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Embed code for: Medical Parasitology Lesson 1
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Medical Parasitology Lumen Dwelling Protozoa
Dr. Adekunle Sanyaolu
Relevant medical properties
Lumen Dwelling Protozoa
Worldwide (where environmental sanitation is poor)
Organism may be in parasitic or commensal form.
Around 400 million people worldwide are infected
Only about 10% are symptomatic
Third leading parasitic cause of death after malaria and schistosomiasis.
Severe infection occur in pregnant women, very young children, the malnourished and people on steroids.
Occurs via the faeco-oral route, usually through food and drink becoming contaminated with human feces.
Prevalence is highest in areas where human feces are used as fertilizer.
Sexual transmission also occur
Parasite inhabits the large intestine, where trophozoites, or active forms, live in the intestinal lumen
Occasionally they may invade the mucosal crypts, where they feed on red blood cells and form ulcers.
Ulceration of the intestinal wall may give rise to amoebic dysentery or there may be fairly extensive damage without any clinical signs of disease.
Invading amoebae at times find their way into capillaries to be transported via the blood stream to the liver or other organs where abscess formation may occur.
Amoebiasis Pathogenesis & Clinical manifestation
Amoeba that remain in or re-enter the lumen of the gut may, if intestinal motility is rapid be passed out in liquid or semi-formed stools as trophozoites.
But if motility is normal, they will round up, extrude any ingested food and enter the resistant cyst stage
Amoebic liver abscess
Amoebiasis (Amoebic dysentry)
Diarrhea is not usually of sudden onset
Incubation period is not less than 7 days and commonly weeks or months.
Diarrheal stool often contain macroscopic blood and mucus
Frequency is seldom more than 12 per days
It is unusual for patient to have severe abdominal pain or tenesmus but low abdominal cramp often precede defecation.
Usually no significant fever or malaise.
No prodromal features
Patient usually ambulant
Diarrhoea fecal, bloody
Stool fishy odour
May be epidemic
Prolonged fever and malaise common
Diarrhoea watery, bloody
few bacilli , pus cells, macrophage, red cells.
very common, sometimes severe
spontaneous recovery in a few days to a week or more, no relapses
numerous bacilli, red cells, amoebic trophozoites with ingested red cell
bout last several weeks, dysentery recurs after a variable interval of remission, infection persist for several years.
Amoebiasis (Amoebic dysentry) Natural course of untreated amoebic dysentery
In the absence of treatment, the usual course is for the diarrhea to become gradually worse over a period of a few days, persist for a few week and then gradually diminish in intensity so that the whole bout is over in about 6 weeks.
Attack may recur at irregular intervals for years, in the intervening intervals the infection persisting in commensal form.
Sometimes there are no attack of dysentery after the first, but the persistence of the infection manifest itself years later as a complication.
Some patients have persistent bloody diarrhea of unremitting intensity which last for years.
Even if untreated, most of those infected probably eliminate the infection in 3-5days, unless they are reinfected in the meantime.
Amoebiasis (Amoebic dysentry) Invasive versus non-invasive disease
If a patient is excreting E. histolytica cysts or trophozoites, he has amoebiasis
If he has relevant bowel symptoms, he obviously has invasive disease
On the other hand, if he has no symptoms, he may either have non-invasive disease or subclinical invasive disease
The last situation arise when the patient has ulcers so few or so small they cause no symptoms; but the tissues are nevertheless being invaded by the amoebae.
Amoebiasis (Amoebic dysentry) Local complication
Occasionally, severe bleeding may occur when a large blood vessel is eroded
Perforation may lead to peritonitis.
Both events are rare.
So also is fulminating amoebiasis, in which the amoebae are so destructive that the colon is destroyed and the patient presents with severe abdominal pain and ileus.
Amoebiasis Amoebic Ulcer & Amoeboma
Ulceration in or near the rectum may cause tenesmus and over secretion of mucus.
The condition may be persistent.
Chronic inflammatory mass developing around a part of the bowel, caused by E. histolytica.
Mass often develops as a diffuse thickening of the bowel wall, closely resembling a carcinoma.
Symptoms includes abdominal pain, constipation and sometimes fever.
Amoebic Ulcer of colon and genitalia
Amoebiasis (Amoebic liver abscess)
It is caused by amoebae entering the liver via the portal vein, and probably usually develops from the coalescence of several small abscesses.
Most abscesses develop in the right lobe.
