5 - Parasites (06.03.2020) Flashcards
1
Q
Infection vs. Disease
A
Infection: invasion by and growth of
pathogenic microorganisms
within the body
Disease: 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, or unfavorable environmental factors; illness; sickness; ailment.
2
Q
What is a parasite?
A
organism living in or on the host and dependent on it for nutrition - causing damage
-> the parasite utilises the host to survive
3
Q
Endoparasites
A
Protozoa: amoeba, coccidiae, ciliate, flagellates
Metazoa: roundworms, flatworms, flukes
4
Q
What are the 2 different types of parasites?
A
- Endoparasites (Protozoa, Metazoa)
- Ectoparasites
5
Q
What are protozoa?
A
- single celled organisms
- Eukaryotes (genome within a nucleus, complex organelles in cytoplasm)
- Pathogenesis (mechanism of disease) varied
- Some have insect vectors (eg malaria)
- No eosinophilia
6
Q
What are metazoa?
A
Metazoa – Multicellular organisms (Helminths/worms)
- Free living, intermediate hosts and vectors
- Some just inhabit gut (geohelminths), other invade tissues
- Eosinophilia – if invade blood
7
Q
amoeba
A
the asymptomatic people keep the cycle going
cyst can remain viable for about 2 months
8
Q
How do you diagnose entamoeba histolytic infections?
A
- microscopically
- look for the eggs in a faeces sample
- wet mount
9
Q
Facts about Malaria
A
- children are most at risk
- In 2013, there were ~198 million cases of malaria, causing an estimated 584 000 deaths, mostly among African children (one child dies every 30 seconds).
- 2 hosts: human and female anopheles mosquito
10
Q
Symptoms of malaria
A
Fever, headache, chills, vomiting, muscle pain
Paroxysm (cycle in 4-8hrs)
Can appear as early as 7 days but the time between exposure and signs of illness can be as long as one year.
- 9 to 14 days for Plasmodium (P.) falciparum.
- 12 to 18 days for P. vivax and P. ovale.
- 18 to 40 days for P. malariae.
- 11 to 12 days for P. knowlesi.
11
Q
Complications of Malaria
A
Severe anemia (destruction of red cells; go into red cells and the red cells burst) Cerebral malaria (swelling of the brain,seizures, coma, death)
liver failure Shock Pulmonary edema abnormally low blood sugar kidney failure swelling and rupturing of the spleen
12
Q
Treatment of Malaria
A
Uncomplicated malaria:
chloroquine, Atovaquone-proguanil, Artemether-lumefantrine, quinine sulfate plus one of the following: Doxycycline, Tetracycline or Clindamycin Quinine sulfate, Mefloquine
Severe malaria:
Artemisinin-based combination therapy (ACT) is recommended for the treatment of P. falciparum malaria.
13
Q
Diagnosis of Malaria
A
- blood film, Giemsa stained (H&E) - people have to be trained to do this
- Rapid test: commercially available antigen detection tests: more expensive and less sensitive
14
Q
Toxoplasmaa
A
- Toxoplasmosis: mild disease in immunocompetent individuals: fever, swollen lymph nodes, headaches, sore throat.
- however, in pregnancy: toxoplasmosis poses serious danger for the Foetus)
- Immunocompromised patients may develop central nervous system disease, brain lesions, pneumonitis or retinochoroiditis among other risks.
- cats and mice are intermediate hosts
- infect warm blooded animals
- there are serological tests
- it is treatable
Infection:
• eating undercooked meat of animals harboring tissue cysts
• consuming food or water contaminated with cat feces
• by contaminated environmental samples
• blood transfusion
• organ transplantation
• transplacentally from mother to fetus.
15
Q
Flagellates examples and the disease they cause
A
Giardia lamblia (Giardiasis)
Disease: - symptoms dependent on dose - most people are asymptomatic - Acute symptoms: Diarrhea Greasy stools that tend to float Stomach or abdominal cramps Upset stomach or nausea/vomiting Dehydration (loss of fluids)
Diagnosis via stool sample, look for cysts and trophozoites (the 2 stages they are found in in humans)
Trichomonas
- STI
- symptoms in genital area in males and females however quite a proportion is asymptomatic
- most common non viral STI in UK
- infection enhances HIV transmission
16
Q
Giardia lamblia (Giardiasis)
A
- faeco-oral transmission
- Giardiasis: commonest, globally distributed, water-borne protozoal infection.
