Week 1 Lecture 2 - Microorganisms that may be Encountered in Haematological Assessment Flashcards
Babesiosis
Several species reported to cause disease
- Babesia microti
- Babesia bovis
- Babesia divergens
Life cycle
- tick borne transmission
- commonly animal reservoir of disease
Uncommon in Australia
Babesia infection may present as a spectrum of clinical signs:
- asymptomatic
- mild influenza like symptoms
- fever, chills, fatigue
- haemolytic anaemia
Babesiosis - Clinical Features on FBP
Anaemia
Thrombocytopenia
Intra-erythrocytic organisms
Extracellular organism (rare)
Neutrophilia
Atypical/reactive lymphocytosis
Babesia microti
Microscopy
- sequential thick & thin blood films
- small piroplasms
- similar morphology to P. falciparum ring form trophozoite
- 1, 2 or 4 organisms per RBC
PCR & DNA sequencing
African trypanosomiasis (Sleeping Sickness)
African trypanosomiasis is caused by infections with:
- Trypanosoma brucei gambiense (West Africa and western Central Africa) (>98% of cases)
- Trypanosoma brucei rhodesiense (East, Central and Southern Africa)
Transmitted by tsetse fly (Glossina spp)
Clinical syndrome:
- first stage, the trypanosomes multiply in subcutaneous tissues, blood and lymph causing bouts of fever, headaches, joint pains and itching
- second stage the parasites cross the blood-brain barrier to infect the central nervous system resulting in changes of behaviour, confusion, sensory disturbances and poor coordination
American trypanosomiasis (Chagas’ disease)
American trypanosomiasis is casued by infection with:
- Trypanosoma cruzi
Transmitted by the Reduviidae bug
T. cruzi can also be transmitted by:
- consumption of food contaminated with triatomine bug faeces
- blood transfusion from infected donors
- passage from an infected mother to her newborn during pregnancy or childbirth
- organ transplants using organs from infected donors
- laboratory accidents
Found in tropical and subtropical South and Central American countries
American trypanosomiasis - Clinical Signs
Chagas’ disease presents itself in 2 phases.
1. Acute phase
- lasts for about 2 months after infection
- high number of parasites circulate in the blood
- most cases patients are asymptomatic
2. Chronic phase
- ~30% of patients suffer from cardiac disorders
- ~10% suffer from digestive (typically enlargement of the oesophagus or colon), neurological or mixed alterations
Trypanosomiasis Diagnosis
Thick & Thin Blood Films
- examination of a thick film allows more of the sample to be examined rapidly, but T. cruzi are easily damaged by the spreading of specimens for thick films
- thin blood films allow greater visualisation of cell morphology
- T. b. gambiense and T. b. rhodesiense cannot be distinguished from each other
- T. cruzi measures 12–30µm and has a larger kinetoplast than T. b. gambiense and T. b. rhodesiense.
Bacteraemia
Wide range of bacteria possible
- pathogens, opportunistic
May result from differing transmission circumstances
- systemic spread of (previously) localised infections
- vector transmission
May visualise on blood films
Bacteria Specifically Infecting Leukocytes
Anaplasma phagocytophilum
Ehrlichia chaffeensis
Ehrlichia ewingii
Undetermined ehrlichiosis/anaplasmosis
Anaplasmosis
Caused by Anaplasma phagocytophilum
Signs and symptoms of anaplasmosis typically begin within 1–2 weeks after the bite of an infected tick
- Amblyomma and Ixodes spp
Early signs and symptoms (days 1-5):
- fever, chills
- severe headache
- muscle aches
- nausea, vomiting, diarrhea, loss of appetite
Signs and symptoms of severe (late stage):
- respiratory failure
- bleeding problems
- organ failure
- death
Anaplasmosis - FBP and BM
FBP:
- lymphopenia
- thrombocytopenia
- inclusions within granulocytes
- morula(e) = aggregates of organisms
BM:
- myeloid hyperplasia
- megakaryocytic hyperplasia
- reactive histiocytosis, lymphohistocytic aggregates, granulomas
Erhlichia chaffeensis - FBP and BM
FBP:
- lymphopenia
- thrombocytopenia
- atypical lymphocytes
- inclusions within neutrophils, monocytes (lymphocytes) are indistinguishable from A. phagocytophilum
BM:
- myeloid hyperplasia
- megakaryocytic hyperplasia
- reactive histiocytosis, lymphohistocytic aggregates, granulomas
- (myeloid, trilineage hypoplasia)
- SAME AS ANAPLASMOSIS
Erhlichiosis - Early and Late Symptoms
Early signs and symptoms (the first 5 days of illness):
- fever, chills
- severe headache
- muscle aches
- nausea, vomiting, diarrhea, loss of appetite
- confusion
- rash
Signs and symptoms of severe (late stage):
- damage to the brain (meningoencephalitis)
- respiratory failure
- uncontrolled bleeding
- organ failure
- death
Spirochaete Bacteria
Borrelia burgdorferi
- Lyme disease
Borrelia hermsii
- Relapsing fever
Borrelia recurrentis
- louse-borne relapsing fever
Lyme Disease
Wildlife reservoir of bacteria
Transmitted via ticks
Clinical signs:
- relapsing fever, headaches, myalgia, arthralgia, chronic fatigue
PB:
- normocytic anaemia
- thrombocytopenia
- leukocytosis
- spirochaetes (most likely to be present during febrile episodes)
BM:
- lymphoid hyperplasia
- epithelioid granulomas
Fungaemia
Fungal infections may cause systemic disease especially in
infants and immunocompromised patients
PB:
- intracellular organisms (neutrophils, monocytes)
- extracellular ‘free’ organisms
E.g.:
- Candida species
- Cryptococcus neoformans
- Histoplasma capsulatum
Nematode Larvae
The larval stages of filaroid nematodes may be observed in the peripheral blood
These include:
- Wuchereria bancrofti
- Brugia malayi
- Brugia timori
- Loa loa
- Mansonella perstans
- Mansonella ozzardi
Transmitted by:
- infected mosquito (W. bancrofti, B. malayi, B. timori)
- infected (Chrysops) fly (L.loa)
