Zoonotic / Parasites / Protozoa Flashcards
What is the bacteria behind Lyme disease?
Borrelia Burgdorfei
What are the early features of Lyme disease?
Early features (within 30 days)
- Erythema migrans
‘bulls-eye’ rash is typically at the site of the tick bite
headache
lethargy
fever
arthralgia
How does erythema migrains develop in Lyme disease?
Typically develops 1-4 weeks after the initial bite
more than 5 cm in diameter and slowly increases in size
present in around 80% of patients.
systemic features
What are later features of Lyme disease?
Heart block
Perimyocarditis
Facial nerve palsy
Radicular pain
Meningitis
How is Lyme disease diagnosed?
Can be diagnosed clinically if erythema migrans is present
First line investigation: enzyme-linked immunosorbent assay (ELISA) antibodies to Borrelia burgdorferi are the first-line test
What should you do if you Lyme ELISA is negative, but still consider possible diagnosis?
Repeat ELISA in 4-6 weeks time
If over 12 weeks an immunoblot should one completed
How should Lyme disease be treated?
- Doxycycline
- Amoxicillin (as an alternative - i.e. if pregnant)
Ceftriaxone if disseminated disease
What is a Jarisch-Herxheimer reaction?
After initiating therapy: fever, rash, tachycardia after first dose of antibiotic (more commonly seen in syphilis, another spirochaetal disease)
What are the two forms of trypanosomiasis?
African trypanosomiasis (sleeping disease)
American trypanosomiasis ( Chagas disease)
How does trypanosomiasis spread?
Tsetse fly
What are that cause of African trypanosomiasis?
Trypanosoma gambiense in West Africa
Trypanosoma rhodesiense in East Africa
What are the features of African trypanosomiasis (sleeping disease) ?
Trypanosoma chancre - painless subcutaneous nodule at site of infection
intermittent fever
Enlargement of posterior cervical lymph nodes
Later:
central nervous system involvement e.g. somnolence, headaches, mood changes, meningoencephalitis
How do you treat African trypanosomiasis?
early disease: IV pentamidine or suramin
later disease or central nervous system involvement: IV melarsoprol
What is the cause of chagas disease?
Trypanosoma cruzi.
What is the classification of trypanosomiasis?
trypanosomiasis is a protozia
How does Chagas disease present?
95% asymptomatic in acute early phase
Chagoma - erythematous nodule at site of infection
periorbital oedema
Myocarditis –> dilated cardiomyopathy (chronic)
GI: Megaoesphagus, megacolon
causing dysphagia and constipation
What is the treatment of Chagas disease?
Acute:
azole or nitroderivatives such as benznidazole or nifurtimox
chronic disease management involves treating the complications
How should Malaria be investigated?
Thick blood film - most sensitive for diagnosis
Thin blood film - diagnosis of species
What other features do you seen on a blood count of malaria?
Thrombocythaemia is characteristic
Normochromic normocytic anaemia
Normal white cell count
Reticulocytosis
What type of organism is toxoplasmoisis Gondi?
intracellular protozoan
How do you manage toxoplasmosis in immunocompetent patients?
Does not require treatment unless severe infection / immunocompromised
What is the treatment of toxoplasmosis? And when do you treat?
pyrimethamine plus sulphadiazine for at least 6 weeks
Congenital toxoplasmosis. How is it acquire? Presentation?
Congenital toxoplasmosis is due to transplacental spread from the mother. It causes a variety of effects to the unborn child including
Neurological damage:
- cerebral calcification
- hydrocephalus
- chorioretinitis
Ophthalmic damage
- retinopathy
- cataracts
What are the features of severe malaria falciparum ?
Schizonts on a blood film
Parasitaemia > 2%
Hypoglycaemia
Acidosis
Temperature > 39 °C
Severe anaemia
What are the complications of malaria?
Cerebral malaria: seizures, coma
Acute renal failure: blackwater fever, Secondary to intravascular haemolysis, mechanism unknown
Acute respiratory distress syndrome (ARDS)
Hypoglycaemia
Disseminated intravascular coagulation (DIC)
What is the treatment of malaria falciparum?
