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Parasitic helminths are divided into two phyla:
Nemathelminthes (roundworms), platyhelminthes (flatworms)
Flatworms have two classes
Trematoda (flukes), and cestoda (tapeworms)
Parasite that can be transmitted through ingestion of contaminated food and/or water
- Ascaris lumbricoides
- Trichuris trichiura
- Trichinella spiralis
- Taenia solium
- Taenia saginata
- Diphyllobothrium latum
Class of parasite that causes malaria
Plasmodium: Female Anopheles mosquito blood-sucking insect
- P. vivax, P. malariae, P. ovale, P. knowlesi, P. falciparum
Cause of Amoebic dysentery
Entamoeba histolytica:
intestinal and tissue amoeba
It’s transmitted by fecal-oral route through ingestion of cysts in contaminated water
How is Giardia lamblia transmitted
Ingestion of the cyst from fecally contaminated water or food.
The Cyst enters the stomach and is stimulated by the gastric acid to undergo excystation in duodenum before attaching to duodenal mucosa through sucking disks. Damage to intestines leads to diarrhea with malabsorption of fat and proteins.
Protozoan that is transmitted via cat feces
Toxoplasma gondii: develops in intestinal cells of cats and passes to tissues through the bloodstream before being passed in the feces and maturing in an external environment
Largest intestinal protozoan of humans
Balantidium coli
Examples of a tapeworm
Taenia saginata (Beef tapeworm)
- Taenia solium (Pork tapeworm)
- Diphyllobothrium (Broad Fish tapeworm)
- Hymenolepsis nana (Dwarf Tapeworm)
- Echinococcus granulosus (Dog tapeworm/Hyadatid Tapeworm)
Diphyllobothrium latum
Longest of the tapeworms (reaching 13 meters)
Acquired through improperly cooked or raw fish containing plerocercoid
Copepods are first intermediate host
Freshwater fish are second intermediate host
Definitive host are humans
Scolex:
organ attached to the head that can consist of hooks, suckers, or sucking grooves, or rostellum
Proglottids
segments that divide the body. A series of proglottids is called strobila
The neck is the region of growth, the worm grows by adding new proglottids from the neck. Oldest proglottids are at the most distal part of the body
What causes hydatid disease
Echinococcus granulosus
Tapeworm that requires and does not require intermediate host
H. nana
Chinese liver fluke:
Stages: egg, larva, adult. Egg has operculum surrounded by thick rim (shoulder)
First intermediate host: freshwater snail
Second intermediate host: freshwater fish
Most patients are asymptomatic. Fever, upper abdominal pain, anorexia, hepatomegaly, diarrhea, eosinophilia in high worm burden.
Fasciola hepatica
(Sheep liver fluke):
Also has shoulders
Eggs mature in water and infect first intermediate host
First intermediate host: snail
Natural host for completion of life cycle: sheep
Second intermediate host: edible aquatic plants
Humans serve as accidental hosts
Adult worms live in biliary passages of liver
Treatment uses dichlorophenol, triclabendazole
Katayama fever:
Systemic hypersensitivity reaction to migrating schistosomes, usually S. japonicum. Characterized by rapid onset of fever, myalgia, body malaise, cough, diarrhea, eosinophilia 1-2 months after parasite exposure. Swollen lymph nodes, and enlargement of liver, spleen may also occur. Can lead to portal hypertension. Internal bleeding from rupture esophageal varices is common cause of death.
Paragonimus westermani
lung fluke, causes paragonimiasis, a disease affecting humans and animals. The infection is acquired by ingesting raw or undercooked crustaceans like crabs and crayfish that contains its metacercariae. The parasite migrates to the lungs. Chest x-rays may be done for diagnosis
Largest intestinal fluke of humans
Fasciolopsis buski (Large intestinal fluke)
What causes perianal itching
Enterobius vermicularis (pinworm, seatworm) acquired through ingestion of eggs. Larvae emerge from eggs and mature into adults in the large intestines. Impregnated female worms migrate to the perianal region where egg laying occurs
Different stages of Ascaris lumbricoides
Acquired through ingestion of food contaminated with human feces containing infective embryonated ova. Larvae are released in the small intestines and penetrate the intestinal wall to go to the liver and localize to the lungs. They gain entrance into air sacs and are then swallowed, returning them into the intestines. They mature into adult worms in the small intestines where they lay their eggs that are eliminated in feces
Trichuris trichiura
Human whipworm - barrel or football shape with prominent hyaline plug at each end of the egg.
Humans acquire infection through ingestion of food or water contaminated by human feces containing infective eggs. Larvae become immature adults in the small intestines and migrate to the colon to mature and mate. Thousands of eggs are produced each day.
