Parasitic infections Flashcards
(126 cards)
1
Q
Define infection.
A
Invasion by and growth of pathogenic microorganisms within the body.
2
Q
Define disease.
A
A disordered or incorrectly functioning organ, part, structure, or system of the body resulting from the effect of genetic or developmental errors, infection, poisons, nutritional deficiency or imbalance, toxicity, unfavourable environmental factors.
Illness, sickness, ailment.
3
Q
Define parasite.
A
Organism living in or on the host (endoparasites or ectoparasites) and dependent on the host for nutrition- causing damage.
4
Q
What are the two types of endoparasites?
A
Protozoa
Metazoa
5
Q
What are the different types of protozoa?
A
Amoeba, coccidiae, ciliate, flagellates.
6
Q
What are the different types of metazoa?
A
Roundworms, flatworms, flukes.
7
Q
What are protozoa?
A
Single celled organisms. Eukaryotes (genome within a nucleus, complex organelles in cytoplasm). Pathogenesis varied. Some have insect vectors (e.g. malaria). No eosinophilia.
8
Q
What are metazoa?
A
Multicellular organisms (helminths/worms). Free living, intermediate hosts and vectors. Some just inhabit gut (geohelminths), others invade tissues. Eosinophilia- if invade blood.
9
Q
Give examples of amoebae.
A
Entamoeba histolytica
Entamoeba dispar
10
Q
What is the route of transmission of amoebae?
A
Infection occurs by ingestion of mature cysts in food or water, or on hands contaminated by faeces.
11
Q
What is the third most common cause of death of parasitic infections, after schistosomiasis and malaria?
A
Entamoeba histolytica (amoeba).
12
Q
Where is Entamoeba histolytica infection most common?
A
South and Central America, West and Southeast Asia- warm climates.
Rare in temperate climates.
13
Q
What percentage of Entamoeba histolytica infections are asymptomatic?
A
90%.
The remaining 10% produce a spectrum of disease varying from dysentery to amoebic liver abscess.
14
Q
What is the difference between Entamoeba histolytica and Entamoeba dispar?
A
E. histolytica is the cause of invasive amoebiasis.
E. dispar is a normal commensal of the GI tract.
15
Q
What is the treatment for amoebiasis?
A
Nitroimidazole derivatives (act on trophozoite, but not on cysts) + parmomycine or diloxanide furoate.
16
Q
How is amoebiasis diagnosed in the laboratory?
A
Wet mount.
Entamoeba histolytica and Entamoeba dispar are morphologically identical species.
In bright-field microscopy, cysts are spherical and usually 12-15µm (range may be 10-20µm).
A mature customers has 4 nuclei, while an immature cyst may contain 1-3.
17
Q
Give examples of coccidiae.
A
Plasmodium species, causing malaria- mosquito borne.
Toxoplasma, causing toxoplasmosis- cats/kittens.
Cryptosporidium, causing diarrhoea- waterborne.
Coccidian infections in humans are mostly zoonoses.
18
Q
What is toxoplasmosis?
A
Mild disease in immunocompetent individuals: fever, swollen lymph nodes, headaches, sore throat.
In pregnancy, poses serious danger to the foetus.
Transmitted to humans by cats/kittens.
19
Q
What are the different types of plasmodium?
A
P. falciparum P. malariae P. ovale P. vivax P. knowlesi
20
Q
What are the 2 types of plasmodium host?
A
Humans
Female Anopheles mosquitoes
21
Q
What are the 2 stages of the plasmodium life cycle?
A
Liver stage- parasite invades liver cells, multiplies and ruptures.
Blood stage.
22
Q
What are the symptoms of malaria?
A
Fever Headache Chills Vomiting Muscle pain Paroxysm (cycle in 4-8 hours)
23
Q
What are the possible complications of malaria?
A
Severe anaemia (destruction of red cells.
Cerebral malaria (swelling of the brain, seizures, coma).
Liver failure.
Shock.
Pulmonary oedema.
Abnormally low blood sugar (hypoglycaemia).
Kidney failure.
Swelling and rupturing of the spleen.
24
Q
What are the treatment options for uncomplicated anaemia?
