Fecal Materials Specimen Preparation and Submission
Other Specimen Preparation and Submission

Alternate constipation and diarrhea may indicate a worm or protozoan infection. The presence of blood in stool can be a sign of parasite infection, such as hookworm in dogs.

Fresh stools are essential for the recovery of motile trophozoites such as Giardia which are most likely to be found in the order of liquid > soft > formed stools. Liquid and soft stool should be examined or preserved in an appropriate fixative within 1 hour of bowl movement. If fresh specimens remain unpreserved for a longer time before examination, many trophozoites may disintegrate or become destroyed. If immediate fixation is not possible, the specimen may be refrigerated (3oC – 5oC) until the next morning.

Although trophozoites will be killed by refrigeration, cysts and helminth eggs will retain their characteristic morphology. Fecal specimen should never be incubated or frozen prior to examination.

Multiple specimens: Because of the intermittent passage of certain intestinal parasites from the host, examining multiple specimens increases the possibility of finding organisms. In general, nematode species such as Toxocara, hookworm and Trichuris shed eggs more or less constantly and may be detected daily in feces. However, some parasite species such as cysts of Entamoeba histolytica and Giardia, eggs of Schistosomes and Diphillobothrium, and proglottids of Taenia species are passed irregularly. It is well documented that Giardia cysts are passed at intervals ranging from 2 to 3 days to 7 or 8 or more. Although there is no magic number of specimens that should be examined to rule out such infections, it is suggested that at least three stools collected at 2 to 3 day intervals, should be examined. A veterinarian receiving a report of "negative" or "no parasites found" on a single specimen should realize that this does not exclude the possibility of the patient being infected with Giardia.

For requesting O & P (formalin-ethyl acetate sedimentation concentration) test:
Transfer 10 to 20 g of a formed specimen (about the size of a large walnut) or 2 to 3 tablespoons of watery stool into plastic container(s) containing a spatula stick and clear colorless liquid preservative (Sodium acetate-Acetic acid-Formalin - SAF). Mix the feces with the fluid as thoroughly as possible, using the spatula stick, and screw cap tightly on the bottle. The thorough mixing is important to preserve any parasites present in the stool so that they can be detected later in the laboratory. The SAF kit is available from the VITA- TECH Laboratory.

O & P test allows the recovery of all helminth eggs, larvae, and protozoan cysts. In some cases, Hymenolepis nana eggs and Giardia cysts may not concentrate well. Therefore, this method is performed along with a permanent staining procedure, which detects more protozoan cysts and trophozoites. The permanent staining method (Haemoatoxylin staining), however, cannot detect Cryptosporidium oocysts. Therefore, a special staining procedure is used, if Cryptosporidium is suspected.

For requesting Baremann and/or fecal flotation test:
Transfer 10 to 20 g of fresh unpreserved fecal specimen in a clean empty container. It is important that the specimen should be submitted to the laboratory within 24 hours after defecation, NOT after collection.

Flotation method detects certain species of helminth eggs, especially nematode eggs, but is not recommended for the detection of trematode eggs (Schistosomes, liver flukes, lung flukes, intestinal flukes), and eggs of Diphillobothrium and unfertilized Ascaris, because they do not float well and may give false negative results. Giardia cysts may be easily missed because of poor flotation and morphological distortion.

Baremann procedure, generally recognized as the most efficient means of examining stools for nematode larvae, is completely unsuitable for some species of lung worms, such as Filaroides osleri, Filaroides hirthi, because larvae of these species tend not to migrate out of the fecal mass into the surrounding water.

For requesting Giardia and Cryptosporidium antigen test:
Submit 5 to 10 g of fecal specimen in 20 to 30 ml of formalin solution (5% or 10%) or SAF solution. The antigen test can be done on fresh unpreserved stools as well. However, the fresh stools should be transported to the laboratory as soon as possible after collection of the stool. This test, an enzyme immunoassay, detects soluble antigens, which may present in fecal samples.

For requesting post-treatment specimens:
Disappearance of symptoms in a patient with a parasitic infection is not sufficient evidence of a "cure". Post-treatment specimens should be examined to determine the effectiveness of therapy.

With most drugs used to treat patients with protozoan infections, organisms may not be found shortly after therapy even though the infection has not been eradicated. Thus, unless symptoms reappear earlier, the first post-treatment specimen should be collected approximately 4 weeks after therapy.

In helminth infections, post-treatment specimen should be collected 1 to 2 weeks after treatment. Patients who have been treated for tapeworm infections should be checked 2 to 3 months later.

The specimens should be collected in the same manner as for the initial diagnosis.