David Allen Elsemore

Enzyme-linked immunosorbent assay for coproantigen detection of Trichuris vulpis in dogs:

Infections with Trichuris vulpis, the canine whipworm, may be challenging to diagnose even though characteristic bipolar eggs are shed by mature worms and may be recovered from feces. Decreased detection sensitivities because of using flotation solutions with specific gravities <1.3 and a lengthy prepatent period can lessen the diagnostician’s ability to detect infection. Coproantigen detection in feces is becoming an accepted form of diagnosing parasitic infections and can circumvent some of the factors that affect egg recovery. The development of an enzyme-linked immunosorbent assay (ELISA) for the detection of whipworm-specific coproantigens in the feces of dogs with experimental and natural T. vulpis infections is reported herein. Whipworm-specific coproantigens were evidenced in feces from experimentally infected dogs using the newly developed ELISA starting as early as day 23 postinfection, while eggs were not detected in feces until day 69. In addition, 1,156 field fecal samples were tested using fecal flotation methods and the newly developed whipworm ELISA. Of these, 27 samples were found by flotation to be whipworm egg positive, while 35 had detectable antigen on the ELISA. Discrepant results were obtained in 12 samples; 2 egg-positive samples tested ELISA negative, and 10 ELISA-positive samples did not contain detectable egg levels. Using the fecal ELISA for the detection of whipworms in dogs should allow for earlier detection of infection, aid the identification of cases in the face of low egg shedding, and increase detection sensitivity as most commercial laboratories are using flotation solutions not optimal for T. vulpis egg detection.

Enzyme-linked immunosorbent assays for coproantigen detection of Ancylostoma caninum and Toxocara canis in dogs and Toxocara cati in cats

We report the development and field validation of 2 ELISAs for the detection of Ancylostoma caninum or Toxocara canis coproantigens in the feces of dogs with experimental and natural infections, and evidence of cross-reactivity with respective feline counterparts. A. caninum–specific coproantigens were detected in feces of experimentally infected dogs starting at 9 d post-infection (dpi), whereas eggs were not seen until 23 dpi. T. canis–specific coproantigens were detected in 3 of 5 experimentally infected dogs by 31 dpi, and 4 of the 5 animals by 38 dpi. T. canis eggs were seen in feces of 4 of the 5 animals by 38 dpi. One dog had delayed coproantigen detection and low egg output. Additionally, 817 canine and 183 feline fecal samples from naturally infected animals tested by flotation were subjected to coproantigen ELISA testing. Of these 1,000 canine and feline samples, 13 and 23 samples, respectively, were positive for “hookworm” or “roundworm” eggs; 19 and 26 samples were ELISA positive, respectively. The T. canis ELISA detected T. cati coproantigen in cat fecal samples. Discrepant ELISA and flotation results were obtained for 16 hookworm- and 13 roundworm-positive samples. Re-examination of the egg-positive, ELISA-negative samples indicated several instances of possible misidentification or coprophagy, whereas detection of antigen in samples without egg observations is likely a reflection of true infection status with egg shedding below detection levels. There is good indication, based on accumulated field data, that these antigen tests also detect other hookworm and ascarid species.

Diagnostic strategies to reveal covert infections with intestinal helminths in dogs

Intestinal helminths are common in dogs in the United States, particularly non-treated dogs in animal shelters, but surveys by fecal flotation may underestimate their prevalence. To determine the prevalence of intestinal helminths and evaluate the ability of fecal flotation and detection of nematode antigen to identify those infections, contents of the entire gastrointestinal tract of 97 adult (>1year) dogs previously identified for humane euthanasia at two animal control shelters in northeastern Oklahoma, USA, were screened. All helminths recovered were washed in saline and fixed prior to enumeration and identification to genus and species. Fecal samples from each dog were examined by passive sodium nitrate (SG 1.33) and centrifugal sugar solution (SG 1.25) flotation. Fecal antigen detection assays were used to confirm the presence of nematode antigen in frozen fecal samples from 92 dogs. Necropsy examination revealed Ancylostoma caninum in 45/97 (46.4%), Toxocara canis in 11/97 (11.3%), Trichuris vulpis in 38/97 (39.2%), Dipylidium caninum in 48/97 (49.5%), and Taenia sp. in 7/97 (7.2%) dogs. Passive fecal flotation identified 38/45 (84.4%) A. caninum, 6/11 (54.5%) T. canis, 26/38 (68.4%) T. vulpis, 2/48 (4.2%) D. caninum, and 1/7 (14.3%) Taenia sp. infections, while centrifugal flotation combined with antigen detection assays identified A. caninum in 97.7% (43/44), T. canis in 77.8% (7/9), and T. vulpis in 83.3% (30/36) of infected dogs based on necropsy recovery of nematodes. Taken together, these data indicate that detection of nematode antigen is a useful adjunct to microscopic examination of fecal samples for parasite eggs, and that this approach can improve diagnostic sensitivity for intestinal nematode infections in dogs.