28 Vector-borne infections - protozoa Flashcards
Which protozoa are transmitted by arthropods?
Malaria
Trypanosomiasis
Leishmaniasis
Plasmodium transmitted by female anopheles mosquito. Can also be transmitted vertically, and via blood transfusion
Approx 200 million cases/ year.
What are the names of plasmodium species?
Falciparum
Vivax
Malariae
Ovale
Knowlesi
What is geographic spread of these species of plasmodium?
Falciparum
Vivax
Malariae
Ovale
Knowlesi
Falciparum - tropics
Vivax - India/ SE Asia, SA, NE Africa
Malariae - tropics
Ovale - tropical Africa
Knowlesi - SE Asia
Which plasmodium species have tertian/ quartan fever?
tertian fever - every 3rd day
quartan fever - every 4th day
Tertian -
falciparum
vivax
ovale
Quartan -
malariae
tertian have asexual reproduction every 48 hours
quartan have asexual reproduction every 72 hours
Why is there a lack of P vivax in West Africa?
Plasmodium binds to red blood cell Duffy antigen
high prevalence of Duffy-negative people in West Africa
What conditions provide some protection from malaria>
Duffy antigen negative
sickle cell
beta-thalassaemia
G6PD
What is life cycle of plasmodium?
not in mosquito
Sporozoites from saliva injected into new host
Move from blood to liver. Two weeks later mature into pre-erythrocytic schizonts
hepatocyte ruptures, releasing merozoites. They enter RBC, where they undergo asexual reproduction. Some species (vivax/ ovale) can have latent hypnozoites
merozoite in RBC matures ring form, trophozoite, and schizont. Which ruptures and releases merozoites into bloodstream (completing cycle)
some merozoites undergo sexual stage, and produce gaemtocytes, which are taken up by new anopheles mosquito during feeding
What is life cycle of plasmodium?
in mosquito
gametocytes taken up by anopheles mosquito during feeding
once inside mosquito gut, gametocytes fertilise to form zygoe, which invades gut mucosa, and forms oocyst
oocyst produces produces sporozoites which are released and migrate to salivary glands of insect
What are symptoms of malaria?
Fever
headache
myalgia
can then develop multi-organ failure as parasatised red cells sequester in capillaries, causing endothelial dysfunction -
- cerebral disease
- jaundice
- anaemia
- hepatosplenomegaly
What is incubation period of malaria?
Between 6-40 days
usually 9-14 days most common time to present
Can present up to 6 months after travel event
What are clinical manifestations of severe malaria?
reduced GCS <11 convulsions respiratory distress prostration shock jaundice
What are biochemical manifestations of severe malaria?
abnormal coagulation anaemia hypoglycaemia <2.2 metabolic acidosis renal impairment parasitaemia >10%
People living in endemic plasmodium area, if they survive first infection, they develop immunity, and subsequent infections are not as severe.
If they move to UK, how long before they lose immunity?
approx 1 year out of endemic area will reduce immunity
How to diagnose malaria?
Lateral flow test - rapid antigen test
thick/ thin blood film - 3x sets (admission/ 24 hours/ 48 hours). If from endemic country, having parasite in bloodstream, does not mean it is always causing disease. If blood film negative, and high suspicion, may need biopsy of tissue
What is treatment of -
uncomplicated falciparum
complicated falciparum (>2% parasitaemia)
- PO co-artem (Artemetherelumefantrine (Riamet) is the drug of choice for 3 days
- dihydroartemisinin-piperaquine (Eurartesim) is an alternative for 3 days
Alternatives -
- Quinine and doxycycline 5-7 days
- atovaquone- proguanil (Malarone) 5-7 days
What is treatment of -
vivax/ ovale/ knowlesi/ malariae
co-artem or chloroquine
How to remove hypnozoites from liver? (vivax/ ovale)
Radical clearance
primaquine 14 days
contraindicate in G6PD deficiency
How to prevent/ reduce malaria spread?
Mass chemotherapy
insecticide treated nets
indoor residual spraying
removal of stagnant water
Suspected malaria. What details are important in travel history?
Must notify public health with positive cases
Country and area of travel.
Stopovers and other countries transited through.
Date of return.
Type of travel and activities while abroad — people returning from visiting friends and family in endemic areas are more at risk of malaria than tourists.
Prophylaxis taken
Vaccinations e.g YF
What are important differential diagnoses of malaria?
VHF - ebola/ marburg/ lassa
dengue
YF
JE
typhoid
leptospirosis
babesiosis - anaemia
African Trypanosomiasis
Could be simple bacterial sepsis. But if high risk/ travel, do not miss malaria
Which malaria patients need to be admitted?
Is suspected of having severe or complicated malaria.
Is suspected of having falciparum malaria.
Is a pregnant woman.
Is a child.
Is older than 65 years of age.
Non-falciparum malaria can be managed as outpatient, if observed for 8 hours after starting treatment
What is treatment of -
complicated falciparum (severe)
> 2% parasitaemia indicates IV therapy required
- IV artesunate until manage oral/ parasite count reduced
- if not available, start IV quinine until artesunate sourced
- manage in HDU/ ITU
What is treatment of malaria in pregnancy?
