Parasitic Infections Flashcards
Define Infection vs. Disease•
Infection:
invasion by and growth of pathogenic microorganisms
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 unfavourable environmental factors; illness; sickness; ailment.
Define Parasite
Organism living in/on a host
AND
is dependent on the host’s function – causing damage.
Two subtypes of parasites?
Endoparasites:
• Protozoa
– amoeba, coccidia, ciliate, flagellates
• Metazoa (helminths)
– roundworms, flatworms, flukes
Ectoparasites
Explain Protozoa and facts about it
Protozoa – single-celled organisms:
- Eukaryotic organisms – genome is within a nucleus, complex organelles
- Causes of pathogenesis varies
- Some have insect vectors
- NO eosinophilia
Explain Metazoa and facts about it
Metazoa – multi-cellular organisms:
- Free living
- Have intermediate hosts and vectors
- Some just inhabit the gut (geo-helminths) whilst other invade tissues
- Eosinophilia if they invade the blood
Endoparasites - protozoa examples?
” A Cell Causing Fever”
A - Amoeba
C - Coccidiae
C - Ciliates
F - Flagellates
Explain the “A” of Protozoa - its different forms and how it causes infections
Amoeba
Genus: Entamoeba
• Entamoeba histolytica
- infects 10% of population
• Entamoeba dispar
- NORMAL COMMENSAL of the GI tract
Infection occurs by:
• INGESTION of MATURE CYSTS in food or water OR on hands
Epidemiology of “A” of Protozoa
Amoeba
3rd most common cause of death
• after schistosomiasis & malaria
90% of infections are ASYMPTOMATIC
Incubation period:
• can be short as 7 days
BUT
• upto 4 months as tissue invasion occurs during first 4 months
Explain “A” of Protozoa - life cycle, symptoms, diagonsis & treatment
Life cycle:
• HUMANS ONLY reservoir
• Cysts enter S.I and release parasites (trophozoites) = invade L.I epithelial cells = cause ULCERS
• Infection spreads via. venous system
Diagnosis:
• wet mount - microscopy of cysts
Treatment:
• Nitroimidazole derivatives, parmomycine or diloxanide furoate
Explain the first “C” of Protozoa and state what its organisms and associated diseases are briefly
Coccidia
Organisms & Associated Disease:
Plasmodium species
– malaria
Toxoplasma
– toxoplasmosis
– mild disease in immunocompromised – major for pregnancy!
Cryptosporidium
– diarrhoea.
Explain the FIRST organism of Coccidia and the related information: Facts Symptoms Treatments Diagnosis
PLASMODIUM - malaria
Facts:
• 2 hosts include humans and female anopheles’ mosquito.
• 2 stages in humans – liver and blood stages
Symptoms:
– fever, headache, chills, emesis, myalgia
Complications:
– severe anaemia (due to RBC destruction)
– cerebral malaria (brain oedema = coma)
Treatments
– uncomplicated malaria = Chloroquine
– severe malaria = ACT (combination)
Diagnosis:
• blood film
• antigen detection tests
Explain the SECOND organism of Coccidia and the related information
TOXOPLASMA - toxoplasmosis
Toxoplasmosis gondii
Hosts:
• infected food (warm-blooded animals with cysts or cat faeces contamination)
Transmission: • blood transfusion • faeco-oral • organ transplantation • trans-placentally to foetus
Normally asymptomatic:
• problematic in pregnancy/immunocompromising
Explain the THIRD organism of Coccidia and the related information:
Symptoms
Diagnosis
Treatment
CRYPTOSPORIDIUM - diarrhoea
Symptoms:
• diarrhoea, fever, nausea, emesis
• Very common in HIV patients
Diagnosis:
– stool examination
Treatment:
– fluid rehydration
Explain the second "C" of Protozoa and state what: Organisms Hosts Symptoms Diagnosis
CILIATES
Organisms:
– Balantidum coli –> balantidiasis
Reservoir hosts:
– pigs, rodents, primates (infects people worldwide)
• transmission via. faeco-oral route
Symptoms:
Most asymptomatic
Immunocompromised people – persistent diarrhoea, dysentery, abdominal pain, weight loss, nausea, emesis; all leading to perforation of the colon
Diagnosis:
• stool examination
Explain the “F” of Protozoa and state what Organisms are generally associated with it
FLAGELLETES
Organisms:
Giardia lamblia –> Giardiasis
– symptoms: diarrhoea
Trichomonas
Leishmania
– sand fly vector
– 4 main types of Leishmania
Explain the organism Trichomonas of Flagellates
Transmitted sexually
Symptoms:
• Females
– 10-50% asymptomatic
– vaginal discharge, vulval itching, dysuria
• Males
– 15-50% asymptomatic
– discharge and/or dysuria
May enhance HIV risk and is very bad for pregnant women.
Diagnosis and treatment:
– microscopy and metronidazole.
What makes up Endoparasites - Metazoa?
Worms!
• roundworms
• flatworms
• flukes
What are some facts about the life cycles of metazoa/helmiths
Cycles may involve insect vectors and intermediate hosts.
for most, humans are the DEFINITIVE host – a few are zoonoses (acquired from animals)
o Adult worms can NOT multiply in man
– the number of adults is related to the infection
o A large burden is found in school-aged children which has a massive effect on their development
Examples of the diseases caused by Metazoa?