A
Chloroquine, Atovaquone-proguanil, Artemether-lumefantrine, quinine sulfate plus one of the following: Doxycycline, Tetracycline or Clindamycin Quinine sulfate, Mefloquine.
25
How is severe malaria treated?
Artemisinin-based combination therapy (ACT) is recommended for the treatment of P. falciparum malaria.
26
How is malaria diagnosed?
Blood film, Giemsa stained.
| Rapid test: commercially available antigen detection tests (more expensive and less sensitive).
27
What are the routes of infection for toxoplasma gondii (leading to toxoplasmosis)?
Eating undercooked meat of animals harbouring tissue cyss
Consuming food or water contaminated with cat faeces
By contaminated environmental samples
Blood transfusion
Organ transplantation
Transplacentally from mother to foetus
28
What symptoms does cryptosporidium (cryptosporidiosis) cause?
Diarrhoea
Fever
Nausea
Vomiting
29
How is cryptosporidiosis diagnosed?
Stool examination.
30
How is cryptosporidiosis treated?
Fluid rehydration.
31
What are the reservoir hosts of ciliates (e.g. Balantidium coli)?
Pigs, rodents, primates.
32
What symptoms does Balantidium coli (balantidiasis) cause?
```
Most people are asymptomatic.
Immunocompromised patients may experience more severe signs and symptoms:
-persistent diarrhoea
-dysentery
-abdominal pain
-weight loss
-nausea
-vomiting
If left untreated, perforation of the colon can occur.
```
33
How is balantidiasis diagnosed?
Stool examination.
34
Give examples of flagellate parasites.
Giardia lamblia (giardiasis).
Trichomonas (trichomoniasis).
Leishmania (leishmaniasis).
35
What symptoms does Giardia lamblia cause?
```
DIARRHOEA
Greasy stools that tend to float
Stomach or abdominal cramps
Upset stomach or nausea/vomiting
Dehydration (loss of fluids)
Most people are asymptomatic.
```
36
What is the commonest globally distributed waterborne protozoal infection?
Giardiasis.
37
How is giardiasis diagnosed?
Stool examination for cysts and trophozoites.
38
How is giardiasis treated?
Metronidazole/tinidazole.
39
How is trichomonas transmitted?
Sexual intercourse.
40
What is the most common, curable, non-viral sexually transmitted infection in the UK?
Trichomoniasis.
41
Where does trichomonas live in women?
Vagina, urethra and paraurethral glands.
42
Where does trichomonas live in men?
Urethra.
43
What are the symptoms of trichomoniasis infection in females?
```
10-50% are asymptomatic.
Vaginal discharge.
Vulval itching.
Dysuria or offensive odour.
Not specific for TV.
Occasionally the presenting complaint is of lower abdominal discomfort or vulval ulceration.
```
44
What are the symptoms of trichomoniasis infection in males?
15-50% of men are asymptomatic.
| Discharge and/or dysuria.
45
What are the possible complications of trichomoniasis infection?
Detrimental outcome on pregnancy and is associated with preterm delivery and low birth weight.
May enhance HIV transmission and there may be an increased risk of TV infection in those that are HIV positive.
46
How is trichomoniasis diagnosed?
Microscopy- detection of motile trichomonads in swab/urine.
| Trichomonas rapid test.
47
How is trichomoniasis treated?
Metronidazole.
48
What are helminths (metazoan parasites)?
Complex multicellular parasites.
Cycles may involve insect vectors and intermediate hosts.
For most, humans are the definitive host- few are zoonoses (acquired from animals),
Adult worms cannot multiply in man- number of adults related to infection.
Lay eggs, microfilaria, larvae.
49
What are the different types of parasitic worms?
Roundworms (nematodes): Ascaris, hookworm, Filaria, Strongyloides.
Flatworms (cestodes): Taenia (tapeworms).
Flukes (trematodes): Schistosoma.
50
How is giardia transmitted?
Faeco-oral route.
51
What are the 4 most common helminth infections worldwide?
Ascariasis- 1221 million cases.
Trichuriasis- 795 million cases.
Hookworm- 740 million cases.
Schistosomiasis- 200 million cases.
52
Where do ascaris worms (nematodes) live in humans?
Lumen of the small intestine.
53
How are ascaris worms (nematodes) transmitted?
Faeco-oral route.
