2: Detection of Protozoan and Helminth Parasites in the Urinary, Reproductive, and Integumentary Systems and in the Eye

Detection of Protozoan and Helminth Parasites in the Urinary, Reproductive, and Integumentary Systems and in the Eye


Parasites of the Urinary System

Several organisms parasitize the urinary tract, and their eggs and cysts can be detected by routine urine sedimentation. Samples collected by cystocentesis are preferred because voided urine samples could be contaminated with fecal material containing parasite eggs or larvae from the intestinal or respiratory systems.

Urine Sedimentation

  1. Centrifuge 5–10 mL of urine in a conical‐tip centrifuge tube for 5 minutes at 1500–2000 rpm (approximately 100 × g).
  2. Decant the supernatant fluid, leaving 0.5 mL. Resuspend the sediment.
  3. Transfer a drop of sediment to a slide, add a coverslip, and examine.

Parasites of the Reproductive Tract

Organisms that are primary parasites of the reproductive tract are not important pathogens of common domestic species in North America, with the exception of Tritrichomonas foetus. In South America, West Asia, and parts of Africa, Trypanosoma equiperdum causes serious disease in horses and is transmitted venereally. However, this parasite is difficult to recover from tissue fluids or blood, and immunodiagnostic tests are usually used for confirmation of infection. Several other parasites can affect reproduction as a part of general systematic effects, including Neospora, Toxoplasma, and Sarcocystis. These parasites also would not be recovered and identified in the live animal.

Tritrichomonas foetus is a parasite of cattle found in the uterus and vagina of cows and the prepuce of bulls. Diagnosis of infection is usually by detection of the organism in preputial samples from bulls, although vaginal or cervical secretions from cows can also be tested. A number of U.S. states require testing of bulls for T. foetus before interstate movement. A commercial kit is available that provides a plastic pouch containing a medium into which the sample can be inoculated either for culture and microscope examination or for use as a transport medium when the sample is submitted for PCR. (InPouch® TF, Biomed Diagnostics, Inc., White City, OR, www.biomeddiagnostics.com/).

Bovine Preputial Sample Collection

  1. Attach a dry 21‐in. infusion pipette to a 20‐cc syringe and insert into the prepuce of the bull. The tip of the pipette is scraped back and forth across the epithelium while suction is applied.
  2. Examine the collected sample microscopically immediately if desired and then inoculate into Ringer’s solution (or the commercial InPouch®) and refrigerate for transport to the laboratory for culture.
  3. Samples not placed directly into nutritive medium should not be held for more than 48 hours in Ringer’s or other balanced salt solution.

Helminth Parasites of the Integumentary System

Several filarial nematode parasites produce microfilariae that are found in the subcutaneous tissue. These larvae can be detected in fresh skin biopsies or on examination of fixed and stained biopsy tissue sections. For recovery of microfilariae from fresh biopsies, the biopsy is macerated and allowed to incubate in saline for several hours at room temperature. Following incubation, the saline is examined microscopically for the presence of microfilariae. Free‐living nematodes that occasionally invade the skin may also be seen in fresh or fixed and stained skin biopsies.

Parasite Detection in Urinary and Other Systems

Urinary System Parasites

PARASITE: Dioctophyme renale (Fig. 2.1)

Common name:Giant kidney worm.

Taxonomy: Nematode (order Enoplida).

Geographic Distribution: North America and Europe.

Location in Host: Kidney and occasionally peritoneal cavity of dogs, mink, and other domestic and wild animals.

Life Cycle: Adult worms in the kidney produce eggs that are passed in the urine. The first intermediate host is an annelid worm; the second intermediate host is a fish. The final host becomes infected when it eats a fish containing infective parasite larvae.

Laboratory Diagnosis: Eggs with a thick, rough shell are detected in the urine.

Size:60–80 × 39–46 μm

Clinical Importance: The spectacular adult worms (females may reach 100 cm in length) enter the renal pelvis and eventually destroy the kidney, leaving only the capsule. Typically, only one kidney (usually the right) is affected. Most infections are asymptomatic, despite the loss of a kidney, although hematuria and dysuria may occur. Dioctophyme renale is a rare finding in dogs in North America.

Photo depicts Dioctophyme eggs which are larger than those of Pearsonema and have a thicker eggshell with a rougher surface.

Fig. 2.1 Dioctophyme eggs are larger than those of Pearsonema and have a thicker eggshell with a rougher surface.

PARASITE: Pearsonema (= Capillaria) plica, P. feliscati (Figs. 2.2 and 2.3)

Taxonomy: Nematode (order Enoplida). These parasites were previously included in the genus Capillaria.

Geographic Distribution: Worldwide.

Location in Host: Adult worms in the bladder of dogs and foxes (P. plica) and cats (P. feliscati).

Life Cycle: Parasite eggs passed in the urine become infective in the environment. Although the life cycle is not known with certainty, the final host is probably infected by ingesting an earthworm intermediate host or a transport host, such as a bird.

Laboratory Diagnosis: Typical capillarid eggs are detected in urine sediment. Cystocentesis is preferred for collecting urine samples since fecal material containing similar eggs of other capillarid species may contaminate voided urine samples.

Size:51–65 × 24–32 μm

Clinical Importance: Many infections are asymptomatic, although infected animals may develop cystitis.

PARASITE: Stephanurus dentatus (Fig. 2.4)

Common name:Kidney worm.

Taxonomy: Nematode (order Strongylida).

Geographic Distribution: Tropical and subtropical regions.

Location in Host: Adults are found in the wall of the ureters and the pelvis of the kidney as well as in the peritoneal fat of swine.

Life Cycle: Parasite eggs leave the host via the urine. First‐stage larvae hatch from the eggs and develop to the infective third stage. The pig final host is infected by ingestion of infective larvae or an earthworm transport host or by skin penetration by infective larvae. Once in the host, larvae migrate through the liver before moving to the perirenal tissues, where development is completed.

Laboratory Diagnosis: Diagnosis is made by detection of eggs from urine sedimentation tests or from clinical signs. Disease may be present before the infection is patent (prepatent period is 4–6 months).

Size:90–114 × 53–65 μm

Clinical Importance: Damage associated with larval migration through the liver is an important component of disease caused by the parasite. Pigs may show reduced growth or weight loss and general loss of condition. Stephanurus dentatus is unlikely to occur in modern swine confinement systems.

Photo depicts Pearsonema feliscati egg in a urine sedimentation procedure. Methylene blue stain is often added to these preparations, which will stain the eggs purple.

Fig. 2.2 Pearsonema feliscati egg in urine sediment. Methylene blue stain is often added to these preparations, which will stain the eggs purple. Like other capillarids, P. feliscati eggs are elongated and bipolar plugged.

Photo depicts that if the microscope is focused on the shell wall of the Pearsonema egg, a thick globular pattern of ridges can be seen.

Fig. 2.3

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Sep 19, 2022 | Posted by in GENERAL | Comments Off on 2: Detection of Protozoan and Helminth Parasites in the Urinary, Reproductive, and Integumentary Systems and in the Eye

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