Elephantiasis
also known as lymphatic filariasis, is caused by parasitic worms called filarial nematodes, particularly Wuchereria bancrofti, Brugia malayi, and Brugia timori. These worms are transmitted by mosquitoes, causing inflammation and damage to the lymphatic system, which can lead to the characteristic skin thickening and swelling associated with elephantiasis.
Impetigo
Common in young children and involves face and limbs. Starts as a flattened red spot (macule) that becomes pus-filled, ruptures, and forms crust.
Sty/hordeolum
folliculitis occurring at the base of eyelids
Staphylococcal scaled skin syndrome
Primarily found in newborns and young children. Sudden onset of erythema covering the whole body within 2 days. Skin displaces when pressure is applied (Nikolsky sign)
Infection acquired in tropical areas through contact with soil
commonly known as intestinal worm infections, are a major health concern. These infections are caused by parasitic worms like roundworm, whipworm, and hookworm. They are contracted through direct contact with soil contaminated by human feces containing the worms' eggs
Parasite that causes pulmonary symptoms
Also called Woolsorter’s disease, pulmonary anthrax or inhalation anthrax is transmitted by inhalation of spores of Bacillus anthracis into the lungs. Begins with symptoms resembling influenza which rapidly progresses to edema
P. Westermani
commonly known as the lung fluke, is a parasitic flatworm that causes paragonimiasis, a disease affecting humans and animals. The infection is acquired by ingesting raw or undercooked crustaceans like crabs and crayfish that harbor the parasite's metacercariae. The parasite migrates to the lungs, where it matures and causes various symptoms
Loeffler's syndrome
is a type of eosinophilic pulmonary disease primarily caused by larval migration of certain helminths, such as Ascaris, hookworm, and Strongyloides, through the lungs during parasitic infections. It's characterized by mild respiratory symptoms like dry cough, wheezing, and fever, along with fleeting migratory pulmonary infiltrates on chest x-rays and peripheral blood eosinophilia
Parasites in sputum and Parasites that undergo lung migration
Paragonimus westermani, Roundworm (Ascaris lumbricoides), Hookworms (Ancylostoma duodenale and Necator americanus), Strongyloidiasis (Strongyloides stercoralis), Lung Flukes (Paragonimus)
Common Protozoa worldwide that cause GI infection
Helicobacter pylori - most common cause of chronic gastritis and peptic ulcers. Rapid motility enables it to penetrate the mucus blanket lining the stomach. Natural habitat is the stomach but can also be found in saliva
flask-shaped ulcer
is a characteristic lesion associated with amebiasis, an intestinal infection caused by the parasite Entamoeba histolytica. These ulcers are named for their distinctive shape, resembling a flask due to a wider, shallower superficial crater that narrows down into a deeper, more tubular or cone-shaped structure
Ascaris lumbricoides
commonly known as the roundworm, is the most prevalent helminth that can cause intestinal obstruction. In severe cases, heavy infestations of Ascaris lumbricoides can lead to a complete or partial blockage of the small intestine
B. coli
is morphologically more complex than E. histolytica. Has a cytosome, nucleus, food vacuoles, and contractile vacuoles. The infective stage is the cyst and the pathogenic stage is the trophozoite
Cryptosporidiosis
is a diarrheal illness caused by the parasite Cryptosporidium. It's transmitted through the fecal-oral route, often by swallowing contaminated water or food, or direct contact with infected individuals or animals. Symptoms include watery diarrhea, stomach cramps, nausea, vomiting, low-grade fever, and loss of appetite
T. vaginalis
Pear-shaped organism with a central nucleus, four anterior flagella, and undulating membrane. It exists only in the trophozoite form. Main mode of transmission is sexual intercourse. Infection is highest among sexually active women in their 30s and lowest in post-menopausal women.
Infection in men is usually asymptomatic, men serve as a reservoir for infection in women. Infection in women is also asymptomatic, may present with scan watery vaginal discharge. Cervix appears very red with small punctuate hemorrhages (strawberry cervix). Can infect infants that pass through bird canal during delivery.
Pyelonephritis
Kidney infection
Cystitis
Inflammation of the bladder. Suprapubic pain and tenderness, frequency, occasional hematuria.
Parasites that cause uti (related to hematuria and bladder pathology)
Enterobacteriaceae - Escherichia coli: most common
- Klebsiella pneumoniae:
- Enterococcus facecalis: most common among enterococci. Frequent causes of nosocomial infections.
- Pseudomonas, Proteus, Serratia: Serratia a major entity in nosocomial infections.