First line therapy:
Artemisinin + combination
Artemether plus lumefantrine
Artesunate plus amodiaquine
Artesunate plus mefloquine
Artesunate plus sulfadoxine-pyrimethamine
Dihydroartemisinin plus piperaquine
What is the treatment of severe malaria falciparum?
Intravenous artesunate
How are people infected with Strongyloides stercoralis?
Infected larvae in soil gain access by penetrating the skin
What are the features of Strongyloides stercoralis?
Diarrhoea
Abdominal pain/bloating
Papulovesicular lesions on soles of feet and buttocks
Larva currens: pruritic, linear, urticarial rash
If the larvae migrate to the lungs a pneumonitis similar to Loeffler’s syndrome may be triggered
What is the shape of Strongyloides larvae?
rhabditiform larvae.
What is the treatment for strongyloides?
- Ivermectin (best)
- Albendazole
Ivermectin is a single dose agent
Albendazole require multiple doses
What causes”thread worm” and what are its features?
Enterobius vermicularis / Pin worm
Perianal itching
Assymtomatic in 90%
How is thread worm investigated?
sticky plastic tape to the perianal area and sending it to the laboratory for microscopy to see the eggs
How do you treat thread worm ?
Bendazoles
What causes hookworm?
Ancylostoma duodenale
Necator americanus
What are the features of hookworm?
Larvae penetrate skin of feet; gastrointestinal infection → anaemia
Thin-shelled ova
What are the features of loa loa?
auses red itchy swellings below the skin called ‘Calabar swellings’, may be observed when crossing conjunctivae
How is loa loa transmitted?
Deer fly
Mango fly
What is the treatment of loa loa?
Diethylcarbamazine
What are the features of trichnerella spirals?
Features include fever, periorbital oedema and myositis (larvae encyst in muscle)
How is trichnerella spiralis treated?
Bendazoles
What is river blindness? How is it spread?
Onchocerca volvulus
Spread by female black flies
How is onchocera volvulus treated?
Ivermeticin
rIVERblindness
= Ivermeticin
What are the features of Amoebiasis?
Profuse blood diarrhoea
- there is a long incubation period
How is amoebiasis tested?
“Hot stool test” - test for stool within 15 minutes
stool microscopy may show trophozoites if examined within 15 minutes or kept warm (known as a ‘hot stool’) - otherwise moves into cyst form and not easily diagnosed
How is amoebiasis treated?
Metronidazole
invasive amoebiasis should be followed by a luminal amoebicide to eradicate the cystic stage which is resistant to metronidazole and tinidazole/diloxanide furoate (which are used against the invasive stage)
What type of organism is rickettsia?
Gram-negative obligate intracellular parasites
What diseases does rickettsia cause?
Rocky Mountain spotted fever
- Rickettsia ricketsii
Q fever
-Coxiella burnetti
Enedemic typhus
- Rickettsia typhus and rickettersia prowazekki
What is the organism and vector for Rocky Mountain spotted fever?
Tick
Rickettsia ricketsii
What is the organism and vector for Q fever?
Coxiella Brunetti
There is no vector
What is the organism and vector for endemic typhus?
Rickettsia prowazekii - Human body louse
Rickettsia typhi - Flea
How is rickettsia treated?
Tetracyclines
What is the bacteria behind leptospirosis?
Leptospira interrogans
What is the vector for leptospirosis?
Infective rat urine
People get it in:
- Sewage worker
- Farmers
- Vets
- Abbatoir workers
What is Weil’s disease? What causes it?
Leptospirosis
Always consider in hepatorenal failure
Early phase is due to bacteraemia and lasts around a week:
-Mild or subclinical
- Fever
- Flu-like symptoms
- Subconjunctival suffusion (redness)/haemorrhage
Second immune phase may lead to more severe disease (Weil’s disease):
- Acute kidney injury (seen in 50% of patients)
- Hepatitis: jaundice, hepatomegaly
- Aseptic meningitis
How should leptospirosis be investigated?
Serology: antibodies to Leptospira develop after about 7 days
PCR
Culture
What is treatment for leptospirosis?
high-dose benzylpenicillin or doxycycline
What is the presentation of rickettsia typhus? ricketsii? and conorii?
