MODULE 1 Unit 4: Laboratory Diagnosis of Parasitic Infections Flashcards
There are two (2) approaches in the diagnosis of parasitic infections: clinical and laboratory.
- Clinical Diagnosis
- Laboratory Diagnosis
The clinical manifestations of parasitic diseases are so (?) that in most instances diagnosis based on symptomatology alone is inadequate. .
non-specific
Although, an experienced physician may recognized characteristic signs and symptoms of certain parasitic diseases, the symptoms in (?) may be so confusing that no clear clinical picture is presented. This provides provisional diagnosis only
atypical cases
Physician also suspects that the person has an infection rather than another type of illness based on patient
clinical history.
It is designed to discover epidemiologic risk factors such as, but not limited to
past medical history, place of residence, travel, occupation, outdoor activities, family, food, and drinking water
Specific examples of the importance of each of these follow.
• (?) should be suspected in a patient with unexplained fever and with the history of travel to rural area in Palawan.
• A history of hiking and drinking stream water is classically associated with (?).
• A gastrointestinal disease characterized by abdominal pain and diarrhea that follows after eating uncooked freshwater or brackish water fish may be associated with (?)
Malaria
giardiasis
Capillaria philippinensis infection
A parasitology laboratory uses appropriate test method to be able to:
• Confirm or rule out a (?) that the disease is parasitic in nature.
• Identify (?( infection
clinical suspicion
unsuspected
To confirm means to state that the disease is due to (?), and what species of parasite is present.
To rule out means to (?) as the cause of the disease.
parasitic infection
exclude or to eliminate parasite
Unrecognizedorsubclinicalinfectionsposeathreatbecause manyparasitescanbetransmittedwhensymptomsare either
mildortotallyabsent.
Accurate diagnosis of a parasitic disease provide (?) thus preventing possible complications that may arise. It can also provide accurate (?) that are important in the surveillance and monitoring of diseases.
prompt treatment
prevalence and incidence
Laboratory diagnosis of parasitic infections is done either by
direct or indirect methods
involves the demonstration of the parasite (e.g., adults, eggs, larvae, cysts, or trophozoites), or parasite components (e.g., antigens and DNA) in the specimen. This provides definitive diagnosis of parasitic infection.
Direct method
tests for the evidence of parasitic infection other than actually finding the organism itself. This provides only presumptive evidence of infection.
Indirect method
Parasitic infections are usually diagnosed by examination of a specimen/ material under the microscope.
Microscopic method
Microscopic method is basically a two-step process:
(1) detection of the (?), and
(2) identification based on
parasite
distinctive morphologic characteristics
Among others factors, this requires the availability of (?) and a well-trained and experienced (?).
good microscope
microscopist
The need for highly invasive procedures to collect samples g. tissue, which may induce medical complications, undermines the utility of this method.
Microscopic method
The most common procedure performed in the area of parasitology is the examination of a stool specimen for
ova and parasites (O&P exam)
refers to the egg stage of select parasites and parasites encompass the other morphologic forms that may be present
ova
Appropriate specimen is examined microscopically by (?) for parasite diagnostic stage
direct wet mounts, wet mounts of concentrates, or permanent stains
- Cysts/trophozoites of (?)
-Oocysts of (?)
-Eggs of (?) - Rhabditiform larvae of
Entamoeba histolytica, Giardia lamblia, Balantidium coli
Cystoisospora belli, Cryptosporidium parvum, Cyclospora cayetanensis, Sarcocystis spp.
Ascaris lumbricoides, Trichuris trichiura, hookworm spp. Capillaria philippinensis, Diphyllobothrium latum, Taenia spp., Hymenolepis nana, Hymenolepis diminuta, Dipylidium caninum, Fasciola spp, Clonorchis sinensis, Opisthorchis spp, Fasciolopsis buski, Echinostoma ilocanum, heterophyids, Schistosoma japonicum, Schistosoma mansoni
Strongyloides stercoralis
Being generally a (?), this remains as the gold standard in most laboratories especially in the diagnosis of common protozoan and helminth infections. However, it is characterized by low sensitivity when parasites are low in numbers such as in light infections ,or during pre-patent and chronic periods of infection, hence, direct microscopic examination may yield false negative results. Concentration technique circumvents this problem
simple and low cost technique
Giardia lamblia trophozoites, Cryptosporidium spp., Cystoisospora belli, Strongyloides stercoralis and eggs of Fasciola hepatica or Clonorchis sinensis
Duodenal material
Entamoeba histolytica
Sigmoidoscopy specimen
Enterobius vermicularis
Perianal swab
Plasmodium spp., Babesia spp., Leishmania spp., Trypanosoma spp. Wuchereria bancrofti, Brugia malayi, Loa loa, Mansonella spp.
Blood
Trichomonas vaginalis, Wuchereria bancrofti, Schistosoma haematobium.
Urine
- Paragonimus westermani
- Occasionally, larvae of Strongyloides stercoralis, Ascaris lumbricoides, and hookworm spp.
Sputum
Trypanosoma brucei, Naegleria, Acanthamoeba
Cerebrospinal fluid
Trichomonas vaginalis
Genital tract specimen
Muscle biopsy specimen: Trichinella spiralis
Tissue and aspirates
Histopathological examination of brain: Naegleria and Acanthamoeba
Tissue and aspirates
Spleen and bone marrow aspirate: Leishmania donovani
Tissue and aspirates
Duodenal aspirates: Trophozoites of Giardia lamblia
Tissue and aspirates
Liver pus: Trophozoites of Entamoeba histolytica in cases of amebic liver abscess
Tissue and aspirates
Culture methods using xenic or axenic media have been described for some protozoan parasites:
Trichomonas vaginalis, Leishmania spp., Trypanosoma cruzi, Entamoeba histolytica, Acanthamoeba spp., or Naegleria fowleri.
is examined microscopically. This approach may be helpful when routine procedures have failed to provide a diagnosis.
Material from culture
But few clinical laboratories undertake the task because of :
infrequent requests, lack of familiarity with methods, the need for special equipment, supplies, and reagents, and the waiting period for several days or weeks for the result.
Culture protozoa grown in association with an unknown microbiota are called a (?).
xenic culture
If they are grown in association with a single known bacterium, the culture is (?)
monoxenic
if the culture contains several identified bacteria, then it is (?).
polyxenic
If protozoa are grown as pure culture without any bacterial associate, the culture is (?).
axenic
(?) is used for maintaining QC strains and for research purposes.
Axenic culture