54
How long can adult ascaris worms (nematodes) live for?
1-2 years.
55
What environmental conditions are optimal for embryonation of ascaris worm eggs so that they become infective?
Moist, warm, shaded soil.
56
What are the symptoms/pathology of ascariasis infection?
Often asymptomatic.
Infections with a large number of worms may cause abdominal pain or intestinal obstruction.
Adults feed on the contents of the small intestine and in heavy infections, this may compound problems in malnourished individuals (especially children).
Migration of larvae may cause localised reactions in various organs.
Penetration of the larvae from capillaries into the lungs can lead to Loeffer’s pneumonia, in which pools of blood and dead epithelial cells clog air spaces in the lungs.
Resulting bacterial infections can be fatal.
57
How is ascariasis infection diagnosed?
Stool examination.
58
How is ascariasis infection treated?
Albendazole and mebendazole.
59
Give an example of a hookworm (nematode).
Ancylostoma duodenale.
60
What is the size and shape of adult hookworms, and how do they attach to the host?
About 1cm long, curved.
| Attached by their buccal capsules to the villi of the small intestine.
61
What is the main problem caused by hookworms (nematodes)?
Iron deficiency anaemia- so well attached to the villi that they cause bleeding.
62
What are the symptoms/pathology of Ancylostoma duodenale hookworm (nematode) infection?
Iron deficiency anaemia (caused by blood loss at the site of intestinal attachment of the adult worms) is the most common symptom of hookworm infection, and can be accompanied by cardiac complications.
Gastrointestinal and nutritional/metabolic symptoms can also occur.
Local skin manifestations (‘ground itch’) can occur during penetration by the filariform (L3) larvae, and respiratory symptoms can be observed during pulmonary migration of the larvae.
63
How is Ancylostoma duodenale hookworm (nematode) infection diagnosed?
Stool examination.
64
How is Ancylostoma duodenale hookworm (nematode) infection treated?
Albendazole and mebendazole.
65
Give examples of hookworms (nematodes).
```
Ancylostoma duodenale.
Trichuris trichiuria (whipworm).
```
66
How long are adult trichuris trichiuria (whipworm) hookworms (nematodes), and where do they reside in humans?
The adult worms (approximately 4cm in length) live in the caecum and ascending colon. Fixed in location.
67
What symptoms does trichuris trichiuria (whipworm) hookworm (nematode) infection cause?
Small amounts of whipworms might not cause any symptoms.
If there are hundreds of worms, there might be bloody diarrhoea and anaemia due to severe vitamin and iron loss.
The worms leave open wounds, which cause inflammation of the intestinal wall.
In some cases, rectal prolapse may develop.
68
How is trichuris trichiuria (whipworm) infection diagnosed?
Stool examination.
69
How is trichuris trichiuria (whipworm) infection treated?
Albendazole and mebendazole.
70
How is trichuris trichiuria (whipworm) being used as a novel treatment?
Whipworm is one of the worms being used in helminthic therapy which helps against allergies and autoimmune diseases.
71
How is trichuris trichiuria (whipworm) transmitted?
Faeco-oral route.
72
Give examples of filaria (roundworms, nematodes).
Brugia malayi- elephantiasis.
| Wucheria bancrofti.
73
How does filaria infection cause elephantiasis?
Lymphatic obstruction by filaria (especially in the legs) can progress to elephantiasis- can also occur in arm, breast, scrotum.
74
How is lymphatic filariasis diagnosed?
The microfilariae are found mainly in the peripheral blood and can be found at peak amounts from 10pm to 4am.
During the day, they are present in the deep veins, and during the night, they migrate to the peripheral circulation.
Blood smear or antigen detection with an immunochromatic test (card) or ELISA.
75
How are filaria parasites (e.g. Loa loa) transmitted?
Insect vector- Chrysops fly.
76
How is lymphatic filariasis treated?
Albendazole and ivermectin.
77
Give an example a filaria parasite.
Loa loa- eye worm, causing loaiasis.
78
How long can an adult loa loa filaria worm live in humans?
4-12 years.
79
Give an example of a flatworm (cestode) parasite.
Taenia (tapeworm).
80
How is taenia (tapeworm) transmitted?
Eating raw or undercooked meat or eggs.