An area of liver cell destruction occupies the centre, containing an amorphous, cream, pink or pinkish-brown viscous fluid called “amoebic pus”
Pus which is at first pale on aspiration, often darkens on exposure to air
Surrounding the pus, there is an area of compressed but otherwise normal liver tissue in which the amoebae , as trophozoites are feasting on the liver cell and actively dividing.
Beyond this zone, the liver is normal, and no inflammatory cells or capsule contain the abscess.
Abscess contains product of colliquative necrosis of the liver cells
not degenerative pus cells like other abscess.
If not interfered with, the abscess will normally grow until it reaches a surface through which it can discharge
E.g. the skin, the peritoneum, the pleural cavity or the pericardium.
Stretching of the liver capsule produced by the abscess is presumably the main source of pain
The absorption of necrotic tissue causes the characteristic constitutional disturbances.
Pain over the liver
sometimes referred to the right shoulder
Tenderness over the liver
Cough if there is associated lung involvement
Breathlessness in chronic cases with marked anemia.
Enlargement of the liver
tenseness of the skin when the abscess approaches the surface.
Signs at the right lung base dullness to percussion and reduced breath sounds, perhaps with crackles
RUPTURE LEADING TO:
Formation of a cutaneous sinus
Hepatobronchial fistula (and secondary pulmonary lesions) or death from inhalation of abscess content
Perhaps with constrictive pericarditis
Metastasis with secondary lesion in lung or brain
marked jaundice is rare
Anaemia may be severe if the abscess is very chronic
Amoebiasis (Cutaneous amoebiasis)
Common when an amoebic liver abscess drains through the skin, as a result of spontaneous rupture or surgical drainage, if no specific anti-amoebic treatment is given.
Gruesomely destructive amoebic infections of the penis may result from anal intercourse with a partner with amoebiasis, and comparable lesions may affect the vulva.
Amoebiasis (Cutaneous amoebiasis)
Made by microscopic demonstration of trophozoites or cyst in fresh or suitably preserved fecal specimens, smears of aspirate or scrapings obtained by protoscopy, aspirate of abscesses or sections of tissue
The presence of trophozoites containing Red Blood Cell (RBC) is indicative of invasive amebiasis
Organism must be differentiated from nonpathogenic amoebae and macrophage.
Antigen capture and PCR tests can distinguish E. dispar (non-pathogenic) from E. histolytica (pathogenic) in heavier infections.
Culture on special media are not routinely used
Many serological test are available as adjunct in diagnosing extra-intestinal amoebiasis such as liver abscess where stool examination is often negative.
Scintillography, ultrasonography and CAT scanning in addition to conventioal x-ray techniques, are helpful in revealing the presence and location of an amebic liver abscess, and can be considered diagnostic when associated with a high titer of specific antibodies
Iodoquinol (Diodoquin®) if cyst passage persist.
Metronidazole or a combination of dehydroemetine plus chloroquine (Aralen®)
Surgical aspiration may be required for abscess
Iodoquinol or diloxanide furoate (Furamide®)
Amoebic liver abscess (ALA)
Amoebiasis (Prevention and Control)
Educate the general public in personal hygiene, particularly in sanitary disposal of feces and in hand washing after defecation and before preparing or eating food
Teach known carriers the need for thorough hand washing after defecation, treat if symptoms develop.
Educate high risk groups to avoid sexual practices that may permit fecal-oral transmission
Dispose of human feces in a sanitary manner
Protect public water supplies from fecal contamination
Exclude infected individuals from food handling and direct care of patients
Thorough washing of fruits and vegetables with potable water and keeping them dry.
Cyst are killed by desiccation and temperature above 50ºC (122ºF)
Health agencies should supervise the sanitary practices of person preparing and serving food in public eating places as well as general cleanliness of the premises involved.
Children infected more frequently than adults.
High prevalence in area of poor sanitation.
Person to person transmission occurs by hand-to-mouth transfer of cyst from the feces of an infected individual especially in institutions and day-care centers, this is the principal mode of spread.
Asymptomatic infected individuals (being very common) are probably more responsible for transmission than those with diarrhea.
Localized outbreaks may occur from ingestion of cyst in fecally contaminated water and less often from fecally contaminated food.
Chlorine concentrations used in routine water treatment do not kill cysts especially when the water is cold.
Unfiltered stream and lake waters that are open to contamination by human and animal feces are a frequent source of infection.
Prevalence of stool positivity in different area may range between 1 and 30%, depending on the community and age group surveyed.
