Fungal and Protozoan Diseases

Ringworm (Tinea Infections)

-              Fungal infections, transmitted primarily through direct contact or indirect contact with contaminated surfaces.

o   Tinea corporis (ringworm of the body)

o   Tinea cruris (jock itch)

o   Tinea capitis (ringworm of the scalp)

o   Tinea unguium (fungal nail infection)

-              All treated with antifungal drugs but may take weeks or months. With Tinea pedis (athlete's foot), possibility of a secondary bacterial infection.

Candida albicans

-              Part of the normal flora of the mouth, GI tract, and vagina.

-              Can cause oral thrush, cutaneous and vulvovaginal candidiasis, and nosocomial fungal infections.

-              Systemic infection can occur in immunocompromised (AIDS patients).

Candida auris

-              Emerging fungus that is highly resistant to multiple antifungal drugs classes.

-              Can cause outbreaks in healthcare settings; serious infection in hospitalized or immunocompromised patients that often enters the bloodstream and spreads throughout the body.

-              Special lab methods are required for accurate identification.

Crytococcosis

-              Caused by encapsulated yeast called Cryptococcus neoformans, C. gattii and C. grubii.

-              Primary route of infection: breathing in airborne spores and desiccated yeast cells (soil contaminated with bird droppings) leading to lung infection.

-              Most people don’t get sick, but in immunocompromised patients, fungus can spread from blood to CNS causing Cryptococcal meningitis.

African Trypanosomiasis

-              Caused by flagellated protozoan in genus Trypanosoma (T. brucei rhodesiense or T. brucei gambiense), transmitted by the bite of an infected tsetse fly.

-              Organism spreads through blood, lymph and can infect all organs. If not treated, can deteriorate CNS, lead to coma, then death.

-              Vaccine development has been challenging because of antigenic variation of surface glycoproteins.

Visceral Leishmaniasis

-              Caused by Leishmania, primarily Leishmania donovani.

-              Transmitted via sand fly bite in tropical and subtropical regions.

-              Parasites taken up by macrophages then multiply and circulate throughout the body, causing systemic infection.

-              Causes fever, anemia, swelling abdomen due to enlargement of spleen & liver. If not treated, death will result.

-              Opportunistic infection in HIV patients. Other Leishmania species cause cutaneous leishmaniasis (skin sores that leave scars).

Malaria

-              In tropical areas caused by Plasmodium protozoans, transmitted by bite of an infected Anopheles mosquito.

o   Infected female mosquito carries the "sporozoite stage" which enters the human blood stream.

o   Travels to the liver and changes into the "merozoite stage".

o   The merozoites rupture liver cells and invade the RBC where they multiply in the "trophozoite stage".

o   The RBC ruptures periodically to release new merozoites, with a simultaneous rise in body temp, fever, chills.

-              Individuals with sickle cell trait possess some resistance to severe malaria.

Of the five species of Plasmodium, Plasmodium falciparum causes the most severe disease due to its ability to obstruct blood vessels. Treatment of P. falciparum malaria involves artemisinin-based combination therapies (ACTs), due to widespread chloroquine resistance. Vaccine development is hard due to antigenic variation. Mosquirix vaccine offers limited protection for children. Chemoprophylaxis and vector control measures should be taken if going to endemic areas. Future vector control strategies include genetically modified mosquitoes to reduce transmission.

Chagas disease (American Trypanosomiasis)

-              Caused by protozoan Trypanosoma cruzi

-              Primarily found in Latin America, with sporadic cases in southern USA.

-              Transmitted by the reduviid bug (kissing bug), through contaminated feces entering the bite site or mucous membranes.

-              The organism initially causes fever, swollen glands and sometimes swelling at the bite site.

o   Some people go on to a chronic form of the disease. Nerves in various organs like the heart, skeletal muscles and colon can be damaged.

o   If a pregnant woman is chronically infected, she can pass it on to fetus. Difficult to treat at chronic stage since parasite can multiply inside host cells.

Toxoplasmosis

-              Caused by protozoan Toxoplasma gondii.

-              Infection by ingesting oocysts from cat feces or tissue cysts in undercooked meat.

-              In the body, oocysts mature into rapidly multiplying tachyzoites in host cells causing acute infection. Most healthy individuals are asymptomatic or have mild lymphadenopathy. The parasite remains dormant in tissue cysts for life, usually without causing illness.

-              If first infection occurs during pregnancy, it will cause miscarriage or congenital defects as the parasite can cross the placenta.

-              Immunocompromised patients experience reactivation of tissue cysts and are at risk for Toxoplasmic Encephalitis. Research about potential link between T. gondii infection and schizophrenia is ongoing.

Coccidioidomycosis (aka Valley Fever or San Joaquin fever)

-              Commonly caused by Coccidioides immitis and C. posadasii, dimorphic fungi in arid regions in Southwestern U.S.

-              Soil spores inhaled usually results in mild flu-like symptoms or no symptoms at all.

-              In tissues the organism forms a spherule filled with spores, often used in diagnosis.

