Microbiology - Diseases of the Digestive System | Biology

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Study GuideMicrobiology–Diseases of the Digestive System1.Protozoal Diseases of the Digestive SystemProtozoa are single-celled organisms that can infect the digestive system when contaminated food orwater is consumed. These infections often cause diarrhea and abdominal discomfort and can beespecially dangerous for people with weakened immune systems. Below are the most importantprotozoal diseases of the digestive tract.1.1Amoebic DysenteryAmoebic dysentery is caused by the amoebaEntamoeba histolytica.In the environment, this protozoan exists in acyst form, which allows it to survive outside the body.Humans become infected by eating food or drinking water contaminated with these cysts.Once inside the body, the cysts releasetrophozoites, which are the active, feeding forms. Thesetrophozoites invade theintestinal lining, causing tissue damage. From there, they may enter thebloodstream and spread to other organs, especially theliver and lungs.Infected individuals pass cysts in their stool and may remaincarriers for long periods, even ifsymptoms are mild or absent. Treatment is usually effective with the drugmetronidazole.1.2GiardiasisGiardiasis is caused byGiardia lamblia, a protozoan that moves using flagella.The organism enters the body in itscyst formthrough contaminated food or water. In the intestine,the cysts release trophozoites, which attach to the intestinal wall and multiply.Symptoms commonly include:•Foul-smelling, watery diarrhea•Abdominal pain•Intestinal discomfortPeople who enjoy outdoor activities such ashiking, backpacking, and campingare at higher risk.This is because untreated mountain streams may contain Giardia cysts from wild animals.The infection is treated withmetronidazole, which is usually very effective.

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Study Guide1.3BalantidiasisBalantidiasis is caused byBalantidium coli, aciliated protozoan.As with other protozoal infections, the organism enters the body as acyst. Inside the intestine,trophozoites emerge and may invade the intestinal tissue.Symptoms include:•Persistent diarrhea•Blood and pus in the stool•Long-lasting digestive problemsPeople with balantidiasis often becomelong-term carriers. Treatment withmetronidazoleiscommonly used.1.4CryptosporidiosisCryptosporidiosis is caused by species ofCryptosporidium, includingC. parvumandC. coccidi.These organisms invade theintestinal epithelial cellsand cause a mild form of gastroenteritis inhealthy individuals. Symptoms include:•Abdominal pain•Watery diarrheaIn people withAIDS or other immune system disorders, the disease can become extremelysevere. The diarrhea may be massive and potentiallyfatal.At present,no effective treatmentis known. The disease is mainly spread throughcontaminatedwater, and many standard water purification methods do not eliminate the organism. Because of this,improved water treatment techniques are currently being explored.Key TakeawayProtozoal diseases of the digestive system are usually spread through contaminated food or water.While some infections cause mild discomfort, others can lead to serious illness, especially inimmunocompromised individuals. Safe drinking water, proper hygiene, and timely treatment areessential for prevention and control.

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Study Guide2.Parasitic Diseases of the Digestive SystemParasitic diseases of the digestive system are most often caused byworms, also known ashelminths. These parasites usually live and multiply in the intestines. When the number of wormsbecomes large, symptoms of disease begin to appear.Poor sanitation, contaminated food and water, and lack of hygiene greatly increase the risk of theseinfections.2.1Pinworm DiseasePinworm disease is caused by a small roundworm calledEnterobius vermicularis.Infection occurs whenpinworm eggs are swallowed, often through contaminated hands, food, orobjects. After the eggs hatch, adult female worms lay eggs near theanus, which causes itching.This disease is most common inyoung children, especially in crowded or daycare settings. Severalmedications are available and effective for treating pinworm infections.2.2Roundworm DiseaseRoundworm disease is caused byAscaris lumbricoides.People become infected by ingestingroundworm eggsin contaminated food or water. Once insidethe body, the larvae:1.Hatch in the intestine2.Burrow through the intestinal wall3.Enter the bloodstream and travel to thelungsFrom the lungs, the worms are coughed up, swallowed, and returned to the digestive system, wherethey mature.Heavy infections can cause:•Respiratory distress•Intestinal obstruction

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Study Guide2.3Hookworm DiseaseHookworm disease is caused by two species:•Ancylostoma duodenale(Old World hookworm)•Necator americanus(New World hookworm)Unlike many other parasites, hookworm larvaeenter through the skin, usually through bare feet.After entering the body, the larvae travel:•From the bloodstream to the lungs•Then are coughed up and swallowed•Finally reaching the intestinesIn the intestine, hookworms attach to the intestinal lining using hooks andfeed on blood. This leadsto:•Anemia•Fatigue•WeaknessHookworm disease is common in areas where peoplewalk barefoot.2.4StrongyloidiasisStrongyloidiasis is caused by the roundwormStrongyloides stercoralis.The larvae penetrate the skin and follow a similar path as hookworms, eventually reaching thedigestive system. Heavy infestations can cause:•Large numbers of worms•Intestinal blockageInimmunocompromised individuals, the worms may invade the intestinal wall, making the diseasemore severe and dangerous.2.5Whipworm DiseaseWhipworm disease is caused byTrichuris trichiura, named for itswhip-shaped body.

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Study GuideInfection occurs when eggs are swallowed in contaminated food or water. Inside the intestine:•Eggs hatch into adults•Adults produce eggs that leave the body in fecesLarge numbers of whipworms cause:•Intestinal irritation•Inflammation•Symptoms of obstruction2.6TrichinosisTrichinosis is caused byTrichinella spiralis.Humans become infected by eatingundercooked porkthat contains cysts in muscle tissue. Afteringestion:•Worms mature in the intestine•Larvae enter the bloodstream•Cysts form inmuscle tissuesSevere pain occurs when large numbers of worms invade:•Rib muscles•Heart muscle•Diaphragm•LungsProper cooking of porkis the most important way to prevent trichinosis.2.7Taeniasis (Tapeworm Infection)Taeniasis is caused bytapeworms, which are flatworms. Two species commonly infect humans:•Taenia solium(pork tapeworm)•Taenia saginata(beef tapeworm)

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