Prevalent in certain temperate as well as tropical countries, with frequent infection of tour groups related epidemiologically to drinking inadequately treated water.
Man, possibly beaver and other wild and domestic animals
Cyst from human sources are more infectious to man than those from animal sources.
Giardiasis (Pathogenesis & Clinical manifestation)
Incubation period is 5 to 25 days or longer; Median 7-10 days.
Symptoms of acute disease usually begin within 3-20 days of infection; most patient recover within 2-4 weeks.
25% of travelers symptoms persist for up to 7 weeks.
Diarrhea is the major symptom
Watery initially becoming steatorrhoeic.
Often associated with nausea, abdominal discomfort, bloating, weight loss, and sometimes sulfurous, offensive burps.
Frequent loose and pale greasy stools.
Some patient develop chronic diarrhea associated with weight loss of up to 20% of ideal body weight, fat malabsorption, Vitamin A and B12 deficiency and in some cases 2º hypolactasia.
Usually no extra-intestinal invasion.
Occasionally, trophozoites may migrate into the bile or pancreatic ducts producing inflammatory processes
Damage to duodenal and jejunal mucosal cells may occur in severe cases.
Retardation of growth and development in severely affected infants and children in whom malabsorbtion excercebates malnutrition.
Chronic giardiasis is associated with allergic and inflammatory conditions such as lymphoid nodular hyperplasia, protein-losing enteropathy, lactose intolerance and irritable bowel syndrome.
Identification of cysts or trophozoites in feces
Repeated at least 3 times before considered negative.
Identification of trophozoites
in duodenal fluids
by aspiration or string test
in mucosa obtained by small intestinal biopsy.
Immunodiagnostic test are available
Elisa Antigen test.
Note that since mixed enteric infections and asymptomatic carriage of Giardia is so common, identification of the parasite does not guarantee that it is the causative agent of the diarrhea
Tinidazole (Tindamax ®)
first-line drug of choice used for the treatment of infectious diarrhea caused by Cryptosporidium parvum or Giardia lamblia in immuno-competent adults and children 1 year of age and older
Rehydration and symptomatic relief are usually sufficient.
If symptoms persist, an anti-giardial drug will decrease the severity and duration of symptoms
Giardiasis (Prevention & Control)
Educate families, personnel, and inmates of institutions and especially adult personnel of day-care centers, on personal hygiene and the need for hand washing before eating and after toilet use.
Filter public water supplies that are at risk of human or animal fecal contamination.
Protect public water supplies against contamination with human and animal feces.
Dispose of feces in a sanitary manner.
In humans, the main causes of disease are
C. hominis (previously C. parvum genotype 1).
Other species that can cause disease in humans are:
C. canis, C. felis, C. meleagridis, and C. muris.
Fecal-Oral, with person to person.
Animal to person
One or more auto infectious cycles may occur in man.
The parasite is transmitted by environmentally hardy cysts (oocysts) that, once ingested, excyst in the small intestine and result in an infection of intestinal epithelial tissue.
Oocyst containing sporozoites are the infective stage.
Man, Cattle, and other domestic animals are Reservoir
In developed countries, prevalence ranged from <1% to 4.5%.
In developing countries prevalence is significantly higher ranging from 3 to 20%.
Children over 2 years of age, animal handlers, travelers, homosexual men and close personal contacts of infected individuals (families, health and day-care workers) are likely exposed to the infection.
Several suspected waterborne outbreaks have been reported worldwide.
Cryptosporidiosis (Life Cycle)
Upon ingestion, sporozoites are released from oocyst and infects intestinal epithelial cells, multiplying initially by schizogony (X2), followed by a sexual cycle (Gametogony).
Sporulated oocysts, containing four sporozoites each are pass out in the feces where they survive under adverse environmental conditions for long period of time
Cryptosporidiosis (Pathogenesis & clinical manifestation)
Disease is typically an acute, short-term infection, but can become severe and non-resolving in children and immuno-compromised individuals.
Major symptom in human patient is diarrhea which may be profuse and watery.
Diarrhea is preceded by anorexia and vomiting in children.
Diarrhea is associated with cramping, abdominal pain, general malaise, fever, anorexia, nausea, and less often vomiting.
In most immunologically healthy person, symptoms usually wax and wane but remit in fewer than 30days.
