L33 Typhoid, Malaria, Travellers disease Flashcards
Give an example of Infections and the new route of infection exposed to overseas
- Contaminated air: TB/influenza
- Contaminated water/food: salmonella typhi, enteritidis, Campylobacter jejuni, Hep A
- Infected vectors (mosquitos): Malaria, dengue
- Infected people: HIV, Syphilis
What are the 3 types of mosquitos and what diseases do they carry. Where are they found
- Females drink blood meal for egg development.
- Culex: only one in NZ
- Anopheles: forest dwelling, night feeding : Malaria. found in PNG, Solomons, Vanuatu. (India, central Africa)
- Aedes: Urban dwelling, day feeding: dengue, Zika, yellow fever.
Describe the steps in the lifecycle of the malaria parasites - Plasmodium falciparum/vivax
- Infected female anopheles feeds on blood and injects saliva containing sporozoites
first 10 days
2. Sporozoites invade liver cells and replicate: No significant LFT damage/symptoms
- Sporozoites mature to Merozoites -> burst from liver cells and invade RBCs. Falciparum all leave, but vivax keeps some behind for mo/yrs
- Merozoites replicate in RBCs and rupture them, causing persistent Fever, Shiver, Sweat.
- Some Merozoites mature into male and female gametocytes which mate in the gut of mosquito when it has taken blood from a human and stores the young plasmodians in the anopheles salivary glands again.
What is the presentation and diagnosis of Malaria
- Presents as Fevers, Rigors, Malaise, headache and coma after returning from residence in a malarious area.
- Blood film examination for infected RBCS (usually 1% is a lot) and antigen detected in blood.
Compare the complications of infection with Plasmodium Falciparum and P. vivax : which RBCs infected, parasite load, Severe disease pathology
Falciparum
- infects any RBC
- high parasite load >1% RBCs infected
- Causes sequestration of RBCs in capillaries due to inserting a protein into RBC membrane that adheres to endothelial cells.
- Leads to Death from Coma (diffuse shortness of nutrients) and Renal failure (ischaemia +blood leaking in urine to look black)
Vivax
- only infects young RBC
- low parasite load <1%
- no sequestration/ risk of severe disease but can get relapses from repeated release of liver hypnozoites mo/yrs after
What is the treatment / prevention for Plasmodium Falciparum and P. vivax :
Treatment
Falciparum: kill the merozoites in RBC using Quinine + doxycycline // artemether + lumefantrine (if resistant)
and P. vivax : kill the merozoites with chloroquine. Then kill hypnozoites with primaquine
Prevention
Avoidance of malarious areas,
Mosquito control: long clothes, bed nets, insect repellent.
Prophylactic doxycycline, mefloquine to kill any malaria deposited into the blood
What is Dengue fever: what does it infect, incubation/ recovery time, presentation and treatment
Dengue Virus (RNA) transmitted by Aedes mosquitoes which infects macrophages
- Incubation is 2-7 days
- Presents with fever, malaise, headache, aching muscles, bone pain. Dengue virus antigens in blood
- Recover in 1 wk.
No effective treatment - vax under development
Compare the two types of Salmonella - where are they acquired, where does it infect, what type of disease caused
Salmonella Enteritidis:
- acquired from animals and birds
- infects colonic mucosa (some destroyed by Peyers patch
- Causes colitis : recovery w/out antibiotics
- common cause of GE in NZ and overseas
Salmonella Typhi = Typhoid/enteric fever
- acquired from people faeces
- infects macrophages in Peyers patches in terminal ileum
- causes necrotic/oedematous PP: then bacteraemia and septicaemia.
- common cause of persistent fever in travellers
Death from
- Perforation of peyers patch resulting in peritonitis
- Erosion of ileal blood vessels resulting in catastrophic intestinal bleeding
Compare the presentation of Sal. Enteritidis and Sal. Typhi.
Which one has a persistent colonisation and where
How is Typhoid fever treated
1.Enteriditis: pain, blood diarrhoea, recovery w/out antibiotics
Typhi: fever, rigors, sweat, cough, headache, confusion- NO DIARRHOEA
- Minority of infected people have Typhi has persistent colonisation in the gall bladder and excrete typhi in the faces as a source of infection for others.
- Confirmed with blood cultures (2-3 days, may require several to isolate typhi) and treated with Ceftriaxone IV or Ciprofloxacin O for 10 days. Then follow up months later to check stool for trace of typhi - seek to eliminate
What is Hepatitis A: epidemiology, pathology, presentation, treatment and test
- RNA virus which only infects humans, widespread in areas of poor sanitation
- Virus ingested infects hepatocytes and is excreted in faeces. Recovery with elimination of infection.
- Jaundice, malaise, anorexia, fever. - No treatment excellent vaccine
- Blood sample for Hep A (HAV) serology: anti-HAV IgM: acute infection, IgG: immunity following previous disease/vaccination
What is Enterotoxigenic E. coli epidemiology, pathology, presentation, treatment
- Travellers diarrhoea. Rare in NZ, common in developing countries
- Produces toxins act on the small bowel
- Abdo cramps, diarrhoea 1-5 days - Antibiotics give minor reductions in incidence and severity.
