pathogens that effect the body

Candida albicans

A fungus that is part of the normal flora; overgrowth due to body imbalance (e.g., after antibiotics) can cause oral thrush and vaginal yeast infections; common in immunosuppressed individuals.

Cryptosporidium hominis

Protozoan found in water; transmitted via fecal-oral route and contaminated food; causes diarrhea with nausea, vomiting, cramps, fever, dehydration; can last up to a month; immunocompromised patients may require anti-protozoal therapy.

Giardia lamblia

Protozoan found in water; mammals can be reservoirs; transmitted via contaminated water or food; symptoms include watery diarrhea, nausea, stomach pain, cramps, gas, greasy stool; dehydration; treated with antiprotozoal drugs; some infections may resolve without treatment.

Entamoeba histolytica

Amoeba transmitted via the fecal-oral route; lives in water; infection can be asymptomatic or cause amoebic dysentery.

Amoebic dysentery

Diarrhea that is more bloody and severe than typical traveler's diarrhea; can be as severe as Giardia infection.

Plantidium coli

Protozoan described as a paranecium or a ciliate; noted as the only human pathogen that is a ciliate; fecal-oral transmission; usually asymptomatic but more severe in immunocompromised individuals.

Penterobius vermicularis

Pinworms; spread via the fecal-oral route; common in children; eggs can contaminate bedding and clothing; symptoms include nocturnal perianal itching; detected by examining the anus with Scotch tape; treated with anti-helminth drugs.

Taenia species

Tapeworms; pork tapeworm common in Taenia species; transmitted through undercooked pork or raw fish; eggs shed in feces and ingested leading to maturation; treated with antihelminth drugs.

Trichinella spiralis

Worm associated with pork; forms cysts in muscle; ingestion of undercooked meat; symptoms include upset stomach, diarrhea, constipation, flu-like symptoms.

Plasmodium species

Protozoa that cause malaria; transmitted by Anopheles mosquitoes; part of the life cycle occurs in the mosquito; symptoms include chills, fever, sweating, fatigue; possible organ failure; treated with antimalarial drugs; prevention focuses on avoiding mosquito bites.

Anopheles mosquito

Mosquito genus that transmits Plasmodium (malaria) to humans; preventing bites is the key preventive strategy.

Toxoplasma gondii

Protozoan found in many mammals; cats are a key reservoir; exposure is often asymptomatic; when present, symptoms resemble mononucleosis; in pregnancy it can cross the placenta causing fetal defects; can cause brain abscess in immunocompromised individuals; avoid cat feces during pregnancy.

Trypanosoma cruzi

Protozoan causing Chagas disease; transmitted by the kissing bug; acute symptoms include fever and a localized chancre; chronic infection can affect the GI tract and heart.

Kissing bug

Triatomine vector for Trypanosoma cruzi; bites around the mouth area; transmits parasite leading to Chagas disease.

Trypanosoma brucei

Protozoan causing African sleeping sickness; transmitted by the tsetse fly; initial chancre and cervical lymphadenopathy; fever; progression to neurological symptoms with sleep disturbance; can be fatal without treatment.

Leishmania species

Protozoan parasites transmitted by sandflies; can cause cutaneous or visceral leishmaniasis.

Acanthamoeba

Free-living amoebae found in streams, ponds, or lakes; can cause amoebic keratitis in the eye and, in some cases, meningitis or encephalitis; infections can be very serious and often deadly.

Dinoflagellates

Algae that produce neurotoxins; toxins can contaminate fish and shellfish; ingestion leads to paralytic shellfish poisoning with tingling and potential paralysis.

Paralytic shellfish poisoning

Neurotoxin-mediated illness from dinoflagellate toxins in contaminated shellfish; initial tingling of lips/tongue/fingers, progressing to weakness and potentially respiratory failure.

Filariasis

Helminth infection of the lymphatic vessels; transmitted by mosquitoes; causes chronic lymphedema and elephantiasis.

Bacillus cereus

A spore-forming bacterium that contaminates foods like rice and pasta and can cause food poisoning via an enterotoxin, with symptoms such as nausea, vomiting, cramps, and diarrhea.

Enterotoxin

A toxin produced by certain bacteria that targets the intestines and triggers GI symptoms like nausea, vomiting, abdominal cramps, and diarrhea.

Bacillus anthracis

A spore-forming bacterium that causes anthrax; can infect skin, lungs, or the gastrointestinal tract if ingested, and contaminated meat can transmit gastrointestinal anthrax.

Clostridium botulinum

An endospore-forming bacterium that produces a neurotoxin causing flaccid paralysis by blocking acetylcholine release at the neuromuscular junction; rapid antitoxin treatment is critical.

Endospore

A dormant, highly resistant form formed by certain bacteria (e.g., Bacillus, Clostridium) that can survive harsh conditions and later germinate.

Clostridium difficile (C. difficile)

An endospore-forming bacterium often acquired after antibiotics disrupt gut flora; causes pseudomembranous colitis with watery diarrhea, cramps, dehydration, and fever; transmitted by spores; treated with antibiotics, probiotics, or fecal transplant.

Pseudomembranous colitis

Inflammation of the colon caused by C. difficile overgrowth, characterized by watery diarrhea and abdominal cramps.