81
What are the symptoms of taenia (tapeworm) infection?
Most people have no symptoms, or mild symptoms.
Patients with T. saginata taeniasis often experience more symptoms (size of the worm up to 10m) than those with T. solium or T. asiatica (~3m).
Tapeworms can cause digestive problems including abdominal pain, loss of appetite, weight loss, and upset stomach.
The most visible sign of taeniasis is the active passing of tapeworm segments.
82
How is taenia (tapeworm) infection diagnosed?
Segment in stool or identification of eggs in stool.
83
How is taenia (tapeworm) infection treated?
Praziquantel.
84
What disease does Taenia solium infection cause?
Cystericercosis.
85
What is the most common acquired cause of epilepsy worldwide?
Taenia solium infection- cysticercosis.
86
Give an example of a fluke (trematode) parasite.
Schistosoma.
87
What are the different types of schistosoma parasites?
S. mansoni
S. haematobium
S. japonicum
88
What are the symptoms of schistosomiasis?
Within days: possible rash or itchy skin.
Within 1-2 months: fever, chills, cough and muscle aches, but most people have no symptoms at this early phase of infection.
When adult worms are present, the eggs that are produced usually travel to the intestine, liver or bladder, causing inflammation or scarring.
Children who are repeatedly infected can develop anaemia, malnutrition, and learning difficulties.
After years of infection, the parasite can also damage the liver, intestine, lungs and bladder.
89
How is schistosomiasis diagnosed?
Stool or urine samples.
90
How is schistosomiasis treated?
Praziquantel.
91
Give examples of ectoparasites.
Sarcoptes scabiei (scabies).
Pediculus humanus capitis (head louse).
Pediculus humanus corporis (body louse, clothes louse).
Pthirus pubis ('crab' louse, pubic louse).
92
How is scabies diagnosed?
Appearance of rash and presence of burrows in the skin.
93
How is scabies treated?
Scabicides.
94
How is scabies transmitted?
Direct contact.
95
How are ectoparasites transmitted?
Direct contact.
96
What type of parasite is Leishmania?
Protozoan flagellate, endoparasite.
97
How is the Leishmania parasite transmitted?
Vector- sandfly.
98
What are the 2 forms of Leishmania parasite?
Promastigote.
| Amastigote.
99
What are Leishmania promastigotes?
Form of Leishmania within sandfly vector.
Move in the direction of their flagellum.
Can be cultured.
100
What are Leishmania amastigotes?
Form of Leishmania within human or other vertebrate host's cells (have resorbed their flagellum).
They are no longer motile.
101
Describe the distribution of sandflies.
Found mainly in the warm parts of the world, including southern Europe, Asia, Africa, Australia, Central and South America.
Climate change: in Europe, transmission of Leishmania is spreading northwards from Greece and Turkey and occurs in southern France, and is currently spreading through Italy.
102
Describe the appearance and behaviour of sandflies.
Small (3mm).
Hairy.
They hop around before settling down to bite.
Unlike mosquitoes, their attack is silent.
Female, not male, feed on blood which provides nutrition for their eggs.
103
What are the major forms of leishmaniasis?
Visceral leishmaniasis (Kala azar).
Cutaneous leishmaniasis.
-diffuse cutaneous leishmaniasis
-mucocutaneous leishmaniasis
104
What is visceral leishmaniasis characterised by?
Characterised by irregular fever, weight loss, swelling of liver and spleen, anaemia.
Affects internal organs.
105
What is the most severe form of leishmaniasis?
Visceral leishmaniasis.
106
What are the risk factors for development of visceral leishmaniasis?
Malnutrition
Immunosuppressive drugs
HIV co-infections
107
What is cutaneous leishmaniasis characterised by?
Skin lesions on exposed body parts, often self-healing.
Can create serious disability and scars.
Immunity to reinfection.
108
What is diffuse cutaneous leishmaniasis characterised by?
Disseminated lesions, resembles leprosy.
| Difficult to treat, no spontaneous healing, frequent relapse.
109
What is mucocutaenous leishmaniasis characterised by?
Disfiguring, destruction of mucous membranes.
110
What are the main symptoms of visceral leishmaniasis?
