blood parasites and heart worm Flashcards
What is a blood parasite?
Pathogenic organism living in or on RBCs and WBCs
What 4 things does the 4DX Test test for?
Heartworm, Lyme, Ehrlichia, anaplasma
The 3DX Test tests for?
Heartworm, lyme, ehrlichia
What is the disadvantage of testing for antibodies rather than antigens?
Antibodies only tells us that the pet was exposed to the disease not that it currently is harboring the disease
Which blood parasite causes Feline Infectious Anemia?
Mycoplasma haemofelis
If looking for blood parasites on a smear, which parts of the smear are more likely to have infected cells?
edges of smear
How are these parasites transmitted?
ticks
Besides anemia, name other symptoms/health issues caused by blood parasites
Lethargy, fever, Thrombocytopenia, lameness
A buffy coat smear is helpful in finding which of the blood parasites?
The WBC parasites Ehrlichia and Anaplasma
Ehrlichia canis
Monocyte-cytoplasm
Rickettsial bacteria-brown dog tick
Ehrlichia ewingii
Neutrophil-cytoplasm
Rickettsial bacteria-ticks
Anaplasma platys
Invades platelets also
Rickettsial bacteria-ticks
Anaplasma phagocytophylum
Neutrophil-cytoplasm
Rickettsial bacteria-ticks
Anaplasma marginale
Edge of RBC
Ticks
Babesia spp
Teardrop or ring- shaped organism found in erythrocyte
ticks
Haemobartonella felis
Round rod or ring shaped bacteria found on RBC
Fleas and ticks
What is the scientific name for the heartworm?
Dirofliaria Immitis
What is the scientific & common name of the larva which may be confused with heartworm larvae?
Acanthocheilonema sp (Dipetalonema)
List symptoms of heartworm a client might notice
Cough, dyspnea, tiring easily after exercise
List 3 things you could see on the differential that may indicate the dog has heartworm
Increased WBC count, Eosinophilia, Basophilia
How long does it take before larvae mature? When can microfilaria be found in a newly infected dog?
70 days; 6 months
List ways heartworm can be diagnosed (6)
Differential smear, direct smear, hematocrit scan, Modified Knott’s test, Difil test, ELISA
Explain why cats are a poor reservoir for heartworm
Not natural host (aberrant host), immune system kills most larvae
A highly sensitive test is prone to false _____ results. A highly specific test is prone to false _____ results
positive; negative
What is a “false positive” result?
Detects antibodies in the system but not current disease
For each type of heartworm test, discuss how sensitive it is and how specific it is (ELISA, concentration tests, crit scan, direct smear)
ELISA - specific detects antigen to adult female heartworm can detect occult infections (no microfilaria)
Concentration tests - specific-look for L 1 larvae in the blood
Crit scan - specific microfilaria
Direct smear - specific microfilaria
Describe how to perform a direct smear for heartworm
- Put 1-2 drops of blood on a slide
- add coverslip
- observe on 10X medium light
Which heartworm tests are “concentration tests”?
Difil, Modified Knott’s test
Name 5 tests for microfilaria
direct smear, differential smear, crit scan, difil, modified knotts
Describe 3 differences that help you distinguish Acanthoheilomea from Dirofilaria
- Size-Acanthoheilomea smaller
- Dirofilaria has a tapered straight tail
- Acanthoheilomea has a curved crooked tail
A cat is tested for microfilaria, but the test is negative. Does this mean the cat doesn’t have heartworm? Explain. Rate the sensitivity and specificity of microfilaria tests for heartworm in the cat
Cats with heartworm disease rarely have microfilaria, Elisa tests detect antigen to adult female heartworm, cats may only have one or two adult heartworms and may not have females. The microfilaria tests are specific therefore are prone to false negatives
The IFA test looks for?
Antibody to heartworm
If the IFA test is positive, does that mean for sure that the animal has heartworm?
No, prone to false positive
ELISA tests for heartworm detect what?
Antigen to adult female heartworm
What is the advantage of ELISA tests for heartworm compared to other types of tests?
Can detect occult infections where no microfilaria are present
Explain what an “occult infection” is. What can cause it?
No microfilaria present, drugs used to prevent heartworm infections kill circulating microfilaria
What can cause a false negative ELISA test?
No adult female heartworms
What is meant by an “aberrant host”?
Not the natural host
