Microbiology Hot topics from the tropics Flashcards
Parasites infecting man can be subdividided as follows:
o Single cell parasites – Protozoa e.g. malaria, giardia
o Multicellular parasites – Metazoa e.g. helminths
o Ectoparasites e.g. fleas and lice
Malaria: A disease caused by
The malaria parasite – a protozoan
Malaria: Incidence
> 300 million people infected with malaria per year
Malaria: Mortality
> 1 million deaths from malaria per year – mainly affects children <5 years of age
Malaria: Geographical locations
equator
Malaria: Human forms of Malaria
There are 4 types of malaria that affect humans:
• Plasmodium vivax
• Plasmodium falciparum – severe malaria (cerebral/anaemia etc)
• Plasmodium ovale
• Plasmodium malariae
Malaria: Onset
7-30 days after mosquito bite depending on the species (pre-patent period (life cycle takes awhile)
Malaria: P. vivax incubation
May rarely take up to 1 year
Malaria: P.vovax and P.ovale can also exist
As dormant forms (hyponozoites) that produce relapses months or years later
Malaria: Life cycle (see more)
- Mosquito bites host (female for eggs to mature)
- Injects anticoagulant to prevent blood clotting + saliva (and if she is
- Sporozoytes (15-20 min) travel to liver
- Undergo life cycle (1 week) – infect RBC (multiplied by binary fission)
- Once RBC infected = brittle/ less malleable in capillaries + surface changes causing sticking to blood vessels.
- Burse and release exponential increase in infected RBC’s
Malaria: Presenting Features/ Complication of Malaria
Flu-like symptoms Respiratory symptoms GI symptoms CNS symptoms Other
Malaria:Flu-like symptoms
Fever Rigors Sweats Malaise Myalgia
Malaria: Respiratory symptoms
Cough
Respiratory distress
Pulmonary oedema
Malaria: GI symptoms
Nausea Vomiting Diarrhoea Jaundice Liver failure
Malaria:CNS symptoms
Headaches
Confusion
Coma – cerebral malaria
Malaria: Other
Shock Acidosis Renal impairment “Blackwater fever” Anaemia DIC Hypoglycaemia Splenic rupture
Malaria: Management of Malaria
- Antimalarials e.g. quinine*, doxycycline, fansidar, primaquine (See BNF, HTD)
- Supportive therapy – correct shock, anaemia, bleeding abnormality, treat or prevent convulsions, hypoglycaemia, (incurrent infections)
- Avoid over hydration
- Consider exchange transfusions
Malaria: Methods of preventing Malaria
Protection against bites • Bed nets • Insect repellants • Clothing to avoid bites at dusk and dawn • Screens on doors and windowns Protection against infections • Prophylaxis • Future role of immunisation Prevent parasite life cycle: • Prompt effective treatment in endemic areas • Local measure e.g. pesticides, avoid pooling of water Potential role for Altruistic vaccine
Investigations
• If you suspect VHF, do a malaria film only • Thick and thin malaria films → Thick – looking at structure of RBC’s • Malaria antigen test • FBC – decreased platelets • Clotting screen • U and Es, LFTs • Blood cultures • Serology – e.g. dengue fever • pH • Lactate
Results
WCC – depressed in malaria
Clotting screen – disseminated vascular
Blood cultures – intercurrent infections
Serology – other
Viral Haemorrhagic Fevers → Types
Lassa
Marburg
Ebola
CCHf
Viral Haemorrhagic Fevers → Risk Factors
- Travel to high risk area in the last 21 days
- Contact with human or animal with suspected VHF (body fluids/tissues)
- Injestion of bush meat
Viral Haemorrhagic Fevers → Description
Febrile disease caused in a variety of ways
Leishmaniasis
Several types of leishmaniasis broadly categorised info:
Visceral leishmaniasis
Cutaneous leishmaniasis
Visceral leishmaniasis is characterised by
Hepatosplenomegaly
Cutaneous leishmaniasis
Tropical sores
Transmission
Sandflies
Diagnosis
Biopsy
Treatment
Antimonials
Pentamidine
Amphotericin
Prevention
Impregnanted bed nets
Elimination of animal vector e.g. dog control
Description (2 types)
Sleeping sickness (Africa) Chagas disease (S. America)
Transmission of Sleeping sickness
Tsetse fly transmit from wild animals to man
Chagas disease transmission causes
Rejuvid blood transmits to man causing (if it gets to this stage its irreversible):
- megaoesophagus
- Megacolon
- Cardiomyopathy
Treatment
Arsenicals
Transmission of helminths:
ingestion
Inoculation
ingestion
- Of eggs ir larvae from the faeces of an infected host e.g. threadworm
- Of soil or food contaminared by soil in which larvae have developed from eggs passed in the faeces have developed from eggs passed in the faeces of an infected host e.g. ascaris
- Ingestino of larvae in the tissue of an intermediate host e.g. taenia so.
Inoculation
- By a blood sucking insect e..g. filariasis
* By active penetrationof the larvae e.g. schistosomias, hookworls
Schistosomiasis (bilharzia) Description
A trematode that infects man
Schistosomiasis (bilharzia) 3 forms
S. haematobium – bladder (haematuria)
S, mansonii (blood vessels around gut eggs released in faeces
S. japonisum
Schistosomiasis (bilharzia) Presentation
- None- “swam in lake malawi”
- “swimmer’s itch”
- “katayama fever” – a seroconversion illness characterised by fever, arthralgia, uticarial rash, death
- Haematuria
- Portal hypertension e.g. haematemesis
- Malignancy
- Paraparesis
Schistosomiasis (bilharzia)Diagnosis
- Ova in urine, stool or biopsy
- Immunodiagnosis
- Eosinophila
Schistosomiasis (bilharzia) Treatment
Praziquantel