```
Fever
Splenomegaly
Uncomfortable spleen
Weight loss
Anaemia
Lymph nodes
Loss of appetite
Cough
Hepatomegaly
Oedema
Diarrhoea
Vomiting
Jaundice
```
111
Give an example of a parasite that causes visceral leishmaniasis.
Leishmania donovani.
112
How is visceral leishmaniasis diagnosed?
Clinical diagnosis based on case definition.
VL case definition: ‘a person who presents with fever of more than 2 weeks and enlarged spleen (splenomegaly) and/or enlarged lymph node (lymphadenopathy) or either of weight loss, anaemia, or leucopenia while living in a known VL endemic area or having travelled to an endemic area’.
113
What laboratory investigations can be performed to diagnose visceral leishmaniasis?
Parasite detection: definitive diagnosis of VL is made by visualisation of the amastigote form of the parasite by microscopic examination of aspirates from lymph nodes, bone marrow or spleen aspiration.
Antibody detection: direct agglutination test (DAT) and rK39 chromatographic test.
114
What is the first line treatment regimen for primary visceral leishmaniasis?
```
Sodium stibogluconate (SSG) or Meglumin antimoniate (monotherapy)- 20mg/kg/day for 30 days either intramuscular or slow intravenous infusion within 5 minutes.
Liposomal amphotericin B (LAmB, AmBisome)- 3-5mg/kg/day or intermittently for 5-7 doses over 6-10 days with a total dose of 30mg/kg used only in special cases (HIV coinfection, pregnancy and very sick patients).
Combination therapy: sodium stibogluconate (SSG) and paromomycin- not implemented yet.
```
115
What is the second line treatment regimen for primary visceral leishmaniasis?
Liposomal amphotericin B.
| Miltefosine (2-3mg/kg/day for 28 days).
116
What is post Kala-azar dermal leishmaniasis (PKDL)?
Occurs during or after treatment, after subclinical infection.
Lesions start on face, usually around mouth.
Lesions can become nodular.
Can spread to the trunk and limbs.
117
What are common signs of localised cutaneous leishmaniasis infection?
Large, irregular ulcer, surrounded by papular and crusted lesions which all contain parasites.
Crusted ulcers/ lesions- sign of healing.
118
Give 2 types leishmania parasite that cause localised cutaneous leishmaniasis.
L. tropica
| L. major
119
Give an example of a leishmania parasite that causes diffuse cutaneous leishmaniasis.
L. aethiopica
120
What are the features of diffuse cutaneous leishmaniasis?
Disseminated infection.
Multiple, nodular non-ulcerating lesions.
No spontaneous healing, relapses.
121
Give examples of leishmania parasites that cause mucocutaneous/mucosal leishmaniasis.
L. braziliensis
L. aethiopica
L. tropica
L. major
122
How is cutaneous leishmaniasis diagnosed?
```
Clinical diagnosis.
Parasitological diagnosis that involves microscopy and/or culture:
-FNA (fine needle aspiration)
-dermal scraping
-biopsy
Leishmanin skin test (for epidemiological study).
Serology.
Polymerase chain reaction (PCR)(AHRI).
```
123
What are the treatment options for cutaneous leishmaniasis?
Systemic treatment with sodium stibogluconate (SSG) or glucantime.
Intra-lesion administration of SSG.
Cryotherapy.
Miltefosine (compassionate).
124
What is the dosage, duration and outcome of systemic treatment of cutaneous leishmaniasis with sodium stibogluconate (SSG) or glucantime?
Dosage: 20mg/kg/day (SSG or glucantime).
Duration: a minimum of 28 days, usually longer.
Outcome: very poor prognosis for DCL and MCL.
125
What is the dosage, duration and outcome of treatment of cutaneous leishmaniasis with miltefosine (compassionate)?
Outcome: better prognosis than any of the other options, especially for DCL, but associated with relapse.
Dosage: 2-3mg/kg/day.
Duration: minimum of 28 days.
126
What are the main issues with visceral leishmaniasis and HIV coinfection?
HIV infection can lead to reactivation of latent Leishmania infection or to symptomatic VL at initial infection.
VL accelerates the onset of AIDS: increased HIV replication, cumulative immunosuppression.
Co-infected patients have lower T cell counts and lower BMI than patients with visceral leishmaniasis alone.