- Flagellated trophozooites attach by their suckers to surface of the duodenal or jejunal mucosa
- Ovoid cysts are able to survive standard chlorination procedures, filtration is required to exclude them from drinking water
17
Q
Giardia lamblia (Giardiasis) symptoms
A
- dependent on parasite dose
- Most people infected with Balantidium coli => no symptoms.
Acute symptoms: Diarrhea Greasy stools that tend to float Stomach or abdominal cramps Upset stomach or nausea/vomiting Dehydration (loss of fluids)
18
Q
Giardia lamblia (Giardiasis) Diagnosis
A
Stool examination. (cysts, trophozoites)
19
Q
Giardia lamblia (Giardiasis) - treatment
A
metronidazole/tinidazole
20
Q
Giardia lamblia (Giardiasis) - epidemiology
A
~2% of adults and 6% to 8% of children in developed countries worldwide; ~ 33% of people in developing countries
21
Q
Examples of flagellates:
A
- giardiasis
- trichomoniasis
- leishmania
22
Q
What is the difference between protozoa and metazoan?
A
Protozoa
- are single celled organisms (genome within a nucleus, complex organelles in cytoplasm)
- do not cause eosinophilia
Metazoa
- are multicellular organisms (helminths/worms)
- cause eosinophilia
23
Q
What are helminths?
A
Metozoa
24
Q
What is the difference between endo- and ectoparasites?
A
- endoparasites are inside the body
- ectoparasites affect the skin
25
What are the 4 main types of protozoa?
amoebae
flagellates
ciliates
coccidia
26
What are the 3 main types of metazoa/hemlinths?
flatworms
roundworms
flukes
27
Name examples of amoeba and the disease they cause?
- entamoeba dispar (commensal in gut)
- entamoeba histolytica
- 90% asymptomatic, in the 10% symptomatic:
- causes a range of symptoms varying from dysentery to amoebic liver disease
- can also affect the lungs, heart, skin, urinaray tract, brain
- transmitted by ingestion if mature cysts in food, water ir on hands contaminated with faeces.
- human - faeces - reingestion
28
Name examples of coccidia and the disease they cause
1. Plasmodium species - Malaria (headache, fever, chills, paroxysm, muscle pain, vomiting)
2. Toxoplasma - Taxoplasmosis (mild in immunocompetent people (swollen lymph nodes, fever, headache, sore throat) but dangerous in immunocompromised and in pregnancies were it can cause damage in the foetus)
3. Cryptosporidium - Diarrhoea, N&V, fever (mild disease in immunocompetent but can cause severe pathological changes in immunocompromised individuals); common in HIV+ presenting with diarrhoea; diagnose via stool sample, treat with fluids
29
What is a paroxysm?
a sudden recurrence or attack of a disease.
| "paroxysms of ataxia and shaking"
30
Give an example of a ciliate and the disease it causes
- Balantidium coli (Balantidiasis)
- Most people infected are asymptomatic.
- Immunocompromised patients may experience more severe signs and symptoms: persistent diarrhea, dysentery, abdominal pain, weight loss, nausea, and vomiting. If left untreated, perforation of the colon can occur.
- worldwide distribution
- reservoir hosts: pigs, rodents, primates
- diagnosis via stool sample
- treatable
31
Dysentery
- a type of gastroenteritis that results in diarrhea with blood.
- Other symptoms may include fever, abdominal pain, and a feeling of incomplete defecation.
- Complications may include dehydration.
- The cause of dysentery is usually Shigella, in which case it is known as shigellosis, or Entamoeba histolytica.
32
Trichomonas
- In women the organism is found in the vagina, urethra and paraurethral glands; in men infection is usually of the urethra.
Symptoms
- Females 10-50% are asymptomatic.=> vaginal discharge, vulval itching, dysuria, or offensive odour, but these are not specific for TV.
- Occasionally the presenting complaint is of low abdominal discomfort or vulval ulceration.
- Males 15 to 50% of men are asymptomatic => discharge and/or dysuria.
