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Microbiology And Immunology > Pathogenesis of parasitic infections > Flashcards

Pathogenesis of parasitic infections Flashcards

1
Q

What is the parasite of chagas disease called and describe briefly the main principles of its life cycle?

A
  • Trypansoma cruzi - protozoa
  • Basic life cycle:
    1. Infected bug and defecates at site
    1. Parasite or person leads to transmissions by invading cells at wound site
    1. These transform into amstigotes
    1. These then mutliple into tryopmatsigotes and enter blood
      Can also enter via ingestion where it will multiply within the intestine
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2
Q

State the 3 phases of chagas disease distinguishing the key features between them?

A
    1. Acute: Incubation 1-2 wks after bite! Up to months after transfusion, Trypanosomes in blood
    1. Chronic ‘indeterminate’: Lifelong infection, Generally trypanosomes not detectable but often positive for parasite DNA, Seropositive - presence of detectable levels of a specific marker within the serum, 60-70% who become infected will develop indeterminate chagas disease, Normal ECG and X rays
    1. ‘Determinate’ Chronic disease: Seropositive, 30-40% of infected will develop chronic 10-30 years after infection, 5-10% develop chronic Chagas immediately after acute disease
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3
Q

State the key clinical symptoms found in acute chagas with symptoms duration and diagnosis rate?

A
  • Occurs within 3 weeks
  • Generally mild or asymptomatic: Local swelling (Romaña), Nodule or chagoma, Fever, Anorexia, Lymphadenopathy - a disease affecting the lymph nodes.
  • 1-2% diagnosed with acute chagas due to mild symptoms which are common with other illnesses
  • Symptoms last 8-10 wks
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4
Q

What are rare clinical symptoms of acute chagas and who do they primarily affect?

A
  • Primarily affect young and immunosuppressed individuals
  • Can lead to:
  • Hepatopsplenomegaly
  • Acute myocarditis
  • Meningoencephalitis
  • Fatality <5% of symptomatic
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5
Q

What are the main organs affected by chronic chagas disease?

A

Heart and intestinal tract

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6
Q

Describe the cardiac impact from chronic chagas?

A
  1. Arrhythmia can occur: Protozoa invades ANS conduction fibres, Damages conduction system of heart via inflammation and fibrosis
  2. Thinning of heart muscle: Damage to heart muscle, Heart muscle becomes tinner + distended due to cardiomyopathy -> Enlarged heart, Insufficiency of heart valves - Aneurysm of apex of left ventricle
  3. Can lead to heart failure
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7
Q

Describe the digestive impact from chronic chagas?

A
  • Develops in 10-15% of patients with chronic infections
  • Esophagus, rectum, and sigmoid colon most affected
  • Ineffective peristalsis occus due to loss of ANS - accumulation of faeces
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8
Q

What frequent clinical symptoms arises from chronic chagas and state the complications of it?

A

Megacolon - Presentation: Constipation
• Complications: Faecaloma, Obstruction, Sigmoid volvulus! Ulceration, Perforation

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9
Q

State the acute chagas pathogenesis

A
  • Tissue damage caused by inflammatory response to parasite in nests of amastigotes in cardiac, skeletal, and smooth muscle
  • Parasite killing by antibodies, activated innate immune response and Th1 pro- inflammatory cytokines.
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10
Q

State the pathogenesis of indeterminate chronic chagas disease

A

Regulatory immune response characterized by IL-10 and IL-17

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11
Q

State the pathogenesis of chronic chagas disease

A
  • Chronic inflammatory response to persistent parasites in muscle and nerve cells
  • Autoimmune mechanisms
  • May vary by parasite strain and tissue tropism
  • Predominance of Th1 cytokines and CD8+ T cells
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12
Q

State the 3 main species of schistosomiasis?

A
  • Schistosoma mansoni
  • S.haematobium
  • S.japonicum
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13
Q

Describe the life cycle of schistosomiasis?

A

VD

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14
Q

What dermal disorder can arise from schistosomiasis and how?

A
  • Cercarial dermatitis - exposure to cercariae from animal or bird schistosomes - Causes rash-like lesions
  • Requires pre-sensitization
  • Allergic-type reaction
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15
Q

What is the key feature of the immune response against schistosomiasis and what can it result in?

A
  • Granuloma formation
  • Originally eggs live in the venous system, but backflow can occur causing eggs to move into the liver.
  • Here eggs can become organised in granulomas - leads to inflammation and damage to tissue - Followed by repair and fibrosis
  • Overtime Repeated insults and tissue repair leads to fibrosis and organ damage to liver
  • Extra info: The eggs formed in the mesentery are pushed through the capillaries, through the intestinal and mucosa and are then excreted.
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16
Q

How can hepato-intestinal schistomsomiasis arise?

A
  • Infections with S.mansoni and S. japonicum
  • Pathology caused by immune response to eggs (granulosa formation)
  • Typically leads to liver damage
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17
Q

What is the first clinical sign of urinary schistosomiasis?

A

Haematuria - Presence of blood within the urine

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18
Q

Describe the bladder pathology from Urinary schistosomiasis?

A

Repeated episodes of US within the bladder will cause inflammation eventually causing neoplastic chances to occur with the bladder mucosa - Carcinoma can occur

19
Q

Describe onchocerciasis, what it is caused by, its vector and how its transmitted?

A
  • Major blinding disease
  • Caused by filarial parasite (Onchocercavolvulus)
  • Transmitted by blackflies
  • Vector: Simulim
20
Q

Describe the life cycle of Onchocerciasis?

