Parasitology
Fecal samples should be mailed in plastic bags or other water – tight containers. If the samples reach the laboratory in three days, no preservatives need to be used.
However, some of the ova may hatch during this time unless air is excluded from the container. The recommended method is to place the fecal sample in 10 – 15 volumes of 10% formalin (the same concentration as for submitting histopathology samples) or, if coccidia are suspected, place the feces in 2.5% potassium dichromate solution. If special procedures such as the Baermann technique to find Strongyloides spp. or lungworm larvae are needed, they should be requested. Fresh fecal samples without preservatives or fixatives are required for the Baermann technique.
If examination for intestinal protozoa other than coccidia (particularly Giardia spp. or amoebae) is requested, the sample should be fixed and shipped using sodium acetate – acetic acid – formalin (SAF) fixative. The fixative also preserves helminth eggs. The SAF solution is prepared as follows:
Sodium acetate 1.5 g
Acetic acid, glacial 2.0 ml
Formaldehyde solution (40%) 4.0 ml
Water 92.5 ml
TOTAL 100.0 ml SAF fixative.
Mix one volume of feces with at least three volumes of SAF fixative. Shake container well to ensure complete dispersal of specimen. Vials containing SAF fixative are available from the Parasitology Laboratory. Please call or write to receive pre – loaded specimen vials.
Parasite Specimens:
Gross specimens require fixation and preservation prior to mailing. Trematodes and cestodes that are recovered at necropsy or passed in the feces should be placed in tap water, kept overnight in a refrigerator, and then fixed and stored in 10% formalin. Nematodes should be fixed, preferably in 70% ethanol, but can also be fixed in 10% formalin.
Most nematodes from domestic animals can be easily identified, but if nematodes are from exotic or wild animals, special fixation is needed. The best method is to heat 70% ethanol to about 60 degrees Celsius, drop the parasites into the hot alcohol one by one, and remove them as soon as they are fixed in an extended position. They should then be placed in fresh 70% alcohol for mailing.
Blood specimens for examination for microfilaria (Knott's test) should be fixed in at least 10 volumes of 2% formalin. Serum (1 ml) should be sent for the occult heartworm antigen test.
Ectoparasites should be fixed and submitted in 70% alcohol.
Skin scrapings may be sent on slides if a coverslip is sealed to the slides with clear nail polish or similar material. Be sure there is enough oil under the coverslip so that the material will not dry out in transit. Send more than one slide if possible. In addition, submit a scraping from the same area the parasites were found. Take scrapings from the edges of lesions and try to squeeze the skin while scraping to bring mites to the surface. A good, deep scraping is indicated by the presence of red cells. Submit in 70% alcohol.