Typhus: Black eschar at site of original inoculation
rash e.g. maculopapular or vasculitis
complications: deranged clotting, renal failure, DIC
Rickettsia: macular rash or hands and feet then spreads
Conorii: rash initially in axilla then spreads
What is the causative organism in cat scratch disease?
Gram negative rod Bartonella henselae
What are the features of cat scratch disease?
Features
fever
history of a cat scratch
regional lymphadenopathy
headache, malaise
What are the features of Q fever?
typically prodrome: fever, malaise
causes pyrexia of unknown origin
transaminitis
atypical pneumonia
endocarditis (culture-negative)
Treatment for Q fever?
Doxycycline
What are the features of brucella?
non-specific: fever, malaise
hepatosplenomegaly
sacroiliitis: spinal tenderness may be seen
complications: osteomyelitis, infective endocarditis, meningoencephalitis, orchitis
leukopenia often seen
Wet hay smell of sweat
What is the treatment of brucella?
Doxycycline and streptomycin
What stain is used on bartonella?
Warthin-Starry staining
Most common bacteria from animal bites?
Pasteurella multocida.
How best to treat animal bites?
- Metronidazole
If allergic:
Doxycycline + metrondiazole
How are human bites treated?
Co-amoxiclav
What are the features of cutaneous leishmaniasis?
Crusted lesion at site of bite
May be underlying ulcer
What cause cutaneous leishmaniasis?
Leishmania tropica
Leishmania mexicana
What is the difference between South or Central American cutaneous leishmaniasis and Africa /Indian cutaneous leishmaniasis?
South / Central America required treatment due to risk of mucocutaneous Leishmaniasis
What causes mucocutaneous leishmaniasis?
Leishmania braziliensis
What causes visceral leishmaniasis?
Leishmania donovani
What causes visceral leishmaniasis?
fever, sweats, rigors
massive splenomegaly. hepatomegaly
poor appetite*, weight loss
grey skin - ‘kala-azar’ means black sickness
pancytopaenia secondary to hypersplenism
How should visceral leishmaniasis be diagnosed?
Bone marrow aspirate
or
Splenic biopsy
What bacteria are found in human bites?
Streptococci spp.
Staphylococcus aureus
Eikenella
Fusobacterium
Prevotella
Risk of Hep C and HIV should be considered
How is brucella diagnosed? How is it stained?
Brucella serology
Rose Bengal plate test can be used for screening but other tests are required to confirm the diagnosis
What are the features of blackwater fever?
Large intravascular haemolysis resulting in haemoglobinuria
Anaemia
Jaundice
Acute kidney injury.
Urine is classically black or dark red in colour
What are the most common non falciparum malarias?
Plasmodium vivax - Central America / India
Plasmodium ovale - Africa
Plasmodium malariae
What are the features of Plasmodium vivax/ovale?
Cyclical fever every 48 hours
+ General malaria features:
- Fever
- Splenomegally
- Headache
What are the features of Plasmodium malariae?
General malaria features:
- Fever
- Splenomegally
- Headache
Nephrotic syndrome
What is treatment for non-falciparum Marla?
WHO recommend either an artemisinin-based combination therapy (ACT) or chloroquine
In areas which are known to be chloroquine-resistant an ACT should be used
ACTs should be avoided in pregnant women
patients with ovale or vivax malaria should be given
Primaquine following acute treatment with chloroquine to destroy liver hypnozoites and prevent relapse
How can toxoplasmosis present in immunocompetent individuals?
Acute toxoplasmosis in the immunocompetent patient can mimic acute EBV infection (low-grade fever, generalised lymphadenopathy with prominent cervical lymph nodes and malaise) and should be suspected with negative EBV serology. Pregnancy testing and counselling is paramount due to the risk of congenital toxoplasmosis
Look at malaria prophylaxis table
Looks at malaria prophylaxis takle
What infection do you get from rabbits?
Tularaemia is a zoonotic infection involving the microorganism F. tularensis
produces an erythematous papulo-ulcerative lesion at the site of the bite with reactive and ulcerating regional lymphadenopathy.
How do you treat F. tularensis ?
Doxycycline
Why is Plasmodium knowlesi difficult to treat?
P. knowlesi has the shortest erythrocytic replication cycle, leading to high parasite counts in short periods of time
