PARASITIC DISEASES (PD)

Parasitic diseases Protozoan Helminthic Malaria Amebiasis Giardiasis Toxoplasmosis Leishmaniasis Trypanosomiasis Enterobiasis (pinworm) Cestodiasis (tapeworm) Ascariasis (roundworm) Trichuriasis (whipworm) A parasitic disease is an infectious disease caused or transmitted by a parasite. Many parasites do not cause diseases. PD can affect practically all living organisms, including plants and mammals

Factors responsible for spread and high prevalence of PD Over population and crowding Poor hygiene and sanitation Poor health education Inadequate control of vectors Tourism Immigration Others

Eradication approaches to PD There are three main approaches to control and eradication of PD Chemotherapy Public health measures Vaccination The least feasible is vaccination due to inherent problem associated with vaccine development against parasites which exist in different forms and in different hosts

amebiasis

Is an infection caused by small protozoan parasite Entamoeba histolytica which results in amebic dysentery and hepatic abscess. Amebiasis can be asymptomatic, or it can present as colitis or dysentery. Extraintestinal lesions include abscesses in the liver, lungs, skin, and rarely, the brain. The amebic parasite or trophozoite lives in the lumen of the colon and the colonic mucosa. Trophozoites do not survive outside the host body and, if ingested, will be destroyed by gastric juice. In contrast, the encysted trophozoites can survive drying and freezing: they are killed only by temperatures in excess of 55◦ C or by hyperchlorination of water. Infection occurs by ingestion of cysts present in contaminated water or food. Once ingested by the host, each cyst dissolves in the alkaline media of the small intestine and undergoes asexual division to produce eight trophozoites. The trophozoites, which represent the invasive form of E. histolytica, then move to the large bowel, invade the mucosal crypts, and produce ulcerations. Ulcerations of the bowel wall can result in amebic dysentery, inflammatory lesions in the bowel (amebomas), amebic appendicitis, and perforation of the colon or intestine. The amebae also can enter into the portal vein, which transports them to the liver, where they can produce abscesses. Although rare, genital and cutaneous amebiasis can occur

Amebic dysentery It is also associated with bloody diarrhea, severe abdominal cramps, vomiting, chills and fever. Acute amoebic dysentery may cause complications including appendicitis, perforation or fulminating colitis.

Ameboma: mass of tissue in the bowel that is formed by the amebiasis organism Either chronic intestinal infection or acute amebic dysentery may produce symptoms that mimic cancer or other intestinal disease Peri-anal ulcer: skin infection around the anus with punched out appearance and are painful to touch

Amebic liver abscess (ALA) ALA occur most frequently in young as a result of direct infection of the liver by E. histolytica with the right lobe of the liver being involved in 90% of all cases. Patients usually present with fever; tenderness over an enlarged liver; leukocytosis; elevated transaminases, alkaline phosphatase and sedimentation rate; and anemia extremely serious and have a relatively high mortality rate

Diagnosis Stool examination: Involves microscopically examining the stool for presence of cysts and or trophozoid of E. histolytica A series of 3 stool tests is approximately 90% accurate in confirming the diagnosis of amoebic dysentry

Tests…. Sigmoidoscopy: a thin flexible, lighted instrument used to visually examine lower part of the large intestine for amoebic ulcers and take tissue or fluid samples from the intestine lining Blood test: Blood serum usually test positive for antibody within a week of symptom.

Case study M.B., a 41-year-old Egyptian immigrant, presented to the ED with a 10-day history of abdominal pain and multiple, loose watery stools with occasional streaks of blood. On physical examination, he is a thin man with abdominal distress. His vital signs include temperature, 38◦C; pulse, 88 beats/minute; and BP, 120/80 mm Hg. He has no skin lesions, jaundice, or lymphadenopathy.

The examination is remarkable for slight abdominal distension and right lower quadrant tenderness. Rectal examination reveals tenderness and brown liquid stool positive for occult blood. Sigmoidoscopy demonstrates colonic mucosa that is diffusely edematous and friable. Initial laboratory findings are as follows: Hgb, 13.4 g/dL Hct, 40% Leukocyte count, 13,800 cells/μL with 68% neutrophils, 14% bands, 5% lymphocytes, and 13% monocytes. Albumin, 3.1 g/dL (normal, 3.5–5 g/dL)

A liver scan and liver function tests are normal A liver scan and liver function tests are normal. On ultrasound examination, a tender mass palpable in the lower right quadrant reveals a 3-cm abdominal abscess. During an exploratory operation, the clinician drains 100 mL of a brownish-yellow material. Smears of the drained material are positive for E. histolytica trophozoites, and culture of the material is negative for bacteria. Fresh stool tested for E. histolytica antigen is positive

Question What tells you M.B. has amebic dysentery?

Answer M.B.’s abdominal symptoms, elevated temperature, right lower quadrant tenderness, and occult blood in the stool examination, together with the sigmoidoscopic findings, strongly suggest a bacterial or protozoan infection Stool examination confirms that M.B. has emebiasis; the presence of E. histolytica in the abdominal abscess and bloody stools confirms the diagnosis of amebic colitis

E. histolytica antigen detection test, which detects specific antibody to the amebae in stool, is helpful in nonendemic areas for the differential diagnosis between ulcerative colitis and amebic colitis M.B.’s positive antibody test and identification of E. histolytica in the abdominal abscess confirm the diagnosis of amebiasis

Question What are the major drugs that can be used to treat M.B.? What regimen might be preferred?

Treatment The 2 classes of drugs that can be used to treat M.B.’s amebiasis are the luminal-acting drugs, which act only in the bowel lumen, and the tissue amebicides, which have activity in the bowel wall, liver, and other extraintestinal tissues. Luminal-acting drugs achieve high concentrations in the bowel, but with minimal systemic absorption. They include Iodoquinol (diiodohydroxyquin), diloxanide, and paromomycin. M.B. needs to be treated with a tissue amebicide in combination with a luminal agent because his serology indicates tissue invasion. Tissue amebicides are well absorbed and attain adequate systemic levels to treat extraintestinal amebiasis. Because the concentrations of the tissue drugs in the bowel may be insufficient to eradicate E. histolytica,tissue amebicides must be combined with a luminal-acting agent to treat both intestinal and extraintestinal disease.

The tissue amebicides include metronidazole, tinidazole, chloroquine phosphate, emetine, and dehydroemetine. Chloroquine is effective only as a liver amebicide.

M.B.’s acute amebic dysentery should be treated with a combination of metronidazole and a luminal agent, such as iodoquinol or diloxanide. Either tinidazole or nitazoxanide are alternatives.

case P.C., a 47-year-old man whose stool was found to be positive for E. histolytica cysts on routine examination, was completely asymptomatic. Questions: Would you treat P.C.? What are other drug regimens for amebiasis? If P.C. is not treated, what complications might be encountered?

answer Amebic cyst passer P.C. is an asymptomatic cyst passer, and the infection may be chronic. Invasive amebiasis and extraintestinal disease are potential threats to P.C., and he is a source of infection to others P.C. should be treated with a full course of a luminal amebicide e.g diloxanide ? Failure to treat P.C. places him at risk for amebic liver abscess, lung abscess, amebic peritonitis

PHCP 402 (Parasitic Diseases) amebic pericarditis, brain abscess, amebic strictures and cutaneous amebiasis PHCP 402 (Parasitic Diseases)

toxoplasmosis