Roundworms/Nematodes • Ascaris • Hookworm • Filaria • Strongyloides
Flatworms/Cestodes
• Taenia (tapeworms)
Flukes/Trematodes
• Schistosoma
Explain the "A" of Roundworms/Nematodes stating: Life Cycle Symptoms Diagnosis Treatment
ASCHARIASIS (most common infection worldwide)
Life cycle:
Live in the S.I and eggs are passed with faeces
After infective eggs are swallowed, larvae hatch and invade the intestinal mucosa
They are carried via the portal and then systemic circulation to the lungs
The larvae mature in the lungs, penetrates the alveolar walls, ascends and is then swallowed.
When they reach the S.I , they develop into adults (live for 1-2 years)
Symptoms:
• often asymptomatic BUT can cause abdominal pain or intestinal obstruction
Adults feed on SI contents –> malnourishment
Penetration of lungs can cause Loeffler’s pneumonia – pools of blood clog the lungs
Diagnosis:
– stool examination
Treatment:
– albendazole or mebendazole
Explain the "H" of Roundworms/Nematodes stating: Life Cycle Symptoms Diagnosis Treatment
HOOKWORM
• cause iron-deficient anaemia AS it causes localised bleeding
Life cycle:
Larvae are carried through the circulatory system to the heart and then lungs.
Penetrate the alveoli and ascend to be swallowed and reach the SI to mature.
In the SI, they attach to the lumen and cause localised bleeding
Symptoms: – iron deficient anaemia – cardiac complications – local skin manifestations – respiratory symptoms
Diagnosis:
– stool examination
Treatment:
– albendazole or mebendazole
Explain the "F" of Roundworms/Nematodes stating: Main types Symptoms Diagnosis Treatment
FILARIA, Lymphatic filariasis
2 main types:
(1) Brugia malayi
(2) Wucheria bancrofti
Symptoms:
– cause ELEPHANTIASIS when they block the lymphatic systems
– Microfilariae are found in peripheral blood.
during the day, they are present in deep veins and at night they migrate to the peripheral circulation
Diagnosis:
– blood smear OR antigen detection with an immunochromatic test (CARD) OR ELISA
Explain the “L” of Roundworms/Nematodes stating:
Life Cycle
Symptoms
LOIASIS - Loa Loa
o These can get into the eye
o Confined to Africa
o Adults can live for 4-12 years
Life cycle:
Females migrate through the SC tissues and may cross the front of the eye
Microfilariae circulate in the blood from where it can be picked up by the Chrysops
In the gut of the fly, the larvae mature into the infective third stage larvae
These larvae infect the next host when chrysops takes a blood meal and they mature into adults.
Explain the example of Flatworms/Cestodes, giving: Hosts Symptoms Diagnosis Treatment
Tapeworm: TAENIA
HUMANS are the ONLY DEFINITIVE HOSTS for:
Taenia solium, Taenia asiatica – PIG.
Taenia saginata – BEEF
Symptoms
– most people are asymptomatic
T. saginata often experience more symptoms – abdominal pain, loss of appetite, weight loss, upset stomach.
T. solium causes cysticercosis – most common cause of acquired EPILEPSY worldwide
Diagnosis:
– tapeworm segments in stool OR identification of eggs in stool
Treatment:
– Praziquantel
Explain the example of Flukes/Trematodes, giving the: Main Types Life Cycle Symptoms Diagnosis Treatment
SCHISTOSOMIASIS
3 main types:
Schistosoma mansoni
(Eggs to SI)
Schistosoma haematobium
(Eggs to bladder and ureter)
Schistosoma japonicum
(Eggs to SI)
Life cycle:
Eggs eliminated in water via faeces or urine
These hatch and release miricidia, which penetrates the snail. The snails release cercariae that penetrate the skin.
They then migrate to different tissues and transform into adults and females which reside in venules
Eggs move progressively towards the lumen of the SI (mansoni and japnicum) or the bladder and ureters (haematobium)
Symptoms:
Days – rash/itchy skin – most people are asymptomatic early on.
Months – fever, chills, cough, myalgia
• Repeated infection in children can cause anaemia, malnutrition and learning difficulties
Diagnosis:
– stool or urine examination.
Treatment:
– praziquantel
Example of Ectoparasites?
Scabies
• Sarcoptes Scabei
Lice
What are symptoms and treatment for Scabies?
Symptoms:
• rash
• burrows presence
Treatment:
• Scabicides
What are the different types of Lice and its life cycle?
Types of lice:
Pediculus humanis corporis
– body louse
Pediculus humanis capitis
– head louse
Pthirus pubis
– crab louse of pubic area
Life cycle:
o Exist in 3 stages – eggs, nymphs, adults.
o Transmission is by direct contact
What are different forms of Leishmania Protozoan?
Leishmania - example of a Flagellates (Protazoa)
Promastigote
• transmitted by sand fly
Amastigote
• IC in host
What are the major forms on leishamaniases disease?
Visceral leishmaniasis (kala azar) - most severe: Most = subclinical, but when symptomatic = very dangerous Fever, hepatosplenomegaly, anaemia, fatal if left uncured
Cutaneous leishmaniasis:
Skin lesions, often self-healing – but can create serious disability and scars
• May be localised, diffuse or mucocutaneous
Localised Cutaneous
– “crust” development is representative of healing
Recovery from localised form –> resistance: basis for a vaccine
Diffuse Cutaneous
resembles leprosy and difficult to treat
causes nodular non-ulcerating lesions
Mucocutaneous
disfiguring - as destroys mucous membranes
What is meant by Vector?
An organism that transmits a disease or parasite from one organism to another
Examples of vestors?
Snail
– transmits schistosomiasis (Fluke, Metazoa, endoparasite)
Female anopheles’ mosquito
– transmits malaria (Coccidia, protozoa, endoparasite)
Chrysops
– transmits Loiasis (Roundworm, Metazoa, endoparasite).