Clostridium perfringens

An endospore-forming bacterium that can cause self-limiting food poisoning; less severe than C. difficile botulinum infections and historically linked to gangrene.

Escherichia coli (E. coli)

A diverse species; most food-poisoning strains are self-limiting, but some virulent strains can cause severe illness and hemolytic uremic syndrome (HUS) requiring medical care.

Hemolytic uremic syndrome (HUS)

A kidney-damaging condition often associated with certain E. coli strains; can lead to kidney failure, especially in children.

Helicobacter pylori

A bacterium that colonizes the stomach, produces urease to neutralize acid, and can cause gastric ulcers; treated with a combination of antibiotics and a stomach-acid reducer (triple therapy).

Triple therapy (H. pylori)

A treatment regimen for H. pylori usually consisting of two antibiotics plus an antacid or proton pump inhibitor to reduce stomach acid.

Salmonella enterica

A species with strains commonly linked to poultry; typically self-limiting but may require antibiotics in severe cases.

Salmonella typhimurium

A Salmonella serovar associated with poultry; usually self-limiting gastroenteritis.

Salmonella typhi

The cause of typhoid fever; fecal-oral transmission; more severe illness with headaches, fever, and abdominal symptoms; untreated mortality ~10%; historically linked to Typhoid Mary.

Typhoid fever

Systemic illness caused by Salmonella typhi, transmitted via the fecal-oral route and requiring antibiotics in severe cases.

Shigella

Bacteria causing shigellosis (dysentery) via the fecal-oral route; usually self-limiting but can be severe and may lead to HUS requiring antibiotics.

Staphylococcus aureus (food poisoning)

Normal skin flora that can contaminate food; produces preformed enterotoxins in improperly stored food, causing rapid vomiting and diarrhea that is usually self-limiting.

Streptococcus mutans

Oral bacteria that ferments sugars to produce acids, leading to dental caries (tooth decay) by enamel erosion.

Vibrio cholerae

Bacterium transmitted mainly through contaminated water; causes cholera with profuse watery diarrhea and dehydration; antibiotics used in severe cases.

Borrelia burgdorferi

Spirochete that causes Lyme disease; tick-borne; early signs may include a bull’s-eye rash and flu-like symptoms.

Ehrlichia chaffeensis

Bacterium transmitted by ticks; causes ehrlichiosis with fever, rash, and flu-like symptoms; deer are common reservoirs.

Francisella tularensis

Also known as rabbit fever; reservoirs include rabbits and small mammals; infection can occur via contact with animals or contaminated meat and may involve skin ulcers and granulomas.

Rickettsia prowazekii

Causes epidemic typhus; transmitted by body lice; reservoir small mammals; fever and rash are common.

Rickettsia typhi

Causes endemic (murine) typhus; reservoir rats; vector rat flea; fever and rash are common.

Rickettsia rickettsii

Causes Rocky Mountain spotted fever; tick-borne; fever, headache, muscle pain with a characteristic rash.

Yersinia pestis

Bacterium that causes bubonic plague; transmitted by fleas; fever, headache, chills, swollen lymph nodes; hypotension can occur.

Clostridium tetani

Endospore-forming bacterium causing tetanus; toxin leads to spastic paralysis; associated with wounds; vaccine and antitoxin are used for prevention and treatment.

Listeria monocytogenes

Bacterium found in soil and water; can contaminate deli meats, soft cheeses, and unpasteurized milk; causes listeriosis, which is usually mild but can cause meningitis in pregnant women, elderly, and newborns.

Neisseria meningitidis

Bacterium that can cause meningococcal meningitis; may be part of normal flora but can invade the CNS and cause rapid-onset meningitis.

Hepatitis A

Virus transmitted via the fecal-oral route; usually milder hepatitis with possible jaundice; vaccine available for prevention.

Hepatitis B

Bloodborne virus with chronic carrier state; important in healthcare settings; has a three-dose vaccine schedule.

Hepatitis C

Bloodborne virus commonly spread by contaminated needles or blood products; often asymptomatic until later; can become chronic with liver disease; no vaccine.

Hepatitis D

Defective virus that requires hepatitis B for infection; vaccination against hepatitis B reduces risk of hepatitis D.

Mumps virus

Respiratory virus causing parotitis (swollen salivary glands); part of the MMR vaccine; can cause infertility in males in some cases.

Norovirus

Highly contagious cause of gastroenteritis; sudden onset vomiting and diarrhea; transmitted by contaminated food, water, or surfaces.

Rotavirus

Viral gastroenteritis mainly in children; diarrhea with fever and vomiting; onset about 48 hours; dehydration risk; vaccines available.

Cytomegalovirus (CMV, HHV-5)

Human herpesvirus 5; often asymptomatic but can cause congenital CMV with birth defects and disease in immunocompromised individuals.

Epstein-Barr virus (EBV, HHV-4)

Herpesvirus that commonly causes infectious mononucleosis; presents with fever, sore throat, swollen glands; historically called the kissing disease; no specific antiviral therapy.

Human immunodeficiency virus (HIV)

Retrovirus that attacks CD4+ T cells, compromising the immune system; transmitted via body fluids; progresses through acute, latent, and AIDS stages with opportunistic infections.

Ebola virus

Virus originating in bats; highly contagious through direct contact; causes hemorrhagic fever with fever, severe headache, vomiting, diarrhea, and bleeding; high mortality.