In immunodeficient person, especially AIDS patients, they may be unable to clear the parasite and the disease has a prolonged and fulminant clinical course, contributing to death
Cryptosporidiosis Pathogenesis & clinical manifestation Diagnosis
Oocyst in fecal smear
Most commonly used stains includes auramine-rhodamine, modified ZN (acid-fast) stain, and safranin-methylene blue.
Small intestinal biopsy
Cryptosporidium antigen detection in stool
Fluorescein-tagged monoclonal antibody
PCR for species identification.
Symptoms of cholecystitis may occur in bilary tract infections.
Infection may mimic Cholera in AIDS patients.
In humans, it remains in the lower intestine and may remain for up to five weeks.
Acid Fast Staining
Nitazoxanide (FDA Approved)
Most people who have healthy immune systems will recover without treatment.
Diarrhea can be managed by drinking plenty of fluids to prevent dehydration
Rapid loss of fluids from diarrhea may be especially life threatening to babies.
For AIDS patients, anti-retroviral therapy that improves the immune status will also decrease or eliminate symptoms of cryptosporidiosis
Cryptosporidiosis (Prevention& Control)
Educate the public on personal hygiene.
Avoid contaminated water or food.
Practice extra caution while travelling.
Prevent contact and contamination during sex.
Dispose of feces in sanitary manner.
Handle animal excreta with care.
Careful hand wash by those in contact with calves and other animals with diarrhea.
Filter or boil drinking water supplies; chemical disinfectant are not effective against oocysts.
Common cause of vaginitis
A sexually transmitted disease
Most common pathogenic protozoan infection of humans in industrialized countries
Approximately 174 million people worldwide are infected with this parasite each year, making it the most common curable sexually transmitted infection worldwide
Infection usually occurs in women during reproductive years, and occurrence before menarche or after menopause is rare.
Fourteen to 60% of male infections are associated with known infected female partners.
Humans is the only host of parasite
Commonly spread through sexual contact with vaginal or urethral discharges of infected persons.
Transmission of organisms via artificial insemination of infected cryobanked semen is also possible.
Non-sexual transmission is rare but has been observed in cases involving contaminated douche nozzles, moist wash-clothes, specula, or toilet seats.
Transmission to newborn infants from infected mothers is possible and is observed in 2 - 17% of cases, and can result in urinary tract or vaginal infections.
Trichomoniasis (Symptoms) Women & Men
Burning after urination or ejaculation
Itching of urethra
Slight discharge from urethra
Occasionally, some men with trichomoniasis may develop prostatitis or epididymitis from the infection.
Discomfort with intercourse /urination
Itching of the inner thighs
Vaginal discharge (thin, greenish-yellow, frothy or foamy)
Vaginal itching / burning
Vulvar itching or swelling of the labia
Vaginal odor (foul or strong smell)
Redness or soreness of genitals
Acute infections are characterised by severe pruritus, vaginitis, vulvitis with dysuria and dyspareunia, and hemorrhagic spots on the mucosa (in 2% of patients) which results in colpitis macularis or petechiae (strawberry cervix)
Trichomoniasis (Complications in Women)
Infection is also associated with increased chances of cervical cancer.
Infection increase the risk of getting or spreading other STI
Infection cause genital inflammation that makes it easier to get infected with the HIV virus, or to pass the HIV virus on to a sex partner.
Infection may cause a woman to deliver a low-birth-weight or premature infant.
Trichomoniasis (Complications in Men)
Scanty, clear to mucopurulent discharge
Infection in males potentially raises the risks of prostate cancer development and spread due to inflammation
Genitourinary inflammation disease
shows red blotches on the vaginal wall or cervix.
Wet prep (microscopic examination of discharge)
shows the infection-causing organisms in vaginal fluids.
A pap smear may also diagnose the condition
The disease can be hard to diagnose in men.
In women, the examiner collects the specimen during a pelvic examination by inserting a speculum into the vagina and then using a cotton-tipped applicator to collect the sample
The sample is then placed onto a microscopic slide and sent to a laboratory to be analyzed.
Trichomoniasis is diagnosed by visually observing the trichomonads via a microscope
Trichomoniasis Treatment & Prevention
Using condoms correctly during sex.
Limiting number of sex partners, and not going back and forth between partners.
Practicing sexual abstinence, or limiting sexual contact to one uninfected partner.
Avoid sexual contact if infected and seeking treatment.
Men are treated if the infection is diagnosed in any of their sexual partners.
Men may also be treated if they have ongoing symptoms of urethral burning or itching despite treatment for gonorrhea and chlamydia.e