Misc Protozoan Infection

Trichomonas vaginalis - Epidemiology

• protozoan: flagellate

• worldwide distribution:

  • globally estimated 287 million infections

  • prevalence in US is 2.1% among women and 0.5% among men (~3.7 million infected)

• human reservoir

Life Cycle of Trichomonas vaginalis

• infection occurs by transmission of the trophozoite through sexual intercourse (infective stage)

• trophozoites reside in the female lower genital tract and the male urethra and prostate where they multiply (diagnostic stage)

• do not survive well in external environment

• incubation period is 5 to 28 days

Trichomonas vaginalis - In men

• no symptoms in 70 to 80% of men

• temporary irritation inside the penis, mild discharge, or slight burning after urination or ejaculation

Trichomonas vaginalis - In women

• no symptoms in ~50% of women

• frothy, yellow-green vaginal discharge with a strong odor

• discomfort during intercourse and urination, as well as irritation and itching of the female genital area

Trichomonas vaginalis - Clinical Syndromes

• pregnant women who have trichomoniasis may:

  • deliver prematurely

  • have a baby with a low birth weight

  • transmit the infection to the baby as it passes through the birth canal

• easier to become infected with HIV

  • inflammation facilitate HIV transmission as it increases the number of HIV-receptive cells in the genital tract

• more difficult to clear Human papillomavirus

Trichomonoas vaginalis - Diagnosis

• wet mount examination of vaginal or urethral discharge for motile trophs

• clinical presentation of “strawberry cervix” (hemorrphages)

• rapid antigen detection

• molecular detection

Trichomonas vaginalis - Treatment and Prevention

• metronidazole

  • treat all sexual partners

• education, better personal hygiene, safe sexual practices

Free-living Ameba

• worldwide distribution

  • found in soil and in contaminated lakes, streams, and other water environments throughout the world

    • recently found in tap water (colonize biofilms?)

    • acanthamoeba can be spread via dust

• no major reservoir

  • typically acquired during summer months while swimming in contaminated water

Acanthamoeba - Clinical syndromes

• chronic granulomatus amebic encephalitis

  • mental status change, double vision

• keratitis

  • eye pain, eye redness, blurred vision, sensitivity to light

• skin lesions (in immunocompromised individuals)

Acanthamoeba - Diagnosis

• identification of trophozoites/cysts in stained smears biopsy specimens or in corneal scraping

• molecular analysis

Life Cycle of Acanthameoba

• infection occurs when cyst or trophozoites enters the body (through eye, nasal passage or broken skin) (infective stage)

• when enters the respiratory system or eye, can invade the central nervous system by hematogenous dissemination

• cyst and trophs in the tissue is diagnostic stage

Naegleria fowleri - Epidemiology

• in the 10 years from 2013 to 2022, 29 infections were reported in the U.S.

  • most were infected by contaminated recreational water, others by performing nasal irrigation using contaminated tap water, or infected by contaminated tap water used on a backyard slip-n-slide

• only 4 survivors (out 157) in US (through 2022) (fatality rate of >97%)

Naegleria fowleri - Clinical syndromes

• primary amebic meningoencephalitis

  • headache, fever, stiff neck

  • symptoms start 1 to 12 days (median 5 days) after symptoms begin (median 5 days)

Naegleria fowleri - Diagnosis

• microscopic examination of CSF for trophozoites

• molecular analysis

Life Cycle of N. fowleri

• infection occurs when trophozoites enters the body through nasal passage (infective)

• trophs migrate to the brain via olfactory nerves

• trophs in cerebrospinal fluid or the tissue is diagnostic stage

• exposure may also occur through nasal irrigation

Free-Living Ameba - Treatment and Prevention

• miltefosine

  • if Naegleria - additional drugs

• education

  • avoid waters where presence of microbe is known

  • avoid high risk activities such as: diving or jumping into water, submerging the head under water or engaging in other water-related activities that cause water to go up the nose

  • do not use tap water to irrigate sinuses

Toxoplasma gondii - Epidemiology

• worldwide distribution:

  • one-third of the general world population is infected with high heterogeneity between countries

  • in the US it is estimated that 22.5% of the population 12 years and older have been infected

    • infects over 1 million persons with an est 4800 individuals each year developing symptomatic eye disease (with vision loss) and an est 400-4000 cases of congenital toxoplasmosis

  • animal reservoir: house cat

Toxoplasma gondii - Transmission

• foodborne: eating contaminated, undercooked meat

• animal to human: accidental ingestion of oocysts (ex. cleaning litter box)

• congenital

• RARE: organ transplants and blood transfusions

Life Cycle of Toxoplasma

• infection occurs when ingestion of oocyst occurs (infective stage)

• parasite circulates in the blood and forms cysts in various tissue, mostly commonly skeletal muscle, myocardium, brain and eyes (diagnostic stage)

• cysts may remain throughout the life of the host

• cats become infected after consuming intermediate host harboring tissue cysts (intermediate hosts can become infected after ingestion of the oocysts in the environment)

Toxoplasma gondii - Clinical Syndrome

• most people are asymptomatic infection (healthy and nonpregnant)

  • 10% to 20% develop flu-like symptoms

• severe symptoms can cause damage to the brain, eyes, or other organs (immunosuppressed)

Congenital toxoplasmosis

• acute primary infection acquired by pregnant woman

• incidence and severity of congenital toxoplasmosis vary with the trimester: (a) infection in 1st trimester - incidence of transplacental infection is low (15%) but disease in neonate is most severe; (b) infection in 3rd trimester - incidence of transplacental infection is high (65%) but infant is usually asymptomatic at birth

• symptoms: chorioretinitis, hypocephalus, and intracranial calcifications

• eye disease occurs in 20-80% of congentially-infected persons by adulthood

Toxoplasma gondii - Diagnosis

• antibody detection

• microscopic staining of blood, fluid, tissue sections

• molecular analysis

Toxoplasma gondii - Treatment and Prevention

• treatment not typically needed for healthy people

• treatment for acutely infected pregnant women/congenitally infected newborns/immunocompromised

• education and handwashing

  • change cat litter box daily (as parasite does not become infectious until 1 to 5 days after shed in feces)/do not change if pregnant

  • do not eat undercooked meat