching (pruritus ani) leading to
disturbed sleep, irritability
* Scratching may cause secondary infections
Pinworm – Diagnosis/Treatment
Scotch-tape test of perianal area
* Microscopic identification of
eggs; adult female worms may
also be present (8-13mm)
* Drug of choice is pyrantel pamoate
Pinworm - Control
Personal hygiene education for children
(wash hands)
* Discourage scratching, nail biting
* Frequent bathing; regular change of
underclothing, pajamas, and bedding
Trichinella spp.
Small roundworm found worldwide in many
carnivorous and omnivorous animals, including
humans
* Transmitted through ingestion of larvae in raw or
poorly cooked meat
* Survives as adult in small intestine; as larvae
encysted in striated muscle
Trichinella spiralis vs Trichinella nativa
Trichinella spiralis (domestic form)
- humans, swine, rats (responsible for endemicity)
- horses! (probably fed animal products as supplement)
Trichinella nativa (sylvatic or wild form)
- humans, bears, wild boar, wolf, fox, walrus, etc
Trichinellosis - Symptoms
Symptoms dependent upon phase of life cycle
* When larvae excyst in small intestine - diarrhea,
abdominal pain, vomiting
* When next generation of larvae migrate into muscle tissues
- facial edema, conjunctivitis, fever, myalgias
* Occasional life-threatening manifestations include
myocarditis, central nervous system involvement, and
pneumonitis
Trichinellosis - Treatment
Thiabendazole effective against intestinal phase
* Mebendazole and albendazole have some effect
on tissue phases
* Steroids may be used to reduce inflammation
Trichinellosis - Control
Rodent control
* Avoid garbage feeding to livestock
* Inspection programs (trichinoscopy, digestion, ELISA)
* Cooking /freezing (T. nativa very resistent to freezing
Diphyllobothrium spp.
(Broad fish tapeworm
large tapeworm (10 m long)
* Adult tapeworm inhabits the small intestine
of humans and other fish-eating mammals
* Larval stages in freshwater fishes (e.g. pike,
trout, perch, whitefish, salmon) which act as
intermediate hosts
Diphyllobothrium spp.
Transmitted through the consumption of raw or
poorly cooked freshwater fish containing
infective larvae
Diphyllobothrium spp. - Symptoms
- Most cases are asymptomatic
- Abdominal pain, dizziness, fatigue, vomiting,
diarrhea/constipation - Vitamin B12 deficiency with
pernicious anemia
Diphyllobothrium spp. – Diagnosis
and Treatment
- Stool examination for eggs (microscopy) or
proglottids (segments)
Anthelmintic drugs effective (Praziquantel)
Taenia spp
Large tapeworms (up to 20 m in length)
* Adult stage only found in humans
* Transmitted through ingestion of larvae in
raw or poorly cooked meat
Taenia spp. (symptom diagnosos trestment)
Symptoms (adult tapeworm)
-mild abdominal complaints
Diagnosis
-Eggs or proglottids in stool
-Serological techniques
Treatment
-Anthelmintic drugs (Praziquantel)
-surgery