-              Immunocompromised individuals are at risk for disseminated disease, which can involve the meninges, bones, or other organs.

Histoplasmosis

-              Caused by Histoplasma capsulatum, a dimorphic fungus endemic in central and eastern U.S.

-              Soil fungal spores are inhaled and mature into an actively growing yeastlike form which can survive and replicate in macrophages.

-              Usually remains mild and localized within the lungs in most, but can disseminate to the spleen, liver, lymph nodes, and other organs, potentially causing severe disease in immunocompromised patients.

Pneumocystis pneumonia (PCP)

-              Caused by the opportunistic fungus Pneumocystis jirovecii.

-              Affects lungs by attaching to alveolar cells, causing inflammation in immunocompromised individuals, organ transplants, or cancer.

-              Healthy individuals are typically asymptomatic carriers.

-              Untreated PCP has high fatality rate. Treated with specific antimicrobial agents (e.g., trimethoprim-sulfamethoxazole [TMP-SMX]), traditional antifungal drugs are ineffective.

Blastomycosis

-              Caused by Blastomyces dermatitidis, a dimorphic fungus thrive in moist soil rich in organic matter.

-              Primarily entered by breathing spores into the lungs, but can very rarely occur through direct entry into wound. Spores mature to yeast cells in lungs leading to pneumonia.

-              Yeast cells can also spread through the circulation and then disseminate to other organs such as skin, bone, and the genitourinary tract. Systemic blastomycosis can lead to extensive tissue damage.

-              Not considered an opportunistic infection.

Aspergillosis

-              Opportunistic fungal disease primarily caused by Aspergillus fumigatus and other Aspergillus species.

-              Spores often found in compost piles and decaying vegetation. When inhaled can trigger allergic reactions in individuals with pre-existing respiratory conditions like asthma or cystic fibrosis.

-              Invasive aspergillosis occurs when inhaled spores infect the lungs, primarily in immunocompromised individuals such as those with AIDS, leukemia, or organ transplants.

Pulmonary cryptococcosis

-              Infection occurs in lungs when a person breathes in the microscopic fungal spores (Cryptococcus neoformans or C. gattii) from the environment (soil, bird droppings, tree debris), which manifests as a form of pneumonia.

-              In people with healthy immune systems, lung infection often mild or asymptomatic and may resolve on its own.

-              In people with weakened immune systems or when the initial lung infection is not contained, the fungus can disseminate via the bloodstream and then leads to nervous system infection causing meningitis

Giardiasis

-              Caused by Giardia duodenalis (also known as G. intestinalis or G. lamblia).

-              Infection occurs when cysts of the organisms are ingested via contaminated water, food, or hands.

-              In the small intestine, cysts transform into trophozoite and adhere to the bowel wall. Causes severe diarrhea (foul and greasy) and can interrupt normal adsorption.

-              Cysts are resistant to standard chlorination, so prevention relies on boiling, filtration, and good hygiene.

Cryptosporidiosis

-              Caused by protozoa of the genus Cryptosporidium, primarily C. hominis and C. parvum.

-              Infection occurs when oocysts are ingested and mature into sporozoites in the small intestine.

-              In immunocompetent individuals, infection usually causes mild, self-limited profuse diarrhea. Immunocompromised people can have chronic, severe, or life-threatening diarrhea.

-              The oocysts are highly resistant to chlorine and is the leading cause of recreational waterborne disease outbreaks in the U.S.

Amebiasis (Amoebic Dysentery)

-              Caused by Entamoeba histolytica. Can be acute disease or chronic.

-              Infection occurs when cysts are ingested usually via contaminated food or water. Cysts develop into trophozoites in the colon which can invade the intestinal mucosa causing dysentery and abdominal pain.

-              Severe invasion may allow trophozoites to enter the peritoneal cavity or bloodstream, leading to peritonitis or disseminate to other organs.

-              Cysts are resistant to standard chlorination.

-              A small number of population are asymptomatic carriers of E. histolytica, but are still capable of transmitting the parasite and at risk of developing clinical disease.

Cyclosporiasis

-              Caused by a more recently discovered protozoan Cyclospora cayetanensis in tropical or subtropical regions of the world.

-              Infection occurs when oocytes are ingested and lead to watery diarrhea.

-              The 4 oocytes are highly resistant to standard water chlorination.

-              Cases are often linked to imported fresh produce such as cilantro, basil, raspberries, and leafy greens.

Vulvovaginal Candidiasis

-              Superficial infection of the vagina and vulva, most commonly caused by overgrowth of Candida albicans.

-              An opportunistic infection which often occurs because of factors that disrupt the vaginal microbiota or immunity, such as uncontrolled diabetes, altered vaginal pH, hormone change, and prolonged antibiotic therapy.

Trichomoniasis

-              Sexually transmitted infection caused by the protozoan Trichomonas vaginalis.

-              Infects the urogenital tract surfaces in both males and females. Men are usually asymptomatic. Irritation and a profuse, frothy, greenish yellow, foul odor discharge in infected women.

-              Other Trichomonas species, like T. hominis and T. tenax are normal commensals in our body.