Complications: detrimental outcome on pregnancy and is associated with preterm delivery and low birth weight.
HIV
There is growing evidence that trichomonas infection may enhance HIV transmission and there may be an increased risk of TV infection in those that are HIV positive.
Diagnosis
Microscopy: Detection of motile trichomonads in swab/urine- Trichomonas Rapid Test
Treatment
metronidazole
33
Exmamples of roundworms (nematodes)
- ascaris
- hookworm
- Filaria
- Strongyloides
34
Ascariasis
Symptoms:
- often causes no symptoms.
- Infections with a large number of worms may cause abdominal pain or intestinal obstruction.
- Adults feed on the contents of the SI and in heavy infections, this may compound problems in malnourished individuals (especially children).
- Migration of larvae may cause localized reactions in various organs.
- Penetration of the larvae from capillaries into the lungs can lead to Loeffler's pneumonia, in which pools of blood and dead epithelial cells clog air spaces in the lungs.
- Resulting bacterial infections can be fatal.
- Diagnosis: stool sample
- Treatment: albendazole and mebendazole
35
Hookworm
Symptoms:
- IDA
- can be accompanied by cardiac symptoms
- GI/nutritional.metabolic symptoms may occur
- local skin manifestations
- respiratory symptoms can be observed during pulmonary migration of the larvae.
Diagnosis:
Stool sample
Treatment:
albenazole and mebendazole
36
Trichuris Trichiura - Whipworm
- a hookworm
- Small amounts of whipworms might not cause any symptoms.
- But if there are hundreds of worms, then you might have bloody diarrhea and anemia due to severe vitamin and iron loss.
- The worms leave open wounds, which cause inflammation of the intestinal wall.
- In some cases you might also develop rectal prolapse.
- Whipworm is one of the worms being used in helminthic therapy which helps against allergies and autoimmune diseases
- Diagnosis: Stool sample
- Treatment albendazole and mebendazole
37
Lymphatic filariasis:
- brugia malayi
- wucheria bancrofti
lymphatic obstruction (especially in the legs) can progress to elephantiasis – can also occur in arm, breast, scrotum
Diagnosis
The microfilariae are found mainly in the peripheral blood and can be found at peak amounts from 10 p.m. to 4 a.m. 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 a immunochromatic test (card) or ELISA
Treatment: albendazole and ivermectin
38
Filaria sybgroups
Filaria is a typeof roundworms which is a type of metazoan and includes:
- lymphatic filariasis
- loaloa (loasis)
39
Loaloa
- eye worm
- confined in Africa
- Infection with the parasite can also cause repeated episodes of itchy swellings of the body known as Calabar swellings
40
Types of flatworms (cestodes)
Flatoworms = cetstodes
Humans are the only definitive hosts for
- Taenia solium and T. asiatica – pig
- T. saginata – beef
41
Taenia
Symptoms:
- Most people: no symptoms or mild symptoms.
- Patients with T. saginata taeniasis often experience more symptoms (size of the worm up to 10m) that those with T. solium or T. asiatica (~3 m).
- 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
Diagnosis:
- Segment in stool or identifcation of eggs in stool
Treatment: praziquantel
Taenia solium - cysticercosis commonest cause of epilepsy worldwide
42
What is the commonest acquired cause of epilepsy worldwide?
Taenia solium - cysticercosis
-> in the brain can cause epilepsy
43
What is a type of fluke?
Schistosoma (mansion, haematobium, japonicum)
44
Schistosoma
Symptoms
- 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 anemia, malnutrition, and learning difficulties.
- After years of infection, the parasite can also damage the liver, intestine, lungs, and bladder.
Diagnosis:
stool or urine samples
Treatment
praziquantel (now MDA in schools)
45
Sarcoptes Scabei
Diagnostic
- Appearance of rash + presence of burrows
Treatment: Scabicides e.g. permethrin
46
Lice
Pediculus humanus capitis (head louse),
Pediculus humanus corporis (body louse, clothes louse), and
Pthirus pubis ("crab" louse, pubic louse)
Three stages: eggs, nymphs and adult
Transmission by direct contact
47
Name examples of ectoparasites
- Sarcoptes scabei
- Pediculus humanus capitis (head louse),
- Pediculus humanus corporis (body louse, clothes louse), and
- Pthirus pubis ("crab" louse, pubic louse)
48
What are the subtypes of leishmaniasis?