A
  • bites + invades through the skin
21
Q

Describe the pathology of Onschocerciasis?

A
  • Repeated episodes of inflammation to presence of microfilariae (the minute larva of a filaria) leads to permanent damage and scarring in skin and eyes
22
Q

Describe the clinical symptoms of the Onchocerciasis?

A
  • Onchocercal nodules
  • Skin disease
  • Eye disease
23
Q

State 3 examples of skin disease that can arise from
Onchocerciasis?

A
  • Acute papular onchodermatitis
  • Chronic onchodermatitis
  • Sowda
24
Q

State examples of anterior and posterior segment eye diseases from Onchocerciasis?

A
  • Anterior segment: Punctate keratitis! Acute iridocyclitis! Sclerosing keratitis
  • Posterior segment: Optic neuritis/atrophy, Chorioretinopathy
25
Q

Describe the immunopathogenesis of onchocerciasis?

A
  • Acute will actively forms antibodies against it
  • Overtime suppression of immune response against infection due to continious infection-> regulatory environment
  • AAM = Alternatively activated macrophages
26
Q

Explain the immunopathogenesis of onchocerciasis?

A
  • Initially primary response will be a strong immune response, but with repeated infections the immune response is also causing pathology
  • So immune system has to switch off when infection occurs otherwise it will kill you
27
Q

What are ticks?

A
  • Ectoparasites which cause tick bites in your skin and release a toxin into the skin which blocks motor fibres
  • Can cause mechanical injury at site
  • Tick paralysis can occur if tick not removed from site due to toxin long term
28
Q

State the two types of ticks and what they can transmit?

A
  • Hard ticks: transmit are typhus, encephalitis, fevers, tick paralysis (rapid onset of muscular paralysis due to failure of ACh liberation from NMJ), tularaemia and human babesiosis.
  • Soft ticks: transmit Q fever and relapsing fever.
29
Q

What disease does ticks normally cause?

A

Lyme disease

30
Q

Describe head lice?

A
  • Head lice
  • Suck blood from scalp & lay eggs on hair
  • Common & easily spread by close contact, sharing of combs, brushes, hats etc
31
Q

Describe body lice?

A
  • Body lice
  • Suck blood from body & lay eggs on clothing
  • Uncommon & spread by bodily contact, sharing of clothing or bedding
  • Vector diseases (epidemic typhus, trench fever, relapsing fever)
32
Q

How can lice be transmitted or be affected?

A
  • Lousiness related to sanitation
  • Crowded conditions
  • Long periods without bathing or changing clothes
33
Q

Describe the pthiridae lice, where its found and how it spreads?

A
  • 2 important families (attack humans)
  • Pthiridae (crab lice, public lice):
  • Broad, flat lice that appear crablike
  • Mid & hind legs are stout with very large claws
  • Abdominal segments have distinct lateral lobes
  • Single species (Pthirus pubus)
    confined to human pubic region
    • Bites cause irritation & typical rash
    Spread by close body contact (usually sex)
    • No diseases
34
Q

What is the alternative name for botfly known as and describe how they work?

A
  • Dermatobia hominis
  • Botflies are parasitic organisms and some lay their eggs in mammals. Like human mammals. One type of botfly latches onto mosquitoes mid-flight, attaching their eggs to the mosquitoes’ stomachs. Then, when a mosquito lands on a human’s skin, the eggs burrow into the tiny wound left by the mosquito bite
  • Eventually, these eggs turn into larvae and will dig their way out from underneath the skin
35
Q

State drugs used to control protozoa infections?

A
  • Tinidazole
  • Metronidazole
  • Nitazoxanide
  • Benznidazole
  • Heavy metals (meglumine antimoniate)
36
Q

State drugs used to control helminths infections?

A
  • Albendazole/ mebendazole
  • Praziquantel
  • Ivermectin
  • Diethylcarbamazine
  • Pyrantel
37
Q

State drugs used to control ectoparasites infections?

A
  • Ivermectin
  • Benzyl malathion lotions
38
Q

Describe 3 forms of control of parasitic infections without drugs?

A

Behaviour, environmental interventions, poverty reduction

39
Q

In terms of behaviour, how can we control parasite infections?

A
  • Education
  • Hand washing and hygiene behaviours
40
Q

In terms of environmental interventions, how can we control parasite infections?

A
  • Spraying of residual insecticides for household vectors
  • Mosquito nets for malaria
  • Improved housing
  • Sewage disposal and potable water
  • Drainage of swamps
41
Q

In terms of poverty reductions, how can we control parasite infections?

A

Micro-financing, etc

42
Q

Treatment of parasite infections
Describe the frequency and duration of treatment given areas with parasite infections (PART 1)

A
  • For many parasite infections in an endemic settings, treatment must be given periodically over long periods of time because re-infections are rapid or because the treatment kills larval rather than adult stages
  • A single dose of albendazole is given to high risk groups such as schoolchildren up to every 4 months to control STH infections.
43
Q

Treatment of parasite infections
Describe the frequency and duration of treatment given areas with parasite infections (PART 2)

A
  • A single dose of ivermectin is given to endemic communities (mass drug administration) every 6 or 12 months to control onchocerciasis
  • A single dose of praziquantel is given to endemic communities (mass drug administration) every 6 or 12 months to control schistosomiasis

Microbiology And Immunology (32 decks)

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