Increases risk of miscarriage
Co-artem 2nd/3rd trimester
Quinine + clindamicin all 3 trimesters
Where is resistance emerging in malaria treatment?
SE Asia
SA
chloroquine resistance
What are options for malaria prophylaxis?
Doxycycline
Mefloquine
Atovaquone-proguanil (malarone)
Chloroquine - widespread resistance
What are options for malaria prophylaxis in pregnancy?
Advise avoid travel to high risk area
Mefloquine - can be used all trimesters, although less data in first trimester
Atovaquone-proguanil - lack of data, avoid if possible
Doxycycline - definitely avoid first trimester. Can use in 2nd/3rd if very high risk of malaria outweighs contraindications
What do these terms mean?
causal prophylaxis
suppressive prophylaxis
Causal prophylaxis - active against liver stage (not hyponozoites), preventing release and infection of RBC. Take for 7 days after returning. Atovaquone-proguanil
Suppressive prophylaxis - active against red blood cell stages. Take for 28 days after returning. Chloroquine, mefloquine, doxycycline
What are contraindications to chloroquine?
If on hydroxychloroquine for rheumatic disease, can continue hydroxychloroquine without swapping
If resistance present
epilepsy
psoriasis
myasthenia gravis
amiodarone interaction
What are contraindications to doxycycline?
pregnancy
children <12
as acidic preparation, can cause severe oesophagitis/ gastritis
When is emergence malaria standby treatment provided for travellers?
What are drug options? including pregnancy
If going to be >24 hours away from medical assistance
Artemther-lumefatrine or
atovaquone-proguanil or
quinine + clindamicin (pregnancy)
Female on malaria prophylaxis, planning to become pregnant. How long should anti-malarials be stopped for?
Mefloquine
Doxycycline
Atovaquone-proguanil
Mefloquine: 3 months
Doxycycline: 1 week
Atovaquone/proguanil: 2 weeks
Patient with epilepsy travelling to malaria country. What are options?
Doxycycline or
atovaquone-proguanil
mefloquine/ chloroquine unsuitable
Patient with G6PD deficiency travelling to malaria country. What are options?
Avoid choroquine
doxycycline/ mefloquine/ atovaquone-proguanil
When must these malaria prophlaxis drugs be started prior to travel?
Doxycycline
atovaquno-proguanil
chloroquine
mefloquine
Doxycycline or atovaquone-proguanil - 2 days before
Chloroquine - 1 week before
mefloquine - 2-3 weeks before (to ensure tolerance).
What are three species of trypanosoma?
African trypanosomiasis -
Trypanosoma brucei gambiense (West) - 97% African cases
Trypanosoma brucei rhodesiense (East)
South American trypanosomiasis -
Trypanosoma cruzi
African trypanosomiasis
what is vector?
tsetse fly
reservoir of trypanosomes in wildlife and cattle
flies feed during daylight hours
What is clinical presentation of african trypanosomiasis?
following insect bite, widespread lymphadenopathy occurs. Enlarged cervical lymph nodes is known as Winterbottom’s sign
fever splenomegaly myocardial involvement headache behavioural change - sleeping sickness, which leads to death
Even after treatment, can be left with permanent neurological disability
How does african trypanosomiasis evade host immune system?
Antigenic variation - switches between 900 different antigens on surface
How to diagnose african trypanosomiasis?
microscopy of blood/ CSF/ lymph node for parasites
antitrypanosomal antibody - mostly only useful for screening populations
What is treatment of african trypanosomiasis
Suramin IV followed by
melarsoprol IV if CNS involvement
West African -
Pentamidine IV
Nifurtimox orally + eflornithine IV if CNS involvement
What is vector of South American trypanosomiasis?
reduviid bug - feeds on host, and excretes faeces. Host rubs trypanosomes into wound/ mucosa
inhabit poor housing in rural areas
most mammals can act as reservoir for infection
can also be transmitted via contaminated food, blood donors
What are symptoms of South American trypanosomiasis?
Nodular lesion at inoculation site
Swelling eyelid - Romanas sign
fever
GI - megaoesophagus/ megacolon
Cardiac - myocarditis
how to diagnose South American trypanosomiasis?
Blood film
PCR
serology
can perform PCR on reduviid bug stool
What is treatment for South American trypanosomiasis?
benznidazole oral or
nifurtimox oral
What is vector of leishmaniasis?
Leishmaniasis either multiplies in skin (cutaenous) or in spleen/ liver/ bone marrow (visceral leishmaniasis)
sandflies
dogs can act as important reservoirs
Which species cause cutaneous leishmaniasis?
L major
L tropica
L mexicana
L braziliensis
Which species cause visceral leishmaniasis?
also known as kala-azar
L donovani
L infantum
L chagasi
Visceral leishmaniasis is fatal in 90% cases
What are symptoms?
Develops slowly
fever
weight loss
hepatosplenomegalt
What are symptoms of cutaneous leishmaniasis?
Small papule develops into large ulcer. Can then heal with considerable scarring
How to diagnose leishmaniasis?
Microscopy of splenic aspirate/ bone marrow/ skin
PCR
serology
What is treatment of cutaneous leishmaniasis?
local injection of sodium stibogluconate
What is treatment of visceral leishmaniasis?
amphotericin B IV or
sodium stibogluconate IV