- mucosocutaneous
- visceral
- cutaneous
- diffuse cuteaneous
49
Visceral Leischmaniasis
- also called Kala azar - black fever
- most severe form, fatal if left untreated.
- Characterised by irregular fever, weight loss, swelling of liver and spleen, anaemia
- hepato and splenomegaly
- thrombocytopenia, anemia, leukopenia (immunosuppression, low CD4+, low CD8+)
- low BMI
RFs for development of clinical disease include:
• Malnutrition
• immune suppressive drugs
• HIV co-infections
VL case definition: “a person who presents with fever of more than two 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”.
50
Cutaneous leishmaniasis
- skin lesions on exposed body parts, often self-healing.
- Can create serious disability and scars.
- Immunity to reinfection
- Large, irregular ulcer; surrounded by papular and crusted
lesions which all contain parasites
51
Diffuse cutaneous leishmaniasis
- disseminated lesions,
- resembles leprosy (social problems, ostracised from society, women can't get married because of it) , difficult to treat, no spontaneous healing, frequent relapses
- Multiple, nodular non-ulcerating lesions
52
Mucocutaneous leishmaniasis
- disfiguring, destroys mucous membranes
- no spontaneous healing
- relapses
53
Kala Azar
- another name for visceral leishmaniasis
| - means black fever
54
Diagnosis of visceral leishmaniasis
VL case definition: “a person who presents with fever of more than two 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”.
Laboratory investigations
a) Parasite detection: definitive diagnosis of VL is made by visualization of the amastigote form of the parasite by
microscopic examination of aspirates from lymph nodes, bone marrow or spleen aspiration
b) Direct agglutination test (DAT) and rK39 chromatographic test
55
PKDL
Post - Kala-azar dermal Leishmaniasis
```
• frequent in Sudan and India
• in ~55% of patients in Sudan,
in 5-10% in India
• Occurs during or after treatment,
after sub-clinical infection
• Lesions start on face, usually around
mouth
• Lesions can become nodular
• PKDL can spread to the trunk and
limbs.
```
56
Take home messages
Parasitic infections - Take home messages:
Parasites infect much of the world’s population. Protozoal and heminthic infections are commonly referred to as “parasitic” infections and many of them belong to the group of neglected tropical diseases (NTDs).
A parasite is an organism that lives in (or on) its host, is dependent on the host for nutrition, often causing damage/disease. Infection vs disease: Infection is invasion by and growth of pathogenic microorganisms within the body. Disease is 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, or unfavorable environmental factors, illness, ailment. Protozoa are single celled eukaryotic organisms, their genome is contained within a nucleus and their cytoplasm contains complex organelles. The pathogenesis (mechanisms by which they cause disease) is varied and many are carried and transmitted by insect vectors (example: sand flies transmit Leishmania parasites; malaria is caused by mosquitos transmitting Plasmodium spp .
Vector-derived products can influence the host response
Protozoa can be divided into: Amoebae (pathogenic: Entamoebae histolytica; non pathogenic: Entamoeba dispar); Coccidia (Plasmodium spp., Toxoplasma, Cryptosporidium); Flagellates (Giarida; Trypanosoma, Leishmania, Trichomonas), Ciliates (Balantidium)
Helminths are complex multicellular organisms (metazoa), can be free living, transmitted by vectors and their life cycle often involves an intermediate host. Humans are the definitive host. Adult worms lay eggs or produce microfilariae but cannot themselves multiply in man – therefore they are frequently a cause of morbidity rather than mortality. Helminths (worms) can be divided into: Round worms (Nematodes), Flat worms (Cestodes) and Flukes (Trematodes).
57
Treatment of Leishmaniasis
sodium stibogluconate (SSG)
58
How is leishmaniasis spread?
Sandflies
59
Forms of Leishmania
* promastigote
* amastigote
Promastigotes
• Form of Leishmania within sand fly vector
• move in the direction of their flagellum
• Can be cultured
Amastigotes:
•Form of Leishmania within human or other vertebrate host’s cells (have resorbed their flagellum).
•They are no longer motile.
