Parasitology 5

Question 1

Describe the life cycle of Leishmania species.

Answer 1

sandfly takes a blood meal and injects larvae into human
larvae infect the macrophages of human and mature
sandfly takes a blood meal and ingests macrophages with mature , within the sandfly, the infectious is released into eh mid gut of the sandfly

Question 2

What are the reservoir and route of transmission for leishmania sp? Where is this infection found?

Answer 2

transmission by sandfly between reservoirs: domestic and wild animals, humans are the only reservoir for L. major

found mostly within the tropics or anywhere with contact with sandfly/reservoir habitat

Question 3

Name and describe the manifestations of leishmaniasis.

Answer 3

cutaneous: bump that ulcerates into a sore that spontaneously can heal but often leaves scars
mucocutaneous: ulceration of nasopharynx tissues due to metastasis months after primary lesion, immunity with chemotherapeutic cure

visceral leishmaniasis: onset at 2-12mo leads to fever and wasting, splenomegaly or hepatomegaly, chemotherapeutic cure leads to immunity

Question 4

Describe the dx and treatment of leishmaniasis.

Answer 4

biopsy or aspirate of lesion stains with giemsa reveals amastigotes

tx: Cutaneous- fluconazole reduces scarring
Mucocutaneous:
Mucocutaneous: antimonials and Am B as a secondary
Visceral: miltefosine, Am B as alternate

Question 5

List the species of African trypoanosomiasis that is present primarily in West and East Africa. How is it diagnosed?

Answer 5

West Africa: T. brucei gambiense (human reservoir) chronic
East Africa: T. brucei rhodensiense (human incidental host) rapid progression

both are transmitted by tse tse fly

Dx: (difficult) direct examination of blood and lymph of extracellular parasites, card agglutination test (not very accurate)

Question 6

Describe the syndrome that follows with African trypanosomiasis.

Answer 6

begins as a self-healing chancre from the bite of tse tse fly
hemoatogenous dissemination occurs through the lymphatics and tissue causing waves of parasitemia with fever
lymphadenopathy is often present (Winterbottom’s sign)
eventual CNS infection causes edema, dementia, sleepy motor impairment and death through coma or secondary infection

Question 7

How is trypanosomias treated?

Answer 7

acute illness
pentamidine for T.b. gambiense (well tolerated)

second stage tx:
melasoprol (contains arsenic)
eflornithine (against T.b. gambiense)
eflornithine and nifurtimox every 12hr for 7d

Question 8

Describe the organism, reservoir and transmission of Chagas disease.

Answer 8

Trypanosome cruzi
spread by reduviid bug between warm blooded reservoirs
can also be spread by transfusion, transplantation and IV drug use

endemic to SA

Question 9

Describe the life cycle of T. cruzi.

Answer 9

sexual reproduction occurs within the midgut of the reduviid bug and bites a human
assexual reproduction occurs within tissues of the human
redivide bug can acquire mature parasite from humans

Question 10

Describe the syndrome caused by T. cruzi.

Answer 10

acute: 2-4mo fever, Romana’s sign, hematogenous spread (large parasite load can lead to death in children)
chronic: 10-20yrs no circulating trypanostigotes, but damage to the nerve and muscles, esp of heart, esophagus and colon (inflammation and autoimmunity lead to severe tissue damage

death from sudden heart attack is common

Question 11

How is T. cruzi dx and treated?

Answer 11

acutely you an see trypomastigotes in the blood, chronic xenodianosis or strip assay for T. cruzi antibodies

tx with benzidasole, nifurimox in acute stage; neither effective in chronic disease

Question 12

How is trichomonas vaginalis transmitted?

Answer 12

by direct sexual contact, but also stable for up to 24hrs (sex toys can be contaminated); condoms will not prevent 100%

no free living or encysted stages

Question 13

Describe the syndrome caused by trichocomonas vaginallis.

Answer 13

70% of infected people are asymptomatic

females: vaginits, burning and itching, inflammation of squamous epithelia or frothy vaginal discharge with usual odor; can cause preterm delivery and low birth weight babies, increases risk of acquiring HIV
males: itching or irritation inside penis, burning after uneaten or ejaculation, may present with mild discharge

Question 14

How is trichomonas vaginalis dx. and tx?

Answer 14

dx. by microscopic observation of motile parasites, DNA test is often available
tx. with metronidazole, if resistant use tinidazole; screen sexual partner, check for other STDs