Parasitology Diagnostics

Question 1

describe the different techniques used to diagnose parasites (BROADLY)

Answer 1

2 main categories:
1. tests based on visual (morphological) identification of the parasite stage available: using blood, feces, urine, or tissue sections
2. tests that do not: not user dependent, use another modality; including fecal antigen, PCR, serology

can be either qualititative: presence or absence, more common in small animals or
quantitative: observe a count of parasites in a known volume of blood, feces, etc.., more common in ruminants and horses

Question 2

what makes a good sample?

Answer 2

1. fresh!! is best; if not possible the refrigerate or preserve solution in formalin or ethanol!
2. don’t forget about opportunisitc/easy to obtain samples: once take temp in an appointment, just stick the tip of that probe in some saline on a slide and you’ve got a direct fecal mount!; can also use the last drop of blood in a syringe as a direct blood mount for microfilariae
3. the more sample the better and more accurate!!: need at least 1 gram of feces for flotation!!

Question 3

describe use of blood to check for parasites: what parasites can be found, what clinical signs would lead you to check a blood sample, what stain/methods used

Answer 3

1. can evaluate for several parasitic protozoa as well as the first-stage larvae of some tissue-dwelling nematodes; will appear in films of peripheral blood stained commonly using Giemsa stain
2. if see the clinical signs: anemia, fever, lethargy, or known exposure to ectoparasites
3. good for heartworm test, ID microfilaria

Question 4

describe use of feces to check for parasites; what clinical signs would lead you to check a fecal sample, what testing options are available

Answer 4

1. SHOULD BE PART OF MINIMUM DATABASE!!!
2. or check when see diarrhea, weight loss, ill-thrift, and COUGHING
3. can do direct mount, flotation with centrifugation, sedimentation, the Baermann technique, and/or McMasters Fecal egg count

Question 5

list and describe 4 qualitative fecal diagnostics

Answer 5

1. direct fecal mount: need FRESH feces as is looking for motile parasites!!, place sample in a drop of saline on a slide; good for protozoa and larvae (NTK: fresh feces, saline +/- Lugol’s, motility, protozoa and larvae)
2. flotation WITH centrifugation: feces are thoroughly mixed with a flotation solution of a relatively high specific gravity (so heavy guys can float), eggs, cysts, and oocysts will float to surface of fecal suspension; need AT LEAST 1 GRAM of feces!! good for protozoa, nematodes, and cestodes (NTK: at least 1 gram, flotation solution matters, protozoa, nematodes, cestodes)
3. sedimentation: used to recover the very heavy eggs of trematodes, which do not float with standard flotation techniques, mostly in cattle; is very time consuming as you need to let sit, dump, then let sit again, then dump again until you’ve got the lighter stuff off
4. Baermann technique: need fresh feces and at least 12 hours! allow larvae to come out, but they can’t swim against gravity so they’ll fall down and you can examine them in the sediment

Question 6

describe quantitative fecal diagnostics and why you would perform them

Answer 6

1. diution egg counts: more accurate measure when eggs per gram is high; using a known fecal volume, a known flotation media and a known chamber capacity
2. great utility when estimating levels of strongyle infection in ruminants and horses; tells not IF infected, but WHAT LEVEL of infection
3. helps you identify your high shedders/contamination risks, allow selective deworming, and determine treatment efficacy

Question 7

list and describe 3 non-morphological diagnostics

Answer 7

1. antigen: detect parasitic antigens in blood/serum or feces like SNAP tests but need to interpret results carefully (positive just means presence not necessarily infection)
2. serology: like antigen, detection in blood of either parasite antigen or of antibodies produced by the host to parasite antigen
3. PCR: detection of various genetic markers in different parasites; enabled species ID of parasite stages found in feces, blood, or tissues

Question 8

list and describe 3 methods for looking for ectoparasites

Answer 8

1. skin scrape: recovers small guys, esp those species associated with mange
2. swab and slide: ear guys
3. skin and hair coat examination: flea coat, or literally just look at it